Annotation of src/usr.bin/ssh/auth.c, Revision 1.130
1.130 ! djm 1: /* $OpenBSD: auth.c,v 1.129 2018/06/01 03:33:53 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"
1.126 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: {
1.129 djm 335: char *file, uidstr[32], ret[PATH_MAX];
1.65 djm 336: int i;
1.22 markus 337:
1.129 djm 338: snprintf(uidstr, sizeof(uidstr), "%llu",
339: (unsigned long long)pw->pw_uid);
1.59 djm 340: file = percent_expand(filename, "h", pw->pw_dir,
1.129 djm 341: "u", pw->pw_name, "U", uidstr, (char *)NULL);
1.22 markus 342:
343: /*
344: * Ensure that filename starts anchored. If not, be backward
345: * compatible and prepend the '%h/'
346: */
1.59 djm 347: if (*file == '/')
348: return (file);
349:
1.65 djm 350: i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
351: if (i < 0 || (size_t)i >= sizeof(ret))
1.59 djm 352: fatal("expand_authorized_keys: path too long");
1.102 djm 353: free(file);
1.65 djm 354: return (xstrdup(ret));
1.22 markus 355: }
1.24 markus 356:
1.87 djm 357: char *
358: authorized_principals_file(struct passwd *pw)
359: {
1.111 djm 360: if (options.authorized_principals_file == NULL)
1.87 djm 361: return NULL;
362: return expand_authorized_keys(options.authorized_principals_file, pw);
363: }
364:
1.24 markus 365: /* return ok if key exists in sysfile or userfile */
366: HostStatus
1.121 markus 367: check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
1.24 markus 368: const char *sysfile, const char *userfile)
369: {
370: char *user_hostfile;
371: struct stat st;
1.30 stevesk 372: HostStatus host_status;
1.91 djm 373: struct hostkeys *hostkeys;
374: const struct hostkey_entry *found;
1.24 markus 375:
1.91 djm 376: hostkeys = init_hostkeys();
377: load_hostkeys(hostkeys, host, sysfile);
378: if (userfile != NULL) {
1.24 markus 379: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
380: if (options.strict_modes &&
381: (stat(user_hostfile, &st) == 0) &&
382: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.31 deraadt 383: (st.st_mode & 022) != 0)) {
1.47 itojun 384: logit("Authentication refused for %.100s: "
1.24 markus 385: "bad owner or modes for %.200s",
386: pw->pw_name, user_hostfile);
1.88 djm 387: auth_debug_add("Ignored %.200s: bad ownership or modes",
388: user_hostfile);
1.24 markus 389: } else {
390: temporarily_use_uid(pw);
1.91 djm 391: load_hostkeys(hostkeys, host, user_hostfile);
1.24 markus 392: restore_uid();
393: }
1.102 djm 394: free(user_hostfile);
1.24 markus 395: }
1.91 djm 396: host_status = check_key_in_hostkeys(hostkeys, key, &found);
397: if (host_status == HOST_REVOKED)
398: error("WARNING: revoked key for %s attempted authentication",
399: found->host);
400: else if (host_status == HOST_OK)
401: debug("%s: key for %s found at %s:%ld", __func__,
402: found->host, found->file, found->line);
403: else
404: debug("%s: key for host %s not found", __func__, host);
405:
406: free_hostkeys(hostkeys);
1.24 markus 407:
408: return host_status;
409: }
410:
1.87 djm 411: static FILE *
412: auth_openfile(const char *file, struct passwd *pw, int strict_modes,
413: int log_missing, char *file_type)
1.79 dtucker 414: {
415: char line[1024];
416: struct stat st;
417: int fd;
418: FILE *f;
419:
1.81 dtucker 420: if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
1.87 djm 421: if (log_missing || errno != ENOENT)
422: debug("Could not open %s '%s': %s", file_type, file,
1.81 dtucker 423: strerror(errno));
1.79 dtucker 424: return NULL;
1.81 dtucker 425: }
1.79 dtucker 426:
427: if (fstat(fd, &st) < 0) {
