| /* SIP extension for UDP NAT alteration. |
| * |
| * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar> |
| * based on RR's ip_nat_ftp.c and other modules. |
| * (C) 2007 United Security Providers |
| * (C) 2007, 2008 Patrick McHardy <kaber@trash.net> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <linux/ip.h> |
| #include <net/ip.h> |
| #include <linux/udp.h> |
| |
| #include <net/netfilter/nf_nat.h> |
| #include <net/netfilter/nf_nat_helper.h> |
| #include <net/netfilter/nf_nat_rule.h> |
| #include <net/netfilter/nf_conntrack_helper.h> |
| #include <net/netfilter/nf_conntrack_expect.h> |
| #include <linux/netfilter/nf_conntrack_sip.h> |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>"); |
| MODULE_DESCRIPTION("SIP NAT helper"); |
| MODULE_ALIAS("ip_nat_sip"); |
| |
| |
| static unsigned int mangle_packet(struct sk_buff *skb, |
| const char **dptr, unsigned int *datalen, |
| unsigned int matchoff, unsigned int matchlen, |
| const char *buffer, unsigned int buflen) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| |
| if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, matchoff, matchlen, |
| buffer, buflen)) |
| return 0; |
| |
| /* Reload data pointer and adjust datalen value */ |
| *dptr = skb->data + ip_hdrlen(skb) + sizeof(struct udphdr); |
| *datalen += buflen - matchlen; |
| return 1; |
| } |
| |
| static int map_addr(struct sk_buff *skb, |
| const char **dptr, unsigned int *datalen, |
| unsigned int matchoff, unsigned int matchlen, |
| union nf_inet_addr *addr, __be16 port) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); |
| char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; |
| unsigned int buflen; |
| __be32 newaddr; |
| __be16 newport; |
| |
| if (ct->tuplehash[dir].tuple.src.u3.ip == addr->ip && |
| ct->tuplehash[dir].tuple.src.u.udp.port == port) { |
| newaddr = ct->tuplehash[!dir].tuple.dst.u3.ip; |
| newport = ct->tuplehash[!dir].tuple.dst.u.udp.port; |
| } else if (ct->tuplehash[dir].tuple.dst.u3.ip == addr->ip && |
| ct->tuplehash[dir].tuple.dst.u.udp.port == port) { |
| newaddr = ct->tuplehash[!dir].tuple.src.u3.ip; |
| newport = ct->tuplehash[!dir].tuple.src.u.udp.port; |
| } else |
| return 1; |
| |
| if (newaddr == addr->ip && newport == port) |
| return 1; |
| |
| buflen = sprintf(buffer, "%pI4:%u", &newaddr, ntohs(newport)); |
| |
| return mangle_packet(skb, dptr, datalen, matchoff, matchlen, |
| buffer, buflen); |
| } |
| |
| static int map_sip_addr(struct sk_buff *skb, |
| const char **dptr, unsigned int *datalen, |
| enum sip_header_types type) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| unsigned int matchlen, matchoff; |
| union nf_inet_addr addr; |
| __be16 port; |
| |
| if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, type, NULL, |
| &matchoff, &matchlen, &addr, &port) <= 0) |
| return 1; |
| return map_addr(skb, dptr, datalen, matchoff, matchlen, &addr, port); |
| } |
| |
| static unsigned int ip_nat_sip(struct sk_buff *skb, |
| const char **dptr, unsigned int *datalen) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); |
| unsigned int dataoff, matchoff, matchlen; |
| union nf_inet_addr addr; |
| __be16 port; |
| int request, in_header; |
| |
| /* Basic rules: requests and responses. */ |
| if (strnicmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) { |
| if (ct_sip_parse_request(ct, *dptr, *datalen, |
| &matchoff, &matchlen, |
| &addr, &port) > 0 && |
| !map_addr(skb, dptr, datalen, matchoff, matchlen, |
| &addr, port)) |
| return NF_DROP; |
| request = 1; |
| } else |
| request = 0; |
| |
| /* Translate topmost Via header and parameters */ |
| if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, |
| SIP_HDR_VIA, NULL, &matchoff, &matchlen, |
| &addr, &port) > 0) { |
| unsigned int matchend, poff, plen, buflen, n; |
| char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; |
| |
| /* We're only interested in headers related to this |
| * connection */ |
