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      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 
    100