Annotation of src/usr.bin/ssh/auth.c, Revision 1.125
1.125 ! markus 1: /* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 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:
1.70 stevesk 31: #include <errno.h>
1.79 dtucker 32: #include <fcntl.h>
1.77 djm 33: #include <login_cap.h>
1.61 stevesk 34: #include <paths.h>
1.68 stevesk 35: #include <pwd.h>
1.69 stevesk 36: #include <stdarg.h>
1.74 stevesk 37: #include <stdio.h>
1.72 stevesk 38: #include <string.h>
1.80 djm 39: #include <unistd.h>
1.109 deraadt 40: #include <limits.h>
1.114 djm 41: #include <netdb.h>
1.1 markus 42:
43: #include "xmalloc.h"
1.13 markus 44: #include "match.h"
1.14 markus 45: #include "groupaccess.h"
46: #include "log.h"
1.75 deraadt 47: #include "buffer.h"
1.106 millert 48: #include "misc.h"
1.1 markus 49: #include "servconf.h"
1.75 deraadt 50: #include "key.h"
51: #include "hostfile.h"
1.2 markus 52: #include "auth.h"
1.13 markus 53: #include "auth-options.h"
1.14 markus 54: #include "canohost.h"
1.24 markus 55: #include "uidswap.h"
1.42 markus 56: #include "packet.h"
1.75 deraadt 57: #ifdef GSSAPI
58: #include "ssh-gss.h"
59: #endif
1.85 djm 60: #include "authfile.h"
1.67 dtucker 61: #include "monitor_wrap.h"
1.107 djm 62: #include "authfile.h"
63: #include "ssherr.h"
1.103 djm 64: #include "compat.h"
1.2 markus 65:
1.1 markus 66: /* import */
67: extern ServerOptions options;
1.67 dtucker 68: extern int use_privsep;
1.1 markus 69:
1.42 markus 70: /* Debugging messages */
71: Buffer auth_debug;
72: int auth_debug_init;
73:
1.1 markus 74: /*
1.12 markus 75: * Check if the user is allowed to log in via ssh. If user is listed
76: * in DenyUsers or one of user's groups is listed in DenyGroups, false
77: * will be returned. If AllowUsers isn't empty and user isn't listed
78: * there, or if AllowGroups isn't empty and one of user's groups isn't
79: * listed there, false will be returned.
1.1 markus 80: * If the user's shell is not executable, false will be returned.
1.4 markus 81: * Otherwise true is returned.
1.1 markus 82: */
1.5 markus 83: int
1.1 markus 84: allowed_user(struct passwd * pw)
85: {
1.114 djm 86: struct ssh *ssh = active_state; /* XXX */
1.1 markus 87: struct stat st;
1.35 markus 88: const char *hostname = NULL, *ipaddr = NULL;
1.117 djm 89: int r;
1.60 djm 90: u_int i;
1.1 markus 91:
92: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 93: if (!pw || !pw->pw_name)
1.1 markus 94: return 0;
95:
1.7 deraadt 96: /*
1.84 djm 97: * Deny if shell does not exist or is not executable unless we
98: * are chrooting.
1.7 deraadt 99: */
1.84 djm 100: if (options.chroot_directory == NULL ||
101: strcasecmp(options.chroot_directory, "none") == 0) {
102: char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
103: _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
104:
105: if (stat(shell, &st) != 0) {
106: logit("User %.100s not allowed because shell %.100s "
107: "does not exist", pw->pw_name, shell);
1.102 djm 108: free(shell);
1.84 djm 109: return 0;
110: }
111: if (S_ISREG(st.st_mode) == 0 ||
112: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
113: logit("User %.100s not allowed because shell %.100s "
114: "is not executable", pw->pw_name, shell);
1.102 djm 115: free(shell);
1.84 djm 116: return 0;
117: }
1.102 djm 118: free(shell);
1.34 stevesk 119: }
1.1 markus 120:
1.58 dtucker 121: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
122: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.114 djm 123: hostname = auth_get_canonical_hostname(ssh, options.use_dns);
124: ipaddr = ssh_remote_ipaddr(ssh);
1.35 markus 125: }
126:
1.1 markus 127: /* Return false if user is listed in DenyUsers */
128: if (options.num_deny_users > 0) {
1.119 dtucker 129: for (i = 0; i < options.num_deny_users; i++) {
1.117 djm 130: r = match_user(pw->pw_name, hostname, ipaddr,
131: options.deny_users[i]);
132: if (r < 0) {
133: fatal("Invalid DenyUsers pattern \"%.100s\"",
134: options.deny_users[i]);
1.118 djm 135: } else if (r != 0) {
1.57 dtucker 136: logit("User %.100s from %.100s not allowed "
137: "because listed in DenyUsers",
138: pw->pw_name, hostname);
1.1 markus 139: return 0;
1.34 stevesk 140: }
1.119 dtucker 141: }
1.1 markus 142: }
143: /* Return false if AllowUsers isn't empty and user isn't listed there */
144: if (options.num_allow_users > 0) {
1.117 djm 145: for (i = 0; i < options.num_allow_users; i++) {
146: r = match_user(pw->pw_name, hostname, ipaddr,
147: options.allow_users[i]);
148: if (r < 0) {
149: fatal("Invalid AllowUsers pattern \"%.100s\"",
150: options.allow_users[i]);
151: } else if (r == 1)
1.1 markus 152: break;
1.117 djm 153: }
1.1 markus 154: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 155: if (i >= options.num_allow_users) {
1.57 dtucker 156: logit("User %.100s from %.100s not allowed because "
157: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 158: return 0;
1.34 stevesk 159: }
1.1 markus 160: }
161: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 162: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 163: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 164: logit("User %.100s from %.100s not allowed because "
165: "not in any group", pw->pw_name, hostname);
1.1 markus 166: return 0;
1.34 stevesk 167: }
1.1 markus 168:
1.12 markus 169: /* Return false if one of user's groups is listed in DenyGroups */
170: if (options.num_deny_groups > 0)
171: if (ga_match(options.deny_groups,
172: options.num_deny_groups)) {
173: ga_free();
1.57 dtucker 174: logit("User %.100s from %.100s not allowed "
175: "because a group is listed in DenyGroups",
176: pw->pw_name, hostname);
1.1 markus 177: return 0;
1.12 markus 178: }
1.1 markus 179: /*
1.12 markus 180: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 181: * isn't listed there
182: */
1.12 markus 183: if (options.num_allow_groups > 0)
184: if (!ga_match(options.allow_groups,
185: options.num_allow_groups)) {
186: ga_free();
1.57 dtucker 187: logit("User %.100s from %.100s not allowed "
188: "because none of user's groups are listed "
189: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 190: return 0;
1.12 markus 191: }
192: ga_free();
1.1 markus 193: }
194: /* We found no reason not to let this user try to log on... */
195: return 1;
1.13 markus 196: }
197:
1.122 djm 198: /*
199: * Formats any key left in authctxt->auth_method_key for inclusion in
200: * auth_log()'s message. Also includes authxtct->auth_method_info if present.
201: */
202: static char *
203: format_method_key(Authctxt *authctxt)
1.103 djm 204: {
1.122 djm 205: const struct sshkey *key = authctxt->auth_method_key;
206: const char *methinfo = authctxt->auth_method_info;
