Annotation of src/usr.bin/ssh/auth.c, Revision 1.126
1.126 ! djm 1: /* $OpenBSD: auth.c,v 1.125 2018/01/08 15:21:49 markus 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"
1.126 ! djm 65: #include "channels.h"
1.2 markus 66:
1.1 markus 67: /* import */
68: extern ServerOptions options;
1.67 dtucker 69: extern int use_privsep;
1.126 ! djm 70: extern struct sshauthopt *auth_opts;
1.1 markus 71:
1.42 markus 72: /* Debugging messages */
73: Buffer auth_debug;
74: int auth_debug_init;
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
1.1 markus 86: allowed_user(struct passwd * pw)
87: {
1.114 djm 88: struct ssh *ssh = active_state; /* XXX */
1.1 markus 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:
107: if (stat(shell, &st) != 0) {
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;
209: char *fp, *ret = NULL;
210:
211: if (key == NULL)
212: return NULL;
213:
214: if (key_is_cert(key)) {
215: fp = sshkey_fingerprint(key->cert->signature_key,
216: options.fingerprint_hash, SSH_FP_DEFAULT);
217: xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s",
218: sshkey_type(key), key->cert->key_id,
219: (unsigned long long)key->cert->serial,
220: sshkey_type(key->cert->signature_key),
221: fp == NULL ? "(null)" : fp,
222: methinfo == NULL ? "" : ", ",
223: methinfo == NULL ? "" : methinfo);
224: free(fp);
225: } else {
226: fp = sshkey_fingerprint(key, options.fingerprint_hash,
227: SSH_FP_DEFAULT);
228: xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
229: fp == NULL ? "(null)" : fp,
230: methinfo == NULL ? "" : ", ",
231: methinfo == NULL ? "" : methinfo);
232: free(fp);
233: }
234: return ret;
1.103 djm 235: }
236:
237: void
1.98 djm 238: auth_log(Authctxt *authctxt, int authenticated, int partial,
1.103 djm 239: const char *method, const char *submethod)
1.13 markus 240: {
1.114 djm 241: struct ssh *ssh = active_state; /* XXX */
1.13 markus 242: void (*authlog) (const char *fmt,...) = verbose;
1.122 djm 243: const char *authmsg;
244: char *extra = NULL;
1.67 dtucker 245:
246: if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
247: return;
1.13 markus 248:
249: /* Raise logging level */
250: if (authenticated == 1 ||
251: !authctxt->valid ||
1.54 dtucker 252: authctxt->failures >= options.max_authtries / 2 ||
1.13 markus 253: strcmp(method, "password") == 0)
1.47 itojun 254: authlog = logit;
1.13 markus 255:
256: if (authctxt->postponed)
257: authmsg = "Postponed";
1.98 djm 258: else if (partial)
259: authmsg = "Partial";
1.13 markus 260: else
261: authmsg = authenticated ? "Accepted" : "Failed";
262:
1.122 djm 263: if ((extra = format_method_key(authctxt)) == NULL) {
264: if (authctxt->auth_method_info != NULL)
265: extra = xstrdup(authctxt->auth_method_info);
266: }
267:
1.116 markus 268: authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
1.13 markus 269: authmsg,
270: method,
1.98 djm 271: submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
1.56 markus 272: authctxt->valid ? "" : "invalid user ",
1.29 markus 273: authctxt->user,
1.114 djm 274: ssh_remote_ipaddr(ssh),
275: ssh_remote_port(ssh),
1.122 djm 276: extra != NULL ? ": " : "",
277: extra != NULL ? extra : "");
278:
279: free(extra);
1.105 djm 280: }
281:
282: void
283: auth_maxtries_exceeded(Authctxt *authctxt)
284: {
1.114 djm 285: struct ssh *ssh = active_state; /* XXX */
286:
1.110 djm 287: error("maximum authentication attempts exceeded for "
1.116 markus 288: "%s%.100s from %.200s port %d ssh2",
1.105 djm 289: authctxt->valid ? "" : "invalid user ",
290: authctxt->user,
1.114 djm 291: ssh_remote_ipaddr(ssh),
1.116 markus 292: ssh_remote_port(ssh));
1.110 djm 293: packet_disconnect("Too many authentication failures");
1.105 djm 294: /* NOTREACHED */
1.13 markus 295: }
296:
297: /*
1.17 markus 298: * Check whether root logins are disallowed.
