Annotation of src/usr.bin/ssh/auth.c, Revision 1.79
1.79 ! dtucker 1: /* $OpenBSD: auth.c,v 1.78 2007/09/21 08:15:29 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>
1.1 markus 39:
40: #include "xmalloc.h"
1.13 markus 41: #include "match.h"
1.14 markus 42: #include "groupaccess.h"
43: #include "log.h"
1.75 deraadt 44: #include "buffer.h"
1.1 markus 45: #include "servconf.h"
1.75 deraadt 46: #include "key.h"
47: #include "hostfile.h"
1.2 markus 48: #include "auth.h"
1.13 markus 49: #include "auth-options.h"
1.14 markus 50: #include "canohost.h"
1.24 markus 51: #include "uidswap.h"
1.40 markus 52: #include "misc.h"
1.42 markus 53: #include "packet.h"
1.75 deraadt 54: #ifdef GSSAPI
55: #include "ssh-gss.h"
56: #endif
1.67 dtucker 57: #include "monitor_wrap.h"
1.2 markus 58:
1.1 markus 59: /* import */
60: extern ServerOptions options;
1.67 dtucker 61: extern int use_privsep;
1.1 markus 62:
1.42 markus 63: /* Debugging messages */
64: Buffer auth_debug;
65: int auth_debug_init;
66:
1.1 markus 67: /*
1.12 markus 68: * Check if the user is allowed to log in via ssh. If user is listed
69: * in DenyUsers or one of user's groups is listed in DenyGroups, false
70: * will be returned. If AllowUsers isn't empty and user isn't listed
71: * there, or if AllowGroups isn't empty and one of user's groups isn't
72: * listed there, false will be returned.
1.1 markus 73: * If the user's shell is not executable, false will be returned.
1.4 markus 74: * Otherwise true is returned.
1.1 markus 75: */
1.5 markus 76: int
1.1 markus 77: allowed_user(struct passwd * pw)
78: {
79: struct stat st;
1.35 markus 80: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 81: char *shell;
1.60 djm 82: u_int i;
1.1 markus 83:
84: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 85: if (!pw || !pw->pw_name)
1.1 markus 86: return 0;
87:
1.7 deraadt 88: /*
89: * Get the shell from the password data. An empty shell field is
90: * legal, and means /bin/sh.
91: */
92: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
93:
1.1 markus 94: /* deny if shell does not exists or is not executable */
1.34 stevesk 95: if (stat(shell, &st) != 0) {
1.47 itojun 96: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 97: pw->pw_name, shell);
1.1 markus 98: return 0;
1.34 stevesk 99: }
1.36 itojun 100: if (S_ISREG(st.st_mode) == 0 ||
101: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 102: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 103: pw->pw_name, shell);
1.1 markus 104: return 0;
1.34 stevesk 105: }
1.1 markus 106:
1.58 dtucker 107: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
108: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 109: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 110: ipaddr = get_remote_ipaddr();
111: }
112:
1.1 markus 113: /* Return false if user is listed in DenyUsers */
114: if (options.num_deny_users > 0) {
115: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 116: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 117: options.deny_users[i])) {
1.57 dtucker 118: logit("User %.100s from %.100s not allowed "
119: "because listed in DenyUsers",
120: pw->pw_name, hostname);
1.1 markus 121: return 0;
1.34 stevesk 122: }
1.1 markus 123: }
124: /* Return false if AllowUsers isn't empty and user isn't listed there */
125: if (options.num_allow_users > 0) {
126: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 127: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 128: options.allow_users[i]))
1.1 markus 129: break;
130: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 131: if (i >= options.num_allow_users) {
1.57 dtucker 132: logit("User %.100s from %.100s not allowed because "
133: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 134: return 0;
1.34 stevesk 135: }
1.1 markus 136: }
137: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 138: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 139: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 140: logit("User %.100s from %.100s not allowed because "
141: "not in any group", pw->pw_name, hostname);
1.1 markus 142: return 0;
1.34 stevesk 143: }
1.1 markus 144:
1.12 markus 145: /* Return false if one of user's groups is listed in DenyGroups */
146: if (options.num_deny_groups > 0)
147: if (ga_match(options.deny_groups,
148: options.num_deny_groups)) {
149: ga_free();
1.57 dtucker 150: logit("User %.100s from %.100s not allowed "
151: "because a group is listed in DenyGroups",
152: pw->pw_name, hostname);
1.1 markus 153: return 0;
1.12 markus 154: }
1.1 markus 155: /*
1.12 markus 156: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 157: * isn't listed there
158: */
1.12 markus 159: if (options.num_allow_groups > 0)
160: if (!ga_match(options.allow_groups,
161: options.num_allow_groups)) {
162: ga_free();
1.57 dtucker 163: logit("User %.100s from %.100s not allowed "
164: "because none of user's groups are listed "
165: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 166: return 0;
1.12 markus 167: }
168: ga_free();
1.1 markus 169: }
170: /* We found no reason not to let this user try to log on... */
171: return 1;
1.13 markus 172: }
173:
174: void
175: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
176: {
177: void (*authlog) (const char *fmt,...) = verbose;
178: char *authmsg;
1.67 dtucker 179:
180: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
181: return;
1.13 markus 182:
183: /* Raise logging level */
184: if (authenticated == 1 ||
185: !authctxt->valid ||
1.54 dtucker 186: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 187: strcmp(method, "password") == 0)
1.47 itojun 188: authlog = logit;
1.13 markus 189:
190: if (authctxt->postponed)
191: authmsg = "Postponed";
192: else
193: authmsg = authenticated ? "Accepted" : "Failed";
194:
195: authlog("%s %s for %s%.100s from %.200s port %d%s",
196: authmsg,
197: method,
1.56 markus 198: authctxt->valid ? "" : "invalid user ",
1.29 markus 199: authctxt->user,
1.13 markus 200: get_remote_ipaddr(),
201: get_remote_port(),
202: info);
203: }
204:
205: /*
1.17 markus 206: * Check whether root logins are disallowed.
1.13 markus 207: */
208: int
1.17 markus 209: auth_root_allowed(char *method)
1.13 markus 210: {
1.17 markus 211: switch (options.permit_root_login) {
212: case PERMIT_YES:
1.13 markus 213: return 1;
1.17 markus 214: case PERMIT_NO_PASSWD:
215: if (strcmp(method, "password") != 0)
216: return 1;
217: break;
218: case PERMIT_FORCED_ONLY:
219: if (forced_command) {
1.47 itojun 220: logit("Root login accepted for forced command.");
1.17 markus 221: return 1;
222: }
223: break;
1.13 markus 224: }
1.47 itojun 225: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 226: return 0;
227: }
228:
229:
230: /*
231: * Given a template and a passwd structure, build a filename
232: * by substituting % tokenised options. Currently, %% becomes '%',
233: * %h becomes the home directory and %u the username.
234: *
235: * This returns a buffer allocated by xmalloc.
