Annotation of src/usr.bin/ssh/auth.c, Revision 1.68
1.68 ! stevesk 1: /* $OpenBSD: auth.c,v 1.67 2006/03/30 11:40:21 dtucker 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:
26: #include "includes.h"
1.62 stevesk 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>
1.68 ! stevesk 33: #include <pwd.h>
1.1 markus 34:
35: #include "xmalloc.h"
1.13 markus 36: #include "match.h"
1.14 markus 37: #include "groupaccess.h"
38: #include "log.h"
1.1 markus 39: #include "servconf.h"
1.2 markus 40: #include "auth.h"
1.13 markus 41: #include "auth-options.h"
1.14 markus 42: #include "canohost.h"
1.22 markus 43: #include "buffer.h"
44: #include "bufaux.h"
1.24 markus 45: #include "uidswap.h"
1.40 markus 46: #include "misc.h"
1.42 markus 47: #include "bufaux.h"
48: #include "packet.h"
1.67 dtucker 49: #include "monitor_wrap.h"
1.2 markus 50:
1.1 markus 51: /* import */
52: extern ServerOptions options;
1.67 dtucker 53: extern int use_privsep;
1.1 markus 54:
1.42 markus 55: /* Debugging messages */
56: Buffer auth_debug;
57: int auth_debug_init;
58:
1.1 markus 59: /*
1.12 markus 60: * Check if the user is allowed to log in via ssh. If user is listed
61: * in DenyUsers or one of user's groups is listed in DenyGroups, false
62: * will be returned. If AllowUsers isn't empty and user isn't listed
63: * there, or if AllowGroups isn't empty and one of user's groups isn't
64: * listed there, false will be returned.
1.1 markus 65: * If the user's shell is not executable, false will be returned.
1.4 markus 66: * Otherwise true is returned.
1.1 markus 67: */
1.5 markus 68: int
1.1 markus 69: allowed_user(struct passwd * pw)
70: {
71: struct stat st;
1.35 markus 72: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 73: char *shell;
1.60 djm 74: u_int i;
1.1 markus 75:
76: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 77: if (!pw || !pw->pw_name)
1.1 markus 78: return 0;
79:
1.7 deraadt 80: /*
81: * Get the shell from the password data. An empty shell field is
82: * legal, and means /bin/sh.
83: */
84: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
85:
1.1 markus 86: /* deny if shell does not exists or is not executable */
1.34 stevesk 87: if (stat(shell, &st) != 0) {
1.47 itojun 88: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 89: pw->pw_name, shell);
1.1 markus 90: return 0;
1.34 stevesk 91: }
1.36 itojun 92: if (S_ISREG(st.st_mode) == 0 ||
93: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 94: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 95: pw->pw_name, shell);
1.1 markus 96: return 0;
1.34 stevesk 97: }
1.1 markus 98:
1.58 dtucker 99: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
100: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 101: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 102: ipaddr = get_remote_ipaddr();
103: }
104:
1.1 markus 105: /* Return false if user is listed in DenyUsers */
106: if (options.num_deny_users > 0) {
107: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 108: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 109: options.deny_users[i])) {
1.57 dtucker 110: logit("User %.100s from %.100s not allowed "
111: "because listed in DenyUsers",
112: pw->pw_name, hostname);
1.1 markus 113: return 0;
1.34 stevesk 114: }
1.1 markus 115: }
116: /* Return false if AllowUsers isn't empty and user isn't listed there */
117: if (options.num_allow_users > 0) {
118: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 119: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 120: options.allow_users[i]))
1.1 markus 121: break;
122: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 123: if (i >= options.num_allow_users) {
1.57 dtucker 124: logit("User %.100s from %.100s not allowed because "
125: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 126: return 0;
1.34 stevesk 127: }
1.1 markus 128: }
129: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 130: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 131: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 132: logit("User %.100s from %.100s not allowed because "
133: "not in any group", pw->pw_name, hostname);
1.1 markus 134: return 0;
1.34 stevesk 135: }
1.1 markus 136:
1.12 markus 137: /* Return false if one of user's groups is listed in DenyGroups */
138: if (options.num_deny_groups > 0)
139: if (ga_match(options.deny_groups,
140: options.num_deny_groups)) {
141: ga_free();
1.57 dtucker 142: logit("User %.100s from %.100s not allowed "
143: "because a group is listed in DenyGroups",
144: pw->pw_name, hostname);
1.1 markus 145: return 0;
1.12 markus 146: }
1.1 markus 147: /*
1.12 markus 148: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 149: * isn't listed there
150: */
1.12 markus 151: if (options.num_allow_groups > 0)
152: if (!ga_match(options.allow_groups,
153: options.num_allow_groups)) {
154: ga_free();
1.57 dtucker 155: logit("User %.100s from %.100s not allowed "
156: "because none of user's groups are listed "
157: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 158: return 0;
1.12 markus 159: }
160: ga_free();
1.1 markus 161: }
162: /* We found no reason not to let this user try to log on... */
163: return 1;
1.13 markus 164: }
165:
166: void
167: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
168: {
169: void (*authlog) (const char *fmt,...) = verbose;
170: char *authmsg;
1.67 dtucker 171:
172: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
173: return;
1.13 markus 174:
175: /* Raise logging level */
176: if (authenticated == 1 ||
177: !authctxt->valid ||
1.54 dtucker 178: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 179: strcmp(method, "password") == 0)
1.47 itojun 180: authlog = logit;
1.13 markus 181:
182: if (authctxt->postponed)
183: authmsg = "Postponed";
184: else
185: authmsg = authenticated ? "Accepted" : "Failed";
186:
187: authlog("%s %s for %s%.100s from %.200s port %d%s",
188: authmsg,
189: method,
1.56 markus 190: authctxt->valid ? "" : "invalid user ",
1.29 markus 191: authctxt->user,
1.13 markus 192: get_remote_ipaddr(),
193: get_remote_port(),
194: info);
195: }
196:
197: /*
1.17 markus 198: * Check whether root logins are disallowed.
