1 /* $OpenBSD: auth2-pubkey.c,v 1.119 2023/07/27 22:25:17 djm Exp $ */
2 /*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 * Copyright (c) 2010 Damien Miller. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 #include "includes.h"
28
29 #include <sys/types.h>
30
31 #include <stdlib.h>
32 #include <errno.h>
33 #ifdef HAVE_PATHS_H
34 # include <paths.h>
35 #endif
36 #include <pwd.h>
37 #include <signal.h>
38 #include <stdio.h>
39 #include <stdarg.h>
40 #include <string.h>
41 #include <time.h>
42 #include <unistd.h>
43 #include <limits.h>
44
45 #include "xmalloc.h"
46 #include "ssh.h"
47 #include "ssh2.h"
48 #include "packet.h"
49 #include "kex.h"
50 #include "sshbuf.h"
51 #include "log.h"
52 #include "misc.h"
53 #include "servconf.h"
54 #include "compat.h"
55 #include "sshkey.h"
56 #include "hostfile.h"
57 #include "auth.h"
58 #include "pathnames.h"
59 #include "uidswap.h"
60 #include "auth-options.h"
61 #include "canohost.h"
62 #ifdef GSSAPI
63 #include "ssh-gss.h"
64 #endif
65 #include "monitor_wrap.h"
66 #include "authfile.h"
67 #include "match.h"
68 #include "ssherr.h"
69 #include "channels.h" /* XXX for session.h */
70 #include "session.h" /* XXX for child_set_env(); refactor? */
71 #include "sk-api.h"
72
73 /* import */
74 extern ServerOptions options;
75
76 static char *
format_key(const struct sshkey * key)77 format_key(const struct sshkey *key)
78 {
79 char *ret, *fp = sshkey_fingerprint(key,
80 options.fingerprint_hash, SSH_FP_DEFAULT);
81
82 xasprintf(&ret, "%s %s", sshkey_type(key), fp);
83 free(fp);
84 return ret;
85 }
86
87 static int
userauth_pubkey(struct ssh * ssh,const char * method)88 userauth_pubkey(struct ssh *ssh, const char *method)
89 {
90 Authctxt *authctxt = ssh->authctxt;
91 struct passwd *pw = authctxt->pw;
92 struct sshbuf *b = NULL;
93 struct sshkey *key = NULL, *hostkey = NULL;
94 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
95 u_char *pkblob = NULL, *sig = NULL, have_sig;
96 size_t blen, slen;
97 int hostbound, r, pktype;
98 int req_presence = 0, req_verify = 0, authenticated = 0;
99 struct sshauthopt *authopts = NULL;
100 struct sshkey_sig_details *sig_details = NULL;
101
102 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0;
103
104 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
105 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
106 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
107 fatal_fr(r, "parse %s packet", method);
108
109 /* hostbound auth includes the hostkey offered at initial KEX */
110 if (hostbound) {
111 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 ||
112 (r = sshkey_fromb(b, &hostkey)) != 0)
113 fatal_fr(r, "parse %s hostkey", method);
114 if (ssh->kex->initial_hostkey == NULL)
115 fatal_f("internal error: initial hostkey not recorded");
116 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey))
117 fatal_f("%s packet contained wrong host key", method);
118 sshbuf_free(b);
119 b = NULL;
120 }
121
122 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
123 char *keystring;
124 struct sshbuf *pkbuf;
125
126 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
127 fatal_f("sshbuf_from failed");
128 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
129 fatal_f("sshbuf_dtob64 failed");
130 debug2_f("%s user %s %s public key %s %s",
131 authctxt->valid ? "valid" : "invalid", authctxt->user,
132 have_sig ? "attempting" : "querying", pkalg, keystring);
133 sshbuf_free(pkbuf);
134 free(keystring);
135 }
136
137 pktype = sshkey_type_from_name(pkalg);
138 if (pktype == KEY_UNSPEC) {
139 /* this is perfectly legal */
140 verbose_f("unsupported public key algorithm: %s", pkalg);
141 goto done;
142 }
143 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
144 error_fr(r, "parse key");
145 goto done;
146 }
147 if (key == NULL) {
148 error_f("cannot decode key: %s", pkalg);
149 goto done;
150 }
151 if (key->type != pktype) {
152 error_f("type mismatch for decoded key "
153 "(received %d, expected %d)", key->type, pktype);
154 goto done;
155 }
156 if (auth2_key_already_used(authctxt, key)) {
157 logit("refusing previously-used %s key", sshkey_type(key));
158 goto done;
159 }
160 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) {
161 logit_f("signature algorithm %s not in "
162 "PubkeyAcceptedAlgorithms", pkalg);
163 goto done;
164 }
165 if ((r = sshkey_check_cert_sigtype(key,
166 options.ca_sign_algorithms)) != 0) {
167 logit_fr(r, "certificate signature algorithm %s",
168 (key->cert == NULL || key->cert->signature_type == NULL) ?
