Annotation of src/usr.bin/ssh/auth.c, Revision 1.73
1.73 ! stevesk 1: /* $OpenBSD: auth.c,v 1.72 2006/07/22 20:48:22 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>
1.73 ! stevesk 30: #include <sys/param.h>
1.22 markus 31:
1.70 stevesk 32: #include <errno.h>
1.22 markus 33: #include <libgen.h>
1.61 stevesk 34: #include <paths.h>
1.68 stevesk 35: #include <pwd.h>
1.69 stevesk 36: #include <stdarg.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"
1.1 markus 43: #include "servconf.h"
1.2 markus 44: #include "auth.h"
1.13 markus 45: #include "auth-options.h"
1.14 markus 46: #include "canohost.h"
1.22 markus 47: #include "buffer.h"
48: #include "bufaux.h"
1.24 markus 49: #include "uidswap.h"
1.40 markus 50: #include "misc.h"
1.42 markus 51: #include "bufaux.h"
52: #include "packet.h"
1.67 dtucker 53: #include "monitor_wrap.h"
1.2 markus 54:
1.1 markus 55: /* import */
56: extern ServerOptions options;
1.67 dtucker 57: extern int use_privsep;
1.1 markus 58:
1.42 markus 59: /* Debugging messages */
60: Buffer auth_debug;
61: int auth_debug_init;
62:
1.1 markus 63: /*
1.12 markus 64: * Check if the user is allowed to log in via ssh. If user is listed
65: * in DenyUsers or one of user's groups is listed in DenyGroups, false
66: * will be returned. If AllowUsers isn't empty and user isn't listed
67: * there, or if AllowGroups isn't empty and one of user's groups isn't
68: * listed there, false will be returned.
1.1 markus 69: * If the user's shell is not executable, false will be returned.
1.4 markus 70: * Otherwise true is returned.
1.1 markus 71: */
1.5 markus 72: int
1.1 markus 73: allowed_user(struct passwd * pw)
74: {
75: struct stat st;
1.35 markus 76: const char *hostname = NULL, *ipaddr = NULL;
1.21 markus 77: char *shell;
1.60 djm 78: u_int i;
1.1 markus 79:
80: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 81: if (!pw || !pw->pw_name)
1.1 markus 82: return 0;
83:
1.7 deraadt 84: /*
85: * Get the shell from the password data. An empty shell field is
86: * legal, and means /bin/sh.
87: */
88: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
89:
1.1 markus 90: /* deny if shell does not exists or is not executable */
1.34 stevesk 91: if (stat(shell, &st) != 0) {
1.47 itojun 92: logit("User %.100s not allowed because shell %.100s does not exist",
1.34 stevesk 93: pw->pw_name, shell);
1.1 markus 94: return 0;
1.34 stevesk 95: }
1.36 itojun 96: if (S_ISREG(st.st_mode) == 0 ||
97: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
1.47 itojun 98: logit("User %.100s not allowed because shell %.100s is not executable",
1.34 stevesk 99: pw->pw_name, shell);
1.1 markus 100: return 0;
1.34 stevesk 101: }
1.1 markus 102:
1.58 dtucker 103: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
104: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.48 markus 105: hostname = get_canonical_hostname(options.use_dns);
1.35 markus 106: ipaddr = get_remote_ipaddr();
107: }
108:
1.1 markus 109: /* Return false if user is listed in DenyUsers */
110: if (options.num_deny_users > 0) {
111: for (i = 0; i < options.num_deny_users; i++)
1.39 markus 112: if (match_user(pw->pw_name, hostname, ipaddr,
1.34 stevesk 113: options.deny_users[i])) {
1.57 dtucker 114: logit("User %.100s from %.100s not allowed "
115: "because listed in DenyUsers",
116: pw->pw_name, hostname);
1.1 markus 117: return 0;
1.34 stevesk 118: }
1.1 markus 119: }
120: /* Return false if AllowUsers isn't empty and user isn't listed there */
121: if (options.num_allow_users > 0) {
122: for (i = 0; i < options.num_allow_users; i++)
