Annotation of src/usr.bin/ssh/auth.c, Revision 1.147
1.147 ! djm 1: /* $OpenBSD: auth.c,v 1.146 2020/01/31 22:42:45 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>
1.114 djm 28: #include <sys/socket.h>
1.125 markus 29: #include <sys/wait.h>
1.22 markus 30:
1.140 djm 31: #include <stdlib.h>
1.70 stevesk 32: #include <errno.h>
1.79 dtucker 33: #include <fcntl.h>
1.77 djm 34: #include <login_cap.h>
1.61 stevesk 35: #include <paths.h>
1.68 stevesk 36: #include <pwd.h>
1.69 stevesk 37: #include <stdarg.h>
1.74 stevesk 38: #include <stdio.h>
1.72 stevesk 39: #include <string.h>
1.80 djm 40: #include <unistd.h>
1.109 deraadt 41: #include <limits.h>
1.114 djm 42: #include <netdb.h>
1.135 djm 43: #include <time.h>
1.1 markus 44:
45: #include "xmalloc.h"
1.13 markus 46: #include "match.h"
1.14 markus 47: #include "groupaccess.h"
48: #include "log.h"
1.131 markus 49: #include "sshbuf.h"
1.106 millert 50: #include "misc.h"
1.1 markus 51: #include "servconf.h"
1.131 markus 52: #include "sshkey.h"
1.75 deraadt 53: #include "hostfile.h"
1.2 markus 54: #include "auth.h"
1.13 markus 55: #include "auth-options.h"
1.14 markus 56: #include "canohost.h"
1.24 markus 57: #include "uidswap.h"
1.42 markus 58: #include "packet.h"
1.75 deraadt 59: #ifdef GSSAPI
60: #include "ssh-gss.h"
61: #endif
1.85 djm 62: #include "authfile.h"
1.67 dtucker 63: #include "monitor_wrap.h"
1.107 djm 64: #include "ssherr.h"
1.103 djm 65: #include "compat.h"
1.126 djm 66: #include "channels.h"
1.136 djm 67:
1.1 markus 68: /* import */
69: extern ServerOptions options;
1.146 djm 70: extern struct include_list includes;
1.67 dtucker 71: extern int use_privsep;
1.126 djm 72: extern struct sshauthopt *auth_opts;
1.1 markus 73:
1.42 markus 74: /* Debugging messages */
1.131 markus 75: static struct sshbuf *auth_debug;
1.42 markus 76:
1.1 markus 77: /*
1.12 markus 78: * Check if the user is allowed to log in via ssh. If user is listed
79: * in DenyUsers or one of user's groups is listed in DenyGroups, false
80: * will be returned. If AllowUsers isn't empty and user isn't listed
81: * there, or if AllowGroups isn't empty and one of user's groups isn't
82: * listed there, false will be returned.
1.1 markus 83: * If the user's shell is not executable, false will be returned.
1.4 markus 84: * Otherwise true is returned.
1.1 markus 85: */
1.5 markus 86: int
1.138 djm 87: allowed_user(struct ssh *ssh, struct passwd * pw)
1.1 markus 88: {
89: struct stat st;
1.35 markus 90: const char *hostname = NULL, *ipaddr = NULL;
1.117 djm 91: int r;
1.60 djm 92: u_int i;
1.1 markus 93:
94: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 95: if (!pw || !pw->pw_name)
1.1 markus 96: return 0;
97:
1.7 deraadt 98: /*
1.84 djm 99: * Deny if shell does not exist or is not executable unless we
100: * are chrooting.