169 "(null)" : key->cert->signature_type);
170 goto done;
171 }
172 if ((r = sshkey_check_rsa_length(key,
173 options.required_rsa_size)) != 0) {
174 logit_r(r, "refusing %s key", sshkey_type(key));
175 goto done;
176 }
177 key_s = format_key(key);
178 if (sshkey_is_cert(key))
179 ca_s = format_key(key->cert->signature_key);
180
181 if (have_sig) {
182 debug3_f("%s have %s signature for %s%s%s",
183 method, pkalg, key_s,
184 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
185 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
186 (r = sshpkt_get_end(ssh)) != 0)
187 fatal_fr(r, "parse signature packet");
188 if ((b = sshbuf_new()) == NULL)
189 fatal_f("sshbuf_new failed");
190 if (ssh->compat & SSH_OLD_SESSIONID) {
191 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
192 fatal_fr(r, "put old session id");
193 } else {
194 if ((r = sshbuf_put_stringb(b,
195 ssh->kex->session_id)) != 0)
196 fatal_fr(r, "put session id");
197 }
198 if (!authctxt->valid || authctxt->user == NULL) {
199 debug2_f("disabled because of invalid user");
200 goto done;
201 }
202 /* reconstruct packet */
203 xasprintf(&userstyle, "%s%s%s", authctxt->user,
204 authctxt->style ? ":" : "",
205 authctxt->style ? authctxt->style : "");
206 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
207 (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
208 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
209 (r = sshbuf_put_cstring(b, method)) != 0 ||
210 (r = sshbuf_put_u8(b, have_sig)) != 0 ||
211 (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
212 (r = sshbuf_put_string(b, pkblob, blen)) != 0)
213 fatal_fr(r, "reconstruct %s packet", method);
214 if (hostbound &&
215 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0)
216 fatal_fr(r, "reconstruct %s packet", method);
217 #ifdef DEBUG_PK
218 sshbuf_dump(b, stderr);
219 #endif
220 /* test for correct signature */
221 authenticated = 0;
222 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
223 PRIVSEP(sshkey_verify(key, sig, slen,
224 sshbuf_ptr(b), sshbuf_len(b),
225 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
226 ssh->compat, &sig_details)) == 0) {
227 authenticated = 1;
228 }
229 if (authenticated == 1 && sig_details != NULL) {
230 auth2_record_info(authctxt, "signature count = %u",
231 sig_details->sk_counter);
232 debug_f("sk_counter = %u, sk_flags = 0x%02x",
233 sig_details->sk_counter, sig_details->sk_flags);
234 req_presence = (options.pubkey_auth_options &
235 PUBKEYAUTH_TOUCH_REQUIRED) ||
236 !authopts->no_require_user_presence;
237 if (req_presence && (sig_details->sk_flags &
238 SSH_SK_USER_PRESENCE_REQD) == 0) {
239 error("public key %s signature for %s%s from "
240 "%.128s port %d rejected: user presence "
241 "(authenticator touch) requirement "
242 "not met ", key_s,
243 authctxt->valid ? "" : "invalid user ",
244 authctxt->user, ssh_remote_ipaddr(ssh),
245 ssh_remote_port(ssh));
