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 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 47 struct kexalg { 48 char *name; 49 u_int type; 50 int ec_nid; 51 int hash_alg; 52 }; 53 static 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 { KEX_SNTRUP761X25519_SHA512_OLD, KEX_KEM_SNTRUP761X25519_SHA512, 0, 74 SSH_DIGEST_SHA512 }, 75 { KEX_MLKEM768X25519_SHA256, KEX_KEM_MLKEM768X25519_SHA256, 0, 76 SSH_DIGEST_SHA256 }, 77 { NULL, 0, -1, -1}, 78 }; 79 80 char * 81 kex_alg_list(char sep) 82 { 83 char *ret = NULL, *tmp; 84 size_t nlen, rlen = 0; 85 const struct kexalg *k; 86 87 for (k = kexalgs; k->name != NULL; k++) { 88 if (ret != NULL) 89 ret[rlen++] = sep; 90 nlen = strlen(k->name); 91 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 92 free(ret); 93 return NULL; 94 } 95 ret = tmp; 96 memcpy(ret + rlen, k->name, nlen + 1); 97 rlen += nlen; 98 } 99 return ret; 100 } 101 102 static const struct kexalg * 103 kex_alg_by_name(const char *name) 104 { 105 const struct kexalg *k; 106 107 for (k = kexalgs; k->name != NULL; k++) { 108 if (strcmp(k->name, name) == 0) 109 return k; 110 } 111 return NULL; 112 } 113 114 int 115 kex_name_valid(const char *name) 116 { 117 return kex_alg_by_name(name) != NULL; 118 } 119 120 u_int 121 kex_type_from_name(const char *name) 122 { 123 const struct kexalg *k; 124 125 if ((k = kex_alg_by_name(name)) == NULL) 126 return 0; 127 return k->type; 128 } 129 130 int 131 kex_hash_from_name(const char *name) 132 { 133 const struct kexalg *k; 134 135 if ((k = kex_alg_by_name(name)) == NULL) 136 return -1; 137 return k->hash_alg; 138 } 139 140 int 141 kex_nid_from_name(const char *name) 142 { 143 const struct kexalg *k; 144 145 if ((k = kex_alg_by_name(name)) == NULL) 146 return -1; 147 return k->ec_nid; 148 } 149 150 /* Validate KEX method name list */ 151 int 152 kex_names_valid(const char *names) 153 { 154 char *s, *cp, *p; 155 156 if (names == NULL || strcmp(names, "") == 0) 157 return 0; 158 if ((s = cp = strdup(names)) == NULL) 159 return 0; 160 for ((p = strsep(&cp, ",")); p && *p != '\0'; 161 (p = strsep(&cp, ","))) { 162 if (kex_alg_by_name(p) == NULL) { 163 error("Unsupported KEX algorithm \"%.100s\"", p); 164 free(s); 165 return 0; 166 } 167 } 168 debug3("kex names ok: [%s]", names); 169 free(s); 170 return 1; 171 } 172 173 /* returns non-zero if proposal contains any algorithm from algs */ 174 int 175 kex_has_any_alg(const char *proposal, const char *algs) 176 { 177 char *cp; 178 179 if ((cp = match_list(proposal, algs, NULL)) == NULL) 180 return 0; 181 free(cp); 182 return 1; 183 } 184 185 /* 186 * Concatenate algorithm names, avoiding duplicates in the process. 187 * Caller must free returned string. 