1 /* $OpenBSD: auth2-pubkey.c,v 1.126 2026/04/02 07:48:13 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 #include <paths.h>
34 #include <pwd.h>
35 #include <glob.h>
36 #include <signal.h>
37 #include <stdio.h>
38 #include <stdarg.h>
39 #include <string.h>
40 #include <time.h>
41 #include <unistd.h>
42 #include <limits.h>
43
44 #include "xmalloc.h"
45 #include "ssh.h"
46 #include "ssh2.h"
47 #include "packet.h"
48 #include "kex.h"
49 #include "sshbuf.h"
50 #include "log.h"
51 #include "misc.h"
52 #include "servconf.h"
53 #include "compat.h"
54 #include "sshkey.h"
55 #include "hostfile.h"
56 #include "auth.h"
57 #include "pathnames.h"
58 #include "uidswap.h"
59 #include "auth-options.h"
60 #include "canohost.h"
61 #ifdef GSSAPI
62 #include "ssh-gss.h"
63 #endif
64 #include "monitor_wrap.h"
65 #include "authfile.h"
66 #include "match.h"
67 #include "ssherr.h"
68 #include "channels.h" /* XXX for session.h */
69 #include "session.h" /* XXX for child_set_env(); refactor? */
70 #include "sk-api.h"
71
72 /* import */
73 extern ServerOptions options;
74 extern struct authmethod_cfg methodcfg_pubkey;
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 || (sshkey_type_plain(pktype) == KEY_ECDSA &&
152 sshkey_ecdsa_nid_from_name(pkalg) != key->ecdsa_nid)) {
153 error_f("key type mismatch for decoded key "
154 "(received %s, expected %s)", sshkey_ssh_name(key), pkalg);
155 goto done;
156 }
157 if (auth2_key_already_used(authctxt, key)) {
158 logit("refusing previously-used %s key", sshkey_type(key));
159 goto done;
160 }
161 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) {
162 logit_f("signature algorithm %s not in "
163 "PubkeyAcceptedAlgorithms", pkalg);
164 goto done;
165 }
166 if ((r = sshkey_check_cert_sigtype(key,
167 options.ca_sign_algorithms)) != 0) {
168 logit_fr(r, "certificate signature algorithm %s",
169 (key->cert == NULL || key->cert->signature_type == NULL) ?
170 "(null)" : key->cert->signature_type);
171 goto done;
172 }
173 if ((r = sshkey_check_rsa_length(key,
174 options.required_rsa_size)) != 0) {
175 logit_r(r, "refusing %s key", sshkey_type(key));
176 goto done;
177 }
178 key_s = format_key(key);
179 if (sshkey_is_cert(key))
180 ca_s = format_key(key->cert->signature_key);
181
182 if (have_sig) {
183 debug3_f("%s have %s signature for %s%s%s",
184 method, pkalg, key_s,
185 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
186 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
187 (r = sshpkt_get_end(ssh)) != 0)
188 fatal_fr(r, "parse signature packet");
189 if ((b = sshbuf_new()) == NULL)
190 fatal_f("sshbuf_new failed");
191 if (ssh->compat & SSH_OLD_SESSIONID) {
192 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
193 fatal_fr(r, "put old session id");
194 } else {
195 if ((r = sshbuf_put_stringb(b,
196 ssh->kex->session_id)) != 0)
197 fatal_fr(r, "put session id");
198 }
199 if (!authctxt->valid || authctxt->user == NULL) {
200 debug2_f("disabled because of invalid user");
201 goto done;
202 }
203 /* reconstruct packet */
204 xasprintf(&userstyle, "%s%s%s", authctxt->user,
205 authctxt->style ? ":" : "",
206 authctxt->style ? authctxt->style : "");
207 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
208 (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
209 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
210 (r = sshbuf_put_cstring(b, method)) != 0 ||
211 (r = sshbuf_put_u8(b, have_sig)) != 0 ||
212 (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
213 (r = sshbuf_put_string(b, pkblob, blen)) != 0)
214 fatal_fr(r, "reconstruct %s packet", method);
215 if (hostbound &&
216 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0)
217 fatal_fr(r, "reconstruct %s packet", method);
218 #ifdef DEBUG_PK
219 sshbuf_dump(b, stderr);
220 #endif
221 /* test for correct signature */
222 authenticated = 0;
223 if (mm_user_key_allowed(ssh, pw, key, 1, &authopts) &&
224 mm_sshkey_verify(key, sig, slen,
225 sshbuf_ptr(b), sshbuf_len(b),
226 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
227 ssh->compat, &sig_details) == 0) {
228 authenticated = 1;
229 }
230 if (authenticated == 1 && sig_details != NULL) {
231 auth2_record_info(authctxt, "signature count = %u",
232 sig_details->sk_counter);
