1/* $OpenBSD: kex-names.c,v 1.1 2024/05/17 00:32:32 djm Exp $ */
2/*
3 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26
27#include <stdio.h>
28#include <stdlib.h>
29#include <string.h>
30#include <unistd.h>
31#include <signal.h>
32
33#ifdef WITH_OPENSSL
34#include <openssl/crypto.h>
35#include <openssl/evp.h>
36#endif
37
38#include "kex.h"
39#include "log.h"
40#include "match.h"
41#include "digest.h"
42#include "misc.h"
43
44#include "ssherr.h"
45#include "xmalloc.h"
46
47struct kexalg {
48	char *name;
49	u_int type;
50	int ec_nid;
51	int hash_alg;
52};
53static const struct kexalg kexalgs[] = {
54#ifdef WITH_OPENSSL
55	{ KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
56	{ KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
57	{ KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
58	{ KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
59	{ KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
60	{ KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
61	{ KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
62	{ KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
63	    NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
64	{ KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
65	    SSH_DIGEST_SHA384 },
66	{ KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
67	    SSH_DIGEST_SHA512 },
68#endif
69	{ KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
70	{ KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
71	{ KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
72	    SSH_DIGEST_SHA512 },
73	{ NULL, 0, -1, -1},
74};
75
76char *
77kex_alg_list(char sep)
78{
79	char *ret = NULL, *tmp;
80	size_t nlen, rlen = 0;
81	const struct kexalg *k;
82
83	for (k = kexalgs; k->name != NULL; k++) {
84		if (ret != NULL)
85			ret[rlen++] = sep;
86		nlen = strlen(k->name);
87		if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
88			free(ret);
89			return NULL;
90		}
91		ret = tmp;
92		memcpy(ret + rlen, k->name, nlen + 1);
93		rlen += nlen;
94	}
95	return ret;
96}
97
98static const struct kexalg *
99kex_alg_by_name(const char *name)
100{
101	const struct kexalg *k;
102
103	for (k = kexalgs; k->name != NULL; k++) {
104		if (strcmp(k->name, name) == 0)
105			return k;
106	}
107	return NULL;
108}
109
110int
111kex_name_valid(const char *name)
112{
113	return kex_alg_by_name(name) != NULL;
114}
115
116u_int
117kex_type_from_name(const char *name)
118{
119	const struct kexalg *k;
120
121	if ((k = kex_alg_by_name(name)) == NULL)
122		return 0;
123	return k->type;
124}
125
126int
127kex_hash_from_name(const char *name)
128{
129	const struct kexalg *k;
130
131	if ((k = kex_alg_by_name(name)) == NULL)
132		return -1;
133	return k->hash_alg;
134}
135
136int
137kex_nid_from_name(const char *name)
138{
139	const struct kexalg *k;
140
141	if ((k = kex_alg_by_name(name)) == NULL)
142		return -1;
143	return k->ec_nid;
144}
145
146/* Validate KEX method name list */
147int
148kex_names_valid(const char *names)
149{
150	char *s, *cp, *p;
151
152	if (names == NULL || strcmp(names, "") == 0)
153		return 0;
154	if ((s = cp = strdup(names)) == NULL)
155		return 0;
156	for ((p = strsep(&cp, ",")); p && *p != '\0';
157	    (p = strsep(&cp, ","))) {
158		if (kex_alg_by_name(p) == NULL) {
159			error("Unsupported KEX algorithm \"%.100s\"", p);
160			free(s);
161			return 0;
162		}
163	}
164	debug3("kex names ok: [%s]", names);
165	free(s);
166	return 1;
167}
168
169/* returns non-zero if proposal contains any algorithm from algs */
170int
171kex_has_any_alg(const char *proposal, const char *algs)
172{
173	char *cp;
174
175	if ((cp = match_list(proposal, algs, NULL)) == NULL)
176		return 0;
177	free(cp);
178	return 1;
179}
180
181/*
182 * Concatenate algorithm names, avoiding duplicates in the process.
183 * Caller must free returned string.
