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 * 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 * 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 128 kex_name_valid(const char *name) 129 { 130 return kex_alg_by_name(name) != NULL; 131 } 132 133 u_int 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 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 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 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 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 * 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 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