1.7 deraadt 101: */
1.84 djm 102: if (options.chroot_directory == NULL ||
103: strcasecmp(options.chroot_directory, "none") == 0) {
104: char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
105: _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
106:
1.139 deraadt 107: if (stat(shell, &st) == -1) {
1.84 djm 108: logit("User %.100s not allowed because shell %.100s "
109: "does not exist", pw->pw_name, shell);
1.102 djm 110: free(shell);
1.84 djm 111: return 0;
112: }
113: if (S_ISREG(st.st_mode) == 0 ||
114: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
115: logit("User %.100s not allowed because shell %.100s "
116: "is not executable", pw->pw_name, shell);
1.102 djm 117: free(shell);
1.84 djm 118: return 0;
119: }
1.102 djm 120: free(shell);
1.34 stevesk 121: }
1.1 markus 122:
1.58 dtucker 123: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
124: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.114 djm 125: hostname = auth_get_canonical_hostname(ssh, options.use_dns);
126: ipaddr = ssh_remote_ipaddr(ssh);
1.35 markus 127: }
128:
1.1 markus 129: /* Return false if user is listed in DenyUsers */
130: if (options.num_deny_users > 0) {
1.119 dtucker 131: for (i = 0; i < options.num_deny_users; i++) {
1.117 djm 132: r = match_user(pw->pw_name, hostname, ipaddr,
133: options.deny_users[i]);
134: if (r < 0) {
135: fatal("Invalid DenyUsers pattern \"%.100s\"",
136: options.deny_users[i]);
1.118 djm 137: } else if (r != 0) {
1.57 dtucker 138: logit("User %.100s from %.100s not allowed "
139: "because listed in DenyUsers",
140: pw->pw_name, hostname);
1.1 markus 141: return 0;
1.34 stevesk 142: }
1.119 dtucker 143: }
1.1 markus 144: }
145: /* Return false if AllowUsers isn't empty and user isn't listed there */
146: if (options.num_allow_users > 0) {
1.117 djm 147: for (i = 0; i < options.num_allow_users; i++) {
148: r = match_user(pw->pw_name, hostname, ipaddr,
149: options.allow_users[i]);
150: if (r < 0) {
151: fatal("Invalid AllowUsers pattern \"%.100s\"",
152: options.allow_users[i]);
153: } else if (r == 1)
1.1 markus 154: break;
1.117 djm 155: }
1.1 markus 156: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 157: if (i >= options.num_allow_users) {
1.57 dtucker 158: logit("User %.100s from %.100s not allowed because "
159: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 160: return 0;
1.34 stevesk 161: }
1.1 markus 162: }
163: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 164: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 165: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 166: logit("User %.100s from %.100s not allowed because "
167: "not in any group", pw->pw_name, hostname);
1.1 markus 168: return 0;
1.34 stevesk 169: }
1.1 markus 170:
1.12 markus 171: /* Return false if one of user's groups is listed in DenyGroups */
172: if (options.num_deny_groups > 0)
173: if (ga_match(options.deny_groups,
174: options.num_deny_groups)) {
175: ga_free();
1.57 dtucker 176: logit("User %.100s from %.100s not allowed "
177: "because a group is listed in DenyGroups",
178: pw->pw_name, hostname);
1.1 markus 179: return 0;
1.12 markus 180: }
1.1 markus 181: /*
1.12 markus 182: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 183: * isn't listed there
184: */
1.12 markus 185: if (options.num_allow_groups > 0)
186: if (!ga_match(options.allow_groups,
187: options.num_allow_groups)) {
188: ga_free();
1.57 dtucker 189: logit("User %.100s from %.100s not allowed "
190: "because none of user's groups are listed "
191: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 192: return 0;
1.12 markus 193: }
194: ga_free();
1.1 markus 195: }
196: /* We found no reason not to let this user try to log on... */
197: return 1;
1.13 markus 198: }
199:
1.122 djm 200: /*
201: * Formats any key left in authctxt->auth_method_key for inclusion in
202: * auth_log()'s message. Also includes authxtct->auth_method_info if present.
203: */
204: static char *
205: format_method_key(Authctxt *authctxt)
1.103 djm 206: {
1.122 djm 207: const struct sshkey *key = authctxt->auth_method_key;
208: const char *methinfo = authctxt->auth_method_info;
1.133 djm 209: char *fp, *cafp, *ret = NULL;
1.122 djm 210:
211: if (key == NULL)
212: return NULL;
213:
1.131 markus 214: if (sshkey_is_cert(key)) {
1.133 djm 215: fp = sshkey_fingerprint(key,
1.122 djm 216: options.fingerprint_hash, SSH_FP_DEFAULT);
1.133 djm 217: cafp = sshkey_fingerprint(key->cert->signature_key,
218: options.fingerprint_hash, SSH_FP_DEFAULT);
219: xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
220: sshkey_type(key), fp == NULL ? "(null)" : fp,
221: key->cert->key_id,
1.122 djm 222: (unsigned long long)key->cert->serial,
223: sshkey_type(key->cert->signature_key),
1.133 djm 224: cafp == NULL ? "(null)" : cafp,
1.122 djm 225: methinfo == NULL ? "" : ", ",
226: methinfo == NULL ? "" : methinfo);
227: free(fp);
1.133 djm 228: free(cafp);
1.122 djm 229: } else {
230: fp = sshkey_fingerprint(key, options.fingerprint_hash,
231: SSH_FP_DEFAULT);
232: xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
233: fp == NULL ? "(null)" : fp,
234: methinfo == NULL ? "" : ", ",
235: methinfo == NULL ? "" : methinfo);
