Annotation of src/usr.bin/ssh/auth.c, Revision 1.94
1.94 ! djm 1: /* $OpenBSD: auth.c,v 1.93 2011/05/23 03:30:07 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: */
1.93 djm 244: char *
1.59 djm 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: }
1.24 markus 266:
1.87 djm 267: char *
268: authorized_principals_file(struct passwd *pw)
269: {
270: if (options.authorized_principals_file == NULL)
271: return NULL;
272: return expand_authorized_keys(options.authorized_principals_file, pw);
273: }
274:
1.24 markus 275: /* return ok if key exists in sysfile or userfile */
276: HostStatus
277: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
278: const char *sysfile, const char *userfile)
279: {
280: char *user_hostfile;
281: struct stat st;
1.30 stevesk 282: HostStatus host_status;
1.91 djm 283: struct hostkeys *hostkeys;
284: const struct hostkey_entry *found;
1.24 markus 285:
1.91 djm 286: hostkeys = init_hostkeys();
287: load_hostkeys(hostkeys, host, sysfile);
288: if (userfile != NULL) {
1.24 markus 289: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
290: if (options.strict_modes &&
291: (stat(user_hostfile, &st) == 0) &&
292: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 293: (st.st_mode & 022) != 0)) {
1.47 itojun 294: logit("Authentication refused for %.100s: "
1.24 markus 295: "bad owner or modes for %.200s",
296: pw->pw_name, user_hostfile);
1.88 djm 297: auth_debug_add("Ignored %.200s: bad ownership or modes",
298: user_hostfile);
1.24 markus 299: } else {
300: temporarily_use_uid(pw);
1.91 djm 301: load_hostkeys(hostkeys, host, user_hostfile);
1.24 markus 302: restore_uid();
303: }
304: xfree(user_hostfile);
305: }
1.91 djm 306: host_status = check_key_in_hostkeys(hostkeys, key, &found);
307: if (host_status == HOST_REVOKED)
308: error("WARNING: revoked key for %s attempted authentication",
309: found->host);
310: else if (host_status == HOST_OK)
311: debug("%s: key for %s found at %s:%ld", __func__,
312: found->host, found->file, found->line);
313: else
314: debug("%s: key for host %s not found", __func__, host);
315:
316: free_hostkeys(hostkeys);
1.24 markus 317:
318: return host_status;
319: }
320:
1.22 markus 321:
322: /*
323: * Check a given file for security. This is defined as all components
1.44 stevesk 324: * of the path to the file must be owned by either the owner of
1.23 markus 325: * of the file or root and no directories must be group or world writable.
1.22 markus 326: *
327: * XXX Should any specific check be done for sym links ?
328: *
329: * Takes an open file descriptor, the file name, a uid and and
330: * error buffer plus max size as arguments.
331: *
332: * Returns 0 on success and -1 on failure
333: */
1.79 dtucker 334: static int
1.25 provos 335: secure_filename(FILE *f, const char *file, struct passwd *pw,
336: char *err, size_t errlen)
1.22 markus 337: {
1.25 provos 338: uid_t uid = pw->pw_uid;
1.28 markus 339: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 340: char *cp;
1.46 markus 341: int comparehome = 0;
1.22 markus 342: struct stat st;
343:
344: if (realpath(file, buf) == NULL) {
345: snprintf(err, errlen, "realpath %s failed: %s", file,
346: strerror(errno));
347: return -1;
348: }
1.46 markus 349: if (realpath(pw->pw_dir, homedir) != NULL)
350: comparehome = 1;
1.22 markus 351:
352: /* check the open file to avoid races */
353: if (fstat(fileno(f), &st) < 0 ||
354: (st.st_uid != 0 && st.st_uid != uid) ||
355: (st.st_mode & 022) != 0) {
356: snprintf(err, errlen, "bad ownership or modes for file %s",
357: buf);
358: return -1;
359: }
360:
361: /* for each component of the canonical path, walking upwards */
362: for (;;) {
363: if ((cp = dirname(buf)) == NULL) {
364: snprintf(err, errlen, "dirname() failed");
365: return -1;
366: }
367: strlcpy(buf, cp, sizeof(buf));
1.25 provos 368:
1.22 markus 369: if (stat(buf, &st) < 0 ||
370: (st.st_uid != 0 && st.st_uid != uid) ||
371: (st.st_mode & 022) != 0) {
1.31 deraadt 372: snprintf(err, errlen,
1.22 markus 373: "bad ownership or modes for directory %s", buf);
374: return -1;
375: }
376:
1.82 dtucker 377: /* If are past the homedir then we can stop */
1.94 ! djm 378: if (comparehome && strcmp(homedir, buf) == 0)
1.27 markus 379: break;
1.94 ! djm 380:
1.22 markus 381: /*
382: * dirname should always complete with a "/" path,
383: * but we can be paranoid and check for "." too
384: */
385: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
386: break;
387: }
1.17 markus 388: return 0;
1.79 dtucker 389: }
390:
1.87 djm 391: static FILE *
392: auth_openfile(const char *file, struct passwd *pw, int strict_modes,
