Annotation of src/usr.bin/ssh/auth.c, Revision 1.142
1.142 ! djm 1: /* $OpenBSD: auth.c,v 1.141 2019/10/02 00:42:30 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;
1.67 dtucker 70: extern int use_privsep;
1.126 djm 71: extern struct sshauthopt *auth_opts;
1.1 markus 72:
1.42 markus 73: /* Debugging messages */
1.131 markus 74: static struct sshbuf *auth_debug;
1.42 markus 75:
1.1 markus 76: /*
1.12 markus 77: * Check if the user is allowed to log in via ssh. If user is listed
78: * in DenyUsers or one of user's groups is listed in DenyGroups, false
79: * will be returned. If AllowUsers isn't empty and user isn't listed
80: * there, or if AllowGroups isn't empty and one of user's groups isn't
81: * listed there, false will be returned.
1.1 markus 82: * If the user's shell is not executable, false will be returned.
1.4 markus 83: * Otherwise true is returned.
1.1 markus 84: */
1.5 markus 85: int
1.138 djm 86: allowed_user(struct ssh *ssh, struct passwd * pw)
1.1 markus 87: {
88: struct stat st;
1.35 markus 89: const char *hostname = NULL, *ipaddr = NULL;
1.117 djm 90: int r;
1.60 djm 91: u_int i;
1.1 markus 92:
93: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 94: if (!pw || !pw->pw_name)
1.1 markus 95: return 0;
96:
1.7 deraadt 97: /*
1.84 djm 98: * Deny if shell does not exist or is not executable unless we
99: * are chrooting.
1.7 deraadt 100: */
1.84 djm 101: if (options.chroot_directory == NULL ||
102: strcasecmp(options.chroot_directory, "none") == 0) {
103: char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
104: _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
105:
1.139 deraadt 106: if (stat(shell, &st) == -1) {
1.84 djm 107: logit("User %.100s not allowed because shell %.100s "
108: "does not exist", pw->pw_name, shell);
1.102 djm 109: free(shell);
1.84 djm 110: return 0;
111: }
112: if (S_ISREG(st.st_mode) == 0 ||
113: (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
114: logit("User %.100s not allowed because shell %.100s "
115: "is not executable", pw->pw_name, shell);
1.102 djm 116: free(shell);
1.84 djm 117: return 0;
118: }
1.102 djm 119: free(shell);
1.34 stevesk 120: }
1.1 markus 121:
1.58 dtucker 122: if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
123: options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.114 djm 124: hostname = auth_get_canonical_hostname(ssh, options.use_dns);
125: ipaddr = ssh_remote_ipaddr(ssh);
1.35 markus 126: }
127:
1.1 markus 128: /* Return false if user is listed in DenyUsers */
129: if (options.num_deny_users > 0) {
1.119 dtucker 130: for (i = 0; i < options.num_deny_users; i++) {
1.117 djm 131: r = match_user(pw->pw_name, hostname, ipaddr,
132: options.deny_users[i]);
133: if (r < 0) {
134: fatal("Invalid DenyUsers pattern \"%.100s\"",
135: options.deny_users[i]);
1.118 djm 136: } else if (r != 0) {
1.57 dtucker 137: logit("User %.100s from %.100s not allowed "
138: "because listed in DenyUsers",
139: pw->pw_name, hostname);
1.1 markus 140: return 0;
1.34 stevesk 141: }
1.119 dtucker 142: }
1.1 markus 143: }
144: /* Return false if AllowUsers isn't empty and user isn't listed there */
145: if (options.num_allow_users > 0) {
1.117 djm 146: for (i = 0; i < options.num_allow_users; i++) {
147: r = match_user(pw->pw_name, hostname, ipaddr,
148: options.allow_users[i]);
149: if (r < 0) {
150: fatal("Invalid AllowUsers pattern \"%.100s\"",
151: options.allow_users[i]);
152: } else if (r == 1)
1.1 markus 153: break;
1.117 djm 154: }
1.1 markus 155: /* i < options.num_allow_users iff we break for loop */
1.34 stevesk 156: if (i >= options.num_allow_users) {
1.57 dtucker 157: logit("User %.100s from %.100s not allowed because "
158: "not listed in AllowUsers", pw->pw_name, hostname);
1.1 markus 159: return 0;
1.34 stevesk 160: }
1.1 markus 161: }
162: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 163: /* Get the user's group access list (primary and supplementary) */
1.34 stevesk 164: if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
1.57 dtucker 165: logit("User %.100s from %.100s not allowed because "
166: "not in any group", pw->pw_name, hostname);
1.1 markus 167: return 0;
1.34 stevesk 168: }
1.1 markus 169:
1.12 markus 170: /* Return false if one of user's groups is listed in DenyGroups */
171: if (options.num_deny_groups > 0)
172: if (ga_match(options.deny_groups,
173: options.num_deny_groups)) {
174: ga_free();
1.57 dtucker 175: logit("User %.100s from %.100s not allowed "
176: "because a group is listed in DenyGroups",
177: pw->pw_name, hostname);
1.1 markus 178: return 0;
1.12 markus 179: }
1.1 markus 180: /*
1.12 markus 181: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 182: * isn't listed there
183: */
1.12 markus 184: if (options.num_allow_groups > 0)
185: if (!ga_match(options.allow_groups,
186: options.num_allow_groups)) {
187: ga_free();
1.57 dtucker 188: logit("User %.100s from %.100s not allowed "
189: "because none of user's groups are listed "
190: "in AllowGroups", pw->pw_name, hostname);
1.1 markus 191: return 0;
1.12 markus 192: }
193: ga_free();
1.1 markus 194: }
195: /* We found no reason not to let this user try to log on... */
196: return 1;
1.13 markus 197: }
198:
1.122 djm 199: /*
200: * Formats any key left in authctxt->auth_method_key for inclusion in
201: * auth_log()'s message. Also includes authxtct->auth_method_info if present.
