1 /* 2 * Copyright (c) 2000 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #include "includes.h" 26 RCSID("$OpenBSD: auth.c,v 1.27 2001/07/11 18:26:15 markus Exp $"); 27 28 #include <libgen.h> 29 30 #include "xmalloc.h" 31 #include "match.h" 32 #include "groupaccess.h" 33 #include "log.h" 34 #include "servconf.h" 35 #include "auth.h" 36 #include "auth-options.h" 37 #include "canohost.h" 38 #include "buffer.h" 39 #include "bufaux.h" 40 #include "uidswap.h" 41 #include "tildexpand.h" 42 43 /* import */ 44 extern ServerOptions options; 45 46 /* 47 * Check if the user is allowed to log in via ssh. If user is listed 48 * in DenyUsers or one of user's groups is listed in DenyGroups, false 49 * will be returned. If AllowUsers isn't empty and user isn't listed 50 * there, or if AllowGroups isn't empty and one of user's groups isn't 51 * listed there, false will be returned. 52 * If the user's shell is not executable, false will be returned. 53 * Otherwise true is returned. 54 */ 55 int 56 allowed_user(struct passwd * pw) 57 { 58 struct stat st; 59 const char *hostname = NULL, *ipaddr = NULL; 60 char *shell; 61 int i; 62 63 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 64 if (!pw || !pw->pw_name) 65 return 0; 66 67 /* 68 * Get the shell from the password data. An empty shell field is 69 * legal, and means /bin/sh. 70 */ 71 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 72 73 /* deny if shell does not exists or is not executable */ 74 if (stat(shell, &st) != 0) 75 return 0; 76 if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)))) 77 return 0; 78 79 if (options.num_deny_users > 0 || options.num_allow_users > 0) { 80 hostname = get_canonical_hostname(options.reverse_mapping_check); 81 ipaddr = get_remote_ipaddr(); 82 } 83 84 /* Return false if user is listed in DenyUsers */ 85 if (options.num_deny_users > 0) { 86 for (i = 0; i < options.num_deny_users; i++) 87 if (match_user(pw->pw_name, hostname, ipaddr, 88 options.deny_users[i])) 89 return 0; 90 } 91 /* Return false if AllowUsers isn't empty and user isn't listed there */ 92 if (options.num_allow_users > 0) { 93 for (i = 0; i < options.num_allow_users; i++) 94 if (match_user(pw->pw_name, hostname, ipaddr, 95 options.allow_users[i])) 96 break; 97 /* i < options.num_allow_users iff we break for loop */ 98 if (i >= options.num_allow_users) 99 return 0; 100 } 101 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 102 /* Get the user's group access list (primary and supplementary) */ 103 if (ga_init(pw->pw_name, pw->pw_gid) == 0) 104 return 0; 105 106 /* Return false if one of user's groups is listed in DenyGroups */ 107 if (options.num_deny_groups > 0) 108 if (ga_match(options.deny_groups, 109 options.num_deny_groups)) { 110 ga_free(); 111 return 0; 112 } 113 /* 114 * Return false if AllowGroups isn't empty and one of user's groups 115 * isn't listed there 116 */ 117 if (options.num_allow_groups > 0) 118 if (!ga_match(options.allow_groups, 119 options.num_allow_groups)) { 120 ga_free(); 121 return 0; 122 } 123 ga_free(); 124 } 125 /* We found no reason not to let this user try to log on... */ 126 return 1; 127 } 128 129 Authctxt * 130 authctxt_new(void) 131 { 132 Authctxt *authctxt = xmalloc(sizeof(*authctxt)); 133 memset(authctxt, 0, sizeof(*authctxt)); 134 return authctxt; 135 } 136 137 void 138 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 139 { 140 void (*authlog) (const char *fmt,...) = verbose; 141 char *authmsg; 142 143 /* Raise logging level */ 144 if (authenticated == 1 || 145 !authctxt->valid || 146 authctxt->failures >= AUTH_FAIL_LOG || 147 strcmp(method, "password") == 0) 148 authlog = log; 149 150 if (authctxt->postponed) 151 authmsg = "Postponed"; 152 else 153 authmsg = authenticated ? "Accepted" : "Failed"; 154 155 authlog("%s %s for %s%.100s from %.200s port %d%s", 156 authmsg, 157 method, 158 authctxt->valid ? "" : "illegal user ", 159 authctxt->valid && authctxt->pw->pw_uid == 0 ? "ROOT" : authctxt->user, 160 get_remote_ipaddr(), 161 get_remote_port(), 162 info); 163 } 164 165 /* 166 * Check whether root logins are disallowed. 167 */ 168 int 169 auth_root_allowed(char *method) 170 { 171 switch (options.permit_root_login) { 172 case PERMIT_YES: 173 return 1; 174 break; 175 case PERMIT_NO_PASSWD: 176 if (strcmp(method, "password") != 0) 177 return 1; 178 break; 179 case PERMIT_FORCED_ONLY: 180 if (forced_command) { 181 log("Root login accepted for forced command."); 182 return 1; 183 } 184 break; 185 } 186 log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 187 return 0; 188 } 189 190 191 /* 192 * Given a template and a passwd structure, build a filename 193 * by substituting % tokenised options. Currently, %% becomes '%', 194 * %h becomes the home directory and %u the username. 