Annotation of src/usr.bin/ssh/auth.c, Revision 1.72
1.72 ! stevesk 1: /* $OpenBSD: auth.c,v 1.71 2006/07/12 11:34:58 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:
1.70 stevesk 31: #include <errno.h>
1.22 markus 32: #include <libgen.h>
1.61 stevesk 33: #include <paths.h>
1.68 stevesk 34: #include <pwd.h>
1.69 stevesk 35: #include <stdarg.h>
1.72 ! stevesk 36: #include <string.h>
1.1 markus 37:
38: #include "xmalloc.h"
1.13 markus 39: #include "match.h"
1.14 markus 40: #include "groupaccess.h"
41: #include "log.h"
1.1 markus 42: #include "servconf.h"
1.2 markus 43: #include "auth.h"
1.13 markus 44: #include "auth-options.h"
1.14 markus 45: #include "canohost.h"
1.22 markus 46: #include "buffer.h"
47: #include "bufaux.h"
1.24 markus 48: #include "uidswap.h"
1.40 markus 49: #include "misc.h"
1.42 markus 50: #include "bufaux.h"
51: #include "packet.h"
1.67 dtucker 52: #include "monitor_wrap.h"
1.2 markus 53:
1.1 markus 54: /* import */
55: extern ServerOptions options;
1.67 dtucker 56: extern int use_privsep;
1.1 markus 57:
1.42 markus 58: /* Debugging messages */
59: Buffer auth_debug;
60: int auth_debug_init;
61:
1.1 markus 62: /*
1.12 markus 63: * Check if the user is allowed to log in via ssh. If user is listed
64: * in DenyUsers or one of user's groups is listed in DenyGroups, false
65: * will be returned. If AllowUsers isn't empty and user isn't listed
66: * there, or if AllowGroups isn't empty and one of user's groups isn't
67: * listed there, false will be returned.
1.1 markus 68: * If the user's shell is not executable, false will be returned.
1.4 markus 69: * Otherwise true is returned.
1.1 markus 70: */
1.5 markus 71: int
1.1 markus 72: allowed_user(struct passwd * pw)
73: {
74: struct stat st;
1.35 markus 75: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 76: char *shell;
1.60 djm 77: u_int i;
1.1 markus 78:
79: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 80: if (!pw || !pw->pw_name)
1.1 markus 81: return 0;
82:
1.7 deraadt 83: /*
84: * Get the shell from the password data. An empty shell field is
85: * legal, and means /bin/sh.
86: */
87: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
88:
1.1 markus 89: /* deny if shell does not exists or is not executable */
1.34 stevesk 90: if (stat(shell, &st) != 0) {
1.47 itojun 91: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 92: pw->pw_name, shell);
1.1 markus 93: return 0;
1.34 stevesk 94: }
1.36 itojun 95: if (S_ISREG(st.st_mode) == 0 ||
96: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 97: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 98: pw->pw_name, shell);
1.1 markus 99: return 0;
1.34 stevesk 100: }
1.1 markus 101:
1.58 dtucker 102: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
103: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 104: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 105: ipaddr = get_remote_ipaddr();
106: }
107:
1.1 markus 108: /* Return false if user is listed in DenyUsers */
109: if (options.num_deny_users > 0) {
110: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 111: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 112: options.deny_users[i])) {
1.57 dtucker 113: logit("User %.100s from %.100s not allowed "
114: "because listed in DenyUsers",
115: pw->pw_name, hostname);
1.1 markus 116: return 0;
1.34 stevesk 117: }
1.1 markus 118: }
119: /* Return false if AllowUsers isn't empty and user isn't listed there */
120: if (options.num_allow_users > 0) {
121: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 122: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 123: options.allow_users[i]))
1.1 markus 124: break;
125: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 126: if (i >= options.num_allow_users) {
1.57 dtucker 127: logit("User %.100s from %.100s not allowed because "
128: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 129: return 0;
1.34 stevesk 130: }
1.1 markus 131: }
132: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 133: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 134: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 135: logit("User %.100s from %.100s not allowed because "
136: "not in any group", pw->pw_name, hostname);
1.1 markus 137: return 0;
1.34 stevesk 138: }
1.1 markus 139:
1.12 markus 140: /* Return false if one of user's groups is listed in DenyGroups */
141: if (options.num_deny_groups > 0)
142: if (ga_match(options.deny_groups,
143: options.num_deny_groups)) {
144: ga_free();
1.57 dtucker 145: logit("User %.100s from %.100s not allowed "
146: "because a group is listed in DenyGroups",
147: pw->pw_name, hostname);
1.1 markus 148: return 0;
1.12 markus 149: }
1.1 markus 150: /*
1.12 markus 151: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 152: * isn't listed there
153: */
1.12 markus 154: if (options.num_allow_groups > 0)
155: if (!ga_match(options.allow_groups,
156: options.num_allow_groups)) {
157: ga_free();
1.57 dtucker 158: logit("User %.100s from %.100s not allowed "
159: "because none of user's groups are listed "
160: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 161: return 0;
1.12 markus 162: }
163: ga_free();
1.1 markus 164: }
165: /* We found no reason not to let this user try to log on... */
166: return 1;
1.13 markus 167: }
168:
169: void
170: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
171: {
172: void (*authlog) (const char *fmt,...) = verbose;
173: char *authmsg;
1.67 dtucker 174:
175: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
176: return;
1.13 markus 177:
178: /* Raise logging level */
179: if (authenticated == 1 ||
180: !authctxt->valid ||
1.54 dtucker 181: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 182: strcmp(method, "password") == 0)
1.47 itojun 183: authlog = logit;
1.13 markus 184:
185: if (authctxt->postponed)
186: authmsg = "Postponed";
187: else
188: authmsg = authenticated ? "Accepted" : "Failed";
189:
190: authlog("%s %s for %s%.100s from %.200s port %d%s",
191: authmsg,
192: method,
1.56 markus 193: authctxt->valid ? "" : "invalid user ",
1.29 markus 194: authctxt->user,
1.13 markus 195: get_remote_ipaddr(),
196: get_remote_port(),
197: info);
198: }
199:
200: /*
1.17 markus 201: * Check whether root logins are disallowed.