236: free(fp);
237: }
238: return ret;
1.103 djm 239: }
240:
241: void
1.138 djm 242: auth_log(struct ssh *ssh, int authenticated, int partial,
1.103 djm 243: const char *method, const char *submethod)
1.13 markus 244: {
1.138 djm 245: Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1.133 djm 246: int level = SYSLOG_LEVEL_VERBOSE;
1.122 djm 247: const char *authmsg;
248: char *extra = NULL;
1.67 dtucker 249:
250: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
251: return;
1.13 markus 252:
253: /* Raise logging level */
254: if (authenticated == 1 ||
255: !authctxt->valid ||
1.54 dtucker 256: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 257: strcmp(method, "password") == 0)
1.133 djm 258: level = SYSLOG_LEVEL_INFO;
1.13 markus 259:
260: if (authctxt->postponed)
261: authmsg = "Postponed";
1.98 djm 262: else if (partial)
263: authmsg = "Partial";
1.13 markus 264: else
265: authmsg = authenticated ? "Accepted" : "Failed";
266:
1.122 djm 267: if ((extra = format_method_key(authctxt)) == NULL) {
268: if (authctxt->auth_method_info != NULL)
269: extra = xstrdup(authctxt->auth_method_info);
270: }
271:
1.133 djm 272: do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
1.13 markus 273: authmsg,
274: method,
1.98 djm 275: submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
1.56 markus 276: authctxt->valid ? "" : "invalid user ",
1.29 markus 277: authctxt->user,
1.114 djm 278: ssh_remote_ipaddr(ssh),
279: ssh_remote_port(ssh),
1.122 djm 280: extra != NULL ? ": " : "",
281: extra != NULL ? extra : "");
282:
283: free(extra);
1.105 djm 284: }
285:
286: void
1.138 djm 287: auth_maxtries_exceeded(struct ssh *ssh)
1.105 djm 288: {
1.138 djm 289: Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1.114 djm 290:
1.110 djm 291: error("maximum authentication attempts exceeded for "
1.116 markus 292: "%s%.100s from %.200s port %d ssh2",
1.105 djm 293: authctxt->valid ? "" : "invalid user ",
294: authctxt->user,
1.114 djm 295: ssh_remote_ipaddr(ssh),
1.116 markus 296: ssh_remote_port(ssh));
1.138 djm 297: ssh_packet_disconnect(ssh, "Too many authentication failures");
1.105 djm 298: /* NOTREACHED */
1.13 markus 299: }
300:
301: /*
1.17 markus 302: * Check whether root logins are disallowed.
1.13 markus 303: */
304: int
1.126 djm 305: auth_root_allowed(struct ssh *ssh, const char *method)
1.13 markus 306: {
1.17 markus 307: switch (options.permit_root_login) {
308: case PERMIT_YES:
1.13 markus 309: return 1;
1.17 markus 310: case PERMIT_NO_PASSWD:
1.112 deraadt 311: if (strcmp(method, "publickey") == 0 ||
312: strcmp(method, "hostbased") == 0 ||
1.113 djm 313: strcmp(method, "gssapi-with-mic") == 0)
1.17 markus 314: return 1;
315: break;
316: case PERMIT_FORCED_ONLY:
1.126 djm 317: if (auth_opts->force_command != NULL) {
1.47 itojun 318: logit("Root login accepted for forced command.");
1.17 markus 319: return 1;
320: }
321: break;
1.13 markus 322: }
1.114 djm 323: logit("ROOT LOGIN REFUSED FROM %.200s port %d",
324: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.22 markus 325: return 0;
326: }
327:
328:
329: /*
330: * Given a template and a passwd structure, build a filename
331: * by substituting % tokenised options. Currently, %% becomes '%',
332: * %h becomes the home directory and %u the username.
333: *
334: * This returns a buffer allocated by xmalloc.
335: */
1.93 djm 336: char *
1.59 djm 337: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 338: {
1.129 djm 339: char *file, uidstr[32], ret[PATH_MAX];
1.65 djm 340: int i;
1.22 markus 341:
1.129 djm 342: snprintf(uidstr, sizeof(uidstr), "%llu",
343: (unsigned long long)pw->pw_uid);
1.59 djm 344: file = percent_expand(filename, "h", pw->pw_dir,
1.129 djm 345: "u", pw->pw_name, "U", uidstr, (char *)NULL);
1.22 markus 346:
347: /*
348: * Ensure that filename starts anchored. If not, be backward
349: * compatible and prepend the '%h/'
350: */
1.134 djm 351: if (path_absolute(file))
1.59 djm 352: return (file);
353:
1.65 djm 354: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
355: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 356: fatal("expand_authorized_keys: path too long");
1.102 djm 357: free(file);
1.65 djm 358: return (xstrdup(ret));
1.22 markus 359: }
1.24 markus 360:
1.87 djm 361: char *
362: authorized_principals_file(struct passwd *pw)
363: {
1.111 djm 364: if (options.authorized_principals_file == NULL)
1.87 djm 365: return NULL;
366: return expand_authorized_keys(options.authorized_principals_file, pw);
367: }
368:
1.24 markus 369: /* return ok if key exists in sysfile or userfile */
370: HostStatus
1.121 markus 371: check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
1.24 markus 372: const char *sysfile, const char *userfile)
373: {
374: char *user_hostfile;
375: struct stat st;
1.30 stevesk 376: HostStatus host_status;
1.91 djm 377: struct hostkeys *hostkeys;
378: const struct hostkey_entry *found;
1.24 markus 379:
1.91 djm 380: hostkeys = init_hostkeys();
381: load_hostkeys(hostkeys, host, sysfile);
382: if (userfile != NULL) {
1.24 markus 383: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
384: if (options.strict_modes &&
385: (stat(user_hostfile, &st) == 0) &&
