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/* match the first algorithm in the comma-separated list in buf which is
31 * also in localalgos[], or return NULL on failure.
32 * (*goodguess) is set to 1 if the preferred client/server algos match,
33 * 0 otherwise. This is used for checking if the kexalgo/hostkeyalgos are
34 * guessed correctly */
35algo_type * svr_buf_match_algo(buffer* buf, algo_type localalgos[],
36		int *goodguess)
37{
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	/* Debug this */
50	TRACE(("buf_match_algo: %s", algolist))
51	if (len > MAX_PROPOSED_ALGO*(MAX_NAME_LEN+1)) {
52		goto out; /* just a sanity check, no other use */
53	}
54
55	/* remotealgos will contain a list of the strings parsed out */
56	/* We will have at least one string (even if it's just "") */
57	remotealgos[0] = algolist;
58	count = 1;
59	/* Iterate through, replacing ','s with NULs, to split it into
60	 * words. */
61	for (i = 0; i < len; i++) {
62		if (algolist[i] == '\0') {
63			/* someone is trying something strange */
64			goto out;
65		}
66		if (algolist[i] == ',') {
67			algolist[i] = '\0';
68			remotealgos[count] = &algolist[i+1];
69			count++;
70		}
71		if (count == MAX_PROPOSED_ALGO) {
72			break;
73		}
74	}
75
76	/* iterate and find the first match */
77	for (i = 0; i < count; i++) {
78
79		len = strlen(remotealgos[i]);
80
81		for (j = 0; localalgos[j].name != NULL; j++) {
82			if (localalgos[j].usable) {
83				if (len == strlen(localalgos[j].name) &&
84						strncmp(localalgos[j].name, remotealgos[i], len) == 0) {
85					/* set if it was a good guess */
86					if (i == 0 && j == 0) {
87						*goodguess = 1;
88					}
89					/* set the algo to return */
90					ret = &localalgos[j];
91					goto out;
92				}
93			}
94		}
95	}
96
97out:
98	m_free(algolist);
99	return ret;
100}
101