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xfrm: Treat already-verified secpath entries as optional 

This change allows inbound traffic through nested IPsec tunnels to
successfully match policies and templates, while retaining the secpath
stack trace as necessary for netfilter policies.

Specifically, this patch marks secpath entries that have already matched
against a relevant policy as having been verified, allowing it to be
treated as optional and skipped after a tunnel decapsulation (during
which the src/dst/proto/etc may have changed, and the correct policy
chain no long be resolvable).

This approach is taken as opposed to the iteration in b0355dbbf1,
where the secpath was cleared, since that breaks subsequent validations
that rely on the existence of the secpath entries (netfilter policies, or
transport-in-tunnel mode, where policies remain resolvable).

Fixes: b0355dbbf1 ("Fix XFRM-I support for nested ESP tunnels")
Test: Tested against Android Kernel Unit Tests
Test: Tested against Android CTS
Signed-off-by: Benedict Wong <benedictwong@google.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Benedict Wong 2023-05-10 01:30:21 +00:00 committed by Steffen Klassert
parent 67caf26d76
commit 1f8b6df6a9
3 changed files with 14 additions and 0 deletions
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1
include/net/xfrm.h
View File

@ -1054,6 +1054,7 @@ struct xfrm_offload {
struct sec_path {
int len;
int olen;
int verified_cnt;
struct xfrm_state *xvec[XFRM_MAX_DEPTH];
struct xfrm_offload ovec[XFRM_MAX_OFFLOAD_DEPTH];

1
net/xfrm/xfrm_input.c
View File

@ -131,6 +131,7 @@ struct sec_path *secpath_set(struct sk_buff *skb)
memset(sp->ovec, 0, sizeof(sp->ovec));
sp->olen = 0;
sp->len = 0;
sp->verified_cnt = 0;
return sp;
}

12
net/xfrm/xfrm_policy.c
View File

@ -3349,6 +3349,13 @@ xfrm_policy_ok(const struct xfrm_tmpl *tmpl, const struct sec_path *sp, int star
if (xfrm_state_ok(tmpl, sp->xvec[idx], family, if_id))
return ++idx;
if (sp->xvec[idx]->props.mode != XFRM_MODE_TRANSPORT) {
if (idx < sp->verified_cnt) {
/* Secpath entry previously verified, consider optional and
* continue searching
*/
continue;
}
if (start == -1)
start = -2-idx;
break;
@ -3723,6 +3730,9 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
* Order is _important_. Later we will implement
* some barriers, but at the moment barriers
* are implied between each two transformations.
* Upon success, marks secpath entries as having been
* verified to allow them to be skipped in future policy
* checks (e.g. nested tunnels).
*/
for (i = xfrm_nr-1, k = 0; i >= 0; i--) {
k = xfrm_policy_ok(tpp[i], sp, k, family, if_id);
@ -3741,6 +3751,8 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
}
xfrm_pols_put(pols, npols);
sp->verified_cnt = k;
return 1;
}
XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLBLOCK);