FreeBSD-5.3/lib/libalias/alias_irc.c
/*-
* 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: src/lib/libalias/alias_irc.c,v 1.18 2004/07/06 12:13:28 des Exp $");
/* 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 libalias *la,
struct ip *pip, /* IP packet to examine */
struct alias_link *lnk, /* 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 *)ip_next(pip);
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 < (int)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
* :) */
unsigned int copyat = i; /* Same */
unsigned 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_lnk;
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_lnk = FindUdpTcpOut(la, true_addr, destaddr,
true_port, 0,
IPPROTO_TCP, 1);
DBprintf(("Got a DCC link\n"));
if (dcc_lnk) {
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_lnk);
#endif
alias_address = GetAliasAddress(lnk);
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_lnk);
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(lnk);
delta = GetDeltaSeqOut(pip, lnk);
AddSeq(pip, lnk, 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.
*/