[Patch net] xfrm: unify xfrm protocol checks

[Patch net] xfrm: unify xfrm protocol checks

[Cong Wang]

In commit 6a53b7593233 ("xfrm: check id proto in validate_tmpl()")
I introduced a check for xfrm protocol, but unfortunately
xfrm_id_proto_match() could still miss IPPROTO_ROUTING which causes
entries left in net->xfrm.state_all.

This patch extracts the check from validate_tmpl() to
xfrm_id_proto_valid() and uses it in all other places, including
the missing one in parse_ipsecrequest().

Fixes: 6a53b7593233 ("xfrm: check id proto in validate_tmpl()")
Reported-by: syzbot+0bf0519d6e0de15914fe@syzkaller.appspotmail.com
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 include/net/xfrm.h   | 21 ++++++++++++++++++---
 net/key/af_key.c     |  4 +++-
 net/xfrm/xfrm_user.c | 14 +-------------
 3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 85386becbaea..22ef7617087d 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1404,12 +1404,27 @@ static inline int xfrm_state_kern(const struct xfrm_state *x)
 	return atomic_read(&x->tunnel_users);
 }
 
+static inline bool xfrm_id_proto_valid(u8 proto)
+{
+	switch (proto) {
+	case IPPROTO_AH:
+	case IPPROTO_ESP:
+	case IPPROTO_COMP:
+#if IS_ENABLED(CONFIG_IPV6)
+	case IPPROTO_ROUTING:
+	case IPPROTO_DSTOPTS:
+#endif
+	case IPSEC_PROTO_ANY:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static inline int xfrm_id_proto_match(u8 proto, u8 userproto)
 {
 	return (!userproto || proto == userproto ||
-		(userproto == IPSEC_PROTO_ANY && (proto == IPPROTO_AH ||
-						  proto == IPPROTO_ESP ||
-						  proto == IPPROTO_COMP)));
+		(userproto == IPSEC_PROTO_ANY && xfrm_id_proto_valid(proto)));
 }
 
 /*
diff --git a/net/key/af_key.c b/net/key/af_key.c
index 5651c29cb5bd..4af1e1d60b9f 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -1951,8 +1951,10 @@ parse_ipsecrequest(struct xfrm_policy *xp, struct sadb_x_ipsecrequest *rq)
 
 	if (rq->sadb_x_ipsecrequest_mode == 0)
 		return -EINVAL;
+	if (!xfrm_id_proto_valid(rq->sadb_x_ipsecrequest_proto))
+		return -EINVAL;
 
-	t->id.proto = rq->sadb_x_ipsecrequest_proto; /* XXX check proto */
+	t->id.proto = rq->sadb_x_ipsecrequest_proto;
 	if ((mode = pfkey_mode_to_xfrm(rq->sadb_x_ipsecrequest_mode)) < 0)
 		return -EINVAL;
 	t->mode = mode;
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index a131f9ff979e..067ac9ed2918 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1513,20 +1513,8 @@ static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family)
 			return -EINVAL;
 		}
 
-		switch (ut[i].id.proto) {
-		case IPPROTO_AH:
-		case IPPROTO_ESP:
-		case IPPROTO_COMP:
-#if IS_ENABLED(CONFIG_IPV6)
-		case IPPROTO_ROUTING:
-		case IPPROTO_DSTOPTS:
-#endif
-		case IPSEC_PROTO_ANY:
-			break;
-		default:
+		if (!xfrm_id_proto_valid(ut[i].id.proto))
 			return -EINVAL;
-		}
-
 	}
 
 	return 0;
-- 
2.20.1

Re: [Patch net] xfrm: unify xfrm protocol checks

[Herbert Xu]

On Mon, Mar 18, 2019 at 10:08:24PM -0700, Cong Wang wrote:
>
> +static inline bool xfrm_id_proto_valid(u8 proto)
> +{
> +	switch (proto) {
> +	case IPPROTO_AH:
> +	case IPPROTO_ESP:
> +	case IPPROTO_COMP:
> +#if IS_ENABLED(CONFIG_IPV6)
> +	case IPPROTO_ROUTING:
> +	case IPPROTO_DSTOPTS:
> +#endif
> +	case IPSEC_PROTO_ANY:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
>  static inline int xfrm_id_proto_match(u8 proto, u8 userproto)
>  {
>  	return (!userproto || proto == userproto ||
> -		(userproto == IPSEC_PROTO_ANY && (proto == IPPROTO_AH ||
> -						  proto == IPPROTO_ESP ||
> -						  proto == IPPROTO_COMP)));
> +		(userproto == IPSEC_PROTO_ANY && xfrm_id_proto_valid(proto)));
>  }

This does not look right.  IPSEC_PROTO_ANY should only be allowed
in userproto and your patch is going to let it pass when it's in
proto.  Whether IPPROTO_ROUTING/IPPROTO_DSTOPTS should be allowed
in this context is also not obvious.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [Patch net] xfrm: unify xfrm protocol checks

[Cong Wang]