1.39 markus 123: if (match_user(pw->pw_name, hostname, ipaddr,
1.26 markus 124: options.allow_users[i]))
1.1 markus 125: break;
126: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 127: if (i >= options.num_allow_users) {
1.57 dtucker 128: logit("User %.100s from %.100s not allowed because "
129: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 130: return 0;
1.34 stevesk 131: }
1.1 markus 132: }
133: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 134: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 135: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 136: logit("User %.100s from %.100s not allowed because "
137: "not in any group", pw->pw_name, hostname);
1.1 markus 138: return 0;
1.34 stevesk 139: }
1.1 markus 140:
1.12 markus 141: /* Return false if one of user's groups is listed in DenyGroups */
142: if (options.num_deny_groups > 0)
143: if (ga_match(options.deny_groups,
144: options.num_deny_groups)) {
145: ga_free();
1.57 dtucker 146: logit("User %.100s from %.100s not allowed "
147: "because a group is listed in DenyGroups",
148: pw->pw_name, hostname);
1.1 markus 149: return 0;
1.12 markus 150: }
1.1 markus 151: /*
1.12 markus 152: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 153: * isn't listed there
154: */
1.12 markus 155: if (options.num_allow_groups > 0)
156: if (!ga_match(options.allow_groups,
157: options.num_allow_groups)) {
158: ga_free();
1.57 dtucker 159: logit("User %.100s from %.100s not allowed "
160: "because none of user's groups are listed "
161: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 162: return 0;
1.12 markus 163: }
164: ga_free();
1.1 markus 165: }
166: /* We found no reason not to let this user try to log on... */
167: return 1;
1.13 markus 168: }
169:
170: void
171: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
172: {
173: void (*authlog) (const char *fmt,...) = verbose;
174: char *authmsg;
1.67 dtucker 175:
176: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
177: return;
1.13 markus 178:
179: /* Raise logging level */
180: if (authenticated == 1 ||
181: !authctxt->valid ||
1.54 dtucker 182: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 183: strcmp(method, "password") == 0)
1.47 itojun 184: authlog = logit;
1.13 markus 185:
186: if (authctxt->postponed)
187: authmsg = "Postponed";
188: else
189: authmsg = authenticated ? "Accepted" : "Failed";
190:
191: authlog("%s %s for %s%.100s from %.200s port %d%s",
192: authmsg,
193: method,
1.56 markus 194: authctxt->valid ? "" : "invalid user ",
1.29 markus 195: authctxt->user,
1.13 markus 196: get_remote_ipaddr(),
197: get_remote_port(),
198: info);
199: }
200:
201: /*
1.17 markus 202: * Check whether root logins are disallowed.
1.13 markus 203: */
204: int
1.17 markus 205: auth_root_allowed(char *method)
1.13 markus 206: {
1.17 markus 207: switch (options.permit_root_login) {
208: case PERMIT_YES:
1.13 markus 209: return 1;
1.17 markus 210: case PERMIT_NO_PASSWD:
211: if (strcmp(method, "password") != 0)
212: return 1;
213: break;
214: case PERMIT_FORCED_ONLY:
215: if (forced_command) {
1.47 itojun 216: logit("Root login accepted for forced command.");
1.17 markus 217: return 1;
218: }
219: break;
1.13 markus 220: }
1.47 itojun 221: logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 222: return 0;
223: }
224:
225:
226: /*
227: * Given a template and a passwd structure, build a filename
228: * by substituting % tokenised options. Currently, %% becomes '%',
229: * %h becomes the home directory and %u the username.
230: *
231: * This returns a buffer allocated by xmalloc.
