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-rw-r--r--lib/libalias/alias_irc.c357
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diff --git a/lib/libalias/alias_irc.c b/lib/libalias/alias_irc.c
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+/*-
+ * Copyright (c) 2001 Charles Mott <cm@linktel.net>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/* Alias_irc.c intercepts packages contain IRC CTCP commands, and
+ changes DCC commands to export a port on the aliasing host instead
+ of an aliased host.
+
+ For this routine to work, the DCC command must fit entirely into a
+ single TCP packet. This will usually happen, but is not
+ guaranteed.
+
+ The interception is likely to change the length of the packet.
+ The handling of this is copied more-or-less verbatim from
+ ftp_alias.c
+
+ Initial version: Eivind Eklund <perhaps@yes.no> (ee) 97-01-29
+
+ Version 2.1: May, 1997 (cjm)
+ Very minor changes to conform with
+ local/global/function naming conventions
+ withing the packet alising module.
+*/
+
+/* Includes */
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <limits.h>
+
+#include "alias_local.h"
+
+/* Local defines */
+#define DBprintf(a)
+
+
+void
+AliasHandleIrcOut(struct ip *pip, /* IP packet to examine */
+ struct alias_link *link, /* Which link are we on? */
+ int maxsize /* Maximum size of IP packet including headers */
+ )
+{
+ int hlen, tlen, dlen;
+ struct in_addr true_addr;
+ u_short true_port;
+ char *sptr;
+ struct tcphdr *tc;
+ int i; /* Iterator through the source */
+
+/* Calculate data length of TCP packet */
+ tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
+ hlen = (pip->ip_hl + tc->th_off) << 2;
+ tlen = ntohs(pip->ip_len);
+ dlen = tlen - hlen;
+
+ /* Return if data length is too short - assume an entire PRIVMSG in each packet. */
+ if (dlen<sizeof(":A!a@n.n PRIVMSG A :aDCC 1 1a")-1)
+ return;
+
+/* Place string pointer at beginning of data */
+ sptr = (char *) pip;
+ sptr += hlen;
+ maxsize -= hlen; /* We're interested in maximum size of data, not packet */
+
+ /* Search for a CTCP command [Note 1] */
+ for( i=0; i<dlen; i++ ) {
+ if(sptr[i]=='\001')
+ goto lFOUND_CTCP;
+ }
+ return; /* No CTCP commands in */
+ /* Handle CTCP commands - the buffer may have to be copied */
+lFOUND_CTCP:
+ {
+ char newpacket[65536]; /* Estimate of maximum packet size :) */
+ int copyat = i; /* Same */
+ int iCopy = 0; /* How much data have we written to copy-back string? */
+ unsigned long org_addr; /* Original IP address */
+ unsigned short org_port; /* Original source port address */
+ lCTCP_START:
+ if( i >= dlen || iCopy >= sizeof(newpacket) )
+ goto lPACKET_DONE;
+ newpacket[iCopy++] = sptr[i++]; /* Copy the CTCP start character */
+ /* Start of a CTCP */
+ if( i+4 >= dlen ) /* Too short for DCC */
+ goto lBAD_CTCP;
+ if( sptr[i+0] != 'D' )
+ goto lBAD_CTCP;
+ if( sptr[i+1] != 'C' )
+ goto lBAD_CTCP;
+ if( sptr[i+2] != 'C' )
+ goto lBAD_CTCP;
+ if( sptr[i+3] != ' ' )
+ goto lBAD_CTCP;
+ /* We have a DCC command - handle it! */
+ i+= 4; /* Skip "DCC " */
+ if( iCopy+4 > sizeof(newpacket) )
+ goto lPACKET_DONE;
+ newpacket[iCopy++] = 'D';
+ newpacket[iCopy++] = 'C';
+ newpacket[iCopy++] = 'C';
+ newpacket[iCopy++] = ' ';
+
+ DBprintf(("Found DCC\n"));
+ /* Skip any extra spaces (should not occur according to
