diff options
Diffstat (limited to 'package/rtsp/src/nf_nat_rtsp.c')
-rw-r--r-- | package/rtsp/src/nf_nat_rtsp.c | 489 |
1 files changed, 489 insertions, 0 deletions
diff --git a/package/rtsp/src/nf_nat_rtsp.c b/package/rtsp/src/nf_nat_rtsp.c new file mode 100644 index 000000000..6ec6aa4f8 --- /dev/null +++ b/package/rtsp/src/nf_nat_rtsp.c @@ -0,0 +1,489 @@ +/* + * RTSP extension for TCP NAT alteration + * (C) 2003 by Tom Marshall <tmarshall at real.com> + * based on ip_nat_irc.c + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + * Module load syntax: + * insmod nf_nat_rtsp.o ports=port1,port2,...port<MAX_PORTS> + * stunaddr=<address> + * destaction=[auto|strip|none] + * + * If no ports are specified, the default will be port 554 only. + * + * stunaddr specifies the address used to detect that a client is using STUN. + * If this address is seen in the destination parameter, it is assumed that + * the client has already punched a UDP hole in the firewall, so we don't + * mangle the client_port. If none is specified, it is autodetected. It + * only needs to be set if you have multiple levels of NAT. It should be + * set to the external address that the STUN clients detect. Note that in + * this case, it will not be possible for clients to use UDP with servers + * between the NATs. + * + * If no destaction is specified, auto is used. + * destaction=auto: strip destination parameter if it is not stunaddr. + * destaction=strip: always strip destination parameter (not recommended). + * destaction=none: do not touch destination parameter (not recommended). + */ + +#include <linux/module.h> +#include <net/tcp.h> +#include <net/netfilter/nf_nat_helper.h> +#include <net/netfilter/nf_nat_rule.h> +#include "nf_conntrack_rtsp.h" +#include <net/netfilter/nf_conntrack_expect.h> + +#include <linux/inet.h> +#include <linux/ctype.h> +#define NF_NEED_STRNCASECMP +#define NF_NEED_STRTOU16 +#include "netfilter_helpers.h" +#define NF_NEED_MIME_NEXTLINE +#include "netfilter_mime.h" + +#define MAX_PORTS 8 +#define DSTACT_AUTO 0 +#define DSTACT_STRIP 1 +#define DSTACT_NONE 2 + +static char* stunaddr = NULL; +static char* destaction = NULL; + +static u_int32_t extip = 0; +static int dstact = 0; + +MODULE_AUTHOR("Tom Marshall <tmarshall at real.com>"); +MODULE_DESCRIPTION("RTSP network address translation module"); +MODULE_LICENSE("GPL"); +module_param(stunaddr, charp, 0644); +MODULE_PARM_DESC(stunaddr, "Address for detecting STUN"); +module_param(destaction, charp, 0644); +MODULE_PARM_DESC(destaction, "Action for destination parameter (auto/strip/none)"); + +#define SKIP_WSPACE(ptr,len,off) while(off < len && isspace(*(ptr+off))) { off++; } + +/*** helper functions ***/ + +static void +get_skb_tcpdata(struct sk_buff* skb, char** pptcpdata, uint* ptcpdatalen) +{ + struct iphdr* iph = ip_hdr(skb); + struct tcphdr* tcph = (void *)iph + ip_hdrlen(skb); + + *pptcpdata = (char*)tcph + tcph->doff*4; + *ptcpdatalen = ((char*)skb_transport_header(skb) + skb->len) - *pptcpdata; +} + +/*** nat functions ***/ + +/* + * Mangle the "Transport:" header: + * - Replace all occurences of "client_port=<spec>" + * - Handle destination parameter + * + * In: + * ct, ctinfo = conntrack context + * skb = packet + * tranoff = Transport