246 authenticated = 0;
247 goto done;
248 }
249 req_verify = (options.pubkey_auth_options &
250 PUBKEYAUTH_VERIFY_REQUIRED) ||
251 authopts->require_verify;
252 if (req_verify && (sig_details->sk_flags &
253 SSH_SK_USER_VERIFICATION_REQD) == 0) {
254 error("public key %s signature for %s%s from "
255 "%.128s port %d rejected: user "
256 "verification requirement not met ", key_s,
257 authctxt->valid ? "" : "invalid user ",
258 authctxt->user, ssh_remote_ipaddr(ssh),
259 ssh_remote_port(ssh));
260 authenticated = 0;
261 goto done;
262 }
263 }
264 auth2_record_key(authctxt, authenticated, key);
265 } else {
266 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s,
267 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
268
269 if ((r = sshpkt_get_end(ssh)) != 0)
270 fatal_fr(r, "parse packet");
271
272 if (!authctxt->valid || authctxt->user == NULL) {
273 debug2_f("disabled because of invalid user");
274 goto done;
275 }
276 /* XXX fake reply and always send PK_OK ? */
277 /*
278 * XXX this allows testing whether a user is allowed
279 * to login: if you happen to have a valid pubkey this
280 * message is sent. the message is NEVER sent at all
281 * if a user is not allowed to login. is this an
282 * issue? -markus
283 */
284 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
285 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
286 != 0 ||
287 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
288 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
289 (r = sshpkt_send(ssh)) != 0 ||
290 (r = ssh_packet_write_wait(ssh)) != 0)
291 fatal_fr(r, "send packet");
292 authctxt->postponed = 1;
293 }
294 }
295 done:
296 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
297 debug_f("key options inconsistent with existing");
298 authenticated = 0;
299 }
300 debug2_f("authenticated %d pkalg %s", authenticated, pkalg);
301
302 sshbuf_free(b);
303 sshauthopt_free(authopts);
304 sshkey_free(key);
305 sshkey_free(hostkey);
306 free(userstyle);
307 free(pkalg);
308 free(pkblob);
309 free(key_s);
310 free(ca_s);
311 free(sig);
312 sshkey_sig_details_free(sig_details);
313 return authenticated;
314 }
315
316 static int
match_principals_file(struct passwd * pw,char * file,struct sshkey_cert * cert,struct sshauthopt ** authoptsp)317 match_principals_file(struct passwd *pw, char *file,
318 struct sshkey_cert *cert, struct sshauthopt **authoptsp)
319 {
320 FILE *f;
321 int success;
322
323 if (authoptsp != NULL)
324 *authoptsp = NULL;
325
326 temporarily_use_uid(pw);
327 debug("trying authorized principals file %s", file);
328 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
329 restore_uid();
330 return 0;
331 }
332 success = auth_process_principals(f, file, cert, authoptsp);
333 fclose(f);
334 restore_uid();
335 return success;
336 }
337
338 /*
339 * Checks whether principal is allowed in output of command.
340 * returns 1 if the principal is allowed or 0 otherwise.
