Annotation of src/usr.bin/ssh/auth.c, Revision 1.62
1.1 markus 1: /*
1.19 deraadt 2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
1.9 deraadt 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.
1.1 markus 23: */
24:
25: #include "includes.h"
1.62 ! stevesk 26: RCSID("$OpenBSD: auth.c,v 1.61 2006/02/08 12:15:27 stevesk Exp $");
! 27:
! 28: #include <sys/types.h>
! 29: #include <sys/stat.h>
1.22 markus 30:
31: #include <libgen.h>
1.61 stevesk 32: #include <paths.h>
1.1 markus 33:
34: #include "xmalloc.h"
1.13 markus 35: #include "match.h"
1.14 markus 36: #include "groupaccess.h"
37: #include "log.h"
1.1 markus 38: #include "servconf.h"
1.2 markus 39: #include "auth.h"
1.13 markus 40: #include "auth-options.h"
1.14 markus 41: #include "canohost.h"
1.22 markus 42: #include "buffer.h"
43: #include "bufaux.h"
1.24 markus 44: #include "uidswap.h"
1.40 markus 45: #include "misc.h"
1.42 markus 46: #include "bufaux.h"
47: #include "packet.h"
1.2 markus 48:
1.1 markus 49: /* import */
50: extern ServerOptions options;
51:
1.42 markus 52: /* Debugging messages */
53: Buffer auth_debug;
54: int auth_debug_init;
55:
1.1 markus 56: /*
1.12 markus 57: * Check if the user is allowed to log in via ssh. If user is listed
58: * in DenyUsers or one of user's groups is listed in DenyGroups, false
59: * will be returned. If AllowUsers isn't empty and user isn't listed
60: * there, or if AllowGroups isn't empty and one of user's groups isn't
61: * listed there, false will be returned.
1.1 markus 62: * If the user's shell is not executable, false will be returned.
1.4 markus 63: * Otherwise true is returned.
1.1 markus 64: */
1.5 markus 65: int
1.1 markus 66: allowed_user(struct passwd * pw)
67: {
68: struct stat st;
1.35 markus 69: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 70: char *shell;
1.60 djm 71: u_int i;
1.1 markus 72:
73: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 74: if (!pw || !pw->pw_name)
1.1 markus 75: return 0;
76:
1.7 deraadt 77: /*
78: * Get the shell from the password data. An empty shell field is
79: * legal, and means /bin/sh.
80: */
81: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
82:
1.1 markus 83: /* deny if shell does not exists or is not executable */
1.34 stevesk 84: if (stat(shell, &st) != 0) {
1.47 itojun 85: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 86: pw->pw_name, shell);
1.1 markus 87: return 0;
1.34 stevesk 88: }
1.36 itojun 89: if (S_ISREG(st.st_mode) == 0 ||
90: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 91: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 92: pw->pw_name, shell);
1.1 markus 93: return 0;
1.34 stevesk 94: }
1.1 markus 95:
1.58 dtucker 96: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
97: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 98: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 99: ipaddr = get_remote_ipaddr();
100: }
101:
1.1 markus 102: /* Return false if user is listed in DenyUsers */
103: if (options.num_deny_users > 0) {
104: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 105: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 106: options.deny_users[i])) {
1.57 dtucker 107: logit("User %.100s from %.100s not allowed "
108: "because listed in DenyUsers",
109: pw->pw_name, hostname);
1.1 markus 110: return 0;
1.34 stevesk 111: }
1.1 markus 112: }
113: /* Return false if AllowUsers isn't empty and user isn't listed there */
114: if (options.num_allow_users > 0) {
115: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 116: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 117: options.allow_users[i]))
1.1 markus 118: break;
119: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 120: if (i >= options.num_allow_users) {
1.57 dtucker 121: logit("User %.100s from %.100s not allowed because "
122: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 123: return 0;
1.34 stevesk 124: }
1.1 markus 125: }
126: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 127: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 128: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 129: logit("User %.100s from %.100s not allowed because "
130: "not in any group", pw->pw_name, hostname);
1.1 markus 131: return 0;
1.34 stevesk 132: }
1.1 markus 133:
1.12 markus 134: /* Return false if one of user's groups is listed in DenyGroups */
135: if (options.num_deny_groups > 0)
136: if (ga_match(options.deny_groups,
137: options.num_deny_groups)) {
138: ga_free();
1.57 dtucker 139: logit("User %.100s from %.100s not allowed "
140: "because a group is listed in DenyGroups",
141: pw->pw_name, hostname);
1.1 markus 142: return 0;
1.12 markus 143: }
1.1 markus 144: /*
1.12 markus 145: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 146: * isn't listed there
147: */
1.12 markus 148: if (options.num_allow_groups > 0)
149: if (!ga_match(options.allow_groups,
150: options.num_allow_groups)) {
151: ga_free();
1.57 dtucker 152: logit("User %.100s from %.100s not allowed "
153: "because none of user's groups are listed "
154: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 155: return 0;
1.12 markus 156: }
157: ga_free();
1.1 markus 158: }
159: /* We found no reason not to let this user try to log on... */
160: return 1;
1.13 markus 161: }
162:
163: void
164: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
165: {
166: void (*authlog) (const char *fmt,...) = verbose;
167: char *authmsg;
168:
169: /* Raise logging level */
170: if (authenticated == 1 ||
171: !authctxt->valid ||
1.54 dtucker 172: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 173: strcmp(method, "password") == 0)
1.47 itojun 174: authlog = logit;
1.13 markus 175:
176: if (authctxt->postponed)
177: authmsg = "Postponed";
178: else
179: authmsg = authenticated ? "Accepted" : "Failed";
180:
181: authlog("%s %s for %s%.100s from %.200s port %d%s",
182: authmsg,
183: method,
1.56 markus 184: authctxt->valid ? "" : "invalid user ",
1.29 markus 185: authctxt->user,
1.13 markus 186: get_remote_ipaddr(),
187: get_remote_port(),
188: info);
189: }
190:
191: /*
1.17 markus 192: * Check whether root logins are disallowed.
1.13 markus 193: */
194: int
1.17 markus 195: auth_root_allowed(char *method)
1.13 markus 196: {
1.17 markus 197: switch (options.permit_root_login) {
198: case PERMIT_YES:
1.13 markus 199: return 1;
1.17 markus 200: break;
201: case PERMIT_NO_PASSWD:
202: if (strcmp(method, "password") != 0)
203: return 1;
204: break;
205: case PERMIT_FORCED_ONLY:
206: if (forced_command) {
1.47 itojun 207: logit("Root login accepted for forced command.");
1.17 markus 208: return 1;
209: }
210: break;
1.13 markus 211: }
1.47 itojun 212: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 213: return 0;
214: }
215:
216:
217: /*
218: * Given a template and a passwd structure, build a filename
219: * by substituting % tokenised options. Currently, %% becomes '%',
220: * %h becomes the home directory and %u the username.
221: *
222: * This returns a buffer allocated by xmalloc.
223: */
1.59 djm 224: static char *
225: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 226: {
1.59 djm 227: char *file, *ret;
1.22 markus 228:
1.59 djm 229: file = percent_expand(filename, "h", pw->pw_dir,
230: "u", pw->pw_name, (char *)NULL);
1.22 markus 231:
232: /*
233: * Ensure that filename starts anchored. If not, be backward
234: * compatible and prepend the '%h/'
235: */
1.59 djm 236: if (*file == '/')
237: return (file);
238:
239: ret = xmalloc(MAXPATHLEN);
240: if (strlcpy(ret, pw->pw_dir, MAXPATHLEN) >= MAXPATHLEN ||
241: strlcat(ret, "/", MAXPATHLEN) >= MAXPATHLEN ||
242: strlcat(ret, file, MAXPATHLEN) >= MAXPATHLEN)
243: fatal("expand_authorized_keys: path too long");
1.22 markus 244:
1.59 djm 245: xfree(file);
246: return (ret);
1.22 markus 247: }
248:
249: char *
250: authorized_keys_file(struct passwd *pw)
251: {
1.59 djm 252: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 253: }
254:
255: char *
256: authorized_keys_file2(struct passwd *pw)
257: {
1.59 djm 258: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 259: }
1.24 markus 260:
261: /* return ok if key exists in sysfile or userfile */
262: HostStatus
263: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
264: const char *sysfile, const char *userfile)
265: {
266: Key *found;
267: char *user_hostfile;
268: struct stat st;
1.30 stevesk 269: HostStatus host_status;
1.24 markus 270:
271: /* Check if we know the host and its host key. */
272: found = key_new(key->type);
273: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
274:
275: if (host_status != HOST_OK && userfile != NULL) {
276: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
277: if (options.strict_modes &&
278: (stat(user_hostfile, &st) == 0) &&
279: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 280: (st.st_mode & 022) != 0)) {
1.47 itojun 281: logit("Authentication refused for %.100s: "
1.24 markus 282: "bad owner or modes for %.200s",
283: pw->pw_name, user_hostfile);
284: } else {
285: temporarily_use_uid(pw);
286: host_status = check_host_in_hostfile(user_hostfile,
287: host, key, found, NULL);
288: restore_uid();
289: }
290: xfree(user_hostfile);
291: }
292: key_free(found);
293:
294: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
295: "ok" : "not found", host);
296: return host_status;
297: }
298:
1.22 markus 299:
300: /*
301: * Check a given file for security. This is defined as all components
1.44 stevesk 302: * of the path to the file must be owned by either the owner of
1.23 markus 303: * of the file or root and no directories must be group or world writable.
1.22 markus 304: *
305: * XXX Should any specific check be done for sym links ?
306: *
307: * Takes an open file descriptor, the file name, a uid and and
308: * error buffer plus max size as arguments.