On Mon, Mar 18, 2019 at 10:17 PM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Mon, Mar 18, 2019 at 10:08:24PM -0700, Cong Wang wrote:
> >
> > +static inline bool xfrm_id_proto_valid(u8 proto)
> > +{
> > +     switch (proto) {
> > +     case IPPROTO_AH:
> > +     case IPPROTO_ESP:
> > +     case IPPROTO_COMP:
> > +#if IS_ENABLED(CONFIG_IPV6)
> > +     case IPPROTO_ROUTING:
> > +     case IPPROTO_DSTOPTS:
> > +#endif
> > +     case IPSEC_PROTO_ANY:
> > +             return true;
> > +     default:
> > +             return false;
> > +     }
> > +}
> > +
> >  static inline int xfrm_id_proto_match(u8 proto, u8 userproto)
> >  {
> >       return (!userproto || proto == userproto ||
> > -             (userproto == IPSEC_PROTO_ANY && (proto == IPPROTO_AH ||
> > -                                               proto == IPPROTO_ESP ||
> > -                                               proto == IPPROTO_COMP)));
> > +             (userproto == IPSEC_PROTO_ANY && xfrm_id_proto_valid(proto)));
> >  }
>
> This does not look right.  IPSEC_PROTO_ANY should only be allowed
> in userproto and your patch is going to let it pass when it's in
> proto.  Whether IPPROTO_ROUTING/IPPROTO_DSTOPTS should be allowed
> in this context is also not obvious.

IIRC, it is Steffen who suggested to add IPPROTO_ROUTING/IPPROTO_DSTOPTS
back to commit 6a53b7593233. My xfrm knowledge is not enough to
figure out IPPROTO_ROUTING/IPPROTO_DSTOPTS.

I just assume validate_tmpl() is correct.

Re: [Patch net] xfrm: unify xfrm protocol checks

[Herbert Xu]

On Tue, Mar 19, 2019 at 01:42:53PM -0700, Cong Wang wrote:
>
> IIRC, it is Steffen who suggested to add IPPROTO_ROUTING/IPPROTO_DSTOPTS
> back to commit 6a53b7593233. My xfrm knowledge is not enough to
> figure out IPPROTO_ROUTING/IPPROTO_DSTOPTS.

OK I dug into the history of xfrm_id_proto_match and this is
definitely not right.  The intention appears to be that
IPSEC_PROTO_ANY should only match genuine IPsec protocols, i.e.,
AH/ESP/COMP, while the special value of zero will match everything.

So I think what we should do is get rid of the validation function
that you added in 6a5t3b7593233, and then change those internal
functions which were incorrectly using IPSEC_PROTO_ANY to using
zero instead.

Does anybody still use IPPROTO_ROUTING/IPPROTO_DSTOPTS? It's always
a pain when people come and add features and then don't shoulder
the burden of maintaining them.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [Patch net] xfrm: unify xfrm protocol checks

[Cong Wang]

On Tue, Mar 19, 2019 at 10:35 PM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Tue, Mar 19, 2019 at 01:42:53PM -0700, Cong Wang wrote:
> >
> > IIRC, it is Steffen who suggested to add IPPROTO_ROUTING/IPPROTO_DSTOPTS
> > back to commit 6a53b7593233. My xfrm knowledge is not enough to
> > figure out IPPROTO_ROUTING/IPPROTO_DSTOPTS.
>
> OK I dug into the history of xfrm_id_proto_match and this is
> definitely not right.  The intention appears to be that
> IPSEC_PROTO_ANY should only match genuine IPsec protocols, i.e.,
> AH/ESP/COMP, while the special value of zero will match everything.
>
> So I think what we should do is get rid of the validation function
> that you added in 6a5t3b7593233, and then change those internal
> functions which were incorrectly using IPSEC_PROTO_ANY to using
> zero instead.

Good point. Replacing IPSEC_PROTO_ANY with zero should
work too, but on the other hand, id.proto is still never allowed to
be any other protocol than these 6 listed, no?


>
> Does anybody still use IPPROTO_ROUTING/IPPROTO_DSTOPTS? It's always
> a pain when people come and add features and then don't shoulder
> the burden of maintaining them.

Yeah, at least iproute2 does the same check:

static const struct typeent xfrmproto_types[] = {
        { "esp", IPPROTO_ESP }, { "ah", IPPROTO_AH }, { "comp", IPPROTO_COMP },
        { "route2", IPPROTO_ROUTING }, { "hao", IPPROTO_DSTOPTS },
        { "ipsec-any", IPSEC_PROTO_ANY },
        { NULL, -1 }
};

Re: [Patch net] xfrm: unify xfrm protocol checks

[Herbert Xu]

On Thu, Mar 21, 2019 at 09:06:05PM -0700, Cong Wang wrote:
>
> Good point. Replacing IPSEC_PROTO_ANY with zero should
> work too, but on the other hand, id.proto is still never allowed to
> be any other protocol than these 6 listed, no?

It should never be IPSEC_PROTO_ANY since that's used as a wildcard.

IOW if you're going to tighten up the check for the id.proto filed
in an actual state, you should distinguish between the case of an
ID that's used to add/modify a state vs. an ID that's be used to
query a state.  IPSEC_PROTO_ANY and zero should be denied in the
first case and allowed in the second case.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [Patch net] xfrm: unify xfrm protocol checks

[Cong Wang]

On Thu, Mar 21, 2019 at 9:11 PM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> On Thu, Mar 21, 2019 at 09:06:05PM -0700, Cong Wang wrote:
> >
> > Good point. Replacing IPSEC_PROTO_ANY with zero should
> > work too, but on the other hand, id.proto is still never allowed to
> > be any other protocol than these 6 listed, no?
>
> It should never be IPSEC_PROTO_ANY since that's used as a wildcard.
>
> IOW if you're going to tighten up the check for the id.proto filed
> in an actual state, you should distinguish between the case of an
> ID that's used to add/modify a state vs. an ID that's be used to
> query a state.  IPSEC_PROTO_ANY and zero should be denied in the
> first case and allowed in the second case.

Yeah, this makes sense. Let me see if I can figure this out correctly.

Thanks for the details!