--- /dev/null
+/* SIP extension for IP connection tracking.
+ *
+ * (C) 2005 by Christian Hentschel <chentschel@arnet.com.ar>
+ * based on RR's ip_conntrack_ftp.c and other modules.
+ *
+ * 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/ctype.h>
+#include <linux/skbuff.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
+#include <linux/netfilter_ipv4/ip_conntrack_sip.h>
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christian Hentschel <chentschel@arnet.com.ar>");
+MODULE_DESCRIPTION("SIP connection tracking helper");
+
+#define MAX_PORTS 8
+static unsigned short ports[MAX_PORTS];
+static 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 = SIP_TIMEOUT;
+module_param(sip_timeout, uint, 0600);
+MODULE_PARM_DESC(sip_timeout, "timeout for the master SIP session");
+
+unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb,
+ enum ip_conntrack_info ctinfo,
+ struct ip_conntrack *ct,
+ const char **dptr);
+EXPORT_SYMBOL_GPL(ip_nat_sip_hook);
+
+unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb,
+ enum ip_conntrack_info ctinfo,
+ struct ip_conntrack_expect *exp,
+ const char *dptr);
+EXPORT_SYMBOL_GPL(ip_nat_sdp_hook);
+
+int ct_sip_get_info(const char *dptr, size_t dlen,
+ unsigned int *matchoff,
+ unsigned int *matchlen,
+ struct sip_header_nfo *hnfo);
+EXPORT_SYMBOL_GPL(ct_sip_get_info);
+
+
+static int digits_len(const char *dptr, const char *limit, int *shift);
+static int epaddr_len(const char *dptr, const char *limit, int *shift);
+static int skp_digits_len(const char *dptr, const char *limit, int *shift);
+static int skp_epaddr_len(const char *dptr, const char *limit, int *shift);
+
+struct sip_header_nfo ct_sip_hdrs[] = {
+ { /* Via header */
+ .lname = "Via:",
+ .lnlen = sizeof("Via:") - 1,
+ .sname = "\r\nv:",
+ .snlen = sizeof("\r\nv:") - 1, /* rfc3261 "\r\n" */
+ .ln_str = "UDP ",
+ .ln_strlen = sizeof("UDP ") - 1,
+ .match_len = epaddr_len,
+ },
+ { /* Contact header */
+ .lname = "Contact:",
+ .lnlen = sizeof("Contact:") - 1,
+ .sname = "\r\nm:",
+ .snlen = sizeof("\r\nm:") - 1,
+ .ln_str = "sip:",
+ .ln_strlen = sizeof("sip:") - 1,
+ .match_len = skp_epaddr_len
+ },
+ { /* Content length header */
+ .lname = "Content-Length:",
+ .lnlen = sizeof("Content-Length:") - 1,
+ .sname = "\r\nl:",
+ .snlen = sizeof("\r\nl:") - 1,
+ .ln_str = ":",
+ .ln_strlen = sizeof(":") - 1,
+ .match_len = skp_digits_len
+ },
+ { /* SDP media info */
+ .lname = "\nm=",
+ .lnlen = sizeof("\nm=") - 1,
+ .sname = "\rm=",
+ .snlen = sizeof("\rm=") - 1,
+ .ln_str = "audio ",
+ .ln_strlen = sizeof("audio ") - 1,
+ .match_len = digits_len
+ },
+ { /* SDP owner address*/
+ .lname = "\no=",
+ .lnlen = sizeof("\no=") - 1,
+ .sname = "\ro=",
+ .snlen = sizeof("\ro=") - 1,
+ .ln_str = "IN IP4 ",
+ .ln_strlen = sizeof("IN IP4 ") - 1,
+ .match_len = epaddr_len
+ },
+ { /* SDP connection info */
+ .lname = "\nc=",
+ .lnlen = sizeof("\nc=") - 1,
+ .sname = "\rc=",
+ .snlen = sizeof("\rc=") - 1,
+ .ln_str = "IN IP4 ",
+ .ln_strlen = sizeof("IN IP4 ") - 1,
+ .match_len = epaddr_len
+ },
+ { /* Requests headers */
+ .lname = "sip:",
+ .lnlen = sizeof("sip:") - 1,
+ .sname = "sip:",
+ .snlen = sizeof("sip:") - 1, /* yes, i know.. ;) */
+ .ln_str = "@",
+ .ln_strlen = sizeof("@") - 1,
+ .match_len = epaddr_len
+ },
+ { /* SDP version header */
+ .lname = "\nv=",
+ .lnlen = sizeof("\nv=") - 1,
+ .sname = "\rv=",
+ .snlen = sizeof("\rv=") - 1,
+ .ln_str = "=",
+ .ln_strlen = sizeof("=") - 1,
+ .match_len = digits_len
+ }
+};
+EXPORT_SYMBOL_GPL(ct_sip_hdrs);
+
+/* get line lenght until first CR or LF seen. */
+int ct_sip_lnlen(const char *line, const char *limit)
+{
