The crypto_shash API is used in order to compute packet signatures. The API comes with several unfortunate limitations:

1) Allocating a crypto_shash can sleep and must be done in user context. 2) Packet signatures must be computed in softirq context 3) Packet signatures use dynamic "traffic keys" which require exclusive access to crypto_shash for crypto_setkey.

The solution is to allocate one crypto_shash for each possible cpu for each algorithm at setsockopt time. The per-cpu tfm is then borrowed from softirq context, signatures are computed and the tfm is returned.

The pool for each algorithm is allocated on first use.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/net/tcp_authopt.h | 16 +++ net/ipv4/tcp_authopt.c | 199 +++++++++++++++++++++++++++++++++++++- 2 files changed, 214 insertions(+), 1 deletion(-)

diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index bc2cff82830d..ed9995c8d486 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -4,10 +4,24 @@

#include <uapi/linux/tcp.h> #include <net/netns/tcp_authopt.h> #include <linux/tcp.h>

+/* According to RFC5925 the length of the authentication option varies based on + * the signature algorithm. Linux only implements the algorithms defined in + * RFC5926 which have a constant length of 16. + * + * This is used in stack allocation of tcp option buffers for output. It is + * shorter than the length of the MD5 option. + * + * Input packets can have authentication options of different lengths but they + * will always be flagged as invalid (since no such algorithms are supported). + */ +#define TCPOLEN_AUTHOPT_OUTPUT 16 + +struct tcp_authopt_alg_imp; + /** * struct tcp_authopt_key_info - Representation of a Master Key Tuple as per RFC5925 * * Key structure lifetime is protected by RCU so send/recv code needs to hold a * single rcu_read_lock until they're done with the key. @@ -33,10 +47,12 @@ struct tcp_authopt_key_info { u8 keylen; /** @key: Same as &tcp_authopt_key.key */ u8 key[TCP_AUTHOPT_MAXKEYLEN]; /** @addr: Same as &tcp_authopt_key.addr */ struct sockaddr_storage addr; + /** @alg: Algorithm implementation matching alg_id */ + struct tcp_authopt_alg_imp *alg; };

/** * struct tcp_authopt_info - Per-socket information regarding tcp_authopt * diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index d38e9c89c89d..005fac36760b 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -2,15 +2,201 @@

#include <net/tcp_authopt.h> #include <net/ipv6.h> #include <net/tcp.h> #include <linux/kref.h> +#include <crypto/hash.h>

/* This is enabled when first struct tcp_authopt_info is allocated and never released */ DEFINE_STATIC_KEY_FALSE(tcp_authopt_needed_key); EXPORT_SYMBOL(tcp_authopt_needed_key);

+/* All current algorithms have a mac length of 12 but crypto API digestsize can be larger */ +#define TCP_AUTHOPT_MAXMACBUF 20 +#define TCP_AUTHOPT_MAX_TRAFFIC_KEY_LEN 20 +#define TCP_AUTHOPT_MACLEN 12 + +struct tcp_authopt_alg_pool { + struct crypto_ahash *tfm; + struct ahash_request *req; +}; + +/* Constant data with per-algorithm information from RFC5926 + * The "KDF" and "MAC" happen to be the same for both algorithms. + */ +struct tcp_authopt_alg_imp { + /* Name of algorithm in crypto-api */ + const char *alg_name; + /* One of the TCP_AUTHOPT_ALG_* constants from uapi */ + u8 alg_id; + /* Length of traffic key */ + u8 traffic_key_len; + + /* shared crypto_ahash */ + struct mutex init_mutex; + bool init_done; + struct tcp_authopt_alg_pool __percpu *pool; +}; + +static struct tcp_authopt_alg_imp tcp_authopt_alg_list[] = { + { + .alg_id = TCP_AUTHOPT_ALG_HMAC_SHA_1_96, + .alg_name = "hmac(sha1)", + .traffic_key_len = 20, + .init_mutex = __MUTEX_INITIALIZER(tcp_authopt_alg_list[0].init_mutex), + }, + { + .alg_id = TCP_AUTHOPT_ALG_AES_128_CMAC_96, + .alg_name = "cmac(aes)", + .traffic_key_len = 16, + .init_mutex = __MUTEX_INITIALIZER(tcp_authopt_alg_list[1].init_mutex), + }, +}; + +/* get a pointer to the tcp_authopt_alg instance or NULL if id invalid */ +static inline struct tcp_authopt_alg_imp *tcp_authopt_alg_get(int alg_num) +{ + if (alg_num <= 0 || alg_num > 2) + return NULL; + return &tcp_authopt_alg_list[alg_num - 1]; +} + +static int tcp_authopt_alg_pool_init(struct tcp_authopt_alg_imp *alg, + struct tcp_authopt_alg_pool *pool) +{ + pool->tfm = crypto_alloc_ahash(alg->alg_name, 0, CRYPTO_ALG_ASYNC); + if (IS_ERR(pool->tfm)) + return PTR_ERR(pool->tfm); + + pool->req = ahash_request_alloc(pool->tfm, GFP_ATOMIC); + if (IS_ERR(pool->req)) + return PTR_ERR(pool->req); + ahash_request_set_callback(pool->req, 0, NULL, NULL); + + return 0; +} + +static void tcp_authopt_alg_pool_free(struct tcp_authopt_alg_pool *pool) +{ + if (!IS_ERR_OR_NULL(pool->req)) + ahash_request_free(pool->req); + pool->req = NULL; + if (!IS_ERR_OR_NULL(pool->tfm)) + crypto_free_ahash(pool->tfm); + pool->tfm = NULL; +} + +static void __tcp_authopt_alg_free(struct tcp_authopt_alg_imp *alg) +{ + int cpu; + struct tcp_authopt_alg_pool *pool; + + if (!alg->pool) + return; + for_each_possible_cpu(cpu) { + pool = per_cpu_ptr(alg->pool, cpu); + tcp_authopt_alg_pool_free(pool); + } + free_percpu(alg->pool); + alg->pool = NULL; +} + +static int __tcp_authopt_alg_init(struct tcp_authopt_alg_imp *alg) +{ + struct tcp_authopt_alg_pool *pool; + int cpu; + int err; + + BUILD_BUG_ON(TCP_AUTHOPT_MAXMACBUF < TCPOLEN_AUTHOPT_OUTPUT); + if (WARN_ON_ONCE(alg->traffic_key_len > TCP_AUTHOPT_MAX_TRAFFIC_KEY_LEN)) + return -ENOBUFS; + + alg->pool = alloc_percpu(struct tcp_authopt_alg_pool); + if (!alg->pool) + return -ENOMEM; + for_each_possible_cpu(cpu) { + pool = per_cpu_ptr(alg->pool, cpu); + err = tcp_authopt_alg_pool_init(alg, pool); + if (err) + goto out_err; + + pool = per_cpu_ptr(alg->pool, cpu); + /* sanity checks: */ + if (WARN_ON_ONCE(crypto_ahash_digestsize(pool->tfm) != alg->traffic_key_len)) { + err = -EINVAL; + goto out_err; + } + if (WARN_ON_ONCE(crypto_ahash_digestsize(pool->tfm) > TCP_AUTHOPT_MAXMACBUF)) { + err = -EINVAL; + goto out_err; + } + } + return 0; + +out_err: + pr_info("Failed to initialize %s\n", alg->alg_name); + __tcp_authopt_alg_free(alg); + return err; +} + +static int tcp_authopt_alg_require(struct tcp_authopt_alg_imp *alg) +{ + int err = 0; + + mutex_lock(&alg->init_mutex); + if (alg->init_done) + goto out; + err = __tcp_authopt_alg_init(alg); + if (err) + goto out; + pr_info("initialized tcp-ao algorithm %s", alg->alg_name); + alg->init_done = true; + +out: + mutex_unlock(&alg->init_mutex); + return err; +} + +static struct tcp_authopt_alg_pool *tcp_authopt_alg_get_pool(struct tcp_authopt_alg_imp *alg) +{ + local_bh_disable(); + return this_cpu_ptr(alg->pool); +} + +static void tcp_authopt_alg_put_pool(struct tcp_authopt_alg_imp *alg, + struct tcp_authopt_alg_pool *pool) +{ + WARN_ON(pool != this_cpu_ptr(alg->pool)); + local_bh_enable(); +} + +__always_unused +static struct tcp_authopt_alg_pool *tcp_authopt_get_kdf_pool(struct tcp_authopt_key_info *key) +{ + return tcp_authopt_alg_get_pool(key->alg); +} + +__always_unused +static void tcp_authopt_put_kdf_pool(struct tcp_authopt_key_info *key, + struct tcp_authopt_alg_pool *pool) +{ + return tcp_authopt_alg_put_pool(key->alg, pool); +} + +__always_unused +static struct tcp_authopt_alg_pool *tcp_authopt_get_mac_pool(struct tcp_authopt_key_info *key) +{ + return tcp_authopt_alg_get_pool(key->alg); +} + +__always_unused +static void tcp_authopt_put_mac_pool(struct tcp_authopt_key_info *key, + struct tcp_authopt_alg_pool *pool) +{ + return tcp_authopt_alg_put_pool(key->alg, pool); +} + static inline struct netns_tcp_authopt *sock_net_tcp_authopt(const struct sock *sk) { return &sock_net(sk)->tcp_authopt; }

@@ -53,11 +239,10 @@ void tcp_authopt_clear(struct sock *sk) if (info) { tcp_authopt_free(sk, info); tcp_sk(sk)->authopt_info = NULL; } } - /* checks that ipv4 or ipv6 addr matches. */ static bool ipvx_addr_match(struct sockaddr_storage *a1, struct sockaddr_storage *a2) { if (a1->ss_family != a2->ss_family) @@ -212,10 +397,11 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) { struct tcp_authopt_key opt; struct tcp_authopt_info *info; struct tcp_authopt_key_info *key_info, *old_key_info; struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); + struct tcp_authopt_alg_imp *alg; int err;

sock_owned_by_me(sk); if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) return -EPERM; @@ -253,10 +439,20 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) /* Initialize tcp_authopt_info if not already set */ info = __tcp_authopt_info_get_or_create(sk); if (IS_ERR(info)) return PTR_ERR(info);

+ /* check the algorithm */ + alg = tcp_authopt_alg_get(opt.alg); + if (!alg) + return -EINVAL; + if (WARN_ON_ONCE(alg->alg_id != opt.alg)) + return -EINVAL; + err = tcp_authopt_alg_require(alg); + if (err) + return err; + key_info = kmalloc(sizeof(*key_info), GFP_KERNEL | __GFP_ZERO); if (!key_info) return -ENOMEM; mutex_lock(&net->mutex); kref_init(&key_info->ref); @@ -268,10 +464,11 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) tcp_authopt_key_del(net, old_key_info); key_info->flags = opt.flags & TCP_AUTHOPT_KEY_KNOWN_FLAGS; key_info->send_id = opt.send_id; key_info->recv_id = opt.recv_id; key_info->alg_id = opt.alg; + key_info->alg = alg; key_info->keylen = opt.keylen; memcpy(key_info->key, opt.key, opt.keylen); memcpy(&key_info->addr, &opt.addr, sizeof(key_info->addr)); hlist_add_head_rcu(&key_info->node, &net->head); mutex_unlock(&net->mutex);

Computing tcp authopt packet signatures is a two step process:

* traffic key is computed based on tcp 4-tuple, initial sequence numbers and the secret key. * packet mac is computed based on traffic key and content of individual packets.

The traffic key could be cached for established sockets but it is not.

A single code path exists for ipv4/ipv6 and input/output. This keeps the code short but slightly slower due to lots of conditionals.

On output we read remote IP address from socket members on output, we can't use skb network header because it's computed after TCP options.

On input we read remote IP address from skb network headers, we can't use socket binding members because those are not available for SYN.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/net/tcp_authopt.h | 9 + net/ipv4/tcp_authopt.c | 460 +++++++++++++++++++++++++++++++++++++- 2 files changed, 465 insertions(+), 4 deletions(-)

diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index ed9995c8d486..e303ef53e1a3 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -68,10 +68,19 @@ struct tcp_authopt_info { u32 src_isn; /** @dst_isn: Remote Initial Sequence Number */ u32 dst_isn; };

+/* TCP authopt as found in header */ +struct tcphdr_authopt { + u8 num; + u8 len; + u8 keyid; + u8 rnextkeyid; + u8 mac[0]; +}; + #ifdef CONFIG_TCP_AUTHOPT DECLARE_STATIC_KEY_FALSE(tcp_authopt_needed_key); #define tcp_authopt_needed (static_branch_unlikely(&tcp_authopt_needed_key)) void tcp_authopt_clear(struct sock *sk); int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen); diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 005fac36760b..440d329b52f4 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -167,30 +167,26 @@ static void tcp_authopt_alg_put_pool(struct tcp_authopt_alg_imp *alg, { WARN_ON(pool != this_cpu_ptr(alg->pool)); local_bh_enable(); }

-__always_unused static struct tcp_authopt_alg_pool *tcp_authopt_get_kdf_pool(struct tcp_authopt_key_info *key) { return tcp_authopt_alg_get_pool(key->alg); }

-__always_unused static void tcp_authopt_put_kdf_pool(struct tcp_authopt_key_info *key, struct tcp_authopt_alg_pool *pool) { return tcp_authopt_alg_put_pool(key->alg, pool); }

-__always_unused static struct tcp_authopt_alg_pool *tcp_authopt_get_mac_pool(struct tcp_authopt_key_info *key) { return tcp_authopt_alg_get_pool(key->alg); }

-__always_unused static void tcp_authopt_put_mac_pool(struct tcp_authopt_key_info *key, struct tcp_authopt_alg_pool *pool) { return tcp_authopt_alg_put_pool(key->alg, pool); } @@ -474,10 +470,466 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) mutex_unlock(&net->mutex);

