2 * Copyright (c) 2001 Charles Mott <cm@linktel.net>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
30 /* Alias_irc.c intercepts packages contain IRC CTCP commands, and
31 changes DCC commands to export a port on the aliasing host instead
34 For this routine to work, the DCC command must fit entirely into a
35 single TCP packet. This will usually happen, but is not
38 The interception is likely to change the length of the packet.
39 The handling of this is copied more-or-less verbatim from
42 Initial version: Eivind Eklund <perhaps@yes.no> (ee) 97-01-29
44 Version 2.1: May, 1997 (cjm)
45 Very minor changes to conform with
46 local/global/function naming conventions
47 withing the packet alising module.
52 #include <sys/param.h>
53 #include <sys/ctype.h>
54 #include <sys/limits.h>
55 #include <sys/systm.h>
56 #include <sys/kernel.h>
57 #include <sys/module.h>
60 #include <sys/types.h>
65 #include <netinet/in_systm.h>
66 #include <netinet/in.h>
67 #include <netinet/ip.h>
68 #include <netinet/tcp.h>
71 #include <netinet/libalias/alias.h>
72 #include <netinet/libalias/alias_local.h>
73 #include <netinet/libalias/alias_mod.h>
75 #include "alias_local.h"
76 #include "alias_mod.h"
79 #define IRC_CONTROL_PORT_NUMBER_1 6667
80 #define IRC_CONTROL_PORT_NUMBER_2 6668
86 AliasHandleIrcOut(struct libalias *, struct ip *, struct alias_link *,
90 fingerprint(struct libalias *la, struct ip *pip, struct alias_data *ah)
93 if (ah->dport == NULL || ah->dport == NULL || ah->lnk == NULL ||
96 if (ntohs(*ah->dport) == IRC_CONTROL_PORT_NUMBER_1
97 || ntohs(*ah->dport) == IRC_CONTROL_PORT_NUMBER_2)
103 protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
106 AliasHandleIrcOut(la, pip, ah->lnk, ah->maxpktsize);
110 struct proto_handler handlers[] = {
115 .fingerprint = &fingerprint,
116 .protohandler = &protohandler
122 mod_handler(module_t mod, int type, void *data)
129 LibAliasAttachHandlers(handlers);
133 LibAliasDetachHandlers(handlers);
144 moduledata_t alias_mod = {
145 "alias_irc", mod_handler, NULL
148 /* Kernel module definition. */
150 DECLARE_MODULE(alias_irc, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
151 MODULE_VERSION(alias_irc, 1);
152 MODULE_DEPEND(alias_irc, libalias, 1, 1, 1);
156 AliasHandleIrcOut(struct libalias *la,
157 struct ip *pip, /* IP packet to examine */
158 struct alias_link *lnk, /* Which link are we on? */
159 int maxsize /* Maximum size of IP packet including
163 int hlen, tlen, dlen;
164 struct in_addr true_addr;
168 int i; /* Iterator through the source */
170 /* Calculate data length of TCP packet */
171 tc = (struct tcphdr *)ip_next(pip);
172 hlen = (pip->ip_hl + tc->th_off) << 2;
173 tlen = ntohs(pip->ip_len);
177 * Return if data length is too short - assume an entire PRIVMSG in
180 if (dlen < (int)sizeof(":A!a@n.n PRIVMSG A :aDCC 1 1a") - 1)
183 /* Place string pointer at beginning of data */
186 maxsize -= hlen; /* We're interested in maximum size of
187 * data, not packet */
189 /* Search for a CTCP command [Note 1] */
190 for (i = 0; i < dlen; i++) {
191 if (sptr[i] == '\001')
194 return; /* No CTCP commands in */
195 /* Handle CTCP commands - the buffer may have to be copied */
198 char newpacket[65536]; /* Estimate of maximum packet size
200 unsigned int copyat = i; /* Same */
201 unsigned int iCopy = 0; /* How much data have we written to
202 * copy-back string? */
203 unsigned long org_addr; /* Original IP address */
204 unsigned short org_port; /* Original source port
208 if (i >= dlen || iCopy >= sizeof(newpacket))
210 newpacket[iCopy++] = sptr[i++]; /* Copy the CTCP start