341 */
342 static int
match_principals_command(struct passwd * user_pw,const struct sshkey * key,const char * conn_id,const char * rdomain,struct sshauthopt ** authoptsp)343 match_principals_command(struct passwd *user_pw, const struct sshkey *key,
344 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
345 {
346 struct passwd *runas_pw = NULL;
347 const struct sshkey_cert *cert = key->cert;
348 FILE *f = NULL;
349 int r, ok, found_principal = 0;
350 int i, ac = 0, uid_swapped = 0;
351 pid_t pid;
352 char *tmp, *username = NULL, *command = NULL, **av = NULL;
353 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
354 char serial_s[32], uidstr[32];
355 void (*osigchld)(int);
356
357 if (authoptsp != NULL)
358 *authoptsp = NULL;
359 if (options.authorized_principals_command == NULL)
360 return 0;
361 if (options.authorized_principals_command_user == NULL) {
362 error("No user for AuthorizedPrincipalsCommand specified, "
363 "skipping");
364 return 0;
365 }
366
367 /*
368 * NB. all returns later this function should go via "out" to
369 * ensure the original SIGCHLD handler is restored properly.
370 */
371 osigchld = ssh_signal(SIGCHLD, SIG_DFL);
372
373 /* Prepare and verify the user for the command */
374 username = percent_expand(options.authorized_principals_command_user,
375 "u", user_pw->pw_name, (char *)NULL);
376 runas_pw = getpwnam(username);
377 if (runas_pw == NULL) {
378 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
379 username, strerror(errno));
380 goto out;
381 }
382
383 /* Turn the command into an argument vector */
384 if (argv_split(options.authorized_principals_command,
385 &ac, &av, 0) != 0) {
386 error("AuthorizedPrincipalsCommand \"%s\" contains "
387 "invalid quotes", options.authorized_principals_command);
388 goto out;
389 }
390 if (ac == 0) {
391 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
392 options.authorized_principals_command);
393 goto out;
394 }
395 if ((ca_fp = sshkey_fingerprint(cert->signature_key,
396 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
397 error_f("sshkey_fingerprint failed");
398 goto out;
399 }
400 if ((key_fp = sshkey_fingerprint(key,
401 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
402 error_f("sshkey_fingerprint failed");
403 goto out;
404 }
405 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
406 error_fr(r, "sshkey_to_base64 failed");
407 goto out;
408 }
409 if ((r = sshkey_to_base64(key, &keytext)) != 0) {
410 error_fr(r, "sshkey_to_base64 failed");
411 goto out;
412 }
413 snprintf(serial_s, sizeof(serial_s), "%llu",
414 (unsigned long long)cert->serial);
415 snprintf(uidstr, sizeof(uidstr), "%llu",
416 (unsigned long long)user_pw->pw_uid);
417 for (i = 1; i < ac; i++) {
418 tmp = percent_expand(av[i],
419 "C", conn_id,
420 "D", rdomain,
421 "U", uidstr,
422 "u", user_pw->pw_name,
423 "h", user_pw->pw_dir,
424 "t", sshkey_ssh_name(key),
425 "T", sshkey_ssh_name(cert->signature_key),
426 "f", key_fp,
427 "F", ca_fp,
428 "k", keytext,
429 "K", catext,
430 "i", cert->key_id,
431 "s", serial_s,
432 (char *)NULL);
433 if (tmp == NULL)
434 fatal_f("percent_expand failed");
435 free(av[i]);
436 av[i] = tmp;
437 }
438 /* Prepare a printable command for logs, etc. */
439 command = argv_assemble(ac, av);
440
441 if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
442 ac, av, &f,
443 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
444 runas_pw, temporarily_use_uid, restore_uid)) == 0)
445 goto out;
446
447 uid_swapped = 1;
448 temporarily_use_uid(runas_pw);
449
450 ok = auth_process_principals(f, "(command)", cert, authoptsp);
451
452 fclose(f);
453 f = NULL;
454
455 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
456 goto out;
457
458 /* Read completed successfully */
459 found_principal = ok;
460 out:
461 if (f != NULL)
462 fclose(f);
463 ssh_signal(SIGCHLD, osigchld);
464 for (i = 0; i < ac; i++)
465 free(av[i]);
466 free(av);
467 if (uid_swapped)
468 restore_uid();
469 free(command);
