Annotation of src/usr.bin/ssh/auth.c, Revision 1.86
1.86 ! djm 1: /* $OpenBSD: auth.c,v 1.85 2010/03/04 10:36:03 djm Exp $ */
1.1 markus 2: /*
1.19 deraadt 3: * Copyright (c) 2000 Markus Friedl. All rights reserved.
1.9 deraadt 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.
1.1 markus 24: */
25:
1.62 stevesk 26: #include <sys/types.h>
27: #include <sys/stat.h>
1.73 stevesk 28: #include <sys/param.h>
1.22 markus 29:
1.70 stevesk 30: #include <errno.h>
1.79 dtucker 31: #include <fcntl.h>
1.22 markus 32: #include <libgen.h>
1.77 djm 33: #include <login_cap.h>
1.61 stevesk 34: #include <paths.h>
1.68 stevesk 35: #include <pwd.h>
1.69 stevesk 36: #include <stdarg.h>
1.74 stevesk 37: #include <stdio.h>
1.72 stevesk 38: #include <string.h>
1.80 djm 39: #include <unistd.h>
1.1 markus 40:
41: #include "xmalloc.h"
1.13 markus 42: #include "match.h"
1.14 markus 43: #include "groupaccess.h"
44: #include "log.h"
1.75 deraadt 45: #include "buffer.h"
1.1 markus 46: #include "servconf.h"
1.75 deraadt 47: #include "key.h"
48: #include "hostfile.h"
1.2 markus 49: #include "auth.h"
1.13 markus 50: #include "auth-options.h"
1.14 markus 51: #include "canohost.h"
1.24 markus 52: #include "uidswap.h"
1.40 markus 53: #include "misc.h"
1.42 markus 54: #include "packet.h"
1.75 deraadt 55: #ifdef GSSAPI
56: #include "ssh-gss.h"
57: #endif
1.85 djm 58: #include "authfile.h"
1.67 dtucker 59: #include "monitor_wrap.h"
1.2 markus 60:
1.1 markus 61: /* import */
62: extern ServerOptions options;
1.67 dtucker 63: extern int use_privsep;
1.1 markus 64:
1.42 markus 65: /* Debugging messages */
66: Buffer auth_debug;
67: int auth_debug_init;
68:
1.1 markus 69: /*
1.12 markus 70: * Check if the user is allowed to log in via ssh. If user is listed
71: * in DenyUsers or one of user's groups is listed in DenyGroups, false
72: * will be returned. If AllowUsers isn't empty and user isn't listed
73: * there, or if AllowGroups isn't empty and one of user's groups isn't
74: * listed there, false will be returned.
1.1 markus 75: * If the user's shell is not executable, false will be returned.
1.4 markus 76: * Otherwise true is returned.
1.1 markus 77: */
1.5 markus 78: int
1.1 markus 79: allowed_user(struct passwd * pw)
80: {
81: struct stat st;
1.35 markus 82: const char *hostname = NULL, *ipaddr = NULL;
1.60 djm 83: u_int i;
1.1 markus 84:
85: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 86: if (!pw || !pw->pw_name)
1.1 markus 87: return 0;
88:
1.7 deraadt 89: /*
1.84 djm 90: * Deny if shell does not exist or is not executable unless we
91: * are chrooting.