202: */
203: static char *
204: format_method_key(Authctxt *authctxt)
1.103 djm 205: {
1.122 djm 206: const struct sshkey *key = authctxt->auth_method_key;
207: const char *methinfo = authctxt->auth_method_info;
1.133 djm 208: char *fp, *cafp, *ret = NULL;
1.122 djm 209:
210: if (key == NULL)
211: return NULL;
212:
1.131 markus 213: if (sshkey_is_cert(key)) {
1.133 djm 214: fp = sshkey_fingerprint(key,
1.122 djm 215: options.fingerprint_hash, SSH_FP_DEFAULT);
1.133 djm 216: cafp = sshkey_fingerprint(key->cert->signature_key,
217: options.fingerprint_hash, SSH_FP_DEFAULT);
218: xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
219: sshkey_type(key), fp == NULL ? "(null)" : fp,
220: key->cert->key_id,
1.122 djm 221: (unsigned long long)key->cert->serial,
222: sshkey_type(key->cert->signature_key),
1.133 djm 223: cafp == NULL ? "(null)" : cafp,
1.122 djm 224: methinfo == NULL ? "" : ", ",
225: methinfo == NULL ? "" : methinfo);
226: free(fp);
1.133 djm 227: free(cafp);
1.122 djm 228: } else {
229: fp = sshkey_fingerprint(key, options.fingerprint_hash,
230: SSH_FP_DEFAULT);
231: xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
232: fp == NULL ? "(null)" : fp,
233: methinfo == NULL ? "" : ", ",
234: methinfo == NULL ? "" : methinfo);
235: free(fp);
236: }
237: return ret;
1.103 djm 238: }
239:
240: void
1.138 djm 241: auth_log(struct ssh *ssh, int authenticated, int partial,
1.103 djm 242: const char *method, const char *submethod)
1.13 markus 243: {
1.138 djm 244: Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1.133 djm 245: int level = SYSLOG_LEVEL_VERBOSE;
1.122 djm 246: const char *authmsg;
247: char *extra = NULL;
1.67 dtucker 248:
249: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
250: return;
1.13 markus 251:
252: /* Raise logging level */
253: if (authenticated == 1 ||
254: !authctxt->valid ||
1.54 dtucker 255: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 256: strcmp(method, "password") == 0)
1.133 djm 257: level = SYSLOG_LEVEL_INFO;
1.13 markus 258:
259: if (authctxt->postponed)
260: authmsg = "Postponed";
1.98 djm 261: else if (partial)
262: authmsg = "Partial";
1.13 markus 263: else
264: authmsg = authenticated ? "Accepted" : "Failed";
265:
1.122 djm 266: if ((extra = format_method_key(authctxt)) == NULL) {
267: if (authctxt->auth_method_info != NULL)
268: extra = xstrdup(authctxt->auth_method_info);
269: }
270:
1.133 djm 271: do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
1.13 markus 272: authmsg,
273: method,
1.98 djm 274: submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
1.56 markus 275: authctxt->valid ? "" : "invalid user ",
1.29 markus 276: authctxt->user,
1.114 djm 277: ssh_remote_ipaddr(ssh),
278: ssh_remote_port(ssh),
1.122 djm 279: extra != NULL ? ": " : "",
280: extra != NULL ? extra : "");
281:
282: free(extra);
1.105 djm 283: }
284:
285: void
1.138 djm 286: auth_maxtries_exceeded(struct ssh *ssh)
1.105 djm 287: {
1.138 djm 288: Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1.114 djm 289:
1.110 djm 290: error("maximum authentication attempts exceeded for "
1.116 markus 291: "%s%.100s from %.200s port %d ssh2",
1.105 djm 292: authctxt->valid ? "" : "invalid user ",
293: authctxt->user,
1.114 djm 294: ssh_remote_ipaddr(ssh),
1.116 markus 295: ssh_remote_port(ssh));
1.138 djm 296: ssh_packet_disconnect(ssh, "Too many authentication failures");
1.105 djm 297: /* NOTREACHED */
1.13 markus 298: }
299:
300: /*
1.17 markus 301: * Check whether root logins are disallowed.
