Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 1 | /* $OpenBSD: auth.c,v 1.110 2015/02/25 17:29:38 djm Exp $ */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 2 | /* |
| 3 | * Copyright (c) 2000 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 | #include "includes.h" |
| 27 | |
| 28 | #include <sys/types.h> |
| 29 | #include <sys/stat.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 30 | |
| 31 | #include <netinet/in.h> |
| 32 | |
| 33 | #include <errno.h> |
| 34 | #include <fcntl.h> |
| 35 | #ifdef HAVE_PATHS_H |
| 36 | # include <paths.h> |
| 37 | #endif |
| 38 | #include <pwd.h> |
| 39 | #ifdef HAVE_LOGIN_H |
| 40 | #include <login.h> |
| 41 | #endif |
| 42 | #ifdef USE_SHADOW |
| 43 | #include <shadow.h> |
| 44 | #endif |
| 45 | #ifdef HAVE_LIBGEN_H |
| 46 | #include <libgen.h> |
| 47 | #endif |
| 48 | #include <stdarg.h> |
| 49 | #include <stdio.h> |
| 50 | #include <string.h> |
| 51 | #include <unistd.h> |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 52 | #include <limits.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 53 | |
| 54 | #include "xmalloc.h" |
| 55 | #include "match.h" |
| 56 | #include "groupaccess.h" |
| 57 | #include "log.h" |
| 58 | #include "buffer.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 59 | #include "misc.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 60 | #include "servconf.h" |
| 61 | #include "key.h" |
| 62 | #include "hostfile.h" |
| 63 | #include "auth.h" |
| 64 | #include "auth-options.h" |
| 65 | #include "canohost.h" |
| 66 | #include "uidswap.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 67 | #include "packet.h" |
| 68 | #include "loginrec.h" |
| 69 | #ifdef GSSAPI |
| 70 | #include "ssh-gss.h" |
| 71 | #endif |
| 72 | #include "authfile.h" |
| 73 | #include "monitor_wrap.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 74 | #include "authfile.h" |
| 75 | #include "ssherr.h" |
| 76 | #include "compat.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 77 | |
| 78 | /* import */ |
| 79 | extern ServerOptions options; |
| 80 | extern int use_privsep; |
| 81 | extern Buffer loginmsg; |
| 82 | extern struct passwd *privsep_pw; |
| 83 | |
| 84 | /* Debugging messages */ |
| 85 | Buffer auth_debug; |
| 86 | int auth_debug_init; |
| 87 | |
| 88 | /* |
| 89 | * Check if the user is allowed to log in via ssh. If user is listed |
| 90 | * in DenyUsers or one of user's groups is listed in DenyGroups, false |
| 91 | * will be returned. If AllowUsers isn't empty and user isn't listed |
| 92 | * there, or if AllowGroups isn't empty and one of user's groups isn't |
| 93 | * listed there, false will be returned. |
| 94 | * If the user's shell is not executable, false will be returned. |
| 95 | * Otherwise true is returned. |
| 96 | */ |
| 97 | int |
| 98 | allowed_user(struct passwd * pw) |
| 99 | { |
| 100 | struct stat st; |
| 101 | const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; |
| 102 | u_int i; |
| 103 | #ifdef USE_SHADOW |
| 104 | struct spwd *spw = NULL; |
| 105 | #endif |
| 106 | |
| 107 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ |
| 108 | if (!pw || !pw->pw_name) |
| 109 | return 0; |
| 110 | |
| 111 | #ifdef USE_SHADOW |
| 112 | if (!options.use_pam) |
| 113 | spw = getspnam(pw->pw_name); |
| 114 | #ifdef HAS_SHADOW_EXPIRE |
| 115 | if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) |
| 116 | return 0; |
| 117 | #endif /* HAS_SHADOW_EXPIRE */ |
| 118 | #endif /* USE_SHADOW */ |
| 119 | |
| 120 | /* grab passwd field for locked account check */ |
| 121 | passwd = pw->pw_passwd; |
| 122 | #ifdef USE_SHADOW |