386: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 387: (st.st_mode & 022) != 0)) {
1.47 itojun 388: logit("Authentication refused for %.100s: "
1.24 markus 389: "bad owner or modes for %.200s",
390: pw->pw_name, user_hostfile);
1.88 djm 391: auth_debug_add("Ignored %.200s: bad ownership or modes",
392: user_hostfile);
1.24 markus 393: } else {
394: temporarily_use_uid(pw);
1.91 djm 395: load_hostkeys(hostkeys, host, user_hostfile);
1.24 markus 396: restore_uid();
397: }
1.102 djm 398: free(user_hostfile);
1.24 markus 399: }
1.91 djm 400: host_status = check_key_in_hostkeys(hostkeys, key, &found);
401: if (host_status == HOST_REVOKED)
402: error("WARNING: revoked key for %s attempted authentication",
1.142 djm 403: host);
1.91 djm 404: else if (host_status == HOST_OK)
405: debug("%s: key for %s found at %s:%ld", __func__,
406: found->host, found->file, found->line);
407: else
408: debug("%s: key for host %s not found", __func__, host);
409:
410: free_hostkeys(hostkeys);
1.24 markus 411:
412: return host_status;
413: }
414:
1.87 djm 415: static FILE *
416: auth_openfile(const char *file, struct passwd *pw, int strict_modes,
417: int log_missing, char *file_type)
1.79 dtucker 418: {
419: char line[1024];
420: struct stat st;
421: int fd;
422: FILE *f;
423:
1.81 dtucker 424: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
1.87 djm 425: if (log_missing || errno != ENOENT)
426: debug("Could not open %s '%s': %s", file_type, file,
1.81 dtucker 427: strerror(errno));
1.79 dtucker 428: return NULL;
1.81 dtucker 429: }
1.79 dtucker 430:
1.139 deraadt 431: if (fstat(fd, &st) == -1) {
1.79 dtucker 432: close(fd);
433: return NULL;
434: }
435: if (!S_ISREG(st.st_mode)) {
1.87 djm 436: logit("User %s %s %s is not a regular file",
437: pw->pw_name, file_type, file);
1.79 dtucker 438: close(fd);
439: return NULL;
440: }
441: unset_nonblock(fd);
442: if ((f = fdopen(fd, "r")) == NULL) {
443: close(fd);
444: return NULL;
445: }
1.90 djm 446: if (strict_modes &&
1.123 djm 447: safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
1.79 dtucker 448: fclose(f);
449: logit("Authentication refused: %s", line);
1.88 djm 450: auth_debug_add("Ignored %s: %s", file_type, line);
1.79 dtucker 451: return NULL;
452: }
453:
454: return f;
1.87 djm 455: }
456:
457:
458: FILE *
459: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
460: {
461: return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
462: }
463:
464: FILE *
465: auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
466: {
467: return auth_openfile(file, pw, strict_modes, 0,
468: "authorized principals");
1.37 provos 469: }
470:
471: struct passwd *
1.138 djm 472: getpwnamallow(struct ssh *ssh, const char *user)
1.37 provos 473: {
1.38 provos 474: extern login_cap_t *lc;
475: auth_session_t *as;
1.37 provos 476: struct passwd *pw;
1.137 djm 477: struct connection_info *ci;
1.71 dtucker 478:
1.137 djm 479: ci = get_connection_info(ssh, 1, options.use_dns);
1.96 dtucker 480: ci->user = user;
1.146 djm 481: parse_server_match_config(&options, &includes, ci);
1.120 djm 482: log_change_level(options.log_level);
1.124 djm 483: process_permitopen(ssh, &options);
1.37 provos 484:
485: pw = getpwnam(user);
1.45 stevesk 486: if (pw == NULL) {
1.114 djm 487: logit("Invalid user %.100s from %.100s port %d",
488: user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.45 stevesk 489: return (NULL);
490: }
1.138 djm 491: if (!allowed_user(ssh, pw))
1.38 provos 492: return (NULL);
493: if ((lc = login_getclass(pw->pw_class)) == NULL) {
494: debug("unable to get login class: %s", user);
495: return (NULL);
496: }
497: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 498: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 499: debug("Approval failure for %s", user);
1.37 provos 500: pw = NULL;
1.38 provos 501: }
502: if (as != NULL)
503: auth_close(as);
1.41 markus 504: if (pw != NULL)
505: return (pwcopy(pw));
506: return (NULL);
1.85 djm 507: }
508:
509: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
510: int
1.121 markus 511: auth_key_is_revoked(struct sshkey *key)
1.85 djm 512: {
1.107 djm 513: char *fp = NULL;
514: int r;
1.85 djm 515:
516: if (options.revoked_keys_file == NULL)
517: return 0;
1.108 djm 518: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
519: SSH_FP_DEFAULT)) == NULL) {
1.107 djm 520: r = SSH_ERR_ALLOC_FAIL;
521: error("%s: fingerprint key: %s", __func__, ssh_err(r));
522: goto out;
523: }
524:
525: r = sshkey_check_revoked(key, options.revoked_keys_file);
526: switch (r) {
1.100 djm 527: case 0:
1.107 djm 528: break; /* not revoked */
529: case SSH_ERR_KEY_REVOKED:
530: error("Authentication key %s %s revoked by file %s",
531: sshkey_type(key), fp, options.revoked_keys_file);
532: goto out;
1.100 djm 533: default:
1.107 djm 534: error("Error checking authentication key %s %s in "
535: "revoked keys file %s: %s", sshkey_type(key), fp,
536: options.revoked_keys_file, ssh_err(r));
537: goto out;
1.100 djm 538: }
1.107 djm 539:
540: /* Success */
541: r = 0;
542:
543: out:
544: free(fp);
545: return r == 0 ? 0 : 1;
1.42 markus 546: }
547:
548: void
549: auth_debug_add(const char *fmt,...)