207: char *fp, *ret = NULL;
208:
209: if (key == NULL)
210: return NULL;
211:
212: if (key_is_cert(key)) {
213: fp = sshkey_fingerprint(key->cert->signature_key,
214: options.fingerprint_hash, SSH_FP_DEFAULT);
215: xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s",
216: sshkey_type(key), key->cert->key_id,
217: (unsigned long long)key->cert->serial,
218: sshkey_type(key->cert->signature_key),
219: fp == NULL ? "(null)" : fp,
220: methinfo == NULL ? "" : ", ",
221: methinfo == NULL ? "" : methinfo);
222: free(fp);
223: } else {
224: fp = sshkey_fingerprint(key, options.fingerprint_hash,
225: SSH_FP_DEFAULT);
226: xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
227: fp == NULL ? "(null)" : fp,
228: methinfo == NULL ? "" : ", ",
229: methinfo == NULL ? "" : methinfo);
230: free(fp);
231: }
232: return ret;
1.103 djm 233: }
234:
235: void
1.98 djm 236: auth_log(Authctxt *authctxt, int authenticated, int partial,
1.103 djm 237: const char *method, const char *submethod)
1.13 markus 238: {
1.114 djm 239: struct ssh *ssh = active_state; /* XXX */
1.13 markus 240: void (*authlog) (const char *fmt,...) = verbose;
1.122 djm 241: const char *authmsg;
242: char *extra = NULL;
1.67 dtucker 243:
244: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
245: return;
1.13 markus 246:
247: /* Raise logging level */
248: if (authenticated == 1 ||
249: !authctxt->valid ||
1.54 dtucker 250: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 251: strcmp(method, "password") == 0)
1.47 itojun 252: authlog = logit;
1.13 markus 253:
254: if (authctxt->postponed)
255: authmsg = "Postponed";
1.98 djm 256: else if (partial)
257: authmsg = "Partial";
1.13 markus 258: else
259: authmsg = authenticated ? "Accepted" : "Failed";
260:
1.122 djm 261: if ((extra = format_method_key(authctxt)) == NULL) {
262: if (authctxt->auth_method_info != NULL)
263: extra = xstrdup(authctxt->auth_method_info);
264: }
265:
1.116 markus 266: authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
1.13 markus 267: authmsg,
268: method,
1.98 djm 269: submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
1.56 markus 270: authctxt->valid ? "" : "invalid user ",
1.29 markus 271: authctxt->user,
1.114 djm 272: ssh_remote_ipaddr(ssh),
273: ssh_remote_port(ssh),
1.122 djm 274: extra != NULL ? ": " : "",
275: extra != NULL ? extra : "");
276:
277: free(extra);
1.105 djm 278: }
279:
280: void
281: auth_maxtries_exceeded(Authctxt *authctxt)
282: {
1.114 djm 283: struct ssh *ssh = active_state; /* XXX */
284:
1.110 djm 285: error("maximum authentication attempts exceeded for "
1.116 markus 286: "%s%.100s from %.200s port %d ssh2",
1.105 djm 287: authctxt->valid ? "" : "invalid user ",
288: authctxt->user,
1.114 djm 289: ssh_remote_ipaddr(ssh),
1.116 markus 290: ssh_remote_port(ssh));
1.110 djm 291: packet_disconnect("Too many authentication failures");
1.105 djm 292: /* NOTREACHED */
1.13 markus 293: }
294:
295: /*
1.17 markus 296: * Check whether root logins are disallowed.
1.13 markus 297: */
298: int
1.98 djm 299: auth_root_allowed(const char *method)
1.13 markus 300: {
1.114 djm 301: struct ssh *ssh = active_state; /* XXX */
302:
1.17 markus 303: switch (options.permit_root_login) {
304: case PERMIT_YES:
1.13 markus 305: return 1;
1.17 markus 306: case PERMIT_NO_PASSWD:
1.112 deraadt 307: if (strcmp(method, "publickey") == 0 ||
308: strcmp(method, "hostbased") == 0 ||
1.113 djm 309: strcmp(method, "gssapi-with-mic") == 0)
1.17 markus 310: return 1;
311: break;
312: case PERMIT_FORCED_ONLY:
313: if (forced_command) {
1.47 itojun 314: logit("Root login accepted for forced command.");
1.17 markus 315: return 1;
316: }
317: break;
1.13 markus 318: }
1.114 djm 319: logit("ROOT LOGIN REFUSED FROM %.200s port %d",
320: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.22 markus 321: return 0;
322: }
323:
324:
325: /*
326: * Given a template and a passwd structure, build a filename
327: * by substituting % tokenised options. Currently, %% becomes '%',
328: * %h becomes the home directory and %u the username.
329: *
330: * This returns a buffer allocated by xmalloc.