+ const char *k = line;
+
+ while ((line <= limit) && (*line == '\r' || *line == '\n'))
+ line++;
+
+ while (line <= limit) {
+ if (*line == '\r' || *line == '\n')
+ break;
+ line++;
+ }
+ return line - k;
+}
+EXPORT_SYMBOL_GPL(ct_sip_lnlen);
+
+/* Linear string search, case sensitive. */
+const char *ct_sip_search(const char *needle, const char *haystack,
+ size_t needle_len, size_t haystack_len)
+{
+ const char *limit = haystack + (haystack_len - needle_len);
+
+ while (haystack <= limit) {
+ if (memcmp(haystack, needle, needle_len) == 0)
+ return haystack;
+ haystack++;
+ }
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(ct_sip_search);
+
+static int digits_len(const char *dptr, const char *limit, int *shift)
+{
+ int len = 0;
+ while (dptr <= limit && isdigit(*dptr)) {
+ dptr++;
+ len++;
+ }
+ return len;
+}
+
+/* get digits lenght, skiping blank spaces. */
+static int skp_digits_len(const char *dptr, const char *limit, int *shift)
+{
+ for (; dptr <= limit && *dptr == ' '; dptr++)
+ (*shift)++;
+
+ return digits_len(dptr, limit, shift);
+}
+
+/* Simple ipaddr parser.. */
+static int parse_ipaddr(const char *cp, const char **endp,
+ u_int32_t *ipaddr, const char *limit)
+{
+ unsigned long int val;
+ int i, digit = 0;
+
+ for (i = 0, *ipaddr = 0; cp <= limit && i < 4; i++) {
+ digit = 0;
+ if (!isdigit(*cp))
+ break;
+
+ val = simple_strtoul(cp, (char **)&cp, 10);
+ if (val > 0xFF)
+ return -1;
+
+ ((u_int8_t *)ipaddr)[i] = val;
+ digit = 1;
+
+ if (*cp != '.')
+ break;
+ cp++;
+ }
+ if (!digit)
+ return -1;
+
+ if (endp)
+ *endp = cp;
+
+ return 0;
+}
+
+/* skip ip address. returns it lenght. */
+static int epaddr_len(const char *dptr, const char *limit, int *shift)
+{
+ const char *aux = dptr;
+ u_int32_t ip;
+
+ if (parse_ipaddr(dptr, &dptr, &ip, limit) < 0) {
+ DEBUGP("ip: %s parse failed.!\n", dptr);
+ return 0;
+ }
+
+ /* Port number */
+ if (*dptr == ':') {
+ dptr++;
+ dptr += digits_len(dptr, limit, shift);
+ }
+ return dptr - aux;
+}
+
+/* get address length, skiping user info. */
+static int skp_epaddr_len(const char *dptr, const char *limit, int *shift)
+{
+ int s = *shift;
+
+ for (; dptr <= limit && *dptr != '@'; dptr++)
+ (*shift)++;
+
+ if (*dptr == '@') {
+ dptr++;
+ (*shift)++;
+ } else
+ *shift = s;
+
+ return epaddr_len(dptr, limit, shift);
+}
+
+/* Returns 0 if not found, -1 error parsing. */
+int ct_sip_get_info(const char *dptr, size_t dlen,
+ unsigned int *matchoff,
+ unsigned int *matchlen,
+ struct sip_header_nfo *hnfo)
+{
+ const char *limit, *aux, *k = dptr;
+ int shift = 0;
+
+ limit = dptr + (dlen - hnfo->lnlen);
+
+ while (dptr <= limit) {
+ if ((strncmp(dptr, hnfo->lname, hnfo->lnlen) != 0) &&
+ (strncmp(dptr, hnfo->sname, hnfo->snlen) != 0)) {
+ dptr++;
+ continue;
+ }
+ aux = ct_sip_search(hnfo->ln_str, dptr, hnfo->ln_strlen,
+ ct_sip_lnlen(dptr, limit));
+ if (!aux) {
+ DEBUGP("'%s' not found in '%s'.\n", hnfo->ln_str,
+ hnfo->lname);
+ return -1;
+ }
+ aux += hnfo->ln_strlen;
+
+ *matchlen = hnfo->match_len(aux, limit, &shift);
+ if (!*matchlen)
+ return -1;
+
+ *matchoff = (aux - k) + shift;
+
+ DEBUGP("%s match succeeded! - len: %u\n", hnfo->lname,
+ *matchlen);
+ return 1;
+ }
+ DEBUGP("%s header not found.\n", hnfo->lname);
+ return 0;
+}
+
+static int set_expected_rtp(struct sk_buff **pskb,
+ struct ip_conntrack *ct,
+ enum ip_conntrack_info ctinfo,
+ u_int32_t ipaddr, u_int16_t port,
+ const char *dptr)
+{
+ struct ip_conntrack_expect *exp;
+ enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+ int ret;
+
+ exp = ip_conntrack_expect_alloc(ct);
+ if (exp == NULL)
+ return NF_DROP;
+
+ exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip;
+ exp->tuple.src.u.udp.port = 0;
+ exp->tuple.dst.ip = ipaddr;
+ exp->tuple.dst.u.udp.port = htons(port);
+ exp->tuple.dst.protonum = IPPROTO_UDP;
+
+ exp->mask.src.ip = 0xFFFFFFFF;
+ exp->mask.src.u.udp.port = 0;
+ exp->mask.dst.ip = 0xFFFFFFFF;
+ exp->mask.dst.u.udp.port = 0xFFFF;
+ exp->mask.dst.protonum = 0xFF;
+
+ exp->expectfn = NULL;
+ exp->flags = 0;
+
+ if (ip_nat_sdp_hook)
+ ret = ip_nat_sdp_hook(pskb, ctinfo, exp, dptr);
+ else {
+ if (ip_conntrack_expect_related(exp) != 0)
+ ret = NF_DROP;
+ else
+ ret = NF_ACCEPT;
+ }
+ ip_conntrack_expect_put(exp);
+
+ return ret;
+}
+
+static int sip_help(struct sk_buff **pskb,
+ struct ip_conntrack *ct,
+ enum ip_conntrack_info ctinfo)
+{
+ unsigned int dataoff, datalen;
+ const char *dptr;
+ int ret = NF_ACCEPT;
+ int matchoff, matchlen;
+ u_int32_t ipaddr;
+ u_int16_t port;
+
+ /* No Data ? */
+ dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr);
+ if (dataoff >= (*pskb)->len) {
+ DEBUGP("skb->len = %u\n", (*pskb)->len);
+ return NF_ACCEPT;
+ }
+
+ ip_ct_refresh(ct, *pskb, sip_timeout * HZ);
+
+ if (!skb_is_nonlinear(*pskb))
+ dptr = (*pskb)->data + dataoff;
+ else {
+ DEBUGP("Copy of skbuff not supported yet.\n");
+ goto out;
+ }
+
+ if (ip_nat_sip_hook) {
+ if (!ip_nat_sip_hook(pskb, ctinfo, ct, &dptr)) {
+ ret = NF_DROP;
+ goto out;
+ }
+ }
+
+ /* After this point NAT, could have mangled skb, so
+ we need to recalculate payload lenght. */
+ datalen = (*pskb)->len - dataoff;
+
+ if (datalen < (sizeof("SIP/2.0 200") - 1))
+ goto out;
+
+ /* RTP info only in some SDP pkts */
+ if (memcmp(dptr, "INVITE", sizeof("INVITE") - 1) != 0 &&
+ memcmp(dptr, "SIP/2.0 200", sizeof("SIP/2.0 200") - 1) != 0) {
+ goto out;
+ }
+ /* Get ip and port address from SDP packet. */
+ if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen,
+ &ct_sip_hdrs[POS_CONNECTION]) > 0) {
+
+ /* We'll drop only if there are parse problems. */
+ if (parse_ipaddr(dptr + matchoff, NULL, &ipaddr,
+ dptr + datalen) < 0) {
+ ret = NF_DROP;
+ goto out;
+ }
+ if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen,
+ &ct_sip_hdrs[POS_MEDIA]) > 0) {
+
+ port = simple_strtoul(dptr + matchoff, NULL, 10);
+ if (port < 1024) {
+ ret = NF_DROP;
+ goto out;
+ }
+ ret = set_expected_rtp(pskb, ct, ctinfo,
+ ipaddr, port, dptr);
+ }
+ }
+out:
+ return ret;
+}
+
+static struct ip_conntrack_helper sip[MAX_PORTS];
+static char sip_names[MAX_PORTS][10];
+
+static void fini(void)
+{
+ int i;
+ for (i = 0; i < ports_c; i++) {
+ DEBUGP("unregistering helper for port %d\n", ports[i]);
+ ip_conntrack_helper_unregister(&sip[i]);
+ }
+}
+
+static int __init init(void)
+{
+ int i, ret;
+ char *tmpname;
+
+ if (ports_c == 0)
+ ports[ports_c++] = SIP_PORT;
+
+ for (i = 0; i < ports_c; i++) {
+ /* Create helper structure */
+ memset(&sip[i], 0, sizeof(struct ip_conntrack_helper));
+
+ sip[i].tuple.dst.protonum = IPPROTO_UDP;
+ sip[i].tuple.src.u.udp.port = htons(ports[i]);
+ sip[i].mask.src.u.udp.port = 0xFFFF;
+ sip[i].mask.dst.protonum = 0xFF;
+ sip[i].max_expected = 2;
+ sip[i].timeout = 3 * 60; /* 3 minutes */
+ sip[i].me = THIS_MODULE;
+ sip[i].help = sip_help;
+
+ tmpname = &sip_names[i][0];
+ if (ports[i] == SIP_PORT)
+ sprintf(tmpname, "sip");
+ else
+ sprintf(tmpname, "sip-%d", i);
+ sip[i].name = tmpname;
+
+ DEBUGP("port #%d: %d\n", i, ports[i]);
+
+ ret = ip_conntrack_helper_register(&sip[i]);
+ if (ret) {
+ printk("ERROR registering helper for port %d\n",
+ ports[i]);
+ fini();
+ return ret;
+ }
+ }
+ return 0;
+}
+
+module_init(init);
+module_exit(fini);
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