/* SIP extension for IP connection tracking. * * (C) 2005 by Christian Hentschel * based on RR's ip_conntrack_ftp.c and other modules. * (C) 2007 United Security Providers * (C) 2007, 2008 Patrick McHardy * * 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 #include #include #include #include #include #include #include #include #include #include #include MODULE_LICENSE("GPL"); MODULE_AUTHOR("Christian Hentschel "); MODULE_DESCRIPTION("SIP connection tracking helper"); MODULE_ALIAS("ip_conntrack_sip"); #define MAX_PORTS 8 static unsigned short ports[MAX_PORTS]; static unsigned int ports_c; module_param_array(ports, ushort, &ports_c, 0400); MODULE_PARM_DESC(ports, "port numbers of SIP servers"); static unsigned int sip_timeout __read_mostly = SIP_TIMEOUT; module_param(sip_timeout, uint, 0600); MODULE_PARM_DESC(sip_timeout, "timeout for the master SIP session"); static int sip_direct_signalling __read_mostly = 1; module_param(sip_direct_signalling, int, 0600); MODULE_PARM_DESC(sip_direct_signalling, "expect incoming calls from registrar " "only (default 1)"); static int sip_direct_media __read_mostly = 1; module_param(sip_direct_media, int, 0600); MODULE_PARM_DESC(sip_direct_media, "Expect Media streams between signalling " "endpoints only (default 1)"); unsigned int (*nf_nat_sip_hook)(struct sk_buff *skb, const char **dptr, unsigned int *datalen) __read_mostly; EXPORT_SYMBOL_GPL(nf_nat_sip_hook); unsigned int (*nf_nat_sip_expect_hook)(struct sk_buff *skb, const char **dptr, unsigned int *datalen, struct nf_conntrack_expect *exp, unsigned int matchoff, unsigned int matchlen) __read_mostly; EXPORT_SYMBOL_GPL(nf_nat_sip_expect_hook); unsigned int (*nf_nat_sdp_addr_hook)(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) __read_mostly; EXPORT_SYMBOL_GPL(nf_nat_sdp_addr_hook); unsigned int (*nf_nat_sdp_port_hook)(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int matchoff, unsigned int matchlen, u_int16_t port) __read_mostly; EXPORT_SYMBOL_GPL(nf_nat_sdp_port_hook); unsigned int (*nf_nat_sdp_session_hook)(struct sk_buff *skb, const char **dptr, unsigned int dataoff, unsigned int *datalen, const union nf_inet_addr *addr) __read_mostly; EXPORT_SYMBOL_GPL(nf_nat_sdp_session_hook); unsigned int (*nf_nat_sdp_media_hook)(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) __read_mostly; EXPORT_SYMBOL_GPL(nf_nat_sdp_media_hook); static int string_len(const struct nf_conn *ct, const char *dptr, const char *limit, int *shift) { int len = 0; while (dptr < limit && isalpha(*dptr)) { dptr++; len++; } return len; } static int digits_len(const struct nf_conn *ct, const char *dptr, const char *limit, int *shift) { int len = 0; while (dptr < limit && isdigit(*dptr)) { dptr++; len++; } return len; } /* get media type + port length */ static int media_len(const struct nf_conn *ct, const char *dptr, const char *limit, int *shift) { int len = string_len(ct, dptr, limit, shift); dptr += len; if (dptr >= limit || *dptr != ' ') return 0; len++; dptr++; return len + digits_len(ct, dptr, limit, shift); } static int parse_addr(const struct nf_conn *ct, const char *cp, const char **endp, union nf_inet_addr *addr, const char *limit) { const char *end; int ret = 0; memset(addr, 0, sizeof(*addr)); switch (nf_ct_l3num(ct)) { case AF_INET: ret = in4_pton(cp, limit - cp, (u8 *)&addr->ip, -1, &end); break; case AF_INET6: ret = in6_pton(cp, limit - cp, (u8 *)&addr->ip6, -1, &end); break; default: BUG(); } if (ret == 0 || end == cp) return 0; if (endp) *endp = end; return 1; } /* skip ip address. returns its length. */ static int epaddr_len(const struct nf_conn *ct, const char *dptr, const char *limit, int *shift) { union nf_inet_addr addr; const char *aux = dptr; if (!parse_addr(ct, dptr, &dptr, &addr, limit)) { pr_debug("ip: %s parse failed.!