Annotation of src/usr.bin/ssh/auth.c, Revision 1.69
1.69 ! stevesk 1: /* $OpenBSD: auth.c,v 1.68 2006/07/06 16:03:53 stevesk 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>
1.69 ! stevesk 34: #include <stdarg.h>
1.1 markus 35:
36: #include "xmalloc.h"
1.13 markus 37: #include "match.h"
1.14 markus 38: #include "groupaccess.h"
39: #include "log.h"
1.1 markus 40: #include "servconf.h"
1.2 markus 41: #include "auth.h"
1.13 markus 42: #include "auth-options.h"
1.14 markus 43: #include "canohost.h"
1.22 markus 44: #include "buffer.h"
45: #include "bufaux.h"
1.24 markus 46: #include "uidswap.h"
1.40 markus 47: #include "misc.h"
1.42 markus 48: #include "bufaux.h"
49: #include "packet.h"
1.67 dtucker 50: #include "monitor_wrap.h"
1.2 markus 51:
1.1 markus 52: /* import */
53: extern ServerOptions options;
1.67 dtucker 54: extern int use_privsep;
1.1 markus 55:
1.42 markus 56: /* Debugging messages */
57: Buffer auth_debug;
58: int auth_debug_init;
59:
1.1 markus 60: /*
1.12 markus 61: * Check if the user is allowed to log in via ssh. If user is listed
62: * in DenyUsers or one of user's groups is listed in DenyGroups, false
63: * will be returned. If AllowUsers isn't empty and user isn't listed
64: * there, or if AllowGroups isn't empty and one of user's groups isn't
65: * listed there, false will be returned.
1.1 markus 66: * If the user's shell is not executable, false will be returned.
1.4 markus 67: * Otherwise true is returned.
1.1 markus 68: */
1.5 markus 69: int
1.1 markus 70: allowed_user(struct passwd * pw)
71: {
72: struct stat st;
1.35 markus 73: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 74: char *shell;
1.60 djm 75: u_int i;
1.1 markus 76:
77: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 78: if (!pw || !pw->pw_name)
1.1 markus 79: return 0;
80:
1.7 deraadt 81: /*
82: * Get the shell from the password data. An empty shell field is
83: * legal, and means /bin/sh.
84: */
85: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
86:
1.1 markus 87: /* deny if shell does not exists or is not executable */
1.34 stevesk 88: if (stat(shell, &st) != 0) {
1.47 itojun 89: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 90: pw->pw_name, shell);
1.1 markus 91: return 0;
1.34 stevesk 92: }
1.36 itojun 93: if (S_ISREG(st.st_mode) == 0 ||
94: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 95: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 96: pw->pw_name, shell);
1.1 markus 97: return 0;
1.34 stevesk 98: }
1.1 markus 99:
1.58 dtucker 100: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
101: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 102: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 103: ipaddr = get_remote_ipaddr();
104: }
105:
1.1 markus 106: /* Return false if user is listed in DenyUsers */
107: if (options.num_deny_users > 0) {
108: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 109: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 110: options.deny_users[i])) {
1.57 dtucker 111: logit("User %.100s from %.100s not allowed "
112: "because listed in DenyUsers",
113: pw->pw_name, hostname);
1.1 markus 114: return 0;
1.34 stevesk 115: }
1.1 markus 116: }
117: /* Return false if AllowUsers isn't empty and user isn't listed there */
118: if (options.num_allow_users > 0) {
119: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 120: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 121: options.allow_users[i]))
1.1 markus 122: break;
123: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 124: if (i >= options.num_allow_users) {
1.57 dtucker 125: logit("User %.100s from %.100s not allowed because "
126: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 127: return 0;
1.34 stevesk 128: }
1.1 markus 129: }
130: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 131: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 132: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 133: logit("User %.100s from %.100s not allowed because "
134: "not in any group", pw->pw_name, hostname);
1.1 markus 135: return 0;
1.34 stevesk 136: }
1.1 markus 137:
1.12 markus 138: /* Return false if one of user's groups is listed in DenyGroups */
139: if (options.num_deny_groups > 0)
140: if (ga_match(options.deny_groups,
141: options.num_deny_groups)) {
142: ga_free();
1.57 dtucker 143: logit("User %.100s from %.100s not allowed "
144: "because a group is listed in DenyGroups",
145: pw->pw_name, hostname);
1.1 markus 146: return 0;
1.12 markus 147: }
1.1 markus 148: /*
1.12 markus 149: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 150: * isn't listed there
151: */
1.12 markus 152: if (options.num_allow_groups > 0)
153: if (!ga_match(options.allow_groups,
154: options.num_allow_groups)) {
155: ga_free();
1.57 dtucker 156: logit("User %.100s from %.100s not allowed "
157: "because none of user's groups are listed "
158: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 159: return 0;
1.12 markus 160: }
161: ga_free();
1.1 markus 162: }
163: /* We found no reason not to let this user try to log on... */
164: return 1;
1.13 markus 165: }
166:
167: void
168: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
169: {
170: void (*authlog) (const char *fmt,...) = verbose;
171: char *authmsg;
1.67 dtucker 172:
173: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
174: return;
1.13 markus 175:
176: /* Raise logging level */
177: if (authenticated == 1 ||
178: !authctxt->valid ||
1.54 dtucker 179: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 180: strcmp(method, "password") == 0)
1.47 itojun 181: authlog = logit;
1.13 markus 182:
183: if (authctxt->postponed)
184: authmsg = "Postponed";
185: else
186: authmsg = authenticated ? "Accepted" : "Failed";
187:
188: authlog("%s %s for %s%.100s from %.200s port %d%s",
189: authmsg,
190: method,
1.56 markus 191: authctxt->valid ? "" : "invalid user ",
1.29 markus 192: authctxt->user,
1.13 markus 193: get_remote_ipaddr(),
194: get_remote_port(),
195: info);
196: }
197:
198: /*
1.17 markus 199: * Check whether root logins are disallowed.