470 free(username);
471 free(ca_fp);
472 free(key_fp);
473 free(catext);
474 free(keytext);
475 return found_principal;
476 }
477
478 /* Authenticate a certificate key against TrustedUserCAKeys */
479 static int
user_cert_trusted_ca(struct passwd * pw,struct sshkey * key,const char * remote_ip,const char * remote_host,const char * conn_id,const char * rdomain,struct sshauthopt ** authoptsp)480 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key,
481 const char *remote_ip, const char *remote_host,
482 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
483 {
484 char *ca_fp, *principals_file = NULL;
485 const char *reason;
486 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
487 struct sshauthopt *final_opts = NULL;
488 int r, ret = 0, found_principal = 0, use_authorized_principals;
489
490 if (authoptsp != NULL)
491 *authoptsp = NULL;
492
493 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
494 return 0;
495
496 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
497 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
498 return 0;
499
500 if ((r = sshkey_in_file(key->cert->signature_key,
501 options.trusted_user_ca_keys, 1, 0)) != 0) {
502 debug2_fr(r, "CA %s %s is not listed in %s",
503 sshkey_type(key->cert->signature_key), ca_fp,
504 options.trusted_user_ca_keys);
505 goto out;
506 }
507 /*
508 * If AuthorizedPrincipals is in use, then compare the certificate
509 * principals against the names in that file rather than matching
510 * against the username.
511 */
512 if ((principals_file = authorized_principals_file(pw)) != NULL) {
513 if (match_principals_file(pw, principals_file,
514 key->cert, &principals_opts))
515 found_principal = 1;
516 }
517 /* Try querying command if specified */
518 if (!found_principal && match_principals_command(pw, key,
519 conn_id, rdomain, &principals_opts))
520 found_principal = 1;
521 /* If principals file or command is specified, then require a match */
522 use_authorized_principals = principals_file != NULL ||
523 options.authorized_principals_command != NULL;
524 if (!found_principal && use_authorized_principals) {
525 reason = "Certificate does not contain an authorized principal";
526 goto fail_reason;
527 }
528 if (use_authorized_principals && principals_opts == NULL)
529 fatal_f("internal error: missing principals_opts");
530 if (sshkey_cert_check_authority_now(key, 0, 1, 0,
531 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
532 goto fail_reason;
533
534 /* Check authority from options in key and from principals file/cmd */
535 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
536 reason = "Invalid certificate options";
537 goto fail_reason;
538 }
539 if (auth_authorise_keyopts(pw, cert_opts, 0,
540 remote_ip, remote_host, "cert") != 0) {
541 reason = "Refused by certificate options";
542 goto fail_reason;
543 }
544 if (principals_opts == NULL) {
545 final_opts = cert_opts;
546 cert_opts = NULL;
547 } else {
548 if (auth_authorise_keyopts(pw, principals_opts, 0,
549 remote_ip, remote_host, "principals") != 0) {
550 reason = "Refused by certificate principals options";
551 goto fail_reason;
552 }
553 if ((final_opts = sshauthopt_merge(principals_opts,
554 cert_opts, &reason)) == NULL) {
555 fail_reason:
556 error("%s", reason);
557 auth_debug_add("%s", reason);
558 goto out;
559 }
560 }
561
562 /* Success */
563 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
564 "%s CA %s via %s", key->cert->key_id,
565 (unsigned long long)key->cert->serial,
566 sshkey_type(key->cert->signature_key), ca_fp,
567 options.trusted_user_ca_keys);
568 if (authoptsp != NULL) {
569 *authoptsp = final_opts;
570 final_opts = NULL;
571 }
572 ret = 1;
573 out:
574 sshauthopt_free(principals_opts);
575 sshauthopt_free(cert_opts);
576 sshauthopt_free(final_opts);
577 free(principals_file);
578 free(ca_fp);
579 return ret;
580 }
581
582 /*
583 * Checks whether key is allowed in file.
584 * returns 1 if the key is allowed or 0 otherwise.