233 debug_f("sk_counter = %u, sk_flags = 0x%02x",
234 sig_details->sk_counter, sig_details->sk_flags);
235 req_presence = (options.pubkey_auth_options &
236 PUBKEYAUTH_TOUCH_REQUIRED) ||
237 !authopts->no_require_user_presence;
238 if (req_presence && (sig_details->sk_flags &
239 SSH_SK_USER_PRESENCE_REQD) == 0) {
240 error("public key %s signature for %s%s from "
241 "%.128s port %d rejected: user presence "
242 "(authenticator touch) requirement "
243 "not met ", key_s,
244 authctxt->valid ? "" : "invalid user ",
245 authctxt->user, ssh_remote_ipaddr(ssh),
246 ssh_remote_port(ssh));
247 authenticated = 0;
248 goto done;
249 }
250 req_verify = (options.pubkey_auth_options &
251 PUBKEYAUTH_VERIFY_REQUIRED) ||
252 authopts->require_verify;
253 if (req_verify && (sig_details->sk_flags &
254 SSH_SK_USER_VERIFICATION_REQD) == 0) {
255 error("public key %s signature for %s%s from "
256 "%.128s port %d rejected: user "
257 "verification requirement not met ", key_s,
258 authctxt->valid ? "" : "invalid user ",
259 authctxt->user, ssh_remote_ipaddr(ssh),
260 ssh_remote_port(ssh));
261 authenticated = 0;
262 goto done;
263 }
264 }
265 auth2_record_key(authctxt, authenticated, key);
266 } else {
267 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s,
268 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s);
269
270 if ((r = sshpkt_get_end(ssh)) != 0)
271 fatal_fr(r, "parse packet");
272
273 if (!authctxt->valid || authctxt->user == NULL) {
274 debug2_f("disabled because of invalid user");
275 goto done;
276 }
277 /* XXX fake reply and always send PK_OK ? */
278 /*
279 * XXX this allows testing whether a user is allowed
280 * to login: if you happen to have a valid pubkey this
281 * message is sent. the message is NEVER sent at all
282 * if a user is not allowed to login. is this an
283 * issue? -markus
284 */
285 if (mm_user_key_allowed(ssh, pw, key, 0, NULL)) {
286 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
287 != 0 ||
288 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
289 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
290 (r = sshpkt_send(ssh)) != 0 ||
291 (r = ssh_packet_write_wait(ssh)) != 0)
292 fatal_fr(r, "send packet");
293 authctxt->postponed = 1;
294 }
295 }
296 done:
297 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
298 debug_f("key options inconsistent with existing");
299 authenticated = 0;
300 }
301 debug2_f("authenticated %d pkalg %s", authenticated, pkalg);
302
303 sshbuf_free(b);
304 sshauthopt_free(authopts);
305 sshkey_free(key);
306 sshkey_free(hostkey);
307 free(userstyle);
308 free(pkalg);
309 free(pkblob);
310 free(key_s);
311 free(ca_s);
312 free(sig);
313 sshkey_sig_details_free(sig_details);
314 return authenticated;
315 }
316
317 static int
match_principals_file(struct passwd * pw,char * file,struct sshkey_cert * cert,struct sshauthopt ** authoptsp)318 match_principals_file(struct passwd *pw, char *file,
319 struct sshkey_cert *cert, struct sshauthopt **authoptsp)
320 {
321 FILE *f;
322 int r, success = 0;
323 size_t i;
324 glob_t gl;
325 struct sshauthopt *opts = NULL;
326
327 if (authoptsp != NULL)
328 *authoptsp = NULL;
329
330 temporarily_use_uid(pw);
331 r = glob(file, 0, NULL, &gl);
332 restore_uid();
333 if (r != 0) {
334 if (r != GLOB_NOMATCH) {
335 logit_f("glob \"%s\" failed", file);
336 }
337 return 0;
338 } else if (gl.gl_pathc > INT_MAX) {
339 fatal_f("too many glob results for \"%s\"", file);
340 } else if (gl.gl_pathc > 1) {
341 debug2_f("glob \"%s\" returned %zu matches", file,
342 gl.gl_pathc);
343 }
344 for (i = 0; !success && i < gl.gl_pathc; i++) {
345 temporarily_use_uid(pw);
346 debug("trying authorized principals file %s", file);
347 if ((f = auth_openprincipals(gl.gl_pathv[i], pw,
348 options.strict_modes)) == NULL) {
349 restore_uid();
350 continue;
351 }
352 success = auth_process_principals(f, gl.gl_pathv[i],
353 cert, &opts);
354 fclose(f);
355 restore_uid();
356 if (!success) {
357 sshauthopt_free(opts);
358 opts = NULL;
359 }
360 }
361 globfree(&gl);
362 if (success && authoptsp != NULL) {
363 *authoptsp = opts;
364 opts = NULL;
365 }
366 sshauthopt_free(opts);
367 return success;
368 }
369
370 /*
371 * Checks whether principal is allowed in output of command.