| 123 | if (spw != NULL) |
| 124 | #ifdef USE_LIBIAF |
| 125 | passwd = get_iaf_password(pw); |
| 126 | #else |
| 127 | passwd = spw->sp_pwdp; |
| 128 | #endif /* USE_LIBIAF */ |
| 129 | #endif |
| 130 | |
| 131 | /* check for locked account */ |
| 132 | if (!options.use_pam && passwd && *passwd) { |
| 133 | int locked = 0; |
| 134 | |
| 135 | #ifdef LOCKED_PASSWD_STRING |
| 136 | if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) |
| 137 | locked = 1; |
| 138 | #endif |
| 139 | #ifdef LOCKED_PASSWD_PREFIX |
| 140 | if (strncmp(passwd, LOCKED_PASSWD_PREFIX, |
| 141 | strlen(LOCKED_PASSWD_PREFIX)) == 0) |
| 142 | locked = 1; |
| 143 | #endif |
| 144 | #ifdef LOCKED_PASSWD_SUBSTR |
| 145 | if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) |
| 146 | locked = 1; |
| 147 | #endif |
| 148 | #ifdef USE_LIBIAF |
| 149 | free((void *) passwd); |
| 150 | #endif /* USE_LIBIAF */ |
| 151 | if (locked) { |
| 152 | logit("User %.100s not allowed because account is locked", |
| 153 | pw->pw_name); |
| 154 | return 0; |
| 155 | } |
| 156 | } |
| 157 | |
| 158 | /* |
| 159 | * Deny if shell does not exist or is not executable unless we |
| 160 | * are chrooting. |
| 161 | */ |
| 162 | if (options.chroot_directory == NULL || |
| 163 | strcasecmp(options.chroot_directory, "none") == 0) { |
| 164 | char *shell = xstrdup((pw->pw_shell[0] == '\0') ? |
| 165 | _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ |
| 166 | |
| 167 | if (stat(shell, &st) != 0) { |
| 168 | logit("User %.100s not allowed because shell %.100s " |
| 169 | "does not exist", pw->pw_name, shell); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 170 | free(shell); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 171 | return 0; |
| 172 | } |
| 173 | if (S_ISREG(st.st_mode) == 0 || |
| 174 | (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { |
| 175 | logit("User %.100s not allowed because shell %.100s " |
| 176 | "is not executable", pw->pw_name, shell); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 177 | free(shell); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 178 | return 0; |
| 179 | } |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 180 | free(shell); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 181 | } |
| 182 | |
| 183 | if (options.num_deny_users > 0 || options.num_allow_users > 0 || |
| 184 | options.num_deny_groups > 0 || options.num_allow_groups > 0) { |
| 185 | hostname = get_canonical_hostname(options.use_dns); |
| 186 | ipaddr = get_remote_ipaddr(); |
| 187 | } |
| 188 | |
| 189 | /* Return false if user is listed in DenyUsers */ |
| 190 | if (options.num_deny_users > 0) { |
| 191 | for (i = 0; i < options.num_deny_users; i++) |
| 192 | if (match_user(pw->pw_name, hostname, ipaddr, |
| 193 | options.deny_users[i])) { |
| 194 | logit("User %.100s from %.100s not allowed " |
| 195 | "because listed in DenyUsers", |
| 196 | pw->pw_name, hostname); |
| 197 | return 0; |
| 198 | } |
| 199 | } |
| 200 | /* Return false if AllowUsers isn't empty and user isn't listed there */ |
| 201 | if (options.num_allow_users > 0) { |
| 202 | for (i = 0; i < options.num_allow_users; i++) |
| 203 | if (match_user(pw->pw_name, hostname, ipaddr, |
| 204 | options.allow_users[i])) |
| 205 | break; |
| 206 | /* i < options.num_allow_users iff we break for loop */ |
| 207 | if (i >= options.num_allow_users) { |
| 208 | logit("User %.100s from %.100s not allowed because " |
| 209 | "not listed in AllowUsers", pw->pw_name, hostname); |
| 210 | return 0; |
| 211 | } |
| 212 | } |
| 213 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { |
| 214 | /* Get the user's group access list (primary and supplementary) */ |
| 215 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) { |
| 216 | logit("User %.100s from %.100s not allowed because " |
| 217 | "not in any group", pw->pw_name, hostname); |
| 218 | return 0; |
| 219 | } |
| 220 | |
| 221 | /* Return false if one of user's groups is listed in DenyGroups */ |
| 222 | if (options.num_deny_groups > 0) |
| 223 | if (ga_match(options.deny_groups, |
| 224 | options.num_deny_groups)) { |
| 225 | ga_free(); |
| 226 | logit("User %.100s from %.100s not allowed " |
| 227 | "because a group is listed in DenyGroups", |
| 228 | pw->pw_name, hostname); |
| 229 | return 0; |
| 230 | } |
| 231 | /* |
| 232 | * Return false if AllowGroups isn't empty and one of user's groups |
| 233 | * isn't listed there |
| 234 | */ |
| 235 | if (options.num_allow_groups > 0) |
| 236 | if (!ga_match(options.allow_groups, |
| 237 | options.num_allow_groups)) { |
| 238 | ga_free(); |
| 239 | logit("User %.100s from %.100s not allowed " |
| 240 | "because none of user's groups are listed " |
| 241 | "in AllowGroups", pw->pw_name, hostname); |
| 242 | return 0; |
| 243 | } |
| 244 | ga_free(); |
| 245 | } |
| 246 | |
| 247 | #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER |
| 248 | if (!sys_auth_allowed_user(pw, &loginmsg)) |
| 249 | return 0; |
| 250 | #endif |
| 251 | |
| 252 | /* We found no reason not to let this user try to log on... */ |
| 253 | return 1; |
| 254 | } |
| 255 | |
| 256 | void |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 257 | auth_info(Authctxt *authctxt, const char *fmt, ...) |
| 258 | { |
| 259 | va_list ap; |
| 260 | int i; |
| 261 | |
| 262 | free(authctxt->info); |
| 263 | authctxt->info = NULL; |
| 264 | |
| 265 | va_start(ap, fmt); |
| 266 | i = vasprintf(&authctxt->info, fmt, ap); |
| 267 | va_end(ap); |
| 268 | |
| 269 | if (i < 0 || authctxt->info == NULL) |
| 270 | fatal("vasprintf failed"); |
| 271 | } |
| 272 | |
| 273 | void |
| 274 | auth_log(Authctxt *authctxt, int authenticated, int partial, |
| 275 | const char *method, const char *submethod) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 276 | { |
| 277 | void (*authlog) (const char *fmt,...) = verbose; |
| 278 | char *authmsg; |
| 279 | |
| 280 | if (use_privsep && !mm_is_monitor() && !authctxt->postponed) |
| 281 | return; |
| 282 | |
| 283 | /* Raise logging level */ |
| 284 | if (authenticated == 1 || |
| 285 | !authctxt->valid || |
| 286 | authctxt->failures >= options.max_authtries / 2 || |
| 287 | strcmp(method, "password") == 0) |
| 288 | authlog = logit; |
| 289 | |
| 290 | if (authctxt->postponed) |
| 291 | authmsg = "Postponed"; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 292 | else if (partial) |
| 293 | authmsg = "Partial"; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 294 | else |
| 295 | authmsg = authenticated ? "Accepted" : "Failed"; |
| 296 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 297 | authlog("%s %s%s%s for %s%.100s from %.200s port %d %s%s%s", |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 298 | authmsg, |
| 299 | method, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 300 | submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 301 | authctxt->valid ? "" : "invalid user ", |
| 302 | authctxt->user, |
| 303 | get_remote_ipaddr(), |
| 304 | get_remote_port(), |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 305 | compat20 ? "ssh2" : "ssh1", |
| 306 | authctxt->info != NULL ? ": " : "", |
| 307 | authctxt->info != NULL ? authctxt->info : ""); |
