This is mainly intended to protect against local privilege escalations through a rarely used feature so it is deliberately not namespaced.
Enforcement is only at the setsockopt level, this should be enough to ensure that the tcp_authopt_needed static key never turns on.
No effort is made to handle disabling when the feature is already in use.
Signed-off-by: Leonard Crestez cdleonard@gmail.com --- Documentation/networking/ip-sysctl.rst | 6 ++++++ include/net/tcp_authopt.h | 1 + net/ipv4/sysctl_net_ipv4.c | 10 ++++++++++ net/ipv4/tcp_authopt.c | 11 +++++++++++ 4 files changed, 28 insertions(+)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index d91ab28718d4..16e34268ecb4 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -995,10 +995,16 @@ tcp_rx_skb_cache - BOOLEAN on systems with a lot of TCP sockets, since it increases memory usage.
Default: 0 (disabled)
+tcp_authopt - BOOLEAN + Enable the TCP Authentication Option (RFC5925), a replacement for TCP + MD5 Signatures (RFC2835). + + Default: 0 + UDP variables =============
udp_l3mdev_accept - BOOLEAN Enabling this option allows a "global" bound socket to work diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index 263f98c3a1a8..422f0034d32b 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -51,10 +51,11 @@ struct tcp_authopt_info { u32 src_isn; u32 dst_isn; };
#ifdef CONFIG_TCP_AUTHOPT +extern int sysctl_tcp_authopt; DECLARE_STATIC_KEY_FALSE(tcp_authopt_needed);
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); diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 4680268f2e59..365466fbca8b 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -17,10 +17,11 @@ #include <net/udp.h> #include <net/cipso_ipv4.h> #include <net/ping.h> #include <net/protocol.h> #include <net/netevent.h> +#include <net/tcp_authopt.h>
static int two = 2; static int three __maybe_unused = 3; static int four = 4; static int thousand = 1000; @@ -595,10 +596,19 @@ static struct ctl_table ipv4_table[] = { .procname = "tcp_tx_skb_cache", .data = &tcp_tx_skb_cache_key.key, .mode = 0644, .proc_handler = proc_do_static_key, }, +#ifdef CONFIG_TCP_AUTHOPT + { + .procname = "tcp_authopt", + .data = &sysctl_tcp_authopt, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, +#endif { } };
static struct ctl_table ipv4_net_table[] = { { diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 0c32b8fb1d41..41f844d5d49a 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -3,10 +3,15 @@ #include <linux/kernel.h> #include <net/tcp.h> #include <net/tcp_authopt.h> #include <crypto/hash.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; + /* This is enabled when first struct tcp_authopt_info is allocated and never released */ DEFINE_STATIC_KEY_FALSE(tcp_authopt_needed); /* only for CONFIG_IPV6=m */ EXPORT_SYMBOL(tcp_authopt_needed);
@@ -361,10 +366,12 @@ int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen) struct tcp_authopt opt; struct tcp_authopt_info *info; int err;
sock_owned_by_me(sk); + if (!sysctl_tcp_authopt) + return -EPERM;
err = _copy_from_sockptr_tolerant((u8*)&opt, sizeof(opt), optval, optlen); if (err) return err;
@@ -384,10 +391,12 @@ int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_authopt_info *info;
sock_owned_by_me(sk); + if (!sysctl_tcp_authopt) + return -EPERM;
memset(opt, 0, sizeof(*opt)); info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk)); if (!info) return -ENOENT; @@ -452,10 +461,12 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) struct tcp_authopt_key_info *key_info, *old_key_info; struct tcp_authopt_alg_imp *alg; int err;
sock_owned_by_me(sk); + if (!sysctl_tcp_authopt) + return -EPERM;
err = _copy_from_sockptr_tolerant((u8*)&opt, sizeof(opt), optval, optlen); if (err) return err;