\n", dptr); return 0; } /* Port number */ if (*dptr == ':') { dptr++; dptr += digits_len(ct, dptr, limit, shift); } return dptr - aux; } /* get address length, skiping user info. */ static int skp_epaddr_len(const struct nf_conn *ct, const char *dptr, const char *limit, int *shift) { const char *start = dptr; int s = *shift; /* Search for @, but stop at the end of the line. * We are inside a sip: URI, so we don't need to worry about * continuation lines. */ while (dptr < limit && *dptr != '@' && *dptr != '\r' && *dptr != '\n') { (*shift)++; dptr++; } if (dptr < limit && *dptr == '@') { dptr++; (*shift)++; } else { dptr = start; *shift = s; } return epaddr_len(ct, dptr, limit, shift); } /* Parse a SIP request line of the form: * * Request-Line = Method SP Request-URI SP SIP-Version CRLF * * and return the offset and length of the address contained in the Request-URI. */ int ct_sip_parse_request(const struct nf_conn *ct, const char *dptr, unsigned int datalen, unsigned int *matchoff, unsigned int *matchlen, union nf_inet_addr *addr, __be16 *port) { const char *start = dptr, *limit = dptr + datalen, *end; unsigned int mlen; unsigned int p; int shift = 0; /* Skip method and following whitespace */ mlen = string_len(ct, dptr, limit, NULL); if (!mlen) return 0; dptr += mlen; if (++dptr >= limit) return 0; /* Find SIP URI */ limit -= strlen("sip:"); for (; dptr < limit; dptr++) { if (*dptr == '\r' || *dptr == '\n') return -1; if (strnicmp(dptr, "sip:", strlen("sip:")) == 0) break; } if (!skp_epaddr_len(ct, dptr, limit, &shift)) return 0; dptr += shift; if (!parse_addr(ct, dptr, &end, addr, limit)) return -1; if (end < limit && *end == ':') { end++; p = simple_strtoul(end, (char **)&end, 10); if (p < 1024 || p > 65535) return -1; *port = htons(p); } else *port = htons(SIP_PORT); if (end == dptr) return 0; *matchoff = dptr - start; *matchlen = end - dptr; return 1; } EXPORT_SYMBOL_GPL(ct_sip_parse_request); /* SIP header parsing: SIP headers are located at the beginning of a line, but * may span several lines, in which case the continuation lines begin with a * whitespace character. RFC 2543 allows lines to be terminated with CR, LF or * CRLF, RFC 3261 allows only CRLF, we support both. * * Headers are followed by (optionally) whitespace, a colon, again (optionally) * whitespace and the values. Whitespace in this context means any amount of * tabs, spaces and continuation lines, which are treated as a single whitespace * character. * * Some headers may appear multiple times. A comma seperated list of values is * equivalent to multiple headers. */ static const struct sip_header ct_sip_hdrs[] = { [SIP_HDR_CSEQ] = SIP_HDR("CSeq", NULL, NULL, digits_len), [SIP_HDR_FROM] = SIP_HDR("From", "f", "sip:", skp_epaddr_len), [SIP_HDR_TO] = SIP_HDR("To", "t", "sip:", skp_epaddr_len), [SIP_HDR_CONTACT] = SIP_HDR("Contact", "m", "sip:", skp_epaddr_len), [SIP_HDR_VIA] = SIP_HDR("Via", "v", "UDP ", epaddr_len), [SIP_HDR_EXPIRES] = SIP_HDR("Expires", NULL, NULL, digits_len), [SIP_HDR_CONTENT_LENGTH] = SIP_HDR("Content-Length", "l", NULL, digits_len), }; static const char *sip_follow_continuation(const char *dptr, const char *limit) { /* Walk past newline */ if (++dptr >= limit) return NULL; /* Skip '\n' in CR LF */ if (*(dptr - 1) == '\r' && *dptr == '\n') { if (++dptr >= limit) return NULL; } /* Continuation line? */ if (*dptr != ' ' && *dptr != '\t') return NULL; /* skip leading whitespace */ for (; dptr < limit; dptr++) { if (*dptr != ' ' && *dptr != '\t') break; } return dptr; } static const char *sip_skip_whitespace(const char *dptr, const char *limit) { for (; dptr < limit; dptr++) { if (*dptr == ' ') continue; if (*dptr != '\r' && *dptr != '\n') break; dptr = sip_follow_continuation(dptr, limit); if (dptr == NULL) return NULL; } return dptr; } /* Search within a SIP header value, dealing with continuation lines */ static const char *ct_sip_header_search(const char *dptr, const char *limit, const char *needle, unsigned int len) { for (limit -= len; dptr < limit; dptr++) { if (*dptr == '\r' || *dptr == '\n') { dptr = sip_follow_continuation(dptr, limit); if (dptr == NULL) break; continue; } if (strnicmp(dptr, needle, len) == 0) return dptr; } return NULL; } int ct_sip_get_header(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, enum sip_header_types type, unsigned int *matchoff, unsigned int *matchlen) { const struct sip_header *hdr = &ct_sip_hdrs[type]; const char *start = dptr, *limit = dptr + datalen; int shift = 0; for (dptr += dataoff; dptr < limit; dptr++) { /* Find beginning of line */ if (*dptr != '\r' && *dptr != '\n') continue; if (++dptr >= limit) break; if (*(dptr - 1) == '\r' && *dptr == '\n') { if (++dptr >= limit) break; } /* Skip continuation lines */ if (*dptr == ' ' || *dptr == '\t') continue; /* Find header. Compact headers must be