auth2-pubkey.c revision 1.11 
1/*	$NetBSD: auth2-pubkey.c,v 1.11 2015/04/03 23:58:19 christos Exp $	*/
2/* $OpenBSD: auth2-pubkey.c,v 1.47 2015/02/17 00:14:05 djm Exp $ */
3/*
4 * Copyright (c) 2000 Markus Friedl.  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__RCSID("$NetBSD: auth2-pubkey.c,v 1.11 2015/04/03 23:58:19 christos Exp $");
29#include <sys/types.h>
30#include <sys/stat.h>
31#include <sys/wait.h>
32
33#include <errno.h>
34#include <fcntl.h>
35#include <paths.h>
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 "buffer.h"
50#include "log.h"
51#include "misc.h"
52#include "servconf.h"
53#include "compat.h"
54#include "key.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 "digest.h"
68
69#ifdef WITH_LDAP_PUBKEY
70#include "ldapauth.h"
71#endif
72
73/* import */
74extern ServerOptions options;
75extern u_char *session_id2;
76extern u_int session_id2_len;
77
78static int
79userauth_pubkey(Authctxt *authctxt)
80{
81	Buffer b;
82	Key *key = NULL;
83	char *pkalg, *userstyle;
84	u_char *pkblob, *sig;
85	u_int alen, blen, slen;
86	int have_sig, pktype;
87	int authenticated = 0;
88
89	if (!authctxt->valid) {
90		debug2("userauth_pubkey: disabled because of invalid user");
91		return 0;
92	}
93	have_sig = packet_get_char();
94	if (datafellows & SSH_BUG_PKAUTH) {
95		debug2("userauth_pubkey: SSH_BUG_PKAUTH");
96		/* no explicit pkalg given */
97		pkblob = packet_get_string(&blen);
98		buffer_init(&b);
99		buffer_append(&b, pkblob, blen);
100		/* so we have to extract the pkalg from the pkblob */
101		pkalg = buffer_get_string(&b, &alen);
102		buffer_free(&b);
103	} else {
104		pkalg = packet_get_string(&alen);
105		pkblob = packet_get_string(&blen);
106	}
107	pktype = key_type_from_name(pkalg);
108	if (pktype == KEY_UNSPEC) {
109		/* this is perfectly legal */
110		logit("userauth_pubkey: unsupported public key algorithm: %s",
111		    pkalg);
112		goto done;
113	}
114	key = key_from_blob(pkblob, blen);
115	if (key == NULL) {
116		error("userauth_pubkey: cannot decode key: %s", pkalg);
117		goto done;
118	}
119	if (key->type != pktype) {
120		error("userauth_pubkey: type mismatch for decoded key "
121		    "(received %d, expected %d)", key->type, pktype);
122		goto done;
123	}
124	if (key_type_plain(key->type) == KEY_RSA &&
125	    (datafellows & SSH_BUG_RSASIGMD5) != 0) {
126		logit("Refusing RSA key because client uses unsafe "
127		    "signature scheme");
128		goto done;
129	}
130	if (auth2_userkey_already_used(authctxt, key)) {
131		logit("refusing previously-used %s key", key_type(key));
132		goto done;
133	}
134	if (match_pattern_list(sshkey_ssh_name(key), options.pubkey_key_types,
135	    strlen(options.pubkey_key_types), 0) != 1) {
136		logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
137		    __func__, sshkey_ssh_name(key));
138		goto done;
139	}
140
141	if (have_sig) {
142		sig = packet_get_string(&slen);
143		packet_check_eom();
144		buffer_init(&b);
145		if (datafellows & SSH_OLD_SESSIONID) {
146			buffer_append(&b, session_id2, session_id2_len);
147		} else {
148			buffer_put_string(&b, session_id2, session_id2_len);
149		}
150		/* reconstruct packet */
151		buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
152		xasprintf(&userstyle, "%s%s%s", authctxt->user,
153		    authctxt->style ? ":" : "",
154		    authctxt->style ? authctxt->style : "");
155		buffer_put_cstring(&b, userstyle);
156		free(userstyle);
157		buffer_put_cstring(&b,
158		    datafellows & SSH_BUG_PKSERVICE ?
