release/src/router/dropbear/cli-algo.c

   1 /*
   2  * Dropbear - a SSH2 server
   3  * SSH client implementation
   4  *
   5  * Copyright (c) 2002,2003 Matt Johnston
   6  * Copyright (c) 2004 by Mihnea Stoenescu
   7  * All rights reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a copy
  10  * of this software and associated documentation files (the "Software"), to deal
  11  * in the Software without restriction, including without limitation the rights
  12  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13  * copies of the Software, and to permit persons to whom the Software is
  14  * furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included in
  17  * all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  25  * SOFTWARE. */
  26
  27 #include "algo.h"
  28 #include "dbutil.h"
  29
  30
  31 /*
  32  * The chosen [encryption | MAC | compression] algorithm to each
  33  * direction MUST be the first algorithm  on the client's list
  34  * that is also on the server's list.
  35  */
  36 algo_type * cli_buf_match_algo(buffer* buf, algo_type localalgos[],
  37                 int *goodguess) {
  38
  39         unsigned char * algolist = NULL;
  40         unsigned char * remotealgos[MAX_PROPOSED_ALGO];
  41         unsigned int len;
  42         unsigned int count, i, j;
  43         algo_type * ret = NULL;
  44
  45         *goodguess = 0;
  46
  47         /* get the comma-separated list from the buffer ie "algo1,algo2,algo3" */
  48         algolist = buf_getstring(buf, &len);
  49         TRACE(("cli_buf_match_algo: %s", algolist))
  50         if (len > MAX_PROPOSED_ALGO*(MAX_NAME_LEN+1)) {
  51                 goto out; /* just a sanity check, no other use */
  52         }
  53
  54         /* remotealgos will contain a list of the strings parsed out */
  55         /* We will have at least one string (even if it's just "") */
  56         remotealgos[0] = algolist;
  57         count = 1;
  58         /* Iterate through, replacing ','s with NULs, to split it into
  59          * words. */
  60         for (i = 0; i < len; i++) {
  61                 if (algolist[i] == '\0') {
  62                         /* someone is trying something strange */
  63                         goto out;
  64                 }
  65                 if (algolist[i] == ',') {
  66                         algolist[i] = '\0';
  67                         remotealgos[count] = &algolist[i+1];
  68                         count++;
  69                 }
  70                 if (count >= MAX_PROPOSED_ALGO) {
  71                         break;
  72                 }
  73         }
  74
  75         /* iterate and find the first match */
  76
  77         for (j = 0; localalgos[j].name != NULL; j++) {
  78                 if (localalgos[j].usable) {
  79                 len = strlen(localalgos[j].name);
  80                         for (i = 0; i < count; i++) {
  81                                 if (len == strlen(remotealgos[i])
  82                                                 && strncmp(localalgos[j].name,
  83                                                         remotealgos[i], len) == 0) {
  84                                         if (i == 0 && j == 0) {
  85                                                 /* was a good guess */
  86                                                 *goodguess = 1;
  87                                         }
  88                                         ret = &localalgos[j];
  89                                         goto out;
  90                                 }
  91                         }
  92                 }
  93         }
  94
  95 out:
  96         m_free(algolist);
  97         return ret;
  98 }
  99