550: {
551: char buf[1024];
552: va_list args;
1.131 markus 553: int r;
1.42 markus 554:
1.131 markus 555: if (auth_debug == NULL)
1.42 markus 556: return;
557:
558: va_start(args, fmt);
559: vsnprintf(buf, sizeof(buf), fmt, args);
560: va_end(args);
1.131 markus 561: if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
562: fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r));
1.42 markus 563: }
564:
565: void
1.138 djm 566: auth_debug_send(struct ssh *ssh)
1.42 markus 567: {
568: char *msg;
1.131 markus 569: int r;
1.42 markus 570:
1.131 markus 571: if (auth_debug == NULL)
1.42 markus 572: return;
1.131 markus 573: while (sshbuf_len(auth_debug) != 0) {
574: if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
575: fatal("%s: sshbuf_get_cstring: %s",
576: __func__, ssh_err(r));
577: ssh_packet_send_debug(ssh, "%s", msg);
1.102 djm 578: free(msg);
1.42 markus 579: }
580: }
581:
582: void
583: auth_debug_reset(void)
584: {
1.131 markus 585: if (auth_debug != NULL)
586: sshbuf_reset(auth_debug);
587: else if ((auth_debug = sshbuf_new()) == NULL)
588: fatal("%s: sshbuf_new failed", __func__);
1.49 markus 589: }
590:
591: struct passwd *
592: fakepw(void)
593: {
594: static struct passwd fake;
595:
596: memset(&fake, 0, sizeof(fake));
597: fake.pw_name = "NOUSER";
598: fake.pw_passwd =
1.51 djm 599: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 600: fake.pw_gecos = "NOUSER";
1.53 deraadt 601: fake.pw_uid = (uid_t)-1;
602: fake.pw_gid = (gid_t)-1;
1.49 markus 603: fake.pw_class = "";
604: fake.pw_dir = "/nonexist";
605: fake.pw_shell = "/nonexist";
606:
607: return (&fake);
1.114 djm 608: }
609:
610: /*
611: * Returns the remote DNS hostname as a string. The returned string must not
612: * be freed. NB. this will usually trigger a DNS query the first time it is
613: * called.
614: * This function does additional checks on the hostname to mitigate some
615: * attacks on legacy rhosts-style authentication.
616: * XXX is RhostsRSAAuthentication vulnerable to these?
617: * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
618: */
619:
620: static char *
621: remote_hostname(struct ssh *ssh)
622: {
623: struct sockaddr_storage from;
624: socklen_t fromlen;
625: struct addrinfo hints, *ai, *aitop;
626: char name[NI_MAXHOST], ntop2[NI_MAXHOST];
627: const char *ntop = ssh_remote_ipaddr(ssh);
628:
629: /* Get IP address of client. */
630: fromlen = sizeof(from);
631: memset(&from, 0, sizeof(from));
632: if (getpeername(ssh_packet_get_connection_in(ssh),
1.139 deraadt 633: (struct sockaddr *)&from, &fromlen) == -1) {
1.114 djm 634: debug("getpeername failed: %.100s", strerror(errno));
1.144 tobhe 635: return xstrdup(ntop);
1.114 djm 636: }
637:
638: debug3("Trying to reverse map address %.100s.", ntop);
639: /* Map the IP address to a host name. */
640: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
641: NULL, 0, NI_NAMEREQD) != 0) {
642: /* Host name not found. Use ip address. */
1.144 tobhe 643: return xstrdup(ntop);
1.114 djm 644: }
645:
646: /*
647: * if reverse lookup result looks like a numeric hostname,
648: * someone is trying to trick us by PTR record like following:
649: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
650: */
651: memset(&hints, 0, sizeof(hints));
652: hints.ai_socktype = SOCK_DGRAM; /*dummy*/
653: hints.ai_flags = AI_NUMERICHOST;
654: if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
655: logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
656: name, ntop);
657: freeaddrinfo(ai);
1.144 tobhe 658: return xstrdup(ntop);
1.114 djm 659: }
660:
661: /* Names are stored in lowercase. */
662: lowercase(name);
663:
664: /*
665: * Map it back to an IP address and check that the given
666: * address actually is an address of this host. This is
667: * necessary because anyone with access to a name server can
668: * define arbitrary names for an IP address. Mapping from
669: * name to IP address can be trusted better (but can still be
670: * fooled if the intruder has access to the name server of
671: * the domain).
