crypto/openssh/match.c

   1 /* $OpenBSD: match.c,v 1.43 2020/11/03 22:53:12 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  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41
  42 #include <ctype.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <stdarg.h>
  46 #include <stdio.h>
  47
  48 #include "xmalloc.h"
  49 #include "match.h"
  50 #include "misc.h"
  51
  52 /*
  53  * Returns true if the given string matches the pattern (which may contain ?
  54  * and * as wildcards), and zero if it does not match.
  55  */
  56 int
  57 match_pattern(const char *s, const char *pattern)
  58 {
  59         for (;;) {
  60                 /* If at end of pattern, accept if also at end of string. */
  61                 if (!*pattern)
  62                         return !*s;
  63
  64                 if (*pattern == '*') {
  65                         /* Skip this and any consecutive asterisks. */
  66                         while (*pattern == '*')
  67                                 pattern++;
  68
  69                         /* If at end of pattern, accept immediately. */
  70                         if (!*pattern)
  71                                 return 1;
  72
  73                         /* If next character in pattern is known, optimize. */
  74                         if (*pattern != '?' && *pattern != '*') {
  75                                 /*
  76                                  * Look instances of the next character in
  77                                  * pattern, and try to match starting from
  78                                  * those.
  79                                  */
  80                                 for (; *s; s++)
  81                                         if (*s == *pattern &&
  82                                             match_pattern(s + 1, pattern + 1))
  83                                                 return 1;
  84                                 /* Failed. */
  85                                 return 0;
  86                         }
  87                         /*
  88                          * Move ahead one character at a time and try to
  89                          * match at each position.
  90                          */
  91                         for (; *s; s++)
  92                                 if (match_pattern(s, pattern))
  93                                         return 1;
  94                         /* Failed. */
  95                         return 0;
  96                 }
  97                 /*
  98                  * There must be at least one more character in the string.
  99                  * If we are at the end, fail.
 100                  */
 101                 if (!*s)
 102                         return 0;
 103
 104                 /* Check if the next character of the string is acceptable. */
 105                 if (*pattern != '?' && *pattern != *s)
 106                         return 0;
 107
 108                 /* Move to the next character, both in string and in pattern. */
 109                 s++;
 110                 pattern++;
 111         }
 112         /* NOTREACHED */
 113 }
 114
 115 /*
 116  * Tries to match the string against the
 117  * comma-separated sequence of subpatterns (each possibly preceded by ! to
 118  * indicate negation).  Returns -1 if negation matches, 1 if there is
 119  * a positive match, 0 if there is no match at all.
 120  */
 121 int
 122 match_pattern_list(const char *string, const char *pattern, int dolower)
 123 {
 124         char sub[1024];
 125         int negated;
 126         int got_positive;
 127         u_int i, subi, len = strlen(pattern);
 128
 129         got_positive = 0;
 130         for (i = 0; i < len;) {
 131                 /* Check if the subpattern is negated. */
 132                 if (pattern[i] == '!') {
 133                         negated = 1;
 134                         i++;
 135                 } else
 136                         negated = 0;
 137
 138                 /*
 139                  * Extract the subpattern up to a comma or end.  Convert the
 140                  * subpattern to lowercase.
 141                  */
 142                 for (subi = 0;
 143                     i < len && subi < sizeof(sub) - 1 && pattern[i] != ',';
 144                     subi++, i++)
 145                         sub[subi] = dolower && isupper((u_char)pattern[i]) ?
 146                             tolower((u_char)pattern[i]) : pattern[i];
 147                 /* If subpattern too long, return failure (no match). */
 148                 if (subi >= sizeof(sub) - 1)
 149                         return 0;
 150
 151                 /* If the subpattern was terminated by a comma, then skip it. */
 152                 if (i < len && pattern[i] == ',')
 153                         i++;
 154
 155                 /* Null-terminate the subpattern. */
 156                 sub[subi] = '\0';
 157
 158                 /* Try to match the subpattern against the string. */
 159                 if (match_pattern(string, sub)) {
 160                         if (negated)
 161                                 return -1;              /* Negative */
 162                         else
 163                                 got_positive = 1;       /* Positive */
 164                 }
 165         }
 166
 167         /*
 168          * Return success if got a positive match.  If there was a negative
 169          * match, we have already returned -1 and never get here.
 170          */
 171         return got_positive;
 172 }
 173
 174 /* Match a list representing users or groups. */
 175 int
 176 match_usergroup_pattern_list(const char *string, const char *pattern)
 177 {
 178 #ifdef HAVE_CYGWIN
 179         /* Windows usernames may be Unicode and are not case sensitive */
 180         return cygwin_ug_match_pattern_list(string, pattern);
 181 #else
 182         /* Case sensitive match */
 183         return match_pattern_list(string, pattern, 0);
 184 #endif
 185 }
 186
 187 /*
 188  * Tries to match the host name (which must be in all lowercase) against the
 189  * comma-separated sequence of subpatterns (each possibly preceded by ! to
 190  * indicate negation).  Returns -1 if negation matches, 1 if there is
 191  * a positive match, 0 if there is no match at all.
 192  */
 193 int
 194 match_hostname(const char *host, const char *pattern)
 195 {
 196         char *hostcopy = xstrdup(host);
 197         int r;
 198
 199         lowercase(hostcopy);
 200         r = match_pattern_list(hostcopy, pattern, 1);
 201         free(hostcopy);
 202         return r;
 203 }
 204
 205 /*
 206  * returns 0 if we get a negative match for the hostname or the ip
 207  * or if we get no match at all.  returns -1 on error, or 1 on
 208  * successful match.
