Annotation of src/usr.bin/ssh/auth.c, Revision 1.158
1.158 ! djm 1: /* $OpenBSD: auth.c,v 1.157 2022/05/27 05:02:46 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();
1.150 djm 381: load_hostkeys(hostkeys, host, sysfile, 0);
1.91 djm 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);
1.150 djm 395: load_hostkeys(hostkeys, host, user_hostfile, 0);
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)
1.149 djm 405: debug_f("key for %s found at %s:%ld",
1.91 djm 406: found->host, found->file, found->line);
407: else
1.149 djm 408: debug_f("key for host %s not found", host);
1.91 djm 409:
410: free_hostkeys(hostkeys);
1.24 markus 411:
412: return host_status;
1.37 provos 413: }
414:
415: struct passwd *
1.138 djm 416: getpwnamallow(struct ssh *ssh, const char *user)
1.37 provos 417: {
1.38 provos 418: extern login_cap_t *lc;
419: auth_session_t *as;
1.37 provos 420: struct passwd *pw;
1.137 djm 421: struct connection_info *ci;
1.148 djm 422: u_int i;
1.71 dtucker 423:
1.137 djm 424: ci = get_connection_info(ssh, 1, options.use_dns);
1.96 dtucker 425: ci->user = user;
1.146 djm 426: parse_server_match_config(&options, &includes, ci);
1.120 djm 427: log_change_level(options.log_level);
1.148 djm 428: log_verbose_reset();
429: for (i = 0; i < options.num_log_verbose; i++)
430: log_verbose_add(options.log_verbose[i]);
1.124 djm 431: process_permitopen(ssh, &options);
1.37 provos 432:
433: pw = getpwnam(user);
1.45 stevesk 434: if (pw == NULL) {
1.114 djm 435: logit("Invalid user %.100s from %.100s port %d",
436: user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.45 stevesk 437: return (NULL);
438: }
1.138 djm 439: if (!allowed_user(ssh, pw))
1.38 provos 440: return (NULL);
441: if ((lc = login_getclass(pw->pw_class)) == NULL) {
442: debug("unable to get login class: %s", user);
443: return (NULL);
444: }
445: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 446: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 447: debug("Approval failure for %s", user);
1.37 provos 448: pw = NULL;
1.38 provos 449: }
450: if (as != NULL)
451: auth_close(as);
1.41 markus 452: if (pw != NULL)
453: return (pwcopy(pw));
454: return (NULL);
1.85 djm 455: }
456:
457: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
458: int
1.121 markus 459: auth_key_is_revoked(struct sshkey *key)
1.85 djm 460: {
1.107 djm 461: char *fp = NULL;
462: int r;
1.85 djm 463:
464: if (options.revoked_keys_file == NULL)
465: return 0;
1.108 djm 466: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
467: SSH_FP_DEFAULT)) == NULL) {
1.107 djm 468: r = SSH_ERR_ALLOC_FAIL;
1.149 djm 469: error_fr(r, "fingerprint key");
1.107 djm 470: goto out;
471: }
472:
473: r = sshkey_check_revoked(key, options.revoked_keys_file);
474: switch (r) {
1.100 djm 475: case 0:
1.107 djm 476: break; /* not revoked */
477: case SSH_ERR_KEY_REVOKED:
478: error("Authentication key %s %s revoked by file %s",
479: sshkey_type(key), fp, options.revoked_keys_file);
480: goto out;
1.100 djm 481: default:
1.149 djm 482: error_r(r, "Error checking authentication key %s %s in "
483: "revoked keys file %s", sshkey_type(key), fp,
484: options.revoked_keys_file);
1.107 djm 485: goto out;
1.100 djm 486: }
1.107 djm 487:
488: /* Success */
489: r = 0;
490:
491: out:
492: free(fp);
493: return r == 0 ? 0 : 1;
1.42 markus 494: }
495:
496: void
497: auth_debug_add(const char *fmt,...)
