Annotation of src/usr.bin/ssh/auth.c, Revision 1.78
1.78 ! djm 1: /* $OpenBSD: auth.c,v 1.77 2007/08/23 02:55:51 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>
1.22 markus 31: #include <libgen.h>
1.77 djm 32: #include <login_cap.h>
1.61 stevesk 33: #include <paths.h>
1.68 stevesk 34: #include <pwd.h>
1.69 stevesk 35: #include <stdarg.h>
1.74 stevesk 36: #include <stdio.h>
1.72 stevesk 37: #include <string.h>
1.1 markus 38:
39: #include "xmalloc.h"
1.13 markus 40: #include "match.h"
1.14 markus 41: #include "groupaccess.h"
42: #include "log.h"
1.75 deraadt 43: #include "buffer.h"
1.1 markus 44: #include "servconf.h"
1.75 deraadt 45: #include "key.h"
46: #include "hostfile.h"
1.2 markus 47: #include "auth.h"
1.13 markus 48: #include "auth-options.h"
1.14 markus 49: #include "canohost.h"
1.24 markus 50: #include "uidswap.h"
1.40 markus 51: #include "misc.h"
1.42 markus 52: #include "packet.h"
1.75 deraadt 53: #ifdef GSSAPI
54: #include "ssh-gss.h"
55: #endif
1.67 dtucker 56: #include "monitor_wrap.h"
1.2 markus 57:
1.1 markus 58: /* import */
59: extern ServerOptions options;
1.67 dtucker 60: extern int use_privsep;
1.1 markus 61:
1.42 markus 62: /* Debugging messages */
63: Buffer auth_debug;
64: int auth_debug_init;
65:
1.1 markus 66: /*
1.12 markus 67: * Check if the user is allowed to log in via ssh. If user is listed
68: * in DenyUsers or one of user's groups is listed in DenyGroups, false
69: * will be returned. If AllowUsers isn't empty and user isn't listed
70: * there, or if AllowGroups isn't empty and one of user's groups isn't
71: * listed there, false will be returned.
1.1 markus 72: * If the user's shell is not executable, false will be returned.
1.4 markus 73: * Otherwise true is returned.
1.1 markus 74: */
1.5 markus 75: int
1.1 markus 76: allowed_user(struct passwd * pw)
77: {
78: struct stat st;
1.35 markus 79: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 80: char *shell;
1.60 djm 81: u_int i;
1.1 markus 82:
83: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 84: if (!pw || !pw->pw_name)
1.1 markus 85: return 0;
86:
1.7 deraadt 87: /*
88: * Get the shell from the password data. An empty shell field is
89: * legal, and means /bin/sh.
90: */
91: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
92:
1.1 markus 93: /* deny if shell does not exists or is not executable */
1.34 stevesk 94: if (stat(shell, &st) != 0) {
1.47 itojun 95: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 96: pw->pw_name, shell);
1.1 markus 97: return 0;
1.34 stevesk 98: }
1.36 itojun 99: if (S_ISREG(st.st_mode) == 0 ||
100: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 101: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 102: pw->pw_name, shell);
1.1 markus 103: return 0;
1.34 stevesk 104: }
1.1 markus 105:
1.58 dtucker 106: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
107: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 108: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 109: ipaddr = get_remote_ipaddr();
110: }
111:
1.1 markus 112: /* Return false if user is listed in DenyUsers */
113: if (options.num_deny_users > 0) {
114: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 115: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 116: options.deny_users[i])) {
1.57 dtucker 117: logit("User %.100s from %.100s not allowed "
118: "because listed in DenyUsers",
119: pw->pw_name, hostname);
1.1 markus 120: return 0;
1.34 stevesk 121: }
1.1 markus 122: }
123: /* Return false if AllowUsers isn't empty and user isn't listed there */
124: if (options.num_allow_users > 0) {
125: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 126: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 127: options.allow_users[i]))
1.1 markus 128: break;
129: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 130: if (i >= options.num_allow_users) {
1.57 dtucker 131: logit("User %.100s from %.100s not allowed because "
132: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 133: return 0;
1.34 stevesk 134: }
1.1 markus 135: }
136: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 137: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 138: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 139: logit("User %.100s from %.100s not allowed because "
140: "not in any group", pw->pw_name, hostname);
1.1 markus 141: return 0;
1.34 stevesk 142: }
1.1 markus 143:
1.12 markus 144: /* Return false if one of user's groups is listed in DenyGroups */
145: if (options.num_deny_groups > 0)
146: if (ga_match(options.deny_groups,
147: options.num_deny_groups)) {
148: ga_free();
1.57 dtucker 149: logit("User %.100s from %.100s not allowed "
150: "because a group is listed in DenyGroups",
151: pw->pw_name, hostname);
1.1 markus 152: return 0;
1.12 markus 153: }
1.1 markus 154: /*
1.12 markus 155: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 156: * isn't listed there
157: */
1.12 markus 158: if (options.num_allow_groups > 0)
159: if (!ga_match(options.allow_groups,
160: options.num_allow_groups)) {
161: ga_free();
1.57 dtucker 162: logit("User %.100s from %.100s not allowed "
163: "because none of user's groups are listed "
164: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 165: return 0;
1.12 markus 166: }
167: ga_free();
1.1 markus 168: }
169: /* We found no reason not to let this user try to log on... */
170: return 1;
1.13 markus 171: }
172:
173: void
174: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
175: {
176: void (*authlog) (const char *fmt,...) = verbose;
177: char *authmsg;
1.67 dtucker 178:
179: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
180: return;
1.13 markus 181:
182: /* Raise logging level */
183: if (authenticated == 1 ||
184: !authctxt->valid ||
1.54 dtucker 185: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 186: strcmp(method, "password") == 0)
1.47 itojun 187: authlog = logit;
1.13 markus 188:
189: if (authctxt->postponed)
190: authmsg = "Postponed";
191: else
192: authmsg = authenticated ? "Accepted" : "Failed";
193:
194: authlog("%s %s for %s%.100s from %.200s port %d%s",
195: authmsg,
196: method,
1.56 markus 197: authctxt->valid ? "" : "invalid user ",
1.29 markus 198: authctxt->user,
1.13 markus 199: get_remote_ipaddr(),
200: get_remote_port(),
201: info);
202: }
203:
204: /*
1.17 markus 205: * Check whether root logins are disallowed.
