![Eric Dumazet](/assets/img/avatar_default.png)
Use of "unsigned int" is preferred to bare "unsigned" in net tree. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
569 lines
17 KiB
C
569 lines
17 KiB
C
/* SIP extension for NAT alteration.
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*
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* (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
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* based on RR's ip_nat_ftp.c and other modules.
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* (C) 2007 United Security Providers
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* (C) 2007, 2008 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/ip.h>
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#include <net/ip.h>
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#include <linux/udp.h>
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#include <linux/tcp.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_helper.h>
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#include <net/netfilter/nf_nat_rule.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#include <linux/netfilter/nf_conntrack_sip.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
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MODULE_DESCRIPTION("SIP NAT helper");
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MODULE_ALIAS("ip_nat_sip");
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static unsigned int mangle_packet(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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unsigned int matchoff, unsigned int matchlen,
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const char *buffer, unsigned int buflen)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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struct tcphdr *th;
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unsigned int baseoff;
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if (nf_ct_protonum(ct) == IPPROTO_TCP) {
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th = (struct tcphdr *)(skb->data + ip_hdrlen(skb));
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baseoff = ip_hdrlen(skb) + th->doff * 4;
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matchoff += dataoff - baseoff;
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if (!__nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
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matchoff, matchlen,
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buffer, buflen, false))
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return 0;
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} else {
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baseoff = ip_hdrlen(skb) + sizeof(struct udphdr);
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matchoff += dataoff - baseoff;
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if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo,
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matchoff, matchlen,
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buffer, buflen))
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return 0;
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}
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/* Reload data pointer and adjust datalen value */
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*dptr = skb->data + dataoff;
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*datalen += buflen - matchlen;
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return 1;
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}
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static int map_addr(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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unsigned int matchoff, unsigned int matchlen,
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union nf_inet_addr *addr, __be16 port)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
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unsigned int buflen;
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__be32 newaddr;
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__be16 newport;
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if (ct->tuplehash[dir].tuple.src.u3.ip == addr->ip &&
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ct->tuplehash[dir].tuple.src.u.udp.port == port) {
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newaddr = ct->tuplehash[!dir].tuple.dst.u3.ip;
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newport = ct->tuplehash[!dir].tuple.dst.u.udp.port;
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} else if (ct->tuplehash[dir].tuple.dst.u3.ip == addr->ip &&
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ct->tuplehash[dir].tuple.dst.u.udp.port == port) {
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newaddr = ct->tuplehash[!dir].tuple.src.u3.ip;
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newport = ct->tuplehash[!dir].tuple.src.u.udp.port;
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} else
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return 1;
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if (newaddr == addr->ip && newport == port)
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return 1;
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buflen = sprintf(buffer, "%pI4:%u", &newaddr, ntohs(newport));
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return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
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buffer, buflen);
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}
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static int map_sip_addr(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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enum sip_header_types type)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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unsigned int matchlen, matchoff;
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union nf_inet_addr addr;
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__be16 port;
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if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, type, NULL,
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&matchoff, &matchlen, &addr, &port) <= 0)
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return 1;
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return map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
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&addr, port);
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}
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static unsigned int ip_nat_sip(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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unsigned int coff, matchoff, matchlen;
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enum sip_header_types hdr;
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union nf_inet_addr addr;
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__be16 port;
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int request, in_header;
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/* Basic rules: requests and responses. */
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if (strnicmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) {
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if (ct_sip_parse_request(ct, *dptr, *datalen,
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&matchoff, &matchlen,
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&addr, &port) > 0 &&
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!map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
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&addr, port))
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return NF_DROP;
