1 /* $OpenBSD: auth2-pubkey.c,v 1.84 2018/08/23 03:01:08 djm Exp $ */
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
28 #include <sys/types.h>
57 #include "pathnames.h"
59 #include "auth-options.h"
64 #include "monitor_wrap.h"
68 #include "channels.h" /* XXX for session.h */
69 #include "session.h" /* XXX for child_set_env(); refactor? */
72 extern ServerOptions options;
73 extern u_char *session_id2;
74 extern u_int session_id2_len;
77 format_key(const struct sshkey *key)
79 char *ret, *fp = sshkey_fingerprint(key,
80 options.fingerprint_hash, SSH_FP_DEFAULT);
82 xasprintf(&ret, "%s %s", sshkey_type(key), fp);
88 userauth_pubkey(struct ssh *ssh)
90 Authctxt *authctxt = ssh->authctxt;
91 struct passwd *pw = authctxt->pw;
92 struct sshbuf *b = NULL;
93 struct sshkey *key = NULL;
94 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
95 u_char *pkblob = NULL, *sig = NULL, have_sig;
98 int authenticated = 0;
99 struct sshauthopt *authopts = NULL;
101 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
102 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
103 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
104 fatal("%s: parse request failed: %s", __func__, ssh_err(r));
105 pktype = sshkey_type_from_name(pkalg);
106 if (pktype == KEY_UNSPEC) {
107 /* this is perfectly legal */
108 verbose("%s: unsupported public key algorithm: %s",
112 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
113 error("%s: could not parse key: %s", __func__, ssh_err(r));
117 error("%s: cannot decode key: %s", __func__, pkalg);
120 if (key->type != pktype) {
121 error("%s: type mismatch for decoded key "
122 "(received %d, expected %d)", __func__, key->type, pktype);
125 if (sshkey_type_plain(key->type) == KEY_RSA &&
126 (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
127 logit("Refusing RSA key because client uses unsafe "
131 if (auth2_key_already_used(authctxt, key)) {
132 logit("refusing previously-used %s key", sshkey_type(key));
135 if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
136 logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
137 __func__, sshkey_ssh_name(key));
141 key_s = format_key(key);
142 if (sshkey_is_cert(key))
143 ca_s = format_key(key->cert->signature_key);
146 debug3("%s: have %s signature for %s%s%s",
147 __func__, pkalg, key_s,
148 ca_s == NULL ? "" : " CA ",
149 ca_s == NULL ? "" : ca_s);
150 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
151 (r = sshpkt_get_end(ssh)) != 0)
152 fatal("%s: %s", __func__, ssh_err(r));
153 if ((b = sshbuf_new()) == NULL)
154 fatal("%s: sshbuf_new failed", __func__);
155 if (ssh->compat & SSH_OLD_SESSIONID) {
156 if ((r = sshbuf_put(b, session_id2,
157 session_id2_len)) != 0)
158 fatal("%s: sshbuf_put session id: %s",
159 __func__, ssh_err(r));
161 if ((r = sshbuf_put_string(b, session_id2,
162 session_id2_len)) != 0)
163 fatal("%s: sshbuf_put_string session id: %s",
164 __func__, ssh_err(r));
166 if (!authctxt->valid || authctxt->user == NULL) {
167 debug2("%s: disabled because of invalid user",
171 /* reconstruct packet */
172 xasprintf(&userstyle, "%s%s%s", authctxt->user,
173 authctxt->style ? ":" : "",
174 authctxt->style ? authctxt->style : "");
175 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
176 (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
177 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
178 (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
179 (r = sshbuf_put_u8(b, have_sig)) != 0 ||
180 (r = sshbuf_put_cstring(b, pkalg) != 0) ||
181 (r = sshbuf_put_string(b, pkblob, blen)) != 0)
182 fatal("%s: build packet failed: %s",
183 __func__, ssh_err(r));
185 sshbuf_dump(b, stderr);
187 /* test for correct signature */
189 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
190 PRIVSEP(sshkey_verify(key, sig, slen,
191 sshbuf_ptr(b), sshbuf_len(b),
192 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
193 ssh->compat)) == 0) {
196 auth2_record_key(authctxt, authenticated, key);
198 debug("%s: test pkalg %s pkblob %s%s%s",
199 __func__, pkalg, key_s,
200 ca_s == NULL ? "" : " CA ",
201 ca_s == NULL ? "" : ca_s);
203 if ((r = sshpkt_get_end(ssh)) != 0)
204 fatal("%s: %s", __func__, ssh_err(r));
206 if (!authctxt->valid || authctxt->user == NULL) {
207 debug2("%s: disabled because of invalid user",
211 /* XXX fake reply and always send PK_OK ? */
213 * XXX this allows testing whether a user is allowed
