[NETFILTER]: sip conntrack: better NAT handling

The NAT handling of the SIP helper has a few problems:

- Request headers are only mangled in the reply direction, From/To headers
  not at all, which can lead to authentication failures with DNAT in case
  the authentication domain is the IP address

- Contact headers in responses are only mangled for REGISTER responses

- Headers may be mangled even though they contain addresses not
  participating in the connection, like alternative addresses

- Packets are droppen when domain names are used where the helper expects
  IP addresses

This patch takes a different approach, instead of fixed rules what field
to mangle to what content, it adds symetric mapping of From/To/Via/Contact
headers, which allows to deal properly with echoed addresses in responses
and foreign addresses not belonging to the connection.

Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 27 insertions, 2 deletions

diff --git a/net/ipv4/netfilter/ip_conntrack_sip.c b/net/ipv4/netfilter/ip_conntrack_sip.c
index 0a6a13c45b0..3a26d63eed8 100644
--- a/net/ipv4/netfilter/ip_conntrack_sip.c
+++ b/net/ipv4/netfilter/ip_conntrack_sip.c
@@ -69,13 +69,38 @@ struct sip_header_nfo {
 };
 
 static struct sip_header_nfo ct_sip_hdrs[] = {
-	[POS_REQ_HEADER] = { 	/* SIP Requests headers */
+	[POS_REG_REQ_URI] = { 	/* SIP REGISTER request URI */
+		.lname		= "sip:",
+		.lnlen		= sizeof("sip:") - 1,
+		.ln_str		= ":",
+		.ln_strlen	= sizeof(":") - 1,
+		.match_len	= epaddr_len
+	},
+	[POS_REQ_URI] = { 	/* SIP request URI */
 		.lname		= "sip:",
 		.lnlen		= sizeof("sip:") - 1,
 		.ln_str		= "@",
 		.ln_strlen	= sizeof("@") - 1,
 		.match_len	= epaddr_len
 	},
+	[POS_FROM] = {		/* SIP From header */
+		.lname		= "From:",
+		.lnlen		= sizeof("From:") - 1,
+		.sname		= "\r\nf:",
+		.snlen		= sizeof("\r\nf:") - 1,
+		.ln_str		= "sip:",
+		.ln_strlen	= sizeof("sip:") - 1,
+		.match_len	= skp_epaddr_len,
+	},
+	[POS_TO] = {		/* SIP To header */
+		.lname		= "To:",
+		.lnlen		= sizeof("To:") - 1,
+		.sname		= "\r\nt:",
+		.snlen		= sizeof("\r\nt:") - 1,
+		.ln_str		= "sip:",
+		.ln_strlen	= sizeof("sip:") - 1,
+		.match_len	= skp_epaddr_len,
+	},
 	[POS_VIA] = { 		/* SIP Via header */
 		.lname		= "Via:",
 		.lnlen		= sizeof("Via:") - 1,
@@ -284,7 +309,7 @@ int ct_sip_get_info(const char *dptr, size_t dlen,
 
 	while (dptr <= limit) {
 		if ((strncmp(dptr, hnfo->lname, hnfo->lnlen) != 0) &&
-		    (hinfo->sname == NULL ||
+		    (hnfo->sname == NULL ||
 		     strncmp(dptr, hnfo->sname, hnfo->snlen) != 0)) {
 			dptr++;
 			continue;