309: *
310: * Returns 0 on success and -1 on failure
311: */
312: int
1.25 provos 313: secure_filename(FILE *f, const char *file, struct passwd *pw,
314: char *err, size_t errlen)
1.22 markus 315: {
1.25 provos 316: uid_t uid = pw->pw_uid;
1.28 markus 317: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 318: char *cp;
1.46 markus 319: int comparehome = 0;
1.22 markus 320: struct stat st;
321:
322: if (realpath(file, buf) == NULL) {
323: snprintf(err, errlen, "realpath %s failed: %s", file,
324: strerror(errno));
325: return -1;
326: }
1.46 markus 327: if (realpath(pw->pw_dir, homedir) != NULL)
328: comparehome = 1;
1.22 markus 329:
330: /* check the open file to avoid races */
331: if (fstat(fileno(f), &st) < 0 ||
332: (st.st_uid != 0 && st.st_uid != uid) ||
333: (st.st_mode & 022) != 0) {
334: snprintf(err, errlen, "bad ownership or modes for file %s",
335: buf);
336: return -1;
337: }
338:
339: /* for each component of the canonical path, walking upwards */
340: for (;;) {
341: if ((cp = dirname(buf)) == NULL) {
342: snprintf(err, errlen, "dirname() failed");
343: return -1;
344: }
345: strlcpy(buf, cp, sizeof(buf));
1.25 provos 346:
1.22 markus 347: debug3("secure_filename: checking '%s'", buf);
348: if (stat(buf, &st) < 0 ||
349: (st.st_uid != 0 && st.st_uid != uid) ||
350: (st.st_mode & 022) != 0) {
1.31 deraadt 351: snprintf(err, errlen,
1.22 markus 352: "bad ownership or modes for directory %s", buf);
353: return -1;
354: }
355:
1.27 markus 356: /* If are passed the homedir then we can stop */
1.46 markus 357: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 358: debug3("secure_filename: terminating check at '%s'",
359: buf);
360: break;
361: }
1.22 markus 362: /*
363: * dirname should always complete with a "/" path,
364: * but we can be paranoid and check for "." too
365: */
366: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
367: break;
368: }
1.17 markus 369: return 0;
1.37 provos 370: }
371:
372: struct passwd *
373: getpwnamallow(const char *user)
374: {
1.38 provos 375: #ifdef HAVE_LOGIN_CAP
376: extern login_cap_t *lc;
377: #ifdef BSD_AUTH
378: auth_session_t *as;
379: #endif
380: #endif
1.37 provos 381: struct passwd *pw;
382:
383: pw = getpwnam(user);
1.45 stevesk 384: if (pw == NULL) {
1.55 markus 385: logit("Invalid user %.100s from %.100s",
1.45 stevesk 386: user, get_remote_ipaddr());
387: return (NULL);
388: }
389: if (!allowed_user(pw))
1.38 provos 390: return (NULL);
391: #ifdef HAVE_LOGIN_CAP
392: if ((lc = login_getclass(pw->pw_class)) == NULL) {
393: debug("unable to get login class: %s", user);
394: return (NULL);
395: }
396: #ifdef BSD_AUTH
397: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 398: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 399: debug("Approval failure for %s", user);
1.37 provos 400: pw = NULL;
1.38 provos 401: }
402: if (as != NULL)
403: auth_close(as);
404: #endif
405: #endif
1.41 markus 406: if (pw != NULL)
407: return (pwcopy(pw));
408: return (NULL);
1.42 markus 409: }
410:
411: void
412: auth_debug_add(const char *fmt,...)
413: {
414: char buf[1024];
415: va_list args;
416:
417: if (!auth_debug_init)
418: return;
419:
420: va_start(args, fmt);
421: vsnprintf(buf, sizeof(buf), fmt, args);
422: va_end(args);
423: buffer_put_cstring(&auth_debug, buf);
424: }
425:
426: void
427: auth_debug_send(void)
428: {
429: char *msg;
430:
431: if (!auth_debug_init)
432: return;
433: while (buffer_len(&auth_debug)) {
434: msg = buffer_get_string(&auth_debug, NULL);
435: packet_send_debug("%s", msg);
436: xfree(msg);
437: }
438: }
439:
440: void
441: auth_debug_reset(void)
442: {
443: if (auth_debug_init)
444: buffer_clear(&auth_debug);
445: else {
446: buffer_init(&auth_debug);
447: auth_debug_init = 1;
448: }
1.49 markus 449: }
450:
451: struct passwd *
452: fakepw(void)
453: {
454: static struct passwd fake;
455:
456: memset(&fake, 0, sizeof(fake));
457: fake.pw_name = "NOUSER";
458: fake.pw_passwd =
1.51 djm 459: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 460: fake.pw_gecos = "NOUSER";
1.53 deraadt 461: fake.pw_uid = (uid_t)-1;
462: fake.pw_gid = (gid_t)-1;
1.49 markus 463: fake.pw_class = "";
464: fake.pw_dir = "/nonexist";
465: fake.pw_shell = "/nonexist";
466:
467: return (&fake);
1.1 markus 468: }
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