331: */
1.93 djm 332: char *
1.59 djm 333: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 334: {
1.109 deraadt 335: char *file, ret[PATH_MAX];
1.65 djm 336: int i;
1.22 markus 337:
1.59 djm 338: file = percent_expand(filename, "h", pw->pw_dir,
339: "u", pw->pw_name, (char *)NULL);
1.22 markus 340:
341: /*
342: * Ensure that filename starts anchored. If not, be backward
343: * compatible and prepend the '%h/'
344: */
1.59 djm 345: if (*file == '/')
346: return (file);
347:
1.65 djm 348: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
349: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 350: fatal("expand_authorized_keys: path too long");
1.102 djm 351: free(file);
1.65 djm 352: return (xstrdup(ret));
1.22 markus 353: }
1.24 markus 354:
1.87 djm 355: char *
356: authorized_principals_file(struct passwd *pw)
357: {
1.111 djm 358: if (options.authorized_principals_file == NULL)
1.87 djm 359: return NULL;
360: return expand_authorized_keys(options.authorized_principals_file, pw);
361: }
362:
1.24 markus 363: /* return ok if key exists in sysfile or userfile */
364: HostStatus
1.121 markus 365: check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
1.24 markus 366: const char *sysfile, const char *userfile)
367: {
368: char *user_hostfile;
369: struct stat st;
1.30 stevesk 370: HostStatus host_status;
1.91 djm 371: struct hostkeys *hostkeys;
372: const struct hostkey_entry *found;
1.24 markus 373:
1.91 djm 374: hostkeys = init_hostkeys();
375: load_hostkeys(hostkeys, host, sysfile);
376: if (userfile != NULL) {
1.24 markus 377: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
378: if (options.strict_modes &&
379: (stat(user_hostfile, &st) == 0) &&
380: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 381: (st.st_mode & 022) != 0)) {
1.47 itojun 382: logit("Authentication refused for %.100s: "
1.24 markus 383: "bad owner or modes for %.200s",
384: pw->pw_name, user_hostfile);
1.88 djm 385: auth_debug_add("Ignored %.200s: bad ownership or modes",
386: user_hostfile);
1.24 markus 387: } else {
388: temporarily_use_uid(pw);
1.91 djm 389: load_hostkeys(hostkeys, host, user_hostfile);
1.24 markus 390: restore_uid();
391: }
1.102 djm 392: free(user_hostfile);
1.24 markus 393: }
1.91 djm 394: host_status = check_key_in_hostkeys(hostkeys, key, &found);
395: if (host_status == HOST_REVOKED)
396: error("WARNING: revoked key for %s attempted authentication",
397: found->host);
398: else if (host_status == HOST_OK)
399: debug("%s: key for %s found at %s:%ld", __func__,
400: found->host, found->file, found->line);
401: else
402: debug("%s: key for host %s not found", __func__, host);
403:
404: free_hostkeys(hostkeys);
1.24 markus 405:
406: return host_status;
407: }
408:
1.87 djm 409: static FILE *
410: auth_openfile(const char *file, struct passwd *pw, int strict_modes,
411: int log_missing, char *file_type)
1.79 dtucker 412: {
413: char line[1024];
414: struct stat st;
415: int fd;
416: FILE *f;
417:
1.81 dtucker 418: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
1.87 djm 419: if (log_missing || errno != ENOENT)
420: debug("Could not open %s '%s': %s", file_type, file,
1.81 dtucker 421: strerror(errno));
1.79 dtucker 422: return NULL;
1.81 dtucker 423: }
1.79 dtucker 424:
425: if (fstat(fd, &st) < 0) {
426: close(fd);
427: return NULL;
428: }
429: if (!S_ISREG(st.st_mode)) {
1.87 djm 430: logit("User %s %s %s is not a regular file",
431: pw->pw_name, file_type, file);
1.79 dtucker 432: close(fd);
433: return NULL;
434: }
435: unset_nonblock(fd);
436: if ((f = fdopen(fd, "r")) == NULL) {
437: close(fd);
438: return NULL;
439: }
1.90 djm 440: if (strict_modes &&
1.123 djm 441: safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
1.79 dtucker 442: fclose(f);
443: logit("Authentication refused: %s", line);
1.88 djm 444: auth_debug_add("Ignored %s: %s", file_type, line);
1.79 dtucker 445: return NULL;
446: }
447:
448: return f;
1.87 djm 449: }
450:
451:
452: FILE *
453: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
454: {
455: return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
456: }
457:
458: FILE *
459: auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