1.13 markus 302: */
303: int
1.126 djm 304: auth_root_allowed(struct ssh *ssh, const char *method)
1.13 markus 305: {
1.17 markus 306: switch (options.permit_root_login) {
307: case PERMIT_YES:
1.13 markus 308: return 1;
1.17 markus 309: case PERMIT_NO_PASSWD:
1.112 deraadt 310: if (strcmp(method, "publickey") == 0 ||
311: strcmp(method, "hostbased") == 0 ||
1.113 djm 312: strcmp(method, "gssapi-with-mic") == 0)
1.17 markus 313: return 1;
314: break;
315: case PERMIT_FORCED_ONLY:
1.126 djm 316: if (auth_opts->force_command != NULL) {
1.47 itojun 317: logit("Root login accepted for forced command.");
1.17 markus 318: return 1;
319: }
320: break;
1.13 markus 321: }
1.114 djm 322: logit("ROOT LOGIN REFUSED FROM %.200s port %d",
323: ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.22 markus 324: return 0;
325: }
326:
327:
328: /*
329: * Given a template and a passwd structure, build a filename
330: * by substituting % tokenised options. Currently, %% becomes '%',
331: * %h becomes the home directory and %u the username.
332: *
333: * This returns a buffer allocated by xmalloc.
334: */
1.93 djm 335: char *
1.59 djm 336: expand_authorized_keys(const char *filename, struct passwd *pw)
1.22 markus 337: {
1.129 djm 338: char *file, uidstr[32], ret[PATH_MAX];
1.65 djm 339: int i;
1.22 markus 340:
1.129 djm 341: snprintf(uidstr, sizeof(uidstr), "%llu",
342: (unsigned long long)pw->pw_uid);
1.59 djm 343: file = percent_expand(filename, "h", pw->pw_dir,
1.129 djm 344: "u", pw->pw_name, "U", uidstr, (char *)NULL);
1.22 markus 345:
346: /*
347: * Ensure that filename starts anchored. If not, be backward
348: * compatible and prepend the '%h/'
349: */
1.134 djm 350: if (path_absolute(file))
1.59 djm 351: return (file);
352:
1.65 djm 353: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
354: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 355: fatal("expand_authorized_keys: path too long");
1.102 djm 356: free(file);
1.65 djm 357: return (xstrdup(ret));
1.22 markus 358: }
1.24 markus 359:
1.87 djm 360: char *
361: authorized_principals_file(struct passwd *pw)
362: {
1.111 djm 363: if (options.authorized_principals_file == NULL)
1.87 djm 364: return NULL;
365: return expand_authorized_keys(options.authorized_principals_file, pw);
366: }
367:
1.24 markus 368: /* return ok if key exists in sysfile or userfile */
369: HostStatus
1.121 markus 370: check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
1.24 markus 371: const char *sysfile, const char *userfile)
372: {
373: char *user_hostfile;
374: struct stat st;
1.30 stevesk 375: HostStatus host_status;
1.91 djm 376: struct hostkeys *hostkeys;
377: const struct hostkey_entry *found;
1.24 markus 378:
1.91 djm 379: hostkeys = init_hostkeys();
380: load_hostkeys(hostkeys, host, sysfile);
381: if (userfile != NULL) {
1.24 markus 382: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
383: if (options.strict_modes &&
384: (stat(user_hostfile, &st) == 0) &&
385: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 386: (st.st_mode & 022) != 0)) {
1.47 itojun 387: logit("Authentication refused for %.100s: "
1.24 markus 388: "bad owner or modes for %.200s",
389: pw->pw_name, user_hostfile);
1.88 djm 390: auth_debug_add("Ignored %.200s: bad ownership or modes",
391: user_hostfile);
1.24 markus 392: } else {
393: temporarily_use_uid(pw);
1.91 djm 394: load_hostkeys(hostkeys, host, user_hostfile);
1.24 markus 395: restore_uid();
396: }
1.102 djm 397: free(user_hostfile);
1.24 markus 398: }
1.91 djm 399: host_status = check_key_in_hostkeys(hostkeys, key, &found);
400: if (host_status == HOST_REVOKED)
401: error("WARNING: revoked key for %s attempted authentication",
1.142 ! djm 402: host);
1.91 djm 403: else if (host_status == HOST_OK)
404: debug("%s: key for %s found at %s:%ld", __func__,
405: found->host, found->file, found->line);
406: else
407: debug("%s: key for host %s not found", __func__, host);
408:
409: free_hostkeys(hostkeys);
1.24 markus 410:
411: return host_status;
412: }
413:
1.87 djm 414: static FILE *