 209  */
 210 int
 211 match_host_and_ip(const char *host, const char *ipaddr,
 212     const char *patterns)
 213 {
 214         int mhost, mip;
 215
 216         if ((mip = addr_match_list(ipaddr, patterns)) == -2)
 217                 return -1; /* error in ipaddr match */
 218         else if (host == NULL || ipaddr == NULL || mip == -1)
 219                 return 0; /* negative ip address match, or testing pattern */
 220
 221         /* negative hostname match */
 222         if ((mhost = match_hostname(host, patterns)) == -1)
 223                 return 0;
 224         /* no match at all */
 225         if (mhost == 0 && mip == 0)
 226                 return 0;
 227         return 1;
 228 }
 229
 230 /*
 231  * Match user, user@host_or_ip, user@host_or_ip_list against pattern.
 232  * If user, host and ipaddr are all NULL then validate pattern/
 233  * Returns -1 on invalid pattern, 0 on no match, 1 on match.
 234  */
 235 int
 236 match_user(const char *user, const char *host, const char *ipaddr,
 237     const char *pattern)
 238 {
 239         char *p, *pat;
 240         int ret;
 241
 242         /* test mode */
 243         if (user == NULL && host == NULL && ipaddr == NULL) {
 244                 if ((p = strchr(pattern, '@')) != NULL &&
 245                     match_host_and_ip(NULL, NULL, p + 1) < 0)
 246                         return -1;
 247                 return 0;
 248         }
 249
 250         if ((p = strchr(pattern, '@')) == NULL)
 251                 return match_pattern(user, pattern);
 252
 253         pat = xstrdup(pattern);
 254         p = strchr(pat, '@');
 255         *p++ = '\0';
 256
 257         if ((ret = match_pattern(user, pat)) == 1)
 258                 ret = match_host_and_ip(host, ipaddr, p);
 259         free(pat);
 260
 261         return ret;
 262 }
 263
 264 /*
 265  * Returns first item from client-list that is also supported by server-list,
 266  * caller must free the returned string.
 267  */
 268 #define MAX_PROP        40
 269 #define SEP     ","
 270 char *
 271 match_list(const char *client, const char *server, u_int *next)
 272 {
 273         char *sproposals[MAX_PROP];
 274         char *c, *s, *p, *ret, *cp, *sp;
 275         int i, j, nproposals;
 276
 277         c = cp = xstrdup(client);
 278         s = sp = xstrdup(server);
 279
 280         for ((p = strsep(&sp, SEP)), i=0; p && *p != '\0';
 281             (p = strsep(&sp, SEP)), i++) {
 282                 if (i < MAX_PROP)
 283                         sproposals[i] = p;
 284                 else
 285                         break;
 286         }
 287         nproposals = i;
 288
 289         for ((p = strsep(&cp, SEP)), i=0; p && *p != '\0';
 290             (p = strsep(&cp, SEP)), i++) {
 291                 for (j = 0; j < nproposals; j++) {
 292                         if (strcmp(p, sproposals[j]) == 0) {
 293                                 ret = xstrdup(p);
 294                                 if (next != NULL)
 295                                         *next = (cp == NULL) ?
 296                                             strlen(c) : (u_int)(cp - c);
 297                                 free(c);
 298                                 free(s);
 299                                 return ret;
 300                         }
 301                 }
 302         }
 303         if (next != NULL)
 304                 *next = strlen(c);
 305         free(c);
 306         free(s);
 307         return NULL;
 308 }
 309
 310 /*
 311  * Filter proposal using pattern-list filter.
 312  * "denylist" determines sense of filter:
 313  * non-zero indicates that items matching filter should be excluded.
 314  * zero indicates that only items matching filter should be included.
 315  * returns NULL on allocation error, otherwise caller must free result.
 316  */
 317 static char *
 318 filter_list(const char *proposal, const char *filter, int denylist)
 319 {
 320         size_t len = strlen(proposal) + 1;
 321         char *fix_prop = malloc(len);
 322         char *orig_prop = strdup(proposal);
 323         char *cp, *tmp;
 324         int r;
 325
 326         if (fix_prop == NULL || orig_prop == NULL) {
 327                 free(orig_prop);
 328                 free(fix_prop);
 329                 return NULL;
 330         }
 331
 332         tmp = orig_prop;
 333         *fix_prop = '\0';
 334         while ((cp = strsep(&tmp, ",")) != NULL) {
 335                 r = match_pattern_list(cp, filter, 0);
 336                 if ((denylist && r != 1) || (!denylist && r == 1)) {
 337                         if (*fix_prop != '\0')
 338                                 strlcat(fix_prop, ",", len);
 339                         strlcat(fix_prop, cp, len);
 340                 }
 341         }
 342         free(orig_prop);
 343         return fix_prop;
 344 }
 345
 346 /*
 347  * Filters a comma-separated list of strings, excluding any entry matching
 348  * the 'filter' pattern list. Caller must free returned string.
 349  */
 350 char *
 351 match_filter_denylist(const char *proposal, const char *filter)
 352 {
 353         return filter_list(proposal, filter, 1);
 354 }
 355
 356 /*
 357  * Filters a comma-separated list of strings, including only entries matching
 358  * the 'filter' pattern list. Caller must free returned string.
 359  */
 360 char *
 361 match_filter_allowlist(const char *proposal, const char *filter)
 362 {
 363         return filter_list(proposal, filter, 0);
 364 }