460: {
461: return auth_openfile(file, pw, strict_modes, 0,
462: "authorized principals");
1.37 provos 463: }
464:
465: struct passwd *
466: getpwnamallow(const char *user)
467: {
1.114 djm 468: struct ssh *ssh = active_state; /* XXX */
1.38 provos 469: extern login_cap_t *lc;
470: auth_session_t *as;
1.37 provos 471: struct passwd *pw;
1.96 dtucker 472: struct connection_info *ci = get_connection_info(1, options.use_dns);
1.71 dtucker 473:
1.96 dtucker 474: ci->user = user;
475: parse_server_match_config(&options, ci);
1.120 djm 476: log_change_level(options.log_level);
1.124 djm 477: process_permitopen(ssh, &options);
1.37 provos 478:
479: pw = getpwnam(user);
1.45 stevesk 480: if (pw == NULL) {
1.114 djm 481: logit("Invalid user %.100s from %.100s port %d",
482: user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.45 stevesk 483: return (NULL);
484: }
485: if (!allowed_user(pw))
1.38 provos 486: return (NULL);
487: if ((lc = login_getclass(pw->pw_class)) == NULL) {
488: debug("unable to get login class: %s", user);
489: return (NULL);
490: }
491: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 492: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 493: debug("Approval failure for %s", user);
1.37 provos 494: pw = NULL;
1.38 provos 495: }
496: if (as != NULL)
497: auth_close(as);
1.41 markus 498: if (pw != NULL)
499: return (pwcopy(pw));
500: return (NULL);
1.85 djm 501: }
502:
503: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
504: int
1.121 markus 505: auth_key_is_revoked(struct sshkey *key)
1.85 djm 506: {
1.107 djm 507: char *fp = NULL;
508: int r;
1.85 djm 509:
510: if (options.revoked_keys_file == NULL)
511: return 0;
1.108 djm 512: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
513: SSH_FP_DEFAULT)) == NULL) {
1.107 djm 514: r = SSH_ERR_ALLOC_FAIL;
515: error("%s: fingerprint key: %s", __func__, ssh_err(r));
516: goto out;
517: }
518:
519: r = sshkey_check_revoked(key, options.revoked_keys_file);
520: switch (r) {
1.100 djm 521: case 0:
1.107 djm 522: break; /* not revoked */
523: case SSH_ERR_KEY_REVOKED:
524: error("Authentication key %s %s revoked by file %s",
525: sshkey_type(key), fp, options.revoked_keys_file);
526: goto out;
1.100 djm 527: default:
1.107 djm 528: error("Error checking authentication key %s %s in "
529: "revoked keys file %s: %s", sshkey_type(key), fp,
530: options.revoked_keys_file, ssh_err(r));
531: goto out;
1.100 djm 532: }
1.107 djm 533:
534: /* Success */
535: r = 0;
536:
537: out:
538: free(fp);
539: return r == 0 ? 0 : 1;
1.42 markus 540: }
541:
542: void
543: auth_debug_add(const char *fmt,...)
544: {
545: char buf[1024];
546: va_list args;
547:
548: if (!auth_debug_init)
549: return;
550:
551: va_start(args, fmt);
552: vsnprintf(buf, sizeof(buf), fmt, args);
553: va_end(args);
554: buffer_put_cstring(&auth_debug, buf);
555: }
556:
557: void
558: auth_debug_send(void)
559: {
560: char *msg;
561:
562: if (!auth_debug_init)
563: return;
564: while (buffer_len(&auth_debug)) {
565: msg = buffer_get_string(&auth_debug, NULL);
566: packet_send_debug("%s", msg);
1.102 djm 567: free(msg);
1.42 markus 568: }
569: }
570:
571: void
572: auth_debug_reset(void)
573: {
574: if (auth_debug_init)
575: buffer_clear(&auth_debug);
576: else {
577: buffer_init(&auth_debug);
578: auth_debug_init = 1;
579: }
1.49 markus 580: }
581:
582: struct passwd *
583: fakepw(void)
584: {
585: static struct passwd fake;
586:
587: memset(&fake, 0, sizeof(fake));
588: fake.pw_name = "NOUSER";
589: fake.pw_passwd =
1.51 djm 590: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 591: fake.pw_gecos = "NOUSER";
1.53 deraadt 592: fake.pw_uid = (uid_t)-1;
593: fake.pw_gid = (gid_t)-1;
1.49 markus 594: fake.pw_class = "";
595: fake.pw_dir = "/nonexist";
596: fake.pw_shell = "/nonexist";
597:
598: return (&fake);
1.114 djm 599: }
600:
601: /*
602: * Returns the remote DNS hostname as a string. The returned string must not
603: * be freed. NB. this will usually trigger a DNS query the first time it is
604: * called.
605: * This function does additional checks on the hostname to mitigate some
606: * attacks on legacy rhosts-style authentication.
