netfilter: nf_ct_sip: fix SDP parsing in TCP SIP messages for some Cisco phones

Some Cisco phones do not place the Content-Length field at the end of the
SIP message. This is valid, due to a misunderstanding of the specification
the parser expects the SDP body to start directly after the Content-Length
field. Fix the parser to scan for \r\n\r\n to locate the beginning of the
SDP body.

Reported-by: Teresa Kang <teresa_kang@gemtek.com.tw>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index 1f81abde131fc64b7af2d3ee325077f3884e72e7..c05c0dc33499ce87b2f817935e168db93f6f0fcc 100644 (file)
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -1419,6 +1419,7 @@ static int sip_help_tcp(struct sk_buff *skb, unsigned int protoff,
        const char *dptr, *end;
        s16 diff, tdiff = 0;
        int ret = NF_ACCEPT;
+       bool term;
        typeof(nf_nat_sip_seq_adjust_hook) nf_nat_sip_seq_adjust;
 
        if (ctinfo != IP_CT_ESTABLISHED &&
@@ -1453,10 +1454,15 @@ static int sip_help_tcp(struct sk_buff *skb, unsigned int protoff,
                if (dptr + matchoff == end)
                        break;
 
-               if (end + strlen("\r\n\r\n") > dptr + datalen)
-                       break;
-               if (end[0] != '\r' || end[1] != '\n' ||
-                   end[2] != '\r' || end[3] != '\n')
+               term = false;
+               for (; end + strlen("\r\n\r\n") <= dptr + datalen; end++) {
+                       if (end[0] == '\r' && end[1] == '\n' &&
+                           end[2] == '\r' && end[3] == '\n') {
+                               term = true;
+                               break;
+                       }
+               }
+               if (!term)
                        break;
                end += strlen("\r\n\r\n") + clen;