+ protocol, but DCC breaks CTCP protocol anyway */
+ while(sptr[i] == ' ') {
+ if( ++i >= dlen) {
+ DBprintf(("DCC packet terminated in just spaces\n"));
+ goto lPACKET_DONE;
+ }
+ }
+
+ DBprintf(("Transferring command...\n"));
+ while(sptr[i] != ' ') {
+ newpacket[iCopy++] = sptr[i];
+ if( ++i >= dlen || iCopy >= sizeof(newpacket) ) {
+ DBprintf(("DCC packet terminated during command\n"));
+ goto lPACKET_DONE;
+ }
+ }
+ /* Copy _one_ space */
+ if( i+1 < dlen && iCopy < sizeof(newpacket) )
+ newpacket[iCopy++] = sptr[i++];
+
+ DBprintf(("Done command - removing spaces\n"));
+ /* Skip any extra spaces (should not occur according to
+ protocol, but DCC breaks CTCP protocol anyway */
+ while(sptr[i] == ' ') {
+ if( ++i >= dlen ) {
+ DBprintf(("DCC packet terminated in just spaces (post-command)\n"));
+ goto lPACKET_DONE;
+ }
+ }
+
+ DBprintf(("Transferring filename...\n"));
+ while(sptr[i] != ' ') {
+ newpacket[iCopy++] = sptr[i];
+ if( ++i >= dlen || iCopy >= sizeof(newpacket) ) {
+ DBprintf(("DCC packet terminated during filename\n"));
+ goto lPACKET_DONE;
+ }
+ }
+ /* Copy _one_ space */
+ if( i+1 < dlen && iCopy < sizeof(newpacket) )
+ newpacket[iCopy++] = sptr[i++];
+
+ DBprintf(("Done filename - removing spaces\n"));
+ /* Skip any extra spaces (should not occur according to
+ protocol, but DCC breaks CTCP protocol anyway */
+ while(sptr[i] == ' ') {
+ if( ++i >= dlen ) {
+ DBprintf(("DCC packet terminated in just spaces (post-filename)\n"));
+ goto lPACKET_DONE;
+ }
+ }
+
+ DBprintf(("Fetching IP address\n"));
+ /* Fetch IP address */
+ org_addr = 0;
+ while(i<dlen && isdigit(sptr[i])) {
+ if( org_addr > ULONG_MAX/10UL ) { /* Terminate on overflow */
+ DBprintf(("DCC Address overflow (org_addr == 0x%08lx, next char %c\n", org_addr, sptr[i]));
+ goto lBAD_CTCP;
+ }
+ org_addr *= 10;
+ org_addr += sptr[i++]-'0';
+ }
+ DBprintf(("Skipping space\n"));
+ if( i+1 >= dlen || sptr[i] != ' ' ) {
+ DBprintf(("Overflow (%d >= %d) or bad character (%02x) terminating IP address\n", i+1, dlen, sptr[i]));
+ goto lBAD_CTCP;
+ }
+ /* Skip any extra spaces (should not occur according to
+ protocol, but DCC breaks CTCP protocol anyway, so we might
+ as well play it safe */
+ while(sptr[i] == ' ') {
+ if( ++i >= dlen ) {
+ DBprintf(("Packet failure - space overflow.\n"));
+ goto lPACKET_DONE;
+ }
+ }
+ DBprintf(("Fetching port number\n"));
+ /* Fetch source port */
+ org_port = 0;
+ while(i<dlen && isdigit(sptr[i])) {
+ if( org_port > 6554 ) { /* Terminate on overflow (65536/10 rounded up*/
+ DBprintf(("DCC: port number overflow\n"));
+ goto lBAD_CTCP;
+ }
+ org_port *= 10;
+ org_port += sptr[i++]-'0';
+ }
+ /* Skip illegal addresses (or early termination) */
+ if( i >= dlen || (sptr[i] != '\001' && sptr[i] != ' ') ) {
+ DBprintf(("Bad port termination\n"));
+ goto lBAD_CTCP;
+ }
+ DBprintf(("Got IP %lu and port %u\n", org_addr, (unsigned)org_port));
+
+ /* We've got the address and port - now alias it */
+ {
+ struct alias_link *dcc_link;
+ struct in_addr destaddr;
+
+
+ true_port = htons(org_port);
+ true_addr.s_addr = htonl(org_addr);
+ destaddr.s_addr = 0;
+
+ /* Sanity/Security checking */
+ if (!org_addr || !org_port ||
+ pip->ip_src.s_addr != true_addr.s_addr ||
+ org_port < IPPORT_RESERVED)
+ goto lBAD_CTCP;
+
+ /* Steal the FTP_DATA_PORT - it doesn't really matter, and this
