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Add address translation support for RTSP/RTP used by RealPlayer and

Browse Source 
Quicktime streaming media applications.

Add a BUGS section to the man page.

Submitted by:	Erik Salander <erik@whistle.com>
This commit is contained in:
Archie Cobbs 2000-07-26 23:15:46 +00:00
parent a6c8be39c9
commit 642e43b39b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=63899
16 changed files with 1638 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lib/libalias/HISTORY
View File

@ -139,3 +139,7 @@ Version 3.1: May, 2000 (Erik Salander, erik@whistle.com)
- Added support to alias 227 replies, allows aliasing for
FTP servers in passive mode.
- Added support for PPTP aliasing.
Version 3.2: July, 2000 (Erik Salander, erik@whistle.com and
Junichi Satoh, junichi@junichi.org)
- Added support for streaming media (RTSP and PNA) aliasing.

3
lib/libalias/Makefile
View File

@ -5,7 +5,8 @@ SHLIB_MAJOR= 4
SHLIB_MINOR= 0
CFLAGS+= -Wall -I${.CURDIR}
SRCS= alias.c alias_cuseeme.c alias_db.c alias_ftp.c alias_irc.c \
alias_nbt.c alias_pptp.c alias_proxy.c alias_util.c
alias_nbt.c alias_pptp.c alias_proxy.c alias_smedia.c \
alias_util.c
INCS= alias.h
MAN3= libalias.3

135
lib/libalias/alias.c
View File

@ -76,9 +76,13 @@
Version 2.3 Dec 1998 (dillon)
- Major bounds checking additions, see FreeBSD/CVS
Version 3.1 May, 2000 (eds)
Version 3.1 May, 2000 (salander)
- Added hooks to handle PPTP.
Version 3.2 July, 2000 (salander and satoh)
- Added PacketUnaliasOut routine.
- Added hooks to handle RTSP/RTP.
See HISTORY file for additional revisions.
$FreeBSD$
@ -102,6 +106,8 @@
#define IRC_CONTROL_PORT_NUMBER_1 6667
#define IRC_CONTROL_PORT_NUMBER_2 6668
#define CUSEEME_PORT_NUMBER 7648
#define RTSP_CONTROL_PORT_NUMBER_1 554
#define RTSP_CONTROL_PORT_NUMBER_2 7070
#define PPTP_CONTROL_PORT_NUMBER 1723
@ -1112,6 +1118,11 @@ TcpAliasOut(struct ip *pip, int maxpacketsize)
else if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
AliasHandleIrcOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_2)
AliasHandleRtspOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
|| ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
AliasHandlePptpOut(pip, link);
@ -1236,6 +1247,7 @@ FragmentOut(struct ip *pip)
PacketAliasFragmentIn()
PacketAliasIn()
PacketAliasOut()
PacketUnaliasOut()
(prototypes in alias.h)
*/
@ -1465,3 +1477,124 @@ PacketAliasOut(char *ptr, /* valid IP packet */
SetDefaultAliasAddress(addr_save);
return(iresult);
}
int
PacketUnaliasOut(char *ptr, /* valid IP packet */
int maxpacketsize /* for error checking */
)
{
struct ip *pip;
struct icmp *ic;
struct udphdr *ud;
struct tcphdr *tc;
struct alias_link *link;
int iresult = PKT_ALIAS_IGNORED;
pip = (struct ip *) ptr;
/* Defense against mangled packets */
if (ntohs(pip->ip_len) > maxpacketsize
|| (pip->ip_hl<<2) > maxpacketsize)
return(iresult);
ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
tc = (struct tcphdr *) ud;
ic = (struct icmp *) ud;
/* Find a link */
if (pip->ip_p == IPPROTO_UDP)
link = QueryUdpTcpIn(pip->ip_dst, pip->ip_src,
ud->uh_dport, ud->uh_sport,
IPPROTO_UDP);
else if (pip->ip_p == IPPROTO_TCP)
link = QueryUdpTcpIn(pip->ip_dst, pip->ip_src,
tc->th_dport, tc->th_sport,
IPPROTO_TCP);
else if (pip->ip_p == IPPROTO_ICMP)
link = FindIcmpIn(pip->ip_dst, pip->ip_src, ic->icmp_id);
else
link = NULL;
/* Change it from an aliased packet to an unaliased packet */
if (link != NULL)
{
if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP)
{
u_short *sptr;
int accumulate;
struct in_addr original_address;
u_short original_port;
original_address = GetOriginalAddress(link);
original_port = GetOriginalPort(link);
/* Adjust TCP/UDP checksum */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
if (pip->ip_p == IPPROTO_UDP) {
accumulate += ud->uh_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, ud->uh_sum)
} else {
accumulate += tc->th_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, tc->th_sum)
}
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &original_address,
(u_short *) &pip->ip_src,
2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
if (pip->ip_p == IPPROTO_UDP)
ud->uh_sport = original_port;
else
tc->th_sport = original_port;
iresult = PKT_ALIAS_OK;
} else if (pip->ip_p == IPPROTO_ICMP) {
u_short *sptr;
int accumulate;
struct in_addr original_address;
u_short original_id;
original_address = GetOriginalAddress(link);
original_id = GetOriginalPort(link);
/* Adjust ICMP checksum */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
accumulate += ic->icmp_id;
accumulate -= original_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum)
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &original_address,
(u_short *) &pip->ip_src,
2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
ic->icmp_id = original_id;
iresult = PKT_ALIAS_OK;
}
}
return(iresult);
}

3
lib/libalias/alias.h
View File

@ -44,6 +44,9 @@ struct alias_link;
extern int
PacketAliasOut(char *, int maxpacketsize);
extern int
PacketUnaliasOut(char *, int maxpacketsize);
/* Port and Address Redirection */
extern struct alias_link *
PacketAliasRedirectPort(struct in_addr, u_short,