672: */
673: memset(&hints, 0, sizeof(hints));
674: hints.ai_family = from.ss_family;
675: hints.ai_socktype = SOCK_STREAM;
676: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
677: logit("reverse mapping checking getaddrinfo for %.700s "
1.115 dtucker 678: "[%s] failed.", name, ntop);
1.144 tobhe 679: return xstrdup(ntop);
1.114 djm 680: }
681: /* Look for the address from the list of addresses. */
682: for (ai = aitop; ai; ai = ai->ai_next) {
683: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
684: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
685: (strcmp(ntop, ntop2) == 0))
686: break;
687: }
688: freeaddrinfo(aitop);
689: /* If we reached the end of the list, the address was not there. */
690: if (ai == NULL) {
691: /* Address not found for the host name. */
692: logit("Address %.100s maps to %.600s, but this does not "
1.115 dtucker 693: "map back to the address.", ntop, name);
1.144 tobhe 694: return xstrdup(ntop);
1.114 djm 695: }
1.144 tobhe 696: return xstrdup(name);
1.114 djm 697: }
698:
699: /*
700: * Return the canonical name of the host in the other side of the current
701: * connection. The host name is cached, so it is efficient to call this
702: * several times.
703: */
704:
705: const char *
706: auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
707: {
708: static char *dnsname;
709:
710: if (!use_dns)
711: return ssh_remote_ipaddr(ssh);
712: else if (dnsname != NULL)
713: return dnsname;
714: else {
715: dnsname = remote_hostname(ssh);
716: return dnsname;
717: }
1.125 markus 718: }
719:
720: /*
1.132 martijn 721: * Runs command in a subprocess with a minimal environment.
1.125 markus 722: * Returns pid on success, 0 on failure.
723: * The child stdout and stderr maybe captured, left attached or sent to
724: * /dev/null depending on the contents of flags.
725: * "tag" is prepended to log messages.
726: * NB. "command" is only used for logging; the actual command executed is
727: * av[0].
728: */
729: pid_t
730: subprocess(const char *tag, struct passwd *pw, const char *command,
731: int ac, char **av, FILE **child, u_int flags)
732: {
733: FILE *f = NULL;
734: struct stat st;
735: int fd, devnull, p[2], i;
736: pid_t pid;
737: char *cp, errmsg[512];
738: u_int envsize;
739: char **child_env;
740:
741: if (child != NULL)
742: *child = NULL;
743:
744: debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
745: tag, command, pw->pw_name, flags);
746:
747: /* Check consistency */
748: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
749: (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
750: error("%s: inconsistent flags", __func__);
751: return 0;
752: }
753: if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
754: error("%s: inconsistent flags/output", __func__);
755: return 0;
756: }
757:
758: /*
759: * If executing an explicit binary, then verify the it exists
760: * and appears safe-ish to execute
761: */
1.134 djm 762: if (!path_absolute(av[0])) {
1.125 markus 763: error("%s path is not absolute", tag);
764: return 0;
765: }
766: temporarily_use_uid(pw);
1.139 deraadt 767: if (stat(av[0], &st) == -1) {
1.125 markus 768: error("Could not stat %s \"%s\": %s", tag,
769: av[0], strerror(errno));
770: restore_uid();
771: return 0;
772: }
773: if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
774: error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
775: restore_uid();
776: return 0;
777: }
778: /* Prepare to keep the child's stdout if requested */
1.139 deraadt 779: if (pipe(p) == -1) {
1.125 markus 780: error("%s: pipe: %s", tag, strerror(errno));
781: restore_uid();
782: return 0;
783: }
784: restore_uid();
785:
786: switch ((pid = fork())) {
787: case -1: /* error */
788: error("%s: fork: %s", tag, strerror(errno));
789: close(p[0]);
790: close(p[1]);
791: return 0;
792: case 0: /* child */
793: /* Prepare a minimal environment for the child. */
794: envsize = 5;
795: child_env = xcalloc(sizeof(*child_env), envsize);
796: child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
797: child_set_env(&child_env, &envsize, "USER", pw->pw_name);
798: child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
799: child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
800: if ((cp = getenv("LANG")) != NULL)
801: child_set_env(&child_env, &envsize, "LANG", cp);
802:
803: for (i = 0; i < NSIG; i++)
1.145 dtucker 804: ssh_signal(i, SIG_DFL);
1.125 markus 805:
806: if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
807: error("%s: open %s: %s", tag, _PATH_DEVNULL,
808: strerror(errno));
809: _exit(1);