followed by a * non-alphabetic character to avoid mismatches. */ if (limit - dptr >= hdr->len && strnicmp(dptr, hdr->name, hdr->len) == 0) dptr += hdr->len; else if (hdr->cname && limit - dptr >= hdr->clen + 1 && strnicmp(dptr, hdr->cname, hdr->clen) == 0 && !isalpha(*(dptr + hdr->clen + 1))) dptr += hdr->clen; else continue; /* Find and skip colon */ dptr = sip_skip_whitespace(dptr, limit); if (dptr == NULL) break; if (*dptr != ':' || ++dptr >= limit) break; /* Skip whitespace after colon */ dptr = sip_skip_whitespace(dptr, limit); if (dptr == NULL) break; *matchoff = dptr - start; if (hdr->search) { dptr = ct_sip_header_search(dptr, limit, hdr->search, hdr->slen); if (!dptr) return -1; dptr += hdr->slen; } *matchlen = hdr->match_len(ct, dptr, limit, &shift); if (!*matchlen) return -1; *matchoff = dptr - start + shift; return 1; } return 0; } EXPORT_SYMBOL_GPL(ct_sip_get_header); /* Get next header field in a list of comma seperated values */ static int ct_sip_next_header(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, enum sip_header_types type, unsigned int *matchoff, unsigned int *matchlen) { const struct sip_header *hdr = &ct_sip_hdrs[type]; const char *start = dptr, *limit = dptr + datalen; int shift = 0; dptr += dataoff; dptr = ct_sip_header_search(dptr, limit, ",", strlen(",")); if (!dptr) return 0; dptr = ct_sip_header_search(dptr, limit, hdr->search, hdr->slen); if (!dptr) return 0; dptr += hdr->slen; *matchoff = dptr - start; *matchlen = hdr->match_len(ct, dptr, limit, &shift); if (!*matchlen) return -1; *matchoff += shift; return 1; } /* Walk through headers until a parsable one is found or no header of the * given type is left. */ static int ct_sip_walk_headers(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, enum sip_header_types type, int *in_header, unsigned int *matchoff, unsigned int *matchlen) { int ret; if (in_header && *in_header) { while (1) { ret = ct_sip_next_header(ct, dptr, dataoff, datalen, type, matchoff, matchlen); if (ret > 0) return ret; if (ret == 0) break; dataoff += *matchoff; } *in_header = 0; } while (1) { ret = ct_sip_get_header(ct, dptr, dataoff, datalen, type, matchoff, matchlen); if (ret > 0) break; if (ret == 0) return ret; dataoff += *matchoff; } if (in_header) *in_header = 1; return 1; } /* Locate a SIP header, parse the URI and return the offset and length of * the address as well as the address and port themselves. A stream of * headers can be parsed by handing in a non-NULL datalen and in_header * pointer. */ int ct_sip_parse_header_uri(const struct nf_conn *ct, const char *dptr, unsigned int *dataoff, unsigned int datalen, enum sip_header_types type, int *in_header, unsigned int *matchoff, unsigned int *matchlen, union nf_inet_addr *addr, __be16 *port) { const char *c, *limit = dptr + datalen; unsigned int p; int ret; ret = ct_sip_walk_headers(ct, dptr, dataoff ? *dataoff : 0, datalen, type, in_header, matchoff, matchlen); WARN_ON(ret < 0); if (ret == 0) return ret; if (!parse_addr(ct, dptr + *matchoff, &c, addr, limit)) return -1; if (*c == ':') { c++; p = simple_strtoul(c, (char **)&c, 10); if (p < 1024 || p > 65535) return -1; *port = htons(p); } else *port = htons(SIP_PORT); if (dataoff) *dataoff = c - dptr; return 1; } EXPORT_SYMBOL_GPL(ct_sip_parse_header_uri); /* Parse address from header parameter and return address, offset and length */ int ct_sip_parse_address_param(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, const char *name, unsigned int *matchoff, unsigned int *matchlen, union nf_inet_addr *addr) { const char *limit = dptr + datalen; const char *start, *end; limit = ct_sip_header_search(dptr + dataoff, limit, ",", strlen(",")); if (!limit) limit = dptr + datalen; start = ct_sip_header_search(dptr + dataoff, limit, name, strlen(name)); if (!start) return 0; start += strlen(name); if (!parse_addr(ct, start, &end, addr, limit)) return 0; *matchoff = start - dptr; *matchlen = end - start; return 1; } EXPORT_SYMBOL_GPL(ct_sip_parse_address_param); /* Parse numerical header parameter and return value, offset and length */ int ct_sip_parse_numerical_param(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, const char *name, unsigned int *matchoff, unsigned int *matchlen, unsigned int *val) { const char *limit = dptr + datalen; const char *start; char *end; limit = ct_sip_header_search(dptr + dataoff, limit, ",", strlen(",")); if (!limit) limit = dptr + datalen; start = ct_sip_header_search(dptr + dataoff, limit, name, strlen(name)); if (!start) return 0; start += strlen(name); *val = simple_strtoul(start, &end, 0); if (start == end) return 0; if (matchoff && matchlen) { *matchoff = start - dptr; *matchlen = end - start; } return 1; } EXPORT_SYMBOL_GPL(ct_sip_parse_numerical_param); /* SDP header parsing: a SDP session description contains an ordered set of * headers, starting with a section containing general session parameters, * optionally followed by multiple media descriptions. * * SDP headers always start at the beginning of a line. According to RFC 2327: * "The sequence CRLF (0x0d0a) is used to end a record, although parsers should * be tolerant and also accept records terminated with a single newline * character". We handle both cases. */ static const struct sip_header ct_sdp_hdrs[] = { [SDP_HDR_VERSION] = SDP_HDR("v=", NULL, digits_len), [SDP_HDR_OWNER_IP4] = SDP_HDR("o=", "IN IP4 ", epaddr_len), [SDP_HDR_CONNECTION_IP4] = SDP_HDR("c=", "IN IP4 ", epaddr_len), [SDP_HDR_OWNER_IP6] = SDP_HDR("o=", "IN IP6 ", epaddr_len), [SDP_HDR_CONNECTION_IP6] = SDP_HDR("c=", "IN IP6 ", epaddr_len), [SDP_HDR_MEDIA] = SDP_HDR("m=", NULL, media_len), }; /* Linear string search within SDP header values */ static const char *ct_sdp_header_search(const char *dptr, const char *limit, const char *needle, unsigned int len) { for (limit -= len; dptr < limit; dptr++) { if (*dptr == '\r' || *dptr == '\n') break; if (strncmp(dptr, needle, len) == 0) return dptr; } return NULL; } /* Locate a SDP header (optionally a substring within the header value), * optionally stopping at the first occurence of the term header, parse * it and return the offset and length of the data we're interested in. */ int ct_sip_get_sdp_header(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, enum sdp_header_types type, enum sdp_header_types term, unsigned int *matchoff, unsigned int *matchlen) { const struct sip_header *hdr = &ct_sdp_hdrs[type]; const struct sip_header *thdr = &ct_sdp_hdrs[term]; const char *start = dptr, *limit = dptr + datalen; int shift = 0; for (dptr += dataoff; dptr < limit; dptr++) { /* Find beginning of line */ if (*dptr != '\r' && *dptr != '\n') continue; if (++dptr >= limit) break; if (*(dptr - 1) == '\r' && *dptr == '\n') { if (++dptr >= limit) break; } if (term != SDP_HDR_UNSPEC && limit - dptr >= thdr->len && strnicmp(dptr, thdr->name, thdr->len) == 0) break; else if (limit - dptr >= hdr->len && strnicmp(dptr, hdr->name, hdr->len) == 0) dptr += hdr->len; else continue; *matchoff = dptr - start; if (hdr->search) { dptr = ct_sdp_header_search(dptr, limit, hdr->search, hdr->slen); if (!dptr) return -1; dptr += hdr->slen; } *matchlen = hdr->match_len(ct, dptr, limit, &shift); if (!*matchlen) return -1; *matchoff = dptr - start + shift; return 1; } return 0; } EXPORT_SYMBOL_GPL(ct_sip_get_sdp_header); static int ct_sip_parse_sdp_addr(const struct nf_conn *ct, const char *dptr, unsigned int dataoff, unsigned int datalen, enum sdp_header_types type, enum sdp_header_types term, unsigned int *matchoff, unsigned int *matchlen, union nf_inet_addr *addr) { int ret; ret = ct_sip_get_sdp_header(ct, dptr, dataoff, datalen, type, term, matchoff, matchlen); if (ret <= 0) return ret; if (!parse_addr(ct, dptr + *matchoff, NULL, addr, dptr + *matchoff + *matchlen)) return -1; return 1; } static int refresh_signalling_expectation(struct nf_conn *ct, union nf_inet_addr *addr, __be16 port, unsigned int expires) { struct nf_conn_help *help = nfct_help(ct); struct nf_conntrack_expect *exp; struct hlist_node *n, *next; int found = 0; spin_lock_bh(&nf_conntrack_lock); hlist_for_each_entry_safe(exp, n, next, &help->expectations, lnode) { if (exp->class != SIP_EXPECT_SIGNALLING || !nf_inet_addr_cmp(&exp->tuple.dst.u3, addr) || exp->tuple.dst.u.udp.port != port) continue; if (!del_timer(&exp->timeout)) continue; exp->flags &= ~NF_CT_EXPECT_INACTIVE; exp->timeout.expires = jiffies + expires * HZ; add_timer(&exp->timeout); found = 1; break; } spin_unlock_bh(&nf_conntrack_lock); return found; } static void flush_expectations(struct nf_conn *ct, bool media) { struct nf_conn_help *help = nfct_help(ct); struct nf_conntrack_expect *exp; struct hlist_node *n, *next; spin_lock_bh(&nf_conntrack_lock); hlist_for_each_entry_safe(exp, n, next, &help->expectations, lnode) { if ((exp->class != SIP_EXPECT_SIGNALLING) ^ media) continue; if (!del_timer(&exp->timeout)) continue; nf_ct_unlink_expect(exp); nf_ct_expect_put(exp); if (!media) break; } spin_unlock_bh(&nf_conntrack_lock); } static int set_expected_rtp_rtcp(struct sk_buff *skb, const char **dptr, unsigned int *datalen, union nf_inet_addr *daddr, __be16 port, enum sip_expectation_classes class, unsigned int mediaoff, unsigned int medialen) { struct nf_conntrack_expect *exp, *rtp_exp, *rtcp_exp; enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct net *net = nf_ct_net(ct); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); union nf_inet_addr *saddr; struct nf_conntrack_tuple tuple; int direct_rtp = 0, skip_expect = 0, ret = NF_DROP; u_int16_t base_port; __be16 rtp_port, rtcp_port; typeof(nf_nat_sdp_port_hook) nf_nat_sdp_port; typeof(nf_nat_sdp_media_hook) nf_nat_sdp_media; saddr = NULL; if (sip_direct_media) { if (!nf_inet_addr_cmp(daddr, &ct->tuplehash[dir].tuple.src.u3)) return NF_ACCEPT; saddr = &ct->tuplehash[!dir].tuple.src.u3; } /* We need to check whether the registration exists before attempting * to register it since we can see the same media description multiple * times on different connections in case multiple endpoints receive * the same call. * * RTP optimization: if we find a matching media channel expectation * and both the expectation and this connection are SNATed, we assume * both sides can reach each other directly and use the final * destination address from the expectation. We still need to keep * the NATed expectations for media that might arrive from the * outside, and additionally need to expect the direct RTP stream * in case it passes through us even without NAT. */ memset(&tuple, 0, sizeof(tuple)); if (saddr) tuple.src.u3 = *saddr; tuple.src.l3num = nf_ct_l3num(ct); tuple.dst.protonum = IPPROTO_UDP; tuple.dst.u3 = *daddr; tuple.dst.u.udp.port = port; rcu_read_lock(); do { exp = __nf_ct_expect_find(net, &tuple); if (!exp || exp->master == ct || nfct_help(exp->master)->helper != nfct_help(ct)->helper || exp->class != class) break; #ifdef CONFIG_NF_NAT_NEEDED if (exp->tuple.src.l3num == AF_INET && !direct_rtp && (exp->saved_ip != exp->tuple.dst.u3.ip || exp->saved_proto.udp.port != exp->tuple.dst.u.udp.port) && ct->status & IPS_NAT_MASK) { daddr->ip = exp->saved_ip; tuple.dst.u3.ip = exp->saved_ip; tuple.dst.u.udp.port = exp->saved_proto.udp.port; direct_rtp = 1; } else #endif skip_expect = 1; } while (!skip_expect); rcu_read_unlock(); base_port = ntohs(tuple.dst.u.udp.port) & ~1; rtp_port = htons(base_port); rtcp_port = htons(base_port + 1); if (direct_rtp) { nf_nat_sdp_port = rcu_dereference(nf_nat_sdp_port_hook); if (nf_nat_sdp_port && !nf_nat_sdp_port(skb, dptr, datalen, mediaoff, medialen, ntohs(rtp_port))) goto err1; } if (skip_expect) return NF_ACCEPT; rtp_exp = nf_ct_expect_alloc(ct); if (rtp_exp == NULL) goto err1; /* When there is SIP Proxy server, the expected RTP connection should be from * the WAN user & not from Proxy server.Hence, changing the expectation to be on 'any source IP'*/ saddr = NULL; nf_ct_expect_init(rtp_exp, class, nf_ct_l3num(ct), saddr, daddr, IPPROTO_UDP, NULL, &rtp_port); rtcp_exp = nf_ct_expect_alloc(ct); if (rtcp_exp == NULL) goto err2; nf_ct_expect_init(rtcp_exp, class, nf_ct_l3num(ct), saddr, daddr, IPPROTO_UDP, NULL, &rtcp_port); nf_nat_sdp_media = rcu_dereference(nf_nat_sdp_media_hook); if (nf_nat_sdp_media && ct->status & IPS_NAT_MASK && !direct_rtp) ret = nf_nat_sdp_media(skb, dptr, datalen, rtp_exp, rtcp_exp, mediaoff, medialen, daddr); else { if (nf_ct_expect_related(rtp_exp) == 0) { if (nf_ct_expect_related(rtcp_exp) != 0) nf_ct_unexpect_related(rtp_exp); else ret = NF_ACCEPT; } } nf_ct_expect_put(rtcp_exp); err2: nf_ct_expect_put(rtp_exp); err1: return ret; } static const struct sdp_media_type sdp_media_types[] = { SDP_MEDIA_TYPE("audio ", SIP_EXPECT_AUDIO), SDP_MEDIA_TYPE("video ", SIP_EXPECT_VIDEO), }; static const struct sdp_media_type *sdp_media_type(const char *dptr, unsigned int matchoff, unsigned int matchlen) { const struct sdp_media_type *t; unsigned int i; for (i = 0; i < ARRAY_SIZE(sdp_media_types); i++) { t = &sdp_media_types[i]; if (matchlen < t->len || strncmp(dptr + matchoff, t->name, t->len)) continue; return t; } return NULL; } static int process_sdp(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct nf_conn_help *help = nfct_help(ct); unsigned int matchoff, matchlen; unsigned int mediaoff, medialen; unsigned int sdpoff; unsigned int caddr_len, maddr_len; unsigned int i; union nf_inet_addr caddr, maddr, rtp_addr; unsigned int port; enum sdp_header_types c_hdr; const struct sdp_media_type *t; int ret = NF_ACCEPT; typeof(nf_nat_sdp_addr_hook) nf_nat_sdp_addr; typeof(nf_nat_sdp_session_hook) nf_nat_sdp_session; nf_nat_sdp_addr = rcu_dereference(nf_nat_sdp_addr_hook); c_hdr = nf_ct_l3num(ct) == AF_INET ? SDP_HDR_CONNECTION_IP4 : SDP_HDR_CONNECTION_IP6; /* Find beginning of session description */ if (ct_sip_get_sdp_header(ct, *dptr, 0, *datalen, SDP_HDR_VERSION, SDP_HDR_UNSPEC, &matchoff, &matchlen) <= 0) return NF_ACCEPT; sdpoff = matchoff; /* The connection information is contained in the session description * and/or once per media description. The first media description marks * the end of the session description. */ caddr_len = 0; if (ct_sip_parse_sdp_addr(ct, *dptr, sdpoff, *datalen, c_hdr, SDP_HDR_MEDIA, &matchoff, &matchlen, &caddr) > 0) caddr_len = matchlen; mediaoff = sdpoff; for (i = 0; i < ARRAY_SIZE(sdp_media_types); ) { if (ct_sip_get_sdp_header(ct, *dptr, mediaoff, *datalen, SDP_HDR_MEDIA, SDP_HDR_UNSPEC, &mediaoff, &medialen) <= 0) break; /* Get media type and port number. A media port value of zero * indicates an inactive stream. */ t = sdp_media_type(*dptr, mediaoff, medialen); if (!t) { mediaoff += medialen; continue; } mediaoff += t->len; medialen -= t->len; port = simple_strtoul(*dptr + mediaoff, NULL, 10); if (port == 0) continue; if (port < 1024 || port > 65535) return NF_DROP; /* The media description overrides the session description. */ maddr_len = 0; if (ct_sip_parse_sdp_addr(ct, *dptr, mediaoff, *datalen, c_hdr, SDP_HDR_MEDIA, &matchoff, &matchlen, &maddr) > 0) { maddr_len = matchlen; memcpy(&rtp_addr, &maddr, sizeof(rtp_addr)); } else if (caddr_len) memcpy(&rtp_addr, &caddr, sizeof(rtp_addr)); else return NF_DROP; ret = set_expected_rtp_rtcp(skb, dptr, datalen, &rtp_addr, htons(port), t->class, mediaoff, medialen); if (ret != NF_ACCEPT) return ret; /* Update media connection address if present */ if (maddr_len && nf_nat_sdp_addr && ct->status & IPS_NAT_MASK) { ret = nf_nat_sdp_addr(skb, dptr, mediaoff, datalen, c_hdr, SDP_HDR_MEDIA, &rtp_addr); if (ret != NF_ACCEPT) return ret; } i++; } /* Update session connection and owner addresses */ nf_nat_sdp_session = rcu_dereference(nf_nat_sdp_session_hook); if (nf_nat_sdp_session && ct->status & IPS_NAT_MASK) ret = nf_nat_sdp_session(skb, dptr, sdpoff, datalen, &rtp_addr); if (ret == NF_ACCEPT && i > 0) help->help.ct_sip_info.invite_cseq = cseq; return ret; } static int process_invite_response(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq, unsigned int code) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct nf_conn_help *help = nfct_help(ct); if ((code >= 100 && code <= 199) || (code >= 200 && code <= 299)) return process_sdp(skb, dptr, datalen, cseq); else if (help->help.ct_sip_info.invite_cseq == cseq) flush_expectations(ct, true); return NF_ACCEPT; } static int process_update_response(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq, unsigned int code) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct nf_conn_help *help = nfct_help(ct); if ((code >= 100 && code <= 199) || (code >= 200 && code <= 299)) return process_sdp(skb, dptr, datalen, cseq); else if (help->help.ct_sip_info.invite_cseq == cseq) flush_expectations(ct, true); return NF_ACCEPT; } static int process_prack_response(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq, unsigned int code) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct nf_conn_help *help = nfct_help(ct); if ((code >= 100 && code <= 199) || (code >= 200 && code <= 299)) return process_sdp(skb, dptr, datalen, cseq); else if (help->help.ct_sip_info.invite_cseq == cseq) flush_expectations(ct, true); return NF_ACCEPT; } static int process_bye_request(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); flush_expectations(ct, true); return NF_ACCEPT; } /* Parse a REGISTER request and create a