159		    "ssh-userauth" :
160		    authctxt->service);
161		if (datafellows & SSH_BUG_PKAUTH) {
162			buffer_put_char(&b, have_sig);
163		} else {
164			buffer_put_cstring(&b, "publickey");
165			buffer_put_char(&b, have_sig);
166			buffer_put_cstring(&b, pkalg);
167		}
168		buffer_put_string(&b, pkblob, blen);
169#ifdef DEBUG_PK
170		buffer_dump(&b);
171#endif
172		pubkey_auth_info(authctxt, key, NULL);
173
174		/* test for correct signature */
175		authenticated = 0;
176		if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
177		    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
178		    buffer_len(&b))) == 1) {
179			authenticated = 1;
180			/* Record the successful key to prevent reuse */
181			auth2_record_userkey(authctxt, key);
182			key = NULL; /* Don't free below */
183		}
184		buffer_free(&b);
185		free(sig);
186	} else {
187		debug("test whether pkalg/pkblob are acceptable");
188		packet_check_eom();
189
190		/* XXX fake reply and always send PK_OK ? */
191		/*
192		 * XXX this allows testing whether a user is allowed
193		 * to login: if you happen to have a valid pubkey this
194		 * message is sent. the message is NEVER sent at all
195		 * if a user is not allowed to login. is this an
196		 * issue? -markus
197		 */
198		if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
199			packet_start(SSH2_MSG_USERAUTH_PK_OK);
200			packet_put_string(pkalg, alen);
201			packet_put_string(pkblob, blen);
202			packet_send();
203			packet_write_wait();
204			authctxt->postponed = 1;
205		}
206	}
207	if (authenticated != 1)
208		auth_clear_options();
209done:
210	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
211	if (key != NULL)
212		key_free(key);
213	free(pkalg);
214	free(pkblob);
215	return authenticated;
216}
217
218void
219pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)
220{
221	char *fp, *extra;
222	va_list ap;
223	int i;
224
225	extra = NULL;
226	if (fmt != NULL) {
227		va_start(ap, fmt);
228		i = vasprintf(&extra, fmt, ap);
229		va_end(ap);
230		if (i < 0 || extra == NULL)
231			fatal("%s: vasprintf failed", __func__);
232	}
233
234	if (key_is_cert(key)) {
235		fp = sshkey_fingerprint(key->cert->signature_key,
236		    options.fingerprint_hash, SSH_FP_DEFAULT);
237		auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s",
238		    key_type(key), key->cert->key_id,
239		    (unsigned long long)key->cert->serial,
240		    key_type(key->cert->signature_key),
241		    fp == NULL ? "(null)" : fp,
242		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
243		free(fp);
244	} else {
245		fp = sshkey_fingerprint(key, options.fingerprint_hash,
246		    SSH_FP_DEFAULT);
247		auth_info(authctxt, "%s %s%s%s", key_type(key),
248		    fp == NULL ? "(null)" : fp,
249		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
250		free(fp);
251	}
252	free(extra);
253}
254
255static int
256match_principals_option(const char *principal_list, struct sshkey_cert *cert)
257{
258	char *result;
259	u_int i;
260
261	/* XXX percent_expand() sequences for authorized_principals? */
262
263	for (i = 0; i < cert->nprincipals; i++) {
264		if ((result = match_list(cert->principals[i],
265		    principal_list, NULL)) != NULL) {
266			debug3("matched principal from key options \"%.100s\"",
267			    result);
268			free(result);
269			return 1;
270		}
271	}
272	return 0;
273}
274
275static int
276match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
277{
278	FILE *f;
279	char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
280	u_long linenum = 0;
281	u_int i;
282
283	temporarily_use_uid(pw);
284	debug("trying authorized principals file %s", file);
285	if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
286		restore_uid();
287		return 0;
288	}
289	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
290		/* Skip leading whitespace. */
291		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
292			;
293		/* Skip blank and comment lines. */
294		if ((ep = strchr(cp, '#')) != NULL)
295			*ep = '\0';
296		if (!*cp || *cp == '\n')
297			continue;
298		/* Trim trailing whitespace. */
299		ep = cp + strlen(cp) - 1;
300		while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
301			*ep-- = '\0';
302		/*
303		 * If the line has internal whitespace then assume it has
304		 * key options.