| 308 | free(authctxt->info); |
| 309 | authctxt->info = NULL; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 310 | |
| 311 | #ifdef CUSTOM_FAILED_LOGIN |
| 312 | if (authenticated == 0 && !authctxt->postponed && |
| 313 | (strcmp(method, "password") == 0 || |
| 314 | strncmp(method, "keyboard-interactive", 20) == 0 || |
| 315 | strcmp(method, "challenge-response") == 0)) |
| 316 | record_failed_login(authctxt->user, |
| 317 | get_canonical_hostname(options.use_dns), "ssh"); |
| 318 | # ifdef WITH_AIXAUTHENTICATE |
| 319 | if (authenticated) |
| 320 | sys_auth_record_login(authctxt->user, |
| 321 | get_canonical_hostname(options.use_dns), "ssh", &loginmsg); |
| 322 | # endif |
| 323 | #endif |
| 324 | #ifdef SSH_AUDIT_EVENTS |
| 325 | if (authenticated == 0 && !authctxt->postponed) |
| 326 | audit_event(audit_classify_auth(method)); |
| 327 | #endif |
| 328 | } |
| 329 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 330 | |
| 331 | void |
| 332 | auth_maxtries_exceeded(Authctxt *authctxt) |
| 333 | { |
| 334 | error("maximum authentication attempts exceeded for " |
| 335 | "%s%.100s from %.200s port %d %s", |
| 336 | authctxt->valid ? "" : "invalid user ", |
| 337 | authctxt->user, |
| 338 | get_remote_ipaddr(), |
| 339 | get_remote_port(), |
| 340 | compat20 ? "ssh2" : "ssh1"); |
| 341 | packet_disconnect("Too many authentication failures"); |
| 342 | /* NOTREACHED */ |
| 343 | } |
| 344 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 345 | /* |
| 346 | * Check whether root logins are disallowed. |
| 347 | */ |
| 348 | int |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 349 | auth_root_allowed(const char *method) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 350 | { |
| 351 | switch (options.permit_root_login) { |
| 352 | case PERMIT_YES: |
| 353 | return 1; |
| 354 | case PERMIT_NO_PASSWD: |
| 355 | if (strcmp(method, "password") != 0) |
| 356 | return 1; |
| 357 | break; |
| 358 | case PERMIT_FORCED_ONLY: |
| 359 | if (forced_command) { |
| 360 | logit("Root login accepted for forced command."); |
| 361 | return 1; |
| 362 | } |
| 363 | break; |
| 364 | } |
| 365 | logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); |
| 366 | return 0; |
| 367 | } |
| 368 | |
| 369 | |
| 370 | /* |
| 371 | * Given a template and a passwd structure, build a filename |
| 372 | * by substituting % tokenised options. Currently, %% becomes '%', |
| 373 | * %h becomes the home directory and %u the username. |
| 374 | * |
| 375 | * This returns a buffer allocated by xmalloc. |
| 376 | */ |
| 377 | char * |
| 378 | expand_authorized_keys(const char *filename, struct passwd *pw) |
| 379 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 380 | char *file, ret[PATH_MAX]; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 381 | int i; |
| 382 | |
| 383 | file = percent_expand(filename, "h", pw->pw_dir, |
| 384 | "u", pw->pw_name, (char *)NULL); |
| 385 | |
| 386 | /* |
| 387 | * Ensure that filename starts anchored. If not, be backward |
| 388 | * compatible and prepend the '%h/' |
| 389 | */ |
| 390 | if (*file == '/') |
| 391 | return (file); |
| 392 | |
| 393 | i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); |
| 394 | if (i < 0 || (size_t)i >= sizeof(ret)) |
| 395 | fatal("expand_authorized_keys: path too long"); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 396 | free(file); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 397 | return (xstrdup(ret)); |
| 398 | } |
| 399 | |
| 400 | char * |
| 401 | authorized_principals_file(struct passwd *pw) |
