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