810: }
811: if (dup2(devnull, STDIN_FILENO) == -1) {
812: error("%s: dup2: %s", tag, strerror(errno));
813: _exit(1);
814: }
815:
816: /* Set up stdout as requested; leave stderr in place for now. */
817: fd = -1;
818: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
819: fd = p[1];
820: else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
821: fd = devnull;
822: if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
823: error("%s: dup2: %s", tag, strerror(errno));
824: _exit(1);
825: }
826: closefrom(STDERR_FILENO + 1);
827:
828: /* Don't use permanently_set_uid() here to avoid fatal() */
1.139 deraadt 829: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) {
1.125 markus 830: error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
831: strerror(errno));
832: _exit(1);
833: }
1.139 deraadt 834: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) {
1.125 markus 835: error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
836: strerror(errno));
837: _exit(1);
838: }
839: /* stdin is pointed to /dev/null at this point */
840: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
841: dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
842: error("%s: dup2: %s", tag, strerror(errno));
843: _exit(1);
844: }
845:
846: execve(av[0], av, child_env);
847: error("%s exec \"%s\": %s", tag, command, strerror(errno));
848: _exit(127);
849: default: /* parent */
850: break;
851: }
852:
853: close(p[1]);
854: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
855: close(p[0]);
856: else if ((f = fdopen(p[0], "r")) == NULL) {
857: error("%s: fdopen: %s", tag, strerror(errno));
858: close(p[0]);
859: /* Don't leave zombie child */
860: kill(pid, SIGTERM);
861: while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
862: ;
863: return 0;
864: }
865: /* Success */
866: debug3("%s: %s pid %ld", __func__, tag, (long)pid);
867: if (child != NULL)
868: *child = f;
869: return pid;
1.126 djm 870: }
871:
872: /* These functions link key/cert options to the auth framework */
873:
874: /* Log sshauthopt options locally and (optionally) for remote transmission */
875: void
876: auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
877: {
878: int do_env = options.permit_user_env && opts->nenv > 0;
879: int do_permitopen = opts->npermitopen > 0 &&
880: (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
1.130 djm 881: int do_permitlisten = opts->npermitlisten > 0 &&
882: (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
1.126 djm 883: size_t i;
1.127 djm 884: char msg[1024], buf[64];
1.126 djm 885:
1.127 djm 886: snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
1.126 djm 887: /* Try to keep this alphabetically sorted */
1.147 ! djm 888: snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
1.126 djm 889: opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
890: opts->force_command == NULL ? "" : " command",
891: do_env ? " environment" : "",
1.127 djm 892: opts->valid_before == 0 ? "" : "expires",
1.147 ! djm 893: opts->no_require_user_presence ? " no-touch-required" : "",
1.126 djm 894: do_permitopen ? " permitopen" : "",
1.130 djm 895: do_permitlisten ? " permitlisten" : "",
1.126 djm 896: opts->permit_port_forwarding_flag ? " port-forwarding" : "",
897: opts->cert_principals == NULL ? "" : " principals",
898: opts->permit_pty_flag ? " pty" : "",
1.147 ! djm 899: opts->require_verify ? " uv" : "",
1.126 djm 900: opts->force_tun_device == -1 ? "" : " tun=",
1.127 djm 901: opts->force_tun_device == -1 ? "" : buf,
1.126 djm 902: opts->permit_user_rc ? " user-rc" : "",
1.147 ! djm 903: opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
1.126 djm 904:
905: debug("%s: %s", loc, msg);
906: if (do_remote)
907: auth_debug_add("%s: %s", loc, msg);
908:
909: if (options.permit_user_env) {
910: for (i = 0; i < opts->nenv; i++) {
911: debug("%s: environment: %s", loc, opts->env[i]);
912: if (do_remote) {
913: auth_debug_add("%s: environment: %s",
914: loc, opts->env[i]);
915: }
916: }
917: }
918:
919: /* Go into a little more details for the local logs. */
1.127 djm 920: if (opts->valid_before != 0) {
921: format_absolute_time(opts->valid_before, buf, sizeof(buf));
922: debug("%s: expires at %s", loc, buf);
923: }
1.126 djm 924: if (opts->cert_principals != NULL) {
925: debug("%s: authorized principals: \"%s\"",
926: loc, opts->cert_principals);
927: }
928: if (opts->force_command != NULL)
929: debug("%s: forced command: \"%s\"", loc, opts->force_command);
1.130 djm 930: if (do_permitopen) {
1.126 djm 931: for (i = 0; i < opts->npermitopen; i++) {