428: close(fd);
429: return NULL;
430: }
431: if (!S_ISREG(st.st_mode)) {
1.87 djm 432: logit("User %s %s %s is not a regular file",
433: pw->pw_name, file_type, file);
1.79 dtucker 434: close(fd);
435: return NULL;
436: }
437: unset_nonblock(fd);
438: if ((f = fdopen(fd, "r")) == NULL) {
439: close(fd);
440: return NULL;
441: }
1.90 djm 442: if (strict_modes &&
1.123 djm 443: safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
1.79 dtucker 444: fclose(f);
445: logit("Authentication refused: %s", line);
1.88 djm 446: auth_debug_add("Ignored %s: %s", file_type, line);
1.79 dtucker 447: return NULL;
448: }
449:
450: return f;
1.87 djm 451: }
452:
453:
454: FILE *
455: auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
456: {
457: return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
458: }
459:
460: FILE *
461: auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
462: {
463: return auth_openfile(file, pw, strict_modes, 0,
464: "authorized principals");
1.37 provos 465: }
466:
467: struct passwd *
468: getpwnamallow(const char *user)
469: {
1.114 djm 470: struct ssh *ssh = active_state; /* XXX */
1.38 provos 471: extern login_cap_t *lc;
472: auth_session_t *as;
1.37 provos 473: struct passwd *pw;
1.96 dtucker 474: struct connection_info *ci = get_connection_info(1, options.use_dns);
1.71 dtucker 475:
1.96 dtucker 476: ci->user = user;
477: parse_server_match_config(&options, ci);
1.120 djm 478: log_change_level(options.log_level);
1.124 djm 479: process_permitopen(ssh, &options);
1.37 provos 480:
481: pw = getpwnam(user);
1.45 stevesk 482: if (pw == NULL) {
1.114 djm 483: logit("Invalid user %.100s from %.100s port %d",
484: user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
1.45 stevesk 485: return (NULL);
486: }
487: if (!allowed_user(pw))
1.38 provos 488: return (NULL);
489: if ((lc = login_getclass(pw->pw_class)) == NULL) {
490: debug("unable to get login class: %s", user);
491: return (NULL);
492: }
493: if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
1.43 millert 494: auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
1.38 provos 495: debug("Approval failure for %s", user);
1.37 provos 496: pw = NULL;
1.38 provos 497: }
498: if (as != NULL)
499: auth_close(as);
1.41 markus 500: if (pw != NULL)
501: return (pwcopy(pw));
502: return (NULL);
1.85 djm 503: }
504:
505: /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
506: int
1.121 markus 507: auth_key_is_revoked(struct sshkey *key)
1.85 djm 508: {
1.107 djm 509: char *fp = NULL;
510: int r;
1.85 djm 511:
512: if (options.revoked_keys_file == NULL)
513: return 0;
1.108 djm 514: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
515: SSH_FP_DEFAULT)) == NULL) {
1.107 djm 516: r = SSH_ERR_ALLOC_FAIL;
517: error("%s: fingerprint key: %s", __func__, ssh_err(r));
518: goto out;
519: }
520:
521: r = sshkey_check_revoked(key, options.revoked_keys_file);
522: switch (r) {
1.100 djm 523: case 0:
1.107 djm 524: break; /* not revoked */
525: case SSH_ERR_KEY_REVOKED:
526: error("Authentication key %s %s revoked by file %s",
527: sshkey_type(key), fp, options.revoked_keys_file);
528: goto out;
1.100 djm 529: default:
1.107 djm 530: error("Error checking authentication key %s %s in "
531: "revoked keys file %s: %s", sshkey_type(key), fp,
532: options.revoked_keys_file, ssh_err(r));
533: goto out;
1.100 djm 534: }
1.107 djm 535:
536: /* Success */
537: r = 0;
538:
539: out:
540: free(fp);
541: return r == 0 ? 0 : 1;
1.42 markus 542: }
543:
544: void
545: auth_debug_add(const char *fmt,...)
