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/*
* Dropbear - a SSH2 server
*
* Copyright (c) 2002-2004 Matt Johnston
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
#include "includes.h"
#include "packet.h"
#include "session.h"
#include "dbutil.h"
#include "ssh.h"
#include "algo.h"
#include "buffer.h"
#include "kex.h"
#include "dbrandom.h"
#include "service.h"
#include "auth.h"
#include "channel.h"
#define MAX_UNAUTH_PACKET_TYPE SSH_MSG_USERAUTH_PK_OK
static void recv_unimplemented(void);
/* process a decrypted packet, call the appropriate handler */
void process_packet() {
unsigned char type;
unsigned int i;
unsigned int first_strict_kex = ses.kexstate.strict_kex && !ses.kexstate.donefirstkex;
time_t now;
TRACE2(("enter process_packet"))
type = buf_getbyte(ses.payload);
TRACE(("process_packet: packet type = %d, len %d", type, ses.payload->len))
now = monotonic_now();
ses.last_packet_time_keepalive_recv = now;
if (type == SSH_MSG_DISCONNECT) {
/* Allowed at any time */
dropbear_close("Disconnect received");
}
/* These packets may be received at any time,
except during first kex with strict kex */
if (!first_strict_kex) {
switch(type) {
case SSH_MSG_IGNORE:
goto out;
case SSH_MSG_DEBUG:
goto out;
case SSH_MSG_UNIMPLEMENTED:
TRACE(("SSH_MSG_UNIMPLEMENTED"))
goto out;
}
}
/* Ignore these packet types so that keepalives don't interfere with
idle detection. This is slightly incorrect since a tcp forwarded
global request with failure won't trigger the idle timeout,
but that's probably acceptable */
if (!(type == SSH_MSG_GLOBAL_REQUEST
|| type == SSH_MSG_REQUEST_FAILURE
|| type == SSH_MSG_CHANNEL_FAILURE)) {
ses.last_packet_time_idle = now;
}
/* This applies for KEX, where the spec says the next packet MUST be
* NEWKEYS */
if (ses.requirenext != 0) {
if (ses.requirenext == type)
{
/* Got what we expected */
TRACE(("got expected packet %d during kexinit", type))
}
else
{
/* RFC4253 7.1 - various messages are allowed at this point.
The only ones we know about have already been handled though,
so just return "unimplemented" */
if (type >= 1 && type <= 49
&& type != SSH_MSG_SERVICE_REQUEST
&& type != SSH_MSG_SERVICE_ACCEPT
&& type != SSH_MSG_KEXINIT
&& !first_strict_kex)
{
TRACE(("unknown allowed packet during kexinit"))
recv_unimplemented();
goto out;
}
else
{
TRACE(("disallowed packet during kexinit"))
dropbear_exit("Unexpected packet type %d, expected %d", type,
ses.requirenext);
}
}
}
/* Check if we should ignore this packet. Used currently only for
* KEX code, with first_kex_packet_follows */
if (ses.ignorenext) {
TRACE(("Ignoring packet, type = %d", type))
ses.ignorenext = 0;
goto out;
}
/* Only clear the flag after we have checked ignorenext */
if (ses.requirenext != 0 && ses.requirenext == type)
{
ses.requirenext = 0;
}
/* Kindly the protocol authors gave all the preauth packets type values
* less-than-or-equal-to 60 ( == MAX_UNAUTH_PACKET_TYPE ).
* NOTE: if the protocol changes and new types are added, revisit this
* assumption */
if ( !ses.authstate.authdone && type > MAX_UNAUTH_PACKET_TYPE ) {
dropbear_exit("Received message %d before userauth", type);
}
for (i = 0; ; i++) {
if (ses.packettypes[i].type == 0) {
/* end of list */
break;
}
if (ses.packettypes[i].type == type) {
ses.packettypes[i].handler();
goto out;
}
}
/* TODO do something more here? */
TRACE(("preauth unknown packet"))
recv_unimplemented();
out:
ses.lastpacket = type;
buf_free(ses.payload);
ses.payload = NULL;
TRACE2(("leave process_packet"))
}
/* This must be called directly after receiving the unimplemented packet.
* Isn't the most clean implementation, it relies on packet processing
* occurring directly after decryption (direct use of ses.recvseq).
* This is reasonably valid, since there is only a single decryption buffer */
static void recv_unimplemented() {
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_UNIMPLEMENTED);
/* the decryption routine increments the sequence number, we must
* decrement */
buf_putint(ses.writepayload, ses.recvseq - 1);
encrypt_packet();
}
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