213
lib/libalias/alias_db.c
View File

@ -103,6 +103,16 @@
version of PacketAliasPermanentLink(). The second function
implements static network address translation.
Version 3.2: July, 2000 (salander and satoh)
Added FindNewPortGroup to get contiguous range of port values.
Added QueryUdpTcpIn and QueryUdpTcpOut to look for an aliasing
link but not actually add one.
Added FindRtspOut, which is closely derived from FindUdpTcpOut,
except that the alias port (from FindNewPortGroup) is provided
as input.
See HISTORY file for additional revisions.
$FreeBSD$
@ -500,6 +510,9 @@ Link creation and deletion:
Link search:
FindLinkOut() - find link for outgoing packets
FindLinkIn() - find link for incoming packets
Port search:
FindNewPortGroup() - find an available group of ports
*/
/* Local prototypes */
@ -531,11 +544,14 @@ FindLinkIn(struct in_addr, struct in_addr, u_short, u_short, int, int);
#define ALIAS_PORT_BASE 0x08000
#define ALIAS_PORT_MASK 0x07fff
#define ALIAS_PORT_MASK_EVEN 0x07ffe
#define GET_NEW_PORT_MAX_ATTEMPTS 20
#define GET_ALIAS_PORT -1
#define GET_ALIAS_ID GET_ALIAS_PORT
#define FIND_EVEN_ALIAS_BASE 1
/* GetNewPort() allocates port numbers. Note that if a port number
is already in use, that does not mean that it cannot be used by
another link concurrently. This is because GetNewPort() looks for
@ -704,6 +720,102 @@ GetSocket(u_short port_net, int *sockfd, int link_type)
}
/* FindNewPortGroup() returns a base port number for an available
range of contiguous port numbers. Note that if a port number
is already in use, that does not mean that it cannot be used by
another link concurrently. This is because FindNewPortGroup()
looks for unused triplets: (dest addr, dest port, alias port). */
int
FindNewPortGroup(struct in_addr dst_addr,
struct in_addr alias_addr,
u_short src_port,
u_short dst_port,
u_short port_count,
u_char proto,
u_char align)
{
int i, j;
int max_trials;
u_short port_sys;
int link_type;
/*
* Get link_type from protocol
*/
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return (0);
break;
}
/*
* The aliasing port is automatically selected
* by one of two methods below:
*/
max_trials = GET_NEW_PORT_MAX_ATTEMPTS;
if (packetAliasMode & PKT_ALIAS_SAME_PORTS) {
/*
* When the ALIAS_SAME_PORTS option is
* chosen, the first try will be the
* actual source port. If this is already
* in use, the remainder of the trials
* will be random.
*/
port_sys = ntohs(src_port);
} else {
/* First trial and all subsequent are random. */
if (align == FIND_EVEN_ALIAS_BASE)
port_sys = random() & ALIAS_PORT_MASK_EVEN;
else
port_sys = random() & ALIAS_PORT_MASK;
port_sys += ALIAS_PORT_BASE;
}
/* Port number search */
for (i = 0; i < max_trials; i++) {
struct alias_link *search_result;
for (j = 0; j < port_count; j++)
if (0 != (search_result = FindLinkIn(dst_addr, alias_addr,
dst_port, htons(port_sys + j),
link_type, 0)))
break;
/* Found a good range, return base */
if (j == port_count)
return (htons(port_sys));
/* Find a new base to try */
if (align == FIND_EVEN_ALIAS_BASE)
port_sys = random() & ALIAS_PORT_MASK_EVEN;
else
port_sys = random() & ALIAS_PORT_MASK;
port_sys += ALIAS_PORT_BASE;
}
#ifdef DEBUG
fprintf(stderr, "PacketAlias/FindNewPortGroup(): ");
fprintf(stderr, "could not find free port(s)\n");
#endif
return(0);
}
static void
CleanupAliasData(void)
{
@ -1600,6 +1712,107 @@ FindPptpOut(struct in_addr src_addr,
}
struct alias_link *
QueryUdpTcpIn(struct in_addr dst_addr,
struct in_addr alias_addr,
u_short dst_port,
u_short alias_port,
u_char proto)
{
int link_type;
struct alias_link *link;
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return NULL;
break;
}
link = FindLinkIn(dst_addr, alias_addr,
dst_port, alias_port,
link_type, 0);
return(link);
}
struct alias_link *
QueryUdpTcpOut(struct in_addr src_addr,
struct in_addr dst_addr,
u_short src_port,
u_short dst_port,
u_char proto)
{
int link_type;
struct alias_link *link;
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return NULL;
break;
}
link = FindLinkOut(src_addr, dst_addr,
src_port, dst_port,
link_type, 0);
return(link);
}
struct alias_link *
FindRtspOut(struct in_addr src_addr,
struct in_addr dst_addr,
u_short src_port,
u_short alias_port,
u_char proto)
{
int link_type;
struct alias_link *link;
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return NULL;
break;
}
link = FindLinkOut(src_addr, dst_addr, src_port, 0, link_type, 1);
if (link == NULL)
{
struct in_addr alias_addr;
alias_addr = FindAliasAddress(src_addr);
link = AddLink(src_addr, dst_addr, alias_addr,
src_port, 0, alias_port,
link_type);
}
return(link);
}
struct in_addr
FindOriginalAddress(struct in_addr alias_addr)
{

14
lib/libalias/alias_local.h
View File

@ -113,6 +113,15 @@ FindPptpIn(struct in_addr, struct in_addr, u_short);
struct alias_link *
FindPptpOut(struct in_addr, struct in_addr, u_short);
struct alias_link *
QueryUdpTcpIn (struct in_addr, struct in_addr, u_short, u_short, u_char);
struct alias_link *
QueryUdpTcpOut(struct in_addr, struct in_addr, u_short, u_short, u_char);
struct alias_link *
FindRtspOut(struct in_addr, struct in_addr, u_short, u_short, u_char);
struct in_addr
FindOriginalAddress(struct in_addr);
@ -120,6 +129,8 @@ struct in_addr
FindAliasAddress(struct in_addr);
/* External data access/modification */
int FindNewPortGroup(struct in_addr, struct in_addr,
u_short, u_short, u_short, u_char, u_char);
void GetFragmentAddr(struct alias_link *, struct in_addr *);
void SetFragmentAddr(struct alias_link *, struct in_addr);
void GetFragmentPtr(struct alias_link *, char **);
@ -165,6 +176,9 @@ void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
/* IRC routines */
void AliasHandleIrcOut(struct ip *, struct alias_link *, int);
/* RTSP routines */
void AliasHandleRtspOut(struct ip *, struct alias_link *, int);
/* PPTP routines */
int PptpGetCallID(struct ip *, u_short *);
void PptpSetCallID(struct ip *, u_short);