305		 */
306		line_opts = NULL;
307		if ((ep = strrchr(cp, ' ')) != NULL ||
308		    (ep = strrchr(cp, '\t')) != NULL) {
309			for (; *ep == ' ' || *ep == '\t'; ep++)
310				;
311			line_opts = cp;
312			cp = ep;
313		}
314		for (i = 0; i < cert->nprincipals; i++) {
315			if (strcmp(cp, cert->principals[i]) == 0) {
316				debug3("matched principal \"%.100s\" "
317				    "from file \"%s\" on line %lu",
318				    cert->principals[i], file, linenum);
319				if (auth_parse_options(pw, line_opts,
320				    file, linenum) != 1)
321					continue;
322				fclose(f);
323				restore_uid();
324				return 1;
325			}
326		}
327	}
328	fclose(f);
329	restore_uid();
330	return 0;
331}
332
333/*
334 * Checks whether key is allowed in authorized_keys-format file,
335 * returns 1 if the key is allowed or 0 otherwise.
336 */
337static int
338check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
339{
340	char line[SSH_MAX_PUBKEY_BYTES];
341	const char *reason;
342	int found_key = 0;
343	u_long linenum = 0;
344	Key *found;
345	char *fp;
346#ifdef WITH_LDAP_PUBKEY
347	ldap_key_t * k;
348	unsigned int i = 0;
349#endif
350
351#ifdef WITH_LDAP_PUBKEY
352	found_key = 0;
353	/* allocate a new key type */
354	found = key_new(key->type);
355
356	/* first check if the options is enabled, then try.. */
357	if (options.lpk.on) {
358	    debug("[LDAP] trying LDAP first uid=%s",pw->pw_name);
359	    if (ldap_ismember(&options.lpk, pw->pw_name) > 0) {
360		if ((k = ldap_getuserkey(&options.lpk, pw->pw_name)) != NULL) {
361		    /* Skip leading whitespace, empty and comment lines. */
362		    for (i = 0 ; i < k->num ; i++) {
363			/* dont forget if multiple keys to reset options */
364			char *cp, *xoptions = NULL;
365
366			for (cp = (char *)k->keys[i]->bv_val; *cp == ' ' || *cp == '\t'; cp++)
367			    ;
368			if (!*cp || *cp == '\n' || *cp == '#')
369			    continue;
370
371			if (key_read(found, &cp) != 1) {
372			    /* no key?  check if there are options for this key */
373			    int quoted = 0;
374			    debug2("[LDAP] user_key_allowed: check options: '%s'", cp);
375			    xoptions = cp;
376			    for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
377				if (*cp == '\\' && cp[1] == '"')
378				    cp++;	/* Skip both */
379				else if (*cp == '"')
380				    quoted = !quoted;
381			    }
382			    /* Skip remaining whitespace. */
383			    for (; *cp == ' ' || *cp == '\t'; cp++)
384				;
385			    if (key_read(found, &cp) != 1) {
386				debug2("[LDAP] user_key_allowed: advance: '%s'", cp);
387				/* still no key?  advance to next line*/
388				continue;
389			    }
390			}
391
392			if (key_equal(found, key) &&
393				auth_parse_options(pw, xoptions, file, linenum) == 1) {
394			    found_key = 1;
395			    debug("[LDAP] matching key found");
396			    fp = sshkey_fingerprint(found, SSH_FP_HASH_DEFAULT, SSH_FP_HEX);
397			    verbose("[LDAP] Found matching %s key: %s", key_type(found), fp);
398
399			    /* restoring memory */
400			    ldap_keys_free(k);
401			    free(fp);
402			    restore_uid();
403			    key_free(found);
404			    return found_key;
405			    break;
406			}
407		    }/* end of LDAP for() */
408		} else {
409		    logit("[LDAP] no keys found for '%s'!", pw->pw_name);
410		}
411	    } else {
412		logit("[LDAP] '%s' is not in '%s'", pw->pw_name, options.lpk.sgroup);
413	    }
414	}
415#endif
416	debug("trying public key file %s", file);
417	f = auth_openkeyfile(file, pw, options.strict_modes);
418
419	if (!f) {
420		restore_uid();
421		return 0;
422	}
423
424	found_key = 0;
425
426	found = NULL;
427	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
428		char *cp, *key_options = NULL;
429		if (found != NULL)
430			key_free(found);
431		found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
432		auth_clear_options();