return 0; }

+static int tcp_authopt_get_isn(struct sock *sk, + struct tcp_authopt_info *info, + struct sk_buff *skb, + int input, + __be32 *sisn, + __be32 *disn) +{ + struct tcphdr *th = tcp_hdr(skb); + + /* Special cases for SYN and SYN/ACK */ + if (th->syn && !th->ack) { + *sisn = th->seq; + *disn = 0; + return 0; + } + if (th->syn && th->ack) { + *sisn = th->seq; + *disn = htonl(ntohl(th->ack_seq) - 1); + return 0; + } + + if (sk->sk_state == TCP_NEW_SYN_RECV) { + struct tcp_request_sock *rsk = (struct tcp_request_sock *)sk; + + if (WARN_ONCE(!input, "Caller passed wrong socket")) + return -EINVAL; + *sisn = htonl(rsk->rcv_isn); + *disn = htonl(rsk->snt_isn); + return 0; + } else if (sk->sk_state == TCP_LISTEN) { + /* Signature computation for non-syn packet on a listen + * socket is not possible because we lack the initial + * sequence numbers. + * + * Input segments that are not matched by any request, + * established or timewait socket will get here. These + * are not normally sent by peers. + * + * Their signature might be valid but we don't have + * enough state to determine that. TCP-MD5 can attempt + * to validate and reply with a signed RST because it + * doesn't care about ISNs. + * + * Reporting an error from signature code causes the + * packet to be discarded which is good. + */ + if (WARN_ONCE(!input, "Caller passed wrong socket")) + return -EINVAL; + *sisn = 0; + *disn = 0; + return 0; + } + if (WARN_ONCE(!info, "caller did not pass tcp_authopt_info\n")) + return -EINVAL; + /* Initial sequence numbers for ESTABLISHED connections from info */ + if (input) { + *sisn = htonl(info->dst_isn); + *disn = htonl(info->src_isn); + } else { + *sisn = htonl(info->src_isn); + *disn = htonl(info->dst_isn); + } + return 0; +} + +/* Feed one buffer into ahash + * The buffer is assumed to be DMA-able + */ +static int crypto_ahash_buf(struct ahash_request *req, u8 *buf, uint len) +{ + struct scatterlist sg; + + sg_init_one(&sg, buf, len); + ahash_request_set_crypt(req, &sg, NULL, len); + + return crypto_ahash_update(req); +} + +/* feed traffic key into ahash */ +static int tcp_authopt_ahash_traffic_key(struct tcp_authopt_alg_pool *pool, + struct sock *sk, + struct sk_buff *skb, + struct tcp_authopt_info *info, + bool input, + bool ipv6) +{ + struct tcphdr *th = tcp_hdr(skb); + int err; + __be32 sisn, disn; + __be16 digestbits = htons(crypto_ahash_digestsize(pool->tfm) * 8); + /* For ahash const data buffers don't work so ensure header is on stack */ + char traffic_key_context_header[7] = "\x01TCP-AO"; + + // RFC5926 section 3.1.1.1 + err = crypto_ahash_buf(pool->req, traffic_key_context_header, 7); + if (err) + return err; + + /* Addresses from packet on input and from sk_common on output + * This is because on output MAC is computed before prepending IP header + */ + if (input) { + if (ipv6) + err = crypto_ahash_buf(pool->req, (u8 *)&ipv6_hdr(skb)->saddr, 32); + else + err = crypto_ahash_buf(pool->req, (u8 *)&ip_hdr(skb)->saddr, 8); + if (err) + return err; + } else { + if (ipv6) { +#if IS_ENABLED(CONFIG_IPV6) + err = crypto_ahash_buf(pool->req, (u8 *)&sk->sk_v6_rcv_saddr, 16); + if (err) + return err; + err = crypto_ahash_buf(pool->req, (u8 *)&sk->sk_v6_daddr, 16); + if (err) + return err; +#else + return -EINVAL; +#endif + } else { + err = crypto_ahash_buf(pool->req, (u8 *)&sk->sk_rcv_saddr, 4); + if (err) + return err; + err = crypto_ahash_buf(pool->req, (u8 *)&sk->sk_daddr, 4); + if (err) + return err; + } + } + + /* TCP ports from header */ + err = crypto_ahash_buf(pool->req, (u8 *)&th->source, 4); + if (err) + return err; + err = tcp_authopt_get_isn(sk, info, skb, input, &sisn, &disn); + if (err) + return err; + err = crypto_ahash_buf(pool->req, (u8 *)&sisn, 4); + if (err) + return err; + err = crypto_ahash_buf(pool->req, (u8 *)&disn, 4); + if (err) + return err; + err = crypto_ahash_buf(pool->req, (u8 *)&digestbits, 2); + if (err) + return err; + + return 0; +} + +/* Convert a variable-length key to a 16-byte fixed-length key for AES-CMAC + * This is described in RFC5926 section 3.1.1.2 + */ +static int aes_setkey_derived(struct crypto_ahash *tfm, struct ahash_request *req, + u8 *key, size_t keylen) +{ + static const u8 zeros[16] = {0}; + struct scatterlist sg; + u8 derived_key[16]; + int err; + + if (WARN_ON_ONCE(crypto_ahash_digestsize(tfm) != sizeof(derived_key))) + return -EINVAL; + err = crypto_ahash_setkey(tfm, zeros, sizeof(zeros)); + if (err) + return err; + err = crypto_ahash_init(req); + if (err) + return err; + sg_init_one(&sg, key, keylen); + ahash_request_set_crypt(req, &sg, derived_key, keylen); + err = crypto_ahash_digest(req); + if (err) + return err; + return crypto_ahash_setkey(tfm, derived_key, sizeof(derived_key)); +} + +static int tcp_authopt_setkey(struct tcp_authopt_alg_pool *pool, struct tcp_authopt_key_info *key) +{ + if (key->alg_id == TCP_AUTHOPT_ALG_AES_128_CMAC_96 && key->keylen != 16) + return aes_setkey_derived(pool->tfm, pool->req, key->key, key->keylen); + else + return crypto_ahash_setkey(pool->tfm, key->key, key->keylen); +} + +static int tcp_authopt_get_traffic_key(struct sock *sk, + struct sk_buff *skb, + struct tcp_authopt_key_info *key, + struct tcp_authopt_info *info, + bool input, + bool ipv6, + u8 *traffic_key) +{ + struct tcp_authopt_alg_pool *pool; + int err; + + pool = tcp_authopt_get_kdf_pool(key); + if (IS_ERR(pool)) + return PTR_ERR(pool); + + err = tcp_authopt_setkey(pool, key); + if (err) + goto out; + err = crypto_ahash_init(pool->req); + if (err) + goto out; + + err = tcp_authopt_ahash_traffic_key(pool, sk, skb, info, input, ipv6); + if (err) + goto out; + + ahash_request_set_crypt(pool->req, NULL, traffic_key, 0); + err = crypto_ahash_final(pool->req); + if (err) + return err; + +out: + tcp_authopt_put_kdf_pool(key, pool); + return err; +} + +static int crypto_ahash_buf_zero(struct ahash_request *req, int len) +{ + u8 zeros[TCP_AUTHOPT_MACLEN] = {0}; + int buflen, err; + + /* In practice this is always called with len exactly 12. + * Even on input we drop unusual signature sizes early. + */ + while (len) { + buflen = min_t(int, len, sizeof(zeros)); + err = crypto_ahash_buf(req, zeros, buflen); + if (err) + return err; + len -= buflen; + } + + return 0; +} + +static int tcp_authopt_hash_tcp4_pseudoheader(struct tcp_authopt_alg_pool *pool, + __be32 saddr, + __be32 daddr, + int nbytes) +{ + struct tcp4_pseudohdr phdr = { + .saddr = saddr, + .daddr = daddr, + .pad = 0, + .protocol = IPPROTO_TCP, + .len = htons(nbytes) + }; + return crypto_ahash_buf(pool->req, (u8 *)&phdr, sizeof(phdr)); +} + +#if IS_ENABLED(CONFIG_IPV6) +static int tcp_authopt_hash_tcp6_pseudoheader(struct tcp_authopt_alg_pool *pool, + struct in6_addr *saddr, + struct in6_addr *daddr, + u32 plen) +{ + int err; + __be32 buf[2]; + + buf[0] = htonl(plen); + buf[1] = htonl(IPPROTO_TCP); + + err = crypto_ahash_buf(pool->req, (u8 *)saddr, sizeof(*saddr)); + if (err) + return err; + err = crypto_ahash_buf(pool->req, (u8 *)daddr, sizeof(*daddr)); + if (err) + return err; + return crypto_ahash_buf(pool->req, (u8 *)&buf, sizeof(buf)); +} +#endif + +/** Hash tcphdr options. + * + * If include_options is false then only the TCPOPT_AUTHOPT option itself is hashed + * Point to AO inside TH is passed by the caller + */ +static int tcp_authopt_hash_opts(struct tcp_authopt_alg_pool *pool, + struct tcphdr *th, + struct tcphdr_authopt *aoptr, + bool include_options) +{ + int err; + /* start of options */ + u8 *tcp_opts = (u8 *)(th + 1); + /* start of options */ + u8 *aobuf = (u8 *)aoptr; + u8 aolen = aoptr->len; + + if (WARN_ONCE(aoptr->num != TCPOPT_AUTHOPT, "Bad aoptr\n")) + return -EINVAL; + + if (include_options) { + /* end of options */ + u8 *tcp_data = ((u8 *)th) + th->doff * 4; + + err = crypto_ahash_buf(pool->req, tcp_opts, aobuf - tcp_opts + 4); + if (err) + return err; + err = crypto_ahash_buf_zero(pool->req, aolen - 4); + if (err) + return err; + err = crypto_ahash_buf(pool->req, aobuf + aolen, tcp_data - (aobuf + aolen)); + if (err) + return err; + } else { + err = crypto_ahash_buf(pool->req, aobuf, 4); + if (err) + return err; + err = crypto_ahash_buf_zero(pool->req, aolen - 4); + if (err) + return err; + } + + return 0; +} + +static int tcp_authopt_hash_packet(struct tcp_authopt_alg_pool *pool, + struct sock *sk, + struct sk_buff *skb, + struct tcphdr_authopt *aoptr, + struct tcp_authopt_info *info, + bool input, + bool ipv6, + bool include_options, + u8 *macbuf) +{ + struct tcphdr *th = tcp_hdr(skb); + int err; + + /* NOTE: SNE unimplemented */ + __be32 sne = 0; + + err = crypto_ahash_init(pool->req); + if (err) + return err; + + err = crypto_ahash_buf(pool->req, (u8 *)&sne, 4); + if (err) + return err; + + if (ipv6) { +#if IS_ENABLED(CONFIG_IPV6) + struct in6_addr *saddr; + struct in6_addr *daddr; + + if (input) { + saddr = &ipv6_hdr(skb)->saddr; + daddr = &ipv6_hdr(skb)->daddr; + } else { + saddr = &sk->sk_v6_rcv_saddr; + daddr = &sk->sk_v6_daddr; + } + err = tcp_authopt_hash_tcp6_pseudoheader(pool, saddr, daddr, skb->len); + if (err) + return err; +#else + return -EINVAL; +#endif + } else { + __be32 saddr; + __be32 daddr; + + if (input) { + saddr = ip_hdr(skb)->saddr; + daddr = ip_hdr(skb)->daddr; + } else { + saddr = sk->sk_rcv_saddr; + daddr = sk->sk_daddr; + } + err = tcp_authopt_hash_tcp4_pseudoheader(pool, saddr, daddr, skb->len); + if (err) + return err; + } + + // TCP header with checksum set to zero + { + struct tcphdr hashed_th = *th; + + hashed_th.check = 0; + err = crypto_ahash_buf(pool->req, (u8 *)&hashed_th, sizeof(hashed_th)); + if (err) + return err; + } + + // TCP options + err = tcp_authopt_hash_opts(pool, th, aoptr, include_options); + if (err) + return err; + + // Rest of SKB->data + err = tcp_sig_hash_skb_data(pool->req, skb, th->doff << 2); + if (err) + return err; + + ahash_request_set_crypt(pool->req, NULL, macbuf, 0); + return crypto_ahash_final(pool->req); +} + +/* __tcp_authopt_calc_mac - Compute packet MAC using key + * + * The macbuf output buffer must be large enough to fit the digestsize of the + * underlying transform before truncation. + * This means TCP_AUTHOPT_MAXMACBUF, not TCP_AUTHOPT_MACLEN + */ +__always_unused +static int __tcp_authopt_calc_mac(struct sock *sk, + struct sk_buff *skb, + struct tcphdr_authopt *aoptr, + struct tcp_authopt_key_info *key, + struct tcp_authopt_info *info, + bool input, + char *macbuf) +{ + struct tcp_authopt_alg_pool *mac_pool; + u8 traffic_key[TCP_AUTHOPT_MAX_TRAFFIC_KEY_LEN]; + int err; + bool ipv6 = (sk->sk_family != AF_INET); + + if (sk->sk_family != AF_INET && sk->sk_family != AF_INET6) + return -EINVAL; + + err = tcp_authopt_get_traffic_key(sk, skb, key, info, input, ipv6, traffic_key); + if (err) + return err; + + mac_pool = tcp_authopt_get_mac_pool(key); + if (IS_ERR(mac_pool)) + return PTR_ERR(mac_pool); + err = crypto_ahash_setkey(mac_pool->tfm, traffic_key, key->alg->traffic_key_len); + if (err) + goto out; + err = crypto_ahash_init(mac_pool->req); + if (err) + return err; + + err = tcp_authopt_hash_packet(mac_pool, + sk, + skb, + aoptr, + info, + input, + ipv6, + !(key->flags & TCP_AUTHOPT_KEY_EXCLUDE_OPTS), + macbuf); + +out: + tcp_authopt_put_mac_pool(key, mac_pool); + return err; +} + static int tcp_authopt_init_net(struct net *full_net) { struct netns_tcp_authopt *net = &full_net->tcp_authopt;

mutex_init(&net->mutex);

The tcp_authopt features exposes a minimal interface to the rest of the TCP stack. Only a few functions are exposed and if the feature is disabled they return neutral values, avoiding ifdefs in the rest of the code. This approach is different from MD5.

Add calls into tcp authopt from send, receive, accept, close code.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/net/dropreason.h | 12 ++ include/net/tcp_authopt.h | 85 +++++++++++ include/uapi/linux/snmp.h | 1 + net/ipv4/proc.c | 1 + net/ipv4/tcp.c | 17 +++ net/ipv4/tcp_authopt.c | 298 +++++++++++++++++++++++++++++++++++++- net/ipv4/tcp_input.c | 3 + net/ipv4/tcp_minisocks.c | 12 ++ net/ipv4/tcp_output.c | 85 ++++++++++- 9 files changed, 511 insertions(+), 3 deletions(-)

diff --git a/include/net/dropreason.h b/include/net/dropreason.h index c5397c24296c..d5dd92affde8 100644 --- a/include/net/dropreason.h +++ b/include/net/dropreason.h @@ -233,10 +233,22 @@ enum skb_drop_reason { SKB_DROP_REASON_PKT_TOO_BIG, /** * @SKB_DROP_REASON_TCP_BOTHAOMD5: Both AO and MD5 found in packet. */ SKB_DROP_REASON_TCP_BOTHAOMD5, + /** + * @SKB_DROP_REASON_TCP_AONOTFOUND: No AO signature and one expected. + */ + SKB_DROP_REASON_TCP_AONOTFOUND, + /** + * @SKB_DROP_REASON_TCP_AOUNEXPECTED: AO hash and we're not expecting + */ + SKB_DROP_REASON_TCP_AOUNEXPECTED, + /** + * @SKB_DROP_REASON_TCP_AOFAILURE: AO hash incorrect + */ + SKB_DROP_REASON_TCP_AOFAILURE, /** * @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be * used as a real 'reason' */ SKB_DROP_REASON_MAX, diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index e303ef53e1a3..7ad34a6987ec 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -80,16 +80,101 @@ struct tcphdr_authopt { };

#ifdef CONFIG_TCP_AUTHOPT DECLARE_STATIC_KEY_FALSE(tcp_authopt_needed_key); #define tcp_authopt_needed (static_branch_unlikely(&tcp_authopt_needed_key)) +void tcp_authopt_free(struct sock *sk, struct tcp_authopt_info *info); void tcp_authopt_clear(struct sock *sk); int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen); int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *key); int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen); +struct tcp_authopt_key_info *__tcp_authopt_select_key( + const struct sock *sk, + struct tcp_authopt_info *info, + const struct sock *addr_sk, + u8 *rnextkeyid); +static inline struct tcp_authopt_key_info *tcp_authopt_select_key( + const struct sock *sk, + const struct sock *addr_sk, + struct tcp_authopt_info **info, + u8 *rnextkeyid) +{ + if (tcp_authopt_needed) { + *info = rcu_dereference(tcp_sk(sk)->authopt_info); + + if (*info) + return __tcp_authopt_select_key(sk, *info, addr_sk, rnextkeyid); + } + return NULL; +} +int tcp_authopt_hash( + char *hash_location, + struct tcp_authopt_key_info *key, + struct tcp_authopt_info *info, + struct sock *sk, struct sk_buff *skb); +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req); +static inline int tcp_authopt_openreq( + struct sock *newsk, + const struct sock *oldsk, + struct request_sock *req) +{ + if (!rcu_dereference(tcp_sk(oldsk)->authopt_info)) + return 0; + else + return __tcp_authopt_openreq(newsk, oldsk, req); +} +void __tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb, + struct tcp_authopt_info *info); +static inline void tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_authopt_info *info; + + if (skb && tcp_authopt_needed) { + info = rcu_dereference_protected(tcp_sk(sk)->authopt_info, + lockdep_sock_is_held(sk)); + + if (info) + __tcp_authopt_finish_connect(sk, skb, info); + } +} +static inline void tcp_authopt_time_wait( + struct tcp_timewait_sock *tcptw, + struct tcp_sock *tp) +{ + if (tcp_authopt_needed) { + /* Transfer ownership of authopt_info to the twsk + * This requires no other users of the origin sock. + */ + tcptw->tw_authopt_info = rcu_dereference_protected( + tp->authopt_info, + lockdep_sock_is_held((struct sock *)tp)); + rcu_assign_pointer(tp->authopt_info, NULL); + } else { + tcptw->tw_authopt_info = NULL; + } +} +int __tcp_authopt_inbound_check( + struct sock *sk, + struct sk_buff *skb, + struct tcp_authopt_info *info, + const u8 *opt); #else static inline void tcp_authopt_clear(struct sock *sk) { } +static inline int tcp_authopt_openreq(struct sock *newsk, + const struct sock *oldsk, + struct request_sock *req) +{ + return 0; +} +static inline void tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb) +{ +} +static inline void tcp_authopt_time_wait( + struct tcp_timewait_sock *tcptw, + struct tcp_sock *tp) +{ +} #endif