1.7 deraadt 92: */
1.84 djm 93: if (options.chroot_directory == NULL ||
94: strcasecmp(options.chroot_directory, "none") == 0) {
95: char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
96: _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
97:
98: if (stat(shell, &st) != 0) {
99: logit("User %.100s not allowed because shell %.100s "
100: "does not exist", pw->pw_name, shell);
101: xfree(shell);
102: return 0;
103: }
104: if (S_ISREG(st.st_mode) == 0 ||
105: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
106: logit("User %.100s not allowed because shell %.100s "
107: "is not executable", pw->pw_name, shell);
108: xfree(shell);
109: return 0;
110: }
1.83 djm 111: xfree(shell);
1.34 stevesk 112: }
1.1 markus 113:
1.58 dtucker 114: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
115: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 116: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 117: ipaddr = get_remote_ipaddr();
118: }
119:
1.1 markus 120: /* Return false if user is listed in DenyUsers */
121: if (options.num_deny_users > 0) {
122: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 123: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 124: options.deny_users[i])) {
1.57 dtucker 125: logit("User %.100s from %.100s not allowed "
126: "because listed in DenyUsers",
127: pw->pw_name, hostname);
1.1 markus 128: return 0;
1.34 stevesk 129: }
1.1 markus 130: }
131: /* Return false if AllowUsers isn't empty and user isn't listed there */
132: if (options.num_allow_users > 0) {
133: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 134: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 135: options.allow_users[i]))
1.1 markus 136: break;
137: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 138: if (i >= options.num_allow_users) {
1.57 dtucker 139: logit("User %.100s from %.100s not allowed because "
140: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 141: return 0;
1.34 stevesk 142: }
1.1 markus 143: }
144: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 145: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 146: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 147: logit("User %.100s from %.100s not allowed because "
148: "not in any group", pw->pw_name, hostname);
1.1 markus 149: return 0;
1.34 stevesk 150: }
1.1 markus 151:
1.12 markus 152: /* Return false if one of user's groups is listed in DenyGroups */
153: if (options.num_deny_groups > 0)
154: if (ga_match(options.deny_groups,
155: options.num_deny_groups)) {
156: ga_free();
1.57 dtucker 157: logit("User %.100s from %.100s not allowed "
158: "because a group is listed in DenyGroups",
159: pw->pw_name, hostname);
1.1 markus 160: return 0;
1.12 markus 161: }
1.1 markus 162: /*
1.12 markus 163: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 164: * isn't listed there
165: */
1.12 markus 166: if (options.num_allow_groups > 0)
167: if (!ga_match(options.allow_groups,
168: options.num_allow_groups)) {
169: ga_free();
1.57 dtucker 170: logit("User %.100s from %.100s not allowed "
171: "because none of user's groups are listed "
172: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 173: return 0;
1.12 markus 174: }
175: ga_free();
1.1 markus 176: }
177: /* We found no reason not to let this user try to log on... */
178: return 1;
1.13 markus 179: }
180:
181: void
182: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
183: {
184: void (*authlog) (const char *fmt,...) = verbose;
185: char *authmsg;
1.67 dtucker 186:
187: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
188: return;
1.13 markus 189:
190: /* Raise logging level */
191: if (authenticated == 1 ||
192: !authctxt->valid ||
1.54 dtucker 193: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 194: strcmp(method, "password") == 0)
1.47 itojun 195: authlog = logit;
1.13 markus 196:
197: if (authctxt->postponed)
198: authmsg = "Postponed";
199: else
200: authmsg = authenticated ? "Accepted" : "Failed";
201:
202: authlog("%s %s for %s%.100s from %.200s port %d%s",
203: authmsg,
204: method,
1.56 markus 205: authctxt->valid ? "" : "invalid user ",
1.29 markus 206: authctxt->user,
1.13 markus 207: get_remote_ipaddr(),
208: get_remote_port(),
209: info);
210: }
211:
212: /*
1.17 markus 213: * Check whether root logins are disallowed.
1.13 markus 214: */
215: int
1.17 markus 216: auth_root_allowed(char *method)
1.13 markus 217: {
1.17 markus 218: switch (options.permit_root_login) {
219: case PERMIT_YES:
1.13 markus 220: return 1;
1.17 markus 221: case PERMIT_NO_PASSWD:
222: if (strcmp(method, "password") != 0)
223: return 1;
224: break;
225: case PERMIT_FORCED_ONLY:
226: if (forced_command) {
1.47 itojun 227: logit("Root login accepted for forced command.");
1.17 markus 228: return 1;
229: }
230: break;
1.13 markus 231: }
1.47 itojun 232: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 233: return 0;
234: }
235:
236:
237: /*
238: * Given a template and a passwd structure, build a filename
239: * by substituting % tokenised options. Currently, %% becomes '%',
240: * %h becomes the home directory and %u the username.
241: *
242: * This returns a buffer allocated by xmalloc.
