1 /* $NetBSD: kex-names.c,v 1.2 2024/07/08 22:33:43 christos Exp $ */ 2 /* $OpenBSD: kex-names.c,v 1.1 2024/05/17 00:32:32 djm Exp $ */ 3 /* 4 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: kex-names.c,v 1.2 2024/07/08 22:33:43 christos Exp $"); 29 30 #include <stdio.h> 31 #include <stdlib.h> 32 #include <string.h> 33 #include <unistd.h> 34 #include <signal.h> 35 36 #ifdef WITH_OPENSSL 37 #include <openssl/crypto.h> 38 #include <openssl/evp.h> 39 #endif 40 41 #include "kex.h" 42 #include "log.h" 43 #include "match.h" 44 #include "digest.h" 45 #include "misc.h" 46 47 #include "ssherr.h" 48 #include "xmalloc.h" 49 50 struct kexalg { 51 const char *name; 52 u_int type; 53 int ec_nid; 54 int hash_alg; 55 }; 56 static const struct kexalg kexalgs[] = { 57 #ifdef WITH_OPENSSL 58 { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 }, 59 { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 }, 60 { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 }, 61 { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 }, 62 { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 }, 63 { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 }, 64 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 }, 65 { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, 66 NID_X9_62_prime256v1, SSH_DIGEST_SHA256 }, 67 { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, 68 SSH_DIGEST_SHA384 }, 69 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, 70 SSH_DIGEST_SHA512 }, 71 #endif 72 { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, 73 { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, 74 { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0, 75 SSH_DIGEST_SHA512 }, 76 { NULL, 0, -1, -1}, 77 }; 78 79 char * 80 kex_alg_list(char sep) 81 { 82 char *ret = NULL, *tmp; 83 size_t nlen, rlen = 0; 84 const struct kexalg *k; 85 86 for (k = kexalgs; k->name != NULL; k++) { 87 if (ret != NULL) 88 ret[rlen++] = sep; 89 nlen = strlen(k->name); 90 if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { 91 free(ret); 92 return NULL; 93 } 94 ret = tmp; 95 memcpy(ret + rlen, k->name, nlen + 1); 96 rlen += nlen; 97 } 98 return ret; 99 } 100 101 static const struct kexalg * 102 kex_alg_by_name(const char *name) 103 { 104 const struct kexalg *k; 105 106 for (k = kexalgs; k->name != NULL; k++) { 107 if (strcmp(k->name, name) == 0) 108 return k; 109 } 110 return NULL; 111 } 112 113 int 114 kex_name_valid(const char *name) 115 { 116 return kex_alg_by_name(name) != NULL; 117 } 118 119 u_int 120 kex_type_from_name(const char *name) 121 { 122 const struct kexalg *k; 123 124 if ((k = kex_alg_by_name(name)) == NULL) 125 return 0; 126 return k->type; 127 } 128 129 int 130 kex_hash_from_name(const char *name) 131 { 132 const struct kexalg *k; 133 134 if ((k = kex_alg_by_name(name)) == NULL) 135 return -1; 136 return k->hash_alg; 137 } 138 139 int 140 kex_nid_from_name(const char *name) 141 { 142 const struct kexalg *k; 143 144 if ((k = kex_alg_by_name(name)) == NULL) 145 return -1; 146 return k->ec_nid; 147 } 148 149 /* Validate KEX method name list */ 150 int 151 kex_names_valid(const char *names) 152 { 153 char *s, *cp, *p; 154 155 if (names == NULL || strcmp(names, "") == 0) 156 return 0; 157 if ((s = cp = strdup(names)) == NULL) 158 return 0; 159 for ((p = strsep(&cp, ",")); p && *p != '\0'; 160 (p = strsep(&cp, ","))) { 161 if (kex_alg_by_name(p) == NULL) { 162 error("Unsupported KEX algorithm \"%.100s\"", p); 163 free(s); 164 return 0; 165 } 166 } 167 debug3("kex names ok: [%s]", names); 168 free(s); 169 return 1; 170 } 171 172 /* returns non-zero if proposal contains any algorithm from algs */ 173 int 174 kex_has_any_alg(const char *proposal, const char *algs) 175 { 176 char *cp; 177 178 if ((cp = match_list(proposal, algs, NULL)) == NULL) 179 return 0; 180 free(cp); 181 return 1; 182 } 183 184 /* 185 * Concatenate algorithm names, avoiding duplicates in the process. 