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request = 1;
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} else
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request = 0;
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if (nf_ct_protonum(ct) == IPPROTO_TCP)
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hdr = SIP_HDR_VIA_TCP;
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else
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hdr = SIP_HDR_VIA_UDP;
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/* Translate topmost Via header and parameters */
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if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen,
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hdr, NULL, &matchoff, &matchlen,
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&addr, &port) > 0) {
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unsigned int matchend, poff, plen, buflen, n;
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char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
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/* We're only interested in headers related to this
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* connection */
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if (request) {
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if (addr.ip != ct->tuplehash[dir].tuple.src.u3.ip ||
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port != ct->tuplehash[dir].tuple.src.u.udp.port)
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goto next;
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} else {
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if (addr.ip != ct->tuplehash[dir].tuple.dst.u3.ip ||
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port != ct->tuplehash[dir].tuple.dst.u.udp.port)
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goto next;
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}
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if (!map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
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&addr, port))
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return NF_DROP;
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matchend = matchoff + matchlen;
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/* The maddr= parameter (RFC 2361) specifies where to send
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* the reply. */
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if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
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"maddr=", &poff, &plen,
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&addr) > 0 &&
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addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
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addr.ip != ct->tuplehash[!dir].tuple.dst.u3.ip) {
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buflen = sprintf(buffer, "%pI4",
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&ct->tuplehash[!dir].tuple.dst.u3.ip);
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if (!mangle_packet(skb, dataoff, dptr, datalen,
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poff, plen, buffer, buflen))
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return NF_DROP;
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}
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/* The received= parameter (RFC 2361) contains the address
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* from which the server received the request. */
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if (ct_sip_parse_address_param(ct, *dptr, matchend, *datalen,
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"received=", &poff, &plen,
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&addr) > 0 &&
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addr.ip == ct->tuplehash[dir].tuple.dst.u3.ip &&
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addr.ip != ct->tuplehash[!dir].tuple.src.u3.ip) {
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buflen = sprintf(buffer, "%pI4",
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&ct->tuplehash[!dir].tuple.src.u3.ip);
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if (!mangle_packet(skb, dataoff, dptr, datalen,
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poff, plen, buffer, buflen))
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return NF_DROP;
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}
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/* The rport= parameter (RFC 3581) contains the port number
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* from which the server received the request. */
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if (ct_sip_parse_numerical_param(ct, *dptr, matchend, *datalen,
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"rport=", &poff, &plen,
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&n) > 0 &&
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htons(n) == ct->tuplehash[dir].tuple.dst.u.udp.port &&
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htons(n) != ct->tuplehash[!dir].tuple.src.u.udp.port) {
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__be16 p = ct->tuplehash[!dir].tuple.src.u.udp.port;
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buflen = sprintf(buffer, "%u", ntohs(p));
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if (!mangle_packet(skb, dataoff, dptr, datalen,
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poff, plen, buffer, buflen))
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return NF_DROP;
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}
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}
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next:
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/* Translate Contact headers */
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coff = 0;
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in_header = 0;
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while (ct_sip_parse_header_uri(ct, *dptr, &coff, *datalen,
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SIP_HDR_CONTACT, &in_header,
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&matchoff, &matchlen,
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&addr, &port) > 0) {
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if (!map_addr(skb, dataoff, dptr, datalen, matchoff, matchlen,
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&addr, port))
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return NF_DROP;
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}
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if (!map_sip_addr(skb, dataoff, dptr, datalen, SIP_HDR_FROM) ||
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!map_sip_addr(skb, dataoff, dptr, datalen, SIP_HDR_TO))
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return NF_DROP;
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return NF_ACCEPT;
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}
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static void ip_nat_sip_seq_adjust(struct sk_buff *skb, s16 off)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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const struct tcphdr *th;
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if (nf_ct_protonum(ct) != IPPROTO_TCP || off == 0)
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return;
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th = (struct tcphdr *)(skb->data + ip_hdrlen(skb));
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nf_nat_set_seq_adjust(ct, ctinfo, th->seq, off);
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}
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/* Handles expected signalling connections and media streams */
