| From foo@baz Fri 17 Jul 2020 11:04:44 AM CEST |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Wed, 1 Jul 2020 18:39:33 -0700 |
| Subject: tcp: md5: allow changing MD5 keys in all socket states |
| |
| From: Eric Dumazet <edumazet@google.com> |
| |
| [ Upstream commit 1ca0fafd73c5268e8fc4b997094b8bb2bfe8deea ] |
| |
| This essentially reverts commit 721230326891 ("tcp: md5: reject TCP_MD5SIG |
| or TCP_MD5SIG_EXT on established sockets") |
| |
| Mathieu reported that many vendors BGP implementations can |
| actually switch TCP MD5 on established flows. |
| |
| Quoting Mathieu : |
| Here is a list of a few network vendors along with their behavior |
| with respect to TCP MD5: |
| |
| - Cisco: Allows for password to be changed, but within the hold-down |
| timer (~180 seconds). |
| - Juniper: When password is initially set on active connection it will |
| reset, but after that any subsequent password changes no network |
| resets. |
| - Nokia: No notes on if they flap the tcp connection or not. |
| - Ericsson/RedBack: Allows for 2 password (old/new) to co-exist until |
| both sides are ok with new passwords. |
| - Meta-Switch: Expects the password to be set before a connection is |
| attempted, but no further info on whether they reset the TCP |
| connection on a change. |
| - Avaya: Disable the neighbor, then set password, then re-enable. |
| - Zebos: Would normally allow the change when socket connected. |
| |
| We can revert my prior change because commit 9424e2e7ad93 ("tcp: md5: fix potential |
| overestimation of TCP option space") removed the leak of 4 kernel bytes to |
| the wire that was the main reason for my patch. |
| |
| While doing my investigations, I found a bug when a MD5 key is changed, leading |
| to these commits that stable teams want to consider before backporting this revert : |
| |
| Commit 6a2febec338d ("tcp: md5: add missing memory barriers in tcp_md5_do_add()/tcp_md5_hash_key()") |
| Commit e6ced831ef11 ("tcp: md5: refine tcp_md5_do_add()/tcp_md5_hash_key() barriers") |
| |
| Fixes: 721230326891 "tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG_EXT on established sockets" |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/ipv4/tcp.c | 5 +---- |
| 1 file changed, 1 insertion(+), 4 deletions(-) |
| |
| --- a/net/ipv4/tcp.c |
| +++ b/net/ipv4/tcp.c |
| @@ -2672,10 +2672,7 @@ static int do_tcp_setsockopt(struct sock |
| |
| #ifdef CONFIG_TCP_MD5SIG |
| case TCP_MD5SIG: |
| - if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) |
| - err = tp->af_specific->md5_parse(sk, optval, optlen); |
| - else |
| - err = -EINVAL; |
| + err = tp->af_specific->md5_parse(sk, optval, optlen); |
| break; |
| #endif |
| case TCP_USER_TIMEOUT: |