546: {
547: char buf[1024];
548: va_list args;
549:
550: if (!auth_debug_init)
551: return;
552:
553: va_start(args, fmt);
554: vsnprintf(buf, sizeof(buf), fmt, args);
555: va_end(args);
556: buffer_put_cstring(&auth_debug, buf);
557: }
558:
559: void
560: auth_debug_send(void)
561: {
562: char *msg;
563:
564: if (!auth_debug_init)
565: return;
566: while (buffer_len(&auth_debug)) {
567: msg = buffer_get_string(&auth_debug, NULL);
568: packet_send_debug("%s", msg);
1.102 djm 569: free(msg);
1.42 markus 570: }
571: }
572:
573: void
574: auth_debug_reset(void)
575: {
576: if (auth_debug_init)
577: buffer_clear(&auth_debug);
578: else {
579: buffer_init(&auth_debug);
580: auth_debug_init = 1;
581: }
1.49 markus 582: }
583:
584: struct passwd *
585: fakepw(void)
586: {
587: static struct passwd fake;
588:
589: memset(&fake, 0, sizeof(fake));
590: fake.pw_name = "NOUSER";
591: fake.pw_passwd =
1.51 djm 592: "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
1.49 markus 593: fake.pw_gecos = "NOUSER";
1.53 deraadt 594: fake.pw_uid = (uid_t)-1;
595: fake.pw_gid = (gid_t)-1;
1.49 markus 596: fake.pw_class = "";
597: fake.pw_dir = "/nonexist";
598: fake.pw_shell = "/nonexist";
599:
600: return (&fake);
1.114 djm 601: }
602:
603: /*
604: * Returns the remote DNS hostname as a string. The returned string must not
605: * be freed. NB. this will usually trigger a DNS query the first time it is
606: * called.
607: * This function does additional checks on the hostname to mitigate some
608: * attacks on legacy rhosts-style authentication.
609: * XXX is RhostsRSAAuthentication vulnerable to these?
610: * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
611: */
612:
613: static char *
614: remote_hostname(struct ssh *ssh)
615: {
616: struct sockaddr_storage from;
617: socklen_t fromlen;
618: struct addrinfo hints, *ai, *aitop;
619: char name[NI_MAXHOST], ntop2[NI_MAXHOST];
620: const char *ntop = ssh_remote_ipaddr(ssh);
621:
622: /* Get IP address of client. */
623: fromlen = sizeof(from);
624: memset(&from, 0, sizeof(from));
625: if (getpeername(ssh_packet_get_connection_in(ssh),
626: (struct sockaddr *)&from, &fromlen) < 0) {
627: debug("getpeername failed: %.100s", strerror(errno));
628: return strdup(ntop);
629: }
630:
631: debug3("Trying to reverse map address %.100s.", ntop);
632: /* Map the IP address to a host name. */
633: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
634: NULL, 0, NI_NAMEREQD) != 0) {
635: /* Host name not found. Use ip address. */
636: return strdup(ntop);
637: }
638:
639: /*
640: * if reverse lookup result looks like a numeric hostname,
641: * someone is trying to trick us by PTR record like following:
642: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
643: */
644: memset(&hints, 0, sizeof(hints));
645: hints.ai_socktype = SOCK_DGRAM; /*dummy*/
646: hints.ai_flags = AI_NUMERICHOST;
647: if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
648: logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
649: name, ntop);
650: freeaddrinfo(ai);
651: return strdup(ntop);
652: }
653:
654: /* Names are stored in lowercase. */
655: lowercase(name);
656:
657: /*
658: * Map it back to an IP address and check that the given
659: * address actually is an address of this host. This is
660: * necessary because anyone with access to a name server can
661: * define arbitrary names for an IP address. Mapping from
662: * name to IP address can be trusted better (but can still be
663: * fooled if the intruder has access to the name server of
664: * the domain).
665: */
666: memset(&hints, 0, sizeof(hints));
667: hints.ai_family = from.ss_family;
668: hints.ai_socktype = SOCK_STREAM;
669: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
670: logit("reverse mapping checking getaddrinfo for %.700s "
1.115 dtucker 671: "[%s] failed.", name, ntop);
1.114 djm 672: return strdup(ntop);
673: }
674: /* Look for the address from the list of addresses. */
675: for (ai = aitop; ai; ai = ai->ai_next) {
676: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
677: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
678: (strcmp(ntop, ntop2) == 0))
679: break;
680: }
681: freeaddrinfo(aitop);
682: /* If we reached the end of the list, the address was not there. */
683: if (ai == NULL) {
684: /* Address not found for the host name. */
685: logit("Address %.100s maps to %.600s, but this does not "
1.115 dtucker 686: "map back to the address.", ntop, name);
1.114 djm 687: return strdup(ntop);
688: }
689: return strdup(name);
690: }
691:
692: /*
693: * Return the canonical name of the host in the other side of the current
694: * connection. The host name is cached, so it is efficient to call this
695: * several times.