214 * to login: if you happen to have a valid pubkey this
215 * message is sent. the message is NEVER sent at all
216 * if a user is not allowed to login. is this an
219 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
220 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
222 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
223 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
224 (r = sshpkt_send(ssh)) != 0 ||
225 (r = ssh_packet_write_wait(ssh)) != 0)
226 fatal("%s: %s", __func__, ssh_err(r));
227 authctxt->postponed = 1;
231 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
232 debug("%s: key options inconsistent with existing", __func__);
235 debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
238 sshauthopt_free(authopts);
246 return authenticated;
250 match_principals_option(const char *principal_list, struct sshkey_cert *cert)
255 /* XXX percent_expand() sequences for authorized_principals? */
257 for (i = 0; i < cert->nprincipals; i++) {
258 if ((result = match_list(cert->principals[i],
259 principal_list, NULL)) != NULL) {
260 debug3("matched principal from key options \"%.100s\"",
270 * Process a single authorized_principals format line. Returns 0 and sets
271 * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
272 * log preamble for file/line information.
275 check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
276 const char *loc, struct sshauthopt **authoptsp)
279 char *ep, *line_opts;
280 const char *reason = NULL;
281 struct sshauthopt *opts = NULL;
283 if (authoptsp != NULL)
286 /* Trim trailing whitespace. */
287 ep = cp + strlen(cp) - 1;
288 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
292 * If the line has internal whitespace then assume it has
296 if ((ep = strrchr(cp, ' ')) != NULL ||
297 (ep = strrchr(cp, '\t')) != NULL) {
298 for (; *ep == ' ' || *ep == '\t'; ep++)
303 if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
304 debug("%s: bad principals options: %s", loc, reason);
305 auth_debug_add("%s: bad principals options: %s", loc, reason);
308 /* Check principals in cert against those on line */
309 for (i = 0; i < cert->nprincipals; i++) {
310 if (strcmp(cp, cert->principals[i]) != 0)
312 debug3("%s: matched principal \"%.100s\"",
313 loc, cert->principals[i]);
316 if (found && authoptsp != NULL) {
320 sshauthopt_free(opts);
321 return found ? 0 : -1;
325 process_principals(struct ssh *ssh, FILE *f, const char *file,
326 const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
328 char loc[256], *line = NULL, *cp, *ep;
331 u_int found_principal = 0;
333 if (authoptsp != NULL)
336 while (getline(&line, &linesize, f) != -1) {
338 /* Always consume entire input */
342 /* Skip leading whitespace. */
343 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
345 /* Skip blank and comment lines. */
346 if ((ep = strchr(cp, '#')) != NULL)
348 if (!*cp || *cp == '\n')
351 snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
352 if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
356 return found_principal;
359 /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
362 match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
363 struct sshkey_cert *cert, struct sshauthopt **authoptsp)
368 if (authoptsp != NULL)
371 temporarily_use_uid(pw);
372 debug("trying authorized principals file %s", file);
373 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
377 success = process_principals(ssh, f, file, cert, authoptsp);
384 * Checks whether principal is allowed in output of command.
385 * returns 1 if the principal is allowed or 0 otherwise.
388 match_principals_command(struct ssh *ssh, struct passwd *user_pw,
389 const struct sshkey *key, struct sshauthopt **authoptsp)
391 struct passwd *runas_pw = NULL;
392 const struct sshkey_cert *cert = key->cert;
394 int r, ok, found_principal = 0;
395 int i, ac = 0, uid_swapped = 0;
397 char *tmp, *username = NULL, *command = NULL, **av = NULL;
398 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
399 char serial_s[16], uidstr[32];
400 void (*osigchld)(int);
402 if (authoptsp != NULL)
404 if (options.authorized_principals_command == NULL)
406 if (options.authorized_principals_command_user == NULL) {
407 error("No user for AuthorizedPrincipalsCommand specified, "
413 * NB. all returns later this function should go via "out" to
414 * ensure the original SIGCHLD handler is restored properly.