| if (request) { |
| if (addr.ip != ct->tuplehash[dir].tuple.src.u3.ip || |
| port != ct->tuplehash[dir].tuple.src.u.udp.port) |
| goto next; |
| } else { |
| if (addr.ip != ct->tuplehash[dir].tuple.dst.u3.ip || |
| port != ct->tuplehash[dir].tuple.dst.u.udp.port) |
| goto next; |
| } |
| |
| if (!map_addr(skb, dptr, datalen, matchoff, matchlen, |
| &addr, port)) |
| return NF_DROP; |
| |
| matchend = matchoff + matchlen; |
| |
| /* The maddr= parameter (RFC 2361) specifies where to send |
| * the reply. */ |
| if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen, |
| "maddr=", &poff, &plen, |
| &addr) > 0 && |
| addr.ip == ct->tuplehash[dir].tuple.src.u3.ip && |
| addr.ip != ct->tuplehash[!dir].tuple.dst.u3.ip) { |
| buflen = sprintf(buffer, "%pI4", |
| &ct->tuplehash[!dir].tuple.dst.u3.ip); |
| if (!mangle_packet(skb, dptr, datalen, poff, plen, |
| buffer, buflen)) |
| return NF_DROP; |
| } |
| |
| /* The received= parameter (RFC 2361) contains the address |
| * from which the server received the request. */ |
| if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen, |
| "received=", &poff, &plen, |
| &addr) > 0 && |
| addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip && |
| addr.ip != ct->tuplehash[!dir].tuple.src.u3.ip) { |
| buflen = sprintf(buffer, "%pI4", |
| &ct->tuplehash[!dir].tuple.src.u3.ip); |
| if (!mangle_packet(skb, dptr, datalen, poff, plen, |
| buffer, buflen)) |
| return NF_DROP; |
| } |
| |
| /* The rport= parameter (RFC 3581) contains the port number |
| * from which the server received the request. */ |
| if (ct_sip_parse_numerical_param(ct, *dptr, matchend, *datalen, |
| "rport=", &poff, &plen, |
| &n) > 0 && |
| htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port && |
| htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) { |
| __be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port; |
| buflen = sprintf(buffer, "%u", ntohs(p)); |
| if (!mangle_packet(skb, dptr, datalen, poff, plen, |
| buffer, buflen)) |
| return NF_DROP; |
| } |
| } |
| |
| next: |
| /* Translate Contact headers */ |
| dataoff = 0; |
| in_header = 0; |
| while (ct_sip_parse_header_uri(ct, *dptr, &dataoff, *datalen, |
| SIP_HDR_CONTACT, &in_header, |
| &matchoff, &matchlen, |
| &addr, &port) > 0) { |
| if (!map_addr(skb, dptr, datalen, matchoff, matchlen, |
| &addr, port)) |
| return NF_DROP; |
| } |
| |
| if (!map_sip_addr(skb, dptr, datalen, SIP_HDR_FROM) || |
| !map_sip_addr(skb, dptr, datalen, SIP_HDR_TO)) |
| return NF_DROP; |
| return NF_ACCEPT; |
| } |
| |
| /* Handles expected signalling connections and media streams */ |
| static void ip_nat_sip_expected(struct nf_conn *ct, |
| struct nf_conntrack_expect *exp) |
| { |
| struct nf_nat_range range; |
| |
| /* This must be a fresh one. */ |
| BUG_ON(ct->status & IPS_NAT_DONE_MASK); |
| |
| /* For DST manip, map port here to where it's expected. */ |
| range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED); |
| range.min = range.max = exp->saved_proto; |
| range.min_ip = range.max_ip = exp->saved_ip; |
| nf_nat_setup_info(ct, &range, IP_NAT_MANIP_DST); |
| |
| /* Change src to where master sends to, but only if the connection |
| * actually came from the same source. */ |
| if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == |
| ct->master->tuplehash[exp->dir].tuple.src.u3.ip) { |
| range.flags = IP_NAT_RANGE_MAP_IPS; |
| range.min_ip = range.max_ip |
| = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip; |
| nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC); |
| } |
| } |
| |
| static unsigned int ip_nat_sip_expect(struct sk_buff *skb, |
| const char **dptr, unsigned int *datalen, |
| struct nf_conntrack_expect *exp, |
| unsigned int matchoff, |
| unsigned int matchlen) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); |
| __be32 newip; |
| u_int16_t port; |
| char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; |
| unsigned buflen; |
