[PATCH 0/2] Netfilter fixes for net

[PATCH 0/2] Netfilter fixes for net

[Pablo Neira Ayuso]

Hi David,

The following patchset contains Netfilter fixes for net:

1) Out-of-bound access to packet data from the snmp nat helper,
   from Jann Horn.

2) ICMP(v6) error packets are set as related traffic by conntrack,
   update protocol number before calling nf_nat_ipv4_manip_pkt()
   to use ICMP(v6) rather than the original protocol number,
   from Florian Westphal.

You can pull these changes from:

  git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git

Thanks!

----------------------------------------------------------------

The following changes since commit 31b58ad0c3279817cd246eab27eaf53b626dfcde:

  Merge branch 'r8169-revert-two-commits-due-to-a-regression' (2019-02-10 12:54:49 -0800)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git HEAD

for you to fetch changes up to 8303b7e8f018724a2cd7752eb29c2801fa8c4067:

  netfilter: nat: fix spurious connection timeouts (2019-02-11 17:43:17 +0100)

----------------------------------------------------------------
Florian Westphal (1):
      netfilter: nat: fix spurious connection timeouts

Jann Horn (1):
      netfilter: nf_nat_snmp_basic: add missing length checks in ASN.1 cbs

 net/ipv4/netfilter/nf_nat_l3proto_ipv4.c    | 1 +
 net/ipv4/netfilter/nf_nat_snmp_basic_main.c | 7 ++++++-
 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c    | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

[PATCH 1/2] netfilter: nf_nat_snmp_basic: add missing length checks in ASN.1 cbs

[Pablo Neira Ayuso]

From: Jann Horn <jannh@google.com>

The generic ASN.1 decoder infrastructure doesn't guarantee that callbacks
will get as much data as they expect; callbacks have to check the `datalen`
parameter before looking at `data`. Make sure that snmp_version() and
snmp_helper() don't read/write beyond the end of the packet data.

(Also move the assignment to `pdata` down below the check to make it clear
that it isn't necessarily a pointer we can use before the `datalen` check.)

Fixes: cc2d58634e0f ("netfilter: nf_nat_snmp_basic: use asn1 decoder library")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/ipv4/netfilter/nf_nat_snmp_basic_main.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic_main.c b/net/ipv4/netfilter/nf_nat_snmp_basic_main.c
index a0aa13bcabda..0a8a60c1bf9a 100644
--- a/net/ipv4/netfilter/nf_nat_snmp_basic_main.c
+++ b/net/ipv4/netfilter/nf_nat_snmp_basic_main.c
@@ -105,6 +105,8 @@ static void fast_csum(struct snmp_ctx *ctx, unsigned char offset)
 int snmp_version(void *context, size_t hdrlen, unsigned char tag,
 		 const void *data, size_t datalen)
 {
+	if (datalen != 1)
+		return -EINVAL;
 	if (*(unsigned char *)data > 1)
 		return -ENOTSUPP;
 	return 1;
@@ -114,8 +116,11 @@ int snmp_helper(void *context, size_t hdrlen, unsigned char tag,
 		const void *data, size_t datalen)
 {
 	struct snmp_ctx *ctx = (struct snmp_ctx *)context;
-	__be32 *pdata = (__be32 *)data;
+	__be32 *pdata;
 
+	if (datalen != 4)
+		return -EINVAL;
+	pdata = (__be32 *)data;
 	if (*pdata == ctx->from) {
 		pr_debug("%s: %pI4 to %pI4\n", __func__,
 			 (void *)&ctx->from, (void *)&ctx->to);
-- 
2.11.0

[PATCH 2/2] netfilter: nat: fix spurious connection timeouts

[Pablo Neira Ayuso]

From: Florian Westphal <fw@strlen.de>

Sander Eikelenboom bisected a NAT related regression down
to the l4proto->manip_pkt indirection removal.

I forgot that ICMP(v6) errors (e.g. PKTTOOBIG) can be set as related
to the existing conntrack entry.

Therefore, when passing the skb to nf_nat_ipv4/6_manip_pkt(), that
ended up calling the wrong l4 manip function, as tuple->dst.protonum
is the original flows l4 protocol (TCP, UDP, etc).

Set the dst protocol field to ICMP(v6), we already have a private copy
of the tuple due to the inversion of src/dst.

Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
Fixes: faec18dbb0405 ("netfilter: nat: remove l4proto->manip_pkt")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/ipv4/netfilter/nf_nat_l3proto_ipv4.c | 1 +
 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
index 2687db015b6f..fa2ba7c500e4 100644
--- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
@@ -215,6 +215,7 @@ int nf_nat_icmp_reply_translation(struct sk_buff *skb,
 
 	/* Change outer to look like the reply to an incoming packet */
 	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
+	target.dst.protonum = IPPROTO_ICMP;
 	if (!nf_nat_ipv4_manip_pkt(skb, 0, &target, manip))
 		return 0;
 
diff --git a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
index 23022447eb49..7a41ee3c11b4 100644
--- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
@@ -226,6 +226,7 @@ int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 	}
 
 	nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
+	target.dst.protonum = IPPROTO_ICMPV6;
 	if (!nf_nat_ipv6_manip_pkt(skb, 0, &target, manip))
 		return 0;
 
-- 
2.11.0

Re: [PATCH 0/2] Netfilter fixes for net

[David Miller]

From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Mon, 11 Feb 2019 17:53:17 +0100

> The following patchset contains Netfilter fixes for net:
> 
> 1) Out-of-bound access to packet data from the snmp nat helper,
>    from Jann Horn.
> 
> 2) ICMP(v6) error packets are set as related traffic by conntrack,
>    update protocol number before calling nf_nat_ipv4_manip_pkt()
>    to use ICMP(v6) rather than the original protocol number,
>    from Florian Westphal.
> 
> You can pull these changes from:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git

Pulled, thanks Pablo.