1.13 markus 206: */
207: int
1.17 markus 208: auth_root_allowed(char *method)
1.13 markus 209: {
1.17 markus 210: switch (options.permit_root_login) {
211: case PERMIT_YES:
1.13 markus 212: return 1;
1.17 markus 213: case PERMIT_NO_PASSWD:
214: if (strcmp(method, "password") != 0)
215: return 1;
216: break;
217: case PERMIT_FORCED_ONLY:
218: if (forced_command) {
1.47 itojun 219: logit("Root login accepted for forced command.");
1.17 markus 220: return 1;
221: }
222: break;
1.13 markus 223: }
1.47 itojun 224: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 225: return 0;
226: }
227:
228:
229: /*
230: * Given a template and a passwd structure, build a filename
231: * by substituting % tokenised options. Currently, %% becomes '%',
232: * %h becomes the home directory and %u the username.
233: *
234: * This returns a buffer allocated by xmalloc.
235: */
1.59 djm 236: static char *
237: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 238: {
1.65 djm 239: char *file, ret[MAXPATHLEN];
240: int i;
1.22 markus 241:
1.59 djm 242: file = percent_expand(filename, "h", pw->pw_dir,
243: "u", pw->pw_name, (char *)NULL);
1.22 markus 244:
245: /*
246: * Ensure that filename starts anchored. If not, be backward
247: * compatible and prepend the '%h/'
248: */
1.59 djm 249: if (*file == '/')
250: return (file);
251:
1.65 djm 252: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
253: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 254: fatal("expand_authorized_keys: path too long");
255: xfree(file);
1.65 djm 256: return (xstrdup(ret));
1.22 markus 257: }
258:
259: char *
260: authorized_keys_file(struct passwd *pw)
261: {
1.59 djm 262: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 263: }
264:
265: char *
266: authorized_keys_file2(struct passwd *pw)
267: {
1.59 djm 268: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 269: }
1.24 markus 270:
271: /* return ok if key exists in sysfile or userfile */
272: HostStatus
273: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
274: const char *sysfile, const char *userfile)
275: {
276: Key *found;
277: char *user_hostfile;
278: struct stat st;
1.30 stevesk 279: HostStatus host_status;
1.24 markus 280:
281: /* Check if we know the host and its host key. */
282: found = key_new(key->type);
283: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
284:
285: if (host_status != HOST_OK && userfile != NULL) {
286: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
287: if (options.strict_modes &&
288: (stat(user_hostfile, &st) == 0) &&
289: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 290: (st.st_mode & 022) != 0)) {
1.47 itojun 291: logit("Authentication refused for %.100s: "
1.24 markus 292: "bad owner or modes for %.200s",
293: pw->pw_name, user_hostfile);
294: } else {
295: temporarily_use_uid(pw);
296: host_status = check_host_in_hostfile(user_hostfile,
297: host, key, found, NULL);
298: restore_uid();
299: }
300: xfree(user_hostfile);
301: }
302: key_free(found);
303:
304: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
305: "ok" : "not found", host);
306: return host_status;
307: }
308:
1.22 markus 309:
310: /*
311: * Check a given file for security. This is defined as all components
1.44 stevesk 312: * of the path to the file must be owned by either the owner of
1.23 markus 313: * of the file or root and no directories must be group or world writable.
1.22 markus 314: *
315: * XXX Should any specific check be done for sym links ?
316: *
317: * Takes an open file descriptor, the file name, a uid and and
318: * error buffer plus max size as arguments.