243: */
1.59 djm 244: static char *
245: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 246: {
1.65 djm 247: char *file, ret[MAXPATHLEN];
248: int i;
1.22 markus 249:
1.59 djm 250: file = percent_expand(filename, "h", pw->pw_dir,
251: "u", pw->pw_name, (char *)NULL);
1.22 markus 252:
253: /*
254: * Ensure that filename starts anchored. If not, be backward
255: * compatible and prepend the '%h/'
256: */
1.59 djm 257: if (*file == '/')
258: return (file);
259:
1.65 djm 260: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
261: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 262: fatal("expand_authorized_keys: path too long");
263: xfree(file);
1.65 djm 264: return (xstrdup(ret));
1.22 markus 265: }
266:
267: char *
268: authorized_keys_file(struct passwd *pw)
269: {
1.59 djm 270: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 271: }
272:
273: char *
274: authorized_keys_file2(struct passwd *pw)
275: {
1.59 djm 276: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 277: }
1.24 markus 278:
279: /* return ok if key exists in sysfile or userfile */
280: HostStatus
281: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
282: const char *sysfile, const char *userfile)
283: {
284: Key *found;
285: char *user_hostfile;
286: struct stat st;
1.30 stevesk 287: HostStatus host_status;
1.24 markus 288:
289: /* Check if we know the host and its host key. */
290: found = key_new(key->type);
291: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
292:
293: if (host_status != HOST_OK && userfile != NULL) {
294: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
295: if (options.strict_modes &&
296: (stat(user_hostfile, &st) == 0) &&
297: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 298: (st.st_mode & 022) != 0)) {
1.47 itojun 299: logit("Authentication refused for %.100s: "
1.24 markus 300: "bad owner or modes for %.200s",
301: pw->pw_name, user_hostfile);
302: } else {
303: temporarily_use_uid(pw);
304: host_status = check_host_in_hostfile(user_hostfile,
305: host, key, found, NULL);
306: restore_uid();
307: }
308: xfree(user_hostfile);
309: }
310: key_free(found);
311:
312: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
313: "ok" : "not found", host);
314: return host_status;
315: }
316:
1.22 markus 317:
318: /*
319: * Check a given file for security. This is defined as all components
1.44 stevesk 320: * of the path to the file must be owned by either the owner of
1.23 markus 321: * of the file or root and no directories must be group or world writable.
1.22 markus 322: *
323: * XXX Should any specific check be done for sym links ?
324: *
325: * Takes an open file descriptor, the file name, a uid and and
326: * error buffer plus max size as arguments.
327: *
328: * Returns 0 on success and -1 on failure
329: */
1.79 dtucker 330: static int
1.25 provos 331: secure_filename(FILE *f, const char *file, struct passwd *pw,
332: char *err, size_t errlen)
1.22 markus 333: {
1.25 provos 334: uid_t uid = pw->pw_uid;
1.28 markus 335: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 336: char *cp;
1.46 markus 337: int comparehome = 0;
1.22 markus 338: struct stat st;
339:
340: if (realpath(file, buf) == NULL) {
341: snprintf(err, errlen, "realpath %s failed: %s", file,
342: strerror(errno));
343: return -1;
344: }
1.46 markus 345: if (realpath(pw->pw_dir, homedir) != NULL)
346: comparehome = 1;
1.22 markus 347:
348: /* check the open file to avoid races */
349: if (fstat(fileno(f), &st) < 0 ||
350: (st.st_uid != 0 && st.st_uid != uid) ||
351: (st.st_mode & 022) != 0) {
352: snprintf(err, errlen, "bad ownership or modes for file %s",
353: buf);
354: return -1;
355: }
356:
357: /* for each component of the canonical path, walking upwards */
358: for (;;) {
359: if ((cp = dirname(buf)) == NULL) {
360: snprintf(err, errlen, "dirname() failed");
361: return -1;
362: }
363: strlcpy(buf, cp, sizeof(buf));
1.25 provos 364:
1.22 markus 365: debug3("secure_filename: checking '%s'", buf);
366: if (stat(buf, &st) < 0 ||
367: (st.st_uid != 0 && st.st_uid != uid) ||
368: (st.st_mode & 022) != 0) {
1.31 deraadt 369: snprintf(err, errlen,
1.22 markus 370: "bad ownership or modes for directory %s", buf);
371: return -1;
372: }
373:
1.82 dtucker 374: /* If are past the homedir then we can stop */
1.46 markus 375: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 376: debug3("secure_filename: terminating check at '%s'",
377: buf);
378: break;
379: }
1.22 markus 380: /*