#endif /* _LINUX_TCP_AUTHOPT_H */ diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h index 4d7470036a8b..ae2738a7992b 100644 --- a/include/uapi/linux/snmp.h +++ b/include/uapi/linux/snmp.h @@ -290,10 +290,11 @@ enum LINUX_MIB_TCPDUPLICATEDATAREHASH, /* TCPDuplicateDataRehash */ LINUX_MIB_TCPDSACKRECVSEGS, /* TCPDSACKRecvSegs */ LINUX_MIB_TCPDSACKIGNOREDDUBIOUS, /* TCPDSACKIgnoredDubious */ LINUX_MIB_TCPMIGRATEREQSUCCESS, /* TCPMigrateReqSuccess */ LINUX_MIB_TCPMIGRATEREQFAILURE, /* TCPMigrateReqFailure */ + LINUX_MIB_TCPAUTHOPTFAILURE, /* TCPAuthOptFailure */ __LINUX_MIB_MAX };

/* linux Xfrm mib definitions */ enum diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index 0088a4c64d77..e48c7245c571 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -295,10 +295,11 @@ static const struct snmp_mib snmp4_net_list[] = { SNMP_MIB_ITEM("TcpDuplicateDataRehash", LINUX_MIB_TCPDUPLICATEDATAREHASH), SNMP_MIB_ITEM("TCPDSACKRecvSegs", LINUX_MIB_TCPDSACKRECVSEGS), SNMP_MIB_ITEM("TCPDSACKIgnoredDubious", LINUX_MIB_TCPDSACKIGNOREDDUBIOUS), SNMP_MIB_ITEM("TCPMigrateReqSuccess", LINUX_MIB_TCPMIGRATEREQSUCCESS), SNMP_MIB_ITEM("TCPMigrateReqFailure", LINUX_MIB_TCPMIGRATEREQFAILURE), + SNMP_MIB_ITEM("TCPAuthOptFailure", LINUX_MIB_TCPAUTHOPTFAILURE), SNMP_MIB_SENTINEL };

static void icmpmsg_put_line(struct seq_file *seq, unsigned long *vals, unsigned short *type, int count) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index d159f1b66930..dd31e78bd22d 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4667,10 +4667,27 @@ tcp_inbound_sig_hash(const struct sock *sk, const struct sk_buff *skb,

ret = tcp_parse_sig_options(tcp_hdr(skb), &md5, &ao); if (ret) return ret;

+#if defined(CONFIG_TCP_AUTHOPT) + if (tcp_authopt_needed) { + struct tcp_authopt_info *info = rcu_dereference(tcp_sk(parent_sk)->authopt_info); + int aoret; + + if (info) { + aoret = __tcp_authopt_inbound_check((struct sock *)sk, + (struct sk_buff *)skb, + info, ao); + /* Don't do MD5 lookup if AO found */ + if (aoret == 1) + return SKB_NOT_DROPPED_YET; + if (aoret < 0) + return -aoret; + } + } +#endif #ifdef CONFIG_TCP_MD5SIG return tcp_inbound_md5_hash(parent_sk, skb, saddr, daddr, family, dif, sdif, md5); #else return SKB_NOT_DROPPED_YET; #endif diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 440d329b52f4..4f7cbe1e17f3 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -268,10 +268,57 @@ static bool tcp_authopt_key_match_exact(struct tcp_authopt_key_info *info, return false;

return true; }

+static bool tcp_authopt_key_match_skb_addr(struct tcp_authopt_key_info *key, + struct sk_buff *skb) +{ + u16 keyaf = key->addr.ss_family; + struct iphdr *iph = (struct iphdr *)skb_network_header(skb); + + if (keyaf == AF_INET && iph->version == 4) { + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; + + return iph->saddr == key_addr->sin_addr.s_addr; + } else if (keyaf == AF_INET6 && iph->version == 6) { + struct ipv6hdr *ip6h = (struct ipv6hdr *)skb_network_header(skb); + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; + + return ipv6_addr_equal(&ip6h->saddr, &key_addr->sin6_addr); + } + + /* This actually happens with ipv6-mapped-ipv4-addresses + * IPv6 listen sockets will be asked to validate ipv4 packets. + */ + return false; +} + +static bool tcp_authopt_key_match_sk_addr(struct tcp_authopt_key_info *key, + const struct sock *addr_sk) +{ + u16 keyaf = key->addr.ss_family; + + /* This probably can't happen even with ipv4-mapped-ipv6 */ + if (keyaf != addr_sk->sk_family) + return false; + + if (keyaf == AF_INET) { + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; + + return addr_sk->sk_daddr == key_addr->sin_addr.s_addr; +#if IS_ENABLED(CONFIG_IPV6) + } else if (keyaf == AF_INET6) { + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; + + return ipv6_addr_equal(&addr_sk->sk_v6_daddr, &key_addr->sin6_addr); +#endif + } + + return false; +} + static struct tcp_authopt_key_info *tcp_authopt_key_lookup_exact(const struct sock *sk, struct netns_tcp_authopt *net, struct tcp_authopt_key *ukey) { struct tcp_authopt_key_info *key_info; @@ -281,10 +328,59 @@ static struct tcp_authopt_key_info *tcp_authopt_key_lookup_exact(const struct so return key_info;

return NULL; }

+/** + * tcp_authopt_lookup_send - lookup key for sending + * + * @net: Per-namespace information containing keys + * @addr_sk: Socket used for destination address lookup + * + * If anykey is false then authentication is not required for peer. + * + * If anykey is true but no key was found then all our keys must be expired and sending should fail. + */ +static struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct netns_tcp_authopt *net, + const struct sock *addr_sk) +{ + struct tcp_authopt_key_info *result = NULL; + struct tcp_authopt_key_info *key; + + hlist_for_each_entry_rcu(key, &net->head, node, 0) { + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) + if (!tcp_authopt_key_match_sk_addr(key, addr_sk)) + continue; + if (result && net_ratelimit()) + pr_warn("ambiguous tcp authentication keys configured for send\n"); + result = key; + } + + return result; +} + +/** + * __tcp_authopt_select_key - select key for sending + * + * @sk: socket + * @info: socket's tcp_authopt_info + * @addr_sk: socket used for address lookup. Same as sk except for synack case + * @rnextkeyid: value of rnextkeyid caller should write in packet + * + * Result is protected by RCU and can't be stored, it may only be passed to + * tcp_authopt_hash and only under a single rcu_read_lock. + */ +struct tcp_authopt_key_info *__tcp_authopt_select_key(const struct sock *sk, + struct tcp_authopt_info *info, + const struct sock *addr_sk, + u8 *rnextkeyid) +{ + struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); + + return tcp_authopt_lookup_send(net, addr_sk); +} + static struct tcp_authopt_info *__tcp_authopt_info_get_or_create(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_authopt_info *info;

@@ -548,10 +644,45 @@ static int crypto_ahash_buf(struct ahash_request *req, u8 *buf, uint len) ahash_request_set_crypt(req, &sg, NULL, len);

return crypto_ahash_update(req); }

+/** Called to create accepted sockets. + * + * Need to copy authopt info from listen socket. + */ +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req) +{ + struct tcp_authopt_info *old_info; + struct tcp_authopt_info *new_info; + + old_info = rcu_dereference(tcp_sk(oldsk)->authopt_info); + if (!old_info) + return 0; + + /* Clear value copies from oldsk: */ + rcu_assign_pointer(tcp_sk(newsk)->authopt_info, NULL); + + new_info = kzalloc(sizeof(*new_info), GFP_ATOMIC); + if (!new_info) + return -ENOMEM; + + new_info->src_isn = tcp_rsk(req)->snt_isn; + new_info->dst_isn = tcp_rsk(req)->rcv_isn; + sk_gso_disable(newsk); + rcu_assign_pointer(tcp_sk(newsk)->authopt_info, new_info); + + return 0; +} + +void __tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb, + struct tcp_authopt_info *info) +{ + info->src_isn = ntohl(tcp_hdr(skb)->ack_seq) - 1; + info->dst_isn = ntohl(tcp_hdr(skb)->seq); +} + /* feed traffic key into ahash */ static int tcp_authopt_ahash_traffic_key(struct tcp_authopt_alg_pool *pool, struct sock *sk, struct sk_buff *skb, struct tcp_authopt_info *info, @@ -880,11 +1011,10 @@ static int tcp_authopt_hash_packet(struct tcp_authopt_alg_pool *pool, * * The macbuf output buffer must be large enough to fit the digestsize of the * underlying transform before truncation. * This means TCP_AUTHOPT_MAXMACBUF, not TCP_AUTHOPT_MACLEN */ -__always_unused static int __tcp_authopt_calc_mac(struct sock *sk, struct sk_buff *skb, struct tcphdr_authopt *aoptr, struct tcp_authopt_key_info *key, struct tcp_authopt_info *info, @@ -926,10 +1056,176 @@ static int __tcp_authopt_calc_mac(struct sock *sk, out: tcp_authopt_put_mac_pool(key, mac_pool); return err; }

+/* tcp_authopt_hash - fill in the mac + * + * The key must come from tcp_authopt_select_key. + */ +int tcp_authopt_hash(char *hash_location, + struct tcp_authopt_key_info *key, + struct tcp_authopt_info *info, + struct sock *sk, + struct sk_buff *skb) +{ + /* MAC inside option is truncated to 12 bytes but crypto API needs output + * buffer to be large enough so we use a buffer on the stack. + */ + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; + int err; + struct tcphdr_authopt *aoptr = (struct tcphdr_authopt *)(hash_location - 4); + + err = __tcp_authopt_calc_mac(sk, skb, aoptr, key, info, false, macbuf); + if (err) + goto fail; + memcpy(hash_location, macbuf, TCP_AUTHOPT_MACLEN); + + return 0; + +fail: + /* If mac calculation fails and caller doesn't handle the error + * try to make it obvious inside the packet. + */ + memset(hash_location, 0, TCP_AUTHOPT_MACLEN); + return err; +} + +/** + * tcp_authopt_lookup_recv - lookup key for receive + * + * @sk: Receive socket + * @skb: Packet, used to compare addr and iface + * @net: Per-namespace information containing keys + * @recv_id: Optional recv_id. If >= 0 then only return keys that match + * @anykey: Set to true if any keys are present for the peer + * + * If anykey is false then authentication is not expected from peer. + * + * If anykey is true then a valid key is required. + */ +static struct tcp_authopt_key_info *tcp_authopt_lookup_recv(struct sock *sk, + struct sk_buff *skb, + struct netns_tcp_authopt *net, + int recv_id, + bool *anykey) +{ + struct tcp_authopt_key_info *result = NULL; + struct tcp_authopt_key_info *key; + + *anykey = false; + /* multiple matches will cause occasional failures */ + hlist_for_each_entry_rcu(key, &net->head, node, 0) { + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND && + !tcp_authopt_key_match_skb_addr(key, skb)) + continue; + *anykey = true; + if (recv_id >= 0 && key->recv_id != recv_id) + continue; + if (!result) + result = key; + else if (result) + net_warn_ratelimited("ambiguous tcp authentication keys configured for recv\n"); + } + + return result; +} + +/* Show a rate-limited message for authentication fail */ +static void print_tcpao_notice(const char *msg, struct sk_buff *skb) +{ + struct iphdr *iph = (struct iphdr *)skb_network_header(skb); + struct tcphdr *th = (struct tcphdr *)skb_transport_header(skb); + + if (iph->version == 4) { + net_info_ratelimited("%s (%pI4, %d)->(%pI4, %d)\n", msg, + &iph->saddr, ntohs(th->source), + &iph->daddr, ntohs(th->dest)); + } else if (iph->version == 6) { + struct ipv6hdr *ip6h = (struct ipv6hdr *)skb_network_header(skb); + + net_info_ratelimited("%s (%pI6, %d)->(%pI6, %d)\n", msg, + &ip6h->saddr, ntohs(th->source), + &ip6h->daddr, ntohs(th->dest)); + } else { + WARN_ONCE(1, "%s unknown IP version\n", msg); + } +} + +/** + * __tcp_authopt_inbound_check - Check inbound TCP authentication option + * + * @sk: Receive socket. For the SYN_RECV state this must be the request_sock, not the listener + * @skb: Input Packet + * @info: TCP authentication option information + * @_opt: Pointer to TCP authentication option inside the skb + * + * Return: + * 0: Nothing found or expected + * 1: Found and verified + * <0: Error, negative skb_drop_reason + */ +int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, + struct tcp_authopt_info *info, const u8 *_opt) +{ + struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); + struct tcphdr_authopt *opt = (struct tcphdr_authopt *)_opt; + struct tcp_authopt_key_info *key; + bool anykey; + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; + int err; + + key = tcp_authopt_lookup_recv(sk, skb, net, opt ? opt->keyid : -1, &anykey); + + /* nothing found or expected */ + if (!opt && !anykey) + return 0; + if (!opt && anykey) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); + print_tcpao_notice("TCP Authentication Missing", skb); + return -SKB_DROP_REASON_TCP_AONOTFOUND; + } + if (opt && !anykey) { + /* RFC5925 Section 7.3: + * A TCP-AO implementation MUST allow for configuration of the behavior + * of segments with TCP-AO but that do not match an MKT. The initial + * default of this configuration SHOULD be to silently accept such + * connections. + */ + if (info->flags & TCP_AUTHOPT_FLAG_REJECT_UNEXPECTED) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); + print_tcpao_notice("TCP Authentication Unexpected: Rejected", skb); + return -SKB_DROP_REASON_TCP_AOUNEXPECTED; + } + print_tcpao_notice("TCP Authentication Unexpected: Accepted", skb); + return 0; + } + if (opt && !key) { + /* Keys are configured for peer but with different keyid than packet */ + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); + print_tcpao_notice("TCP Authentication Failed", skb); + return -SKB_DROP_REASON_TCP_AOFAILURE; + } + + /* bad inbound key len */ + if (opt->len != TCPOLEN_AUTHOPT_OUTPUT) + return -SKB_DROP_REASON_TCP_AOFAILURE; + + err = __tcp_authopt_calc_mac(sk, skb, opt, key, info, true, macbuf); + if (err) + return -SKB_DROP_REASON_TCP_AOFAILURE; + + if (memcmp(macbuf, opt->mac, TCP_AUTHOPT_MACLEN)) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); + print_tcpao_notice("TCP Authentication Failed", skb); + return -SKB_DROP_REASON_TCP_AOFAILURE; + } + + return 1; +} +EXPORT_SYMBOL(__tcp_authopt_inbound_check); + static int tcp_authopt_init_net(struct net *full_net) { struct netns_tcp_authopt *net = &full_net->tcp_authopt;

mutex_init(&net->mutex); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a6b43fb954b7..9f065469562d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -70,10 +70,11 @@ #include <linux/sysctl.h> #include <linux/kernel.h> #include <linux/prefetch.h> #include <net/dst.h> #include <net/tcp.h> +#include <net/tcp_authopt.h> #include <net/inet_common.h> #include <linux/ipsec.h> #include <asm/unaligned.h> #include <linux/errqueue.h> #include <trace/events/tcp.h> @@ -6060,10 +6061,12 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) struct inet_connection_sock *icsk = inet_csk(sk);

tcp_set_state(sk, TCP_ESTABLISHED); icsk->icsk_ack.lrcvtime = tcp_jiffies32;

+ tcp_authopt_finish_connect(sk, skb); + if (skb) { icsk->icsk_af_ops->sk_rx_dst_set(sk, skb); security_inet_conn_established(sk, skb); sk_mark_napi_id(sk, skb); } diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index cb95d88497ae..64357bf5ede2 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -18,10 +18,11 @@ * Arnt Gulbrandsen, agulbra@nvg.unit.no * Jorge Cwik, jorge@laser.satlink.net */