416 osigchld = signal(SIGCHLD, SIG_DFL);
418 /* Prepare and verify the user for the command */
419 username = percent_expand(options.authorized_principals_command_user,
420 "u", user_pw->pw_name, (char *)NULL);
421 runas_pw = getpwnam(username);
422 if (runas_pw == NULL) {
423 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
424 username, strerror(errno));
428 /* Turn the command into an argument vector */
429 if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
430 error("AuthorizedPrincipalsCommand \"%s\" contains "
431 "invalid quotes", command);
435 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
439 if ((ca_fp = sshkey_fingerprint(cert->signature_key,
440 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
441 error("%s: sshkey_fingerprint failed", __func__);
444 if ((key_fp = sshkey_fingerprint(key,
445 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
446 error("%s: sshkey_fingerprint failed", __func__);
449 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
450 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
453 if ((r = sshkey_to_base64(key, &keytext)) != 0) {
454 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
457 snprintf(serial_s, sizeof(serial_s), "%llu",
458 (unsigned long long)cert->serial);
459 snprintf(uidstr, sizeof(uidstr), "%llu",
460 (unsigned long long)user_pw->pw_uid);
461 for (i = 1; i < ac; i++) {
462 tmp = percent_expand(av[i],
464 "u", user_pw->pw_name,
465 "h", user_pw->pw_dir,
466 "t", sshkey_ssh_name(key),
467 "T", sshkey_ssh_name(cert->signature_key),
476 fatal("%s: percent_expand failed", __func__);
480 /* Prepare a printable command for logs, etc. */
481 command = argv_assemble(ac, av);
483 if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
485 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
489 temporarily_use_uid(runas_pw);
491 ok = process_principals(ssh, f, "(command)", cert, authoptsp);
496 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
499 /* Read completed successfully */
500 found_principal = ok;
504 signal(SIGCHLD, osigchld);
505 for (i = 0; i < ac; i++)
516 return found_principal;
520 skip_space(char **cpp)
524 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
530 * Advanced *cpp past the end of key options, defined as the first unquoted
531 * whitespace character. Returns 0 on success or -1 on failure (e.g.
532 * unterminated quotes).
535 advance_past_options(char **cpp)
540 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
541 if (*cp == '\\' && cp[1] == '"')
542 cp++; /* Skip both */
547 /* return failure for unterminated quotes */
548 return (*cp == '\0' && quoted) ? -1 : 0;
552 * Check a single line of an authorized_keys-format file. Returns 0 if key
553 * matches, -1 otherwise. Will return key/cert options via *authoptsp
554 * on success. "loc" is used as file/line location in log messages.
557 check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
558 char *cp, const char *loc, struct sshauthopt **authoptsp)
560 int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
561 struct sshkey *found = NULL;
562 struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
563 char *key_options = NULL, *fp = NULL;
564 const char *reason = NULL;
567 if (authoptsp != NULL)
570 if ((found = sshkey_new(want_keytype)) == NULL) {
571 debug3("%s: keytype %d failed", __func__, want_keytype);
575 /* XXX djm: peek at key type in line and skip if unwanted */
577 if (sshkey_read(found, &cp) != 0) {
578 /* no key? check for options */
579 debug2("%s: check options: '%s'", loc, cp);
581 if (advance_past_options(&cp) != 0) {
582 reason = "invalid key option string";
586 if (sshkey_read(found, &cp) != 0) {
587 /* still no key? advance to next line*/
588 debug2("%s: advance: '%s'", loc, cp);
592 /* Parse key options now; we need to know if this is a CA key */
593 if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
594 debug("%s: bad key options: %s", loc, reason);
595 auth_debug_add("%s: bad key options: %s", loc, reason);
598 /* Ignore keys that don't match or incorrectly marked as CAs */
599 if (sshkey_is_cert(key)) {
600 /* Certificate; check signature key against CA */
601 if (!sshkey_equal(found, key->cert->signature_key) ||
602 !keyopts->cert_authority)
605 /* Plain key: check it against key found in file */
606 if (!sshkey_equal(found, key) || keyopts->cert_authority)
610 /* We have a candidate key, perform authorisation checks */
611 if ((fp = sshkey_fingerprint(found,
612 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
613 fatal("%s: fingerprint failed", __func__);
615 debug("%s: matching %s found: %s %s", loc,
616 sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
618 if (auth_authorise_keyopts(ssh, pw, keyopts,
619 sshkey_is_cert(key), loc) != 0) {
620 reason = "Refused by key options";
623 /* That's all we need for plain keys. */
624 if (!sshkey_is_cert(key)) {
625 verbose("Accepted key %s %s found at %s",
626 sshkey_type(found), fp, loc);
633 * Additional authorisation for certificates.