header offset from TCP data + * tranlen = Transport header length (incl. CRLF) + * rport_lo = replacement low port (host endian) + * rport_hi = replacement high port (host endian) + * + * Returns packet size difference. + * + * Assumes that a complete transport header is present, ending with CR or LF + */ +static int +rtsp_mangle_tran(enum ip_conntrack_info ctinfo, + struct nf_conntrack_expect* exp, + struct ip_ct_rtsp_expect* prtspexp, + struct sk_buff* skb, uint tranoff, uint tranlen) +{ + char* ptcp; + uint tcplen; + char* ptran; + char rbuf1[16]; /* Replacement buffer (one port) */ + uint rbuf1len; /* Replacement len (one port) */ + char rbufa[16]; /* Replacement buffer (all ports) */ + uint rbufalen; /* Replacement len (all ports) */ + u_int32_t newip; + u_int16_t loport, hiport; + uint off = 0; + uint diff; /* Number of bytes we removed */ + + struct nf_conn *ct = exp->master; + struct nf_conntrack_tuple *t; + + char szextaddr[15+1]; + uint extaddrlen; + int is_stun; + + get_skb_tcpdata(skb, &ptcp, &tcplen); + ptran = ptcp+tranoff; + + if (tranoff+tranlen > tcplen || tcplen-tranoff < tranlen || + tranlen < 10 || !iseol(ptran[tranlen-1]) || + nf_strncasecmp(ptran, "Transport:", 10) != 0) + { + pr_info("sanity check failed\n"); + return 0; + } + off += 10; + SKIP_WSPACE(ptcp+tranoff, tranlen, off); + + newip = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip; + t = &exp->tuple; + t->dst.u3.ip = newip; + + extaddrlen = extip ? sprintf(szextaddr, "%u.%u.%u.%u", NIPQUAD(extip)) + : sprintf(szextaddr, "%u.%u.%u.%u", NIPQUAD(newip)); + pr_debug("stunaddr=%s (%s)\n", szextaddr, (extip?"forced":"auto")); + + rbuf1len = rbufalen = 0; + switch (prtspexp->pbtype) + { + case pb_single: + for (loport = prtspexp->loport; loport != 0; loport++) /* XXX: improper wrap? */ + { + t->dst.u.udp.port = htons(loport); + if (nf_ct_expect_related(exp) == 0) + { + pr_debug("using port %hu\n", loport); + break; + } + } + if (loport != 0) + { + rbuf1len = sprintf(rbuf1, "%hu", loport); + rbufalen = sprintf(rbufa, "%hu", loport); + } + break; + case pb_range: + for (loport = prtspexp->loport; loport != 0; loport += 2) /* XXX: improper wrap? */ + { + t->dst.u.udp.port = htons(loport); + if (nf_ct_expect_related(exp) == 0) + { + hiport = loport + 1; //~exp->mask.dst.u.udp.port; + pr_debug("using ports %hu-%hu\n", loport, hiport); + break; + } + } + if (loport != 0) + { + rbuf1len = sprintf(rbuf1, "%hu", loport); + rbufalen = sprintf(rbufa, "%hu-%hu", loport, loport+1); + } + break; + case pb_discon: + for (loport = prtspexp->loport; loport != 0; loport++) /* XXX: improper wrap? */ + { + t->dst.u.udp.port = htons(loport); + if (nf_ct_expect_related(exp) == 0) + { + pr_debug("using port %hu (1 of 2)\n", loport); + break; + } + } + for (hiport = prtspexp->hiport; hiport != 0; hiport++) /* XXX: improper wrap? */ + { + t->dst.u.udp.port = htons(hiport); + if (nf_ct_expect_related(exp) == 0) + { + pr_debug("using port %hu (2 of 2)\n", hiport); + break; + } + } + if (loport != 0 && hiport != 0) + { + rbuf1len = sprintf(rbuf1, "%hu", loport); + if (hiport == loport+1) + { + rbufalen = sprintf(rbufa, "%hu-%hu", loport, hiport); + } + else + { + rbufalen = sprintf(rbufa, "%hu/%hu", loport, hiport); + } + } + break; + } + + if (rbuf1len == 0) + { + return 0; /* cannot get replacement port(s) */ + } + + /* Transport: tran;field;field=val,tran;field;field=val,... */ + while (off < tranlen) + { + uint saveoff; + const char* pparamend; + uint nextparamoff; + + pparamend = memchr(ptran+off, ',', tranlen-off); + pparamend = (pparamend == NULL) ? ptran+tranlen : pparamend+1; + nextparamoff = pparamend-ptcp; + + /* + * We pass over each param twice. On the first pass, we look for a + * destination= field. It is handled by the security policy. If it + * is present, allowed, and equal to our external address, we assume + * that STUN is being used and we leave the client_port= field alone. + */ + is_stun = 0; + saveoff = off; + while (off < nextparamoff) + { + const char* pfieldend; + uint nextfieldoff; + + pfieldend = memchr(ptran+off, ';', nextparamoff-off); + nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1; + + if (dstact != DSTACT_NONE && strncmp(ptran+off, "destination=", 12) == 0) + { + if (strncmp(ptran+off+12, szextaddr, extaddrlen) == 0) + { + is_stun = 1; + } + if (dstact == DSTACT_STRIP || (dstact == DSTACT_AUTO && !is_stun)) + { + diff = nextfieldoff-off; + if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, + off, diff, NULL, 0)) + { + /* mangle failed, all we can do is bail */ + nf_ct_unexpect_related(exp); + return 0; + } + get_skb_tcpdata(skb, &ptcp, &tcplen); + ptran = ptcp+tranoff; + tranlen -= diff; + nextparamoff -= diff; + nextfieldoff -= diff; + } + } + + off = nextfieldoff; + } + if (is_stun) + { + continue; + } + off = saveoff; + while (off < nextparamoff) + { + const char* pfieldend; + uint nextfieldoff; + + pfieldend = memchr(ptran+off, ';', nextparamoff-off); + nextfieldoff = (pfieldend == NULL) ? nextparamoff : pfieldend-ptran+1; + + if (strncmp(ptran+off, "client_port=", 12) == 0) + { + u_int16_t port; + uint numlen; + uint origoff; + uint origlen; + char* rbuf = rbuf1; + uint rbuflen = rbuf1len; + + off += 12; + origoff = (ptran-ptcp)+off; + origlen = 0; + numlen = nf_strtou16(ptran+off, &port); + off += numlen; + origlen += numlen; + if (port != prtspexp->loport) + { + pr_debug("multiple ports found, port %hu ignored\n", port); + } + else + { + if (ptran[off] == '-' || ptran[off] == '/') + { + off++; + origlen++; + numlen = nf_strtou16(ptran+off, &port); + off += numlen; + origlen += numlen; + rbuf = rbufa; + rbuflen = rbufalen; + } + + /* + * note we cannot just memcpy() if the sizes are the same. + * the mangle function does skb resizing, checks for a + * cloned skb, and updates the checksums. + * + * parameter 4 below is offset from start of tcp data. + */ + diff = origlen-rbuflen; + if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, + origoff, origlen, rbuf, rbuflen)) + { + /* mangle failed, all we can do is bail */ + nf_ct_unexpect_related(exp); + return 0; + } + get_skb_tcpdata(skb, &ptcp, &tcplen); + ptran = ptcp+tranoff; + tranlen -= diff; + nextparamoff -= diff; + nextfieldoff -= diff; + } + } + + off = nextfieldoff; + } + + off = nextparamoff; + } + + return 1; +} + +static uint +help_out(struct sk_buff *skb, enum ip_conntrack_info ctinfo, + unsigned int matchoff, unsigned int matchlen, struct ip_ct_rtsp_expect* prtspexp, + struct nf_conntrack_expect* exp) +{ + char* ptcp; + uint tcplen; + uint hdrsoff; + uint hdrslen; + uint lineoff; + uint linelen; + uint off; + + //struct iphdr* iph = (struct iphdr*)(*pskb)->nh.iph; + //struct tcphdr* tcph = (struct tcphdr*)((void*)iph + iph->ihl*4); + + get_skb_tcpdata(skb, &ptcp, &tcplen); + hdrsoff = matchoff;//exp->seq - ntohl(tcph->seq); + hdrslen = matchlen; + off = hdrsoff; + pr_debug("NAT rtsp help_out\n"); + + while (nf_mime_nextline(ptcp, hdrsoff+hdrslen, &off, &lineoff, &linelen)) + { + if (linelen == 0) + { + break; + } + if (off > hdrsoff+hdrslen) + { + pr_info("!! overrun !!"); + break; + } + pr_debug("hdr: len=%u, %.*s", linelen, (int)linelen, ptcp+lineoff); + + if (nf_strncasecmp(ptcp+lineoff, "Transport:", 10) == 0) + { + uint oldtcplen = tcplen; + pr_debug("hdr: Transport\n"); + if (!rtsp_mangle_tran(ctinfo, exp, prtspexp, skb, lineoff, linelen)) + { + pr_debug("hdr: Transport mangle failed"); + break; + } + get_skb_tcpdata(skb, &ptcp, &tcplen); + hdrslen -= (oldtcplen-tcplen); + off -= (oldtcplen-tcplen); + lineoff -= (oldtcplen-tcplen); + linelen -= (oldtcplen-tcplen); + pr_debug("rep: len=%u, %.*s", linelen, (int)linelen, ptcp+lineoff); + } + } + + return NF_ACCEPT; +} + +static unsigned int +help(struct sk_buff *skb, enum ip_conntrack_info ctinfo, + unsigned int matchoff, unsigned int matchlen, struct ip_ct_rtsp_expect* prtspexp, + struct nf_conntrack_expect* exp) +{ + int dir = CTINFO2DIR(ctinfo); + int rc = NF_ACCEPT; + + switch (dir) + { + case IP_CT_DIR_ORIGINAL: + rc = help_out(skb, ctinfo, matchoff, matchlen, prtspexp, exp); + break; + case IP_CT_DIR_REPLY: + pr_debug("unmangle ! %u\n", ctinfo); + /* XXX: unmangle */ + rc = NF_ACCEPT; + break; + } + //UNLOCK_BH(&ip_rtsp_lock); + + return rc; +} + +static void expected(struct nf_conn* ct, struct nf_conntrack_expect *exp) +{ + struct nf_nat_multi_range_compat mr; + u_int32_t newdstip, newsrcip, newip; + + struct nf_conn *master = ct->master; + + newdstip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; + newsrcip = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; + //FIXME (how to port that ?) + //code from 2.4 : newip = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC) ? newsrcip : newdstip; + newip = newdstip; + + pr_debug("newsrcip=%u.%u.%u.%u, newdstip=%u.%u.%u.%u, newip=%u.%u.%u.%u\n", + NIPQUAD(newsrcip), NIPQUAD(newdstip), NIPQUAD(newip)); + + mr.rangesize = 1; + // We don't want to manip the per-protocol, just the IPs. + mr.range[0].flags = IP_NAT_RANGE_MAP_IPS; + mr.range[0].min_ip = mr.range[0].max_ip = newip; + + nf_nat_setup_info(ct, &mr.range[0], IP_NAT_MANIP_DST); +} + + +static void __exit fini(void) +{ + nf_nat_rtsp_hook = NULL; + nf_nat_rtsp_hook_expectfn = NULL; + synchronize_net(); +} + +static int __init init(void) +{ + printk("nf_nat_rtsp v" IP_NF_RTSP_VERSION " loading\n"); + + BUG_ON(nf_nat_rtsp_hook); + nf_nat_rtsp_hook = help; + nf_nat_rtsp_hook_expectfn = &expected; + + if (stunaddr != NULL) + extip = in_aton(stunaddr); + + if (destaction != NULL) { + if (strcmp(destaction, "auto") == 0) + dstact = DSTACT_AUTO; + + if (strcmp(destaction, "strip") == 0) + dstact = DSTACT_STRIP; + + if (strcmp(destaction, "none") == 0) + dstact = DSTACT_NONE; + } + + return 0; +} + +module_init(init); +module_exit(fini); |