372 * returns 1 if the principal is allowed or 0 otherwise.
373 */
374 static int
match_principals_command(struct passwd * user_pw,const struct sshkey * key,const char * conn_id,const char * rdomain,struct sshauthopt ** authoptsp)375 match_principals_command(struct passwd *user_pw, const struct sshkey *key,
376 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
377 {
378 struct passwd *runas_pw = NULL;
379 const struct sshkey_cert *cert = key->cert;
380 FILE *f = NULL;
381 int r, ok, found_principal = 0;
382 int i, ac = 0, uid_swapped = 0;
383 pid_t pid;
384 char *tmp, *username = NULL, *command = NULL, **av = NULL;
385 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
386 char serial_s[32], uidstr[32];
387 void (*osigchld)(int);
388
389 if (authoptsp != NULL)
390 *authoptsp = NULL;
391 if (options.authorized_principals_command == NULL)
392 return 0;
393 if (options.authorized_principals_command_user == NULL) {
394 error("No user for AuthorizedPrincipalsCommand specified, "
395 "skipping");
396 return 0;
397 }
398
399 /*
400 * NB. all returns later this function should go via "out" to
401 * ensure the original SIGCHLD handler is restored properly.
402 */
403 osigchld = ssh_signal(SIGCHLD, SIG_DFL);
404
405 /* Prepare and verify the user for the command */
406 username = percent_expand(options.authorized_principals_command_user,
407 "u", user_pw->pw_name, (char *)NULL);
408 runas_pw = getpwnam(username);
409 if (runas_pw == NULL) {
410 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
411 username, strerror(errno));
412 goto out;
413 }
414
415 /* Turn the command into an argument vector */
416 if (argv_split(options.authorized_principals_command,
417 &ac, &av, 0) != 0) {
418 error("AuthorizedPrincipalsCommand \"%s\" contains "
419 "invalid quotes", options.authorized_principals_command);
420 goto out;
421 }
422 if (ac == 0) {
423 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
424 options.authorized_principals_command);
425 goto out;
426 }
427 if ((ca_fp = sshkey_fingerprint(cert->signature_key,
428 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
429 error_f("sshkey_fingerprint failed");
430 goto out;
431 }
432 if ((key_fp = sshkey_fingerprint(key,
433 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
434 error_f("sshkey_fingerprint failed");
435 goto out;
436 }
437 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
438 error_fr(r, "sshkey_to_base64 failed");
439 goto out;
440 }
441 if ((r = sshkey_to_base64(key, &keytext)) != 0) {
442 error_fr(r, "sshkey_to_base64 failed");
443 goto out;
444 }
445 snprintf(serial_s, sizeof(serial_s), "%llu",
446 (unsigned long long)cert->serial);
447 snprintf(uidstr, sizeof(uidstr), "%llu",
448 (unsigned long long)user_pw->pw_uid);
449 for (i = 1; i < ac; i++) {
450 tmp = percent_expand(av[i],
451 "C", conn_id,
452 "D", rdomain,
453 "U", uidstr,
454 "u", user_pw->pw_name,
455 "h", user_pw->pw_dir,
456 "t", sshkey_ssh_name(key),
457 "T", sshkey_ssh_name(cert->signature_key),
458 "f", key_fp,
459 "F", ca_fp,
460 "k", keytext,
461 "K", catext,
462 "i", cert->key_id,
463 "s", serial_s,
464 (char *)NULL);
465 if (tmp == NULL)
466 fatal_f("percent_expand failed");
467 free(av[i]);
468 av[i] = tmp;
469 }
470 /* Prepare a printable command for logs, etc. */
471 command = argv_assemble(ac, av);
472
473 if ((pid = subprocess("AuthorizedPrincipalsCommand", command,
474 ac, av, &f,
475 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
476 runas_pw, temporarily_use_uid, restore_uid)) == 0)
477 goto out;
478
479 uid_swapped = 1;
480 temporarily_use_uid(runas_pw);
481
482 ok = auth_process_principals(f, "(command)", cert, authoptsp);
483
484 fclose(f);
485 f = NULL;
486
487 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
488 goto out;
489
490 /* Read completed successfully */
491 found_principal = ok;
492 out:
493 if (f != NULL)
494 fclose(f);
495 ssh_signal(SIGCHLD, osigchld);
496 for (i = 0; i < ac; i++)
497 free(av[i]);
498 free(av);
499 if (uid_swapped)
500 restore_uid();
501 free(command);
502 free(username);
