diff options
| author | Pablo Neira Ayuso <pablo@netfilter.org> | 2013-05-07 03:22:18 +0200 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2013-05-16 17:35:53 +0200 |
| commit | bc6bcb59dd7c184d229f9e86d08aa56059938a4c (patch) | |
| tree | 1305eb74bb354d76cc815910a3ebe1f803b7a6f4 | |
| parent | 8cdb46da06ea94543a3b2e53e3e92736421d1093 (diff) | |
netfilter: xt_TCPOPTSTRIP: fix possible mangling beyond packet boundary
This target assumes that tcph->doff is well-formed, that may be well
not the case. Add extra sanity checkings to avoid possible crash due
to read/write out of the real packet boundary. After this patch, the
default action on malformed TCP packets is to drop them. Moreover,
fragments are skipped.
Reported-by: Rafal Kupka <rkupka@telemetry.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
| -rw-r--r-- | net/netfilter/xt_TCPOPTSTRIP.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/net/netfilter/xt_TCPOPTSTRIP.c b/net/netfilter/xt_TCPOPTSTRIP.c index 25fd1c4e1eec..1eb1a44bfd3d 100644 --- a/net/netfilter/xt_TCPOPTSTRIP.c +++ b/net/netfilter/xt_TCPOPTSTRIP.c @@ -30,17 +30,28 @@ static inline unsigned int optlen(const u_int8_t *opt, unsigned int offset) static unsigned int tcpoptstrip_mangle_packet(struct sk_buff *skb, - const struct xt_tcpoptstrip_target_info *info, + const struct xt_action_param *par, unsigned int tcphoff, unsigned int minlen) { + const struct xt_tcpoptstrip_target_info *info = par->targinfo; unsigned int optl, i, j; struct tcphdr *tcph; u_int16_t n, o; u_int8_t *opt; + int len; + + /* This is a fragment, no TCP header is available */ + if (par->fragoff != 0) + return XT_CONTINUE; if (!skb_make_writable(skb, skb->len)) return NF_DROP; + len = skb->len - tcphoff; + if (len < (int)sizeof(struct tcphdr) || + tcp_hdr(skb)->doff * 4 > len) + return NF_DROP; + tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); opt = (u_int8_t *)tcph; @@ -76,7 +87,7 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb, static unsigned int tcpoptstrip_tg4(struct sk_buff *skb, const struct xt_action_param *par) { - return tcpoptstrip_mangle_packet(skb, par->targinfo, ip_hdrlen(skb), + return tcpoptstrip_mangle_packet(skb, par, ip_hdrlen(skb), sizeof(struct iphdr) + sizeof(struct tcphdr)); } @@ -94,7 +105,7 @@ tcpoptstrip_tg6(struct sk_buff *skb, const struct xt_action_param *par) if (tcphoff < 0) return NF_DROP; - return tcpoptstrip_mangle_packet(skb, par->targinfo, tcphoff, + return tcpoptstrip_mangle_packet(skb, par, tcphoff, sizeof(*ipv6h) + sizeof(struct tcphdr)); } #endif |