212 /* Start of a CTCP */
213 if (i + 4 >= dlen) /* Too short for DCC */
215 if (sptr[i + 0] != 'D')
217 if (sptr[i + 1] != 'C')
219 if (sptr[i + 2] != 'C')
221 if (sptr[i + 3] != ' ')
223 /* We have a DCC command - handle it! */
224 i += 4; /* Skip "DCC " */
225 if (iCopy + 4 > sizeof(newpacket))
227 newpacket[iCopy++] = 'D';
228 newpacket[iCopy++] = 'C';
229 newpacket[iCopy++] = 'C';
230 newpacket[iCopy++] = ' ';
232 DBprintf(("Found DCC\n"));
234 * Skip any extra spaces (should not occur according to
235 * protocol, but DCC breaks CTCP protocol anyway
237 while (sptr[i] == ' ') {
239 DBprintf(("DCC packet terminated in just spaces\n"));
244 DBprintf(("Transferring command...\n"));
245 while (sptr[i] != ' ') {
246 newpacket[iCopy++] = sptr[i];
247 if (++i >= dlen || iCopy >= sizeof(newpacket)) {
248 DBprintf(("DCC packet terminated during command\n"));
252 /* Copy _one_ space */
253 if (i + 1 < dlen && iCopy < sizeof(newpacket))
254 newpacket[iCopy++] = sptr[i++];
256 DBprintf(("Done command - removing spaces\n"));
258 * Skip any extra spaces (should not occur according to
259 * protocol, but DCC breaks CTCP protocol anyway
261 while (sptr[i] == ' ') {
263 DBprintf(("DCC packet terminated in just spaces (post-command)\n"));
268 DBprintf(("Transferring filename...\n"));
269 while (sptr[i] != ' ') {
270 newpacket[iCopy++] = sptr[i];
271 if (++i >= dlen || iCopy >= sizeof(newpacket)) {
272 DBprintf(("DCC packet terminated during filename\n"));
276 /* Copy _one_ space */
277 if (i + 1 < dlen && iCopy < sizeof(newpacket))
278 newpacket[iCopy++] = sptr[i++];
280 DBprintf(("Done filename - removing spaces\n"));
282 * Skip any extra spaces (should not occur according to
283 * protocol, but DCC breaks CTCP protocol anyway
285 while (sptr[i] == ' ') {
287 DBprintf(("DCC packet terminated in just spaces (post-filename)\n"));
292 DBprintf(("Fetching IP address\n"));
293 /* Fetch IP address */
295 while (i < dlen && isdigit(sptr[i])) {
296 if (org_addr > ULONG_MAX / 10UL) { /* Terminate on overflow */
297 DBprintf(("DCC Address overflow (org_addr == 0x%08lx, next char %c\n", org_addr, sptr[i]));
301 org_addr += sptr[i++] - '0';
303 DBprintf(("Skipping space\n"));
304 if (i + 1 >= dlen || sptr[i] != ' ') {
305 DBprintf(("Overflow (%d >= %d) or bad character (%02x) terminating IP address\n", i + 1, dlen, sptr[i]));
309 * Skip any extra spaces (should not occur according to
310 * protocol, but DCC breaks CTCP protocol anyway, so we
311 * might as well play it safe
313 while (sptr[i] == ' ') {
315 DBprintf(("Packet failure - space overflow.\n"));
319 DBprintf(("Fetching port number\n"));
320 /* Fetch source port */
322 while (i < dlen && isdigit(sptr[i])) {
323 if (org_port > 6554) { /* Terminate on overflow
324 * (65536/10 rounded up */
325 DBprintf(("DCC: port number overflow\n"));
329 org_port += sptr[i++] - '0';
331 /* Skip illegal addresses (or early termination) */
332 if (i >= dlen || (sptr[i] != '\001' && sptr[i] != ' ')) {
333 DBprintf(("Bad port termination\n"));
336 DBprintf(("Got IP %lu and port %u\n", org_addr, (unsigned)org_port));
338 /* We've got the address and port - now alias it */
340 struct alias_link *dcc_lnk;
341 struct in_addr destaddr;
344 true_port = htons(org_port);
345 true_addr.s_addr = htonl(org_addr);
348 /* Sanity/Security checking */
349 if (!org_addr || !org_port ||
350 pip->ip_src.s_addr != true_addr.s_addr ||
351 org_port < IPPORT_RESERVED)
355 * Steal the FTP_DATA_PORT - it doesn't really
356 * matter, and this would probably allow it through
357 * at least _some_ firewalls.