195 * 196 * This returns a buffer allocated by xmalloc. 197 */ 198 char * 199 expand_filename(const char *filename, struct passwd *pw) 200 { 201 Buffer buffer; 202 char *file; 203 const char *cp; 204 205 /* 206 * Build the filename string in the buffer by making the appropriate 207 * substitutions to the given file name. 208 */ 209 buffer_init(&buffer); 210 for (cp = filename; *cp; cp++) { 211 if (cp[0] == '%' && cp[1] == '%') { 212 buffer_append(&buffer, "%", 1); 213 cp++; 214 continue; 215 } 216 if (cp[0] == '%' && cp[1] == 'h') { 217 buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); 218 cp++; 219 continue; 220 } 221 if (cp[0] == '%' && cp[1] == 'u') { 222 buffer_append(&buffer, pw->pw_name, 223 strlen(pw->pw_name)); 224 cp++; 225 continue; 226 } 227 buffer_append(&buffer, cp, 1); 228 } 229 buffer_append(&buffer, "\0", 1); 230 231 /* 232 * Ensure that filename starts anchored. If not, be backward 233 * compatible and prepend the '%h/' 234 */ 235 file = xmalloc(MAXPATHLEN); 236 cp = buffer_ptr(&buffer); 237 if (*cp != '/') 238 snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); 239 else 240 strlcpy(file, cp, MAXPATHLEN); 241 242 buffer_free(&buffer); 243 return file; 244 } 245 246 char * 247 authorized_keys_file(struct passwd *pw) 248 { 249 return expand_filename(options.authorized_keys_file, pw); 250 } 251 252 char * 253 authorized_keys_file2(struct passwd *pw) 254 { 255 return expand_filename(options.authorized_keys_file2, pw); 256 } 257 258 /* return ok if key exists in sysfile or userfile */ 259 HostStatus 260 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 261 const char *sysfile, const char *userfile) 262 { 263 Key *found; 264 char *user_hostfile; 265 struct stat st; 266 int host_status; 267 268 /* Check if we know the host and its host key. */ 269 found = key_new(key->type); 270 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 271 272 if (host_status != HOST_OK && userfile != NULL) { 273 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 274 if (options.strict_modes && 275 (stat(user_hostfile, &st) == 0) && 276 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 277 (st.st_mode & 022) != 0)) { 278 log("Authentication refused for %.100s: " 279 "bad owner or modes for %.200s", 280 pw->pw_name, user_hostfile); 281 } else { 282 temporarily_use_uid(pw); 283 host_status = check_host_in_hostfile(user_hostfile, 284 host, key, found, NULL); 285 restore_uid(); 286 } 287 xfree(user_hostfile); 288 } 289 key_free(found); 290 291 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 292 "ok" : "not found", host); 293 return host_status; 294 } 295 296 297 /* 298 * Check a given file for security. This is defined as all components 299 * of the path to the file must either be owned by either the owner of 300 * of the file or root and no directories must be group or world writable. 301 * 302 * XXX Should any specific check be done for sym links ? 303 * 304 * Takes an open file descriptor, the file name, a uid and and 305 * error buffer plus max size as arguments. 306 * 307 * Returns 0 on success and -1 on failure 308 */ 309 int 310 secure_filename(FILE *f, const char *file, struct passwd *pw, 311 char *err, size_t errlen) 312 { 313 uid_t uid = pw->pw_uid; 314 char buf[MAXPATHLEN]; 315 char *cp; 316 struct stat st; 317 318 if (realpath(file, buf) == NULL) { 319 snprintf(err, errlen, "realpath %s failed: %s", file, 320 strerror(errno)); 321 return -1; 322 } 323 324 /* check the open file to avoid races */ 325 if (fstat(fileno(f), &st) < 0 || 326 (st.st_uid != 0 && st.st_uid != uid) || 327 (st.st_mode & 022) != 0) { 328 snprintf(err, errlen, "bad ownership or modes for file %s", 329 buf); 330 return -1; 331 } 332 333 /* for each component of the canonical path, walking upwards */ 334 for (;;) { 335 if ((cp = dirname(buf)) == NULL) { 336 snprintf(err, errlen, "dirname() failed"); 337 return -1; 338 } 339 strlcpy(buf, cp, sizeof(buf)); 340 341 debug3("secure_filename: checking '%s'", buf); 342 if (stat(buf, &st) < 0 || 343 (st.st_uid != 0 && st.st_uid != uid) || 344 (st.st_mode & 022) != 0) { 345 snprintf(err, errlen, 346 "bad ownership or modes for directory %s", buf); 347 return -1; 348 } 349 350 /* If are passed the homedir then we can stop */ 351 if (strcmp(pw->pw_dir, buf) == 0) { 352 debug3("secure_filename: terminating check at '%s'", 353 buf); 354 break; 355 } 356 /* 357 * dirname should always complete with a "/" path, 358 * but we can be paranoid and check for "." too 359 */ 360 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 361 break; 362 } 363 return 0; 364 } 365