1.13 markus 200: */
201: int
1.17 markus 202: auth_root_allowed(char *method)
1.13 markus 203: {
1.17 markus 204: switch (options.permit_root_login) {
205: case PERMIT_YES:
1.13 markus 206: return 1;
1.17 markus 207: case PERMIT_NO_PASSWD:
208: if (strcmp(method, "password") != 0)
209: return 1;
210: break;
211: case PERMIT_FORCED_ONLY:
212: if (forced_command) {
1.47 itojun 213: logit("Root login accepted for forced command.");
1.17 markus 214: return 1;
215: }
216: break;
1.13 markus 217: }
1.47 itojun 218: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 219: return 0;
220: }
221:
222:
223: /*
224: * Given a template and a passwd structure, build a filename
225: * by substituting % tokenised options. Currently, %% becomes '%',
226: * %h becomes the home directory and %u the username.
227: *
228: * This returns a buffer allocated by xmalloc.
229: */
1.59 djm 230: static char *
231: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 232: {
1.65 djm 233: char *file, ret[MAXPATHLEN];
234: int i;
1.22 markus 235:
1.59 djm 236: file = percent_expand(filename, "h", pw->pw_dir,
237: "u", pw->pw_name, (char *)NULL);
1.22 markus 238:
239: /*
240: * Ensure that filename starts anchored. If not, be backward
241: * compatible and prepend the '%h/'
242: */
1.59 djm 243: if (*file == '/')
244: return (file);
245:
1.65 djm 246: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
247: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 248: fatal("expand_authorized_keys: path too long");
249: xfree(file);
1.65 djm 250: return (xstrdup(ret));
1.22 markus 251: }
252:
253: char *
254: authorized_keys_file(struct passwd *pw)
255: {
1.59 djm 256: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 257: }
258:
259: char *
260: authorized_keys_file2(struct passwd *pw)
261: {
1.59 djm 262: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 263: }
1.24 markus 264:
265: /* return ok if key exists in sysfile or userfile */
266: HostStatus
267: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
268: const char *sysfile, const char *userfile)
269: {
270: Key *found;
271: char *user_hostfile;
272: struct stat st;
1.30 stevesk 273: HostStatus host_status;
1.24 markus 274:
275: /* Check if we know the host and its host key. */
276: found = key_new(key->type);
277: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
278:
279: if (host_status != HOST_OK && userfile != NULL) {
280: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
281: if (options.strict_modes &&
282: (stat(user_hostfile, &st) == 0) &&
283: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 284: (st.st_mode & 022) != 0)) {
1.47 itojun 285: logit("Authentication refused for %.100s: "
1.24 markus 286: "bad owner or modes for %.200s",
287: pw->pw_name, user_hostfile);
288: } else {
289: temporarily_use_uid(pw);
290: host_status = check_host_in_hostfile(user_hostfile,
291: host, key, found, NULL);
292: restore_uid();
293: }
294: xfree(user_hostfile);
295: }
296: key_free(found);
297:
298: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
299: "ok" : "not found", host);
300: return host_status;
301: }
302:
1.22 markus 303:
304: /*
305: * Check a given file for security. This is defined as all components
1.44 stevesk 306: * of the path to the file must be owned by either the owner of
1.23 markus 307: * of the file or root and no directories must be group or world writable.
1.22 markus 308: *
309: * XXX Should any specific check be done for sym links ?
310: *
311: * Takes an open file descriptor, the file name, a uid and and
312: * error buffer plus max size as arguments.