1.13 markus 202: */
203: int
1.17 markus 204: auth_root_allowed(char *method)
1.13 markus 205: {
1.17 markus 206: switch (options.permit_root_login) {
207: case PERMIT_YES:
1.13 markus 208: return 1;
1.17 markus 209: case PERMIT_NO_PASSWD:
210: if (strcmp(method, "password") != 0)
211: return 1;
212: break;
213: case PERMIT_FORCED_ONLY:
214: if (forced_command) {
1.47 itojun 215: logit("Root login accepted for forced command.");
1.17 markus 216: return 1;
217: }
218: break;
1.13 markus 219: }
1.47 itojun 220: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 221: return 0;
222: }
223:
224:
225: /*
226: * Given a template and a passwd structure, build a filename
227: * by substituting % tokenised options. Currently, %% becomes '%',
228: * %h becomes the home directory and %u the username.
229: *
230: * This returns a buffer allocated by xmalloc.
231: */
1.59 djm 232: static char *
233: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 234: {
1.65 djm 235: char *file, ret[MAXPATHLEN];
236: int i;
1.22 markus 237:
1.59 djm 238: file = percent_expand(filename, "h", pw->pw_dir,
239: "u", pw->pw_name, (char *)NULL);
1.22 markus 240:
241: /*
242: * Ensure that filename starts anchored. If not, be backward
243: * compatible and prepend the '%h/'
244: */
1.59 djm 245: if (*file == '/')
246: return (file);
247:
1.65 djm 248: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
249: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 250: fatal("expand_authorized_keys: path too long");
251: xfree(file);
1.65 djm 252: return (xstrdup(ret));
1.22 markus 253: }
254:
255: char *
256: authorized_keys_file(struct passwd *pw)
257: {
1.59 djm 258: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 259: }
260:
261: char *
262: authorized_keys_file2(struct passwd *pw)
263: {
1.59 djm 264: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 265: }
1.24 markus 266:
267: /* return ok if key exists in sysfile or userfile */
268: HostStatus
269: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
270: const char *sysfile, const char *userfile)
271: {
272: Key *found;
273: char *user_hostfile;
274: struct stat st;
1.30 stevesk 275: HostStatus host_status;
1.24 markus 276:
277: /* Check if we know the host and its host key. */
278: found = key_new(key->type);
279: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
280:
281: if (host_status != HOST_OK && userfile != NULL) {
282: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
283: if (options.strict_modes &&
284: (stat(user_hostfile, &st) == 0) &&
285: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 286: (st.st_mode & 022) != 0)) {
1.47 itojun 287: logit("Authentication refused for %.100s: "
1.24 markus 288: "bad owner or modes for %.200s",
289: pw->pw_name, user_hostfile);
290: } else {
291: temporarily_use_uid(pw);
292: host_status = check_host_in_hostfile(user_hostfile,
293: host, key, found, NULL);
294: restore_uid();
295: }
296: xfree(user_hostfile);
297: }
298: key_free(found);
299:
300: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
301: "ok" : "not found", host);
302: return host_status;
303: }
304:
1.22 markus 305:
306: /*
307: * Check a given file for security. This is defined as all components
1.44 stevesk 308: * of the path to the file must be owned by either the owner of
1.23 markus 309: * of the file or root and no directories must be group or world writable.
1.22 markus 310: *
311: * XXX Should any specific check be done for sym links ?