498: {
499: char buf[1024];
500: va_list args;
1.131 markus 501: int r;
1.42 markus 502:
1.131 markus 503: if (auth_debug == NULL)
1.42 markus 504: return;
505:
506: va_start(args, fmt);
507: vsnprintf(buf, sizeof(buf), fmt, args);
508: va_end(args);
1.131 markus 509: if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
1.149 djm 510: fatal_fr(r, "sshbuf_put_cstring");
1.42 markus 511: }
512:
513: void
1.138 djm 514: auth_debug_send(struct ssh *ssh)
1.42 markus 515: {
516: char *msg;
1.131 markus 517: int r;
1.42 markus 518:
1.131 markus 519: if (auth_debug == NULL)
1.42 markus 520: return;
1.131 markus 521: while (sshbuf_len(auth_debug) != 0) {
522: if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
1.149 djm 523: fatal_fr(r, "sshbuf_get_cstring");
1.131 markus 524: ssh_packet_send_debug(ssh, "%s", msg);
1.102 djm 525: free(msg);
1.42 markus 526: }
527: }
528:
529: void
530: auth_debug_reset(void)
531: {
1.131 markus 532: if (auth_debug != NULL)
533: sshbuf_reset(auth_debug);
534: else if ((auth_debug = sshbuf_new()) == NULL)
1.149 djm 535: fatal_f("sshbuf_new failed");
1.49 markus 536: }
537:
538: struct passwd *
539: fakepw(void)
540: {
1.154 djm 541: static int done = 0;
1.49 markus 542: static struct passwd fake;
1.154 djm 543: const char hashchars[] = "./ABCDEFGHIJKLMNOPQRSTUVWXYZ"
544: "abcdefghijklmnopqrstuvwxyz0123456789"; /* from bcrypt.c */
545: char *cp;
546:
547: if (done)
548: return (&fake);
1.49 markus 549:
550: memset(&fake, 0, sizeof(fake));
551: fake.pw_name = "NOUSER";
1.154 djm 552: fake.pw_passwd = xstrdup("$2a$10$"
553: "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
554: for (cp = fake.pw_passwd + 7; *cp != '\0'; cp++)
555: *cp = hashchars[arc4random_uniform(sizeof(hashchars) - 1)];
1.49 markus 556: fake.pw_gecos = "NOUSER";
1.53 deraadt 557: fake.pw_uid = (uid_t)-1;
558: fake.pw_gid = (gid_t)-1;
1.49 markus 559: fake.pw_class = "";
560: fake.pw_dir = "/nonexist";
561: fake.pw_shell = "/nonexist";
1.154 djm 562: done = 1;
1.49 markus 563:
564: return (&fake);
1.114 djm 565: }
566:
567: /*
568: * Returns the remote DNS hostname as a string. The returned string must not
569: * be freed. NB. this will usually trigger a DNS query the first time it is
570: * called.
571: * This function does additional checks on the hostname to mitigate some
1.153 dtucker 572: * attacks on based on conflation of hostnames and IP addresses.
1.114 djm 573: */
574:
575: static char *
576: remote_hostname(struct ssh *ssh)
577: {
578: struct sockaddr_storage from;
579: socklen_t fromlen;
580: struct addrinfo hints, *ai, *aitop;
581: char name[NI_MAXHOST], ntop2[NI_MAXHOST];
582: const char *ntop = ssh_remote_ipaddr(ssh);
583:
584: /* Get IP address of client. */
585: fromlen = sizeof(from);
586: memset(&from, 0, sizeof(from));
587: if (getpeername(ssh_packet_get_connection_in(ssh),
1.139 deraadt 588: (struct sockaddr *)&from, &fromlen) == -1) {
1.114 djm 589: debug("getpeername failed: %.100s", strerror(errno));
1.144 tobhe 590: return xstrdup(ntop);
1.114 djm 591: }
592:
593: debug3("Trying to reverse map address %.100s.", ntop);
594: /* Map the IP address to a host name. */
595: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
596: NULL, 0, NI_NAMEREQD) != 0) {
597: /* Host name not found. Use ip address. */
1.144 tobhe 598: return xstrdup(ntop);
1.114 djm 599: }
600:
601: /*
602: * if reverse lookup result looks like a numeric hostname,
603: * someone is trying to trick us by PTR record like following:
604: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
605: */
606: memset(&hints, 0, sizeof(hints));
607: hints.ai_socktype = SOCK_DGRAM; /*dummy*/
608: hints.ai_flags = AI_NUMERICHOST;
609: if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
610: logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
611: name, ntop);
612: freeaddrinfo(ai);
1.144 tobhe 613: return xstrdup(ntop);
1.114 djm 614: }
615:
616: /* Names are stored in lowercase. */
617: lowercase(name);
618:
619: /*
620: * Map it back to an IP address and check that the given
621: * address actually is an address of this host. This is
622: * necessary because anyone with access to a name server can
623: * define arbitrary names for an IP address. Mapping from
624: * name to IP address can be trusted better (but can still be
625: * fooled if the intruder has access to the name server of
626: * the domain).
627: */
628: memset(&hints, 0, sizeof(hints));
629: hints.ai_family = from.ss_family;
630: hints.ai_socktype = SOCK_STREAM;
631: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
632: logit("reverse mapping checking getaddrinfo for %.700s "
1.115 dtucker 633: "[%s] failed.", name, ntop);
1.144 tobhe 634: return xstrdup(ntop);
1.114 djm 635: }
636: /* Look for the address from the list of addresses. */
637: for (ai = aitop; ai; ai = ai->ai_next) {
638: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
639: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
640: (strcmp(ntop, ntop2) == 0))
641: break;
642: }
643: freeaddrinfo(aitop);
644: /* If we reached the end of the list, the address was not there. */
645: if (ai == NULL) {
646: /* Address not found for the host name. */
647: logit("Address %.100s maps to %.600s, but this does not "
1.115 dtucker 648: "map back to the address.", ntop, name);
1.144 tobhe 649: return xstrdup(ntop);
1.114 djm 650: }
1.144 tobhe 651: return xstrdup(name);
1.114 djm 652: }
653:
654: /*
655: * Return the canonical name of the host in the other side of the current
656: * connection. The host name is cached, so it is efficient to call this
657: * several times.