427
lib/libalias/alias_smedia.c Normal file
View File

@ -0,0 +1,427 @@
/*
* alias_smedia.c
*
* Copyright (c) 2000 Whistle Communications, Inc.
* All rights reserved.
*
* Subject to the following obligations and disclaimer of warranty, use and
* redistribution of this software, in source or object code forms, with or
* without modifications are expressly permitted by Whistle Communications;
* provided, however, that:
* 1. Any and all reproductions of the source or object code must include the
* copyright notice above and the following disclaimer of warranties; and
* 2. No rights are granted, in any manner or form, to use Whistle
* Communications, Inc. trademarks, including the mark "WHISTLE
* COMMUNICATIONS" on advertising, endorsements, or otherwise except as
* such appears in the above copyright notice or in the software.
*
* THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
* TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
* REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
* INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
* WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
* REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
* SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
* IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
* RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
* WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
* PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* Copyright (c) 2000 Junichi SATOH <junichi@astec.co.jp>
* <junichi@junichi.org>
* 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.
*
* Authors: Erik Salander <erik@whistle.com>
* Junichi SATOH <junichi@astec.co.jp>
* <junichi@junichi.org>
*
* $FreeBSD$
*/
/*
Alias_smedia.c is meant to contain the aliasing code for streaming media
protocols. It performs special processing for RSTP sessions under TCP.
Specifically, when a SETUP request is sent by a client, or a 200 reply
is sent by a server, it is intercepted and modified. The address is
changed to the gateway machine and an aliasing port is used.
More specifically, the "client_port" configuration parameter is
parsed for SETUP requests. The "server_port" configuration parameter is
parsed for 200 replies eminating from a server. This is intended to handle
the unicast case.
RTSP also allows a redirection of a stream to another client by using the
"destination" configuration parameter. The destination config parm would
indicate a different IP address. This function is NOT supported by the
RTSP translation code below.
The RTSP multicast functions without any address translation intervention.
For this routine to work, the SETUP/200 must fit entirely
into a single TCP packet. This is typically the case, but exceptions
can easily be envisioned under the actual specifications.
Probably the most troubling aspect of the approach taken here is
that the new SETUP/200 will typically be a different length, and
this causes a certain amount of bookkeeping to keep track of the
changes of sequence and acknowledgment numbers, since the client
machine is totally unaware of the modification to the TCP stream.
Initial version: May, 2000 (eds)
*/
#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 <netinet/udp.h>
#include "alias_local.h"
#define RTSP_CONTROL_PORT_NUMBER_1 554
#define RTSP_CONTROL_PORT_NUMBER_2 7070
#define RTSP_PORT_GROUP 2
#define ISDIGIT(a) (((a) >= '0') && ((a) <= '9'))
int search_string(char *data, int dlen, char *search_str)
{
int i, j, k;
int search_str_len;
search_str_len = strlen(search_str);
for (i = 0; i < dlen - search_str_len; i++) {
for (j = i, k = 0; j < dlen - search_str_len; j++, k++) {
if (data[j] != search_str[k] &&
data[j] != search_str[k] - ('a' - 'A')) {
break;
}
if (k == search_str_len - 1) {
return j + 1;
}
}
}
return -1;
}
int alias_rtsp_out(struct ip *pip,
struct alias_link *link,
char *data,
char *port_str)
{
int hlen, tlen, dlen;
struct tcphdr *tc;
int i, j, pos, state, port_dlen, new_dlen, delta;
u_short p[2], new_len;
u_short sport, eport, base_port;
u_short salias = 0, ealias = 0, base_alias = 0;
char *transport_str = "transport:";
char newdata[2048], *port_data, *port_newdata, stemp[80];
int links_created = 0, pkt_updated = 0;
struct alias_link *rtsp_link = NULL;
struct in_addr null_addr;
/* 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;
/* Find keyword, "Transport: " */
pos = search_string(data, dlen, transport_str);
if (pos < 0) {
return -1;
}
port_data = data + pos;
port_dlen = dlen - pos;
memcpy(newdata, data, pos);
port_newdata = newdata + pos;
while (port_dlen > strlen(port_str)) {
/* Find keyword, appropriate port string */
pos = search_string(port_data, port_dlen, port_str);
if (pos < 0) {
break;
}
memcpy (port_newdata, port_data, pos + 1);
port_newdata += (pos + 1);
p[0] = p[1] = 0;
sport = eport = 0;
state = 0;
for (i = pos; i < port_dlen; i++) {
switch(state) {
case 0:
if (port_data[i] == '=') {
state++;
}
break;
case 1:
if (ISDIGIT(port_data[i])) {
p[0] = p[0] * 10 + port_data[i] - '0';
} else {
if (port_data[i] == ';') {
state = 3;
}
if (port_data[i] == '-') {
state++;
}
}
break;
case 2:
if (ISDIGIT(port_data[i])) {
p[1] = p[1] * 10 + port_data[i] - '0';
} else {
state++;
}
break;
case 3:
base_port = p[0];
sport = htons(p[0]);
eport = htons(p[1]);
if (!links_created) {
links_created = 1;
/* Find an even numbered port number base that
satisfies the contiguous number of ports we need */
null_addr.s_addr = 0;
if (0 == (salias = FindNewPortGroup(null_addr,
FindAliasAddress(pip->ip_src),
sport, 0,
RTSP_PORT_GROUP,
IPPROTO_UDP, 1))) {
#ifdef DEBUG
fprintf(stderr,
"PacketAlias/RTSP: Cannot find contiguous RTSP data ports\n");
#endif
} else {
base_alias = ntohs(salias);
for (j = 0; j < RTSP_PORT_GROUP; j++) {
/* Establish link to port found in RTSP packet */
rtsp_link = FindRtspOut(GetOriginalAddress(link), null_addr,
htons(base_port + j), htons(base_alias + j),
IPPROTO_UDP);
if (rtsp_link != NULL) {
#ifndef NO_FW_PUNCH
/* Punch hole in firewall */
PunchFWHole(rtsp_link);
#endif
} else {
#ifdef DEBUG
fprintf(stderr,
"PacketAlias/RTSP: Cannot allocate RTSP data ports\n");
#endif
break;
}
}
}
ealias = htons(base_alias + (RTSP_PORT_GROUP - 1));
}
if (salias && rtsp_link) {
pkt_updated = 1;
/* Copy into IP packet */
sprintf(stemp, "%d", ntohs(salias));
memcpy(port_newdata, stemp, strlen(stemp));
port_newdata += strlen(stemp);
if (eport != 0) {
*port_newdata = '-';
port_newdata++;
/* Copy into IP packet */
sprintf(stemp, "%d", ntohs(ealias));
memcpy(port_newdata, stemp, strlen(stemp));
port_newdata += strlen(stemp);
}
*port_newdata = ';';
port_newdata++;
}
state++;
break;
}
if (state > 3) {
break;
}
}
port_data += i;
port_dlen -= i;
}
if (!pkt_updated)
return -1;
memcpy (port_newdata, port_data, port_dlen);
port_newdata += port_dlen;
*port_newdata = '\0';
/* Create new packet */
new_dlen = port_newdata - newdata;
memcpy (data, newdata, new_dlen);
SetAckModified(link);
delta = GetDeltaSeqOut(pip, link);
AddSeq(pip, link, delta + new_dlen - dlen);
new_len = htons(hlen + new_dlen);
DifferentialChecksum(&pip->ip_sum,
&new_len,
&pip->ip_len,
1);
pip->ip_len = new_len;
tc->th_sum = 0;
tc->th_sum = TcpChecksum(pip);
return 0;
}
/* Support the protocol used by early versions of RealPlayer */
int alias_pna_out(struct ip *pip,
struct alias_link *link,
char *data,
int dlen)
{
struct alias_link *pna_links;
u_short msg_id, msg_len;
char *work;
u_short alias_port, port;
struct tcphdr *tc;
work = data;
work += 5;
while (work + 4 < data + dlen) {
memcpy(&msg_id, work, 2);
work += 2;
memcpy(&msg_len, work, 2);
work += 2;
if (ntohs(msg_id) == 0) {
/* end of options */
return 0;
}
if ((ntohs(msg_id) == 1) || (ntohs(msg_id) == 7)) {
memcpy((char*)&port, (char*)work, 2);
pna_links = FindUdpTcpOut(pip->ip_src, GetDestAddress(link),
port, 0, IPPROTO_UDP);
if (pna_links != NULL) {
#ifndef NO_FW_PUNCH
/* Punch hole in firewall */
PunchFWHole(pna_links);
#endif
tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
alias_port = GetAliasPort(pna_links);
memcpy((char*)work, (char*)&alias_port, 2);
/* Compute TCP checksum for revised packet */
tc->th_sum = 0;
tc->th_sum = TcpChecksum(pip);
}
}
work += ntohs(msg_len);
}
return 0;
}
void
AliasHandleRtspOut(struct ip *pip, struct alias_link *link, int maxpacketsize)
{
int hlen, tlen, dlen;
struct tcphdr *tc;
char *data, *setup = "SETUP", *pna = "PNA", *str200 = "200", *okstr = "OK";
char *client_port_str = "client_port", *server_port_str = "server_port";
int i, parseOk;
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;
data = (char*)pip;
data += hlen;
/* When aliasing a client, check for the SETUP request */
if ((ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1) ||
(ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2)) {
if (dlen >= strlen(setup)) {
if (memcmp(data, setup, strlen(setup)) == 0) {
alias_rtsp_out(pip, link, data, client_port_str);
return;
}
}
if (dlen >= strlen(pna)) {
if (memcmp(data, pna, strlen(pna)) == 0) {
alias_pna_out(pip, link, data, dlen);
}
}
} else {
/* When aliasing a server, check for the 200 reply
Accomodate varying number of blanks between 200 & OK */
if (dlen >= strlen(str200)) {
for (parseOk = 0, i = 0;
i <= dlen - strlen(str200);
i++) {
if (memcmp(&data[i], str200, strlen(str200)) == 0) {
parseOk = 1;
break;
}
}
if (parseOk) {
i += strlen(str200); /* skip string found */
while(data[i] == ' ') /* skip blank(s) */
i++;
if ((dlen - i) >= strlen(okstr)) {
if (memcmp(&data[i], okstr, strlen(okstr)) == 0)
alias_rtsp_out(pip, link, data, server_port_str);
}
}
}
}
}