| 402 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 403 | if (options.authorized_principals_file == NULL || |
| 404 | strcasecmp(options.authorized_principals_file, "none") == 0) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 405 | return NULL; |
| 406 | return expand_authorized_keys(options.authorized_principals_file, pw); |
| 407 | } |
| 408 | |
| 409 | /* return ok if key exists in sysfile or userfile */ |
| 410 | HostStatus |
| 411 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, |
| 412 | const char *sysfile, const char *userfile) |
| 413 | { |
| 414 | char *user_hostfile; |
| 415 | struct stat st; |
| 416 | HostStatus host_status; |
| 417 | struct hostkeys *hostkeys; |
| 418 | const struct hostkey_entry *found; |
| 419 | |
| 420 | hostkeys = init_hostkeys(); |
| 421 | load_hostkeys(hostkeys, host, sysfile); |
| 422 | if (userfile != NULL) { |
| 423 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); |
| 424 | if (options.strict_modes && |
| 425 | (stat(user_hostfile, &st) == 0) && |
| 426 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || |
| 427 | (st.st_mode & 022) != 0)) { |
| 428 | logit("Authentication refused for %.100s: " |
| 429 | "bad owner or modes for %.200s", |
| 430 | pw->pw_name, user_hostfile); |
| 431 | auth_debug_add("Ignored %.200s: bad ownership or modes", |
| 432 | user_hostfile); |
| 433 | } else { |
| 434 | temporarily_use_uid(pw); |
| 435 | load_hostkeys(hostkeys, host, user_hostfile); |
| 436 | restore_uid(); |
| 437 | } |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 438 | free(user_hostfile); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 439 | } |
| 440 | host_status = check_key_in_hostkeys(hostkeys, key, &found); |
| 441 | if (host_status == HOST_REVOKED) |
| 442 | error("WARNING: revoked key for %s attempted authentication", |
| 443 | found->host); |
| 444 | else if (host_status == HOST_OK) |
| 445 | debug("%s: key for %s found at %s:%ld", __func__, |
| 446 | found->host, found->file, found->line); |
| 447 | else |
| 448 | debug("%s: key for host %s not found", __func__, host); |
| 449 | |
| 450 | free_hostkeys(hostkeys); |
| 451 | |
| 452 | return host_status; |
| 453 | } |
| 454 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 455 | /* |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 456 | * Check a given path for security. This is defined as all components |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 457 | * of the path to the file must be owned by either the owner of |
| 458 | * of the file or root and no directories must be group or world writable. |
| 459 | * |
| 460 | * XXX Should any specific check be done for sym links ? |
| 461 | * |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 462 | * Takes a file name, its stat information (preferably from fstat() to |
| 463 | * avoid races), the uid of the expected owner, their home directory and an |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 464 | * error buffer plus max size as arguments. |
| 465 | * |
| 466 | * Returns 0 on success and -1 on failure |
| 467 | */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 468 | int |
| 469 | auth_secure_path(const char *name, struct stat *stp, const char *pw_dir, |
| 470 | uid_t uid, char *err, size_t errlen) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 471 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 472 | char buf[PATH_MAX], homedir[PATH_MAX]; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 473 | char *cp; |
| 474 | int comparehome = 0; |
| 475 | struct stat st; |
| 476 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 477 | if (realpath(name, buf) == NULL) { |