415: auth_openfile(const char *file, struct passwd *pw, int strict_modes,
416: int log_missing, char *file_type)
1.79 dtucker 417: {
418: char line[1024];
419: struct stat st;
420: int fd;
421: FILE *f;
422:
1.81 dtucker 423: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
1.87 djm 424: if (log_missing || errno != ENOENT)
425: debug("Could not open %s '%s': %s", file_type, file,
1.81 dtucker 426: strerror(errno));
1.79 dtucker 427: return NULL;
1.81 dtucker 428: }
1.79 dtucker 429:
1.139 deraadt 430: if (fstat(fd, &st) == -1) {
1.79 dtucker 431: close(fd);
432: return NULL;
433: }
434: if (!S_ISREG(st.st_mode)) {
1.87 djm 435: logit("User %s %s %s is not a regular file",
436: pw->pw_name, file_type, file);
1.79 dtucker 437: close(fd);
438: return NULL;
439: }
440: unset_nonblock(fd);
441: if ((f = fdopen(fd, "r")) == NULL) {
442: close(fd);
443: return NULL;
444: }
1.90 djm 445: if (strict_modes &&
1.123 djm 446: safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
1.79 dtucker 447: fclose(f);
448: logit("Authentication refused: %s", line);
1.88 djm 449: auth_debug_add("Ignored %s: %s", file_type, line);
1.79 dtucker 450: return NULL;
451: }
452:
453: return f;
1.87 djm 454: }
455:
456:
457: FILE *
458: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
459: {
460: return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
461: }
462:
463: FILE *
464: auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
465: {
466: return auth_openfile(file, pw, strict_modes, 0,
467: "authorized principals");
1.37 provos 468: }
469:
470: struct passwd *
1.138 djm 471: getpwnamallow(struct ssh *ssh, const char *user)
1.37 provos 472: {
1.38 provos 473: extern login_cap_t *lc;
474: auth_session_t *as;
1.37 provos 475: struct passwd *pw;
1.137 djm 476: struct connection_info *ci;
1.71 dtucker 477:
1.137 djm 478: ci = get_connection_info(ssh, 1, options.use_dns);
1.96 dtucker 479: ci->user = user;
480: parse_server_match_config(&options, ci);
1.120 djm 481: log_change_level(options.log_level);
1.124 djm 482: process_permitopen(ssh, &options);
1.37 provos 483:
484: pw = getpwnam(user);
1.45 stevesk 485: if (pw == NULL) {
1.114 djm 486: logit("Invalid user %.100s from %.100s port %d",
487: user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.45 stevesk 488: return (NULL);
489: }
1.138 djm 490: if (!allowed_user(ssh, pw))
1.38 provos 491: return (NULL);
492: if ((lc = login_getclass(pw->pw_class)) == NULL) {
493: debug("unable to get login class: %s", user);
494: return (NULL);
495: }
496: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 497: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 498: debug("Approval failure for %s", user);
1.37 provos 499: pw = NULL;
1.38 provos 500: }
501: if (as != NULL)
502: auth_close(as);
1.41 markus 503: if (pw != NULL)
504: return (pwcopy(pw));
505: return (NULL);
1.85 djm 506: }
507:
508: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
509: int
1.121 markus 510: auth_key_is_revoked(struct sshkey *key)
1.85 djm 511: {
1.107 djm 512: char *fp = NULL;
513: int r;
1.85 djm 514:
515: if (options.revoked_keys_file == NULL)
516: return 0;
1.108 djm 517: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
518: SSH_FP_DEFAULT)) == NULL) {
1.107 djm 519: r = SSH_ERR_ALLOC_FAIL;
520: error("%s: fingerprint key: %s", __func__, ssh_err(r));
521: goto out;
522: }
523:
524: r = sshkey_check_revoked(key, options.revoked_keys_file);
525: switch (r) {
1.100 djm 526: case 0:
1.107 djm 527: break; /* not revoked */
528: case SSH_ERR_KEY_REVOKED:
529: error("Authentication key %s %s revoked by file %s",
530: sshkey_type(key), fp, options.revoked_keys_file);
531: goto out;
1.100 djm 532: default:
1.107 djm 533: error("Error checking authentication key %s %s in "
534: "revoked keys file %s: %s", sshkey_type(key), fp,
535: options.revoked_keys_file, ssh_err(r));
536: goto out;
1.100 djm 537: }
1.107 djm 538:
539: /* Success */
540: r = 0;
541:
542: out:
543: free(fp);
544: return r == 0 ? 0 : 1;
1.42 markus 545: }
546:
547: void
548: auth_debug_add(const char *fmt,...)