23
lib/libalias/libalias.3
View File

@ -808,6 +808,25 @@ If the checksum is valid,
.Fn PacketAliasInternetChecksum
will return zero.
.Ed
.Pp
.Ft int
.Fn PacketUnaliasOut "char *buffer" "int maxpacketsize"
.Bd -ragged -offset indent
An outgoing packet, which has already been aliased, has its private address/port
information restored by this function.
The IP packet is pointed to by
.Fa buffer ,
and
.Fa maxpacketsize
is provided for error checking purposes.
This function can be used if an already-aliased packet needs to have its
original IP header restored for further processing (eg. logging).
.Ed
.Sh BUGS
PPTP aliasing does not work when more than one internal client
connects to the same external server at the same time, because
PPTP requires a single TCP control connection to be established
between any two IP addresses.
.Sh AUTHORS
.An Charles Mott Aq cmott@scientech.com ,
versions 1.0 - 1.8, 2.0 - 2.4.
@ -816,7 +835,9 @@ versions 1.8b, 1.9 and 2.5.
Added IRC DCC support as well as contributing a number of architectural
improvements; added the firewall bypass for FTP/IRC DCC.
.An Erik Salander Aq erik@whistle.com
added support for PPTP.
added support for PPTP and RTSP.
.An Junichi Satoh Aq junichi@junichi.org
added support for RTSP/PNA.
.Sh ACKNOWLEDGMENTS
Listed below, in approximate chronological order, are individuals who
have provided valuable comments and/or debugging assistance.

