Mercurial > dropbear
view cli-channel.c @ 1715:3974f087d9c0
Disallow leading lines before the ident for server (#102)
Per RFC4253 4.2 clients must be able to process other lines of data
before the version string, server behavior is not defined neither
with MUST/SHOULD nor with MAY.
If server process up to 50 lines too - it may cause too long hanging
session with invalid/evil client that consume host resources and
potentially may lead to DDoS on poor embedded boxes.
Let's require first line from client to be version string and fail
early if it's not - matches both RFC and real OpenSSH behavior.
author | Vladislav Grishenko <themiron@users.noreply.github.com> |
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date | Mon, 15 Jun 2020 18:22:18 +0500 |
parents | 1c7bf9cec6c8 |
children |
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/* * Dropbear SSH * * 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 "channel.h" #include "buffer.h" #include "circbuffer.h" #include "dbutil.h" #include "session.h" #include "ssh.h" /* We receive channel data - only used by the client chansession code*/ void recv_msg_channel_extended_data() { struct Channel *channel; unsigned int datatype; TRACE(("enter recv_msg_channel_extended_data")) channel = getchannel(); if (channel->type != &clichansess) { TRACE(("leave recv_msg_channel_extended_data: chantype is wrong")) return; /* we just ignore it */ } datatype = buf_getint(ses.payload); if (datatype != SSH_EXTENDED_DATA_STDERR) { TRACE(("leave recv_msg_channel_extended_data: wrong datatype: %d", datatype)) return; } common_recv_msg_channel_data(channel, channel->errfd, channel->extrabuf); TRACE(("leave recv_msg_channel_extended_data")) }