| |
| /* Connection will come from reply */ |
| if (ct->tuplehash[dir].tuple.src.u3.ip == ct->tuplehash[!dir].tuple.dst.u3.ip) |
| newip = exp->tuple.dst.u3.ip; |
| else |
| newip = ct->tuplehash[!dir].tuple.dst.u3.ip; |
| |
| /* If the signalling port matches the connection's source port in the |
| * original direction, try to use the destination port in the opposite |
| * direction. */ |
| if (exp->tuple.dst.u.udp.port == |
| ct->tuplehash[dir].tuple.src.u.udp.port) |
| port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port); |
| else |
| port = ntohs(exp->tuple.dst.u.udp.port); |
| |
| exp->saved_ip = exp->tuple.dst.u3.ip; |
| exp->tuple.dst.u3.ip = newip; |
| exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port; |
| exp->dir = !dir; |
| exp->expectfn = ip_nat_sip_expected; |
| |
| for (; port != 0; port++) { |
| exp->tuple.dst.u.udp.port = htons(port); |
| if (nf_ct_expect_related(exp) == 0) |
| break; |
| } |
| |
| if (port == 0) |
| return NF_DROP; |
| |
| if (exp->tuple.dst.u3.ip != exp->saved_ip || |
| exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) { |
| buflen = sprintf(buffer, "%pI4:%u", &newip, port); |
| if (!mangle_packet(skb, dptr, datalen, matchoff, matchlen, |
| buffer, buflen)) |
| goto err; |
| } |
| return NF_ACCEPT; |
| |
| err: |
| nf_ct_unexpect_related(exp); |
| return NF_DROP; |
| } |
| |
| static int mangle_content_len(struct sk_buff *skb, |
| const char **dptr, unsigned int *datalen) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| unsigned int matchoff, matchlen; |
| char buffer[sizeof("65536")]; |
| int buflen, c_len; |
| |
| /* Get actual SDP length */ |
| if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen, |
| SDP_HDR_VERSION, SDP_HDR_UNSPEC, |
| &matchoff, &matchlen) <= 0) |
| return 0; |
| c_len = *datalen - matchoff + strlen("v="); |
| |
| /* Now, update SDP length */ |
| if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH, |
| &matchoff, &matchlen) <= 0) |
| return 0; |
| |
| buflen = sprintf(buffer, "%u", c_len); |
| return mangle_packet(skb, dptr, datalen, matchoff, matchlen, |
| buffer, buflen); |
| } |
| |
| static int mangle_sdp_packet(struct sk_buff *skb, const char **dptr, |
| unsigned int dataoff, unsigned int *datalen, |
| enum sdp_header_types type, |
| enum sdp_header_types term, |
| char *buffer, int buflen) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| unsigned int matchlen, matchoff; |
| |
| if (ct_sip_get_sdp_header(ct, *dptr, dataoff, *datalen, type, term, |
| &matchoff, &matchlen) <= 0) |
| return -ENOENT; |
| return mangle_packet(skb, dptr, datalen, matchoff, matchlen, |
| buffer, buflen) ? 0 : -EINVAL; |
| } |
| |
| static unsigned int ip_nat_sdp_addr(struct sk_buff *skb, const char **dptr, |
| unsigned int dataoff, |
| unsigned int *datalen, |
| enum sdp_header_types type, |
| enum sdp_header_types term, |
| const union nf_inet_addr *addr) |
| { |
| char buffer[sizeof("nnn.nnn.nnn.nnn")]; |
| unsigned int buflen; |
| |
| buflen = sprintf(buffer, "%pI4", &addr->ip); |
| if (mangle_sdp_packet(skb, dptr, dataoff, datalen, type, term, |
| buffer, buflen)) |
| return 0; |
| |
| return mangle_content_len(skb, dptr, datalen); |
| } |
| |
| static unsigned int ip_nat_sdp_port(struct sk_buff *skb, |
| const char **dptr, |
| unsigned int *datalen, |
| unsigned int matchoff, |
| unsigned int matchlen, |
| u_int16_t port) |
| { |
| char buffer[sizeof("nnnnn")]; |
| unsigned int buflen; |
| |
| buflen = sprintf(buffer, "%u", port); |
| if (!mangle_packet(skb, dptr, datalen, matchoff, matchlen, |
| buffer, buflen)) |
| return 0; |
| |
| return mangle_content_len(skb, dptr, datalen); |
| } |
| |
| static unsigned int ip_nat_sdp_session(struct sk_buff *skb, const char **dptr, |
| unsigned int dataoff, |
| unsigned int *datalen, |
| const union nf_inet_addr *addr) |
| { |
| char buffer[sizeof("nnn.nnn.nnn.nnn")]; |
| unsigned int buflen; |
| |