4
sys/netinet/libalias/HISTORY
View File

@ -139,3 +139,7 @@ Version 3.1: May, 2000 (Erik Salander, erik@whistle.com)
- Added support to alias 227 replies, allows aliasing for
FTP servers in passive mode.
- Added support for PPTP aliasing.
Version 3.2: July, 2000 (Erik Salander, erik@whistle.com and
Junichi Satoh, junichi@junichi.org)
- Added support for streaming media (RTSP and PNA) aliasing.

3
sys/netinet/libalias/Makefile
View File

@ -5,7 +5,8 @@ SHLIB_MAJOR= 4
SHLIB_MINOR= 0
CFLAGS+= -Wall -I${.CURDIR}
SRCS= alias.c alias_cuseeme.c alias_db.c alias_ftp.c alias_irc.c \
alias_nbt.c alias_pptp.c alias_proxy.c alias_util.c
alias_nbt.c alias_pptp.c alias_proxy.c alias_smedia.c \
alias_util.c
INCS= alias.h
MAN3= libalias.3

135
sys/netinet/libalias/alias.c
View File

@ -76,9 +76,13 @@
Version 2.3 Dec 1998 (dillon)
- Major bounds checking additions, see FreeBSD/CVS
Version 3.1 May, 2000 (eds)
Version 3.1 May, 2000 (salander)
- Added hooks to handle PPTP.
Version 3.2 July, 2000 (salander and satoh)
- Added PacketUnaliasOut routine.
- Added hooks to handle RTSP/RTP.
See HISTORY file for additional revisions.
$FreeBSD$
@ -102,6 +106,8 @@
#define IRC_CONTROL_PORT_NUMBER_1 6667
#define IRC_CONTROL_PORT_NUMBER_2 6668
#define CUSEEME_PORT_NUMBER 7648
#define RTSP_CONTROL_PORT_NUMBER_1 554
#define RTSP_CONTROL_PORT_NUMBER_2 7070
#define PPTP_CONTROL_PORT_NUMBER 1723
@ -1112,6 +1118,11 @@ TcpAliasOut(struct ip *pip, int maxpacketsize)
else if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
AliasHandleIrcOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_1
|| ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_2)
AliasHandleRtspOut(pip, link, maxpacketsize);
else if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
|| ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
AliasHandlePptpOut(pip, link);
@ -1236,6 +1247,7 @@ FragmentOut(struct ip *pip)
PacketAliasFragmentIn()
PacketAliasIn()
PacketAliasOut()
PacketUnaliasOut()
(prototypes in alias.h)
*/
@ -1465,3 +1477,124 @@ PacketAliasOut(char *ptr, /* valid IP packet */
SetDefaultAliasAddress(addr_save);
return(iresult);
}
int
PacketUnaliasOut(char *ptr, /* valid IP packet */
int maxpacketsize /* for error checking */
)
{
struct ip *pip;
struct icmp *ic;
struct udphdr *ud;
struct tcphdr *tc;
struct alias_link *link;
int iresult = PKT_ALIAS_IGNORED;
pip = (struct ip *) ptr;
/* Defense against mangled packets */
if (ntohs(pip->ip_len) > maxpacketsize
|| (pip->ip_hl<<2) > maxpacketsize)
return(iresult);
ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
tc = (struct tcphdr *) ud;
ic = (struct icmp *) ud;
/* Find a link */
if (pip->ip_p == IPPROTO_UDP)
link = QueryUdpTcpIn(pip->ip_dst, pip->ip_src,
ud->uh_dport, ud->uh_sport,
IPPROTO_UDP);
else if (pip->ip_p == IPPROTO_TCP)
link = QueryUdpTcpIn(pip->ip_dst, pip->ip_src,
tc->th_dport, tc->th_sport,
IPPROTO_TCP);
else if (pip->ip_p == IPPROTO_ICMP)
link = FindIcmpIn(pip->ip_dst, pip->ip_src, ic->icmp_id);
else
link = NULL;
/* Change it from an aliased packet to an unaliased packet */
if (link != NULL)
{
if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP)
{
u_short *sptr;
int accumulate;
struct in_addr original_address;
u_short original_port;
original_address = GetOriginalAddress(link);
original_port = GetOriginalPort(link);
/* Adjust TCP/UDP checksum */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
if (pip->ip_p == IPPROTO_UDP) {
accumulate += ud->uh_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, ud->uh_sum)
} else {
accumulate += tc->th_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, tc->th_sum)
}
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &original_address,
(u_short *) &pip->ip_src,
2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
if (pip->ip_p == IPPROTO_UDP)
ud->uh_sport = original_port;
else
tc->th_sport = original_port;
iresult = PKT_ALIAS_OK;
} else if (pip->ip_p == IPPROTO_ICMP) {
u_short *sptr;
int accumulate;
struct in_addr original_address;
u_short original_id;
original_address = GetOriginalAddress(link);
original_id = GetOriginalPort(link);
/* Adjust ICMP checksum */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
accumulate += ic->icmp_id;
accumulate -= original_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum)
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &original_address,
(u_short *) &pip->ip_src,
2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
ic->icmp_id = original_id;
iresult = PKT_ALIAS_OK;
}
}
return(iresult);
}

3
sys/netinet/libalias/alias.h
View File

@ -44,6 +44,9 @@ struct alias_link;
extern int
PacketAliasOut(char *, int maxpacketsize);
extern int
PacketUnaliasOut(char *, int maxpacketsize);
/* Port and Address Redirection */
extern struct alias_link *
PacketAliasRedirectPort(struct in_addr, u_short,