359 dcc_lnk = FindUdpTcpOut(la, true_addr, destaddr,
362 DBprintf(("Got a DCC link\n"));
364 struct in_addr alias_address; /* Address from aliasing */
365 u_short alias_port; /* Port given by
370 /* Generate firewall hole as appropriate */
371 PunchFWHole(dcc_lnk);
374 alias_address = GetAliasAddress(lnk);
375 n = snprintf(&newpacket[iCopy],
376 sizeof(newpacket) - iCopy,
377 "%lu ", (u_long) htonl(alias_address.s_addr));
379 DBprintf(("DCC packet construct failure.\n"));
382 if ((iCopy += n) >= sizeof(newpacket)) { /* Truncated/fit exactly
384 DBprintf(("DCC constructed packet overflow.\n"));
387 alias_port = GetAliasPort(dcc_lnk);
388 n = snprintf(&newpacket[iCopy],
389 sizeof(newpacket) - iCopy,
390 "%u", htons(alias_port));
392 DBprintf(("DCC packet construct failure.\n"));
397 * Done - truncated cases will be taken
398 * care of by lBAD_CTCP
400 DBprintf(("Aliased IP %lu and port %u\n", alias_address.s_addr, (unsigned)alias_port));
404 * An uninteresting CTCP - state entered right after '\001'
405 * has been pushed. Also used to copy the rest of a DCC,
406 * after IP address and port has been handled
409 for (; i < dlen && iCopy < sizeof(newpacket); i++, iCopy++) {
410 newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
411 if (sptr[i] == '\001') {
418 for (; i < dlen && iCopy < sizeof(newpacket); i++, iCopy++) {
419 newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
420 if (sptr[i] == '\001') {
424 /* Handle the end of a packet */
426 iCopy = iCopy > maxsize - copyat ? maxsize - copyat : iCopy;
427 memcpy(sptr + copyat, newpacket, iCopy);
429 /* Save information regarding modified seq and ack numbers */
434 delta = GetDeltaSeqOut(pip, lnk);
435 AddSeq(pip, lnk, delta + copyat + iCopy - dlen);
438 /* Revise IP header */
442 new_len = htons(hlen + iCopy + copyat);
443 DifferentialChecksum(&pip->ip_sum,
447 pip->ip_len = new_len;
450 /* Compute TCP checksum for revised packet */
455 tc->th_sum = TcpChecksum(pip);
463 The initial search will most often fail; it could be replaced with a 32-bit specific search.
464 Such a search would be done for 32-bit unsigned value V:
465 V ^= 0x01010101; (Search is for null bytes)
466 if( ((V-0x01010101)^V) & 0x80808080 ) {
467 (found a null bytes which was a 01 byte)
469 To assert that the processor is 32-bits, do
470 extern int ircdccar[32]; (32 bits)
471 extern int ircdccar[CHAR_BIT*sizeof(unsigned int)];
472 which will generate a type-error on all but 32-bit machines.
474 [Note 2] This routine really ought to be replaced with one that
475 creates a transparent proxy on the aliasing host, to allow arbitary
476 changes in the TCP stream. This should not be too difficult given
477 this base; I (ee) will try to do this some time later.