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static void ip_nat_sip_expected(struct nf_conn *ct,
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struct nf_conntrack_expect *exp)
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{
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struct nf_nat_ipv4_range range;
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/* This must be a fresh one. */
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BUG_ON(ct->status & IPS_NAT_DONE_MASK);
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/* For DST manip, map port here to where it's expected. */
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range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED);
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range.min = range.max = exp->saved_proto;
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range.min_ip = range.max_ip = exp->saved_ip;
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nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
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/* Change src to where master sends to, but only if the connection
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* actually came from the same source. */
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if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip ==
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ct->master->tuplehash[exp->dir].tuple.src.u3.ip) {
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range.flags = NF_NAT_RANGE_MAP_IPS;
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range.min_ip = range.max_ip
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= ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip;
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nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
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}
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}
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static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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struct nf_conntrack_expect *exp,
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unsigned int matchoff,
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unsigned int matchlen)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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__be32 newip;
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u_int16_t port;
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char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
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unsigned int buflen;
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/* Connection will come from reply */
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if (ct->tuplehash[dir].tuple.src.u3.ip == ct->tuplehash[!dir].tuple.dst.u3.ip)
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newip = exp->tuple.dst.u3.ip;
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else
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newip = ct->tuplehash[!dir].tuple.dst.u3.ip;
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/* If the signalling port matches the connection's source port in the
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* original direction, try to use the destination port in the opposite
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* direction. */
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if (exp->tuple.dst.u.udp.port ==
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ct->tuplehash[dir].tuple.src.u.udp.port)
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port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
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else
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port = ntohs(exp->tuple.dst.u.udp.port);
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exp->saved_ip = exp->tuple.dst.u3.ip;
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exp->tuple.dst.u3.ip = newip;
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exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port;
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exp->dir = !dir;
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exp->expectfn = ip_nat_sip_expected;
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for (; port != 0; port++) {
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int ret;
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exp->tuple.dst.u.udp.port = htons(port);
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ret = nf_ct_expect_related(exp);
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if (ret == 0)
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break;
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else if (ret != -EBUSY) {
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port = 0;
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break;
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}
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}
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if (port == 0)
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return NF_DROP;
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if (exp->tuple.dst.u3.ip != exp->saved_ip ||
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exp->tuple.dst.u.udp.port != exp->saved_proto.udp.port) {
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buflen = sprintf(buffer, "%pI4:%u", &newip, port);
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if (!mangle_packet(skb, dataoff, dptr, datalen,
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matchoff, matchlen, buffer, buflen))
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goto err;
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}
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return NF_ACCEPT;
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err:
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nf_ct_unexpect_related(exp);
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return NF_DROP;
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}
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static int mangle_content_len(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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unsigned int matchoff, matchlen;
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char buffer[sizeof("65536")];
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int buflen, c_len;
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/* Get actual SDP length */
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if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen,
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SDP_HDR_VERSION, SDP_HDR_UNSPEC,
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&matchoff, &matchlen) <= 0)
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return 0;
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c_len = *datalen - matchoff + strlen("v=");
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/* Now, update SDP length */
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if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CONTENT_LENGTH,
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&matchoff, &matchlen) <= 0)
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return 0;
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buflen = sprintf(buffer, "%u", c_len);
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return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
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buffer, buflen);
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}
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static int mangle_sdp_packet(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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unsigned int sdpoff,