#include <net/tcp.h> +#include <net/tcp_authopt.h> #include <net/xfrm.h> #include <net/busy_poll.h>

static bool tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win) { @@ -300,10 +301,11 @@ void tcp_time_wait(struct sock *sk, int state, int timeo) BUG_ON(tcptw->tw_md5_key && !tcp_alloc_md5sig_pool()); } } } while (0); #endif + tcp_authopt_time_wait(tcptw, tcp_sk(sk));

/* Get the TIME_WAIT timeout firing. */ if (timeo < rto) timeo = rto;

@@ -342,10 +344,19 @@ void tcp_twsk_destructor(struct sock *sk)

if (twsk->tw_md5_key) kfree_rcu(twsk->tw_md5_key, rcu); } #endif +#ifdef CONFIG_TCP_AUTHOPT + if (tcp_authopt_needed) { + struct tcp_timewait_sock *twsk = tcp_twsk(sk); + + /* twsk only contains sock_common so pass NULL as sk. */ + if (twsk->tw_authopt_info) + tcp_authopt_free(NULL, twsk->tw_authopt_info); + } +#endif } EXPORT_SYMBOL_GPL(tcp_twsk_destructor);

/* Warning : This function is called without sk_listener being locked. * Be sure to read socket fields once, as their value could change under us. @@ -532,10 +543,11 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, #ifdef CONFIG_TCP_MD5SIG newtp->md5sig_info = NULL; /*XXX*/ if (treq->af_specific->req_md5_lookup(sk, req_to_sk(req))) newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; #endif + tcp_authopt_openreq(newsk, sk, req); if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len) newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len; newtp->rx_opt.mss_clamp = req->mss; tcp_ecn_openreq_child(newtp, req); newtp->fastopen_req = NULL; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 290019de766d..da683f7951eb 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -37,10 +37,11 @@

#define pr_fmt(fmt) "TCP: " fmt

#include <net/tcp.h> #include <net/mptcp.h> +#include <net/tcp_authopt.h>

#include <linux/compiler.h> #include <linux/gfp.h> #include <linux/module.h> #include <linux/static_key.h> @@ -408,10 +409,11 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)

#define OPTION_SACK_ADVERTISE BIT(0) #define OPTION_TS BIT(1) #define OPTION_MD5 BIT(2) #define OPTION_WSCALE BIT(3) +#define OPTION_AUTHOPT BIT(4) #define OPTION_FAST_OPEN_COOKIE BIT(8) #define OPTION_SMC BIT(9) #define OPTION_MPTCP BIT(10)

static void smc_options_write(__be32 *ptr, u16 *options) @@ -432,16 +434,22 @@ static void smc_options_write(__be32 *ptr, u16 *options) struct tcp_out_options { u16 options; /* bit field of OPTION_* */ u16 mss; /* 0 to disable */ u8 ws; /* window scale, 0 to disable */ u8 num_sack_blocks; /* number of SACK blocks to include */ - u8 hash_size; /* bytes in hash_location */ u8 bpf_opt_len; /* length of BPF hdr option */ +#ifdef CONFIG_TCP_AUTHOPT + u8 authopt_rnextkeyid; /* rnextkey */ +#endif __u8 *hash_location; /* temporary pointer, overloaded */ __u32 tsval, tsecr; /* need to include OPTION_TS */ struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ struct mptcp_out_options mptcp; +#ifdef CONFIG_TCP_AUTHOPT + struct tcp_authopt_info *authopt_info; + struct tcp_authopt_key_info *authopt_key; +#endif };

static void mptcp_options_write(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp, struct tcp_out_options *opts) @@ -616,10 +624,25 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, /* overload cookie hash location */ opts->hash_location = (__u8 *)ptr; ptr += 4; }

+#ifdef CONFIG_TCP_AUTHOPT + if (unlikely(OPTION_AUTHOPT & options)) { + struct tcp_authopt_key_info *key = opts->authopt_key; + + WARN_ON(!key); + *ptr = htonl((TCPOPT_AUTHOPT << 24) | + (TCPOLEN_AUTHOPT_OUTPUT << 16) | + (key->send_id << 8) | + opts->authopt_rnextkeyid); + /* overload cookie hash location */ + opts->hash_location = (__u8 *)(ptr + 1); + ptr += TCPOLEN_AUTHOPT_OUTPUT / 4; + } +#endif + if (unlikely(opts->mss)) { *ptr++ = htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | opts->mss); } @@ -751,10 +774,28 @@ static void mptcp_set_option_cond(const struct request_sock *req, } } } }

+static int tcp_authopt_init_options(const struct sock *sk, + const struct sock *addr_sk, + struct tcp_out_options *opts) +{ +#ifdef CONFIG_TCP_AUTHOPT + struct tcp_authopt_key_info *key; + + key = tcp_authopt_select_key(sk, addr_sk, &opts->authopt_info, &opts->authopt_rnextkeyid); + if (key) { + opts->options |= OPTION_AUTHOPT; + opts->authopt_key = key; + return TCPOLEN_AUTHOPT_OUTPUT; + } +#endif + + return 0; +} + /* Compute TCP options for SYN packets. This is not the final * network wire format yet. */ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, struct tcp_out_options *opts, @@ -763,12 +804,15 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, struct tcp_sock *tp = tcp_sk(sk); unsigned int remaining = MAX_TCP_OPTION_SPACE; struct tcp_fastopen_request *fastopen = tp->fastopen_req;

*md5 = NULL; + + remaining -= tcp_authopt_init_options(sk, sk, opts); #ifdef CONFIG_TCP_MD5SIG if (static_branch_unlikely(&tcp_md5_needed) && + !(opts->options & OPTION_AUTHOPT) && rcu_access_pointer(tp->md5sig_info)) { *md5 = tp->af_specific->md5_lookup(sk, sk); if (*md5) { opts->options |= OPTION_MD5; remaining -= TCPOLEN_MD5SIG_ALIGNED; @@ -847,12 +891,13 @@ static unsigned int tcp_synack_options(const struct sock *sk, struct sk_buff *syn_skb) { struct inet_request_sock *ireq = inet_rsk(req); unsigned int remaining = MAX_TCP_OPTION_SPACE;

+ remaining -= tcp_authopt_init_options(sk, req_to_sk(req), opts); #ifdef CONFIG_TCP_MD5SIG - if (md5) { + if (md5 && !(opts->options & OPTION_AUTHOPT)) { opts->options |= OPTION_MD5; remaining -= TCPOLEN_MD5SIG_ALIGNED;

/* We can't fit any SACK blocks in a packet with MD5 + TS * options. There was discussion about disabling SACK @@ -918,13 +963,15 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb unsigned int size = 0; unsigned int eff_sacks;

opts->options = 0;

+ size += tcp_authopt_init_options(sk, sk, opts); *md5 = NULL; #ifdef CONFIG_TCP_MD5SIG if (static_branch_unlikely(&tcp_md5_needed) && + !(opts->options & OPTION_AUTHOPT) && rcu_access_pointer(tp->md5sig_info)) { *md5 = tp->af_specific->md5_lookup(sk, sk); if (*md5) { opts->options |= OPTION_MD5; size += TCPOLEN_MD5SIG_ALIGNED; @@ -1274,10 +1321,14 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,

inet = inet_sk(sk); tcb = TCP_SKB_CB(skb); memset(&opts, 0, sizeof(opts));

+#ifdef CONFIG_TCP_AUTHOPT + /* for tcp_authopt_init_options inside tcp_syn_options or tcp_established_options */ + rcu_read_lock(); +#endif if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); } else { tcp_options_size = tcp_established_options(sk, skb, &opts, &md5); @@ -1362,10 +1413,17 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, sk_gso_disable(sk); tp->af_specific->calc_md5_hash(opts.hash_location, md5, sk, skb); } #endif +#ifdef CONFIG_TCP_AUTHOPT + if (opts.authopt_key) { + sk_gso_disable(sk); + tcp_authopt_hash(opts.hash_location, opts.authopt_key, opts.authopt_info, sk, skb); + } + rcu_read_unlock(); +#endif

/* BPF prog is the last one writing header option */ bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);

INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check, @@ -1832,12 +1890,21 @@ unsigned int tcp_current_mss(struct sock *sk) u32 mtu = dst_mtu(dst); if (mtu != inet_csk(sk)->icsk_pmtu_cookie) mss_now = tcp_sync_mss(sk, mtu); }

+#ifdef CONFIG_TCP_AUTHOPT + /* Even if the result is not used rcu_read_lock is required when scanning for + * tcp authentication keys. Otherwise lockdep will complain. + */ + rcu_read_lock(); +#endif header_len = tcp_established_options(sk, NULL, &opts, &md5) + sizeof(struct tcphdr); +#ifdef CONFIG_TCP_AUTHOPT + rcu_read_unlock(); +#endif /* The mss_cache is sized based on tp->tcp_header_len, which assumes * some common options. If this is an odd packet (because we have SACK * blocks etc) then our calculated header_len will be different, and * we have to adjust mss_now correspondingly */ if (header_len != tp->tcp_header_len) { @@ -3573,10 +3640,14 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, }

#ifdef CONFIG_TCP_MD5SIG rcu_read_lock(); md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); +#endif +#ifdef CONFIG_TCP_AUTHOPT + /* for tcp_authopt_init_options inside tcp_synack_options */ + rcu_read_lock(); #endif skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4); /* bpf program will be interested in the tcp_flags */ TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK; tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, @@ -3610,10 +3681,20 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, if (md5) tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, md5, req_to_sk(req), skb); rcu_read_unlock(); #endif +#ifdef CONFIG_TCP_AUTHOPT + /* If signature fails we do nothing */ + if (opts.authopt_key) + tcp_authopt_hash(opts.hash_location, + opts.authopt_key, + opts.authopt_info, + req_to_sk(req), + skb); + rcu_read_unlock(); +#endif

bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb, synack_type, &opts);

skb_set_delivery_time(skb, now, true);

Add a compute_sne function which finds the value of SNE for a certain SEQ given an already known "recent" SNE/SEQ. This is implemented using the standard tcp before/after macro and will work for SEQ values that are without 2^31 of the SEQ for which we know the SNE.

For updating we advance the value for rcv_sne at the same time as rcv_nxt and for snd_sne at the same time as snd_nxt. We could track other values (for example snd_una) but this is good enough and works very easily for timewait socket.

This implementation is different from RFC suggestions and doesn't require additional flags. It does pass tests from this draft: https://datatracker.ietf.org/doc/draft-touch-sne/

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/net/tcp_authopt.h | 34 ++++++++++++++ net/ipv4/tcp_authopt.c | 98 ++++++++++++++++++++++++++++++++++++++- net/ipv4/tcp_input.c | 1 + net/ipv4/tcp_output.c | 1 + 4 files changed, 132 insertions(+), 2 deletions(-)

diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index 1f5020b790dd..1fa1b968c80c 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -66,10 +66,14 @@ struct tcp_authopt_info { u32 flags; /** @src_isn: Local Initial Sequence Number */ u32 src_isn; /** @dst_isn: Remote Initial Sequence Number */ u32 dst_isn; + /** @rcv_sne: Recv-side Sequence Number Extension tracking tcp_sock.rcv_nxt */ + u32 rcv_sne; + /** @snd_sne: Send-side Sequence Number Extension tracking tcp_sock.snd_nxt */ + u32 snd_sne; };

/* TCP authopt as found in header */ struct tcphdr_authopt { u8 num; @@ -156,10 +160,34 @@ static inline void tcp_authopt_time_wait( int __tcp_authopt_inbound_check( struct sock *sk, struct sk_buff *skb, struct tcp_authopt_info *info, const u8 *opt); +void __tcp_authopt_update_rcv_sne(struct tcp_sock *tp, struct tcp_authopt_info *info, u32 seq); +static inline void tcp_authopt_update_rcv_sne(struct tcp_sock *tp, u32 seq) +{ + struct tcp_authopt_info *info; + + if (tcp_authopt_needed) { + info = rcu_dereference_protected(tp->authopt_info, + lockdep_sock_is_held((struct sock *)tp)); + if (info) + __tcp_authopt_update_rcv_sne(tp, info, seq); + } +} +void __tcp_authopt_update_snd_sne(struct tcp_sock *tp, struct tcp_authopt_info *info, u32 seq); +static inline void tcp_authopt_update_snd_sne(struct tcp_sock *tp, u32 seq) +{ + struct tcp_authopt_info *info; + + if (tcp_authopt_needed) { + info = rcu_dereference_protected(tp->authopt_info, + lockdep_sock_is_held((struct sock *)tp)); + if (info) + __tcp_authopt_update_snd_sne(tp, info, seq); + } +} #else static inline void tcp_authopt_clear(struct sock *sk) { } static inline int tcp_authopt_openreq(struct sock *newsk, @@ -174,8 +202,14 @@ static inline void tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *s static inline void tcp_authopt_time_wait( struct tcp_timewait_sock *tcptw, struct tcp_sock *tp) { } +static inline void tcp_authopt_update_rcv_sne(struct tcp_sock *tp, u32 seq) +{ +} +static inline void tcp_authopt_update_snd_sne(struct tcp_sock *tp, u32 seq) +{ +} #endif

#endif /* _LINUX_TCP_AUTHOPT_H */ diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 9d02da8d6964..1c2039a48bf6 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -656,10 +656,97 @@ static int tcp_authopt_get_isn(struct sock *sk, *disn = htonl(info->dst_isn); } return 0; }

+/* compute_sne - Calculate Sequence Number Extension + * + * Give old upper/lower 32bit values and a new lower 32bit value determine the + * new value of the upper 32 bit. The new sequence number can be 2^31 before or + * after prev_seq but TCP window scaling should limit this further. + * + * For correct accounting the stored SNE value should be only updated together + * with the SEQ. + */ +static u32 compute_sne(u32 sne, u32 prev_seq, u32 seq) +{ + if (before(seq, prev_seq)) { + if (seq > prev_seq) + --sne; + } else { + if (seq < prev_seq) + ++sne; + } + + return sne; +} + +/* Update rcv_sne, must be called immediately before rcv_nxt update */ +void __tcp_authopt_update_rcv_sne(struct tcp_sock *tp, + struct tcp_authopt_info *info, u32 seq) +{ + info->rcv_sne = compute_sne(info->rcv_sne, tp->rcv_nxt, seq); +} + +/* Update snd_sne, must be called immediately before snd_nxt update */ +void __tcp_authopt_update_snd_sne(struct tcp_sock *tp, + struct tcp_authopt_info *info, u32 seq) +{ + info->snd_sne = compute_sne(info->snd_sne, tp->snd_nxt, seq); +} + +/* Compute SNE for a specific packet (by seq). */ +static int compute_packet_sne(struct sock *sk, struct tcp_authopt_info *info, + u32 seq, bool input, __be32 *sne) +{ + u32 rcv_nxt, snd_nxt; + + // For TCP_NEW_SYN_RECV we have no tcp_authopt_info but tcp_request_sock holds ISN. + if (sk->sk_state == TCP_NEW_SYN_RECV) { + struct tcp_request_sock *rsk = tcp_rsk((struct request_sock *)sk); + + if (input) + *sne = htonl(compute_sne(0, rsk->rcv_isn, seq)); + else + *sne = htonl(compute_sne(0, rsk->snt_isn, seq)); + return 0; + } + + /* TCP_LISTEN only receives SYN */ + if (sk->sk_state == TCP_LISTEN && input) + return 0; + + /* TCP_SYN_SENT only sends SYN and receives SYN/ACK + * For the input case rcv_nxt is initialized after the packet is + * validated so tcp_sk(sk)->rcv_nxt is not initialized. + */ + if (sk->sk_state == TCP_SYN_SENT) + return 0; + + if (sk->sk_state == TCP_TIME_WAIT) { + rcv_nxt = tcp_twsk(sk)->tw_rcv_nxt; + snd_nxt = tcp_twsk(sk)->tw_snd_nxt; + } else { + if (WARN_ONCE(!sk_fullsock(sk), + "unexpected minisock sk=%p state=%d", sk, + sk->sk_state)) + return -EINVAL; + rcv_nxt = tcp_sk(sk)->rcv_nxt; + snd_nxt = tcp_sk(sk)->snd_nxt; + } + + if (WARN_ONCE(!info, "unexpected missing info for sk=%p sk_state=%d", sk, sk->sk_state)) + return -EINVAL; + + if (input) + *sne = htonl(compute_sne(info->rcv_sne, rcv_nxt, seq)); + else + *sne = htonl(compute_sne(info->snd_sne, snd_nxt, seq)); + + return 0; +} + /* Feed one buffer into ahash * The buffer is assumed to be DMA-able */ static int crypto_ahash_buf(struct ahash_request *req, u8 *buf, uint len) { @@ -691,10 +778,13 @@ int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct r if (!new_info) return -ENOMEM;

new_info->src_isn = tcp_rsk(req)->snt_isn; new_info->dst_isn = tcp_rsk(req)->rcv_isn; + /* Caller is tcp_create_openreq_child and already initializes snd_nxt/rcv_nxt */ + new_info->snd_sne = compute_sne(0, new_info->src_isn, tcp_sk(newsk)->snd_nxt); + new_info->rcv_sne = compute_sne(0, new_info->dst_isn, tcp_sk(newsk)->rcv_nxt); sk_gso_disable(newsk); rcu_assign_pointer(tcp_sk(newsk)->authopt_info, new_info);

return 0; } @@ -702,10 +792,12 @@ int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct r void __tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb, struct tcp_authopt_info *info) { info->src_isn = ntohl(tcp_hdr(skb)->ack_seq) - 1; info->dst_isn = ntohl(tcp_hdr(skb)->seq); + info->snd_sne = compute_sne(0, info->src_isn, tcp_sk(sk)->snd_nxt); + info->rcv_sne = compute_sne(0, info->dst_isn, tcp_sk(sk)->rcv_nxt); }