381: * dirname should always complete with a "/" path,
382: * but we can be paranoid and check for "." too
383: */
384: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
385: break;
386: }
1.17 markus 387: return 0;
1.79 dtucker 388: }
389:
390: FILE *
391: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
392: {
393: char line[1024];
394: struct stat st;
395: int fd;
396: FILE *f;
397:
398: /*
399: * Open the file containing the authorized keys
400: * Fail quietly if file does not exist
401: */
1.81 dtucker 402: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
403: if (errno != ENOENT)
404: debug("Could not open keyfile '%s': %s", file,
405: strerror(errno));
1.79 dtucker 406: return NULL;
1.81 dtucker 407: }
1.79 dtucker 408:
409: if (fstat(fd, &st) < 0) {
410: close(fd);
411: return NULL;
412: }
413: if (!S_ISREG(st.st_mode)) {
414: logit("User %s authorized keys %s is not a regular file",
415: pw->pw_name, file);
416: close(fd);
417: return NULL;
418: }
419: unset_nonblock(fd);
420: if ((f = fdopen(fd, "r")) == NULL) {
421: close(fd);
422: return NULL;
423: }
424: if (options.strict_modes &&
425: secure_filename(f, file, pw, line, sizeof(line)) != 0) {
426: fclose(f);
427: logit("Authentication refused: %s", line);
428: return NULL;
429: }
430:
431: return f;
1.37 provos 432: }
433:
434: struct passwd *
435: getpwnamallow(const char *user)
436: {
1.38 provos 437: extern login_cap_t *lc;
438: auth_session_t *as;
1.37 provos 439: struct passwd *pw;
1.71 dtucker 440:
441: parse_server_match_config(&options, user,
442: get_canonical_hostname(options.use_dns), get_remote_ipaddr());
1.37 provos 443:
444: pw = getpwnam(user);
1.45 stevesk 445: if (pw == NULL) {
1.55 markus 446: logit("Invalid user %.100s from %.100s",
1.45 stevesk 447: user, get_remote_ipaddr());
448: return (NULL);
449: }
450: if (!allowed_user(pw))
1.38 provos 451: return (NULL);
452: if ((lc = login_getclass(pw->pw_class)) == NULL) {
453: debug("unable to get login class: %s", user);
454: return (NULL);
455: }
456: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 457: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 458: debug("Approval failure for %s", user);
1.37 provos 459: pw = NULL;
1.38 provos 460: }
461: if (as != NULL)
462: auth_close(as);
1.41 markus 463: if (pw != NULL)
464: return (pwcopy(pw));
465: return (NULL);
1.85 djm 466: }
467:
468: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
469: int
470: auth_key_is_revoked(Key *key)
471: {
472: char *key_fp;
473:
474: if (options.revoked_keys_file == NULL)
475: return 0;
476:
477: switch (key_in_file(key, options.revoked_keys_file, 0)) {
478: case 0:
479: /* key not revoked */
480: return 0;
481: case -1:
482: /* Error opening revoked_keys_file: refuse all keys */
483: error("Revoked keys file is unreadable: refusing public key "
484: "authentication");
485: return 1;
486: case 1:
487: /* Key revoked */
488: key_fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
1.86 ! djm 489: error("WARNING: authentication attempt with a revoked "
! 490: "%s key %s ", key_type(key), key_fp);
1.85 djm 491: xfree(key_fp);
492: return 1;
493: }
494: fatal("key_in_file returned junk");
1.42 markus 495: }
496:
497: void
498: auth_debug_add(const char *fmt,...)
499: {
500: char buf[1024];
501: va_list args;
502:
503: if (!auth_debug_init)
504: return;
505:
506: va_start(args, fmt);
507: vsnprintf(buf, sizeof(buf), fmt, args);
508: va_end(args);
509: buffer_put_cstring(&auth_debug, buf);
510: }
511:
512: void
513: auth_debug_send(void)
514: {
515: char *msg;
516:
517: if (!auth_debug_init)
518: return;
519: while (buffer_len(&auth_debug)) {
520: msg = buffer_get_string(&auth_debug, NULL);
521: packet_send_debug("%s", msg);
522: xfree(msg);
523: }
524: }
525:
526: void
527: auth_debug_reset(void)
528: {
529: if (auth_debug_init)
530: buffer_clear(&auth_debug);
531: else {
532: buffer_init(&auth_debug);
533: auth_debug_init = 1;
534: }
1.49 markus 535: }
536:
537: struct passwd *
538: fakepw(void)
539: {
540: static struct passwd fake;
541:
542: memset(&fake, 0, sizeof(fake));
543: fake.pw_name = "NOUSER";
544: fake.pw_passwd =
1.51 djm 545: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 546: fake.pw_gecos = "NOUSER";
1.53 deraadt 547: fake.pw_uid = (uid_t)-1;
548: fake.pw_gid = (gid_t)-1;
1.49 markus 549: fake.pw_class = "";
550: fake.pw_dir = "/nonexist";
551: fake.pw_shell = "/nonexist";
552:
553: return (&fake);
1.1 markus 554: }
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