+ would probably allow it through at least _some_
+ firewalls. */
+ dcc_link = FindUdpTcpOut(true_addr, destaddr,
+ true_port, 0,
+ IPPROTO_TCP, 1);
+ DBprintf(("Got a DCC link\n"));
+ if ( dcc_link ) {
+ struct in_addr alias_address; /* Address from aliasing */
+ u_short alias_port; /* Port given by aliasing */
+ int n;
+
+#ifndef NO_FW_PUNCH
+ /* Generate firewall hole as appropriate */
+ PunchFWHole(dcc_link);
+#endif
+
+ alias_address = GetAliasAddress(link);
+ n = snprintf(&newpacket[iCopy],
+ sizeof(newpacket)-iCopy,
+ "%lu ", (u_long)htonl(alias_address.s_addr));
+ if( n < 0 ) {
+ DBprintf(("DCC packet construct failure.\n"));
+ goto lBAD_CTCP;
+ }
+ if( (iCopy += n) >= sizeof(newpacket) ) { /* Truncated/fit exactly - bad news */
+ DBprintf(("DCC constructed packet overflow.\n"));
+ goto lBAD_CTCP;
+ }
+ alias_port = GetAliasPort(dcc_link);
+ n = snprintf(&newpacket[iCopy],
+ sizeof(newpacket)-iCopy,
+ "%u", htons(alias_port) );
+ if( n < 0 ) {
+ DBprintf(("DCC packet construct failure.\n"));
+ goto lBAD_CTCP;
+ }
+ iCopy += n;
+ /* Done - truncated cases will be taken care of by lBAD_CTCP */
+ DBprintf(("Aliased IP %lu and port %u\n", alias_address.s_addr, (unsigned)alias_port));
+ }
+ }
+ /* An uninteresting CTCP - state entered right after '\001' has
+ been pushed. Also used to copy the rest of a DCC, after IP
+ address and port has been handled */
+ lBAD_CTCP:
+ for(; i<dlen && iCopy<sizeof(newpacket); i++,iCopy++) {
+ newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
+ if(sptr[i] == '\001') {
+ goto lNORMAL_TEXT;
+ }
+ }
+ goto lPACKET_DONE;
+ /* Normal text */
+ lNORMAL_TEXT:
+ for(; i<dlen && iCopy<sizeof(newpacket); i++,iCopy++) {
+ newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
+ if(sptr[i] == '\001') {
+ goto lCTCP_START;
+ }
+ }
+ /* Handle the end of a packet */
+ lPACKET_DONE:
+ iCopy = iCopy > maxsize-copyat ? maxsize-copyat : iCopy;
+ memcpy(sptr+copyat, newpacket, iCopy);
+
+/* Save information regarding modified seq and ack numbers */
+ {
+ int delta;
+
+ SetAckModified(link);
+ delta = GetDeltaSeqOut(pip, link);
+ AddSeq(pip, link, delta+copyat+iCopy-dlen);
+ }
+
+ /* Revise IP header */
+ {
+ u_short new_len;
+
+ new_len = htons(hlen + iCopy + copyat);
+ DifferentialChecksum(&pip->ip_sum,
+ &new_len,
+ &pip->ip_len,
+ 1);
+ pip->ip_len = new_len;
+ }
+
+ /* Compute TCP checksum for revised packet */
+ tc->th_sum = 0;
+ tc->th_sum = TcpChecksum(pip);
+ return;
+ }
+}
+
+/* Notes:
+ [Note 1]
+ The initial search will most often fail; it could be replaced with a 32-bit specific search.
+ Such a search would be done for 32-bit unsigned value V:
+ V ^= 0x01010101; (Search is for null bytes)
+ if( ((V-0x01010101)^V) & 0x80808080 ) {
+ (found a null bytes which was a 01 byte)
+ }
+ To assert that the processor is 32-bits, do
+ extern int ircdccar[32]; (32 bits)
+ extern int ircdccar[CHAR_BIT*sizeof(unsigned int)];
+ which will generate a type-error on all but 32-bit machines.
+
+ [Note 2] This routine really ought to be replaced with one that
+ creates a transparent proxy on the aliasing host, to allow arbitary
+ changes in the TCP stream. This should not be too difficult given
+ this base; I (ee) will try to do this some time later.
+ */
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