932: debug("%s: permitted open: %s",
933: loc, opts->permitopen[i]);
1.130 djm 934: }
935: }
936: if (do_permitlisten) {
937: for (i = 0; i < opts->npermitlisten; i++) {
938: debug("%s: permitted listen: %s",
939: loc, opts->permitlisten[i]);
1.126 djm 940: }
941: }
942: }
943:
944: /* Activate a new set of key/cert options; merging with what is there. */
945: int
946: auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
947: {
948: struct sshauthopt *old = auth_opts;
949: const char *emsg = NULL;
950:
951: debug("%s: setting new authentication options", __func__);
952: if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
953: error("Inconsistent authentication options: %s", emsg);
954: return -1;
955: }
956: return 0;
957: }
958:
959: /* Disable forwarding, etc for the session */
960: void
961: auth_restrict_session(struct ssh *ssh)
962: {
963: struct sshauthopt *restricted;
964:
965: debug("%s: restricting session", __func__);
966:
967: /* A blank sshauthopt defaults to permitting nothing */
968: restricted = sshauthopt_new();
1.128 djm 969: restricted->permit_pty_flag = 1;
1.126 djm 970: restricted->restricted = 1;
971:
972: if (auth_activate_options(ssh, restricted) != 0)
973: fatal("%s: failed to restrict session", __func__);
974: sshauthopt_free(restricted);
975: }
976:
977: int
978: auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
979: struct sshauthopt *opts, int allow_cert_authority, const char *loc)
980: {
981: const char *remote_ip = ssh_remote_ipaddr(ssh);
982: const char *remote_host = auth_get_canonical_hostname(ssh,
983: options.use_dns);
1.127 djm 984: time_t now = time(NULL);
985: char buf[64];
1.126 djm 986:
1.127 djm 987: /*
988: * Check keys/principals file expiry time.
989: * NB. validity interval in certificate is handled elsewhere.
990: */
991: if (opts->valid_before && now > 0 &&
992: opts->valid_before < (uint64_t)now) {
993: format_absolute_time(opts->valid_before, buf, sizeof(buf));
994: debug("%s: entry expired at %s", loc, buf);
995: auth_debug_add("%s: entry expired at %s", loc, buf);
996: return -1;
997: }
1.126 djm 998: /* Consistency checks */
999: if (opts->cert_principals != NULL && !opts->cert_authority) {
1000: debug("%s: principals on non-CA key", loc);
1001: auth_debug_add("%s: principals on non-CA key", loc);
1002: /* deny access */
1003: return -1;
1004: }
1005: /* cert-authority flag isn't valid in authorized_principals files */
1006: if (!allow_cert_authority && opts->cert_authority) {
1007: debug("%s: cert-authority flag invalid here", loc);
1008: auth_debug_add("%s: cert-authority flag invalid here", loc);
1009: /* deny access */
1010: return -1;
1011: }
1012:
1013: /* Perform from= checks */
1014: if (opts->required_from_host_keys != NULL) {
1015: switch (match_host_and_ip(remote_host, remote_ip,
1016: opts->required_from_host_keys )) {
1017: case 1:
1018: /* Host name matches. */
1019: break;
1020: case -1:
1021: default:
1022: debug("%s: invalid from criteria", loc);
1023: auth_debug_add("%s: invalid from criteria", loc);
1024: /* FALLTHROUGH */
1025: case 0:
1026: logit("%s: Authentication tried for %.100s with "
1027: "correct key but not from a permitted "
1028: "host (host=%.200s, ip=%.200s, required=%.200s).",
1029: loc, pw->pw_name, remote_host, remote_ip,
1030: opts->required_from_host_keys);
1031: auth_debug_add("%s: Your host '%.200s' is not "
1032: "permitted to use this key for login.",
1033: loc, remote_host);
1034: /* deny access */
1035: return -1;
1036: }
1037: }
1038: /* Check source-address restriction from certificate */
1039: if (opts->required_from_host_cert != NULL) {
1040: switch (addr_match_cidr_list(remote_ip,
1041: opts->required_from_host_cert)) {
1042: case 1:
1043: /* accepted */
1044: break;
1045: case -1:
1046: default:
1047: /* invalid */
1048: error("%s: Certificate source-address invalid",
1049: loc);
1050: /* FALLTHROUGH */
1051: case 0:
1052: logit("%s: Authentication tried for %.100s with valid "
1053: "certificate but not from a permitted source "
1054: "address (%.200s).", loc, pw->pw_name, remote_ip);
1055: auth_debug_add("%s: Your address '%.200s' is not "
1056: "permitted to use this certificate for login.",
1057: loc, remote_ip);
1058: return -1;
1059: }
1060: }
1061: /*
1062: *
1063: * XXX this is spammy. We should report remotely only for keys
1064: * that are successful in actual auth attempts, and not PK_OK
1065: * tests.
1066: */
1067: auth_log_authopts(loc, opts, 1);
1068:
1069: return 0;
1.1 markus 1070: }
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