636 /* Parse and check options present in certificate */
637 if ((certopts = sshauthopt_from_cert(key)) == NULL) {
638 reason = "Invalid certificate options";
641 if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
642 reason = "Refused by certificate options";
645 if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
649 * If the user has specified a list of principals as
650 * a key option, then prefer that list to matching
651 * their username in the certificate principals list.
653 if (keyopts->cert_principals != NULL &&
654 !match_principals_option(keyopts->cert_principals, key->cert)) {
655 reason = "Certificate does not contain an authorized principal";
658 if (sshkey_cert_check_authority(key, 0, 0,
659 keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
662 verbose("Accepted certificate ID \"%s\" (serial %llu) "
663 "signed by CA %s %s found at %s",
665 (unsigned long long)key->cert->serial,
666 sshkey_type(found), fp, loc);
669 if (finalopts == NULL)
670 fatal("%s: internal error: missing options", __func__);
671 if (authoptsp != NULL) {
672 *authoptsp = finalopts;
681 auth_debug_add("%s", reason);
684 sshauthopt_free(keyopts);
685 sshauthopt_free(certopts);
686 sshauthopt_free(finalopts);
692 * Checks whether key is allowed in authorized_keys-format file,
693 * returns 1 if the key is allowed or 0 otherwise.
696 check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
697 char *file, struct sshkey *key, struct sshauthopt **authoptsp)
699 char *cp, *line = NULL, loc[256];
704 if (authoptsp != NULL)
707 while (getline(&line, &linesize, f) != -1) {
709 /* Always consume entire file */
713 /* Skip leading whitespace, empty and comment lines. */
716 if (!*cp || *cp == '\n' || *cp == '#')
718 snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
719 if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
726 /* Authenticate a certificate key against TrustedUserCAKeys */
728 user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
729 struct sshauthopt **authoptsp)
731 char *ca_fp, *principals_file = NULL;
733 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
734 struct sshauthopt *final_opts = NULL;
735 int r, ret = 0, found_principal = 0, use_authorized_principals;
737 if (authoptsp != NULL)
740 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
743 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
744 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
747 if ((r = sshkey_in_file(key->cert->signature_key,
748 options.trusted_user_ca_keys, 1, 0)) != 0) {
749 debug2("%s: CA %s %s is not listed in %s: %s", __func__,
750 sshkey_type(key->cert->signature_key), ca_fp,
751 options.trusted_user_ca_keys, ssh_err(r));
755 * If AuthorizedPrincipals is in use, then compare the certificate
756 * principals against the names in that file rather than matching
757 * against the username.
759 if ((principals_file = authorized_principals_file(pw)) != NULL) {
760 if (match_principals_file(ssh, pw, principals_file,
761 key->cert, &principals_opts))
764 /* Try querying command if specified */
765 if (!found_principal && match_principals_command(ssh, pw, key,
768 /* If principals file or command is specified, then require a match */
769 use_authorized_principals = principals_file != NULL ||
770 options.authorized_principals_command != NULL;
771 if (!found_principal && use_authorized_principals) {
772 reason = "Certificate does not contain an authorized principal";
775 if (use_authorized_principals && principals_opts == NULL)
776 fatal("%s: internal error: missing principals_opts", __func__);
777 if (sshkey_cert_check_authority(key, 0, 1,
778 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
781 /* Check authority from options in key and from principals file/cmd */
782 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
783 reason = "Invalid certificate options";
786 if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
787 reason = "Refused by certificate options";
790 if (principals_opts == NULL) {
791 final_opts = cert_opts;
794 if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
795 "principals") != 0) {
796 reason = "Refused by certificate principals options";
799 if ((final_opts = sshauthopt_merge(principals_opts,
800 cert_opts, &reason)) == NULL) {
803 auth_debug_add("%s", reason);
809 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
810 "%s CA %s via %s", key->cert->key_id,
811 (unsigned long long)key->cert->serial,
812 sshkey_type(key->cert->signature_key), ca_fp,
813 options.trusted_user_ca_keys);
814 if (authoptsp != NULL) {
815 *authoptsp = final_opts;
820 sshauthopt_free(principals_opts);
821 sshauthopt_free(cert_opts);
822 sshauthopt_free(final_opts);
823 free(principals_file);
829 * Checks whether key is allowed in file.