549: {
550: char buf[1024];
551: va_list args;
1.131 markus 552: int r;
1.42 markus 553:
1.131 markus 554: if (auth_debug == NULL)
1.42 markus 555: return;
556:
557: va_start(args, fmt);
558: vsnprintf(buf, sizeof(buf), fmt, args);
559: va_end(args);
1.131 markus 560: if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
561: fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r));
1.42 markus 562: }
563:
564: void
1.138 djm 565: auth_debug_send(struct ssh *ssh)
1.42 markus 566: {
567: char *msg;
1.131 markus 568: int r;
1.42 markus 569:
1.131 markus 570: if (auth_debug == NULL)
1.42 markus 571: return;
1.131 markus 572: while (sshbuf_len(auth_debug) != 0) {
573: if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
574: fatal("%s: sshbuf_get_cstring: %s",
575: __func__, ssh_err(r));
576: ssh_packet_send_debug(ssh, "%s", msg);
1.102 djm 577: free(msg);
1.42 markus 578: }
579: }
580:
581: void
582: auth_debug_reset(void)
583: {
1.131 markus 584: if (auth_debug != NULL)
585: sshbuf_reset(auth_debug);
586: else if ((auth_debug = sshbuf_new()) == NULL)
587: fatal("%s: sshbuf_new failed", __func__);
1.49 markus 588: }
589:
590: struct passwd *
591: fakepw(void)
592: {
593: static struct passwd fake;
594:
595: memset(&fake, 0, sizeof(fake));
596: fake.pw_name = "NOUSER";
597: fake.pw_passwd =
1.51 djm 598: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 599: fake.pw_gecos = "NOUSER";
1.53 deraadt 600: fake.pw_uid = (uid_t)-1;
601: fake.pw_gid = (gid_t)-1;
1.49 markus 602: fake.pw_class = "";
603: fake.pw_dir = "/nonexist";
604: fake.pw_shell = "/nonexist";
605:
606: return (&fake);
1.114 djm 607: }
608:
609: /*
610: * Returns the remote DNS hostname as a string. The returned string must not
611: * be freed. NB. this will usually trigger a DNS query the first time it is
612: * called.
613: * This function does additional checks on the hostname to mitigate some
614: * attacks on legacy rhosts-style authentication.
615: * XXX is RhostsRSAAuthentication vulnerable to these?
616: * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
617: */
618:
619: static char *
620: remote_hostname(struct ssh *ssh)
621: {
622: struct sockaddr_storage from;
623: socklen_t fromlen;
624: struct addrinfo hints, *ai, *aitop;
625: char name[NI_MAXHOST], ntop2[NI_MAXHOST];
626: const char *ntop = ssh_remote_ipaddr(ssh);
627:
628: /* Get IP address of client. */
629: fromlen = sizeof(from);
630: memset(&from, 0, sizeof(from));
631: if (getpeername(ssh_packet_get_connection_in(ssh),
1.139 deraadt 632: (struct sockaddr *)&from, &fromlen) == -1) {
1.114 djm 633: debug("getpeername failed: %.100s", strerror(errno));
634: return strdup(ntop);
635: }
636:
637: debug3("Trying to reverse map address %.100s.", ntop);
638: /* Map the IP address to a host name. */
639: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
640: NULL, 0, NI_NAMEREQD) != 0) {
641: /* Host name not found. Use ip address. */
642: return strdup(ntop);
643: }
644:
645: /*
646: * if reverse lookup result looks like a numeric hostname,
647: * someone is trying to trick us by PTR record like following:
648: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
649: */
650: memset(&hints, 0, sizeof(hints));
651: hints.ai_socktype = SOCK_DGRAM; /*dummy*/
652: hints.ai_flags = AI_NUMERICHOST;
653: if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
654: logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
655: name, ntop);
656: freeaddrinfo(ai);
657: return strdup(ntop);
658: }
659:
660: /* Names are stored in lowercase. */
661: lowercase(name);
662:
663: /*
664: * Map it back to an IP address and check that the given
665: * address actually is an address of this host. This is
666: * necessary because anyone with access to a name server can
667: * define arbitrary names for an IP address. Mapping from
668: * name to IP address can be trusted better (but can still be
669: * fooled if the intruder has access to the name server of
670: * the domain).