permanent expectation for incoming * signalling connections. The expectation is marked inactive and is activated * when receiving a response indicating success from the registrar. */ static int process_register_request(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct nf_conn_help *help = nfct_help(ct); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned int matchoff, matchlen; struct nf_conntrack_expect *exp; union nf_inet_addr *saddr, daddr; __be16 port; unsigned int expires = 0; int ret; typeof(nf_nat_sip_expect_hook) nf_nat_sip_expect; /* Expected connections can not register again. */ if (ct->status & IPS_EXPECTED) return NF_ACCEPT; /* We must check the expiration time: a value of zero signals the * registrar to release the binding. We'll remove our expectation * when receiving the new bindings in the response, but we don't * want to create new ones. * * The expiration time may be contained in Expires: header, the * Contact: header parameters or the URI parameters. */ if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_EXPIRES, &matchoff, &matchlen) > 0) expires = simple_strtoul(*dptr + matchoff, NULL, 10); ret = ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, SIP_HDR_CONTACT, NULL, &matchoff, &matchlen, &daddr, &port); if (ret < 0) return NF_DROP; else if (ret == 0) return NF_ACCEPT; /* We don't support third-party registrations */ if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3, &daddr)) return NF_ACCEPT; if (ct_sip_parse_numerical_param(ct, *dptr, matchoff + matchlen, *datalen, "expires=", NULL, NULL, &expires) < 0) return NF_DROP; if (expires == 0) { ret = NF_ACCEPT; goto store_cseq; } exp = nf_ct_expect_alloc(ct); if (!exp) return NF_DROP; saddr = NULL; if (sip_direct_signalling) saddr = &ct->tuplehash[!dir].tuple.src.u3; nf_ct_expect_init(exp, SIP_EXPECT_SIGNALLING, nf_ct_l3num(ct), saddr, &daddr, IPPROTO_UDP, NULL, &port); exp->timeout.expires = sip_timeout * HZ; exp->helper = nfct_help(ct)->helper; exp->flags = NF_CT_EXPECT_PERMANENT | NF_CT_EXPECT_INACTIVE; nf_nat_sip_expect = rcu_dereference(nf_nat_sip_expect_hook); if (nf_nat_sip_expect && ct->status & IPS_NAT_MASK) ret = nf_nat_sip_expect(skb, dptr, datalen, exp, matchoff, matchlen); else { if (nf_ct_expect_related(exp) != 0) ret = NF_DROP; else ret = NF_ACCEPT; } nf_ct_expect_put(exp); store_cseq: if (ret == NF_ACCEPT) help->help.ct_sip_info.register_cseq = cseq; return ret; } static int process_register_response(struct sk_buff *skb, const char **dptr, unsigned int *datalen, unsigned int cseq, unsigned int code) { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); struct nf_conn_help *help = nfct_help(ct); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); union nf_inet_addr addr; __be16 port; unsigned int matchoff, matchlen, dataoff = 0; unsigned int expires = 0; int in_contact = 0, ret; /* According to RFC 3261, "UAs MUST NOT send a new registration until * they have received a final response from the registrar for the * previous one or the previous REGISTER request has timed out". * * However, some servers fail to detect retransmissions and send late * responses, so we store the sequence number of the last valid * request and compare it here. */ if (help->help.ct_sip_info.register_cseq != cseq) return NF_ACCEPT; if (code >= 100 && code <= 199) return NF_ACCEPT; if (code < 200 || code > 299) goto flush; if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_EXPIRES, &matchoff, &matchlen) > 0) expires = simple_strtoul(*dptr + matchoff, NULL, 10); while (1) { unsigned int c_expires = expires; ret = ct_sip_parse_header_uri(ct, *dptr, &dataoff, *datalen, SIP_HDR_CONTACT, &in_contact, &matchoff, &matchlen, &addr, &port); if (ret < 0) return NF_DROP; else if (ret == 0) break; /* We don't support third-party registrations */ if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3, &addr)) continue; ret = ct_sip_parse_numerical_param(ct, *dptr, matchoff + matchlen, *datalen, "expires=", NULL, NULL, &c_expires); if (ret < 0) return NF_DROP; if (c_expires == 0) break; if (refresh_signalling_expectation(ct, &addr, port, c_expires)) return NF_ACCEPT; } flush: flush_expectations(ct, false); return NF_ACCEPT; } static const struct sip_handler