232: */
1.59 djm 233: static char *
234: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 235: {
1.65 djm 236: char *file, ret[MAXPATHLEN];
237: int i;
1.22 markus 238:
1.59 djm 239: file = percent_expand(filename, "h", pw->pw_dir,
240: "u", pw->pw_name, (char *)NULL);
1.22 markus 241:
242: /*
243: * Ensure that filename starts anchored. If not, be backward
244: * compatible and prepend the '%h/'
245: */
1.59 djm 246: if (*file == '/')
247: return (file);
248:
1.65 djm 249: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
250: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 251: fatal("expand_authorized_keys: path too long");
252: xfree(file);
1.65 djm 253: return (xstrdup(ret));
1.22 markus 254: }
255:
256: char *
257: authorized_keys_file(struct passwd *pw)
258: {
1.59 djm 259: return expand_authorized_keys(options.authorized_keys_file, pw);
1.22 markus 260: }
261:
262: char *
263: authorized_keys_file2(struct passwd *pw)
264: {
1.59 djm 265: return expand_authorized_keys(options.authorized_keys_file2, pw);
1.22 markus 266: }
1.24 markus 267:
268: /* return ok if key exists in sysfile or userfile */
269: HostStatus
270: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
271: const char *sysfile, const char *userfile)
272: {
273: Key *found;
274: char *user_hostfile;
275: struct stat st;
1.30 stevesk 276: HostStatus host_status;
1.24 markus 277:
278: /* Check if we know the host and its host key. */
279: found = key_new(key->type);
280: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
281:
282: if (host_status != HOST_OK && userfile != NULL) {
283: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
284: if (options.strict_modes &&
285: (stat(user_hostfile, &st) == 0) &&
286: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 287: (st.st_mode & 022) != 0)) {
1.47 itojun 288: logit("Authentication refused for %.100s: "
1.24 markus 289: "bad owner or modes for %.200s",
290: pw->pw_name, user_hostfile);
291: } else {
292: temporarily_use_uid(pw);
293: host_status = check_host_in_hostfile(user_hostfile,
294: host, key, found, NULL);
295: restore_uid();
296: }
297: xfree(user_hostfile);
298: }
299: key_free(found);
300:
301: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
302: "ok" : "not found", host);
303: return host_status;
304: }
305:
1.22 markus 306:
307: /*
308: * Check a given file for security. This is defined as all components
1.44 stevesk 309: * of the path to the file must be owned by either the owner of
1.23 markus 310: * of the file or root and no directories must be group or world writable.
1.22 markus 311: *
312: * XXX Should any specific check be done for sym links ?
313: *
314: * Takes an open file descriptor, the file name, a uid and and
315: * error buffer plus max size as arguments.
316: *
317: * Returns 0 on success and -1 on failure
318: */
319: int
1.25 provos 320: secure_filename(FILE *f, const char *file, struct passwd *pw,
321: char *err, size_t errlen)
1.22 markus 322: {
1.25 provos 323: uid_t uid = pw->pw_uid;
1.28 markus 324: char buf[MAXPATHLEN], homedir[MAXPATHLEN];
1.22 markus 325: char *cp;
1.46 markus 326: int comparehome = 0;
1.22 markus 327: struct stat st;
328:
329: if (realpath(file, buf) == NULL) {
330: snprintf(err, errlen, "realpath %s failed: %s", file,
331: strerror(errno));
332: return -1;
333: }
1.46 markus 334: if (realpath(pw->pw_dir, homedir) != NULL)
335: comparehome = 1;
1.22 markus 336:
337: /* check the open file to avoid races */
338: if (fstat(fileno(f), &st) < 0 ||
339: (st.st_uid != 0 && st.st_uid != uid) ||
340: (st.st_mode & 022) != 0) {
341: snprintf(err, errlen, "bad ownership or modes for file %s",