236: */
1.59 djm 237: static char *
238: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 239: {
1.65 djm 240: char *file, ret[MAXPATHLEN];
241: int i;
1.22 markus 242:
1.59 djm 243: file = percent_expand(filename, "h", pw->pw_dir,
244: "u", pw->pw_name, (char *)NULL);
1.22 markus 245:
246: /*
247: * Ensure that filename starts anchored. If not, be backward
248: * compatible and prepend the '%h/'
249: */
1.59 djm 250: if (*file == '/')
251: return (file);
252:
1.65 djm 253: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
254: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 255: fatal("expand_authorized_keys: path too long");
256: xfree(file);
1.65 djm 257: return (xstrdup(ret));
1.22 markus 258: }
259:
260: char *
261: authorized_keys_file(struct passwd *pw)
262: {
1.59 djm 263: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 264: }
265:
266: char *
267: authorized_keys_file2(struct passwd *pw)
268: {
1.59 djm 269: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 270: }
1.24 markus 271:
272: /* return ok if key exists in sysfile or userfile */
273: HostStatus
274: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
275: const char *sysfile, const char *userfile)
276: {
277: Key *found;
278: char *user_hostfile;
279: struct stat st;
1.30 stevesk 280: HostStatus host_status;
1.24 markus 281:
282: /* Check if we know the host and its host key. */
283: found = key_new(key->type);
284: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
285:
286: if (host_status != HOST_OK && userfile != NULL) {
287: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
288: if (options.strict_modes &&
289: (stat(user_hostfile, &st) == 0) &&
290: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 291: (st.st_mode & 022) != 0)) {
1.47 itojun 292: logit("Authentication refused for %.100s: "
1.24 markus 293: "bad owner or modes for %.200s",
294: pw->pw_name, user_hostfile);
295: } else {
296: temporarily_use_uid(pw);
297: host_status = check_host_in_hostfile(user_hostfile,
298: host, key, found, NULL);
299: restore_uid();
300: }
301: xfree(user_hostfile);
302: }
303: key_free(found);
304:
305: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
306: "ok" : "not found", host);
307: return host_status;
308: }
309:
1.22 markus 310:
311: /*
312: * Check a given file for security. This is defined as all components
1.44 stevesk 313: * of the path to the file must be owned by either the owner of
1.23 markus 314: * of the file or root and no directories must be group or world writable.
1.22 markus 315: *
316: * XXX Should any specific check be done for sym links ?
317: *
318: * Takes an open file descriptor, the file name, a uid and and
319: * error buffer plus max size as arguments.
320: *
321: * Returns 0 on success and -1 on failure
322: */
1.79 ! dtucker 323: static int
1.25 provos 324: secure_filename(FILE *f, const char *file, struct passwd *pw,
325: char *err, size_t errlen)
1.22 markus 326: {
1.25 provos 327: uid_t uid = pw->pw_uid;
1.28 markus 328: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 329: char *cp;
1.46 markus 330: int comparehome = 0;
1.22 markus 331: struct stat st;
332:
333: if (realpath(file, buf) == NULL) {
334: snprintf(err, errlen, "realpath %s failed: %s", file,
335: strerror(errno));
336: return -1;
337: }
1.46 markus 338: if (realpath(pw->pw_dir, homedir) != NULL)
339: comparehome = 1;
1.22 markus 340:
341: /* check the open file to avoid races */
342: if (fstat(fileno(f), &st) < 0 ||
343: (st.st_uid != 0 && st.st_uid != uid) ||
344: (st.st_mode & 022) != 0) {
345: snprintf(err, errlen, "bad ownership or modes for file %s",
346: buf);
347: return -1;
348: }
349:
350: /* for each component of the canonical path, walking upwards */
351: for (;;) {
352: if ((cp = dirname(buf)) == NULL) {
353: snprintf(err, errlen, "dirname() failed");
354: return -1;
355: }
356: strlcpy(buf, cp, sizeof(buf));
1.25 provos 357:
1.22 markus 358: debug3("secure_filename: checking '%s'", buf);
359: if (stat(buf, &st) < 0 ||
360: (st.st_uid != 0 && st.st_uid != uid) ||