213
sys/netinet/libalias/alias_db.c
View File

@ -103,6 +103,16 @@
version of PacketAliasPermanentLink(). The second function
implements static network address translation.
Version 3.2: July, 2000 (salander and satoh)
Added FindNewPortGroup to get contiguous range of port values.
Added QueryUdpTcpIn and QueryUdpTcpOut to look for an aliasing
link but not actually add one.
Added FindRtspOut, which is closely derived from FindUdpTcpOut,
except that the alias port (from FindNewPortGroup) is provided
as input.
See HISTORY file for additional revisions.
$FreeBSD$
@ -500,6 +510,9 @@ Link creation and deletion:
Link search:
FindLinkOut() - find link for outgoing packets
FindLinkIn() - find link for incoming packets
Port search:
FindNewPortGroup() - find an available group of ports
*/
/* Local prototypes */
@ -531,11 +544,14 @@ FindLinkIn(struct in_addr, struct in_addr, u_short, u_short, int, int);
#define ALIAS_PORT_BASE 0x08000
#define ALIAS_PORT_MASK 0x07fff
#define ALIAS_PORT_MASK_EVEN 0x07ffe
#define GET_NEW_PORT_MAX_ATTEMPTS 20
#define GET_ALIAS_PORT -1
#define GET_ALIAS_ID GET_ALIAS_PORT
#define FIND_EVEN_ALIAS_BASE 1
/* GetNewPort() allocates port numbers. Note that if a port number
is already in use, that does not mean that it cannot be used by
another link concurrently. This is because GetNewPort() looks for
@ -704,6 +720,102 @@ GetSocket(u_short port_net, int *sockfd, int link_type)
}
/* FindNewPortGroup() returns a base port number for an available
range of contiguous port numbers. Note that if a port number
is already in use, that does not mean that it cannot be used by
another link concurrently. This is because FindNewPortGroup()
looks for unused triplets: (dest addr, dest port, alias port). */
int
FindNewPortGroup(struct in_addr dst_addr,
struct in_addr alias_addr,
u_short src_port,
u_short dst_port,
u_short port_count,
u_char proto,
u_char align)
{
int i, j;
int max_trials;
u_short port_sys;
int link_type;
/*
* Get link_type from protocol
*/
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return (0);
break;
}
/*
* The aliasing port is automatically selected
* by one of two methods below:
*/
max_trials = GET_NEW_PORT_MAX_ATTEMPTS;
if (packetAliasMode & PKT_ALIAS_SAME_PORTS) {
/*
* When the ALIAS_SAME_PORTS option is
* chosen, the first try will be the
* actual source port. If this is already
* in use, the remainder of the trials
* will be random.
*/
port_sys = ntohs(src_port);
} else {
/* First trial and all subsequent are random. */
if (align == FIND_EVEN_ALIAS_BASE)
port_sys = random() & ALIAS_PORT_MASK_EVEN;
else
port_sys = random() & ALIAS_PORT_MASK;
port_sys += ALIAS_PORT_BASE;
}
/* Port number search */
for (i = 0; i < max_trials; i++) {
struct alias_link *search_result;
for (j = 0; j < port_count; j++)
if (0 != (search_result = FindLinkIn(dst_addr, alias_addr,
dst_port, htons(port_sys + j),
link_type, 0)))
break;
/* Found a good range, return base */
if (j == port_count)
return (htons(port_sys));
/* Find a new base to try */
if (align == FIND_EVEN_ALIAS_BASE)
port_sys = random() & ALIAS_PORT_MASK_EVEN;
else
port_sys = random() & ALIAS_PORT_MASK;
port_sys += ALIAS_PORT_BASE;
}
#ifdef DEBUG
fprintf(stderr, "PacketAlias/FindNewPortGroup(): ");
fprintf(stderr, "could not find free port(s)\n");
#endif
return(0);
}
static void
CleanupAliasData(void)
{
@ -1600,6 +1712,107 @@ FindPptpOut(struct in_addr src_addr,
}
struct alias_link *
QueryUdpTcpIn(struct in_addr dst_addr,
struct in_addr alias_addr,
u_short dst_port,
u_short alias_port,
u_char proto)
{
int link_type;
struct alias_link *link;
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return NULL;
break;
}
link = FindLinkIn(dst_addr, alias_addr,
dst_port, alias_port,
link_type, 0);
return(link);
}
struct alias_link *
QueryUdpTcpOut(struct in_addr src_addr,
struct in_addr dst_addr,
u_short src_port,
u_short dst_port,
u_char proto)
{
int link_type;
struct alias_link *link;
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return NULL;
break;
}
link = FindLinkOut(src_addr, dst_addr,
src_port, dst_port,
link_type, 0);
return(link);
}
struct alias_link *
FindRtspOut(struct in_addr src_addr,
struct in_addr dst_addr,
u_short src_port,
u_short alias_port,
u_char proto)
{
int link_type;
struct alias_link *link;
switch (proto)
{
case IPPROTO_UDP:
link_type = LINK_UDP;
break;
case IPPROTO_TCP:
link_type = LINK_TCP;
break;
default:
return NULL;
break;
}
link = FindLinkOut(src_addr, dst_addr, src_port, 0, link_type, 1);
if (link == NULL)
{
struct in_addr alias_addr;
alias_addr = FindAliasAddress(src_addr);
link = AddLink(src_addr, dst_addr, alias_addr,
src_port, 0, alias_port,
link_type);
}
return(link);
}
struct in_addr
FindOriginalAddress(struct in_addr alias_addr)
{

14
sys/netinet/libalias/alias_local.h
View File

@ -113,6 +113,15 @@ FindPptpIn(struct in_addr, struct in_addr, u_short);
struct alias_link *
FindPptpOut(struct in_addr, struct in_addr, u_short);
struct alias_link *
QueryUdpTcpIn (struct in_addr, struct in_addr, u_short, u_short, u_char);
struct alias_link *
QueryUdpTcpOut(struct in_addr, struct in_addr, u_short, u_short, u_char);
struct alias_link *
FindRtspOut(struct in_addr, struct in_addr, u_short, u_short, u_char);
struct in_addr
FindOriginalAddress(struct in_addr);
@ -120,6 +129,8 @@ struct in_addr
FindAliasAddress(struct in_addr);
/* External data access/modification */
int FindNewPortGroup(struct in_addr, struct in_addr,
u_short, u_short, u_short, u_char, u_char);
void GetFragmentAddr(struct alias_link *, struct in_addr *);
void SetFragmentAddr(struct alias_link *, struct in_addr);
void GetFragmentPtr(struct alias_link *, char **);
@ -165,6 +176,9 @@ void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
/* IRC routines */
void AliasHandleIrcOut(struct ip *, struct alias_link *, int);
/* RTSP routines */
void AliasHandleRtspOut(struct ip *, struct alias_link *, int);
/* PPTP routines */
int PptpGetCallID(struct ip *, u_short *);
void PptpSetCallID(struct ip *, u_short);