| /* Mangle session description owner and contact addresses */ |
| buflen = sprintf(buffer, "%pI4", &addr->ip); |
| if (mangle_sdp_packet(skb, dptr, dataoff, datalen, |
| SDP_HDR_OWNER_IP4, SDP_HDR_MEDIA, |
| buffer, buflen)) |
| return 0; |
| |
| switch (mangle_sdp_packet(skb, dptr, dataoff, datalen, |
| SDP_HDR_CONNECTION_IP4, SDP_HDR_MEDIA, |
| buffer, buflen)) { |
| case 0: |
| /* |
| * RFC 2327: |
| * |
| * Session description |
| * |
| * c=* (connection information - not required if included in all media) |
| */ |
| case -ENOENT: |
| break; |
| default: |
| return 0; |
| } |
| |
| return mangle_content_len(skb, dptr, datalen); |
| } |
| |
| /* So, this packet has hit the connection tracking matching code. |
| Mangle it, and change the expectation to match the new version. */ |
| static unsigned int ip_nat_sdp_media(struct sk_buff *skb, |
| const char **dptr, |
| unsigned int *datalen, |
| struct nf_conntrack_expect *rtp_exp, |
| struct nf_conntrack_expect *rtcp_exp, |
| unsigned int mediaoff, |
| unsigned int medialen, |
| union nf_inet_addr *rtp_addr) |
| { |
| enum ip_conntrack_info ctinfo; |
| struct nf_conn *ct = nf_ct_get(skb, &ctinfo); |
| enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); |
| u_int16_t port; |
| |
| /* Connection will come from reply */ |
| if (ct->tuplehash[dir].tuple.src.u3.ip == |
| ct->tuplehash[!dir].tuple.dst.u3.ip) |
| rtp_addr->ip = rtp_exp->tuple.dst.u3.ip; |
| else |
| rtp_addr->ip = ct->tuplehash[!dir].tuple.dst.u3.ip; |
| |
| rtp_exp->saved_ip = rtp_exp->tuple.dst.u3.ip; |
| rtp_exp->tuple.dst.u3.ip = rtp_addr->ip; |
| rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port; |
| rtp_exp->dir = !dir; |
| rtp_exp->expectfn = ip_nat_sip_expected; |
| |
| rtcp_exp->saved_ip = rtcp_exp->tuple.dst.u3.ip; |
| rtcp_exp->tuple.dst.u3.ip = rtp_addr->ip; |
| rtcp_exp->saved_proto.udp.port = rtcp_exp->tuple.dst.u.udp.port; |
| rtcp_exp->dir = !dir; |
| rtcp_exp->expectfn = ip_nat_sip_expected; |
| |
| /* Try to get same pair of ports: if not, try to change them. */ |
| for (port = ntohs(rtp_exp->tuple.dst.u.udp.port); |
| port != 0; port += 2) { |
| rtp_exp->tuple.dst.u.udp.port = htons(port); |
| if (nf_ct_expect_related(rtp_exp) != 0) |
| continue; |
| rtcp_exp->tuple.dst.u.udp.port = htons(port + 1); |
| if (nf_ct_expect_related(rtcp_exp) == 0) |
| break; |
| nf_ct_unexpect_related(rtp_exp); |
| } |
| |
| if (port == 0) |
| goto err1; |
| |
| /* Update media port. */ |
| if (rtp_exp->tuple.dst.u.udp.port != rtp_exp->saved_proto.udp.port && |
| !ip_nat_sdp_port(skb, dptr, datalen, mediaoff, medialen, port)) |
| goto err2; |
| |
| return NF_ACCEPT; |
| |
| err2: |
| nf_ct_unexpect_related(rtp_exp); |
| nf_ct_unexpect_related(rtcp_exp); |
| err1: |
| return NF_DROP; |
| } |
| |
| static void __exit nf_nat_sip_fini(void) |
| { |
| rcu_assign_pointer(nf_nat_sip_hook, NULL); |
| rcu_assign_pointer(nf_nat_sip_expect_hook, NULL); |
| rcu_assign_pointer(nf_nat_sdp_addr_hook, NULL); |
| rcu_assign_pointer(nf_nat_sdp_port_hook, NULL); |
| rcu_assign_pointer(nf_nat_sdp_session_hook, NULL); |
| rcu_assign_pointer(nf_nat_sdp_media_hook, NULL); |
| synchronize_rcu(); |
| } |
| |
| static int __init nf_nat_sip_init(void) |
| { |
| BUG_ON(nf_nat_sip_hook != NULL); |
| BUG_ON(nf_nat_sip_expect_hook != NULL); |
| BUG_ON(nf_nat_sdp_addr_hook != NULL); |
| BUG_ON(nf_nat_sdp_port_hook != NULL); |
| BUG_ON(nf_nat_sdp_session_hook != NULL); |
| BUG_ON(nf_nat_sdp_media_hook != NULL); |
| rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip); |
| rcu_assign_pointer(nf_nat_sip_expect_hook, ip_nat_sip_expect); |
| rcu_assign_pointer(nf_nat_sdp_addr_hook, ip_nat_sdp_addr); |
| rcu_assign_pointer(nf_nat_sdp_port_hook, ip_nat_sdp_port); |
| rcu_assign_pointer(nf_nat_sdp_session_hook, ip_nat_sdp_session); |
| rcu_assign_pointer(nf_nat_sdp_media_hook, ip_nat_sdp_media); |
| return 0; |
| } |
| |
| module_init(nf_nat_sip_init); |
| module_exit(nf_nat_sip_fini); |