433
434		/* Skip leading whitespace, empty and comment lines. */
435		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
436			;
437		if (!*cp || *cp == '\n' || *cp == '#')
438			continue;
439
440		if (key_read(found, &cp) != 1) {
441			/* no key?  check if there are options for this key */
442			int quoted = 0;
443			debug2("user_key_allowed: check options: '%s'", cp);
444			key_options = cp;
445			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
446				if (*cp == '\\' && cp[1] == '"')
447					cp++;	/* Skip both */
448				else if (*cp == '"')
449					quoted = !quoted;
450			}
451			/* Skip remaining whitespace. */
452			for (; *cp == ' ' || *cp == '\t'; cp++)
453				;
454			if (key_read(found, &cp) != 1) {
455				debug2("user_key_allowed: advance: '%s'", cp);
456				/* still no key?  advance to next line*/
457				continue;
458			}
459		}
460		if (key_is_cert(key)) {
461			if (!key_equal(found, key->cert->signature_key))
462				continue;
463			if (auth_parse_options(pw, key_options, file,
464			    linenum) != 1)
465				continue;
466			if (!key_is_cert_authority)
467				continue;
468			if ((fp = sshkey_fingerprint(found,
469			    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
470				continue;
471			debug("matching CA found: file %s, line %lu, %s %s",
472			    file, linenum, key_type(found), fp);
473			/*
474			 * If the user has specified a list of principals as
475			 * a key option, then prefer that list to matching
476			 * their username in the certificate principals list.
477			 */
478			if (authorized_principals != NULL &&
479			    !match_principals_option(authorized_principals,
480			    key->cert)) {
481				reason = "Certificate does not contain an "
482				    "authorized principal";
483 fail_reason:
484				free(fp);
485				error("%s", reason);
486				auth_debug_add("%s", reason);
487				continue;
488			}
489			if (key_cert_check_authority(key, 0, 0,
490			    authorized_principals == NULL ? pw->pw_name : NULL,
491			    &reason) != 0)
492				goto fail_reason;
493			if (auth_cert_options(key, pw) != 0) {
494				free(fp);
495				continue;
496			}
497			verbose("Accepted certificate ID \"%s\" "
498			    "signed by %s CA %s via %s", key->cert->key_id,
499			    key_type(found), fp, file);
500			free(fp);
501			found_key = 1;
502			break;
503		} else if (key_equal(found, key)) {
504			if (auth_parse_options(pw, key_options, file,
505			    linenum) != 1)
506				continue;
507			if (key_is_cert_authority)
508				continue;
509			if ((fp = sshkey_fingerprint(found,
510			    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
511				continue;
512			debug("matching key found: file %s, line %lu %s %s",
513			    file, linenum, key_type(found), fp);
514			free(fp);
515			found_key = 1;
516			break;
517		}
518	}
519	if (found != NULL)
520		key_free(found);
521	if (!found_key)
522		debug2("key not found");
523	return found_key;
524}
525
526/* Authenticate a certificate key against TrustedUserCAKeys */
527static int
528user_cert_trusted_ca(struct passwd *pw, Key *key)
529{
530	char *ca_fp, *principals_file = NULL;
531	const char *reason;
532	int ret = 0;
533
534	if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
535		return 0;
536
537	if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
538	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
539		return 0;
540
541	if (sshkey_in_file(key->cert->signature_key,
542	    options.trusted_user_ca_keys, 1, 0) != 0) {
543		debug2("%s: CA %s %s is not listed in %s", __func__,
544		    key_type(key->cert->signature_key), ca_fp,
545		    options.trusted_user_ca_keys);
546		goto out;
547	}
548	/*
549	 * If AuthorizedPrincipals is in use, then compare the certificate
550	 * principals against the names in that file rather than matching
551	 * against the username.