427
sys/netinet/libalias/alias_smedia.c Normal file
View File

@ -0,0 +1,427 @@
/*
* alias_smedia.c
*
* Copyright (c) 2000 Whistle Communications, Inc.
* All rights reserved.
*
* Subject to the following obligations and disclaimer of warranty, use and
* redistribution of this software, in source or object code forms, with or
* without modifications are expressly permitted by Whistle Communications;
* provided, however, that:
* 1. Any and all reproductions of the source or object code must include the
* copyright notice above and the following disclaimer of warranties; and
* 2. No rights are granted, in any manner or form, to use Whistle
* Communications, Inc. trademarks, including the mark "WHISTLE
* COMMUNICATIONS" on advertising, endorsements, or otherwise except as
* such appears in the above copyright notice or in the software.
*
* THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
* TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
* REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
* INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
* WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
* REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
* SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
* IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
* RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
* WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
* PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* Copyright (c) 2000 Junichi SATOH <junichi@astec.co.jp>
* <junichi@junichi.org>
* 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.
*
* Authors: Erik Salander <erik@whistle.com>
* Junichi SATOH <junichi@astec.co.jp>
* <junichi@junichi.org>
*
* $FreeBSD$
*/
/*
Alias_smedia.c is meant to contain the aliasing code for streaming media
protocols. It performs special processing for RSTP sessions under TCP.
Specifically, when a SETUP request is sent by a client, or a 200 reply
is sent by a server, it is intercepted and modified. The address is
changed to the gateway machine and an aliasing port is used.
More specifically, the "client_port" configuration parameter is
parsed for SETUP requests. The "server_port" configuration parameter is
parsed for 200 replies eminating from a server. This is intended to handle
the unicast case.
RTSP also allows a redirection of a stream to another client by using the
"destination" configuration parameter. The destination config parm would
indicate a different IP address. This function is NOT supported by the
RTSP translation code below.
The RTSP multicast functions without any address translation intervention.
For this routine to work, the SETUP/200 must fit entirely
into a single TCP packet. This is typically the case, but exceptions
can easily be envisioned under the actual specifications.
Probably the most troubling aspect of the approach taken here is
that the new SETUP/200 will typically be a different length, and
this causes a certain amount of bookkeeping to keep track of the
changes of sequence and acknowledgment numbers, since the client
machine is totally unaware of the modification to the TCP stream.
Initial version: May, 2000 (eds)
*/
#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 <netinet/udp.h>
#include "alias_local.h"
#define RTSP_CONTROL_PORT_NUMBER_1 554
#define RTSP_CONTROL_PORT_NUMBER_2 7070
#define RTSP_PORT_GROUP 2
#define ISDIGIT(a) (((a) >= '0') && ((a) <= '9'))
int search_string(char *data, int dlen, char *search_str)
{
int i, j, k;
int search_str_len;
search_str_len = strlen(search_str);
for (i = 0; i < dlen - search_str_len; i++) {
for (j = i, k = 0; j < dlen - search_str_len; j++, k++) {
if (data[j] != search_str[k] &&
data[j] != search_str[k] - ('a' - 'A')) {
break;
}
if (k == search_str_len - 1) {
return j + 1;
}
}
}
return -1;
}
int alias_rtsp_out(struct ip *pip,
struct alias_link *link,
char *data,
char *port_str)
{
int hlen, tlen, dlen;
struct tcphdr *tc;
int i, j, pos, state, port_dlen, new_dlen, delta;
u_short p[2], new_len;
u_short sport, eport, base_port;
u_short salias = 0, ealias = 0, base_alias = 0;
char *transport_str = "transport:";
char newdata[2048], *port_data, *port_newdata, stemp[80];
int links_created = 0, pkt_updated = 0;
struct alias_link *rtsp_link = NULL;
struct in_addr null_addr;
/* 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;
/* Find keyword, "Transport: " */
pos = search_string(data, dlen, transport_str);
if (pos < 0) {
return -1;
}
port_data = data + pos;
port_dlen = dlen - pos;
memcpy(newdata, data, pos);
port_newdata = newdata + pos;
while (port_dlen > strlen(port_str)) {
/* Find keyword, appropriate port string */
pos = search_string(port_data, port_dlen, port_str);
if (pos < 0) {
break;
}
memcpy (port_newdata, port_data, pos + 1);
port_newdata += (pos + 1);
p[0] = p[1] = 0;
sport = eport = 0;
state = 0;
for (i = pos; i < port_dlen; i++) {
switch(state) {
case 0:
if (port_data[i] == '=') {
state++;
}
break;
case 1:
if (ISDIGIT(port_data[i])) {
p[0] = p[0] * 10 + port_data[i] - '0';
} else {
if (port_data[i] == ';') {
state = 3;
}
if (port_data[i] == '-') {
state++;
}
}
break;
case 2:
if (ISDIGIT(port_data[i])) {
p[1] = p[1] * 10 + port_data[i] - '0';
} else {
state++;
}
break;
case 3:
base_port = p[0];
sport = htons(p[0]);
eport = htons(p[1]);
if (!links_created) {
links_created = 1;
/* Find an even numbered port number base that
satisfies the contiguous number of ports we need */
null_addr.s_addr = 0;
if (0 == (salias = FindNewPortGroup(null_addr,
FindAliasAddress(pip->ip_src),
sport, 0,
RTSP_PORT_GROUP,
IPPROTO_UDP, 1))) {
#ifdef DEBUG
fprintf(stderr,
"PacketAlias/RTSP: Cannot find contiguous RTSP data ports\n");
#endif
} else {
base_alias = ntohs(salias);
for (j = 0; j < RTSP_PORT_GROUP; j++) {
/* Establish link to port found in RTSP packet */
rtsp_link = FindRtspOut(GetOriginalAddress(link), null_addr,
htons(base_port + j), htons(base_alias + j),
IPPROTO_UDP);
if (rtsp_link != NULL) {
#ifndef NO_FW_PUNCH
/* Punch hole in firewall */
PunchFWHole(rtsp_link);
#endif
} else {
#ifdef DEBUG
fprintf(stderr,
"PacketAlias/RTSP: Cannot allocate RTSP data ports\n");
#endif
break;
}
}
}
ealias = htons(base_alias + (RTSP_PORT_GROUP - 1));
}
if (salias && rtsp_link) {
pkt_updated = 1;
/* Copy into IP packet */
sprintf(stemp, "%d", ntohs(salias));
memcpy(port_newdata, stemp, strlen(stemp));
port_newdata += strlen(stemp);
if (eport != 0) {
*port_newdata = '-';
port_newdata++;
/* Copy into IP packet */
sprintf(stemp, "%d", ntohs(ealias));
memcpy(port_newdata, stemp, strlen(stemp));
port_newdata += strlen(stemp);
}
*port_newdata = ';';
port_newdata++;
}
state++;
break;
}
if (state > 3) {
break;
}
}
port_data += i;
port_dlen -= i;
}
if (!pkt_updated)
return -1;
memcpy (port_newdata, port_data, port_dlen);
port_newdata += port_dlen;
*port_newdata = '\0';
/* Create new packet */
new_dlen = port_newdata - newdata;
memcpy (data, newdata, new_dlen);
SetAckModified(link);
delta = GetDeltaSeqOut(pip, link);
AddSeq(pip, link, delta + new_dlen - dlen);
new_len = htons(hlen + new_dlen);
DifferentialChecksum(&pip->ip_sum,
&new_len,
&pip->ip_len,
1);
pip->ip_len = new_len;
tc->th_sum = 0;
tc->th_sum = TcpChecksum(pip);
return 0;
}
/* Support the protocol used by early versions of RealPlayer */
int alias_pna_out(struct ip *pip,
struct alias_link *link,
char *data,
int dlen)
{
struct alias_link *pna_links;
u_short msg_id, msg_len;
char *work;
u_short alias_port, port;
struct tcphdr *tc;
work = data;
work += 5;
while (work + 4 < data + dlen) {
memcpy(&msg_id, work, 2);
work += 2;
memcpy(&msg_len, work, 2);
work += 2;
if (ntohs(msg_id) == 0) {
/* end of options */
return 0;
}
if ((ntohs(msg_id) == 1) || (ntohs(msg_id) == 7)) {
memcpy((char*)&port, (char*)work, 2);
pna_links = FindUdpTcpOut(pip->ip_src, GetDestAddress(link),
port, 0, IPPROTO_UDP);
if (pna_links != NULL) {
#ifndef NO_FW_PUNCH
/* Punch hole in firewall */
PunchFWHole(pna_links);
#endif
tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
alias_port = GetAliasPort(pna_links);
memcpy((char*)work, (char*)&alias_port, 2);
/* Compute TCP checksum for revised packet */
tc->th_sum = 0;
tc->th_sum = TcpChecksum(pip);
}
}
work += ntohs(msg_len);
}
return 0;
}
void
AliasHandleRtspOut(struct ip *pip, struct alias_link *link, int maxpacketsize)
{
int hlen, tlen, dlen;
struct tcphdr *tc;
char *data, *setup = "SETUP", *pna = "PNA", *str200 = "200", *okstr = "OK";
char *client_port_str = "client_port", *server_port_str = "server_port";
int i, parseOk;
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;
data = (char*)pip;
data += hlen;
/* When aliasing a client, check for the SETUP request */
if ((ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1) ||
(ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2)) {
if (dlen >= strlen(setup)) {
if (memcmp(data, setup, strlen(setup)) == 0) {
alias_rtsp_out(pip, link, data, client_port_str);
return;
}
}
if (dlen >= strlen(pna)) {
if (memcmp(data, pna, strlen(pna)) == 0) {
alias_pna_out(pip, link, data, dlen);
}
}
} else {
/* When aliasing a server, check for the 200 reply
Accomodate varying number of blanks between 200 & OK */
if (dlen >= strlen(str200)) {
for (parseOk = 0, i = 0;
i <= dlen - strlen(str200);
i++) {
if (memcmp(&data[i], str200, strlen(str200)) == 0) {
parseOk = 1;
break;
}
}
if (parseOk) {
i += strlen(str200); /* skip string found */
while(data[i] == ' ') /* skip blank(s) */
i++;
if ((dlen - i) >= strlen(okstr)) {
if (memcmp(&data[i], okstr, strlen(okstr)) == 0)
alias_rtsp_out(pip, link, data, server_port_str);
}
}
}
}
}