188 */ 189 char * 190 kex_names_cat(const char *a, const char *b) 191 { 192 char *ret = NULL, *tmp = NULL, *cp, *p; 193 size_t len; 194 195 if (a == NULL || *a == '\0') 196 return strdup(b); 197 if (b == NULL || *b == '\0') 198 return strdup(a); 199 if (strlen(b) > 1024*1024) 200 return NULL; 201 len = strlen(a) + strlen(b) + 2; 202 if ((tmp = cp = strdup(b)) == NULL || 203 (ret = calloc(1, len)) == NULL) { 204 free(tmp); 205 return NULL; 206 } 207 strlcpy(ret, a, len); 208 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) { 209 if (kex_has_any_alg(ret, p)) 210 continue; /* Algorithm already present */ 211 if (strlcat(ret, ",", len) >= len || 212 strlcat(ret, p, len) >= len) { 213 free(tmp); 214 free(ret); 215 return NULL; /* Shouldn't happen */ 216 } 217 } 218 free(tmp); 219 return ret; 220 } 221 222 /* 223 * Assemble a list of algorithms from a default list and a string from a 224 * configuration file. The user-provided string may begin with '+' to 225 * indicate that it should be appended to the default, '-' that the 226 * specified names should be removed, or '^' that they should be placed 227 * at the head. 228 */ 229 int 230 kex_assemble_names(char **listp, const char *def, const char *all) 231 { 232 char *cp, *tmp, *patterns; 233 char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL; 234 int r = SSH_ERR_INTERNAL_ERROR; 235 236 if (listp == NULL || def == NULL || all == NULL) 237 return SSH_ERR_INVALID_ARGUMENT; 238 239 if (*listp == NULL || **listp == '\0') { 240 if ((*listp = strdup(def)) == NULL) 241 return SSH_ERR_ALLOC_FAIL; 242 return 0; 243 } 244 245 list = *listp; 246 *listp = NULL; 247 if (*list == '+') { 248 /* Append names to default list */ 249 if ((tmp = kex_names_cat(def, list + 1)) == NULL) { 250 r = SSH_ERR_ALLOC_FAIL; 251 goto fail; 252 } 253 free(list); 254 list = tmp; 255 } else if (*list == '-') { 256 /* Remove names from default list */ 257 if ((*listp = match_filter_denylist(def, list + 1)) == NULL) { 258 r = SSH_ERR_ALLOC_FAIL; 259 goto fail; 260 } 261 free(list); 262 /* filtering has already been done */ 263 return 0; 264 } else if (*list == '^') { 265 /* Place names at head of default list */ 266 if ((tmp = kex_names_cat(list + 1, def)) == NULL) { 267 r = SSH_ERR_ALLOC_FAIL; 268 goto fail; 269 } 270 free(list); 271 list = tmp; 272 } else { 273 /* Explicit list, overrides default - just use "list" as is */ 274 } 275 276 /* 277 * The supplied names may be a pattern-list. For the -list case, 278 * the patterns are applied above. For the +list and explicit list 279 * cases we need to do it now. 280 */ 281 ret = NULL; 282 if ((patterns = opatterns = strdup(list)) == NULL) { 283 r = SSH_ERR_ALLOC_FAIL; 284 goto fail; 285 } 286 /* Apply positive (i.e. non-negated) patterns from the list */ 287 while ((cp = strsep(&patterns, ",")) != NULL) { 288 if (*cp == '!') { 289 /* negated matches are not supported here */ 290 r = SSH_ERR_INVALID_ARGUMENT; 291 goto fail; 292 } 293 free(matching); 294 if ((matching = match_filter_allowlist(all, cp)) == NULL) { 295 r = SSH_ERR_ALLOC_FAIL; 296 goto fail; 297 } 298 if ((tmp = kex_names_cat(ret, matching)) == NULL) { 299 r = SSH_ERR_ALLOC_FAIL; 300 goto fail; 301 } 302 free(ret); 303 ret = tmp; 304 } 305 if (ret == NULL || *ret == '\0') { 306 /* An empty name-list is an error */ 307 /* XXX better error code? */ 308 r = SSH_ERR_INVALID_ARGUMENT; 309 goto fail; 310 } 311 312 /* success */ 313 *listp = ret; 314 ret = NULL; 315 r = 0; 316 317 fail: 318 free(matching); 319 free(opatterns); 320 free(list); 321 free(ret); 322 return r; 323 } 324