393: int log_missing, char *file_type)
1.79 dtucker 394: {
395: char line[1024];
396: struct stat st;
397: int fd;
398: FILE *f;
399:
1.81 dtucker 400: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
1.87 djm 401: if (log_missing || errno != ENOENT)
402: debug("Could not open %s '%s': %s", file_type, file,
1.81 dtucker 403: strerror(errno));
1.79 dtucker 404: return NULL;
1.81 dtucker 405: }
1.79 dtucker 406:
407: if (fstat(fd, &st) < 0) {
408: close(fd);
409: return NULL;
410: }
411: if (!S_ISREG(st.st_mode)) {
1.87 djm 412: logit("User %s %s %s is not a regular file",
413: pw->pw_name, file_type, file);
1.79 dtucker 414: close(fd);
415: return NULL;
416: }
417: unset_nonblock(fd);
418: if ((f = fdopen(fd, "r")) == NULL) {
419: close(fd);
420: return NULL;
421: }
1.90 djm 422: if (strict_modes &&
1.79 dtucker 423: secure_filename(f, file, pw, line, sizeof(line)) != 0) {
424: fclose(f);
425: logit("Authentication refused: %s", line);
1.88 djm 426: auth_debug_add("Ignored %s: %s", file_type, line);
1.79 dtucker 427: return NULL;
428: }
429:
430: return f;
1.87 djm 431: }
432:
433:
434: FILE *
435: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
436: {
437: return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
438: }
439:
440: FILE *
441: auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
442: {
443: return auth_openfile(file, pw, strict_modes, 0,
444: "authorized principals");
1.37 provos 445: }
446:
447: struct passwd *
448: getpwnamallow(const char *user)
449: {
1.38 provos 450: extern login_cap_t *lc;
451: auth_session_t *as;
1.37 provos 452: struct passwd *pw;
1.71 dtucker 453:
454: parse_server_match_config(&options, user,
455: get_canonical_hostname(options.use_dns), get_remote_ipaddr());
1.37 provos 456:
457: pw = getpwnam(user);
1.45 stevesk 458: if (pw == NULL) {
1.55 markus 459: logit("Invalid user %.100s from %.100s",
1.45 stevesk 460: user, get_remote_ipaddr());
461: return (NULL);
462: }
463: if (!allowed_user(pw))
1.38 provos 464: return (NULL);
465: if ((lc = login_getclass(pw->pw_class)) == NULL) {
466: debug("unable to get login class: %s", user);
467: return (NULL);
468: }
469: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 470: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 471: debug("Approval failure for %s", user);
1.37 provos 472: pw = NULL;
1.38 provos 473: }
474: if (as != NULL)
475: auth_close(as);
1.41 markus 476: if (pw != NULL)
477: return (pwcopy(pw));
478: return (NULL);
1.85 djm 479: }
480:
481: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
482: int
483: auth_key_is_revoked(Key *key)
484: {
485: char *key_fp;
486:
487: if (options.revoked_keys_file == NULL)
488: return 0;
489:
490: switch (key_in_file(key, options.revoked_keys_file, 0)) {
491: case 0:
492: /* key not revoked */
493: return 0;
494: case -1:
495: /* Error opening revoked_keys_file: refuse all keys */
496: error("Revoked keys file is unreadable: refusing public key "
497: "authentication");
498: return 1;
499: case 1:
500: /* Key revoked */
501: key_fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
1.86 djm 502: error("WARNING: authentication attempt with a revoked "
503: "%s key %s ", key_type(key), key_fp);
1.85 djm 504: xfree(key_fp);
505: return 1;
506: }
507: fatal("key_in_file returned junk");
1.42 markus 508: }
509:
510: void
511: auth_debug_add(const char *fmt,...)
512: {
513: char buf[1024];
514: va_list args;
515:
516: if (!auth_debug_init)
517: return;
518:
519: va_start(args, fmt);
520: vsnprintf(buf, sizeof(buf), fmt, args);
521: va_end(args);
522: buffer_put_cstring(&auth_debug, buf);
523: }
524:
525: void
526: auth_debug_send(void)
527: {
528: char *msg;
529:
530: if (!auth_debug_init)
531: return;
532: while (buffer_len(&auth_debug)) {
533: msg = buffer_get_string(&auth_debug, NULL);
534: packet_send_debug("%s", msg);
535: xfree(msg);
536: }
537: }
538:
539: void
540: auth_debug_reset(void)
541: {
542: if (auth_debug_init)
543: buffer_clear(&auth_debug);
544: else {
545: buffer_init(&auth_debug);
546: auth_debug_init = 1;
547: }
1.49 markus 548: }
549:
550: struct passwd *
551: fakepw(void)
552: {
553: static struct passwd fake;
554:
555: memset(&fake, 0, sizeof(fake));
556: fake.pw_name = "NOUSER";
557: fake.pw_passwd =
1.51 djm 558: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 559: fake.pw_gecos = "NOUSER";
1.53 deraadt 560: fake.pw_uid = (uid_t)-1;
561: fake.pw_gid = (gid_t)-1;
1.49 markus 562: fake.pw_class = "";
563: fake.pw_dir = "/nonexist";
564: fake.pw_shell = "/nonexist";
565:
566: return (&fake);
1.1 markus 567: }
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