sip_handlers[] = { SIP_HANDLER("INVITE", process_sdp, process_invite_response), SIP_HANDLER("UPDATE", process_sdp, process_update_response), SIP_HANDLER("ACK", process_sdp, NULL), SIP_HANDLER("PRACK", process_sdp, process_prack_response), SIP_HANDLER("BYE", process_bye_request, NULL), SIP_HANDLER("REGISTER", process_register_request, process_register_response), }; static int process_sip_response(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; unsigned int code, cseq, dataoff, i; if (*datalen < strlen("SIP/2.0 200")) return NF_ACCEPT; code = simple_strtoul(*dptr + strlen("SIP/2.0 "), NULL, 10); if (!code) return NF_DROP; if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CSEQ, &matchoff, &matchlen) <= 0) return NF_DROP; cseq = simple_strtoul(*dptr + matchoff, NULL, 10); if (!cseq) return NF_DROP; dataoff = matchoff + matchlen + 1; for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) { const struct sip_handler *handler; handler = &sip_handlers[i]; if (handler->response == NULL) continue; if (*datalen < dataoff + handler->len || strnicmp(*dptr + dataoff, handler->method, handler->len)) continue; return handler->response(skb, dptr, datalen, cseq, code); } return NF_ACCEPT; } static int process_sip_request(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; unsigned int cseq, i; for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) { const struct sip_handler *handler; handler = &sip_handlers[i]; if (handler->request == NULL) continue; if (*datalen < handler->len || strnicmp(*dptr, handler->method, handler->len)) continue; if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CSEQ, &matchoff, &matchlen) <= 0) return NF_DROP; cseq = simple_strtoul(*dptr + matchoff, NULL, 10); if (!cseq) return NF_DROP; return handler->request(skb, dptr, datalen, cseq); } return NF_ACCEPT; } static int sip_help(struct sk_buff *skb, unsigned int protoff, struct nf_conn *ct, enum ip_conntrack_info ctinfo) { unsigned int dataoff, datalen; const char *dptr; int ret; typeof(nf_nat_sip_hook) nf_nat_sip; /* No Data ? */ dataoff = protoff + sizeof(struct udphdr); if (dataoff >= skb->len) return NF_ACCEPT; nf_ct_refresh(ct, skb, sip_timeout * HZ); if (!skb_is_nonlinear(skb)) dptr = skb->data + dataoff; else { pr_debug("Copy of skbuff not supported yet.\n"); return NF_ACCEPT; } datalen = skb->len - dataoff; if (datalen < strlen("SIP/2.0 200")) return NF_ACCEPT; if (strnicmp(dptr, "SIP/2.0 ", strlen("SIP/2.0 ")) != 0) ret = process_sip_request(skb, &dptr, &datalen); else ret = process_sip_response(skb, &dptr, &datalen); if (ret == NF_ACCEPT && ct->status & IPS_NAT_MASK) { nf_nat_sip = rcu_dereference(nf_nat_sip_hook); if (nf_nat_sip && !nf_nat_sip(skb, &dptr, &datalen)) ret = NF_DROP; } return ret; } static struct nf_conntrack_helper sip[MAX_PORTS][2] __read_mostly; static char sip_names[MAX_PORTS][2][sizeof("sip-65535")] __read_mostly; static const struct nf_conntrack_expect_policy sip_exp_policy[SIP_EXPECT_MAX + 1] = { [SIP_EXPECT_SIGNALLING] = { .max_expected = 1, .timeout = 3 * 60, }, [SIP_EXPECT_AUDIO] = { .max_expected = 2 * IP_CT_DIR_MAX, .timeout = 3 * 60, }, [SIP_EXPECT_VIDEO] = { .max_expected = 2 * IP_CT_DIR_MAX, .timeout = 3 * 60, }, }; static void nf_conntrack_sip_fini(void) { int i, j; for (i = 0; i < ports_c; i++) { for (j = 0; j < 2; j++) { if (sip[i][j].me == NULL) continue; nf_conntrack_helper_unregister(&sip[i][j]); } } } static int __init nf_conntrack_sip_init(void) { int i, j, ret; char *tmpname; if (ports_c == 0) ports[ports_c++] = SIP_PORT; for (i = 0; i < ports_c; i++) { memset(&sip[i], 0, sizeof(sip[i])); sip[i][0].tuple.src.l3num = AF_INET; sip[i][1].tuple.src.l3num = AF_INET6; for (j = 0; j < 2; j++) { sip[i][j].tuple.dst.protonum = IPPROTO_UDP; sip[i][j].tuple.src.u.udp.port = htons(ports[i]); sip[i][j].expect_policy = sip_exp_policy; sip[i][j].expect_class_max = SIP_EXPECT_MAX; sip[i][j].me = THIS_MODULE; sip[i][j].help = sip_help; tmpname = &sip_names[i][j][0]; if (ports[i] == SIP_PORT) sprintf(tmpname, "sip"); else sprintf(tmpname, "sip-%u", i); sip[i][j].name = tmpname; pr_debug("port #%u: %u\n", i, ports[i]); ret = nf_conntrack_helper_register(&sip[i][j]); if (ret) { printk("nf_ct_sip: failed to register helper " "for pf: %u port: %u\n", sip[i][j].tuple.src.l3num, ports[i]); nf_conntrack_sip_fini(); return ret; } } } return 0; } module_init(nf_conntrack_sip_init); module_exit(nf_conntrack_sip_fini);