[PATCH v6 17/26] tcp: authopt: Add prefixlen support

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 f681d2221ce3..6520c6d02755 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 1630fc2aa082..4f83d8e54fef 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 ed27feb93b0e..b1063e1e1b9f 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -403,18 +403,21 @@ 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 */ @@ -465,10 +468,17 @@ 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 0ead961fcfe0..e4aecd35ffda 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; }

/** @@ -626,21 +643,32 @@ 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(&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) @@ -676,10 +704,36 @@ 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);

@@ -725,10 +779,11 @@ 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; }