552	 */
553	if ((principals_file = authorized_principals_file(pw)) != NULL) {
554		if (!match_principals_file(principals_file, pw, key->cert)) {
555			reason = "Certificate does not contain an "
556			    "authorized principal";
557 fail_reason:
558			error("%s", reason);
559			auth_debug_add("%s", reason);
560			goto out;
561		}
562	}
563	if (key_cert_check_authority(key, 0, 1,
564	    principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
565		goto fail_reason;
566	if (auth_cert_options(key, pw) != 0)
567		goto out;
568
569	verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
570	    key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
571	    options.trusted_user_ca_keys);
572	ret = 1;
573
574 out:
575	free(principals_file);
576	free(ca_fp);
577	return ret;
578}
579
580/*
581 * Checks whether key is allowed in file.
582 * returns 1 if the key is allowed or 0 otherwise.
583 */
584static int
585user_key_allowed2(struct passwd *pw, Key *key, char *file)
586{
587	FILE *f;
588	int found_key = 0;
589
590	/* Temporarily use the user's uid. */
591	temporarily_use_uid(pw);
592
593	debug("trying public key file %s", file);
594	if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
595		found_key = check_authkeys_file(f, file, key, pw);
596		fclose(f);
597	}
598
599	restore_uid();
600	return found_key;
601}
602
603/*
604 * Checks whether key is allowed in output of command.
605 * returns 1 if the key is allowed or 0 otherwise.
606 */
607static int
608user_key_command_allowed2(struct passwd *user_pw, Key *key)
609{
610	FILE *f;
611	int ok, found_key = 0;
612	struct passwd *pw;
613	struct stat st;
614	int status, devnull, p[2], i;
615	pid_t pid;
616	char *username, errmsg[512];
617
618	if (options.authorized_keys_command == NULL ||
619	    options.authorized_keys_command[0] != '/')
620		return 0;
621
622	if (options.authorized_keys_command_user == NULL) {
623		error("No user for AuthorizedKeysCommand specified, skipping");
624		return 0;
625	}
626
627	username = percent_expand(options.authorized_keys_command_user,
628	    "u", user_pw->pw_name, (char *)NULL);
629	pw = getpwnam(username);
630	if (pw == NULL) {
631		error("AuthorizedKeysCommandUser \"%s\" not found: %s",
632		    username, strerror(errno));
633		free(username);
634		return 0;
635	}
636	free(username);
637
638	temporarily_use_uid(pw);
639
640	if (stat(options.authorized_keys_command, &st) < 0) {
641		error("Could not stat AuthorizedKeysCommand \"%s\": %s",
642		    options.authorized_keys_command, strerror(errno));
643		goto out;
644	}
645	if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
646	    errmsg, sizeof(errmsg)) != 0) {
647		error("Unsafe AuthorizedKeysCommand: %s", errmsg);
648		goto out;
649	}
650
651	if (pipe(p) != 0) {
652		error("%s: pipe: %s", __func__, strerror(errno));
653		goto out;
654	}
655
656	debug3("Running AuthorizedKeysCommand: \"%s %s\" as \"%s\"",
657	    options.authorized_keys_command, user_pw->pw_name, pw->pw_name);
658
659	/*
660	 * Don't want to call this in the child, where it can fatal() and
661	 * run cleanup_exit() code.