607: * XXX is RhostsRSAAuthentication vulnerable to these?
608: * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
609: */
610:
611: static char *
612: remote_hostname(struct ssh *ssh)
613: {
614: struct sockaddr_storage from;
615: socklen_t fromlen;
616: struct addrinfo hints, *ai, *aitop;
617: char name[NI_MAXHOST], ntop2[NI_MAXHOST];
618: const char *ntop = ssh_remote_ipaddr(ssh);
619:
620: /* Get IP address of client. */
621: fromlen = sizeof(from);
622: memset(&from, 0, sizeof(from));
623: if (getpeername(ssh_packet_get_connection_in(ssh),
624: (struct sockaddr *)&from, &fromlen) < 0) {
625: debug("getpeername failed: %.100s", strerror(errno));
626: return strdup(ntop);
627: }
628:
629: debug3("Trying to reverse map address %.100s.", ntop);
630: /* Map the IP address to a host name. */
631: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
632: NULL, 0, NI_NAMEREQD) != 0) {
633: /* Host name not found. Use ip address. */
634: return strdup(ntop);
635: }
636:
637: /*
638: * if reverse lookup result looks like a numeric hostname,
639: * someone is trying to trick us by PTR record like following:
640: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
641: */
642: memset(&hints, 0, sizeof(hints));
643: hints.ai_socktype = SOCK_DGRAM; /*dummy*/
644: hints.ai_flags = AI_NUMERICHOST;
645: if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
646: logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
647: name, ntop);
648: freeaddrinfo(ai);
649: return strdup(ntop);
650: }
651:
652: /* Names are stored in lowercase. */
653: lowercase(name);
654:
655: /*
656: * Map it back to an IP address and check that the given
657: * address actually is an address of this host. This is
658: * necessary because anyone with access to a name server can
659: * define arbitrary names for an IP address. Mapping from
660: * name to IP address can be trusted better (but can still be
661: * fooled if the intruder has access to the name server of
662: * the domain).
663: */
664: memset(&hints, 0, sizeof(hints));
665: hints.ai_family = from.ss_family;
666: hints.ai_socktype = SOCK_STREAM;
667: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
668: logit("reverse mapping checking getaddrinfo for %.700s "
1.115 dtucker 669: "[%s] failed.", name, ntop);
1.114 djm 670: return strdup(ntop);
671: }
672: /* Look for the address from the list of addresses. */
673: for (ai = aitop; ai; ai = ai->ai_next) {
674: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
675: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
676: (strcmp(ntop, ntop2) == 0))
677: break;
678: }
679: freeaddrinfo(aitop);
680: /* If we reached the end of the list, the address was not there. */
681: if (ai == NULL) {
682: /* Address not found for the host name. */
683: logit("Address %.100s maps to %.600s, but this does not "
1.115 dtucker 684: "map back to the address.", ntop, name);
1.114 djm 685: return strdup(ntop);
686: }
687: return strdup(name);
688: }
689:
690: /*
691: * Return the canonical name of the host in the other side of the current
692: * connection. The host name is cached, so it is efficient to call this
693: * several times.
694: */
695:
696: const char *
697: auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
698: {
699: static char *dnsname;
700:
701: if (!use_dns)
702: return ssh_remote_ipaddr(ssh);
703: else if (dnsname != NULL)
704: return dnsname;
705: else {
706: dnsname = remote_hostname(ssh);
707: return dnsname;
708: }
1.125 ! markus 709: }
! 710:
! 711: /*
! 712: * Runs command in a subprocess wuth a minimal environment.
! 713: * Returns pid on success, 0 on failure.
! 714: * The child stdout and stderr maybe captured, left attached or sent to
! 715: * /dev/null depending on the contents of flags.
! 716: * "tag" is prepended to log messages.
! 717: * NB. "command" is only used for logging; the actual command executed is
! 718: * av[0].
