Mercurial > dropbear

annotate svr-service.c @ 1715:3974f087d9c0

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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>
date Mon, 15 Jun 2020 18:22:18 +0500
parents f20038b513a5
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /*
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2 * Dropbear - a SSH2 server
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3 *
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4 * Copyright (c) 2002,2003 Matt Johnston
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5 * All rights reserved.
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6 *
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7 * Permission is hereby granted, free of charge, to any person obtaining a copy
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8 * of this software and associated documentation files (the "Software"), to deal
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9 * in the Software without restriction, including without limitation the rights
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10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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11 * copies of the Software, and to permit persons to whom the Software is
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12 * furnished to do so, subject to the following conditions:
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13 *
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14 * The above copyright notice and this permission notice shall be included in
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15 * all copies or substantial portions of the Software.
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16 *
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17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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23 * SOFTWARE. */
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24
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25 #include "includes.h"
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26 #include "dbutil.h"
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27 #include "service.h"
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28 #include "session.h"
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29 #include "packet.h"
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30 #include "ssh.h"
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31 #include "auth.h"
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32
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33 static void send_msg_service_accept(const char *name, int len);
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35 /* processes a SSH_MSG_SERVICE_REQUEST, returning 0 if finished,
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36 * 1 if not */
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37 void recv_msg_service_request() {
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38
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39 char * name;
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40 unsigned int len;
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41
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42 TRACE(("enter recv_msg_service_request"))
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44 name = buf_getstring(ses.payload, &len);
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45
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46 /* ssh-userauth */
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47 if (len == SSH_SERVICE_USERAUTH_LEN &&
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48 strncmp(SSH_SERVICE_USERAUTH, name, len) == 0) {
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50 send_msg_service_accept(name, len);
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51 m_free(name);
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52 TRACE(("leave recv_msg_service_request: done ssh-userauth"))
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53 return;
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54 }
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56 /* ssh-connection */
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57 if (len == SSH_SERVICE_CONNECTION_LEN &&
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58 (strncmp(SSH_SERVICE_CONNECTION, name, len) == 0)) {
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59 if (ses.authstate.authdone != 1) {
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60 dropbear_exit("Request for connection before auth");
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61 }
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63 send_msg_service_accept(name, len);
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64 m_free(name);
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65 TRACE(("leave recv_msg_service_request: done ssh-connection"))
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66 return;
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67 }
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69 m_free(name);
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70 /* TODO this should be a MSG_DISCONNECT */
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71 dropbear_exit("Unrecognised SSH_MSG_SERVICE_REQUEST");
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74 }
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76 static void send_msg_service_accept(const char *name, int len) {
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78 TRACE(("accepting service %s", name))
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80 CHECKCLEARTOWRITE();
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82 buf_putbyte(ses.writepayload, SSH_MSG_SERVICE_ACCEPT);
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83 buf_putstring(ses.writepayload, name, len);
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85 encrypt_packet();
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86
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87 }