503 free(ca_fp);
504 free(key_fp);
505 free(catext);
506 free(keytext);
507 return found_principal;
508 }
509
510 /* Authenticate a certificate key against TrustedUserCAKeys */
511 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)512 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key,
513 const char *remote_ip, const char *remote_host,
514 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
515 {
516 char *ca_fp, *principals_file = NULL;
517 const char *reason;
518 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
519 struct sshauthopt *final_opts = NULL;
520 int r, ret = 0, found_principal = 0, use_authorized_principals;
521
522 if (authoptsp != NULL)
523 *authoptsp = NULL;
524
525 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
526 return 0;
527
528 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
529 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
530 return 0;
531
532 if ((r = sshkey_in_file(key->cert->signature_key,
533 options.trusted_user_ca_keys, 1, 0)) != 0) {
534 debug2_fr(r, "CA %s %s is not listed in %s",
535 sshkey_type(key->cert->signature_key), ca_fp,
536 options.trusted_user_ca_keys);
537 goto out;
538 }
539 /*
540 * If AuthorizedPrincipals is in use, then compare the certificate
541 * principals against the names in that file rather than matching
542 * against the username.
543 */
544 if ((principals_file = authorized_principals_file(pw)) != NULL) {
545 if (match_principals_file(pw, principals_file,
546 key->cert, &principals_opts))
547 found_principal = 1;
548 }
549 /* Try querying command if specified */
550 if (!found_principal && match_principals_command(pw, key,
551 conn_id, rdomain, &principals_opts))
552 found_principal = 1;
553 /* If principals file or command is specified, then require a match */
554 use_authorized_principals = principals_file != NULL ||
555 options.authorized_principals_command != NULL;
556 if (!found_principal && use_authorized_principals) {
557 reason = "Certificate does not contain an authorized principal";
558 goto fail_reason;
559 }
560 if (use_authorized_principals && principals_opts == NULL)
561 fatal_f("internal error: missing principals_opts");
562 if (sshkey_cert_check_authority_now(key, 0, 0,
563 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
564 goto fail_reason;
565
566 /* Check authority from options in key and from principals file/cmd */
567 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
568 reason = "Invalid certificate options";
569 goto fail_reason;
570 }
571 if (auth_authorise_keyopts(pw, cert_opts, 0,
572 remote_ip, remote_host, "cert") != 0) {
573 reason = "Refused by certificate options";
574 goto fail_reason;
575 }
576 if (principals_opts == NULL) {
577 final_opts = cert_opts;
578 cert_opts = NULL;
579 } else {
580 if (auth_authorise_keyopts(pw, principals_opts, 0,
581 remote_ip, remote_host, "principals") != 0) {
582 reason = "Refused by certificate principals options";
583 goto fail_reason;
584 }
585 if ((final_opts = sshauthopt_merge(principals_opts,
586 cert_opts, &reason)) == NULL) {
587 fail_reason:
588 error("Refusing certificate ID \"%s\" serial=%llu "
589 "signed by %s CA %s: %s", key->cert->key_id,
590 (unsigned long long)key->cert->serial,
591 sshkey_type(key->cert->signature_key), ca_fp,
592 reason);
593 auth_debug_add("Refused Certificate ID \"%s\" "
594 "serial=%llu: %s", key->cert->key_id,
595 (unsigned long long)key->cert->serial, reason);
596 goto out;
597 }
598 }
599
600 /* Success */
601 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
602 "%s CA %s via %s", key->cert->key_id,
603 (unsigned long long)key->cert->serial,
604 sshkey_type(key->cert->signature_key), ca_fp,
605 options.trusted_user_ca_keys);
606 if (authoptsp != NULL) {
607 *authoptsp = final_opts;
608 final_opts = NULL;
609 }
610 ret = 1;
611 out:
612 sshauthopt_free(principals_opts);
613 sshauthopt_free(cert_opts);
614 sshauthopt_free(final_opts);
615 free(principals_file);
616 free(ca_fp);
617 return ret;
618 }
619
620 /*
621 * Checks whether key is allowed in file.
