1 /* $OpenBSD: match.c,v 1.46 2026/05/31 04:19:16 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Simple pattern matching, with '*' and '?' as wildcards. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 */ 14 /* 15 * Copyright (c) 2000 Markus Friedl. All rights reserved. 16 * Copyright (c) 2026 Damien Miller. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 41 #include <sys/types.h> 42 43 #include <ctype.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <stdarg.h> 47 #include <stdio.h> 48 49 #include "xmalloc.h" 50 #include "match.h" 51 #include "misc.h" 52 53 /* 54 * Computes the epsilon closure of an NFA set. 55 * In our wildcard grammar, epsilon transitions only exist for '*' wildcards, 56 * allowing us to transition from state i to i+1 without consuming input. 57 * 58 * This function modifies 'states' in place. 59 */ 60 static void 61 epsilon_closure(char *states, const char *pattern, size_t M) 62 { 63 size_t i; 64 65 /* only need a forward pass as there are no back jumps in our grammar */ 66 for (i = 0; i < M; i++) { 67 if (!states[i] || pattern[i] != '*') 68 continue; 69 /* 70 * State i is active, and pattern[i] is '*', so we can 71 * epsilon-transition to i+1. 72 */ 73 states[i + 1] = 1; 74 } 75 } 76 77 /* 78 * Returns true if the given string matches the pattern (which may contain ? 79 * and * as wildcards), and zero if it does not match. Uses an NFA internally. 80 */ 81 int 82 match_pattern(const char *s, const char *pattern) 83 { 84 size_t M; 85 size_t i; 86 char *states, *next_states, *tmp; 87 int active, matched = 0; 88 89 /* trivial case: empty pattern vs empty input */ 90 if ((M = strlen(pattern)) == 0) 91 return *s == '\0'; 92 93 /* A state for each pattern character, plus one final accepting state */ 94 states = xcalloc(M + 1, sizeof(*states)); 95 next_states = xcalloc(M + 1, sizeof(*next_states)); 96 97 /* Initial state: state 0 is active */ 98 states[0] = 1; 99 /* Other states might be reachable now if the pattern starts with '*' */ 100 epsilon_closure(states, pattern, M); 101 102 for (; *s; s++) { 103 memset(next_states, 0, M + 1); 104 105 /* Calculate the reachable next states given the input char */ 106 for (i = 0; i < M; i++) { 107 if (!states[i]) 108 continue; 109 if (pattern[i] == '*') { 110 /* 111 * '*' matches any character, so we can 112 * stay in state i 113 */ 114 next_states[i] = 1; 115 } else if (pattern[i] == '?' || pattern[i] == *s) { 116 /* 117 * '?' matches any character, or we have 118 * a literal match. 119 */ 120 next_states[i + 1] = 1; 121 } 122 } 123 124 /* Expand the reachable next states with epsilon transitions */ 125 epsilon_closure(next_states, pattern, M); 126 127 /* Swap states and next_states */ 128 tmp = states; 129 states = next_states; 130 next_states = tmp; 131 132 /* Check if we have any active pattern states left */ 133 active = 0; 134 for (i = 0; i <= M; i++) { 135 if (states[i]) { 136 active = 1; 137 break; 138 } 139 } 140 if (!active) 141 goto out; /* No active states, fail early */ 142 } 143 /* 144 * We matched only if we ended up in the final, accepting state 145 * after consuming all the input. 