358 lines
12 KiB
C
358 lines
12 KiB
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("$FreeBSD$");
|
|
|
|
/* 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.
|
|
*/
|