iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

tcp: md5: Fix overlap between vrf and non-vrf keys

Browse Source 
With net.ipv4.tcp_l3mdev_accept=1 it is possible for a listen socket to
accept connection from the same client address in different VRFs. It is
also possible to set different MD5 keys for these clients which differ
only in the tcpm_l3index field.

This appears to work when distinguishing between different VRFs but not
between non-VRF and VRF connections. In particular:

 * tcp_md5_do_lookup_exact will match a non-vrf key against a vrf key.
This means that adding a key with l3index != 0 after a key with l3index
== 0 will cause the earlier key to be deleted. Both keys can be present
if the non-vrf key is added later.
 * _tcp_md5_do_lookup can match a non-vrf key before a vrf key. This
casues failures if the passwords differ.

Fix this by making tcp_md5_do_lookup_exact perform an actual exact
comparison on l3index and by making  __tcp_md5_do_lookup perfer
vrf-bound keys above other considerations like prefixlen.

Fixes: dea53bb80e ("tcp: Add l3index to tcp_md5sig_key and md5 functions")
Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Leonard Crestez 2021-10-15 10:26:04 +03:00 committed by David S. Miller
parent 46393d61a3
commit 86f1e3a848
1 changed files with 16 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
net/ipv4/tcp_ipv4.c
View File

@ -1037,6 +1037,20 @@ static void tcp_v4_reqsk_destructor(struct request_sock *req)
DEFINE_STATIC_KEY_FALSE(tcp_md5_needed);
EXPORT_SYMBOL(tcp_md5_needed);
static bool better_md5_match(struct tcp_md5sig_key *old, struct tcp_md5sig_key *new)
{
if (!old)
return true;
/* l3index always overrides non-l3index */
if (old->l3index && new->l3index == 0)
return false;
if (old->l3index == 0 && new->l3index)
return true;
return old->prefixlen < new->prefixlen;
}
/* Find the Key structure for an address. */
struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
const union tcp_md5_addr *addr,
@ -1074,8 +1088,7 @@ struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
match = false;
}
if (match && (!best_match ||
key->prefixlen > best_match->prefixlen))
if (match && better_md5_match(best_match, key))
best_match = key;
}
return best_match;
@ -1105,7 +1118,7 @@ static struct tcp_md5sig_key *tcp_md5_do_lookup_exact(const struct sock *sk,
lockdep_sock_is_held(sk)) {
if (key->family != family)
continue;
if (key->l3index && key->l3index != l3index)
if (key->l3index != l3index)
continue;
if (!memcmp(&key->addr, addr, size) &&
key->prefixlen == prefixlen)