| 478 | snprintf(err, errlen, "realpath %s failed: %s", name, |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 479 | strerror(errno)); |
| 480 | return -1; |
| 481 | } |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 482 | if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 483 | comparehome = 1; |
| 484 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 485 | if (!S_ISREG(stp->st_mode)) { |
| 486 | snprintf(err, errlen, "%s is not a regular file", buf); |
| 487 | return -1; |
| 488 | } |
| 489 | if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) || |
| 490 | (stp->st_mode & 022) != 0) { |
| 491 | #if defined(ANDROID) |
| 492 | /* needed to allow root login on Android. */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 493 | if (getuid() != 0) |
| 494 | #endif |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 495 | { |
| 496 | snprintf(err, errlen, "bad ownership or modes for file %s", |
| 497 | buf); |
| 498 | return -1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 499 | } |
| 500 | } |
| 501 | |
| 502 | /* for each component of the canonical path, walking upwards */ |
| 503 | for (;;) { |
| 504 | if ((cp = dirname(buf)) == NULL) { |
| 505 | snprintf(err, errlen, "dirname() failed"); |
| 506 | return -1; |
| 507 | } |
| 508 | strlcpy(buf, cp, sizeof(buf)); |
| 509 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 510 | #if !defined(ANDROID) |
| 511 | /* /data is owned by system user, which causes this check to fail */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 512 | if (stat(buf, &st) < 0 || |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 513 | (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) || |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 514 | (st.st_mode & 022) != 0) { |
| 515 | snprintf(err, errlen, |
| 516 | "bad ownership or modes for directory %s", buf); |
| 517 | return -1; |
| 518 | } |
| 519 | #endif |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 520 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 521 | /* If are past the homedir then we can stop */ |
| 522 | if (comparehome && strcmp(homedir, buf) == 0) |
| 523 | break; |
| 524 | |
| 525 | /* |
| 526 | * dirname should always complete with a "/" path, |
| 527 | * but we can be paranoid and check for "." too |
| 528 | */ |
| 529 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) |
| 530 | break; |
| 531 | } |
| 532 | return 0; |
| 533 | } |
| 534 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 535 | /* |
| 536 | * Version of secure_path() that accepts an open file descriptor to |
| 537 | * avoid races. |
| 538 | * |
| 539 | * Returns 0 on success and -1 on failure |
| 540 | */ |
| 541 | static int |
| 542 | secure_filename(FILE *f, const char *file, struct passwd *pw, |
| 543 | char *err, size_t errlen) |
| 544 | { |
| 545 | struct stat st; |
| 546 | |
| 547 | /* check the open file to avoid races */ |
| 548 | if (fstat(fileno(f), &st) < 0) { |
| 549 | snprintf(err, errlen, "cannot stat file %s: %s", |
| 550 | file, strerror(errno)); |
| 551 | return -1; |
| 552 | } |
| 553 | return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen); |
| 554 | } |
| 555 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 556 | static FILE * |
| 557 | auth_openfile(const char *file, struct passwd *pw, int strict_modes, |
| 558 | int log_missing, char *file_type) |
| 559 | { |
| 560 | char line[1024]; |
| 561 | struct stat st; |
| 562 | int fd; |
| 563 | FILE *f; |
| 564 | |
| 565 | if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { |
| 566 | if (log_missing || errno != ENOENT) |
| 567 | debug("Could not open %s '%s': %s", file_type, file, |
| 568 | strerror(errno)); |
| 569 | return NULL; |
| 570 | } |
| 571 | |
| 572 | if (fstat(fd, &st) < 0) { |
| 573 | close(fd); |
| 574 | return NULL; |
| 575 | } |
| 576 | if (!S_ISREG(st.st_mode)) { |
| 577 | logit("User %s %s %s is not a regular file", |
| 578 | pw->pw_name, file_type, file); |
| 579 | close(fd); |
| 580 | return NULL; |
| 581 | } |
| 582 | unset_nonblock(fd); |
| 583 | if ((f = fdopen(fd, "r")) == NULL) { |
| 584 | close(fd); |
| 585 | return NULL; |
| 586 | } |
| 587 | if (strict_modes && |
| 588 | secure_filename(f, file, pw, line, sizeof(line)) != 0) { |
| 589 | fclose(f); |
| 590 | logit("Authentication refused: %s", line); |
| 591 | auth_debug_add("Ignored %s: %s", file_type, line); |
| 592 | return NULL; |
| 593 | } |
| 594 | |
| 595 | return f; |
| 596 | } |
| 597 | |
| 598 | |
| 599 | FILE * |
| 600 | auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) |
| 601 | { |
| 602 | return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); |
| 603 | } |
| 604 | |
| 605 | FILE * |
| 606 | auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) |
| 607 | { |
| 608 | return auth_openfile(file, pw, strict_modes, 0, |
| 609 | "authorized principals"); |
| 610 | } |
| 611 | |
| 612 | struct passwd * |
| 613 | getpwnamallow(const char *user) |
| 614 | { |
| 615 | #ifdef HAVE_LOGIN_CAP |
| 616 | extern login_cap_t *lc; |
| 617 | #ifdef BSD_AUTH |
| 618 | auth_session_t *as; |
| 619 | #endif |
| 620 | #endif |
| 621 | struct passwd *pw; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 622 | struct connection_info *ci = get_connection_info(1, options.use_dns); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 623 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 624 | ci->user = user; |
| 625 | parse_server_match_config(&options, ci); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 626 | |
| 627 | #if defined(_AIX) && defined(HAVE_SETAUTHDB) |
| 628 | aix_setauthdb(user); |
| 629 | #endif |
| 630 | |
| 631 | pw = getpwnam(user); |
| 632 | |
| 633 | #if defined(_AIX) && defined(HAVE_SETAUTHDB) |
| 634 | aix_restoreauthdb(); |
| 635 | #endif |
| 636 | #ifdef HAVE_CYGWIN |
| 637 | /* |
| 638 | * Windows usernames are case-insensitive. To avoid later problems |
| 639 | * when trying to match the username, the user is only allowed to |
| 640 | * login if the username is given in the same case as stored in the |
| 641 | * user database. |
| 642 | */ |
| 643 | if (pw != NULL && strcmp(user, pw->pw_name) != 0) { |
| 644 | logit("Login name %.100s does not match stored username %.100s", |
| 645 | user, pw->pw_name); |
| 646 | pw = NULL; |
| 647 | } |
| 648 | #endif |
| 649 | if (pw == NULL) { |
| 650 | logit("Invalid user %.100s from %.100s", |
| 651 | user, get_remote_ipaddr()); |
| 652 | #ifdef CUSTOM_FAILED_LOGIN |
| 653 | record_failed_login(user, |
| 654 | get_canonical_hostname(options.use_dns), "ssh"); |
| 655 | #endif |
| 656 | #ifdef SSH_AUDIT_EVENTS |
| 657 | audit_event(SSH_INVALID_USER); |
| 658 | #endif /* SSH_AUDIT_EVENTS */ |
| 659 | return (NULL); |
| 660 | } |
| 661 | if (!allowed_user(pw)) |
| 662 | return (NULL); |
| 663 | #ifdef HAVE_LOGIN_CAP |
| 664 | if ((lc = login_getclass(pw->pw_class)) == NULL) { |
| 665 | debug("unable to get login class: %s", user); |
| 666 | return (NULL); |
| 667 | } |
| 668 | #ifdef BSD_AUTH |
| 669 | if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || |
| 670 | auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { |
| 671 | debug("Approval failure for %s", user); |