/* feed traffic key into ahash */ static int tcp_authopt_ahash_traffic_key(struct tcp_authopt_alg_pool *pool, struct sock *sk, @@ -959,14 +1051,16 @@ static int tcp_authopt_hash_packet(struct tcp_authopt_alg_pool *pool, bool ipv6, bool include_options, u8 *macbuf) { struct tcphdr *th = tcp_hdr(skb); + __be32 sne = 0; int err;

- /* NOTE: SNE unimplemented */ - __be32 sne = 0; + err = compute_packet_sne(sk, info, ntohl(th->seq), input, &sne); + if (err) + return err;

err = crypto_ahash_init(pool->req); if (err) return err;

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 9f065469562d..4da39c32b934 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3527,10 +3527,11 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack) static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq) { u32 delta = seq - tp->rcv_nxt;

sock_owned_by_me((struct sock *)tp); + tcp_authopt_update_rcv_sne(tp, seq); tp->bytes_received += delta; WRITE_ONCE(tp->rcv_nxt, seq); }

/* Update our send window. diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index da683f7951eb..d48d5dc36916 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -67,10 +67,11 @@ static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); unsigned int prior_packets = tp->packets_out;

+ tcp_authopt_update_snd_sne(tp, TCP_SKB_CB(skb)->end_seq); WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq);

__skb_unlink(skb, &sk->sk_write_queue); tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);

This is required because tcp ipv4 sometimes sends replies without allocating a full skb that can be signed by tcp authopt.

Handle this with additional code in tcp authopt.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/net/tcp_authopt.h | 7 ++ net/ipv4/tcp_authopt.c | 144 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 151 insertions(+)

diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index 1fa1b968c80c..9bc0f58a78cb 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -114,10 +114,17 @@ static inline struct tcp_authopt_key_info *tcp_authopt_select_key( int tcp_authopt_hash( char *hash_location, struct tcp_authopt_key_info *key, struct tcp_authopt_info *info, struct sock *sk, struct sk_buff *skb); +int tcp_v4_authopt_hash_reply( + char *hash_location, + struct tcp_authopt_info *info, + struct tcp_authopt_key_info *key, + __be32 saddr, + __be32 daddr, + struct tcphdr *th); int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req); static inline int tcp_authopt_openreq( struct sock *newsk, const struct sock *oldsk, struct request_sock *req) diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index bb74ab96b18f..0260173cd546 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -940,10 +940,72 @@ static int tcp_authopt_get_traffic_key(struct sock *sk, out: tcp_authopt_put_kdf_pool(key, pool); return err; }

+struct tcp_v4_authopt_context_data { + __be32 saddr; + __be32 daddr; + __be16 sport; + __be16 dport; + __be32 sisn; + __be32 disn; + __be16 digestbits; +} __packed; + +static int tcp_v4_authopt_get_traffic_key_noskb(struct tcp_authopt_key_info *key, + __be32 saddr, + __be32 daddr, + __be16 sport, + __be16 dport, + __be32 sisn, + __be32 disn, + u8 *traffic_key) +{ + int err; + struct tcp_authopt_alg_pool *pool; + struct tcp_v4_authopt_context_data data; + + BUILD_BUG_ON(sizeof(data) != 22); + + pool = tcp_authopt_get_kdf_pool(key); + if (IS_ERR(pool)) + return PTR_ERR(pool); + + err = tcp_authopt_setkey(pool, key); + if (err) + goto out; + err = crypto_ahash_init(pool->req); + if (err) + goto out; + + // RFC5926 section 3.1.1.1 + // Separate to keep alignment semi-sane + err = crypto_ahash_buf(pool->req, "\x01TCP-AO", 7); + if (err) + return err; + data.saddr = saddr; + data.daddr = daddr; + data.sport = sport; + data.dport = dport; + data.sisn = sisn; + data.disn = disn; + data.digestbits = htons(crypto_ahash_digestsize(pool->tfm) * 8); + + err = crypto_ahash_buf(pool->req, (u8 *)&data, sizeof(data)); + if (err) + goto out; + ahash_request_set_crypt(pool->req, NULL, traffic_key, 0); + err = crypto_ahash_final(pool->req); + if (err) + goto out; + +out: + tcp_authopt_put_kdf_pool(key, pool); + return err; +} + static int crypto_ahash_buf_zero(struct ahash_request *req, int len) { u8 zeros[TCP_AUTHOPT_MACLEN] = {0}; int buflen, err;

@@ -1210,10 +1272,92 @@ int tcp_authopt_hash(char *hash_location, return err; } EXPORT_SYMBOL(tcp_authopt_hash);

/** + * tcp_v4_authopt_hash_reply - Hash tcp+ipv4 header without SKB + * + * @hash_location: output buffer + * @info: sending socket's tcp_authopt_info + * @key: signing key, from tcp_authopt_select_key. + * @saddr: source address + * @daddr: destination address + * @th: Pointer to TCP header and options + */ +int tcp_v4_authopt_hash_reply(char *hash_location, + struct tcp_authopt_info *info, + struct tcp_authopt_key_info *key, + __be32 saddr, + __be32 daddr, + struct tcphdr *th) +{ + struct tcp_authopt_alg_pool *pool; + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; + u8 traffic_key[TCP_AUTHOPT_MAX_TRAFFIC_KEY_LEN]; + __be32 sne = 0; + int err; + + /* Call special code path for computing traffic key without skb + * This can be called from tcp_v4_reqsk_send_ack so caching would be + * difficult here. + */ + err = tcp_v4_authopt_get_traffic_key_noskb(key, saddr, daddr, + th->source, th->dest, + htonl(info->src_isn), htonl(info->dst_isn), + traffic_key); + if (err) + goto out_err_traffic_key; + + /* Init mac shash */ + pool = tcp_authopt_get_mac_pool(key); + if (IS_ERR(pool)) + return PTR_ERR(pool); + err = crypto_ahash_setkey(pool->tfm, traffic_key, key->alg->traffic_key_len); + if (err) + goto out_err; + err = crypto_ahash_init(pool->req); + if (err) + return err; + + err = crypto_ahash_buf(pool->req, (u8 *)&sne, 4); + if (err) + return err; + + err = tcp_authopt_hash_tcp4_pseudoheader(pool, saddr, daddr, th->doff * 4); + if (err) + return err; + + // TCP header with checksum set to zero. Caller ensures this. + if (WARN_ON_ONCE(th->check != 0)) + goto out_err; + err = crypto_ahash_buf(pool->req, (u8 *)th, sizeof(*th)); + if (err) + goto out_err; + + // TCP options + err = tcp_authopt_hash_opts(pool, th, (struct tcphdr_authopt *)(hash_location - 4), + !(key->flags & TCP_AUTHOPT_KEY_EXCLUDE_OPTS)); + if (err) + goto out_err; + + ahash_request_set_crypt(pool->req, NULL, macbuf, 0); + err = crypto_ahash_final(pool->req); + if (err) + goto out_err; + memcpy(hash_location, macbuf, TCP_AUTHOPT_MACLEN); + + tcp_authopt_put_mac_pool(key, pool); + return 0; + +out_err: + tcp_authopt_put_mac_pool(key, pool); +out_err_traffic_key: + memset(hash_location, 0, TCP_AUTHOPT_MACLEN); + return err; +} + +/* * tcp_authopt_lookup_recv - lookup key for receive * * @sk: Receive socket * @skb: Packet, used to compare addr and iface * @net: Per-namespace information containing keys

Add flags to allow marking individual keys and invalid for send or recv. Making keys assymetric this way is not mentioned in RFC5925 but RFC8177 requires that keys inside a keychain have independent "accept" and "send" lifetimes.

Flag names are negative so that the default behavior is for keys to be valid for both send and recv.

Setting both NOSEND and NORECV for a certain peer address can be used on a listen socket can be used to mean "TCP-AO is required from this peer but no keys are currently valid".

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/uapi/linux/tcp.h | 4 ++++ net/ipv4/tcp_authopt.c | 9 ++++++++- 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 76d7be6b27f4..75107a7fd935 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -369,15 +369,19 @@ struct tcp_authopt { * enum tcp_authopt_key_flag - flags for `tcp_authopt.flags` * * @TCP_AUTHOPT_KEY_DEL: Delete the key and ignore non-id fields * @TCP_AUTHOPT_KEY_EXCLUDE_OPTS: Exclude TCP options from signature * @TCP_AUTHOPT_KEY_ADDR_BIND: Key only valid for `tcp_authopt.addr` + * @TCP_AUTHOPT_KEY_NOSEND: Key invalid for send (expired) + * @TCP_AUTHOPT_KEY_NORECV: Key invalid for recv (expired) */ enum tcp_authopt_key_flag { TCP_AUTHOPT_KEY_DEL = (1 << 0), TCP_AUTHOPT_KEY_EXCLUDE_OPTS = (1 << 1), TCP_AUTHOPT_KEY_ADDR_BIND = (1 << 2), + TCP_AUTHOPT_KEY_NOSEND = (1 << 4), + TCP_AUTHOPT_KEY_NORECV = (1 << 5), };

/** * enum tcp_authopt_alg - Algorithms for TCP Authentication Option */ diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 0672a3bf5686..4dc2fe541498 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -353,10 +353,12 @@ static struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct netns_tcp_aut

hlist_for_each_entry_rcu(key, &net->head, node, 0) { if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) if (!tcp_authopt_key_match_sk_addr(key, addr_sk)) continue; + if (key->flags & TCP_AUTHOPT_KEY_NOSEND) + continue; if (result && net_ratelimit()) pr_warn("ambiguous tcp authentication keys configured for send\n"); result = key; }

@@ -504,11 +506,13 @@ int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) }

#define TCP_AUTHOPT_KEY_KNOWN_FLAGS ( \ TCP_AUTHOPT_KEY_DEL | \ TCP_AUTHOPT_KEY_EXCLUDE_OPTS | \ - TCP_AUTHOPT_KEY_ADDR_BIND) + TCP_AUTHOPT_KEY_ADDR_BIND | \ + TCP_AUTHOPT_KEY_NOSEND | \ + TCP_AUTHOPT_KEY_NORECV)

int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) { struct tcp_authopt_key opt; struct tcp_authopt_info *info; @@ -1383,10 +1387,13 @@ static struct tcp_authopt_key_info *tcp_authopt_lookup_recv(struct sock *sk, hlist_for_each_entry_rcu(key, &net->head, node, 0) { if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND && !tcp_authopt_key_match_skb_addr(key, skb)) continue; *anykey = true; + // If only keys with norecv flag are present still consider that + if (key->flags & TCP_AUTHOPT_KEY_NORECV) + continue; if (recv_id >= 0 && key->recv_id != recv_id) continue; if (!result) result = key; else if (result)

This allows making a key apply to an addr/prefix instead of just the full addr. This is enabled through a custom flag, default behavior is still full address match.

This is equivalent to TCP_MD5SIG_FLAG_PREFIX from TCP_MD5SIG and has the same use-cases.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- Documentation/networking/tcp_authopt.rst | 1 + include/net/tcp_authopt.h | 2 + include/uapi/linux/tcp.h | 10 ++++ net/ipv4/tcp_authopt.c | 63 ++++++++++++++++++++++-- 4 files changed, 72 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/tcp_authopt.rst b/Documentation/networking/tcp_authopt.rst index cbdea65e2b5d..d0191d0c6c02 100644 --- a/Documentation/networking/tcp_authopt.rst +++ b/Documentation/networking/tcp_authopt.rst @@ -38,10 +38,11 @@ new flags.

* Address binding is optional, by default keys match all addresses * Local address is ignored, matching is done by remote address * Ports are ignored * It is possible to match a specific VRF by l3index (default is to ignore) + * It is possible to match with a fixed prefixlen (default is full address)

RFC5925 requires that key ids do not overlap when tcp identifiers (addr/port) overlap. This is not enforced by linux, configuring ambiguous keys will result in packet drops and lost connections.

diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index e450f7c30043..6260c3ef6864 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -47,10 +47,12 @@ struct tcp_authopt_key_info { u8 keylen; /** @key: Same as &tcp_authopt_key.key */ u8 key[TCP_AUTHOPT_MAXKEYLEN]; /** @l3index: Same as &tcp_authopt_key.ifindex */ int l3index; + /** @prefixlen: Length of addr match (default full) */ + int prefixlen; /** @addr: Same as &tcp_authopt_key.addr */ struct sockaddr_storage addr; /** @alg: Algorithm implementation matching alg_id */ struct tcp_authopt_alg_imp *alg; }; diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 28be52f4e411..274ddfefd6de 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -372,18 +372,21 @@ struct tcp_authopt { * @TCP_AUTHOPT_KEY_EXCLUDE_OPTS: Exclude TCP options from signature * @TCP_AUTHOPT_KEY_ADDR_BIND: Key only valid for `tcp_authopt.addr` * @TCP_AUTHOPT_KEY_IFINDEX: Key only valid for `tcp_authopt.ifindex` * @TCP_AUTHOPT_KEY_NOSEND: Key invalid for send (expired) * @TCP_AUTHOPT_KEY_NORECV: Key invalid for recv (expired) + * @TCP_AUTHOPT_KEY_PREFIXLEN: Valid value in `tcp_authopt.prefixlen`, otherwise + * match full address length */ enum tcp_authopt_key_flag { TCP_AUTHOPT_KEY_DEL = (1 << 0), TCP_AUTHOPT_KEY_EXCLUDE_OPTS = (1 << 1), TCP_AUTHOPT_KEY_ADDR_BIND = (1 << 2), TCP_AUTHOPT_KEY_IFINDEX = (1 << 3), TCP_AUTHOPT_KEY_NOSEND = (1 << 4), TCP_AUTHOPT_KEY_NORECV = (1 << 5), + TCP_AUTHOPT_KEY_PREFIXLEN = (1 << 6), };

/** * enum tcp_authopt_alg - Algorithms for TCP Authentication Option */ @@ -434,10 +437,17 @@ struct tcp_authopt_key { * connections through this interface. Interface must be an vrf master. * * This is similar to `tcp_msg5sig.tcpm_ifindex` */ int ifindex; + /** + * @prefixlen: length of prefix to match + * + * Without the TCP_AUTHOPT_KEY_PREFIXLEN flag this is ignored and a full + * address match is performed. + */ + int prefixlen; };

/* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */

#define TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT 0x1 diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 3704af8202eb..daeecb64c89e 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -4,10 +4,11 @@ #include <net/ip.h> #include <net/ipv6.h> #include <net/tcp.h> #include <linux/kref.h> #include <crypto/hash.h> +#include <linux/inetdevice.h>