319: *
320: * Returns 0 on success and -1 on failure
321: */
322: int
1.25 provos 323: secure_filename(FILE *f, const char *file, struct passwd *pw,
324: char *err, size_t errlen)
1.22 markus 325: {
1.25 provos 326: uid_t uid = pw->pw_uid;
1.28 markus 327: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 328: char *cp;
1.46 markus 329: int comparehome = 0;
1.22 markus 330: struct stat st;
331:
332: if (realpath(file, buf) == NULL) {
333: snprintf(err, errlen, "realpath %s failed: %s", file,
334: strerror(errno));
335: return -1;
336: }
1.46 markus 337: if (realpath(pw->pw_dir, homedir) != NULL)
338: comparehome = 1;
1.22 markus 339:
340: /* check the open file to avoid races */
341: if (fstat(fileno(f), &st) < 0 ||
342: (st.st_uid != 0 && st.st_uid != uid) ||
343: (st.st_mode & 022) != 0) {
344: snprintf(err, errlen, "bad ownership or modes for file %s",
345: buf);
346: return -1;
347: }
348:
349: /* for each component of the canonical path, walking upwards */
350: for (;;) {
351: if ((cp = dirname(buf)) == NULL) {
352: snprintf(err, errlen, "dirname() failed");
353: return -1;
354: }
355: strlcpy(buf, cp, sizeof(buf));
1.25 provos 356:
1.22 markus 357: debug3("secure_filename: checking '%s'", buf);
358: if (stat(buf, &st) < 0 ||
359: (st.st_uid != 0 && st.st_uid != uid) ||
360: (st.st_mode & 022) != 0) {
1.31 deraadt 361: snprintf(err, errlen,
1.22 markus 362: "bad ownership or modes for directory %s", buf);
363: return -1;
364: }
365:
1.27 markus 366: /* If are passed the homedir then we can stop */
1.46 markus 367: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 368: debug3("secure_filename: terminating check at '%s'",
369: buf);
370: break;
371: }
1.22 markus 372: /*
373: * dirname should always complete with a "/" path,
374: * but we can be paranoid and check for "." too
375: */
376: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
377: break;
378: }
1.17 markus 379: return 0;
1.37 provos 380: }
381:
382: struct passwd *
383: getpwnamallow(const char *user)
384: {
1.38 provos 385: extern login_cap_t *lc;
386: auth_session_t *as;
1.37 provos 387: struct passwd *pw;
1.71 dtucker 388:
389: parse_server_match_config(&options, user,
390: get_canonical_hostname(options.use_dns), get_remote_ipaddr());
1.37 provos 391:
392: pw = getpwnam(user);
1.45 stevesk 393: if (pw == NULL) {
1.55 markus 394: logit("Invalid user %.100s from %.100s",
1.45 stevesk 395: user, get_remote_ipaddr());
396: return (NULL);
397: }
398: if (!allowed_user(pw))
1.38 provos 399: return (NULL);
400: if ((lc = login_getclass(pw->pw_class)) == NULL) {
401: debug("unable to get login class: %s", user);
402: return (NULL);
403: }
404: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 405: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 406: debug("Approval failure for %s", user);
1.37 provos 407: pw = NULL;
1.38 provos 408: }
409: if (as != NULL)
410: auth_close(as);
1.41 markus 411: if (pw != NULL)
412: return (pwcopy(pw));
413: return (NULL);
1.42 markus 414: }
415:
416: void
417: auth_debug_add(const char *fmt,...)
418: {
419: char buf[1024];
420: va_list args;
421:
422: if (!auth_debug_init)
423: return;
424:
425: va_start(args, fmt);
426: vsnprintf(buf, sizeof(buf), fmt, args);
427: va_end(args);
428: buffer_put_cstring(&auth_debug, buf);
429: }
430:
431: void
432: auth_debug_send(void)
433: {
434: char *msg;
435:
436: if (!auth_debug_init)
437: return;
438: while (buffer_len(&auth_debug)) {
439: msg = buffer_get_string(&auth_debug, NULL);
440: packet_send_debug("%s", msg);
441: xfree(msg);
442: }
443: }
444:
445: void
446: auth_debug_reset(void)
447: {
448: if (auth_debug_init)
449: buffer_clear(&auth_debug);
450: else {
451: buffer_init(&auth_debug);
452: auth_debug_init = 1;
453: }
1.49 markus 454: }
455:
456: struct passwd *
457: fakepw(void)
458: {
459: static struct passwd fake;
460:
461: memset(&fake, 0, sizeof(fake));
462: fake.pw_name = "NOUSER";
463: fake.pw_passwd =
1.51 djm 464: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 465: fake.pw_gecos = "NOUSER";
1.53 deraadt 466: fake.pw_uid = (uid_t)-1;
467: fake.pw_gid = (gid_t)-1;
1.49 markus 468: fake.pw_class = "";
469: fake.pw_dir = "/nonexist";
470: fake.pw_shell = "/nonexist";
471:
472: return (&fake);
1.1 markus 473: }
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