585 */
586 static int
user_key_allowed2(struct passwd * pw,struct sshkey * key,char * file,const char * remote_ip,const char * remote_host,struct sshauthopt ** authoptsp)587 user_key_allowed2(struct passwd *pw, struct sshkey *key,
588 char *file, const char *remote_ip, const char *remote_host,
589 struct sshauthopt **authoptsp)
590 {
591 FILE *f;
592 int found_key = 0;
593
594 if (authoptsp != NULL)
595 *authoptsp = NULL;
596
597 /* Temporarily use the user's uid. */
598 temporarily_use_uid(pw);
599
600 debug("trying public key file %s", file);
601 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
602 found_key = auth_check_authkeys_file(pw, f, file,
603 key, remote_ip, remote_host, authoptsp);
604 fclose(f);
605 }
606
607 restore_uid();
608 return found_key;
609 }
610
611 /*
612 * Checks whether key is allowed in output of command.
613 * returns 1 if the key is allowed or 0 otherwise.
614 */
615 static int
user_key_command_allowed2(struct passwd * user_pw,struct sshkey * key,const char * remote_ip,const char * remote_host,const char * conn_id,const char * rdomain,struct sshauthopt ** authoptsp)616 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key,
617 const char *remote_ip, const char *remote_host,
618 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
619 {
620 struct passwd *runas_pw = NULL;
621 FILE *f = NULL;
622 int r, ok, found_key = 0;
623 int i, uid_swapped = 0, ac = 0;
624 pid_t pid;
625 char *username = NULL, *key_fp = NULL, *keytext = NULL;
626 char uidstr[32], *tmp, *command = NULL, **av = NULL;
627 void (*osigchld)(int);
628
629 if (authoptsp != NULL)
630 *authoptsp = NULL;
631 if (options.authorized_keys_command == NULL)
632 return 0;
633 if (options.authorized_keys_command_user == NULL) {
634 error("No user for AuthorizedKeysCommand specified, skipping");
635 return 0;
636 }
637
638 /*
639 * NB. all returns later this function should go via "out" to
640 * ensure the original SIGCHLD handler is restored properly.
641 */
642 osigchld = ssh_signal(SIGCHLD, SIG_DFL);
643
644 /* Prepare and verify the user for the command */
645 username = percent_expand(options.authorized_keys_command_user,
646 "u", user_pw->pw_name, (char *)NULL);
647 runas_pw = getpwnam(username);
648 if (runas_pw == NULL) {
649 error("AuthorizedKeysCommandUser \"%s\" not found: %s",
650 username, strerror(errno));
651 goto out;
652 }
653
654 /* Prepare AuthorizedKeysCommand */
655 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
656 SSH_FP_DEFAULT)) == NULL) {
657 error_f("sshkey_fingerprint failed");
658 goto out;
659 }
660 if ((r = sshkey_to_base64(key, &keytext)) != 0) {
661 error_fr(r, "sshkey_to_base64 failed");
662 goto out;
663 }
664
665 /* Turn the command into an argument vector */
666 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) {
667 error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
668 options.authorized_keys_command);
669 goto out;
670 }
671 if (ac == 0) {
672 error("AuthorizedKeysCommand \"%s\" yielded no arguments",
673 options.authorized_keys_command);
674 goto out;
675 }
676 snprintf(uidstr, sizeof(uidstr), "%llu",
677 (unsigned long long)user_pw->pw_uid);
678 for (i = 1; i < ac; i++) {
679 tmp = percent_expand(av[i],
680 "C", conn_id,
681 "D", rdomain,
682 "U", uidstr,
683 "u", user_pw->pw_name,
684 "h", user_pw->pw_dir,
685 "t", sshkey_ssh_name(key),
686 "f", key_fp,
687 "k", keytext,
688 (char *)NULL);
689 if (tmp == NULL)
690 fatal_f("percent_expand failed");
691 free(av[i]);
692 av[i] = tmp;
693 }
694 /* Prepare a printable command for logs, etc. */
695 command = argv_assemble(ac, av);
696
697 /*
698 * If AuthorizedKeysCommand was run without arguments
699 * then fall back to the old behaviour of passing the
700 * target username as a single argument.