146 */ 147 matched = states[M]; 148 out: 149 free(states); 150 free(next_states); 151 return matched; 152 } 153 154 /* 155 * Tries to match the string against the 156 * comma-separated sequence of subpatterns (each possibly preceded by ! to 157 * indicate negation). Returns -1 if negation matches, 1 if there is 158 * a positive match, 0 if there is no match at all. 159 */ 160 int 161 match_pattern_list(const char *string, const char *pattern, int dolower) 162 { 163 char sub[1024]; 164 int negated; 165 int got_positive; 166 u_int i, subi, len = strlen(pattern); 167 168 got_positive = 0; 169 for (i = 0; i < len;) { 170 /* Check if the subpattern is negated. */ 171 if (pattern[i] == '!') { 172 negated = 1; 173 i++; 174 } else 175 negated = 0; 176 177 /* 178 * Extract the subpattern up to a comma or end. Convert the 179 * subpattern to lowercase. 180 */ 181 for (subi = 0; 182 i < len && subi < sizeof(sub) - 1 && pattern[i] != ','; 183 subi++, i++) 184 sub[subi] = dolower && isupper((u_char)pattern[i]) ? 185 tolower((u_char)pattern[i]) : pattern[i]; 186 /* If subpattern too long, return failure (no match). */ 187 if (subi >= sizeof(sub) - 1) 188 return 0; 189 190 /* If the subpattern was terminated by a comma, then skip it. */ 191 if (i < len && pattern[i] == ',') 192 i++; 193 194 /* Null-terminate the subpattern. */ 195 sub[subi] = '\0'; 196 197 /* Try to match the subpattern against the string. */ 198 if (match_pattern(string, sub)) { 199 if (negated) 200 return -1; /* Negative */ 201 else 202 got_positive = 1; /* Positive */ 203 } 204 } 205 206 /* 207 * Return success if got a positive match. If there was a negative 208 * match, we have already returned -1 and never get here. 209 */ 210 return got_positive; 211 } 212 213 /* Match a list representing users or groups. */ 214 int 215 match_usergroup_pattern_list(const char *string, const char *pattern) 216 { 217 #ifdef HAVE_CYGWIN 218 /* Windows usernames may be Unicode and are not case sensitive */ 219 return cygwin_ug_match_pattern_list(string, pattern); 220 #else 221 /* Case sensitive match */ 222 return match_pattern_list(string, pattern, 0); 223 #endif 224 } 225 226 /* 227 * Tries to match the host name (which must be in all lowercase) against the 228 * comma-separated sequence of subpatterns (each possibly preceded by ! to 229 * indicate negation). Returns -1 if negation matches, 1 if there is 230 * a positive match, 0 if there is no match at all. 231 */ 232 int 233 match_hostname(const char *host, const char *pattern) 234 { 235 char *hostcopy = xstrdup(host); 236 int r; 237 238 lowercase(hostcopy); 239 r = match_pattern_list(hostcopy, pattern, 1); 240 free(hostcopy); 241 return r; 242 } 243 244 /* 245 * returns 0 if we get a negative match for the hostname or the ip 246 * or if we get no match at all. returns -1 on error, or 1 on 247 * successful match. 248 */ 249 int 250 match_host_and_ip(const char *host, const char *ipaddr, 251 const char *patterns) 252 { 253 int mhost, mip; 254 255 if ((mip = addr_match_list(ipaddr, patterns)) == -2) 256 return -1; /* error in ipaddr match */ 257 else if (host == NULL || ipaddr == NULL || mip == -1) 258 return 0; /* negative ip address match, or testing pattern */ 259 260 /* negative hostname match */ 261 if ((mhost = match_hostname(host, patterns)) == -1) 262 return 0; 263 /* no match at all */ 264 if (mhost == 0 && mip == 0) 265 return 0; 266 return 1; 267 } 268 269 /* 270 * Match user, user@host_or_ip, user@host_or_ip_list against pattern. 271 * If user, host and ipaddr are all NULL then validate pattern/ 272 * Returns -1 on invalid pattern, 0 on no match, 1 on match. 