23
sys/netinet/libalias/libalias.3
View File

@ -808,6 +808,25 @@ If the checksum is valid,
.Fn PacketAliasInternetChecksum
will return zero.
.Ed
.Pp
.Ft int
.Fn PacketUnaliasOut "char *buffer" "int maxpacketsize"
.Bd -ragged -offset indent
An outgoing packet, which has already been aliased, has its private address/port
information restored by this function.
The IP packet is pointed to by
.Fa buffer ,
and
.Fa maxpacketsize
is provided for error checking purposes.
This function can be used if an already-aliased packet needs to have its
original IP header restored for further processing (eg. logging).
.Ed
.Sh BUGS
PPTP aliasing does not work when more than one internal client
connects to the same external server at the same time, because
PPTP requires a single TCP control connection to be established
between any two IP addresses.
.Sh AUTHORS
.An Charles Mott Aq cmott@scientech.com ,
versions 1.0 - 1.8, 2.0 - 2.4.
@ -816,7 +835,9 @@ versions 1.8b, 1.9 and 2.5.
Added IRC DCC support as well as contributing a number of architectural
improvements; added the firewall bypass for FTP/IRC DCC.
.An Erik Salander Aq erik@whistle.com
added support for PPTP.
added support for PPTP and RTSP.
.An Junichi Satoh Aq junichi@junichi.org
added support for RTSP/PNA.
.Sh ACKNOWLEDGMENTS
Listed below, in approximate chronological order, are individuals who
have provided valuable comments and/or debugging assistance.