696: */
697:
698: const char *
699: auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
700: {
701: static char *dnsname;
702:
703: if (!use_dns)
704: return ssh_remote_ipaddr(ssh);
705: else if (dnsname != NULL)
706: return dnsname;
707: else {
708: dnsname = remote_hostname(ssh);
709: return dnsname;
710: }
1.125 markus 711: }
712:
713: /*
714: * Runs command in a subprocess wuth a minimal environment.
715: * Returns pid on success, 0 on failure.
716: * The child stdout and stderr maybe captured, left attached or sent to
717: * /dev/null depending on the contents of flags.
718: * "tag" is prepended to log messages.
719: * NB. "command" is only used for logging; the actual command executed is
720: * av[0].
721: */
722: pid_t
723: subprocess(const char *tag, struct passwd *pw, const char *command,
724: int ac, char **av, FILE **child, u_int flags)
725: {
726: FILE *f = NULL;
727: struct stat st;
728: int fd, devnull, p[2], i;
729: pid_t pid;
730: char *cp, errmsg[512];
731: u_int envsize;
732: char **child_env;
733:
734: if (child != NULL)
735: *child = NULL;
736:
737: debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
738: tag, command, pw->pw_name, flags);
739:
740: /* Check consistency */
741: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
742: (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
743: error("%s: inconsistent flags", __func__);
744: return 0;
745: }
746: if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
747: error("%s: inconsistent flags/output", __func__);
748: return 0;
749: }
750:
751: /*
752: * If executing an explicit binary, then verify the it exists
753: * and appears safe-ish to execute
754: */
755: if (*av[0] != '/') {
756: error("%s path is not absolute", tag);
757: return 0;
758: }
759: temporarily_use_uid(pw);
760: if (stat(av[0], &st) < 0) {
761: error("Could not stat %s \"%s\": %s", tag,
762: av[0], strerror(errno));
763: restore_uid();
764: return 0;
765: }
766: if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
767: error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
768: restore_uid();
769: return 0;
770: }
771: /* Prepare to keep the child's stdout if requested */
772: if (pipe(p) != 0) {
773: error("%s: pipe: %s", tag, strerror(errno));
774: restore_uid();
775: return 0;
776: }
777: restore_uid();
778:
779: switch ((pid = fork())) {
780: case -1: /* error */
781: error("%s: fork: %s", tag, strerror(errno));
782: close(p[0]);
783: close(p[1]);
784: return 0;
785: case 0: /* child */
786: /* Prepare a minimal environment for the child. */
787: envsize = 5;
788: child_env = xcalloc(sizeof(*child_env), envsize);
789: child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
790: child_set_env(&child_env, &envsize, "USER", pw->pw_name);
791: child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
792: child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
793: if ((cp = getenv("LANG")) != NULL)
794: child_set_env(&child_env, &envsize, "LANG", cp);
795:
796: for (i = 0; i < NSIG; i++)
797: signal(i, SIG_DFL);
798:
799: if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
800: error("%s: open %s: %s", tag, _PATH_DEVNULL,
801: strerror(errno));
802: _exit(1);
803: }
804: if (dup2(devnull, STDIN_FILENO) == -1) {
805: error("%s: dup2: %s", tag, strerror(errno));
806: _exit(1);
807: }
808:
809: /* Set up stdout as requested; leave stderr in place for now. */
810: fd = -1;
811: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
812: fd = p[1];
813: else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
814: fd = devnull;
815: if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
816: error("%s: dup2: %s", tag, strerror(errno));
817: _exit(1);
818: }
819: closefrom(STDERR_FILENO + 1);
820:
821: /* Don't use permanently_set_uid() here to avoid fatal() */
822: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
823: error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
824: strerror(errno));
825: _exit(1);
826: }
827: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
828: error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
829: strerror(errno));
830: _exit(1);
831: }
832: /* stdin is pointed to /dev/null at this point */
833: if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
834: dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
835: error("%s: dup2: %s", tag, strerror(errno));
836: _exit(1);
837: }
838:
839: execve(av[0], av, child_env);
840: error("%s exec \"%s\": %s", tag, command, strerror(errno));
841: _exit(127);
842: default: /* parent */
843: break;
844: }
845:
846: close(p[1]);
847: if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