701 */
702 if (ac == 1) {
703 av = xreallocarray(av, ac + 2, sizeof(*av));
704 av[1] = xstrdup(user_pw->pw_name);
705 av[2] = NULL;
706 /* Fix up command too, since it is used in log messages */
707 free(command);
708 xasprintf(&command, "%s %s", av[0], av[1]);
709 }
710
711 if ((pid = subprocess("AuthorizedKeysCommand", command,
712 ac, av, &f,
713 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
714 runas_pw, temporarily_use_uid, restore_uid)) == 0)
715 goto out;
716
717 uid_swapped = 1;
718 temporarily_use_uid(runas_pw);
719
720 ok = auth_check_authkeys_file(user_pw, f,
721 options.authorized_keys_command, key, remote_ip,
722 remote_host, authoptsp);
723
724 fclose(f);
725 f = NULL;
726
727 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
728 goto out;
729
730 /* Read completed successfully */
731 found_key = ok;
732 out:
733 if (f != NULL)
734 fclose(f);
735 ssh_signal(SIGCHLD, osigchld);
736 for (i = 0; i < ac; i++)
737 free(av[i]);
738 free(av);
739 if (uid_swapped)
740 restore_uid();
741 free(command);
742 free(username);
743 free(key_fp);
744 free(keytext);
745 return found_key;
746 }
747
748 /*
749 * Check whether key authenticates and authorises the user.
750 */
751 int
user_key_allowed(struct ssh * ssh,struct passwd * pw,struct sshkey * key,int auth_attempt,struct sshauthopt ** authoptsp)752 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
753 int auth_attempt, struct sshauthopt **authoptsp)
754 {
755 u_int success = 0, i;
756 char *file, *conn_id;
757 struct sshauthopt *opts = NULL;
758 const char *rdomain, *remote_ip, *remote_host;
759
760 if (authoptsp != NULL)
761 *authoptsp = NULL;
762
763 if (auth_key_is_revoked(key))
764 return 0;
765 if (sshkey_is_cert(key) &&
766 auth_key_is_revoked(key->cert->signature_key))
767 return 0;
768
769 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL)
770 rdomain = "";
771 remote_ip = ssh_remote_ipaddr(ssh);
772 remote_host = auth_get_canonical_hostname(ssh, options.use_dns);
773 xasprintf(&conn_id, "%s %d %s %d",
774 ssh_local_ipaddr(ssh), ssh_local_port(ssh),
775 remote_ip, ssh_remote_port(ssh));
776
777 for (i = 0; !success && i < options.num_authkeys_files; i++) {
778 if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
779 continue;
780 file = expand_authorized_keys(
781 options.authorized_keys_files[i], pw);
782 success = user_key_allowed2(pw, key, file,
783 remote_ip, remote_host, &opts);
784 free(file);
785 if (!success) {
786 sshauthopt_free(opts);
787 opts = NULL;
788 }
789 }
790 if (success)
791 goto out;
792
793 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host,
794 conn_id, rdomain, &opts)) != 0)
795 goto out;
796 sshauthopt_free(opts);
797 opts = NULL;
798
799 if ((success = user_key_command_allowed2(pw, key, remote_ip,
800 remote_host, conn_id, rdomain, &opts)) != 0)
801 goto out;
802 sshauthopt_free(opts);
803 opts = NULL;
804
805 out:
806 free(conn_id);
807 if (success && authoptsp != NULL) {
808 *authoptsp = opts;
809 opts = NULL;
810 }
811 sshauthopt_free(opts);
812 return success;
813 }
814
815 Authmethod method_pubkey = {
816 "publickey",
817 "publickey-hostbound-v00@openssh.com",
818 userauth_pubkey,
819 &options.pubkey_authentication
820 };
821