| 672 | pw = NULL; |
| 673 | } |
| 674 | if (as != NULL) |
| 675 | auth_close(as); |
| 676 | #endif |
| 677 | #endif |
| 678 | if (pw != NULL) |
| 679 | return (pwcopy(pw)); |
| 680 | return (NULL); |
| 681 | } |
| 682 | |
| 683 | /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ |
| 684 | int |
| 685 | auth_key_is_revoked(Key *key) |
| 686 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 687 | char *fp = NULL; |
| 688 | int r; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 689 | |
| 690 | if (options.revoked_keys_file == NULL) |
| 691 | return 0; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 692 | if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, |
| 693 | SSH_FP_DEFAULT)) == NULL) { |
| 694 | r = SSH_ERR_ALLOC_FAIL; |
| 695 | error("%s: fingerprint key: %s", __func__, ssh_err(r)); |
| 696 | goto out; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 697 | } |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 698 | |
| 699 | r = sshkey_check_revoked(key, options.revoked_keys_file); |
| 700 | switch (r) { |
| 701 | case 0: |
| 702 | break; /* not revoked */ |
| 703 | case SSH_ERR_KEY_REVOKED: |
| 704 | error("Authentication key %s %s revoked by file %s", |
| 705 | sshkey_type(key), fp, options.revoked_keys_file); |
| 706 | goto out; |
| 707 | default: |
| 708 | error("Error checking authentication key %s %s in " |
| 709 | "revoked keys file %s: %s", sshkey_type(key), fp, |
| 710 | options.revoked_keys_file, ssh_err(r)); |
| 711 | goto out; |
| 712 | } |
| 713 | |
| 714 | /* Success */ |
| 715 | r = 0; |
| 716 | |
| 717 | out: |
| 718 | free(fp); |
| 719 | return r == 0 ? 0 : 1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 720 | } |
| 721 | |
| 722 | void |
| 723 | auth_debug_add(const char *fmt,...) |
| 724 | { |
| 725 | char buf[1024]; |
| 726 | va_list args; |
| 727 | |
| 728 | if (!auth_debug_init) |
| 729 | return; |
| 730 | |
| 731 | va_start(args, fmt); |
| 732 | vsnprintf(buf, sizeof(buf), fmt, args); |
| 733 | va_end(args); |
| 734 | buffer_put_cstring(&auth_debug, buf); |
| 735 | } |
| 736 | |
| 737 | void |
| 738 | auth_debug_send(void) |
| 739 | { |
| 740 | char *msg; |
| 741 | |
| 742 | if (!auth_debug_init) |
| 743 | return; |
| 744 | while (buffer_len(&auth_debug)) { |
| 745 | msg = buffer_get_string(&auth_debug, NULL); |
| 746 | packet_send_debug("%s", msg); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 747 | free(msg); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 748 | } |
| 749 | } |
| 750 | |
| 751 | void |
| 752 | auth_debug_reset(void) |
| 753 | { |
| 754 | if (auth_debug_init) |
| 755 | buffer_clear(&auth_debug); |
| 756 | else { |
| 757 | buffer_init(&auth_debug); |
| 758 | auth_debug_init = 1; |
| 759 | } |
| 760 | } |
| 761 | |
| 762 | struct passwd * |
| 763 | fakepw(void) |
| 764 | { |
| 765 | static struct passwd fake; |
| 766 | |
| 767 | memset(&fake, 0, sizeof(fake)); |
| 768 | fake.pw_name = "NOUSER"; |
| 769 | fake.pw_passwd = |
| 770 | "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 771 | #ifdef HAVE_STRUCT_PASSWD_PW_GECOS |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 772 | fake.pw_gecos = "NOUSER"; |
| 773 | #endif |
| 774 | fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; |
| 775 | fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 776 | #ifdef HAVE_STRUCT_PASSWD_PW_CLASS |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 777 | fake.pw_class = ""; |
| 778 | #endif |
| 779 | fake.pw_dir = "/nonexist"; |
| 780 | fake.pw_shell = "/nonexist"; |
| 781 | |
| 782 | return (&fake); |
| 783 | } |