658: */
659:
660: const char *
661: auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
662: {
663: static char *dnsname;
664:
665: if (!use_dns)
666: return ssh_remote_ipaddr(ssh);
667: else if (dnsname != NULL)
668: return dnsname;
669: else {
670: dnsname = remote_hostname(ssh);
671: return dnsname;
672: }
1.126 djm 673: }
674:
675: /* These functions link key/cert options to the auth framework */
676:
677: /* Log sshauthopt options locally and (optionally) for remote transmission */
678: void
679: auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
680: {
681: int do_env = options.permit_user_env && opts->nenv > 0;
682: int do_permitopen = opts->npermitopen > 0 &&
683: (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
1.130 djm 684: int do_permitlisten = opts->npermitlisten > 0 &&
685: (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
1.126 djm 686: size_t i;
1.127 djm 687: char msg[1024], buf[64];
1.126 djm 688:
1.127 djm 689: snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
1.126 djm 690: /* Try to keep this alphabetically sorted */
1.147 djm 691: snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
1.126 djm 692: opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
693: opts->force_command == NULL ? "" : " command",
694: do_env ? " environment" : "",
1.127 djm 695: opts->valid_before == 0 ? "" : "expires",
1.147 djm 696: opts->no_require_user_presence ? " no-touch-required" : "",
1.126 djm 697: do_permitopen ? " permitopen" : "",
1.130 djm 698: do_permitlisten ? " permitlisten" : "",
1.126 djm 699: opts->permit_port_forwarding_flag ? " port-forwarding" : "",
700: opts->cert_principals == NULL ? "" : " principals",
701: opts->permit_pty_flag ? " pty" : "",
1.147 djm 702: opts->require_verify ? " uv" : "",
1.126 djm 703: opts->force_tun_device == -1 ? "" : " tun=",
1.127 djm 704: opts->force_tun_device == -1 ? "" : buf,
1.126 djm 705: opts->permit_user_rc ? " user-rc" : "",
1.147 djm 706: opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
1.126 djm 707:
708: debug("%s: %s", loc, msg);
709: if (do_remote)
710: auth_debug_add("%s: %s", loc, msg);
711:
712: if (options.permit_user_env) {
713: for (i = 0; i < opts->nenv; i++) {
714: debug("%s: environment: %s", loc, opts->env[i]);
715: if (do_remote) {
716: auth_debug_add("%s: environment: %s",
717: loc, opts->env[i]);
718: }
719: }
720: }
721:
722: /* Go into a little more details for the local logs. */
1.127 djm 723: if (opts->valid_before != 0) {
724: format_absolute_time(opts->valid_before, buf, sizeof(buf));
725: debug("%s: expires at %s", loc, buf);
726: }
1.126 djm 727: if (opts->cert_principals != NULL) {
728: debug("%s: authorized principals: \"%s\"",
729: loc, opts->cert_principals);
730: }
731: if (opts->force_command != NULL)
732: debug("%s: forced command: \"%s\"", loc, opts->force_command);
1.130 djm 733: if (do_permitopen) {
1.126 djm 734: for (i = 0; i < opts->npermitopen; i++) {
735: debug("%s: permitted open: %s",
736: loc, opts->permitopen[i]);
1.130 djm 737: }
738: }
739: if (do_permitlisten) {
740: for (i = 0; i < opts->npermitlisten; i++) {
741: debug("%s: permitted listen: %s",
742: loc, opts->permitlisten[i]);
1.126 djm 743: }
744: }
745: }
746:
747: /* Activate a new set of key/cert options; merging with what is there. */
748: int
749: auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
750: {
751: struct sshauthopt *old = auth_opts;
752: const char *emsg = NULL;
753:
1.149 djm 754: debug_f("setting new authentication options");
1.126 djm 755: if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
756: error("Inconsistent authentication options: %s", emsg);
757: return -1;
758: }
759: return 0;
760: }
761:
762: /* Disable forwarding, etc for the session */
763: void
764: auth_restrict_session(struct ssh *ssh)
765: {
766: struct sshauthopt *restricted;
767:
1.149 djm 768: debug_f("restricting session");
1.126 djm 769:
770: /* A blank sshauthopt defaults to permitting nothing */
1.155 dtucker 771: if ((restricted = sshauthopt_new()) == NULL)
772: fatal_f("sshauthopt_new failed");
1.128 djm 773: restricted->permit_pty_flag = 1;
1.126 djm 774: restricted->restricted = 1;
775:
776: if (auth_activate_options(ssh, restricted) != 0)
1.149 djm 777: fatal_f("failed to restrict session");
1.126 djm 778: sshauthopt_free(restricted);
1.1 markus 779: }
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