1 /* $OpenBSD: kex-names.c,v 1.4 2024/09/09 02:39:57 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 { KEX_SNTRUP761X25519_SHA512_OLD, KEX_KEM_SNTRUP761X25519_SHA512, 0,
83 SSH_DIGEST_SHA512 },
84 #endif
85 #ifdef USE_MLKEM768X25519
86 { KEX_MLKEM768X25519_SHA256, KEX_KEM_MLKEM768X25519_SHA256, 0,
87 SSH_DIGEST_SHA256 },
88 #endif
89 #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
90 { NULL, 0, -1, -1},
91 };
92
93 char *
kex_alg_list(char sep)94 kex_alg_list(char sep)
95 {
96 char *ret = NULL, *tmp;
97 size_t nlen, rlen = 0;
98 const struct kexalg *k;
99
100 for (k = kexalgs; k->name != NULL; k++) {
101 if (ret != NULL)
102 ret[rlen++] = sep;
103 nlen = strlen(k->name);
104 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
105 free(ret);
106 return NULL;
107 }
108 ret = tmp;
109 memcpy(ret + rlen, k->name, nlen + 1);
110 rlen += nlen;
111 }
112 return ret;
113 }
114
115 static const struct kexalg *
kex_alg_by_name(const char * name)116 kex_alg_by_name(const char *name)
117 {
118 const struct kexalg *k;
119
120 for (k = kexalgs; k->name != NULL; k++) {
121 if (strcmp(k->name, name) == 0)
122 return k;
123 }
124 return NULL;
125 }
126
127 int
kex_name_valid(const char * name)128 kex_name_valid(const char *name)
129 {
130 return kex_alg_by_name(name) != NULL;
131 }
132
133 u_int
kex_type_from_name(const char * name)134 kex_type_from_name(const char *name)
135 {
136 const struct kexalg *k;
137
138 if ((k = kex_alg_by_name(name)) == NULL)
139 return 0;
140 return k->type;
141 }
142
143 int
kex_hash_from_name(const char * name)144 kex_hash_from_name(const char *name)
145 {
146 const struct kexalg *k;
147
148 if ((k = kex_alg_by_name(name)) == NULL)
149 return -1;
150 return k->hash_alg;
151 }
152
153 int
kex_nid_from_name(const char * name)154 kex_nid_from_name(const char *name)
155 {
156 const struct kexalg *k;
157
158 if ((k = kex_alg_by_name(name)) == NULL)
159 return -1;
160 return k->ec_nid;
161 }
162
163 /* Validate KEX method name list */
164 int
kex_names_valid(const char * names)165 kex_names_valid(const char *names)
166 {
167 char *s, *cp, *p;
168
169 if (names == NULL || strcmp(names, "") == 0)
170 return 0;
171 if ((s = cp = strdup(names)) == NULL)
172 return 0;
173 for ((p = strsep(&cp, ",")); p && *p != '\0';
174 (p = strsep(&cp, ","))) {
175 if (kex_alg_by_name(p) == NULL) {
176 error("Unsupported KEX algorithm \"%.100s\"", p);
177 free(s);
178 return 0;
179 }
180 }
181 debug3("kex names ok: [%s]", names);
182 free(s);
183 return 1;
184 }
185
186 /* returns non-zero if proposal contains any algorithm from algs */
187 int
kex_has_any_alg(const char * proposal,const char * algs)188 kex_has_any_alg(const char *proposal, const char *algs)
189 {
190 char *cp;
191
192 if ((cp = match_list(proposal, algs, NULL)) == NULL)
193 return 0;
194 free(cp);
195 return 1;
196 }
197
198 /*
199 * Concatenate algorithm names, avoiding duplicates in the process.
200 * Caller must free returned string.