848: close(p[0]);
849: else if ((f = fdopen(p[0], "r")) == NULL) {
850: error("%s: fdopen: %s", tag, strerror(errno));
851: close(p[0]);
852: /* Don't leave zombie child */
853: kill(pid, SIGTERM);
854: while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
855: ;
856: return 0;
857: }
858: /* Success */
859: debug3("%s: %s pid %ld", __func__, tag, (long)pid);
860: if (child != NULL)
861: *child = f;
862: return pid;
1.126 djm 863: }
864:
865: /* These functions link key/cert options to the auth framework */
866:
867: /* Log sshauthopt options locally and (optionally) for remote transmission */
868: void
869: auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
870: {
871: int do_env = options.permit_user_env && opts->nenv > 0;
872: int do_permitopen = opts->npermitopen > 0 &&
873: (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
1.130 ! djm 874: int do_permitlisten = opts->npermitlisten > 0 &&
! 875: (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
1.126 djm 876: size_t i;
1.127 djm 877: char msg[1024], buf[64];
1.126 djm 878:
1.127 djm 879: snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
1.126 djm 880: /* Try to keep this alphabetically sorted */
1.130 ! djm 881: snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s",
1.126 djm 882: opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
883: opts->force_command == NULL ? "" : " command",
884: do_env ? " environment" : "",
1.127 djm 885: opts->valid_before == 0 ? "" : "expires",
1.126 djm 886: do_permitopen ? " permitopen" : "",
1.130 ! djm 887: do_permitlisten ? " permitlisten" : "",
1.126 djm 888: opts->permit_port_forwarding_flag ? " port-forwarding" : "",
889: opts->cert_principals == NULL ? "" : " principals",
890: opts->permit_pty_flag ? " pty" : "",
891: opts->force_tun_device == -1 ? "" : " tun=",
1.127 djm 892: opts->force_tun_device == -1 ? "" : buf,
1.126 djm 893: opts->permit_user_rc ? " user-rc" : "",
894: opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
895:
896: debug("%s: %s", loc, msg);
897: if (do_remote)
898: auth_debug_add("%s: %s", loc, msg);
899:
900: if (options.permit_user_env) {
901: for (i = 0; i < opts->nenv; i++) {
902: debug("%s: environment: %s", loc, opts->env[i]);
903: if (do_remote) {
904: auth_debug_add("%s: environment: %s",
905: loc, opts->env[i]);
906: }
907: }
908: }
909:
910: /* Go into a little more details for the local logs. */
1.127 djm 911: if (opts->valid_before != 0) {
912: format_absolute_time(opts->valid_before, buf, sizeof(buf));
913: debug("%s: expires at %s", loc, buf);
914: }
1.126 djm 915: if (opts->cert_principals != NULL) {
916: debug("%s: authorized principals: \"%s\"",
917: loc, opts->cert_principals);
918: }
919: if (opts->force_command != NULL)
920: debug("%s: forced command: \"%s\"", loc, opts->force_command);
1.130 ! djm 921: if (do_permitopen) {
1.126 djm 922: for (i = 0; i < opts->npermitopen; i++) {
923: debug("%s: permitted open: %s",
924: loc, opts->permitopen[i]);
1.130 ! djm 925: }
! 926: }
! 927: if (do_permitlisten) {
! 928: for (i = 0; i < opts->npermitlisten; i++) {
! 929: debug("%s: permitted listen: %s",
! 930: loc, opts->permitlisten[i]);
1.126 djm 931: }
932: }
933: }
934:
935: /* Activate a new set of key/cert options; merging with what is there. */
936: int
937: auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
938: {
939: struct sshauthopt *old = auth_opts;
940: const char *emsg = NULL;
941:
942: debug("%s: setting new authentication options", __func__);
943: if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
944: error("Inconsistent authentication options: %s", emsg);
945: return -1;
946: }
947: return 0;
948: }
949:
950: /* Disable forwarding, etc for the session */
951: void
952: auth_restrict_session(struct ssh *ssh)
953: {
954: struct sshauthopt *restricted;
955:
956: debug("%s: restricting session", __func__);
957:
958: /* A blank sshauthopt defaults to permitting nothing */
959: restricted = sshauthopt_new();
1.128 djm 960: restricted->permit_pty_flag = 1;
1.126 djm 961: restricted->restricted = 1;
962:
963: if (auth_activate_options(ssh, restricted) != 0)
964: fatal("%s: failed to restrict session", __func__);
965: sshauthopt_free(restricted);
966: }
967:
968: int
969: auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
970: struct sshauthopt *opts, int allow_cert_authority, const char *loc)
971: {
972: const char *remote_ip = ssh_remote_ipaddr(ssh);
973: const char *remote_host = auth_get_canonical_hostname(ssh,
974: options.use_dns);
1.127 djm 975: time_t now = time(NULL);
976: char buf[64];
1.126 djm 977:
1.127 djm 978: /*
979: * Check keys/principals file expiry time.