671: */
672: memset(&hints, 0, sizeof(hints));
673: hints.ai_family = from.ss_family;
674: hints.ai_socktype = SOCK_STREAM;
675: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
676: logit("reverse mapping checking getaddrinfo for %.700s "
1.115 dtucker 677: "[%s] failed.", name, ntop);
1.114 djm 678: return strdup(ntop);
679: }
680: /* Look for the address from the list of addresses. */
681: for (ai = aitop; ai; ai = ai->ai_next) {
682: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
683: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
684: (strcmp(ntop, ntop2) == 0))
685: break;
686: }
687: freeaddrinfo(aitop);
688: /* If we reached the end of the list, the address was not there. */
689: if (ai == NULL) {
690: /* Address not found for the host name. */
691: logit("Address %.100s maps to %.600s, but this does not "
1.115 dtucker 692: "map back to the address.", ntop, name);
1.114 djm 693: return strdup(ntop);
694: }
695: return strdup(name);
696: }
697:
698: /*
699: * Return the canonical name of the host in the other side of the current
700: * connection. The host name is cached, so it is efficient to call this
701: * several times.
702: */
703:
704: const char *
705: auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
706: {
707: static char *dnsname;
708:
709: if (!use_dns)
710: return ssh_remote_ipaddr(ssh);
711: else if (dnsname != NULL)
712: return dnsname;
713: else {
714: dnsname = remote_hostname(ssh);
715: return dnsname;
716: }
1.125 markus 717: }
718:
719: /*
1.132 martijn 720: * Runs command in a subprocess with a minimal environment.
1.125 markus 721: * Returns pid on success, 0 on failure.
722: * The child stdout and stderr maybe captured, left attached or sent to
723: * /dev/null depending on the contents of flags.
724: * "tag" is prepended to log messages.
725: * NB. "command" is only used for logging; the actual command executed is
726: * av[0].
727: */
728: pid_t
729: subprocess(const char *tag, struct passwd *pw, const char *command,
730: int ac, char **av, FILE **child, u_int flags)
731: {
732: FILE *f = NULL;
733: struct stat st;
734: int fd, devnull, p[2], i;
735: pid_t pid;
736: char *cp, errmsg[512];
737: u_int envsize;
738: char **child_env;
739:
740: if (child != NULL)
741: *child = NULL;
742:
743: debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
744: tag, command, pw->pw_name, flags);
745:
746: /* Check consistency */
747: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
748: (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
749: error("%s: inconsistent flags", __func__);
750: return 0;
751: }
752: if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
753: error("%s: inconsistent flags/output", __func__);
754: return 0;
755: }
756:
757: /*
758: * If executing an explicit binary, then verify the it exists
759: * and appears safe-ish to execute
760: */
1.134 djm 761: if (!path_absolute(av[0])) {
1.125 markus 762: error("%s path is not absolute", tag);
763: return 0;
764: }
765: temporarily_use_uid(pw);
1.139 deraadt 766: if (stat(av[0], &st) == -1) {
1.125 markus 767: error("Could not stat %s \"%s\": %s", tag,
768: av[0], strerror(errno));
769: restore_uid();
770: return 0;
771: }
772: if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
773: error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
774: restore_uid();
775: return 0;
776: }
777: /* Prepare to keep the child's stdout if requested */
1.139 deraadt 778: if (pipe(p) == -1) {
1.125 markus 779: error("%s: pipe: %s", tag, strerror(errno));
780: restore_uid();
781: return 0;
782: }
783: restore_uid();
784:
785: switch ((pid = fork())) {
786: case -1: /* error */
787: error("%s: fork: %s", tag, strerror(errno));
788: close(p[0]);
789: close(p[1]);
790: return 0;
791: case 0: /* child */
792: /* Prepare a minimal environment for the child. */
793: envsize = 5;
794: child_env = xcalloc(sizeof(*child_env), envsize);
795: child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
796: child_set_env(&child_env, &envsize, "USER", pw->pw_name);
797: child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
798: child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
799: if ((cp = getenv("LANG")) != NULL)
800: child_set_env(&child_env, &envsize, "LANG", cp);
801:
802: for (i = 0; i < NSIG; i++)
803: signal(i, SIG_DFL);
804:
805: if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
806: error("%s: open %s: %s", tag, _PATH_DEVNULL,
807: strerror(errno));