201 */
202 char *
kex_names_cat(const char * a,const char * b)203 kex_names_cat(const char *a, const char *b)
204 {
205 char *ret = NULL, *tmp = NULL, *cp, *p;
206 size_t len;
207
208 if (a == NULL || *a == '\0')
209 return strdup(b);
210 if (b == NULL || *b == '\0')
211 return strdup(a);
212 if (strlen(b) > 1024*1024)
213 return NULL;
214 len = strlen(a) + strlen(b) + 2;
215 if ((tmp = cp = strdup(b)) == NULL ||
216 (ret = calloc(1, len)) == NULL) {
217 free(tmp);
218 return NULL;
219 }
220 strlcpy(ret, a, len);
221 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
222 if (kex_has_any_alg(ret, p))
223 continue; /* Algorithm already present */
224 if (strlcat(ret, ",", len) >= len ||
225 strlcat(ret, p, len) >= len) {
226 free(tmp);
227 free(ret);
228 return NULL; /* Shouldn't happen */
229 }
230 }
231 free(tmp);
232 return ret;
233 }
234
235 /*
236 * Assemble a list of algorithms from a default list and a string from a
237 * configuration file. The user-provided string may begin with '+' to
238 * indicate that it should be appended to the default, '-' that the
239 * specified names should be removed, or '^' that they should be placed
240 * at the head.
241 */
242 int
kex_assemble_names(char ** listp,const char * def,const char * all)243 kex_assemble_names(char **listp, const char *def, const char *all)
244 {
245 char *cp, *tmp, *patterns;
246 char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;
247 int r = SSH_ERR_INTERNAL_ERROR;
248
249 if (listp == NULL || def == NULL || all == NULL)
250 return SSH_ERR_INVALID_ARGUMENT;
251
252 if (*listp == NULL || **listp == '\0') {
253 if ((*listp = strdup(def)) == NULL)
254 return SSH_ERR_ALLOC_FAIL;
255 return 0;
256 }
257
258 list = *listp;
259 *listp = NULL;
260 if (*list == '+') {
261 /* Append names to default list */
262 if ((tmp = kex_names_cat(def, list + 1)) == NULL) {
263 r = SSH_ERR_ALLOC_FAIL;
264 goto fail;
265 }
266 free(list);
267 list = tmp;
268 } else if (*list == '-') {
269 /* Remove names from default list */
270 if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {
271 r = SSH_ERR_ALLOC_FAIL;
272 goto fail;
273 }
274 free(list);
275 /* filtering has already been done */
276 return 0;
277 } else if (*list == '^') {
278 /* Place names at head of default list */
279 if ((tmp = kex_names_cat(list + 1, def)) == NULL) {
280 r = SSH_ERR_ALLOC_FAIL;
281 goto fail;
282 }
283 free(list);
284 list = tmp;
285 } else {
286 /* Explicit list, overrides default - just use "list" as is */
287 }
288
289 /*
290 * The supplied names may be a pattern-list. For the -list case,
291 * the patterns are applied above. For the +list and explicit list
292 * cases we need to do it now.
293 */
294 ret = NULL;
295 if ((patterns = opatterns = strdup(list)) == NULL) {
296 r = SSH_ERR_ALLOC_FAIL;
297 goto fail;
298 }
299 /* Apply positive (i.e. non-negated) patterns from the list */
300 while ((cp = strsep(&patterns, ",")) != NULL) {
301 if (*cp == '!') {
302 /* negated matches are not supported here */
303 r = SSH_ERR_INVALID_ARGUMENT;
304 goto fail;
305 }
306 free(matching);
307 if ((matching = match_filter_allowlist(all, cp)) == NULL) {
308 r = SSH_ERR_ALLOC_FAIL;
309 goto fail;
310 }
311 if ((tmp = kex_names_cat(ret, matching)) == NULL) {
312 r = SSH_ERR_ALLOC_FAIL;
313 goto fail;
314 }
315 free(ret);
316 ret = tmp;
317 }
318 if (ret == NULL || *ret == '\0') {
319 /* An empty name-list is an error */
320 /* XXX better error code? */
321 r = SSH_ERR_INVALID_ARGUMENT;
322 goto fail;
323 }
324
325 /* success */
326 *listp = ret;
327 ret = NULL;
328 r = 0;
329
330 fail:
331 free(matching);
332 free(opatterns);
333 free(list);
334 free(ret);
335 return r;
336 }
337