[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>

diff --git a/include/linux/netfilter_ipv4/ip_conntrack_sip.h b/include/linux/netfilter_ipv4/ip_conntrack_sip.h
index 51c65ac..bef6c64 100644 (file)
--- a/include/linux/netfilter_ipv4/ip_conntrack_sip.h
+++ b/include/linux/netfilter_ipv4/ip_conntrack_sip.h
@@ -6,7 +6,10 @@
 #define SIP_TIMEOUT    3600
 
 enum sip_header_pos {
-       POS_REQ_HEADER,
+       POS_REG_REQ_URI,
+       POS_REQ_URI,
+       POS_FROM,
+       POS_TO,
        POS_VIA,
        POS_CONTACT,
        POS_CONTENT,

diff --git a/net/ipv4/netfilter/ip_conntrack_sip.c b/net/ipv4/netfilter/ip_conntrack_sip.c
index 0a6a13c..3a26d63 100644 (file)
--- 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;

diff --git a/net/ipv4/netfilter/ip_nat_sip.c b/net/ipv4/netfilter/ip_nat_sip.c
index e16604c..6223abc 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_sip.c
+++ b/net/ipv4/netfilter/ip_nat_sip.c
@@ -29,25 +29,70 @@ MODULE_DESCRIPTION("SIP NAT helper");
 #define DEBUGP(format, args...)
 #endif
 
-static unsigned int mangle_sip_packet(struct sk_buff **pskb,
-                                     enum ip_conntrack_info ctinfo,
-                                     struct ip_conntrack *ct,
-                                     const char **dptr, size_t dlen,
-                                     char *buffer, int bufflen,
-                                     enum sip_header_pos pos)
+struct addr_map {
+       struct {
+               char            src[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
+               char            dst[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
+               unsigned int    srclen, srciplen;
+               unsigned int    dstlen, dstiplen;
+       } addr[IP_CT_DIR_MAX];
+};
+
+static void addr_map_init(struct ip_conntrack *ct, struct addr_map *map)
 {
-       unsigned int matchlen, matchoff;
+       struct ip_conntrack_tuple *t;
+       enum ip_conntrack_dir dir;
+       unsigned int n;
+
+       for (dir = 0; dir < IP_CT_DIR_MAX; dir++) {
+               t = &ct->tuplehash[dir].tuple;
+
+               n = sprintf(map->addr[dir].src, "%u.%u.%u.%u",
+                           NIPQUAD(t->src.ip));
+               map->addr[dir].srciplen = n;
+               n += sprintf(map->addr[dir].src + n, ":%u",
+                            ntohs(t->src.u.udp.port));
+               map->addr[dir].srclen = n;
+
+               n = sprintf(map->addr[dir].dst, "%u.%u.%u.%u",
+                           NIPQUAD(t->dst.ip));
+               map->addr[dir].dstiplen = n;
+               n += sprintf(map->addr[dir].dst + n, ":%u",
+                            ntohs(t->dst.u.udp.port));
+               map->addr[dir].dstlen = n;
+       }
+}
+
+static int map_sip_addr(struct sk_buff **pskb, enum ip_conntrack_info ctinfo,
+                       struct ip_conntrack *ct, const char **dptr, size_t dlen,
+                       enum sip_header_pos pos, struct addr_map *map)
+{
+       enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+       unsigned int matchlen, matchoff, addrlen;
+       char *addr;
 
        if (ct_sip_get_info(*dptr, dlen, &matchoff, &matchlen, pos) <= 0)
-               return 0;
+               return 1;
+
+       if ((matchlen == map->addr[dir].srciplen ||
+            matchlen == map->addr[dir].srclen) &&
+           memcmp(*dptr + matchoff, map->addr[dir].src, matchlen) == 0) {
+               addr    = map->addr[!dir].dst;
+               addrlen = map->addr[!dir].dstlen;
+       } else if ((matchlen == map->addr[dir].dstiplen ||
+                   matchlen == map->addr[dir].dstlen) &&
+                  memcmp(*dptr + matchoff, map->addr[dir].dst, matchlen) == 0) {
+               addr    = map->addr[!dir].src;
+               addrlen = map->addr[!dir].srclen;
+       } else
+               return 1;
 
        if (!ip_nat_mangle_udp_packet(pskb, ct, ctinfo,
-                                     matchoff, matchlen, buffer, bufflen))
+                                     matchoff, matchlen, addr, addrlen))
                return 0;
-
-       /* We need to reload this. Thanks Patrick. */
        *dptr = (*pskb)->data + (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
        return 1;
+
 }
 