622 * returns 1 if the key is allowed or 0 otherwise.
623 */
624 static int
user_key_allowed2(struct passwd * pw,struct sshkey * key,char * file,const char * remote_ip,const char * remote_host,struct sshauthopt ** authoptsp)625 user_key_allowed2(struct passwd *pw, struct sshkey *key,
626 char *file, const char *remote_ip, const char *remote_host,
627 struct sshauthopt **authoptsp)
628 {
629 FILE *f;
630 int found_key = 0;
631
632 if (authoptsp != NULL)
633 *authoptsp = NULL;
634
635 /* Temporarily use the user's uid. */
636 temporarily_use_uid(pw);
637
638 debug("trying public key file %s", file);
639 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
640 found_key = auth_check_authkeys_file(pw, f, file,
641 key, remote_ip, remote_host, authoptsp);
642 fclose(f);
643 }
644
645 restore_uid();
646 return found_key;
647 }
648
649 /*
650 * Checks whether key is allowed in output of command.
651 * returns 1 if the key is allowed or 0 otherwise.
652 */
653 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)654 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key,
655 const char *remote_ip, const char *remote_host,
656 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp)
657 {
658 struct passwd *runas_pw = NULL;
659 FILE *f = NULL;
660 int r, ok, found_key = 0;
661 int i, uid_swapped = 0, ac = 0;
662 pid_t pid;
663 char *username = NULL, *key_fp = NULL, *keytext = NULL;
664 char uidstr[32], *tmp, *command = NULL, **av = NULL;
665 void (*osigchld)(int);
666
667 if (authoptsp != NULL)
668 *authoptsp = NULL;
669 if (options.authorized_keys_command == NULL)
670 return 0;
671 if (options.authorized_keys_command_user == NULL) {
672 error("No user for AuthorizedKeysCommand specified, skipping");
673 return 0;
674 }
675
676 /*
677 * NB. all returns later this function should go via "out" to
678 * ensure the original SIGCHLD handler is restored properly.
679 */
680 osigchld = ssh_signal(SIGCHLD, SIG_DFL);
681
682 /* Prepare and verify the user for the command */
683 username = percent_expand(options.authorized_keys_command_user,
684 "u", user_pw->pw_name, (char *)NULL);
685 runas_pw = getpwnam(username);
686 if (runas_pw == NULL) {
687 error("AuthorizedKeysCommandUser \"%s\" not found: %s",
688 username, strerror(errno));
689 goto out;
690 }
691
692 /* Prepare AuthorizedKeysCommand */
693 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
694 SSH_FP_DEFAULT)) == NULL) {
695 error_f("sshkey_fingerprint failed");
696 goto out;
697 }
698 if ((r = sshkey_to_base64(key, &keytext)) != 0) {
699 error_fr(r, "sshkey_to_base64 failed");
700 goto out;
701 }
702
703 /* Turn the command into an argument vector */
704 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) {
705 error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
706 options.authorized_keys_command);
707 goto out;
708 }
709 if (ac == 0) {
710 error("AuthorizedKeysCommand \"%s\" yielded no arguments",
711 options.authorized_keys_command);
712 goto out;
713 }
714 snprintf(uidstr, sizeof(uidstr), "%llu",
715 (unsigned long long)user_pw->pw_uid);
716 for (i = 1; i < ac; i++) {
717 tmp = percent_expand(av[i],
718 "C", conn_id,
719 "D", rdomain,
720 "U", uidstr,
721 "u", user_pw->pw_name,
722 "h", user_pw->pw_dir,
723 "t", sshkey_ssh_name(key),
724 "f", key_fp,
725 "k", keytext,
726 (char *)NULL);
727 if (tmp == NULL)
728 fatal_f("percent_expand failed");
729 free(av[i]);
730 av[i] = tmp;
731 }
732 /* Prepare a printable command for logs, etc. */
733 command = argv_assemble(ac, av);
734
735 /*
736 * If AuthorizedKeysCommand was run without arguments
737 * then fall back to the old behaviour of passing the
738 * target username as a single argument.
