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 * 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 * 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 122 kex_name_valid(const char *name) 123 { 124 return kex_alg_by_name(name) != NULL; 125 } 126 127 u_int 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 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 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 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 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 * 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 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