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enum sdp_header_types type,
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enum sdp_header_types term,
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char *buffer, int buflen)
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{
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enum ip_conntrack_info ctinfo;
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struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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unsigned int matchlen, matchoff;
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if (ct_sip_get_sdp_header(ct, *dptr, sdpoff, *datalen, type, term,
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&matchoff, &matchlen) <= 0)
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return -ENOENT;
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return mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
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buffer, buflen) ? 0 : -EINVAL;
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}
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static unsigned int ip_nat_sdp_addr(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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unsigned int sdpoff,
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enum sdp_header_types type,
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enum sdp_header_types term,
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const union nf_inet_addr *addr)
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{
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char buffer[sizeof("nnn.nnn.nnn.nnn")];
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unsigned int buflen;
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buflen = sprintf(buffer, "%pI4", &addr->ip);
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if (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff, type, term,
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buffer, buflen))
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return 0;
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return mangle_content_len(skb, dataoff, dptr, datalen);
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}
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|
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static unsigned int ip_nat_sdp_port(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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unsigned int matchoff,
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unsigned int matchlen,
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u_int16_t port)
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{
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char buffer[sizeof("nnnnn")];
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unsigned int buflen;
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buflen = sprintf(buffer, "%u", port);
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if (!mangle_packet(skb, dataoff, dptr, datalen, matchoff, matchlen,
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buffer, buflen))
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return 0;
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return mangle_content_len(skb, dataoff, dptr, datalen);
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}
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|
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static unsigned int ip_nat_sdp_session(struct sk_buff *skb, unsigned int dataoff,
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const char **dptr, unsigned int *datalen,
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unsigned int sdpoff,
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const union nf_inet_addr *addr)
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{
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char buffer[sizeof("nnn.nnn.nnn.nnn")];
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unsigned int buflen;
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/* Mangle session description owner and contact addresses */
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buflen = sprintf(buffer, "%pI4", &addr->ip);
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if (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff,
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SDP_HDR_OWNER_IP4, SDP_HDR_MEDIA,
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buffer, buflen))
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return 0;
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|
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switch (mangle_sdp_packet(skb, dataoff, dptr, datalen, sdpoff,
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SDP_HDR_CONNECTION_IP4, SDP_HDR_MEDIA,
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buffer, buflen)) {
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case 0:
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/*
|
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* RFC 2327:
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*
|
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* Session description
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*
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* c=* (connection information - not required if included in all media)
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*/
|
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case -ENOENT:
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break;
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default:
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return 0;
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}
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|
|
|
return mangle_content_len(skb, dataoff, 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, unsigned int dataoff,
|
|
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) {
|
|
int ret;
|
|
|
|
rtp_exp->tuple.dst.u.udp.port = htons(port);
|
|
ret = nf_ct_expect_related(rtp_exp);
|
|
if (ret == -EBUSY)
|
|
continue;
|
|
else if (ret < 0) {
|
|
port = 0;
|
|
break;
|
|
}
|
|
rtcp_exp->tuple.dst.u.udp.port = htons(port + 1);
|
|
ret = nf_ct_expect_related(rtcp_exp);
|
|
if (ret == 0)
|
|
break;
|
|
else if (ret != -EBUSY) {
|
|
nf_ct_unexpect_related(rtp_exp);
|
|
port = 0;
|
|
break;
|
|
}
|
|
}
|
|
|
|
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, dataoff, 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 struct nf_ct_helper_expectfn sip_nat = {
|
|
.name = "sip",
|
|
.expectfn = ip_nat_sip_expected,
|
|
};
|
|
|
|
static void __exit nf_nat_sip_fini(void)
|
|
{
|
|
RCU_INIT_POINTER(nf_nat_sip_hook, NULL);
|
|
RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, NULL);
|
|
RCU_INIT_POINTER(nf_nat_sip_expect_hook, NULL);
|
|
RCU_INIT_POINTER(nf_nat_sdp_addr_hook, NULL);
|
|
RCU_INIT_POINTER(nf_nat_sdp_port_hook, NULL);
|
|
RCU_INIT_POINTER(nf_nat_sdp_session_hook, NULL);
|
|
RCU_INIT_POINTER(nf_nat_sdp_media_hook, NULL);
|
|
nf_ct_helper_expectfn_unregister(&sip_nat);
|
|
synchronize_rcu();
|
|
}
|
|
|
|
static int __init nf_nat_sip_init(void)
|
|
{
|
|
BUG_ON(nf_nat_sip_hook != NULL);
|
|
BUG_ON(nf_nat_sip_seq_adjust_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_INIT_POINTER(nf_nat_sip_hook, ip_nat_sip);
|
|
RCU_INIT_POINTER(nf_nat_sip_seq_adjust_hook, ip_nat_sip_seq_adjust);
|
|
RCU_INIT_POINTER(nf_nat_sip_expect_hook, ip_nat_sip_expect);
|
|
RCU_INIT_POINTER(nf_nat_sdp_addr_hook, ip_nat_sdp_addr);
|
|
RCU_INIT_POINTER(nf_nat_sdp_port_hook, ip_nat_sdp_port);
|
|
RCU_INIT_POINTER(nf_nat_sdp_session_hook, ip_nat_sdp_session);
|
|
RCU_INIT_POINTER(nf_nat_sdp_media_hook, ip_nat_sdp_media);
|
|
nf_ct_helper_expectfn_register(&sip_nat);
|
|
return 0;
|
|
}
|
|
|
|
module_init(nf_nat_sip_init);
|
|
module_exit(nf_nat_sip_fini);
|