739 */
740 if (ac == 1) {
741 av = xreallocarray(av, ac + 2, sizeof(*av));
742 av[1] = xstrdup(user_pw->pw_name);
743 av[2] = NULL;
744 /* Fix up command too, since it is used in log messages */
745 free(command);
746 xasprintf(&command, "%s %s", av[0], av[1]);
747 }
748
749 if ((pid = subprocess("AuthorizedKeysCommand", command,
750 ac, av, &f,
751 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD,
752 runas_pw, temporarily_use_uid, restore_uid)) == 0)
753 goto out;
754
755 uid_swapped = 1;
756 temporarily_use_uid(runas_pw);
757
758 ok = auth_check_authkeys_file(user_pw, f,
759 options.authorized_keys_command, key, remote_ip,
760 remote_host, authoptsp);
761
762 fclose(f);
763 f = NULL;
764
765 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
766 goto out;
767
768 /* Read completed successfully */
769 found_key = ok;
770 out:
771 if (f != NULL)
772 fclose(f);
773 ssh_signal(SIGCHLD, osigchld);
774 for (i = 0; i < ac; i++)
775 free(av[i]);
776 free(av);
777 if (uid_swapped)
778 restore_uid();
779 free(command);
780 free(username);
781 free(key_fp);
782 free(keytext);
783 return found_key;
784 }
785
786 /*
787 * Check whether key authenticates and authorises the user.
788 */
789 int
user_key_allowed(struct ssh * ssh,struct passwd * pw,struct sshkey * key,int auth_attempt,struct sshauthopt ** authoptsp)790 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
791 int auth_attempt, struct sshauthopt **authoptsp)
792 {
793 u_int success = 0, i, j;
794 char *file = NULL, *conn_id;
795 struct sshauthopt *opts = NULL;
796 const char *rdomain, *remote_ip, *remote_host;
797
798 if (authoptsp != NULL)
799 *authoptsp = NULL;
800
801 if (auth_key_is_revoked(key))
802 return 0;
803 if (sshkey_is_cert(key) &&
804 auth_key_is_revoked(key->cert->signature_key))
805 return 0;
806
807 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL)
808 rdomain = "";
809 remote_ip = ssh_remote_ipaddr(ssh);
810 remote_host = auth_get_canonical_hostname(ssh, options.use_dns);
811 xasprintf(&conn_id, "%s %d %s %d",
812 ssh_local_ipaddr(ssh), ssh_local_port(ssh),
813 remote_ip, ssh_remote_port(ssh));
814
815 for (i = 0; !success && i < options.num_authkeys_files; i++) {
816 int r;
817 glob_t gl;
818
819 if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
820 continue;
821 file = expand_authorized_keys(
822 options.authorized_keys_files[i], pw);
823 temporarily_use_uid(pw);
824 r = glob(file, 0, NULL, &gl);
825 restore_uid();
826 if (r != 0) {
827 if (r != GLOB_NOMATCH) {
828 logit_f("glob \"%s\" failed", file);
829 }
830 free(file);
831 file = NULL;
832 continue;
833 } else if (gl.gl_pathc > INT_MAX) {
834 fatal_f("too many glob results for \"%s\"", file);
835 } else if (gl.gl_pathc > 1) {
836 debug2_f("glob \"%s\" returned %zu matches", file,
837 gl.gl_pathc);
838 }
839 for (j = 0; !success && j < gl.gl_pathc; j++) {
840 success = user_key_allowed2(pw, key, gl.gl_pathv[j],
841 remote_ip, remote_host, &opts);
842 if (!success) {
843 sshauthopt_free(opts);
844 opts = NULL;
845 }
846 }
847 free(file);
848 file = NULL;
849 globfree(&gl);
850 }
851 if (success)
852 goto out;
853
854 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host,
855 conn_id, rdomain, &opts)) != 0)
856 goto out;
857 sshauthopt_free(opts);
858 opts = NULL;
859
860 if ((success = user_key_command_allowed2(pw, key, remote_ip,
861 remote_host, conn_id, rdomain, &opts)) != 0)
862 goto out;
863 sshauthopt_free(opts);
864 opts = NULL;
865
866 out:
867 free(conn_id);
868 if (success && authoptsp != NULL) {
869 *authoptsp = opts;
870 opts = NULL;
871 }
872 sshauthopt_free(opts);
873 return success;
874 }
875
876 Authmethod method_pubkey = {
877 &methodcfg_pubkey,
878 userauth_pubkey,
879 };
880