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 #include "includes.h"
27
28 #include <stdio.h>
29 #include <stdlib.h>
30 #include <string.h>
31 #include <unistd.h>
32 #include <signal.h>
33
34 #ifdef WITH_OPENSSL
35 #include <openssl/crypto.h>
36 #include <openssl/evp.h>
37 #endif
38
39 #include "kex.h"
40 #include "log.h"
41 #include "match.h"
42 #include "digest.h"
43 #include "misc.h"
44
45 #include "ssherr.h"
46 #include "xmalloc.h"
47
48 struct kexalg {
49 char *name;
50 u_int type;
51 int ec_nid;
52 int hash_alg;
53 };
54 static const struct kexalg kexalgs[] = {
55 #ifdef WITH_OPENSSL
56 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
57 { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
58 { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
59 { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
60 { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },
61 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
62 #ifdef HAVE_EVP_SHA256
63 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },
64 #endif /* HAVE_EVP_SHA256 */
65 #ifdef OPENSSL_HAS_ECC
66 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
67 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
68 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
69 SSH_DIGEST_SHA384 },
70 # ifdef OPENSSL_HAS_NISTP521
71 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
72 SSH_DIGEST_SHA512 },
73 # endif /* OPENSSL_HAS_NISTP521 */
74 #endif /* OPENSSL_HAS_ECC */
75 #endif /* WITH_OPENSSL */
76 #if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)
77 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
78 { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
79 #ifdef USE_SNTRUP761X25519
80 { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
81 SSH_DIGEST_SHA512 },
82 #endif
83 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
84 { NULL, 0, -1, -1},
85 };
86
87 char *
kex_alg_list(char sep)88 kex_alg_list(char sep)
89 {
90 char *ret = NULL, *tmp;
91 size_t nlen, rlen = 0;
92 const struct kexalg *k;
93
94 for (k = kexalgs; k->name != NULL; k++) {
95 if (ret != NULL)
96 ret[rlen++] = sep;
97 nlen = strlen(k->name);
98 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
99 free(ret);
100 return NULL;
101 }
102 ret = tmp;
103 memcpy(ret + rlen, k->name, nlen + 1);
104 rlen += nlen;
105 }
106 return ret;
107 }
108
109 static const struct kexalg *
kex_alg_by_name(const char * name)110 kex_alg_by_name(const char *name)
111 {
112 const struct kexalg *k;
113
114 for (k = kexalgs; k->name != NULL; k++) {
115 if (strcmp(k->name, name) == 0)
116 return k;
117 }
118 return NULL;
119 }
120
121 int
kex_name_valid(const char * name)122 kex_name_valid(const char *name)
123 {
124 return kex_alg_by_name(name) != NULL;
125 }
126
127 u_int
kex_type_from_name(const char * name)128 kex_type_from_name(const char *name)
129 {
130 const struct kexalg *k;
131
132 if ((k = kex_alg_by_name(name)) == NULL)
133 return 0;
134 return k->type;
135 }
136
137 int
kex_hash_from_name(const char * name)138 kex_hash_from_name(const char *name)
139 {
140 const struct kexalg *k;
141
142 if ((k = kex_alg_by_name(name)) == NULL)
143 return -1;
144 return k->hash_alg;
145 }
146
147 int
kex_nid_from_name(const char * name)148 kex_nid_from_name(const char *name)
149 {
150 const struct kexalg *k;
151
152 if ((k = kex_alg_by_name(name)) == NULL)
153 return -1;
154 return k->ec_nid;
155 }
156
157 /* Validate KEX method name list */
158 int
kex_names_valid(const char * names)159 kex_names_valid(const char *names)
160 {
161 char *s, *cp, *p;
162
163 if (names == NULL || strcmp(names, "") == 0)
164 return 0;
165 if ((s = cp = strdup(names)) == NULL)
166 return 0;
167 for ((p = strsep(&cp, ",")); p && *p != '\0';
168 (p = strsep(&cp, ","))) {
169 if (kex_alg_by_name(p) == NULL) {
170 error("Unsupported KEX algorithm \"%.100s\"", p);
171 free(s);
172 return 0;
173 }
174 }
175 debug3("kex names ok: [%s]", names);
176 free(s);
177 return 1;
178 }
179
180 /* returns non-zero if proposal contains any algorithm from algs */
181 int
kex_has_any_alg(const char * proposal,const char * algs)182 kex_has_any_alg(const char *proposal, const char *algs)
183 {
184 char *cp;
185
186 if ((cp = match_list(proposal, algs, NULL)) == NULL)
187 return 0;
188 free(cp);
189 return 1;
190 }
191
192 /*
193 * Concatenate algorithm names, avoiding duplicates in the process.