/* This is mainly intended to protect against local privilege escalations through * a rarely used feature so it is deliberately not namespaced. */ int sysctl_tcp_authopt; @@ -269,10 +270,14 @@ static bool tcp_authopt_key_match_exact(struct tcp_authopt_key_info *info, return false; if ((info->flags & TCP_AUTHOPT_KEY_IFINDEX) != (key->flags & TCP_AUTHOPT_KEY_IFINDEX)) return false; if ((info->flags & TCP_AUTHOPT_KEY_IFINDEX) && info->l3index != key->ifindex) return false; + if ((info->flags & TCP_AUTHOPT_KEY_PREFIXLEN) != (key->flags & TCP_AUTHOPT_KEY_PREFIXLEN)) + return false; + if ((info->flags & TCP_AUTHOPT_KEY_PREFIXLEN) && info->prefixlen != key->prefixlen) + return false; if ((info->flags & TCP_AUTHOPT_KEY_ADDR_BIND) != (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND)) return false; if (info->flags & TCP_AUTHOPT_KEY_ADDR_BIND) if (!ipvx_addr_match(&info->addr, &key->addr)) return false; @@ -286,17 +291,20 @@ static bool tcp_authopt_key_match_skb_addr(struct tcp_authopt_key_info *key, u16 keyaf = key->addr.ss_family; struct iphdr *iph = (struct iphdr *)skb_network_header(skb);

if (keyaf == AF_INET && iph->version == 4) { struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; + __be32 mask = inet_make_mask(key->prefixlen);

- return iph->saddr == key_addr->sin_addr.s_addr; + return (iph->saddr & mask) == key_addr->sin_addr.s_addr; } else if (keyaf == AF_INET6 && iph->version == 6) { struct ipv6hdr *ip6h = (struct ipv6hdr *)skb_network_header(skb); struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr;

- return ipv6_addr_equal(&ip6h->saddr, &key_addr->sin6_addr); + return ipv6_prefix_equal(&ip6h->saddr, + &key_addr->sin6_addr, + key->prefixlen); }

/* This actually happens with ipv6-mapped-ipv4-addresses * IPv6 listen sockets will be asked to validate ipv4 packets. */ @@ -312,17 +320,20 @@ static bool tcp_authopt_key_match_sk_addr(struct tcp_authopt_key_info *key, if (keyaf != addr_sk->sk_family) return false;

if (keyaf == AF_INET) { struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; + __be32 mask = inet_make_mask(key->prefixlen);

- return addr_sk->sk_daddr == key_addr->sin_addr.s_addr; + return (addr_sk->sk_daddr & mask) == key_addr->sin_addr.s_addr; #if IS_ENABLED(CONFIG_IPV6) } else if (keyaf == AF_INET6) { struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr;

- return ipv6_addr_equal(&addr_sk->sk_v6_daddr, &key_addr->sin6_addr); + return ipv6_prefix_equal(&addr_sk->sk_v6_daddr, + &key_addr->sin6_addr, + key->prefixlen); #endif }

return false; } @@ -348,10 +359,16 @@ static bool better_key_match(struct tcp_authopt_key_info *old, struct tcp_authop /* l3index always overrides non-l3index */ if (old->l3index && new->l3index == 0) return false; if (old->l3index == 0 && new->l3index) return true; + /* Full address match overrides match by prefixlen */ + if (!(new->flags & TCP_AUTHOPT_KEY_PREFIXLEN) && (old->flags & TCP_AUTHOPT_KEY_PREFIXLEN)) + return false; + /* Longer prefixes are better matches */ + if (new->prefixlen > old->prefixlen) + return true;

return false; }

/** @@ -536,21 +553,32 @@ int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) #define TCP_AUTHOPT_KEY_KNOWN_FLAGS ( \ TCP_AUTHOPT_KEY_DEL | \ TCP_AUTHOPT_KEY_EXCLUDE_OPTS | \ TCP_AUTHOPT_KEY_ADDR_BIND | \ TCP_AUTHOPT_KEY_IFINDEX | \ + TCP_AUTHOPT_KEY_PREFIXLEN | \ TCP_AUTHOPT_KEY_NOSEND | \ TCP_AUTHOPT_KEY_NORECV)

+static bool ipv6_addr_is_prefix(struct in6_addr *addr, int plen) +{ + struct in6_addr copy; + + ipv6_addr_prefix(&copy, addr, plen); + + return !memcmp(&copy, addr, sizeof(*addr)); +} + int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) { struct tcp_authopt_key opt; struct tcp_authopt_info *info; struct tcp_authopt_key_info *key_info, *old_key_info; struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); struct tcp_authopt_alg_imp *alg; int l3index = 0; + int prefixlen; int err;

sock_owned_by_me(sk); err = check_sysctl_tcp_authopt(); if (err) @@ -586,10 +614,36 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) if (opt.flags & TCP_AUTHOPT_KEY_ADDR_BIND) { if (sk->sk_family != opt.addr.ss_family) return -EINVAL; }

+ /* check prefixlen */ + if (opt.flags & TCP_AUTHOPT_KEY_PREFIXLEN) { + prefixlen = opt.prefixlen; + if (sk->sk_family == AF_INET) { + if (prefixlen < 0 || prefixlen > 32) + return -EINVAL; + if (((struct sockaddr_in *)&opt.addr)->sin_addr.s_addr & + ~inet_make_mask(prefixlen)) + return -EINVAL; + } + if (sk->sk_family == AF_INET6) { + if (prefixlen < 0 || prefixlen > 128) + return -EINVAL; + if (!ipv6_addr_is_prefix(&((struct sockaddr_in6 *)&opt.addr)->sin6_addr, + prefixlen)) + return -EINVAL; + } + } else { + if (sk->sk_family == AF_INET) + prefixlen = 32; + else if (sk->sk_family == AF_INET6) + prefixlen = 128; + else + return -EINVAL; + } + /* Initialize tcp_authopt_info if not already set */ info = __tcp_authopt_info_get_or_create(sk); if (IS_ERR(info)) return PTR_ERR(info);

@@ -635,10 +689,11 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) key_info->alg = alg; key_info->keylen = opt.keylen; memcpy(key_info->key, opt.key, opt.keylen); memcpy(&key_info->addr, &opt.addr, sizeof(key_info->addr)); key_info->l3index = l3index; + key_info->prefixlen = prefixlen; hlist_add_head_rcu(&key_info->node, &net->head); mutex_unlock(&net->mutex);

return 0; }

The RFC requires that TCP can report the keyid and rnextkeyid values being sent or received, implement this via getsockopt values.

The RFC also requires that user can select the sending key and that the sending key is automatically switched based on rnextkeyid. These requirements can conflict so we implement both and add a flag which specifies if user or peer request takes priority.

Also add an option to control rnextkeyid explicitly from userspace.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- Documentation/networking/tcp_authopt.rst | 32 +++++ include/net/tcp_authopt.h | 32 +++++ include/uapi/linux/tcp.h | 31 +++++ net/ipv4/tcp_authopt.c | 167 +++++++++++++++++++++-- 4 files changed, 254 insertions(+), 8 deletions(-)

diff --git a/Documentation/networking/tcp_authopt.rst b/Documentation/networking/tcp_authopt.rst index d0191d0c6c02..5631750cc3f7 100644 --- a/Documentation/networking/tcp_authopt.rst +++ b/Documentation/networking/tcp_authopt.rst @@ -44,10 +44,42 @@ new flags.

RFC5925 requires that key ids do not overlap when tcp identifiers (addr/port) overlap. This is not enforced by linux, configuring ambiguous keys will result in packet drops and lost connections.

+Key selection +------------- + +On getsockopt(TCP_AUTHOPT) information is provided about keyid/rnextkeyid in +the last send packet and about the keyid/rnextkeyd in the last valid received +packet. + +By default the sending keyid is selected to match the rnextkeyid value sent by +the remote side, visible as recv_rnextkeyid in getsockopt. If that keyid is not +available then the valid key with the longest send validity time is used, and +otherwise ties are broken by preferring lowest numeric send_id. + +If the ``TCP_AUTHOPT_LOCK_KEYID`` flag is set then the sending key is selected +by the `tcp_authopt.send_local_id` field and recv_rnextkeyid is ignored. If no +key with local_id == send_local_id is valid then the same default is used +as for missing recv_rnextkeyid. + +The rnextkeyid value sent on the wire is the recv_id of the valid key with the +longest recv validity time, and otherwise ties are broken by preferring lowest +numeric recv_id. + +If the TCP_AUTHOPT_LOCK_RNEXTKEY flag is set in `tcp_authopt.flags` the value of +`tcp_authopt.send_rnextkeyid` is sent instead. + +The default key selection behavior is designed to implement key rollover in a +way that is compatible with existing vendors without needing userspace key +management. It also tries to behave predictably in all scenarios therefore it +breaks ties by numeric IDs. + +A userspace daemon can use the "lock" flags to implement different key +management and key rotation policies. + ABI Reference =============

.. kernel-doc:: include/uapi/linux/tcp.h :identifiers: tcp_authopt tcp_authopt_flag tcp_authopt_key tcp_authopt_key_flag tcp_authopt_alg diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index 6ef893e75ee4..759b6d71fe86 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -83,10 +83,42 @@ struct tcp_authopt_info { u32 dst_isn; /** @rcv_sne: Recv-side Sequence Number Extension tracking tcp_sock.rcv_nxt */ u32 rcv_sne; /** @snd_sne: Send-side Sequence Number Extension tracking tcp_sock.snd_nxt */ u32 snd_sne; + + /** + * @send_keyid: keyid currently being sent + * + * This is controlled by userspace by userspace if + * TCP_AUTHOPT_FLAG_LOCK_KEYID, otherwise we try to match recv_rnextkeyid. + * + * This is the "currently effective" value from the last packet. + */ + u8 send_keyid; + /** + * @user_pref_send_keyid: Preferred keyid requested by userspace + */ + u8 user_pref_send_keyid; + /** + * @send_rnextkeyid: rnextkeyid currently being sent + * + * This is controlled by userspace if TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID is set + */ + u8 send_rnextkeyid; + /** + * @recv_keyid: last keyid received from remote + * + * This is reported to userspace but has no other special behavior attached. + */ + u8 recv_keyid; + /** + * @recv_rnextkeyid: last rnextkeyid received from remote + * + * Linux tries to honor this unless TCP_AUTHOPT_FLAG_LOCK_KEYID is set + */ + u8 recv_rnextkeyid; };

/* TCP authopt as found in header */ struct tcphdr_authopt { u8 num; diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 52e6293048f5..4c3b1aef9976 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -346,10 +346,24 @@ struct tcp_diag_md5sig {

/** * enum tcp_authopt_flag - flags for `tcp_authopt.flags` */ enum tcp_authopt_flag { + /** + * @TCP_AUTHOPT_FLAG_LOCK_KEYID: keyid controlled by sockopt + * + * If this is set `tcp_authopt.send_keyid` is used to determined sending + * key. Otherwise a key with send_id == recv_rnextkeyid is preferred. + */ + TCP_AUTHOPT_FLAG_LOCK_KEYID = (1 << 0), + /** + * @TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID: Override rnextkeyid from userspace + * + * If this is set then `tcp_authopt.send_rnextkeyid` is sent on outbound + * packets. Other the recv_id of the current sending key is sent. + */ + TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID = (1 << 1), /** * @TCP_AUTHOPT_FLAG_REJECT_UNEXPECTED: * Configure behavior of segments with TCP-AO coming from hosts for which no * key is configured. The default recommended by RFC is to silently accept * such connections. @@ -361,10 +375,27 @@ enum tcp_authopt_flag { * struct tcp_authopt - Per-socket options related to TCP Authentication Option */ struct tcp_authopt { /** @flags: Combination of &enum tcp_authopt_flag */ __u32 flags; + /** + * @send_keyid: `tcp_authopt_key.send_id` of preferred send key + * + * This is only used if `TCP_AUTHOPT_FLAG_LOCK_KEYID` is set. + */ + __u8 send_keyid; + /** + * @send_rnextkeyid: The rnextkeyid to send in packets + * + * This is controlled by the user iff TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID is + * set. Otherwise rnextkeyid is the recv_id of the current key. + */ + __u8 send_rnextkeyid; + /** @recv_keyid: A recently-received keyid value. Only for getsockopt. */ + __u8 recv_keyid; + /** @recv_rnextkeyid: A recently-received rnextkeyid value. Only for getsockopt. */ + __u8 recv_rnextkeyid; };

/** * enum tcp_authopt_key_flag - flags for `tcp_authopt.flags` * diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 2bb7b2356e50..6db06e1edcc7 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -392,24 +392,85 @@ static bool better_key_match(struct tcp_authopt_key_info *old, struct tcp_authop return true;

return false; }

+static int better_key_match_for_send(struct tcp_authopt_key_info *old, + struct tcp_authopt_key_info *new) +{ + if (better_key_match(old, new)) + return 1; + + /* For keys with expiration dates prefer the one with longest lifetime */ + if ((new->flags & TCP_AUTHOPT_KEY_SEND_LIFETIME_END) != 0 && + (old->flags & TCP_AUTHOPT_KEY_SEND_LIFETIME_END) == 0) + return -1; + if ((new->flags & TCP_AUTHOPT_KEY_SEND_LIFETIME_END) == 0 && + (old->flags & TCP_AUTHOPT_KEY_SEND_LIFETIME_END) != 0) + return 1; + if (old->flags & TCP_AUTHOPT_KEY_SEND_LIFETIME_END && + new->flags & TCP_AUTHOPT_KEY_SEND_LIFETIME_END) { + if (new->send_lifetime_end > old->send_lifetime_end) + return 1; + if (new->send_lifetime_end < old->send_lifetime_end) + return -1; + } + + if (new->send_id != old->send_id) + return !!(old->send_id - new->send_id); + + return 0; +} + +static int better_rnextkey(struct tcp_authopt_key_info *old, struct tcp_authopt_key_info *new) +{ + if (better_key_match(old, new)) + return 1; + + /* For keys with expiration dates prefer the one with longest lifetime */ + if ((new->flags & TCP_AUTHOPT_KEY_RECV_LIFETIME_END) != 0 && + (old->flags & TCP_AUTHOPT_KEY_RECV_LIFETIME_END) == 0) + return -1; + if ((new->flags & TCP_AUTHOPT_KEY_RECV_LIFETIME_END) == 0 && + (old->flags & TCP_AUTHOPT_KEY_RECV_LIFETIME_END) != 0) + return 1; + if (old->flags & TCP_AUTHOPT_KEY_RECV_LIFETIME_END && + new->flags & TCP_AUTHOPT_KEY_RECV_LIFETIME_END) { + if (new->recv_lifetime_end > old->recv_lifetime_end) + return 1; + if (new->recv_lifetime_end < old->recv_lifetime_end) + return -1; + } + + /* Break ties by numeric ID */ + if (new->recv_id != old->recv_id) + return !!(old->recv_id - new->recv_id); + + return 0; +} + /** * tcp_authopt_lookup_send - lookup key for sending * * @net: Per-namespace information containing keys * @addr_sk: Socket used for destination address lookup + * @pref_send_id: Preferred send_id. If >= 0 then prefer keys that match + * @rnextkeyid: Output pointer to preferred rnextkeyid + * @anykey: Set to true if any keys are present for the peer * * If anykey is false then authentication is not required for peer. * * If anykey is true but no key was found then all our keys must be expired and sending should fail. */ static struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct netns_tcp_authopt *net, - const struct sock *addr_sk) + const struct sock *addr_sk, + int pref_send_id, + u8 *rnextkeyid, + bool *anykey) { struct tcp_authopt_key_info *result = NULL; + struct tcp_authopt_key_info *rnext_result = NULL; struct tcp_authopt_key_info *key; time64_t now = ktime_get_real_seconds(); int l3index = -1;