184 */
185char *
186kex_names_cat(const char *a, const char *b)
187{
188	char *ret = NULL, *tmp = NULL, *cp, *p;
189	size_t len;
190
191	if (a == NULL || *a == '\0')
192		return strdup(b);
193	if (b == NULL || *b == '\0')
194		return strdup(a);
195	if (strlen(b) > 1024*1024)
196		return NULL;
197	len = strlen(a) + strlen(b) + 2;
198	if ((tmp = cp = strdup(b)) == NULL ||
199	    (ret = calloc(1, len)) == NULL) {
200		free(tmp);
201		return NULL;
202	}
203	strlcpy(ret, a, len);
204	for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
205		if (kex_has_any_alg(ret, p))
206			continue; /* Algorithm already present */
207		if (strlcat(ret, ",", len) >= len ||
208		    strlcat(ret, p, len) >= len) {
209			free(tmp);
210			free(ret);
211			return NULL; /* Shouldn't happen */
212		}
213	}
214	free(tmp);
215	return ret;
216}
217
218/*
219 * Assemble a list of algorithms from a default list and a string from a
220 * configuration file. The user-provided string may begin with '+' to
221 * indicate that it should be appended to the default, '-' that the
222 * specified names should be removed, or '^' that they should be placed
223 * at the head.
224 */
225int
226kex_assemble_names(char **listp, const char *def, const char *all)
227{
228	char *cp, *tmp, *patterns;
229	char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
230	int r = SSH_ERR_INTERNAL_ERROR;
231
232	if (listp == NULL || def == NULL || all == NULL)
233		return SSH_ERR_INVALID_ARGUMENT;
234
235	if (*listp == NULL || **listp == '\0') {
236		if ((*listp = strdup(def)) == NULL)
237			return SSH_ERR_ALLOC_FAIL;
238		return 0;
239	}
240
241	list = *listp;
242	*listp = NULL;
243	if (*list == '+') {
244		/* Append names to default list */
245		if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
246			r = SSH_ERR_ALLOC_FAIL;
247			goto fail;
248		}
249		free(list);
250		list = tmp;
251	} else if (*list == '-') {
252		/* Remove names from default list */
253		if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {
254			r = SSH_ERR_ALLOC_FAIL;
255			goto fail;
256		}
257		free(list);
258		/* filtering has already been done */
259		return 0;
260	} else if (*list == '^') {
261		/* Place names at head of default list */
262		if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
263			r = SSH_ERR_ALLOC_FAIL;
264			goto fail;
265		}
266		free(list);
267		list = tmp;
268	} else {
269		/* Explicit list, overrides default - just use "list" as is */
270	}
271
272	/*
273	 * The supplied names may be a pattern-list. For the -list case,
274	 * the patterns are applied above. For the +list and explicit list
275	 * cases we need to do it now.
276	 */
277	ret = NULL;
278	if ((patterns = opatterns = strdup(list)) == NULL) {
279		r = SSH_ERR_ALLOC_FAIL;
280		goto fail;
281	}
282	/* Apply positive (i.e. non-negated) patterns from the list */
283	while ((cp = strsep(&patterns, ",")) != NULL) {
284		if (*cp == '!') {
285			/* negated matches are not supported here */
286			r = SSH_ERR_INVALID_ARGUMENT;
287			goto fail;
288		}
289		free(matching);
290		if ((matching = match_filter_allowlist(all, cp)) == NULL) {
291			r = SSH_ERR_ALLOC_FAIL;
292			goto fail;
293		}
294		if ((tmp = kex_names_cat(ret, matching)) == NULL) {
295			r = SSH_ERR_ALLOC_FAIL;
296			goto fail;
297		}
298		free(ret);
299		ret = tmp;
300	}
301	if (ret == NULL || *ret == '\0') {
302		/* An empty name-list is an error */
303		/* XXX better error code? */
304		r = SSH_ERR_INVALID_ARGUMENT;
305		goto fail;
306	}
307
308	/* success */
309	*listp = ret;
310	ret = NULL;
311	r = 0;
312
313 fail:
314	free(matching);
315	free(opatterns);
316	free(list);
317	free(ret);
318	return r;
319}
320