808: _exit(1);
809: }
810: if (dup2(devnull, STDIN_FILENO) == -1) {
811: error("%s: dup2: %s", tag, strerror(errno));
812: _exit(1);
813: }
814:
815: /* Set up stdout as requested; leave stderr in place for now. */
816: fd = -1;
817: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
818: fd = p[1];
819: else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
820: fd = devnull;
821: if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
822: error("%s: dup2: %s", tag, strerror(errno));
823: _exit(1);
824: }
825: closefrom(STDERR_FILENO + 1);
826:
827: /* Don't use permanently_set_uid() here to avoid fatal() */
1.139 deraadt 828: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) {
1.125 markus 829: error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
830: strerror(errno));
831: _exit(1);
832: }
1.139 deraadt 833: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) {
1.125 markus 834: error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
835: strerror(errno));
836: _exit(1);
837: }
838: /* stdin is pointed to /dev/null at this point */
839: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
840: dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
841: error("%s: dup2: %s", tag, strerror(errno));
842: _exit(1);
843: }
844:
845: execve(av[0], av, child_env);
846: error("%s exec \"%s\": %s", tag, command, strerror(errno));
847: _exit(127);
848: default: /* parent */
849: break;
850: }
851:
852: close(p[1]);
853: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
854: close(p[0]);
855: else if ((f = fdopen(p[0], "r")) == NULL) {
856: error("%s: fdopen: %s", tag, strerror(errno));
857: close(p[0]);
858: /* Don't leave zombie child */
859: kill(pid, SIGTERM);
860: while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
861: ;
862: return 0;
863: }
864: /* Success */
865: debug3("%s: %s pid %ld", __func__, tag, (long)pid);
866: if (child != NULL)
867: *child = f;
868: return pid;
1.126 djm 869: }
870:
871: /* These functions link key/cert options to the auth framework */
872:
873: /* Log sshauthopt options locally and (optionally) for remote transmission */
874: void
875: auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
876: {
877: int do_env = options.permit_user_env && opts->nenv > 0;
878: int do_permitopen = opts->npermitopen > 0 &&
879: (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
1.130 djm 880: int do_permitlisten = opts->npermitlisten > 0 &&
881: (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
1.126 djm 882: size_t i;
1.127 djm 883: char msg[1024], buf[64];
1.126 djm 884:
1.127 djm 885: snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
1.126 djm 886: /* Try to keep this alphabetically sorted */
1.130 djm 887: snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s",
1.126 djm 888: opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
889: opts->force_command == NULL ? "" : " command",
890: do_env ? " environment" : "",
1.127 djm 891: opts->valid_before == 0 ? "" : "expires",
1.126 djm 892: do_permitopen ? " permitopen" : "",
1.130 djm 893: do_permitlisten ? " permitlisten" : "",
1.126 djm 894: opts->permit_port_forwarding_flag ? " port-forwarding" : "",
895: opts->cert_principals == NULL ? "" : " principals",
896: opts->permit_pty_flag ? " pty" : "",
897: opts->force_tun_device == -1 ? "" : " tun=",
1.127 djm 898: opts->force_tun_device == -1 ? "" : buf,
1.126 djm 899: opts->permit_user_rc ? " user-rc" : "",
900: opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
901:
902: debug("%s: %s", loc, msg);
903: if (do_remote)
904: auth_debug_add("%s: %s", loc, msg);
905:
906: if (options.permit_user_env) {
907: for (i = 0; i < opts->nenv; i++) {
908: debug("%s: environment: %s", loc, opts->env[i]);
909: if (do_remote) {
910: auth_debug_add("%s: environment: %s",
911: loc, opts->env[i]);
912: }
913: }
914: }
915:
916: /* Go into a little more details for the local logs. */
1.127 djm 917: if (opts->valid_before != 0) {
918: format_absolute_time(opts->valid_before, buf, sizeof(buf));
919: debug("%s: expires at %s", loc, buf);
920: }
1.126 djm 921: if (opts->cert_principals != NULL) {
922: debug("%s: authorized principals: \"%s\"",
923: loc, opts->cert_principals);
924: }
925: if (opts->force_command != NULL)
926: debug("%s: forced command: \"%s\"", loc, opts->force_command);
1.130 djm 927: if (do_permitopen) {
1.126 djm 928: for (i = 0; i < opts->npermitopen; i++) {
929: debug("%s: permitted open: %s",