! 719: */
! 720: pid_t
! 721: subprocess(const char *tag, struct passwd *pw, const char *command,
! 722: int ac, char **av, FILE **child, u_int flags)
! 723: {
! 724: FILE *f = NULL;
! 725: struct stat st;
! 726: int fd, devnull, p[2], i;
! 727: pid_t pid;
! 728: char *cp, errmsg[512];
! 729: u_int envsize;
! 730: char **child_env;
! 731:
! 732: if (child != NULL)
! 733: *child = NULL;
! 734:
! 735: debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
! 736: tag, command, pw->pw_name, flags);
! 737:
! 738: /* Check consistency */
! 739: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
! 740: (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
! 741: error("%s: inconsistent flags", __func__);
! 742: return 0;
! 743: }
! 744: if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
! 745: error("%s: inconsistent flags/output", __func__);
! 746: return 0;
! 747: }
! 748:
! 749: /*
! 750: * If executing an explicit binary, then verify the it exists
! 751: * and appears safe-ish to execute
! 752: */
! 753: if (*av[0] != '/') {
! 754: error("%s path is not absolute", tag);
! 755: return 0;
! 756: }
! 757: temporarily_use_uid(pw);
! 758: if (stat(av[0], &st) < 0) {
! 759: error("Could not stat %s \"%s\": %s", tag,
! 760: av[0], strerror(errno));
! 761: restore_uid();
! 762: return 0;
! 763: }
! 764: if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
! 765: error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
! 766: restore_uid();
! 767: return 0;
! 768: }
! 769: /* Prepare to keep the child's stdout if requested */
! 770: if (pipe(p) != 0) {
! 771: error("%s: pipe: %s", tag, strerror(errno));
! 772: restore_uid();
! 773: return 0;
! 774: }
! 775: restore_uid();
! 776:
! 777: switch ((pid = fork())) {
! 778: case -1: /* error */
! 779: error("%s: fork: %s", tag, strerror(errno));
! 780: close(p[0]);
! 781: close(p[1]);
! 782: return 0;
! 783: case 0: /* child */
! 784: /* Prepare a minimal environment for the child. */
! 785: envsize = 5;
! 786: child_env = xcalloc(sizeof(*child_env), envsize);
! 787: child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
! 788: child_set_env(&child_env, &envsize, "USER", pw->pw_name);
! 789: child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
! 790: child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
! 791: if ((cp = getenv("LANG")) != NULL)
! 792: child_set_env(&child_env, &envsize, "LANG", cp);
! 793:
! 794: for (i = 0; i < NSIG; i++)
! 795: signal(i, SIG_DFL);
! 796:
! 797: if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
! 798: error("%s: open %s: %s", tag, _PATH_DEVNULL,
! 799: strerror(errno));
! 800: _exit(1);
! 801: }
! 802: if (dup2(devnull, STDIN_FILENO) == -1) {
! 803: error("%s: dup2: %s", tag, strerror(errno));
! 804: _exit(1);
! 805: }
! 806:
! 807: /* Set up stdout as requested; leave stderr in place for now. */
! 808: fd = -1;
! 809: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
! 810: fd = p[1];
! 811: else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
! 812: fd = devnull;
! 813: if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
! 814: error("%s: dup2: %s", tag, strerror(errno));
! 815: _exit(1);
! 816: }
! 817: closefrom(STDERR_FILENO + 1);
! 818:
! 819: /* Don't use permanently_set_uid() here to avoid fatal() */
! 820: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
! 821: error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
! 822: strerror(errno));
! 823: _exit(1);
! 824: }
! 825: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
! 826: error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
! 827: strerror(errno));
! 828: _exit(1);
! 829: }
! 830: /* stdin is pointed to /dev/null at this point */
! 831: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
! 832: dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
! 833: error("%s: dup2: %s", tag, strerror(errno));
! 834: _exit(1);
! 835: }
! 836:
! 837: execve(av[0], av, child_env);
! 838: error("%s exec \"%s\": %s", tag, command, strerror(errno));
! 839: _exit(127);
! 840: default: /* parent */
! 841: break;
! 842: }
! 843:
! 844: close(p[1]);
! 845: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
! 846: close(p[0]);
! 847: else if ((f = fdopen(p[0], "r")) == NULL) {
! 848: error("%s: fdopen: %s", tag, strerror(errno));
! 849: close(p[0]);
! 850: /* Don't leave zombie child */
! 851: kill(pid, SIGTERM);
! 852: while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
! 853: ;
! 854: return 0;
! 855: }
! 856: /* Success */
! 857: debug3("%s: %s pid %ld", __func__, tag, (long)pid);
! 858: if (child != NULL)
! 859: *child = f;
! 860: return pid;
1.1 markus 861: }
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