hlist_for_each_entry_rcu(key, &net->head, node, 0) { @@ -421,16 +482,35 @@ static struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct netns_tcp_aut l3index = l3mdev_master_ifindex_by_index(sock_net(addr_sk), addr_sk->sk_bound_dev_if); if (l3index != key->l3index) continue; } - if (!key_valid_for_send(key, now)) - continue; - if (better_key_match(result, key)) - result = key; - else if (result) - net_warn_ratelimited("ambiguous tcp authentication keys configured for send\n"); + if (anykey) + *anykey = true; + + if (rnextkeyid && + key_valid_for_recv(key, now) && + better_rnextkey(rnext_result, key) > 0) + rnext_result = key; + + if (key_valid_for_send(key, now)) { + if (pref_send_id >= 0 && result && + key->send_id != pref_send_id && + result->send_id == pref_send_id) + continue; + if (better_key_match_for_send(result, key) > 0) + result = key; + else if (result) + net_warn_ratelimited("ambiguous tcp authentication keys configured for send\n"); + } + } + + if (rnextkeyid) { + if (rnext_result) + *rnextkeyid = rnext_result->recv_id; + else + *rnextkeyid = 0; }

return result; }

@@ -442,19 +522,59 @@ static struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct netns_tcp_aut * @addr_sk: socket used for address lookup. Same as sk except for synack case * @rnextkeyid: value of rnextkeyid caller should write in packet * * Result is protected by RCU and can't be stored, it may only be passed to * tcp_authopt_hash and only under a single rcu_read_lock. + * + * Returns NULL if no key is required or ERR_PTR(-ENOKEY) if key is required but + * none is currently valid. */ struct tcp_authopt_key_info *__tcp_authopt_select_key(const struct sock *sk, struct tcp_authopt_info *info, const struct sock *addr_sk, u8 *rnextkeyid) { + struct tcp_authopt_key_info *key; struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); + bool anykey = false; + int pref_send_id; + + /* Listen sockets don't refer to any specific connection so we don't try + * to keep using the same key and ignore any received keyids. + */ + if (sk->sk_state == TCP_LISTEN) { + if (info->flags & TCP_AUTHOPT_FLAG_LOCK_KEYID) + pref_send_id = info->user_pref_send_keyid; + else + pref_send_id = -1; + key = tcp_authopt_lookup_send(net, addr_sk, pref_send_id, rnextkeyid, &anykey); + + return key; + } + + /* Try to keep the same sending key unless user or peer requires a different key + * User request (via TCP_AUTHOPT_FLAG_LOCK_KEYID) always overrides peer request. + */ + if (info->flags & TCP_AUTHOPT_FLAG_LOCK_KEYID) + pref_send_id = info->user_pref_send_keyid; + else + pref_send_id = info->recv_rnextkeyid;

- return tcp_authopt_lookup_send(net, addr_sk); + key = tcp_authopt_lookup_send(net, addr_sk, pref_send_id, rnextkeyid, &anykey); + + if (!key) + return NULL; + + info->send_keyid = key->send_id; + if (rnextkeyid) { + if (info->flags & TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID) + *rnextkeyid = info->send_rnextkeyid; + else + info->send_rnextkeyid = *rnextkeyid; + } + + return key; } EXPORT_SYMBOL(__tcp_authopt_select_key);

static struct tcp_authopt_info *__tcp_authopt_info_get_or_create(struct sock *sk) { @@ -476,10 +596,12 @@ static struct tcp_authopt_info *__tcp_authopt_info_get_or_create(struct sock *sk

return info; }

#define TCP_AUTHOPT_KNOWN_FLAGS ( \ + TCP_AUTHOPT_FLAG_LOCK_KEYID | \ + TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID | \ TCP_AUTHOPT_FLAG_REJECT_UNEXPECTED)

/* Like copy_from_sockptr except tolerate different optlen for compatibility reasons * * If the src is shorter then it's from an old userspace and the rest of dst is @@ -547,10 +669,14 @@ int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen) info = __tcp_authopt_info_get_or_create(sk); if (IS_ERR(info)) return PTR_ERR(info);

info->flags = opt.flags & TCP_AUTHOPT_KNOWN_FLAGS; + if (opt.flags & TCP_AUTHOPT_FLAG_LOCK_KEYID) + info->user_pref_send_keyid = opt.send_keyid; + if (opt.flags & TCP_AUTHOPT_FLAG_LOCK_RNEXTKEYID) + info->send_rnextkeyid = opt.send_rnextkeyid;

return 0; }

int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) @@ -568,10 +694,18 @@ int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk)); if (!info) return -ENOENT;

opt->flags = info->flags & TCP_AUTHOPT_KNOWN_FLAGS; + /* These keyids might be undefined, for example before connect. + * Reporting zero is not strictly correct because there are no reserved + * values. + */ + opt->send_keyid = info->send_keyid; + opt->send_rnextkeyid = info->send_rnextkeyid; + opt->recv_keyid = info->recv_keyid; + opt->recv_rnextkeyid = info->recv_rnextkeyid;

return 0; }

#define TCP_AUTHOPT_KEY_KNOWN_FLAGS ( \ @@ -1571,10 +1705,25 @@ static void print_tcpao_notice(const char *msg, struct sk_buff *skb) } else { WARN_ONCE(1, "%s unknown IP version\n", msg); } }

+static void save_inbound_key_info( + struct tcp_authopt_info *info, + struct tcphdr_authopt *opt) +{ + /* Doing this for all valid packets will results in keyids temporarily + * flipping back and forth if packets are reordered or retransmitted + * but keys should eventually stabilize. + * + * This is connection-specific so don't store for listen sockets. + * + */ + info->recv_keyid = opt->keyid; + info->recv_rnextkeyid = opt->rnextkeyid; +} + /** * __tcp_authopt_inbound_check - Check inbound TCP authentication option * * @sk: Receive socket. For the SYN_RECV state this must be the request_sock, not the listener * @skb: Input Packet @@ -1617,10 +1766,11 @@ int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); print_tcpao_notice("TCP Authentication Unexpected: Rejected", skb); return -SKB_DROP_REASON_TCP_AOUNEXPECTED; } print_tcpao_notice("TCP Authentication Unexpected: Accepted", skb); + save_inbound_key_info(info, opt); return 0; } if (opt && !key) { /* Keys are configured for peer but with different keyid than packet */ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); @@ -1640,10 +1790,11 @@ int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTHOPTFAILURE); print_tcpao_notice("TCP Authentication Failed", skb); return -SKB_DROP_REASON_TCP_AOFAILURE; }

+ save_inbound_key_info(info, opt); return 1; } EXPORT_SYMBOL(__tcp_authopt_inbound_check);

static int tcp_authopt_init_net(struct net *full_net)

This provides a very brief summary of all keys for debugging purposes.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- Documentation/networking/tcp_authopt.rst | 10 +++ net/ipv4/tcp_authopt.c | 102 ++++++++++++++++++++++- 2 files changed, 111 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/tcp_authopt.rst b/Documentation/networking/tcp_authopt.rst index 5631750cc3f7..2bceefe6fe1d 100644 --- a/Documentation/networking/tcp_authopt.rst +++ b/Documentation/networking/tcp_authopt.rst @@ -76,10 +76,20 @@ management. It also tries to behave predictably in all scenarios therefore it breaks ties by numeric IDs.

A userspace daemon can use the "lock" flags to implement different key management and key rotation policies.

+Proc interface +-------------- + +The ``/proc/net/tcp_authopt`` file contains a tab-separated table of keys. The +first line contains column names. The number of columns might increase in the +future if more matching criteria are added. Here is an example of the table:: + + flags send_id recv_id alg addr l3index + 0x44 0 0 1 10.10.2.2/31 0 + ABI Reference =============

.. kernel-doc:: include/uapi/linux/tcp.h :identifiers: tcp_authopt tcp_authopt_flag tcp_authopt_key tcp_authopt_key_flag tcp_authopt_alg diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 28c10a916fb3..ba16b8c50565 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -5,10 +5,11 @@ #include <net/ipv6.h> #include <net/tcp.h> #include <linux/kref.h> #include <crypto/hash.h> #include <linux/inetdevice.h> +#include <linux/proc_fs.h>

/* This is mainly intended to protect against local privilege escalations through * a rarely used feature so it is deliberately not namespaced. */ int sysctl_tcp_authopt; @@ -1810,26 +1811,125 @@ int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, save_inbound_key_info(info, opt); return 1; } EXPORT_SYMBOL(__tcp_authopt_inbound_check);

+#ifdef CONFIG_PROC_FS +struct tcp_authopt_iter_state { + struct seq_net_private p; +}; + +static struct tcp_authopt_key_info *tcp_authopt_get_key_index(struct netns_tcp_authopt *net, + int index) +{ + struct tcp_authopt_key_info *key; + + hlist_for_each_entry(key, &net->head, node) { + if (--index < 0) + return key; + } + + return NULL; +} + +static void *tcp_authopt_seq_start(struct seq_file *seq, loff_t *pos) + __acquires(RCU) +{ + struct netns_tcp_authopt *net = &seq_file_net(seq)->tcp_authopt; + + rcu_read_lock(); + if (*pos == 0) + return SEQ_START_TOKEN; + else + return tcp_authopt_get_key_index(net, *pos - 1); +} + +static void tcp_authopt_seq_stop(struct seq_file *seq, void *v) + __releases(RCU) +{ + rcu_read_unlock(); +} + +static void *tcp_authopt_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct netns_tcp_authopt *net = &seq_file_net(seq)->tcp_authopt; + void *ret; + + ret = tcp_authopt_get_key_index(net, *pos); + ++*pos; + + return ret; +} + +static int tcp_authopt_seq_show(struct seq_file *seq, void *v) +{ + struct tcp_authopt_key_info *key = v; + + /* FIXME: Document somewhere */ + /* Key is deliberately inaccessible */ + if (v == SEQ_START_TOKEN) { + seq_puts(seq, "flags\tsend_id\trecv_id\talg\taddr\tl3index\n"); + return 0; + } + + seq_printf(seq, "0x%x\t%d\t%d\t%d", + key->flags, key->send_id, key->recv_id, (int)key->alg_id); + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) { + if (key->addr.ss_family == AF_INET6) + seq_printf(seq, "\t%pI6", &((struct sockaddr_in6 *)&key->addr)->sin6_addr); + else + seq_printf(seq, "\t%pI4", &((struct sockaddr_in *)&key->addr)->sin_addr); + if (key->flags & TCP_AUTHOPT_KEY_PREFIXLEN) + seq_printf(seq, "/%d", key->prefixlen); + } else { + seq_puts(seq, "\t*"); + } + seq_printf(seq, "\t%d", key->l3index); + seq_puts(seq, "\n"); + + return 0; +} + +static const struct seq_operations tcp_authopt_seq_ops = { + .start = tcp_authopt_seq_start, + .next = tcp_authopt_seq_next, + .stop = tcp_authopt_seq_stop, + .show = tcp_authopt_seq_show, +}; +#endif /* CONFIG_PROC_FS */ + +static int __net_init tcp_authopt_proc_init_net(struct net *net) +{ + if (!proc_create_net("tcp_authopt", 0400, net->proc_net, + &tcp_authopt_seq_ops, + sizeof(struct tcp_authopt_iter_state))) + return -ENOMEM; + return 0; +} + +static void __net_exit tcp_authopt_proc_exit_net(struct net *net) +{ + remove_proc_entry("tcp_authopt", net->proc_net); +} + static int tcp_authopt_init_net(struct net *full_net) { struct netns_tcp_authopt *net = &full_net->tcp_authopt;

mutex_init(&net->mutex); INIT_HLIST_HEAD(&net->head);

- return 0; + return tcp_authopt_proc_init_net(full_net); }

static void tcp_authopt_exit_net(struct net *full_net) { struct netns_tcp_authopt *net = &full_net->tcp_authopt; struct tcp_authopt_key_info *key; struct hlist_node *n;

+ tcp_authopt_proc_exit_net(full_net); mutex_lock(&net->mutex);

hlist_for_each_entry_safe(key, n, &net->head, node) { hlist_del_rcu(&key->node); tcp_authopt_key_put(key);

According to the RFC we should use the key that the peer suggests via rnextkeyid.

This is currently done by storing recv_rnextkeyid in tcp_authopt_info but this does not work for the SYNACK case because the tcp_request_sock does not hold an info pointer for reasons of memory usage.

Handle this by storing recv_rnextkeyid inside tcp_request_sock. This doesn't increase the memory usage because there are unused bytes at the end.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/linux/tcp.h | 6 ++++++ net/ipv4/tcp_authopt.c | 14 +++++++++++--- net/ipv4/tcp_input.c | 12 ++++++++++++ 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 551942883f06..6a4ff0ed55c6 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -125,10 +125,13 @@ struct tcp_options_received { u8 saw_unknown:1, /* Received unknown option */ unused:7; u8 num_sacks; /* Number of SACK blocks */ u16 user_mss; /* mss requested by user in ioctl */ u16 mss_clamp; /* Maximal mss, negotiated at connection setup */ +#if IS_ENABLED(CONFIG_TCP_AUTHOPT) + u8 rnextkeyid; +#endif };

static inline void tcp_clear_options(struct tcp_options_received *rx_opt) { rx_opt->tstamp_ok = rx_opt->sack_ok = 0; @@ -163,10 +166,13 @@ struct tcp_request_sock { u32 rcv_nxt; /* the ack # by SYNACK. For * FastOpen it's the seq# * after data-in-SYN. */ u8 syn_tos; +#if IS_ENABLED(CONFIG_TCP_AUTHOPT) + u8 recv_rnextkeyid; +#endif };

static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req) { return (struct tcp_request_sock *)req; diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 2a1ddae69b27..a141439d9ebe 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -547,21 +547,29 @@ struct tcp_authopt_key_info *__tcp_authopt_select_key(const struct sock *sk, struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); bool anykey = false; int pref_send_id;

/* Listen sockets don't refer to any specific connection so we don't try - * to keep using the same key and ignore any received keyids. + * to keep using the same key. + * The rnextkeyid is stored in tcp_request_sock */ if (sk->sk_state == TCP_LISTEN) { + struct tcp_request_sock *rsk; + + if (WARN_ONCE(addr_sk->sk_state != TCP_NEW_SYN_RECV, "bad socket state")) + return NULL; + rsk = tcp_rsk((struct request_sock *)addr_sk); + /* Forcing a specific send_keyid on a listen socket forces it for + * all clients so is unlikely to be useful. + */ if (info->flags & TCP_AUTHOPT_FLAG_LOCK_KEYID) pref_send_id = info->user_pref_send_keyid; else - pref_send_id = -1; + pref_send_id = rsk->recv_rnextkeyid; key = tcp_authopt_lookup_send(net, addr_sk, pref_send_id, rnextkeyid, &anykey); if (!key && anykey) return ERR_PTR(-ENOKEY); - return key; }

/* Try to keep the same sending key unless user or peer requires a different key * User request (via TCP_AUTHOPT_FLAG_LOCK_KEYID) always overrides peer request. diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 4da39c32b934..6f477b110896 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4108,10 +4108,18 @@ void tcp_parse_options(const struct net *net, /* * The MD5 Hash has already been * checked (see tcp_v{4,6}_do_rcv()). */ break; +#endif +#ifdef CONFIG_TCP_AUTHOPT + case TCPOPT_AUTHOPT: + /* Hash has already been checked. + * We parse rnextkeyid here so we can match it on synack + */ + opt_rx->rnextkeyid = ptr[1]; + break; #endif case TCPOPT_FASTOPEN: tcp_parse_fastopen_option( opsize - TCPOLEN_FASTOPEN_BASE, ptr, th->syn, foc, false); @@ -6964,10 +6972,14 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, tcp_clear_options(&tmp_opt);

if (IS_ENABLED(CONFIG_SMC) && want_cookie) tmp_opt.smc_ok = 0;

+#if IS_ENABLED(CONFIG_TCP_AUTHOPT) + tcp_rsk(req)->recv_rnextkeyid = tmp_opt.rnextkeyid; +#endif + tmp_opt.tstamp_ok = tmp_opt.saw_tstamp; tcp_openreq_init(req, &tmp_opt, skb, sk); inet_rsk(req)->no_srccheck = inet_sk(sk)->transparent;

/* Note: tcp_v6_init_req() might override ir_iif for link locals */

In order to support TCP_REPAIR for connections using RFC5925 Authentication Option add a sockopt to get/set ISN and SNE values.

