diff options
Diffstat (limited to 'net/ipv4/netfilter/ip_conntrack_sip.c')
| -rw-r--r-- | net/ipv4/netfilter/ip_conntrack_sip.c | 471 |
1 files changed, 471 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ip_conntrack_sip.c b/net/ipv4/netfilter/ip_conntrack_sip.c new file mode 100644 index 0000000000000..fc87ce0da40d3 --- /dev/null +++ b/net/ipv4/netfilter/ip_conntrack_sip.c @@ -0,0 +1,471 @@ +/* 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/config.h> +#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 = 1; + 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); |