1.13 markus 199: */
200: int
1.17 markus 201: auth_root_allowed(char *method)
1.13 markus 202: {
1.17 markus 203: switch (options.permit_root_login) {
204: case PERMIT_YES:
1.13 markus 205: return 1;
1.17 markus 206: case PERMIT_NO_PASSWD:
207: if (strcmp(method, "password") != 0)
208: return 1;
209: break;
210: case PERMIT_FORCED_ONLY:
211: if (forced_command) {
1.47 itojun 212: logit("Root login accepted for forced command.");
1.17 markus 213: return 1;
214: }
215: break;
1.13 markus 216: }
1.47 itojun 217: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 218: return 0;
219: }
220:
221:
222: /*
223: * Given a template and a passwd structure, build a filename
224: * by substituting % tokenised options. Currently, %% becomes '%',
225: * %h becomes the home directory and %u the username.
226: *
227: * This returns a buffer allocated by xmalloc.
228: */
1.59 djm 229: static char *
230: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 231: {
1.65 djm 232: char *file, ret[MAXPATHLEN];
233: int i;
1.22 markus 234:
1.59 djm 235: file = percent_expand(filename, "h", pw->pw_dir,
236: "u", pw->pw_name, (char *)NULL);
1.22 markus 237:
238: /*
239: * Ensure that filename starts anchored. If not, be backward
240: * compatible and prepend the '%h/'
241: */
1.59 djm 242: if (*file == '/')
243: return (file);
244:
1.65 djm 245: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
246: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 247: fatal("expand_authorized_keys: path too long");
248: xfree(file);
1.65 djm 249: return (xstrdup(ret));
1.22 markus 250: }
251:
252: char *
253: authorized_keys_file(struct passwd *pw)
254: {
1.59 djm 255: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 256: }
257:
258: char *
259: authorized_keys_file2(struct passwd *pw)
260: {
1.59 djm 261: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 262: }
1.24 markus 263:
264: /* return ok if key exists in sysfile or userfile */
265: HostStatus
266: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
267: const char *sysfile, const char *userfile)
268: {
269: Key *found;
270: char *user_hostfile;
271: struct stat st;
1.30 stevesk 272: HostStatus host_status;
1.24 markus 273:
274: /* Check if we know the host and its host key. */
275: found = key_new(key->type);
276: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
277:
278: if (host_status != HOST_OK && userfile != NULL) {
279: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
280: if (options.strict_modes &&
281: (stat(user_hostfile, &st) == 0) &&
282: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 283: (st.st_mode & 022) != 0)) {
1.47 itojun 284: logit("Authentication refused for %.100s: "
1.24 markus 285: "bad owner or modes for %.200s",
286: pw->pw_name, user_hostfile);
287: } else {
288: temporarily_use_uid(pw);
289: host_status = check_host_in_hostfile(user_hostfile,
290: host, key, found, NULL);
291: restore_uid();
292: }
293: xfree(user_hostfile);
294: }
295: key_free(found);
296:
297: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
298: "ok" : "not found", host);
299: return host_status;
300: }
301:
1.22 markus 302:
303: /*
304: * Check a given file for security. This is defined as all components
1.44 stevesk 305: * of the path to the file must be owned by either the owner of
1.23 markus 306: * of the file or root and no directories must be group or world writable.
1.22 markus 307: *
308: * XXX Should any specific check be done for sym links ?
309: *
310: * Takes an open file descriptor, the file name, a uid and and
311: * error buffer plus max size as arguments.