361: (st.st_mode & 022) != 0) {
1.31 deraadt 362: snprintf(err, errlen,
1.22 markus 363: "bad ownership or modes for directory %s", buf);
364: return -1;
365: }
366:
1.27 markus 367: /* If are passed the homedir then we can stop */
1.46 markus 368: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 369: debug3("secure_filename: terminating check at '%s'",
370: buf);
371: break;
372: }
1.22 markus 373: /*
374: * dirname should always complete with a "/" path,
375: * but we can be paranoid and check for "." too
376: */
377: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
378: break;
379: }
1.17 markus 380: return 0;
1.79 ! dtucker 381: }
! 382:
! 383: FILE *
! 384: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
! 385: {
! 386: char line[1024];
! 387: struct stat st;
! 388: int fd;
! 389: FILE *f;
! 390:
! 391: /*
! 392: * Open the file containing the authorized keys
! 393: * Fail quietly if file does not exist
! 394: */
! 395: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1)
! 396: return NULL;
! 397:
! 398: if (fstat(fd, &st) < 0) {
! 399: close(fd);
! 400: return NULL;
! 401: }
! 402: if (!S_ISREG(st.st_mode)) {
! 403: logit("User %s authorized keys %s is not a regular file",
! 404: pw->pw_name, file);
! 405: close(fd);
! 406: return NULL;
! 407: }
! 408: unset_nonblock(fd);
! 409: if ((f = fdopen(fd, "r")) == NULL) {
! 410: close(fd);
! 411: return NULL;
! 412: }
! 413: if (options.strict_modes &&
! 414: secure_filename(f, file, pw, line, sizeof(line)) != 0) {
! 415: fclose(f);
! 416: logit("Authentication refused: %s", line);
! 417: return NULL;
! 418: }
! 419:
! 420: return f;
1.37 provos 421: }
422:
423: struct passwd *
424: getpwnamallow(const char *user)
425: {
1.38 provos 426: extern login_cap_t *lc;
427: auth_session_t *as;
1.37 provos 428: struct passwd *pw;
1.71 dtucker 429:
430: parse_server_match_config(&options, user,
431: get_canonical_hostname(options.use_dns), get_remote_ipaddr());
1.37 provos 432:
433: pw = getpwnam(user);
1.45 stevesk 434: if (pw == NULL) {
1.55 markus 435: logit("Invalid user %.100s from %.100s",
1.45 stevesk 436: user, get_remote_ipaddr());
437: return (NULL);
438: }
439: if (!allowed_user(pw))
1.38 provos 440: return (NULL);
441: if ((lc = login_getclass(pw->pw_class)) == NULL) {
442: debug("unable to get login class: %s", user);
443: return (NULL);
444: }
445: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 446: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 447: debug("Approval failure for %s", user);
1.37 provos 448: pw = NULL;
1.38 provos 449: }
450: if (as != NULL)
451: auth_close(as);
1.41 markus 452: if (pw != NULL)
453: return (pwcopy(pw));
454: return (NULL);
1.42 markus 455: }
456:
457: void
458: auth_debug_add(const char *fmt,...)
459: {
460: char buf[1024];
461: va_list args;
462:
463: if (!auth_debug_init)
464: return;
465:
466: va_start(args, fmt);
467: vsnprintf(buf, sizeof(buf), fmt, args);
468: va_end(args);
469: buffer_put_cstring(&auth_debug, buf);
470: }
471:
472: void
473: auth_debug_send(void)
474: {
475: char *msg;
476:
477: if (!auth_debug_init)
478: return;
479: while (buffer_len(&auth_debug)) {
480: msg = buffer_get_string(&auth_debug, NULL);
481: packet_send_debug("%s", msg);
482: xfree(msg);
483: }
484: }
485:
486: void
487: auth_debug_reset(void)
488: {
489: if (auth_debug_init)
490: buffer_clear(&auth_debug);
491: else {
492: buffer_init(&auth_debug);
493: auth_debug_init = 1;
494: }
1.49 markus 495: }
496:
497: struct passwd *
498: fakepw(void)
499: {
500: static struct passwd fake;
501:
502: memset(&fake, 0, sizeof(fake));
503: fake.pw_name = "NOUSER";
504: fake.pw_passwd =
1.51 djm 505: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 506: fake.pw_gecos = "NOUSER";
1.53 deraadt 507: fake.pw_uid = (uid_t)-1;
508: fake.pw_gid = (gid_t)-1;
1.49 markus 509: fake.pw_class = "";
510: fake.pw_dir = "/nonexist";
511: fake.pw_shell = "/nonexist";
512:
513: return (&fake);
1.1 markus 514: }
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