980: * NB. validity interval in certificate is handled elsewhere.
981: */
982: if (opts->valid_before && now > 0 &&
983: opts->valid_before < (uint64_t)now) {
984: format_absolute_time(opts->valid_before, buf, sizeof(buf));
985: debug("%s: entry expired at %s", loc, buf);
986: auth_debug_add("%s: entry expired at %s", loc, buf);
987: return -1;
988: }
1.126 djm 989: /* Consistency checks */
990: if (opts->cert_principals != NULL && !opts->cert_authority) {
991: debug("%s: principals on non-CA key", loc);
992: auth_debug_add("%s: principals on non-CA key", loc);
993: /* deny access */
994: return -1;
995: }
996: /* cert-authority flag isn't valid in authorized_principals files */
997: if (!allow_cert_authority && opts->cert_authority) {
998: debug("%s: cert-authority flag invalid here", loc);
999: auth_debug_add("%s: cert-authority flag invalid here", loc);
1000: /* deny access */
1001: return -1;
1002: }
1003:
1004: /* Perform from= checks */
1005: if (opts->required_from_host_keys != NULL) {
1006: switch (match_host_and_ip(remote_host, remote_ip,
1007: opts->required_from_host_keys )) {
1008: case 1:
1009: /* Host name matches. */
1010: break;
1011: case -1:
1012: default:
1013: debug("%s: invalid from criteria", loc);
1014: auth_debug_add("%s: invalid from criteria", loc);
1015: /* FALLTHROUGH */
1016: case 0:
1017: logit("%s: Authentication tried for %.100s with "
1018: "correct key but not from a permitted "
1019: "host (host=%.200s, ip=%.200s, required=%.200s).",
1020: loc, pw->pw_name, remote_host, remote_ip,
1021: opts->required_from_host_keys);
1022: auth_debug_add("%s: Your host '%.200s' is not "
1023: "permitted to use this key for login.",
1024: loc, remote_host);
1025: /* deny access */
1026: return -1;
1027: }
1028: }
1029: /* Check source-address restriction from certificate */
1030: if (opts->required_from_host_cert != NULL) {
1031: switch (addr_match_cidr_list(remote_ip,
1032: opts->required_from_host_cert)) {
1033: case 1:
1034: /* accepted */
1035: break;
1036: case -1:
1037: default:
1038: /* invalid */
1039: error("%s: Certificate source-address invalid",
1040: loc);
1041: /* FALLTHROUGH */
1042: case 0:
1043: logit("%s: Authentication tried for %.100s with valid "
1044: "certificate but not from a permitted source "
1045: "address (%.200s).", loc, pw->pw_name, remote_ip);
1046: auth_debug_add("%s: Your address '%.200s' is not "
1047: "permitted to use this certificate for login.",
1048: loc, remote_ip);
1049: return -1;
1050: }
1051: }
1052: /*
1053: *
1054: * XXX this is spammy. We should report remotely only for keys
1055: * that are successful in actual auth attempts, and not PK_OK
1056: * tests.
1057: */
1058: auth_log_authopts(loc, opts, 1);
1059:
1060: return 0;
1.1 markus 1061: }
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