930: loc, opts->permitopen[i]);
1.130 djm 931: }
932: }
933: if (do_permitlisten) {
934: for (i = 0; i < opts->npermitlisten; i++) {
935: debug("%s: permitted listen: %s",
936: loc, opts->permitlisten[i]);
1.126 djm 937: }
938: }
939: }
940:
941: /* Activate a new set of key/cert options; merging with what is there. */
942: int
943: auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
944: {
945: struct sshauthopt *old = auth_opts;
946: const char *emsg = NULL;
947:
948: debug("%s: setting new authentication options", __func__);
949: if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
950: error("Inconsistent authentication options: %s", emsg);
951: return -1;
952: }
953: return 0;
954: }
955:
956: /* Disable forwarding, etc for the session */
957: void
958: auth_restrict_session(struct ssh *ssh)
959: {
960: struct sshauthopt *restricted;
961:
962: debug("%s: restricting session", __func__);
963:
964: /* A blank sshauthopt defaults to permitting nothing */
965: restricted = sshauthopt_new();
1.128 djm 966: restricted->permit_pty_flag = 1;
1.126 djm 967: restricted->restricted = 1;
968:
969: if (auth_activate_options(ssh, restricted) != 0)
970: fatal("%s: failed to restrict session", __func__);
971: sshauthopt_free(restricted);
972: }
973:
974: int
975: auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
976: struct sshauthopt *opts, int allow_cert_authority, const char *loc)
977: {
978: const char *remote_ip = ssh_remote_ipaddr(ssh);
979: const char *remote_host = auth_get_canonical_hostname(ssh,
980: options.use_dns);
1.127 djm 981: time_t now = time(NULL);
982: char buf[64];
1.126 djm 983:
1.127 djm 984: /*
985: * Check keys/principals file expiry time.
986: * NB. validity interval in certificate is handled elsewhere.
987: */
988: if (opts->valid_before && now > 0 &&
989: opts->valid_before < (uint64_t)now) {
990: format_absolute_time(opts->valid_before, buf, sizeof(buf));
991: debug("%s: entry expired at %s", loc, buf);
992: auth_debug_add("%s: entry expired at %s", loc, buf);
993: return -1;
994: }
1.126 djm 995: /* Consistency checks */
996: if (opts->cert_principals != NULL && !opts->cert_authority) {
997: debug("%s: principals on non-CA key", loc);
998: auth_debug_add("%s: principals on non-CA key", loc);
999: /* deny access */
1000: return -1;
1001: }
1002: /* cert-authority flag isn't valid in authorized_principals files */
1003: if (!allow_cert_authority && opts->cert_authority) {
1004: debug("%s: cert-authority flag invalid here", loc);
1005: auth_debug_add("%s: cert-authority flag invalid here", loc);
1006: /* deny access */
1007: return -1;
1008: }
1009:
1010: /* Perform from= checks */
1011: if (opts->required_from_host_keys != NULL) {
1012: switch (match_host_and_ip(remote_host, remote_ip,
1013: opts->required_from_host_keys )) {
1014: case 1:
1015: /* Host name matches. */
1016: break;
1017: case -1:
1018: default:
1019: debug("%s: invalid from criteria", loc);
1020: auth_debug_add("%s: invalid from criteria", loc);
1021: /* FALLTHROUGH */
1022: case 0:
1023: logit("%s: Authentication tried for %.100s with "
1024: "correct key but not from a permitted "
1025: "host (host=%.200s, ip=%.200s, required=%.200s).",
1026: loc, pw->pw_name, remote_host, remote_ip,
1027: opts->required_from_host_keys);
1028: auth_debug_add("%s: Your host '%.200s' is not "
1029: "permitted to use this key for login.",
1030: loc, remote_host);
1031: /* deny access */
1032: return -1;
1033: }
1034: }
1035: /* Check source-address restriction from certificate */
1036: if (opts->required_from_host_cert != NULL) {
1037: switch (addr_match_cidr_list(remote_ip,
1038: opts->required_from_host_cert)) {
1039: case 1:
1040: /* accepted */
1041: break;
1042: case -1:
1043: default:
1044: /* invalid */
1045: error("%s: Certificate source-address invalid",
1046: loc);
1047: /* FALLTHROUGH */
1048: case 0:
1049: logit("%s: Authentication tried for %.100s with valid "
1050: "certificate but not from a permitted source "
1051: "address (%.200s).", loc, pw->pw_name, remote_ip);
1052: auth_debug_add("%s: Your address '%.200s' is not "
1053: "permitted to use this certificate for login.",
1054: loc, remote_ip);
1055: return -1;
1056: }
1057: }
1058: /*
1059: *
1060: * XXX this is spammy. We should report remotely only for keys
1061: * that are successful in actual auth attempts, and not PK_OK
1062: * tests.
1063: */
1064: auth_log_authopts(loc, opts, 1);
1065:
1066: return 0;
1.1 markus 1067: }