186 * Caller must free returned string. 187 */ 188 char * 189 kex_names_cat(const char *a, const char *b) 190 { 191 char *ret = NULL, *tmp = NULL, *cp, *p; 192 size_t len; 193 194 if (a == NULL || *a == '\0') 195 return strdup(b); 196 if (b == NULL || *b == '\0') 197 return strdup(a); 198 if (strlen(b) > 1024*1024) 199 return NULL; 200 len = strlen(a) + strlen(b) + 2; 201 if ((tmp = cp = strdup(b)) == NULL || 202 (ret = calloc(1, len)) == NULL) { 203 free(tmp); 204 return NULL; 205 } 206 strlcpy(ret, a, len); 207 for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) { 208 if (kex_has_any_alg(ret, p)) 209 continue; /* Algorithm already present */ 210 if (strlcat(ret, ",", len) >= len || 211 strlcat(ret, p, len) >= len) { 212 free(tmp); 213 free(ret); 214 return NULL; /* Shouldn't happen */ 215 } 216 } 217 free(tmp); 218 return ret; 219 } 220 221 /* 222 * Assemble a list of algorithms from a default list and a string from a 223 * configuration file. The user-provided string may begin with '+' to 224 * indicate that it should be appended to the default, '-' that the 225 * specified names should be removed, or '^' that they should be placed 226 * at the head. 227 */ 228 int 229 kex_assemble_names(char **listp, const char *def, const char *all) 230 { 231 char *cp, *tmp, *patterns; 232 char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL; 233 int r = SSH_ERR_INTERNAL_ERROR; 234 235 if (listp == NULL || def == NULL || all == NULL) 236 return SSH_ERR_INVALID_ARGUMENT; 237 238 if (*listp == NULL || **listp == '\0') { 239 if ((*listp = strdup(def)) == NULL) 240 return SSH_ERR_ALLOC_FAIL; 241 return 0; 242 } 243 244 list = *listp; 245 *listp = NULL; 246 if (*list == '+') { 247 /* Append names to default list */ 248 if ((tmp = kex_names_cat(def, list + 1)) == NULL) { 249 r = SSH_ERR_ALLOC_FAIL; 250 goto fail; 251 } 252 free(list); 253 list = tmp; 254 } else if (*list == '-') { 255 /* Remove names from default list */ 256 if ((*listp = match_filter_denylist(def, list + 1)) == NULL) { 257 r = SSH_ERR_ALLOC_FAIL; 258 goto fail; 259 } 260 free(list); 261 /* filtering has already been done */ 262 return 0; 263 } else if (*list == '^') { 264 /* Place names at head of default list */ 265 if ((tmp = kex_names_cat(list + 1, def)) == NULL) { 266 r = SSH_ERR_ALLOC_FAIL; 267 goto fail; 268 } 269 free(list); 270 list = tmp; 271 } else { 272 /* Explicit list, overrides default - just use "list" as is */ 273 } 274 275 /* 276 * The supplied names may be a pattern-list. For the -list case, 277 * the patterns are applied above. For the +list and explicit list 278 * cases we need to do it now. 279 */ 280 ret = NULL; 281 if ((patterns = opatterns = strdup(list)) == NULL) { 282 r = SSH_ERR_ALLOC_FAIL; 283 goto fail; 284 } 285 /* Apply positive (i.e. non-negated) patterns from the list */ 286 while ((cp = strsep(&patterns, ",")) != NULL) { 287 if (*cp == '!') { 288 /* negated matches are not supported here */ 289 r = SSH_ERR_INVALID_ARGUMENT; 290 goto fail; 291 } 292 free(matching); 293 if ((matching = match_filter_allowlist(all, cp)) == NULL) { 294 r = SSH_ERR_ALLOC_FAIL; 295 goto fail; 296 } 297 if ((tmp = kex_names_cat(ret, matching)) == NULL) { 298 r = SSH_ERR_ALLOC_FAIL; 299 goto fail; 300 } 301 free(ret); 302 ret = tmp; 303 } 304 if (ret == NULL || *ret == '\0') { 305 /* An empty name-list is an error */ 306 /* XXX better error code? */ 307 r = SSH_ERR_INVALID_ARGUMENT; 308 goto fail; 309 } 310 311 /* success */ 312 *listp = ret; 313 ret = NULL; 314 r = 0; 315 316 fail: 317 free(matching); 318 free(opatterns); 319 free(list); 320 free(ret); 321 return r; 322 } 323