1.13 markus 299: */
300: int
1.126 ! djm 301: auth_root_allowed(struct ssh *ssh, const char *method)
1.13 markus 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:
1.126 ! djm 313: if (auth_opts->force_command != NULL) {
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;
1.126 ! djm 861: }
! 862:
! 863: /* These functions link key/cert options to the auth framework */
! 864:
! 865: /* Log sshauthopt options locally and (optionally) for remote transmission */
! 866: void
! 867: auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
! 868: {
! 869: int do_env = options.permit_user_env && opts->nenv > 0;
! 870: int do_permitopen = opts->npermitopen > 0 &&
! 871: (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
! 872: size_t i;
! 873: char msg[1024], tbuf[32];
! 874:
! 875: snprintf(tbuf, sizeof(tbuf), "%d", opts->force_tun_device);
! 876: /* Try to keep this alphabetically sorted */
! 877: snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s",
! 878: opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
! 879: opts->force_command == NULL ? "" : " command",
! 880: do_env ? " environment" : "",
! 881: do_permitopen ? " permitopen" : "",
! 882: opts->permit_port_forwarding_flag ? " port-forwarding" : "",
! 883: opts->cert_principals == NULL ? "" : " principals",
! 884: opts->permit_pty_flag ? " pty" : "",
! 885: opts->force_tun_device == -1 ? "" : " tun=",
! 886: opts->force_tun_device == -1 ? "" : tbuf,
! 887: opts->permit_user_rc ? " user-rc" : "",
! 888: opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
! 889:
! 890: debug("%s: %s", loc, msg);
! 891: if (do_remote)
! 892: auth_debug_add("%s: %s", loc, msg);
! 893:
! 894: if (options.permit_user_env) {
! 895: for (i = 0; i < opts->nenv; i++) {
! 896: debug("%s: environment: %s", loc, opts->env[i]);
! 897: if (do_remote) {
! 898: auth_debug_add("%s: environment: %s",
! 899: loc, opts->env[i]);
! 900: }
! 901: }
! 902: }
! 903:
! 904: /* Go into a little more details for the local logs. */
! 905: if (opts->cert_principals != NULL) {
! 906: debug("%s: authorized principals: \"%s\"",
! 907: loc, opts->cert_principals);
! 908: }
! 909: if (opts->force_command != NULL)
! 910: debug("%s: forced command: \"%s\"", loc, opts->force_command);
! 911: if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0) {
! 912: for (i = 0; i < opts->npermitopen; i++) {
! 913: debug("%s: permitted open: %s",
! 914: loc, opts->permitopen[i]);
! 915: }
! 916: }
! 917: }
! 918:
! 919: /* Activate a new set of key/cert options; merging with what is there. */
! 920: int
! 921: auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
! 922: {
! 923: struct sshauthopt *old = auth_opts;
! 924: const char *emsg = NULL;
! 925:
! 926: debug("%s: setting new authentication options", __func__);
! 927: if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
! 928: error("Inconsistent authentication options: %s", emsg);
! 929: return -1;
! 930: }
! 931: return 0;
! 932: }
! 933:
! 934: /* Disable forwarding, etc for the session */
! 935: void
! 936: auth_restrict_session(struct ssh *ssh)
! 937: {
! 938: struct sshauthopt *restricted;
! 939:
! 940: debug("%s: restricting session", __func__);
! 941:
! 942: /* A blank sshauthopt defaults to permitting nothing */
! 943: restricted = sshauthopt_new();
! 944: restricted->restricted = 1;
! 945:
! 946: if (auth_activate_options(ssh, restricted) != 0)
! 947: fatal("%s: failed to restrict session", __func__);
! 948: sshauthopt_free(restricted);
! 949: }
! 950:
! 951: int
! 952: auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
! 953: struct sshauthopt *opts, int allow_cert_authority, const char *loc)
! 954: {
! 955: const char *remote_ip = ssh_remote_ipaddr(ssh);
! 956: const char *remote_host = auth_get_canonical_hostname(ssh,
! 957: options.use_dns);
! 958:
! 959: /* Consistency checks */
! 960: if (opts->cert_principals != NULL && !opts->cert_authority) {
! 961: debug("%s: principals on non-CA key", loc);
! 962: auth_debug_add("%s: principals on non-CA key", loc);
! 963: /* deny access */
! 964: return -1;
! 965: }
! 966: /* cert-authority flag isn't valid in authorized_principals files */
! 967: if (!allow_cert_authority && opts->cert_authority) {
! 968: debug("%s: cert-authority flag invalid here", loc);
! 969: auth_debug_add("%s: cert-authority flag invalid here", loc);
! 970: /* deny access */
! 971: return -1;
! 972: }
! 973:
! 974: /* Perform from= checks */
! 975: if (opts->required_from_host_keys != NULL) {
! 976: switch (match_host_and_ip(remote_host, remote_ip,
! 977: opts->required_from_host_keys )) {
! 978: case 1:
! 979: /* Host name matches. */
! 980: break;
! 981: case -1:
! 982: default:
! 983: debug("%s: invalid from criteria", loc);
! 984: auth_debug_add("%s: invalid from criteria", loc);
! 985: /* FALLTHROUGH */
! 986: case 0:
! 987: logit("%s: Authentication tried for %.100s with "
! 988: "correct key but not from a permitted "
! 989: "host (host=%.200s, ip=%.200s, required=%.200s).",
! 990: loc, pw->pw_name, remote_host, remote_ip,
! 991: opts->required_from_host_keys);
! 992: auth_debug_add("%s: Your host '%.200s' is not "
! 993: "permitted to use this key for login.",
! 994: loc, remote_host);
! 995: /* deny access */
! 996: return -1;
! 997: }
! 998: }
! 999: /* Check source-address restriction from certificate */
! 1000: if (opts->required_from_host_cert != NULL) {
! 1001: switch (addr_match_cidr_list(remote_ip,
! 1002: opts->required_from_host_cert)) {
! 1003: case 1:
! 1004: /* accepted */
! 1005: break;
! 1006: case -1:
! 1007: default:
! 1008: /* invalid */
! 1009: error("%s: Certificate source-address invalid",
! 1010: loc);
! 1011: /* FALLTHROUGH */
! 1012: case 0:
! 1013: logit("%s: Authentication tried for %.100s with valid "
! 1014: "certificate but not from a permitted source "
! 1015: "address (%.200s).", loc, pw->pw_name, remote_ip);
! 1016: auth_debug_add("%s: Your address '%.200s' is not "
! 1017: "permitted to use this certificate for login.",
! 1018: loc, remote_ip);
! 1019: return -1;
! 1020: }
! 1021: }
! 1022: /*
! 1023: *
! 1024: * XXX this is spammy. We should report remotely only for keys
! 1025: * that are successful in actual auth attempts, and not PK_OK
! 1026: * tests.
! 1027: */
! 1028: auth_log_authopts(loc, opts, 1);
! 1029:
! 1030: return 0;
1.1 markus 1031: }
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