313: *
314: * Returns 0 on success and -1 on failure
315: */
316: int
1.25 provos 317: secure_filename(FILE *f, const char *file, struct passwd *pw,
318: char *err, size_t errlen)
1.22 markus 319: {
1.25 provos 320: uid_t uid = pw->pw_uid;
1.28 markus 321: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 322: char *cp;
1.46 markus 323: int comparehome = 0;
1.22 markus 324: struct stat st;
325:
326: if (realpath(file, buf) == NULL) {
327: snprintf(err, errlen, "realpath %s failed: %s", file,
328: strerror(errno));
329: return -1;
330: }
1.46 markus 331: if (realpath(pw->pw_dir, homedir) != NULL)
332: comparehome = 1;
1.22 markus 333:
334: /* check the open file to avoid races */
335: if (fstat(fileno(f), &st) < 0 ||
336: (st.st_uid != 0 && st.st_uid != uid) ||
337: (st.st_mode & 022) != 0) {
338: snprintf(err, errlen, "bad ownership or modes for file %s",
339: buf);
340: return -1;
341: }
342:
343: /* for each component of the canonical path, walking upwards */
344: for (;;) {
345: if ((cp = dirname(buf)) == NULL) {
346: snprintf(err, errlen, "dirname() failed");
347: return -1;
348: }
349: strlcpy(buf, cp, sizeof(buf));
1.25 provos 350:
1.22 markus 351: debug3("secure_filename: checking '%s'", buf);
352: if (stat(buf, &st) < 0 ||
353: (st.st_uid != 0 && st.st_uid != uid) ||
354: (st.st_mode & 022) != 0) {
1.31 deraadt 355: snprintf(err, errlen,
1.22 markus 356: "bad ownership or modes for directory %s", buf);
357: return -1;
358: }
359:
1.27 markus 360: /* If are passed the homedir then we can stop */
1.46 markus 361: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 362: debug3("secure_filename: terminating check at '%s'",
363: buf);
364: break;
365: }
1.22 markus 366: /*
367: * dirname should always complete with a "/" path,
368: * but we can be paranoid and check for "." too
369: */
370: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
371: break;
372: }
1.17 markus 373: return 0;
1.37 provos 374: }
375:
376: struct passwd *
377: getpwnamallow(const char *user)
378: {
1.38 provos 379: #ifdef HAVE_LOGIN_CAP
380: extern login_cap_t *lc;
381: #ifdef BSD_AUTH
382: auth_session_t *as;
383: #endif
384: #endif
1.37 provos 385: struct passwd *pw;
386:
387: pw = getpwnam(user);
1.45 stevesk 388: if (pw == NULL) {
1.55 markus 389: logit("Invalid user %.100s from %.100s",
1.45 stevesk 390: user, get_remote_ipaddr());
391: return (NULL);
392: }
393: if (!allowed_user(pw))
1.38 provos 394: return (NULL);
395: #ifdef HAVE_LOGIN_CAP
396: if ((lc = login_getclass(pw->pw_class)) == NULL) {
397: debug("unable to get login class: %s", user);
398: return (NULL);
399: }
400: #ifdef BSD_AUTH
401: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 402: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 403: debug("Approval failure for %s", user);
1.37 provos 404: pw = NULL;
1.38 provos 405: }
406: if (as != NULL)
407: auth_close(as);
408: #endif
409: #endif
1.41 markus 410: if (pw != NULL)
411: return (pwcopy(pw));
412: return (NULL);
1.42 markus 413: }
414:
415: void
416: auth_debug_add(const char *fmt,...)
417: {
418: char buf[1024];
419: va_list args;
420:
421: if (!auth_debug_init)
422: return;
423:
424: va_start(args, fmt);
425: vsnprintf(buf, sizeof(buf), fmt, args);
426: va_end(args);
427: buffer_put_cstring(&auth_debug, buf);
428: }
429:
430: void
431: auth_debug_send(void)
432: {
433: char *msg;
434:
435: if (!auth_debug_init)
436: return;
437: while (buffer_len(&auth_debug)) {
438: msg = buffer_get_string(&auth_debug, NULL);
439: packet_send_debug("%s", msg);
440: xfree(msg);
441: }
442: }
443:
444: void
445: auth_debug_reset(void)
446: {
447: if (auth_debug_init)
448: buffer_clear(&auth_debug);
449: else {
450: buffer_init(&auth_debug);
451: auth_debug_init = 1;
452: }
1.49 markus 453: }
454:
455: struct passwd *
456: fakepw(void)
457: {
458: static struct passwd fake;
459:
460: memset(&fake, 0, sizeof(fake));
461: fake.pw_name = "NOUSER";
462: fake.pw_passwd =
1.51 djm 463: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 464: fake.pw_gecos = "NOUSER";
1.53 deraadt 465: fake.pw_uid = (uid_t)-1;
466: fake.pw_gid = (gid_t)-1;
1.49 markus 467: fake.pw_class = "";
468: fake.pw_dir = "/nonexist";
469: fake.pw_shell = "/nonexist";
470:
471: return (&fake);
1.1 markus 472: }
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