830 * returns 1 if the key is allowed or 0 otherwise.
833 user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
834 char *file, struct sshauthopt **authoptsp)
839 if (authoptsp != NULL)
842 /* Temporarily use the user's uid. */
843 temporarily_use_uid(pw);
845 debug("trying public key file %s", file);
846 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
847 found_key = check_authkeys_file(ssh, pw, f, file,
857 * Checks whether key is allowed in output of command.
858 * returns 1 if the key is allowed or 0 otherwise.
861 user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
862 struct sshkey *key, struct sshauthopt **authoptsp)
864 struct passwd *runas_pw = NULL;
866 int r, ok, found_key = 0;
867 int i, uid_swapped = 0, ac = 0;
869 char *username = NULL, *key_fp = NULL, *keytext = NULL;
870 char uidstr[32], *tmp, *command = NULL, **av = NULL;
871 void (*osigchld)(int);
873 if (authoptsp != NULL)
875 if (options.authorized_keys_command == NULL)
877 if (options.authorized_keys_command_user == NULL) {
878 error("No user for AuthorizedKeysCommand specified, skipping");
883 * NB. all returns later this function should go via "out" to
884 * ensure the original SIGCHLD handler is restored properly.
886 osigchld = signal(SIGCHLD, SIG_DFL);
888 /* Prepare and verify the user for the command */
889 username = percent_expand(options.authorized_keys_command_user,
890 "u", user_pw->pw_name, (char *)NULL);
891 runas_pw = getpwnam(username);
892 if (runas_pw == NULL) {
893 error("AuthorizedKeysCommandUser \"%s\" not found: %s",
894 username, strerror(errno));
898 /* Prepare AuthorizedKeysCommand */
899 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
900 SSH_FP_DEFAULT)) == NULL) {
901 error("%s: sshkey_fingerprint failed", __func__);
904 if ((r = sshkey_to_base64(key, &keytext)) != 0) {
905 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
909 /* Turn the command into an argument vector */
910 if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
911 error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
916 error("AuthorizedKeysCommand \"%s\" yielded no arguments",
920 snprintf(uidstr, sizeof(uidstr), "%llu",
921 (unsigned long long)user_pw->pw_uid);
922 for (i = 1; i < ac; i++) {
923 tmp = percent_expand(av[i],
925 "u", user_pw->pw_name,
926 "h", user_pw->pw_dir,
927 "t", sshkey_ssh_name(key),
932 fatal("%s: percent_expand failed", __func__);
936 /* Prepare a printable command for logs, etc. */
937 command = argv_assemble(ac, av);
940 * If AuthorizedKeysCommand was run without arguments
941 * then fall back to the old behaviour of passing the
942 * target username as a single argument.
945 av = xreallocarray(av, ac + 2, sizeof(*av));
946 av[1] = xstrdup(user_pw->pw_name);
948 /* Fix up command too, since it is used in log messages */
950 xasprintf(&command, "%s %s", av[0], av[1]);
953 if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
955 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
959 temporarily_use_uid(runas_pw);
961 ok = check_authkeys_file(ssh, user_pw, f,
962 options.authorized_keys_command, key, authoptsp);
967 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
970 /* Read completed successfully */
975 signal(SIGCHLD, osigchld);
976 for (i = 0; i < ac; i++)
989 * Check whether key authenticates and authorises the user.
992 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
993 int auth_attempt, struct sshauthopt **authoptsp)
997 struct sshauthopt *opts = NULL;
998 if (authoptsp != NULL)
1001 if (auth_key_is_revoked(key))
1003 if (sshkey_is_cert(key) &&
1004 auth_key_is_revoked(key->cert->signature_key))
1007 if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
1009 sshauthopt_free(opts);
1012 if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
1014 sshauthopt_free(opts);
1017 for (i = 0; !success && i < options.num_authkeys_files; i++) {
1018 if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
1020 file = expand_authorized_keys(
1021 options.authorized_keys_files[i], pw);
1022 success = user_key_allowed2(ssh, pw, key, file, &opts);
1027 if (success && authoptsp != NULL) {
1031 sshauthopt_free(opts);
1035 Authmethod method_pubkey = {
1038 &options.pubkey_authentication