 static unsigned int ip_nat_sip(struct sk_buff **pskb,
@@ -55,69 +100,61 @@ static unsigned int ip_nat_sip(struct sk_buff **pskb,
                               struct ip_conntrack *ct,
                               const char **dptr)
 {
-       enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
-       char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
-       unsigned int bufflen, dataoff;
-       __be32 ip;
-       __be16 port;
+       enum sip_header_pos pos;
+       struct addr_map map;
+       int dataoff, datalen;
 
        dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+       datalen = (*pskb)->len - dataoff;
+       if (datalen < sizeof("SIP/2.0") - 1)
+               return NF_DROP;
+
+       addr_map_init(ct, &map);
+
+       /* Basic rules: requests and responses. */
+       if (strncmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) != 0) {
+               /* 10.2: Constructing the REGISTER Request:
+                *
+                * The "userinfo" and "@" components of the SIP URI MUST NOT
+                * be present.
+                */
+               if (datalen >= sizeof("REGISTER") - 1 &&
+                   strncmp(*dptr, "REGISTER", sizeof("REGISTER") - 1) == 0)
+                       pos = POS_REG_REQ_URI;
+               else
+                       pos = POS_REQ_URI;
+
+               if (!map_sip_addr(pskb, ctinfo, ct, dptr, datalen, pos, &map))
+                       return NF_DROP;
+       }
 
-       ip   = ct->tuplehash[!dir].tuple.dst.ip;
-       port = ct->tuplehash[!dir].tuple.dst.u.udp.port;
-       bufflen = sprintf(buffer, "%u.%u.%u.%u:%u", NIPQUAD(ip), ntohs(port));
+       if (!map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_FROM, &map) ||
+           !map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_TO, &map) ||
+           !map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_VIA, &map) ||
+           !map_sip_addr(pskb, ctinfo, ct, dptr, datalen, POS_CONTACT, &map))
+               return NF_DROP;
+       return NF_ACCEPT;
+}
+
+static unsigned int mangle_sip_packet(struct sk_buff **pskb,
+                                     enum ip_conntrack_info ctinfo,
+                                     struct ip_conntrack *ct,
+                                     const char **dptr, size_t dlen,
+                                     char *buffer, int bufflen,
+                                     enum sip_header_pos pos)
+{
+       unsigned int matchlen, matchoff;
 
-       /* short packet ? */
-       if (((*pskb)->len - dataoff) < (sizeof("SIP/2.0") - 1))
+       if (ct_sip_get_info(*dptr, dlen, &matchoff, &matchlen, pos) <= 0)
                return 0;
 
-       /* Basic rules: requests and responses. */
-       if (memcmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) == 0) {
-               const char *aux;
-
-               if ((ctinfo) < IP_CT_IS_REPLY) {
-                       mangle_sip_packet(pskb, ctinfo, ct, dptr,
-                                         (*pskb)->len - dataoff,
-                                         buffer, bufflen, POS_CONTACT);
-                       return 1;
-               }
+       if (!ip_nat_mangle_udp_packet(pskb, ct, ctinfo,
+                                     matchoff, matchlen, buffer, bufflen))
+               return 0;
 
-               if (!mangle_sip_packet(pskb, ctinfo, ct, dptr,
-                                      (*pskb)->len - dataoff,
-                                      buffer, bufflen, POS_VIA))
-                       return 0;
-
-               aux = ct_sip_search("CSeq:", *dptr, sizeof("CSeq:") - 1,
-                                   (*pskb)->len - dataoff, 0);
-               if (!aux)
-                       return 0;
-
-               if (!ct_sip_search("REGISTER", aux, sizeof("REGISTER"),
-                                  ct_sip_lnlen(aux,
-                                               *dptr + (*pskb)->len - dataoff),
-                                  1))
-                       return 1;
-
-               return mangle_sip_packet(pskb, ctinfo, ct, dptr,
-                                        (*pskb)->len - dataoff,
-                                        buffer, bufflen, POS_CONTACT);
-       }
-       if ((ctinfo) < IP_CT_IS_REPLY) {
-               if (!mangle_sip_packet(pskb, ctinfo, ct, dptr,
-                                      (*pskb)->len - dataoff,
-                                      buffer, bufflen, POS_VIA))
-                       return 0;
-
-               /* Mangle Contact if exists only. - watch udp_nat_mangle()! */
-               mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff,
-                                 buffer, bufflen, POS_CONTACT);
-               return 1;
-       }
-       /* This mangle requests headers. */
-       return mangle_sip_packet(pskb, ctinfo, ct, dptr,
-                                ct_sip_lnlen(*dptr,
-                                             *dptr + (*pskb)->len - dataoff),
-                                buffer, bufflen, POS_REQ_HEADER);
+       /* We need to reload this. Thanks Patrick. */
+       *dptr = (*pskb)->data + (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+       return 1;
 }
 
 static int mangle_content_len(struct sk_buff **pskb,