312: *
313: * Returns 0 on success and -1 on failure
314: */
315: int
1.25 provos 316: secure_filename(FILE *f, const char *file, struct passwd *pw,
317: char *err, size_t errlen)
1.22 markus 318: {
1.25 provos 319: uid_t uid = pw->pw_uid;
1.28 markus 320: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 321: char *cp;
1.46 markus 322: int comparehome = 0;
1.22 markus 323: struct stat st;
324:
325: if (realpath(file, buf) == NULL) {
326: snprintf(err, errlen, "realpath %s failed: %s", file,
327: strerror(errno));
328: return -1;
329: }
1.46 markus 330: if (realpath(pw->pw_dir, homedir) != NULL)
331: comparehome = 1;
1.22 markus 332:
333: /* check the open file to avoid races */
334: if (fstat(fileno(f), &st) < 0 ||
335: (st.st_uid != 0 && st.st_uid != uid) ||
336: (st.st_mode & 022) != 0) {
337: snprintf(err, errlen, "bad ownership or modes for file %s",
338: buf);
339: return -1;
340: }
341:
342: /* for each component of the canonical path, walking upwards */
343: for (;;) {
344: if ((cp = dirname(buf)) == NULL) {
345: snprintf(err, errlen, "dirname() failed");
346: return -1;
347: }
348: strlcpy(buf, cp, sizeof(buf));
1.25 provos 349:
1.22 markus 350: debug3("secure_filename: checking '%s'", buf);
351: if (stat(buf, &st) < 0 ||
352: (st.st_uid != 0 && st.st_uid != uid) ||
353: (st.st_mode & 022) != 0) {
1.31 deraadt 354: snprintf(err, errlen,
1.22 markus 355: "bad ownership or modes for directory %s", buf);
356: return -1;
357: }
358:
1.27 markus 359: /* If are passed the homedir then we can stop */
1.46 markus 360: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 361: debug3("secure_filename: terminating check at '%s'",
362: buf);
363: break;
364: }
1.22 markus 365: /*
366: * dirname should always complete with a "/" path,
367: * but we can be paranoid and check for "." too
368: */
369: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
370: break;
371: }
1.17 markus 372: return 0;
1.37 provos 373: }
374:
375: struct passwd *
376: getpwnamallow(const char *user)
377: {
1.38 provos 378: #ifdef HAVE_LOGIN_CAP
379: extern login_cap_t *lc;
380: #ifdef BSD_AUTH
381: auth_session_t *as;
382: #endif
383: #endif
1.37 provos 384: struct passwd *pw;
385:
386: pw = getpwnam(user);
1.45 stevesk 387: if (pw == NULL) {
1.55 markus 388: logit("Invalid user %.100s from %.100s",
1.45 stevesk 389: user, get_remote_ipaddr());
390: return (NULL);
391: }
392: if (!allowed_user(pw))
1.38 provos 393: return (NULL);
394: #ifdef HAVE_LOGIN_CAP
395: if ((lc = login_getclass(pw->pw_class)) == NULL) {
396: debug("unable to get login class: %s", user);
397: return (NULL);
398: }
399: #ifdef BSD_AUTH
400: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 401: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 402: debug("Approval failure for %s", user);
1.37 provos 403: pw = NULL;
1.38 provos 404: }
405: if (as != NULL)
406: auth_close(as);
407: #endif
408: #endif
1.41 markus 409: if (pw != NULL)
410: return (pwcopy(pw));
411: return (NULL);
1.42 markus 412: }
413:
414: void
415: auth_debug_add(const char *fmt,...)
416: {
417: char buf[1024];
418: va_list args;
419:
420: if (!auth_debug_init)
421: return;
422:
423: va_start(args, fmt);
424: vsnprintf(buf, sizeof(buf), fmt, args);
425: va_end(args);
426: buffer_put_cstring(&auth_debug, buf);
427: }
428:
429: void
430: auth_debug_send(void)
431: {
432: char *msg;
433:
434: if (!auth_debug_init)
435: return;
436: while (buffer_len(&auth_debug)) {
437: msg = buffer_get_string(&auth_debug, NULL);
438: packet_send_debug("%s", msg);
439: xfree(msg);
440: }
441: }
442:
443: void
444: auth_debug_reset(void)
445: {
446: if (auth_debug_init)
447: buffer_clear(&auth_debug);
448: else {
449: buffer_init(&auth_debug);
450: auth_debug_init = 1;
451: }
1.49 markus 452: }
453:
454: struct passwd *
455: fakepw(void)
456: {
457: static struct passwd fake;
458:
459: memset(&fake, 0, sizeof(fake));
460: fake.pw_name = "NOUSER";
461: fake.pw_passwd =
1.51 djm 462: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 463: fake.pw_gecos = "NOUSER";
1.53 deraadt 464: fake.pw_uid = (uid_t)-1;
465: fake.pw_gid = (gid_t)-1;
1.49 markus 466: fake.pw_class = "";
467: fake.pw_dir = "/nonexist";
468: fake.pw_shell = "/nonexist";
469:
470: return (&fake);
1.1 markus 471: }
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