312: *
313: * Takes an open file descriptor, the file name, a uid and and
314: * error buffer plus max size as arguments.
315: *
316: * Returns 0 on success and -1 on failure
317: */
318: int
1.25 provos 319: secure_filename(FILE *f, const char *file, struct passwd *pw,
320: char *err, size_t errlen)
1.22 markus 321: {
1.25 provos 322: uid_t uid = pw->pw_uid;
1.28 markus 323: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 324: char *cp;
1.46 markus 325: int comparehome = 0;
1.22 markus 326: struct stat st;
327:
328: if (realpath(file, buf) == NULL) {
329: snprintf(err, errlen, "realpath %s failed: %s", file,
330: strerror(errno));
331: return -1;
332: }
1.46 markus 333: if (realpath(pw->pw_dir, homedir) != NULL)
334: comparehome = 1;
1.22 markus 335:
336: /* check the open file to avoid races */
337: if (fstat(fileno(f), &st) < 0 ||
338: (st.st_uid != 0 && st.st_uid != uid) ||
339: (st.st_mode & 022) != 0) {
340: snprintf(err, errlen, "bad ownership or modes for file %s",
341: buf);
342: return -1;
343: }
344:
345: /* for each component of the canonical path, walking upwards */
346: for (;;) {
347: if ((cp = dirname(buf)) == NULL) {
348: snprintf(err, errlen, "dirname() failed");
349: return -1;
350: }
351: strlcpy(buf, cp, sizeof(buf));
1.25 provos 352:
1.22 markus 353: debug3("secure_filename: checking '%s'", buf);
354: if (stat(buf, &st) < 0 ||
355: (st.st_uid != 0 && st.st_uid != uid) ||
356: (st.st_mode & 022) != 0) {
1.31 deraadt 357: snprintf(err, errlen,
1.22 markus 358: "bad ownership or modes for directory %s", buf);
359: return -1;
360: }
361:
1.27 markus 362: /* If are passed the homedir then we can stop */
1.46 markus 363: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 364: debug3("secure_filename: terminating check at '%s'",
365: buf);
366: break;
367: }
1.22 markus 368: /*
369: * dirname should always complete with a "/" path,
370: * but we can be paranoid and check for "." too
371: */
372: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
373: break;
374: }
1.17 markus 375: return 0;
1.37 provos 376: }
377:
378: struct passwd *
379: getpwnamallow(const char *user)
380: {
1.38 provos 381: #ifdef HAVE_LOGIN_CAP
382: extern login_cap_t *lc;
383: #ifdef BSD_AUTH
384: auth_session_t *as;
385: #endif
386: #endif
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: #ifdef HAVE_LOGIN_CAP
401: if ((lc = login_getclass(pw->pw_class)) == NULL) {
402: debug("unable to get login class: %s", user);
403: return (NULL);
404: }
405: #ifdef BSD_AUTH
406: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 407: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 408: debug("Approval failure for %s", user);
1.37 provos 409: pw = NULL;
1.38 provos 410: }
411: if (as != NULL)
412: auth_close(as);
413: #endif
414: #endif
1.41 markus 415: if (pw != NULL)
416: return (pwcopy(pw));
417: return (NULL);
1.42 markus 418: }
419:
420: void
421: auth_debug_add(const char *fmt,...)
422: {
423: char buf[1024];
424: va_list args;
425:
426: if (!auth_debug_init)
427: return;
428:
429: va_start(args, fmt);
430: vsnprintf(buf, sizeof(buf), fmt, args);
431: va_end(args);
432: buffer_put_cstring(&auth_debug, buf);
433: }
434:
435: void
436: auth_debug_send(void)
437: {
438: char *msg;
439:
440: if (!auth_debug_init)
441: return;
442: while (buffer_len(&auth_debug)) {
443: msg = buffer_get_string(&auth_debug, NULL);
444: packet_send_debug("%s", msg);
445: xfree(msg);
446: }
447: }
448:
449: void
450: auth_debug_reset(void)
451: {
452: if (auth_debug_init)
453: buffer_clear(&auth_debug);
454: else {
455: buffer_init(&auth_debug);
456: auth_debug_init = 1;
457: }
1.49 markus 458: }
459:
460: struct passwd *
461: fakepw(void)
462: {
463: static struct passwd fake;
464:
465: memset(&fake, 0, sizeof(fake));
466: fake.pw_name = "NOUSER";
467: fake.pw_passwd =
1.51 djm 468: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 469: fake.pw_gecos = "NOUSER";
1.53 deraadt 470: fake.pw_uid = (uid_t)-1;
471: fake.pw_gid = (gid_t)-1;
1.49 markus 472: fake.pw_class = "";
473: fake.pw_dir = "/nonexist";
474: fake.pw_shell = "/nonexist";
475:
476: return (&fake);
1.1 markus 477: }
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