342: buf);
343: return -1;
344: }
345:
346: /* for each component of the canonical path, walking upwards */
347: for (;;) {
348: if ((cp = dirname(buf)) == NULL) {
349: snprintf(err, errlen, "dirname() failed");
350: return -1;
351: }
352: strlcpy(buf, cp, sizeof(buf));
1.25 provos 353:
1.22 markus 354: debug3("secure_filename: checking '%s'", buf);
355: if (stat(buf, &st) < 0 ||
356: (st.st_uid != 0 && st.st_uid != uid) ||
357: (st.st_mode & 022) != 0) {
1.31 deraadt 358: snprintf(err, errlen,
1.22 markus 359: "bad ownership or modes for directory %s", buf);
360: return -1;
361: }
362:
1.27 markus 363: /* If are passed the homedir then we can stop */
1.46 markus 364: if (comparehome && strcmp(homedir, buf) == 0) {
1.27 markus 365: debug3("secure_filename: terminating check at '%s'",
366: buf);
367: break;
368: }
1.22 markus 369: /*
370: * dirname should always complete with a "/" path,
371: * but we can be paranoid and check for "." too
372: */
373: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
374: break;
375: }
1.17 markus 376: return 0;
1.37 provos 377: }
378:
379: struct passwd *
380: getpwnamallow(const char *user)
381: {
1.38 provos 382: #ifdef HAVE_LOGIN_CAP
383: extern login_cap_t *lc;
384: #ifdef BSD_AUTH
385: auth_session_t *as;
386: #endif
387: #endif
1.37 provos 388: struct passwd *pw;
1.71 dtucker 389:
390: parse_server_match_config(&options, user,
391: get_canonical_hostname(options.use_dns), get_remote_ipaddr());
1.37 provos 392:
393: pw = getpwnam(user);
1.45 stevesk 394: if (pw == NULL) {
1.55 markus 395: logit("Invalid user %.100s from %.100s",
1.45 stevesk 396: user, get_remote_ipaddr());
397: return (NULL);
398: }
399: if (!allowed_user(pw))
1.38 provos 400: return (NULL);
401: #ifdef HAVE_LOGIN_CAP
402: if ((lc = login_getclass(pw->pw_class)) == NULL) {
403: debug("unable to get login class: %s", user);
404: return (NULL);
405: }
406: #ifdef BSD_AUTH
407: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 408: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 409: debug("Approval failure for %s", user);
1.37 provos 410: pw = NULL;
1.38 provos 411: }
412: if (as != NULL)
413: auth_close(as);
414: #endif
415: #endif
1.41 markus 416: if (pw != NULL)
417: return (pwcopy(pw));
418: return (NULL);
1.42 markus 419: }
420:
421: void
422: auth_debug_add(const char *fmt,...)
423: {
424: char buf[1024];
425: va_list args;
426:
427: if (!auth_debug_init)
428: return;
429:
430: va_start(args, fmt);
431: vsnprintf(buf, sizeof(buf), fmt, args);
432: va_end(args);
433: buffer_put_cstring(&auth_debug, buf);
434: }
435:
436: void
437: auth_debug_send(void)
438: {
439: char *msg;
440:
441: if (!auth_debug_init)
442: return;
443: while (buffer_len(&auth_debug)) {
444: msg = buffer_get_string(&auth_debug, NULL);
445: packet_send_debug("%s", msg);
446: xfree(msg);
447: }
448: }
449:
450: void
451: auth_debug_reset(void)
452: {
453: if (auth_debug_init)
454: buffer_clear(&auth_debug);
455: else {
456: buffer_init(&auth_debug);
457: auth_debug_init = 1;
458: }
1.49 markus 459: }
460:
461: struct passwd *
462: fakepw(void)
463: {
464: static struct passwd fake;
465:
466: memset(&fake, 0, sizeof(fake));
467: fake.pw_name = "NOUSER";
468: fake.pw_passwd =
1.51 djm 469: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 470: fake.pw_gecos = "NOUSER";
1.53 deraadt 471: fake.pw_uid = (uid_t)-1;
472: fake.pw_gid = (gid_t)-1;
1.49 markus 473: fake.pw_class = "";
474: fake.pw_dir = "/nonexist";
475: fake.pw_shell = "/nonexist";
476:
477: return (&fake);
1.1 markus 478: }
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