194 * Caller must free returned string.
195 */
196 char *
kex_names_cat(const char * a,const char * b)197 kex_names_cat(const char *a, const char *b)
198 {
199 char *ret = NULL, *tmp = NULL, *cp, *p;
200 size_t len;
201
202 if (a == NULL || *a == '\0')
203 return strdup(b);
204 if (b == NULL || *b == '\0')
205 return strdup(a);
206 if (strlen(b) > 1024*1024)
207 return NULL;
208 len = strlen(a) + strlen(b) + 2;
209 if ((tmp = cp = strdup(b)) == NULL ||
210 (ret = calloc(1, len)) == NULL) {
211 free(tmp);
212 return NULL;
213 }
214 strlcpy(ret, a, len);
215 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
216 if (kex_has_any_alg(ret, p))
217 continue; /* Algorithm already present */
218 if (strlcat(ret, ",", len) >= len ||
219 strlcat(ret, p, len) >= len) {
220 free(tmp);
221 free(ret);
222 return NULL; /* Shouldn't happen */
223 }
224 }
225 free(tmp);
226 return ret;
227 }
228
229 /*
230 * Assemble a list of algorithms from a default list and a string from a
231 * configuration file. The user-provided string may begin with '+' to
232 * indicate that it should be appended to the default, '-' that the
233 * specified names should be removed, or '^' that they should be placed
234 * at the head.
235 */
236 int
kex_assemble_names(char ** listp,const char * def,const char * all)237 kex_assemble_names(char **listp, const char *def, const char *all)
238 {
239 char *cp, *tmp, *patterns;
240 char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
241 int r = SSH_ERR_INTERNAL_ERROR;
242
243 if (listp == NULL || def == NULL || all == NULL)
244 return SSH_ERR_INVALID_ARGUMENT;
245
246 if (*listp == NULL || **listp == '\0') {
247 if ((*listp = strdup(def)) == NULL)
248 return SSH_ERR_ALLOC_FAIL;
249 return 0;
250 }
251
252 list = *listp;
253 *listp = NULL;
254 if (*list == '+') {
255 /* Append names to default list */
256 if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
257 r = SSH_ERR_ALLOC_FAIL;
258 goto fail;
259 }
260 free(list);
261 list = tmp;
262 } else if (*list == '-') {
263 /* Remove names from default list */
264 if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {
265 r = SSH_ERR_ALLOC_FAIL;
266 goto fail;
267 }
268 free(list);
269 /* filtering has already been done */
270 return 0;
271 } else if (*list == '^') {
272 /* Place names at head of default list */
273 if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
274 r = SSH_ERR_ALLOC_FAIL;
275 goto fail;
276 }
277 free(list);
278 list = tmp;
279 } else {
280 /* Explicit list, overrides default - just use "list" as is */
281 }
282
283 /*
284 * The supplied names may be a pattern-list. For the -list case,
285 * the patterns are applied above. For the +list and explicit list
286 * cases we need to do it now.
287 */
288 ret = NULL;
289 if ((patterns = opatterns = strdup(list)) == NULL) {
290 r = SSH_ERR_ALLOC_FAIL;
291 goto fail;
292 }
293 /* Apply positive (i.e. non-negated) patterns from the list */
294 while ((cp = strsep(&patterns, ",")) != NULL) {
295 if (*cp == '!') {
296 /* negated matches are not supported here */
297 r = SSH_ERR_INVALID_ARGUMENT;
298 goto fail;
299 }
300 free(matching);
301 if ((matching = match_filter_allowlist(all, cp)) == NULL) {
302 r = SSH_ERR_ALLOC_FAIL;
303 goto fail;
304 }
305 if ((tmp = kex_names_cat(ret, matching)) == NULL) {
306 r = SSH_ERR_ALLOC_FAIL;
307 goto fail;
308 }
309 free(ret);
310 ret = tmp;
311 }
312 if (ret == NULL || *ret == '\0') {
313 /* An empty name-list is an error */
314 /* XXX better error code? */
315 r = SSH_ERR_INVALID_ARGUMENT;
316 goto fail;
317 }
318
319 /* success */
320 *listp = ret;
321 ret = NULL;
322 r = 0;
323
324 fail:
325 free(matching);
326 free(opatterns);
327 free(list);
328 free(ret);
329 return r;
330 }
331