The TCP_REPAIR_AUTHOxpTP sockopt is only allowed when the socket is already in "repair" mode, this behavior is shared with other sockopts relevant to TCP_REPAIR.

The setsockopt further requires the TCP_ESTABLISHED state, this is because it relies on snd_nxt which is only initialized after connect().

For SNE restoration we provide a full 64-bit sequence number on "get" and handle any recent 64-bit sequence number on "set", where recent means "within ~2GB to the current window".

Linux tracks snd_sne and rcv_sne as the extension of snd_nxt and rcv_nxt but this is an implementation detail and snd_nxt doesn't even seem to be one of the values that can be read by userspace. Handling SNE with 64-bit values means userspace doesn't need to worry about matching snd_nxt.

Signed-off-by: Leonard Crestez cdleonard@gmail.com --- include/net/tcp_authopt.h | 2 ++ include/uapi/linux/tcp.h | 19 +++++++++++ net/ipv4/tcp.c | 23 ++++++++++++++ net/ipv4/tcp_authopt.c | 66 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 110 insertions(+)

diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index 759b6d71fe86..5a8cea32a5f3 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -236,10 +236,12 @@ static inline void tcp_authopt_update_snd_sne(struct tcp_sock *tp, u32 seq) lockdep_sock_is_held((struct sock *)tp)); if (info) __tcp_authopt_update_snd_sne(tp, info, seq); } } +int tcp_get_authopt_repair_val(struct sock *sk, struct tcp_authopt_repair *opt); +int tcp_set_authopt_repair(struct sock *sk, sockptr_t optval, unsigned int optlen); #else static inline void tcp_authopt_clear(struct sock *sk) { } static inline int tcp_authopt_openreq(struct sock *newsk, diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index ff8b53f4209d..d6911d9c2b4e 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -128,10 +128,11 @@ enum { #define TCP_CM_INQ TCP_INQ

#define TCP_TX_DELAY 37 /* delay outgoing packets by XX usec */ #define TCP_AUTHOPT 38 /* TCP Authentication Option (RFC5925) */ #define TCP_AUTHOPT_KEY 39 /* TCP Authentication Option Key (RFC5925) */ +#define TCP_REPAIR_AUTHOPT 40

#define TCP_REPAIR_ON 1 #define TCP_REPAIR_OFF 0 #define TCP_REPAIR_OFF_NO_WP -1 /* Turn off without window probes */ @@ -509,10 +510,28 @@ struct tcp_authopt_key { __u64 recv_lifetime_begin; /** @recv_lifetime_end: End of recv lifetime */ __u64 recv_lifetime_end; };

+/** + * struct tcp_authopt_repair - TCP_REPAIR information related to Authentication Option + * @src_isn: Local Initial Sequence Number + * @dst_isn: Remote Initial Sequence Number + * @snd_sne: Sequence Number Extension for Send (upper 32 bits of snd_seq) + * @rcv_sne: Sequence Number Extension for Recv (upper 32 bits of rcv_seq) + * @snd_seq: Recent Send Sequence Number (lower 32 bits of snd_sne) + * @rcv_seq: Recent Recv Sequence Number (lower 32 bits of rcv_sne) + */ +struct tcp_authopt_repair { + __u32 src_isn; + __u32 dst_isn; + __u32 snd_sne; + __u32 rcv_sne; + __u32 snd_seq; + __u32 rcv_seq; +}; + /* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */

#define TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT 0x1 struct tcp_zerocopy_receive { __u64 address; /* in: address of mapping */ diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index dd31e78bd22d..1e0dcfae23f5 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3712,10 +3712,13 @@ static int do_tcp_setsockopt(struct sock *sk, int level, int optname, err = tcp_set_authopt(sk, optval, optlen); break; case TCP_AUTHOPT_KEY: err = tcp_set_authopt_key(sk, optval, optlen); break; + case TCP_REPAIR_AUTHOPT: + err = tcp_set_authopt_repair(sk, optval, optlen); + break; #endif case TCP_USER_TIMEOUT: /* Cap the max time in ms TCP will retry or probe the window * before giving up and aborting (ETIMEDOUT) a connection. */ @@ -4384,10 +4387,30 @@ static int do_tcp_getsockopt(struct sock *sk, int level, return -EFAULT; if (copy_to_user(optval, &info, len)) return -EFAULT; return 0; } + case TCP_REPAIR_AUTHOPT: { + struct tcp_authopt_repair val; + int err; + + if (get_user(len, optlen)) + return -EFAULT; + + lock_sock(sk); + err = tcp_get_authopt_repair_val(sk, &val); + release_sock(sk); + + if (err) + return err; + len = min_t(unsigned int, len, sizeof(val)); + if (put_user(len, optlen)) + return -EFAULT; + if (copy_to_user(optval, &val, len)) + return -EFAULT; + return 0; + } #endif

default: return -ENOPROTOOPT; } diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index b4158b430b79..1c571a977224 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -1839,10 +1839,76 @@ int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, save_inbound_key_info(info, opt); return 1; } EXPORT_SYMBOL(__tcp_authopt_inbound_check);

+int tcp_get_authopt_repair_val(struct sock *sk, struct tcp_authopt_repair *opt) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_authopt_info *info; + int err; + + memset(opt, 0, sizeof(*opt)); + sock_owned_by_me(sk); + err = check_sysctl_tcp_authopt(); + if (err) + return err; + if (!tp->repair) + return -EPERM; + + info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk)); + if (!info) + return -ENOENT; + + opt->dst_isn = info->dst_isn; + opt->src_isn = info->src_isn; + opt->rcv_sne = info->rcv_sne; + opt->snd_sne = info->snd_sne; + opt->rcv_seq = tp->rcv_nxt; + opt->snd_seq = tp->snd_nxt; + + return 0; +} + +int tcp_set_authopt_repair(struct sock *sk, sockptr_t optval, unsigned int optlen) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_authopt_info *info; + struct tcp_authopt_repair val; + int err; + + sock_owned_by_me(sk); + err = check_sysctl_tcp_authopt(); + if (err) + return err; + + if (optlen != sizeof(val)) + return -EFAULT; + if (copy_from_sockptr(&val, optval, sizeof(val))) + return -EFAULT; + + /* tcp_authopt repair relies on fields that are only initialized after + * tcp_connect. Doing this setsockopt before connect() can't be correct + * so return an error. + */ + if (sk->sk_state != TCP_ESTABLISHED) + return -EPERM; + + info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk)); + if (!info) + return -ENOENT; + if (!tp->repair) + return -EPERM; + + info->dst_isn = val.dst_isn; + info->src_isn = val.src_isn; + info->rcv_sne = compute_sne(val.rcv_sne, val.rcv_seq, tp->rcv_nxt); + info->snd_sne = compute_sne(val.snd_sne, val.snd_seq, tp->snd_nxt); + + return 0; +} + #ifdef CONFIG_PROC_FS struct tcp_authopt_iter_state { struct seq_net_private p; };

Add support for configuring TCP Authentication Option. Only a single key is supported with default options.

Reviewed-by: David Ahern dsahern@kernel.org Signed-off-by: Leonard Crestez cdleonard@gmail.com --- tools/testing/selftests/net/nettest.c | 156 ++++++++++++++++++++++++-- 1 file changed, 145 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/net/nettest.c b/tools/testing/selftests/net/nettest.c index 30585050e00a..c5faabf6ba34 100644 --- a/tools/testing/selftests/net/nettest.c +++ b/tools/testing/selftests/net/nettest.c @@ -27,10 +27,11 @@ #include <string.h> #include <unistd.h> #include <time.h> #include <errno.h> #include <getopt.h> +#include <stdbool.h>

#include <linux/xfrm.h> #include <linux/ipsec.h> #include <linux/pfkeyv2.h>

@@ -104,10 +105,12 @@ struct sock_args { } key_addr; unsigned int key_addr_prefix_len; /* 0: default, -1: force off, +1: force on */ int bind_key_ifindex;

+ const char *authopt_password; + /* expected addresses and device index for connection */ const char *expected_dev; const char *expected_server_dev; int expected_ifindex;

@@ -257,10 +260,75 @@ static int switch_ns(const char *ns) close(fd);

return ret; }

+/* Fill key identification fields: address and ifindex */ +static void tcp_authopt_key_fill_id(struct tcp_authopt_key *key, struct sock_args *args) +{ + if (args->key_addr_prefix_str) { + key->flags |= TCP_AUTHOPT_KEY_ADDR_BIND; + switch (args->version) { + case AF_INET: + memcpy(&key->addr, &args->key_addr.v4, sizeof(args->key_addr.v4)); + break; + case AF_INET6: + memcpy(&key->addr, &args->key_addr.v6, sizeof(args->key_addr.v6)); + break; + default: + log_error("unknown address family\n"); + exit(1); + } + if (args->key_addr_prefix_len) { + key->flags |= TCP_AUTHOPT_KEY_PREFIXLEN; + key->prefixlen = args->key_addr_prefix_len; + } + } + + if ((args->ifindex && args->bind_key_ifindex >= 0) || args->bind_key_ifindex >= 1) { + key->flags |= TCP_AUTHOPT_KEY_IFINDEX; + key->ifindex = args->ifindex; + log_msg("TCP_AUTHOPT_KEY_IFINDEX set ifindex=%d\n", key->ifindex); + } else { + log_msg("TCP_AUTHOPT_KEY_IFINDEX off\n", key->ifindex); + } +} + +static int tcp_del_authopt(int sd, struct sock_args *args) +{ + struct tcp_authopt_key key; + int rc; + + memset(&key, 0, sizeof(key)); + key.flags |= TCP_AUTHOPT_KEY_DEL; + tcp_authopt_key_fill_id(&key, args); + + rc = setsockopt(sd, IPPROTO_TCP, TCP_AUTHOPT_KEY, &key, sizeof(key)); + if (rc < 0) + log_err_errno("setsockopt(TCP_AUTHOPT_KEY) del fail"); + + return rc; +} + +static int tcp_set_authopt(int sd, struct sock_args *args) +{ + struct tcp_authopt_key key; + int rc; + + memset(&key, 0, sizeof(key)); + strcpy((char *)key.key, args->authopt_password); + key.keylen = strlen(args->authopt_password); + key.alg = TCP_AUTHOPT_ALG_HMAC_SHA_1_96; + tcp_authopt_key_fill_id(&key, args); + + rc = setsockopt(sd, IPPROTO_TCP, TCP_AUTHOPT_KEY, &key, sizeof(key)); + if (rc < 0) + log_err_errno("setsockopt(TCP_AUTHOPT_KEY) add fail"); + + return rc; +} + static int tcp_md5sig(int sd, void *addr, socklen_t alen, struct sock_args *args) { int keylen = strlen(args->password); struct tcp_md5sig md5sig = {}; int opt = TCP_MD5SIG; @@ -1549,10 +1617,15 @@ static int do_server(struct sock_args *args, int ipc_fd) if (args->password && tcp_md5_remote(lsd, args)) { close(lsd); goto err_exit; }

+ if (args->authopt_password && tcp_set_authopt(lsd, args)) { + close(lsd); + goto err_exit; + } + ipc_write(ipc_fd, 1); while (1) { log_msg("waiting for client connection.\n"); FD_ZERO(&rfds); FD_SET(lsd, &rfds); @@ -1671,10 +1744,13 @@ static int connectsock(void *addr, socklen_t alen, struct sock_args *args) goto out;

if (args->password && tcp_md5sig(sd, addr, alen, args)) goto err;

+ if (args->authopt_password && tcp_set_authopt(sd, args)) + goto err; + if (args->bind_test_only) goto out;

if (connect(sd, addr, alen) < 0) { if (errno != EINPROGRESS) { @@ -1860,11 +1936,11 @@ static int ipc_parent(int cpid, int fd, struct sock_args *args)

wait(&status); return client_status; }

-#define GETOPT_STR "sr:l:c:p:t:g:P:DRn:M:X:m:d:I:BN:O:SUCi6xL:0:1:2:3:Fbqf" +#define GETOPT_STR "sr:l:c:p:t:g:P:DRn:M:X:m:A:d:I:BN:O:SUCi6xL:0:1:2:3:Fbqf" #define OPT_FORCE_BIND_KEY_IFINDEX 1001 #define OPT_NO_BIND_KEY_IFINDEX 1002

static struct option long_opts[] = { {"force-bind-key-ifindex", 0, 0, OPT_FORCE_BIND_KEY_IFINDEX}, @@ -1906,14 +1982,15 @@ static void print_usage(char *prog) " -L len send random message of given length\n" " -n num number of times to send message\n" "\n" " -M password use MD5 sum protection\n" " -X password MD5 password for client mode\n" - " -m prefix/len prefix and length to use for MD5 key\n" - " --no-bind-key-ifindex: Force TCP_MD5SIG_FLAG_IFINDEX off\n" - " --force-bind-key-ifindex: Force TCP_MD5SIG_FLAG_IFINDEX on\n" + " -m prefix/len prefix and length to use for MD5/AO key\n" + " --no-bind-key-ifindex: Force disable binding key to ifindex\n" + " --force-bind-key-ifindex: Force enable binding key to ifindex\n" " (default: only if -I is passed)\n" + " -A password use RFC5925 TCP Authentication Option with password\n" "\n" " -g grp multicast group (e.g., 239.1.1.1)\n" " -i interactive mode (default is echo and terminate)\n" "\n" " -0 addr Expected local address\n" @@ -1924,17 +2001,64 @@ static void print_usage(char *prog) " -b Bind test only.\n" " -q Be quiet. Run test without printing anything.\n" , prog, DEFAULT_PORT); }

-int main(int argc, char *argv[]) +/* Needs explicit cleanup because keys are global per-namespace */ +void cleanup_tcp_authopt(struct sock_args *args) +{ + int fd; + + if (!args->authopt_password) + return; + + fd = socket(AF_INET, SOCK_STREAM, 0); + if (fd < 0) { + log_err_errno("Failed to create socket"); + return; + } + tcp_del_authopt(fd, args); + close(fd); +} + +static bool cleanup_done; +static struct sock_args args = { + .version = AF_INET, + .type = SOCK_STREAM, + .port = DEFAULT_PORT, +}; + +void cleanup(void) +{ + if (cleanup_done) + return; + cleanup_done = true; + cleanup_tcp_authopt(&args); +} + +void signal_handler(int num) +{ + cleanup(); +} + +void atexit_handler(void) +{ + cleanup(); +} + +/* Explicit cleanup is required for TCP-AO because keys are global. */ +static void register_cleanup(void) { - struct sock_args args = { - .version = AF_INET, - .type = SOCK_STREAM, - .port = DEFAULT_PORT, + struct sigaction sa = { + .sa_handler = signal_handler, }; + sigaction(SIGINT, &sa, NULL); + atexit(atexit_handler); +} + +int main(int argc, char *argv[]) +{ struct protoent *pe; int both_mode = 0; unsigned int tmp; int forever = 0; int fd[2]; @@ -2031,10 +2155,13 @@ int main(int argc, char *argv[]) args.client_pw = optarg; break; case 'm': args.key_addr_prefix_str = optarg; break; + case 'A': + args.authopt_password = optarg; + break; case 'S': args.use_setsockopt = 1; break; case 'f': args.use_freebind = 1; @@ -2097,12 +2224,17 @@ int main(int argc, char *argv[]) args.type != SOCK_STREAM)) { log_error("MD5 passwords apply to TCP only and require a remote ip for the password\n"); return 1; }

- if (args.key_addr_prefix_str && !args.password) { - log_error("Prefix range for MD5 protection specified without a password\n"); + if (args.key_addr_prefix_str && !args.password && !args.authopt_password) { + log_error("Prefix range for authentication requires -M or -A\n"); + return 1; + } + + if (args.key_addr_prefix_len && args.authopt_password) { + log_error("TCP-AO does not support prefix match, only full address\n"); return 1; }

if (iter == 0) { fprintf(stderr, "Invalid number of messages to send\n"); @@ -2125,10 +2257,12 @@ int main(int argc, char *argv[]) fprintf(stderr, "Local (server mode) or remote IP (client IP) required\n"); return 1; }

+ register_cleanup(); + if (interactive) { prog_timeout = 0; msg = NULL; }