From 0aadc73995d08f6b0dc061c14a564ffa46f5914e Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Mon, 23 Oct 2023 20:21:56 +0100 Subject: net/tcp: Prevent TCP-MD5 with TCP-AO being set Be as conservative as possible: if there is TCP-MD5 key for a given peer regardless of L3 interface - don't allow setting TCP-AO key for the same peer. According to RFC5925, TCP-AO is supposed to replace TCP-MD5 and there can't be any switch between both on any connected tuple. Later it can be relaxed, if there's a use, but in the beginning restrict any intersection. Note: it's still should be possible to set both TCP-MD5 and TCP-AO keys on a listening socket for *different* peers. Co-developed-by: Francesco Ruggeri Signed-off-by: Francesco Ruggeri Co-developed-by: Salam Noureddine Signed-off-by: Salam Noureddine Signed-off-by: Dmitry Safonov Acked-by: David Ahern Signed-off-by: David S. Miller --- net/ipv4/tcp_ao.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'net/ipv4/tcp_ao.c') diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index 3c2d005a37ce..ee23356101f4 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -116,6 +116,13 @@ static struct tcp_ao_key *__tcp_ao_do_lookup(const struct sock *sk, return NULL; } +struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk, + const union tcp_ao_addr *addr, + int family, int sndid, int rcvid) +{ + return __tcp_ao_do_lookup(sk, addr, family, U8_MAX, sndid, rcvid); +} + static struct tcp_ao_info *tcp_ao_alloc_info(gfp_t flags) { struct tcp_ao_info *ao; @@ -162,6 +169,14 @@ void tcp_ao_destroy_sock(struct sock *sk) kfree_rcu(ao, rcu); } +struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk, + int sndid, int rcvid) +{ + union tcp_ao_addr *addr = (union tcp_ao_addr *)&addr_sk->sk_daddr; + + return tcp_ao_do_lookup(sk, addr, AF_INET, sndid, rcvid); +} + static bool tcp_ao_can_set_current_rnext(struct sock *sk) { /* There aren't current/rnext keys on TCP_LISTEN sockets */ @@ -497,6 +512,10 @@ static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family, return -EINVAL; } + /* Don't allow keys for peers that have a matching TCP-MD5 key */ + if (tcp_md5_do_lookup_any_l3index(sk, addr, family)) + return -EKEYREJECTED; + ao_info = setsockopt_ao_info(sk); if (IS_ERR(ao_info)) return PTR_ERR(ao_info); @@ -698,6 +717,31 @@ static int tcp_ao_del_cmd(struct sock *sk, unsigned short int family, return -ENOENT; } +/* cmd.ao_required makes a socket TCP-AO only. + * Don't allow any md5 keys for any l3intf on the socket together with it. + * Restricting it early in setsockopt() removes a check for + * ao_info->ao_required on inbound tcp segment fast-path. + */ +static int tcp_ao_required_verify(struct sock *sk) +{ +#ifdef CONFIG_TCP_MD5SIG + const struct tcp_md5sig_info *md5sig; + + if (!static_branch_unlikely(&tcp_md5_needed.key)) + return 0; + + md5sig = rcu_dereference_check(tcp_sk(sk)->md5sig_info, + lockdep_sock_is_held(sk)); + if (!md5sig) + return 0; + + if (rcu_dereference_check(hlist_first_rcu(&md5sig->head), + lockdep_sock_is_held(sk))) + return 1; +#endif + return 0; +} + static int tcp_ao_info_cmd(struct sock *sk, unsigned short int family, sockptr_t optval, int optlen) { @@ -732,6 +776,9 @@ static int tcp_ao_info_cmd(struct sock *sk, unsigned short int family, first = true; } + if (cmd.ao_required && tcp_ao_required_verify(sk)) + return -EKEYREJECTED; + /* For sockets in TCP_CLOSED it's possible set keys that aren't * matching the future peer (address/port/VRF/etc), * tcp_ao_connect_init() will choose a correct matching MKT -- cgit v1.2.3