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 */
36algo_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
95out:
96	m_free(algolist);
97	return ret;
98}
99
100