From c4c07b4d6fa1f11880eab8e076d3d060ef3f55fc Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Wed, 6 Feb 2019 22:56:15 +0100 Subject: [PATCH 1/2] netfilter: nf_nat_snmp_basic: add missing length checks in ASN.1 cbs 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 Signed-off-by: Pablo Neira Ayuso --- 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); From 8303b7e8f018724a2cd7752eb29c2801fa8c4067 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 8 Feb 2019 16:39:52 +0100 Subject: [PATCH 2/2] netfilter: nat: fix spurious connection timeouts 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 Tested-by: Sander Eikelenboom Fixes: faec18dbb0405 ("netfilter: nat: remove l4proto->manip_pkt") Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- 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;