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authorPatrick McHardy <kaber@trash.net>2013-09-30 08:51:46 +0100
committerPablo Neira Ayuso <pablo@netfilter.org>2013-09-30 12:44:38 +0200
commitf4a87e7bd2eaef26a3ca25437ce8b807de2966ad (patch)
tree72359689d53c3ce656b4568f04b8ee92dd2e05f4 /net
parentd1ee4fea0b6946dd8bc61b46db35ea80af7af34b (diff)
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netfilter: synproxy: fix BUG_ON triggered by corrupt TCP packets
TCP packets hitting the SYN proxy through the SYNPROXY target are not validated by TCP conntrack. When th->doff is below 5, an underflow happens when calculating the options length, causing skb_header_pointer() to return NULL and triggering the BUG_ON(). Handle this case gracefully by checking for NULL instead of using BUG_ON(). Reported-by: Martin Topholm <mph@one.com> Tested-by: Martin Topholm <mph@one.com> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/netfilter/ipt_SYNPROXY.c10
-rw-r--r--net/ipv6/netfilter/ip6t_SYNPROXY.c10
-rw-r--r--net/netfilter/nf_synproxy_core.c12
3 files changed, 21 insertions, 11 deletions
diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c
index 67e17dcda65e..b6346bf2fde3 100644
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -267,7 +267,8 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par)
if (th == NULL)
return NF_DROP;
- synproxy_parse_options(skb, par->thoff, th, &opts);
+ if (!synproxy_parse_options(skb, par->thoff, th, &opts))
+ return NF_DROP;
if (th->syn && !(th->ack || th->fin || th->rst)) {
/* Initial SYN from client */
@@ -350,7 +351,8 @@ static unsigned int ipv4_synproxy_hook(unsigned int hooknum,
/* fall through */
case TCP_CONNTRACK_SYN_SENT:
- synproxy_parse_options(skb, thoff, th, &opts);
+ if (!synproxy_parse_options(skb, thoff, th, &opts))
+ return NF_DROP;
if (!th->syn && th->ack &&
CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
@@ -373,7 +375,9 @@ static unsigned int ipv4_synproxy_hook(unsigned int hooknum,
if (!th->syn || !th->ack)
break;
- synproxy_parse_options(skb, thoff, th, &opts);
+ if (!synproxy_parse_options(skb, thoff, th, &opts))
+ return NF_DROP;
+
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
synproxy->tsoff = opts.tsval - synproxy->its;
diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c
index 19cfea8dbcaa..2748b042da72 100644
--- a/net/ipv6/netfilter/ip6t_SYNPROXY.c
+++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c
@@ -282,7 +282,8 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par)
if (th == NULL)
return NF_DROP;
- synproxy_parse_options(skb, par->thoff, th, &opts);
+ if (!synproxy_parse_options(skb, par->thoff, th, &opts))
+ return NF_DROP;
if (th->syn && !(th->ack || th->fin || th->rst)) {
/* Initial SYN from client */
@@ -372,7 +373,8 @@ static unsigned int ipv6_synproxy_hook(unsigned int hooknum,
/* fall through */
case TCP_CONNTRACK_SYN_SENT:
- synproxy_parse_options(skb, thoff, th, &opts);
+ if (!synproxy_parse_options(skb, thoff, th, &opts))
+ return NF_DROP;
if (!th->syn && th->ack &&
CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
@@ -395,7 +397,9 @@ static unsigned int ipv6_synproxy_hook(unsigned int hooknum,
if (!th->syn || !th->ack)
break;
- synproxy_parse_options(skb, thoff, th, &opts);
+ if (!synproxy_parse_options(skb, thoff, th, &opts))
+ return NF_DROP;
+
if (opts.options & XT_SYNPROXY_OPT_TIMESTAMP)
synproxy->tsoff = opts.tsval - synproxy->its;
diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index 6fd967c6278c..cdf4567ba9b3 100644
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -24,7 +24,7 @@
int synproxy_net_id;
EXPORT_SYMBOL_GPL(synproxy_net_id);
-void
+bool
synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
const struct tcphdr *th, struct synproxy_options *opts)
{
@@ -32,7 +32,8 @@ synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
u8 buf[40], *ptr;
ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
- BUG_ON(ptr == NULL);
+ if (ptr == NULL)
+ return false;
opts->options = 0;
while (length > 0) {
@@ -41,16 +42,16 @@ synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
switch (opcode) {
case TCPOPT_EOL:
- return;
+ return true;
case TCPOPT_NOP:
length--;
continue;
default:
opsize = *ptr++;
if (opsize < 2)
- return;
+ return true;
if (opsize > length)
- return;
+ return true;
switch (opcode) {
case TCPOPT_MSS:
@@ -84,6 +85,7 @@ synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
length -= opsize;
}
}
+ return true;
}
EXPORT_SYMBOL_GPL(synproxy_parse_options);