273 */ 274 int 275 match_user(const char *user, const char *host, const char *ipaddr, 276 const char *pattern) 277 { 278 char *p, *pat; 279 int ret; 280 281 /* test mode */ 282 if (user == NULL && host == NULL && ipaddr == NULL) { 283 if ((p = strrchr(pattern, '@')) != NULL && 284 match_host_and_ip(NULL, NULL, p + 1) < 0) 285 return -1; 286 return 0; 287 } 288 289 if (user == NULL) 290 return 0; /* shouldn't happen */ 291 292 if (strrchr(pattern, '@') == NULL) 293 return match_pattern(user, pattern); 294 295 pat = xstrdup(pattern); 296 p = strrchr(pat, '@'); 297 *p++ = '\0'; 298 299 if ((ret = match_pattern(user, pat)) == 1) 300 ret = match_host_and_ip(host, ipaddr, p); 301 free(pat); 302 303 return ret; 304 } 305 306 /* 307 * Returns first item from client-list that is also supported by server-list, 308 * caller must free the returned string. 309 */ 310 #define MAX_PROP 40 311 #define SEP "," 312 char * 313 match_list(const char *client, const char *server, u_int *next) 314 { 315 char *sproposals[MAX_PROP]; 316 char *c, *s, *p, *ret, *cp, *sp; 317 int i, j, nproposals; 318 319 c = cp = xstrdup(client); 320 s = sp = xstrdup(server); 321 322 for ((p = strsep(&sp, SEP)), i=0; p && *p != '\0'; 323 (p = strsep(&sp, SEP)), i++) { 324 if (i < MAX_PROP) 325 sproposals[i] = p; 326 else 327 break; 328 } 329 nproposals = i; 330 331 for ((p = strsep(&cp, SEP)), i=0; p && *p != '\0'; 332 (p = strsep(&cp, SEP)), i++) { 333 for (j = 0; j < nproposals; j++) { 334 if (strcmp(p, sproposals[j]) == 0) { 335 ret = xstrdup(p); 336 if (next != NULL) 337 *next = (cp == NULL) ? 338 strlen(c) : (u_int)(cp - c); 339 free(c); 340 free(s); 341 return ret; 342 } 343 } 344 } 345 if (next != NULL) 346 *next = strlen(c); 347 free(c); 348 free(s); 349 return NULL; 350 } 351 352 /* 353 * Filter proposal using pattern-list filter. 354 * "denylist" determines sense of filter: 355 * non-zero indicates that items matching filter should be excluded. 356 * zero indicates that only items matching filter should be included. 357 * returns NULL on allocation error, otherwise caller must free result. 358 */ 359 static char * 360 filter_list(const char *proposal, const char *filter, int denylist) 361 { 362 size_t len = strlen(proposal) + 1; 363 char *fix_prop = malloc(len); 364 char *orig_prop = strdup(proposal); 365 char *cp, *tmp; 366 int r; 367 368 if (fix_prop == NULL || orig_prop == NULL) { 369 free(orig_prop); 370 free(fix_prop); 371 return NULL; 372 } 373 374 tmp = orig_prop; 375 *fix_prop = '\0'; 376 while ((cp = strsep(&tmp, ",")) != NULL) { 377 r = match_pattern_list(cp, filter, 0); 378 if ((denylist && r != 1) || (!denylist && r == 1)) { 379 if (*fix_prop != '\0') 380 strlcat(fix_prop, ",", len); 381 strlcat(fix_prop, cp, len); 382 } 383 } 384 free(orig_prop); 385 return fix_prop; 386 } 387 388 /* 389 * Filters a comma-separated list of strings, excluding any entry matching 390 * the 'filter' pattern list. Caller must free returned string. 391 */ 392 char * 393 match_filter_denylist(const char *proposal, const char *filter) 394 { 395 return filter_list(proposal, filter, 1); 396 } 397 398 /* 399 * Filters a comma-separated list of strings, including only entries matching 400 * the 'filter' pattern list. Caller must free returned string. 401 */ 402 char * 403 match_filter_allowlist(const char *proposal, const char *filter) 404 { 405 return filter_list(proposal, filter, 0); 406 } 407