662	 */
663	restore_uid();
664
665	switch ((pid = fork())) {
666	case -1: /* error */
667		error("%s: fork: %s", __func__, strerror(errno));
668		close(p[0]);
669		close(p[1]);
670		return 0;
671	case 0: /* child */
672		for (i = 0; i < NSIG; i++)
673			signal(i, SIG_DFL);
674
675		if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
676			error("%s: open %s: %s", __func__, _PATH_DEVNULL,
677			    strerror(errno));
678			_exit(1);
679		}
680		/* Keep stderr around a while longer to catch errors */
681		if (dup2(devnull, STDIN_FILENO) == -1 ||
682		    dup2(p[1], STDOUT_FILENO) == -1) {
683			error("%s: dup2: %s", __func__, strerror(errno));
684			_exit(1);
685		}
686		closefrom(STDERR_FILENO + 1);
687
688		/* Don't use permanently_set_uid() here to avoid fatal() */
689		if (setgid(pw->pw_gid) != 0) {
690			error("setgid %u: %s", (u_int)pw->pw_gid,
691			    strerror(errno));
692			_exit(1);
693		}
694		if (setuid(pw->pw_uid) != 0) {
695			error("setuid %u: %s", (u_int)pw->pw_uid,
696			    strerror(errno));
697			_exit(1);
698		}
699		/* stdin is pointed to /dev/null at this point */
700		if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
701			error("%s: dup2: %s", __func__, strerror(errno));
702			_exit(1);
703		}
704
705		execl(options.authorized_keys_command,
706		    options.authorized_keys_command, user_pw->pw_name, NULL);
707
708		error("AuthorizedKeysCommand %s exec failed: %s",
709		    options.authorized_keys_command, strerror(errno));
710		_exit(127);
711	default: /* parent */
712		break;
713	}
714
715	temporarily_use_uid(pw);
716
717	close(p[1]);
718	if ((f = fdopen(p[0], "r")) == NULL) {
719		error("%s: fdopen: %s", __func__, strerror(errno));
720		close(p[0]);
721		/* Don't leave zombie child */
722		kill(pid, SIGTERM);
723		while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
724			;
725		goto out;
726	}
727	ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
728	fclose(f);
729
730	while (waitpid(pid, &status, 0) == -1) {
731		if (errno != EINTR) {
732			error("%s: waitpid: %s", __func__, strerror(errno));
733			goto out;
734		}
735	}
736	if (WIFSIGNALED(status)) {
737		error("AuthorizedKeysCommand %s exited on signal %d",
738		    options.authorized_keys_command, WTERMSIG(status));
739		goto out;
740	} else if (WEXITSTATUS(status) != 0) {
741		error("AuthorizedKeysCommand %s returned status %d",
742		    options.authorized_keys_command, WEXITSTATUS(status));
743		goto out;
744	}
745	found_key = ok;
746 out:
747	restore_uid();
748	return found_key;
749}
750
751/*
752 * Check whether key authenticates and authorises the user.
753 */
754int
755user_key_allowed(struct passwd *pw, Key *key)
756{
757	u_int success, i;
758	char *file;
759
760	if (auth_key_is_revoked(key))
761		return 0;
762	if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
763		return 0;
764
765	success = user_cert_trusted_ca(pw, key);
766	if (success)
767		return success;
768
769	success = user_key_command_allowed2(pw, key);
770	if (success > 0)
771		return success;
772
773	for (i = 0; !success && i < options.num_authkeys_files; i++) {
774
775		if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
776			continue;
777		file = expand_authorized_keys(
778		    options.authorized_keys_files[i], pw);
779
780		success = user_key_allowed2(pw, key, file);
781		free(file);
782	}
783
784	return success;
785}
786
787/* Records a public key in the list of previously-successful keys */
788void
789auth2_record_userkey(Authctxt *authctxt, struct sshkey *key)
790{
791	struct sshkey **tmp;
792
793	if (authctxt->nprev_userkeys >= INT_MAX ||
794	    (tmp = reallocarray(authctxt->prev_userkeys,
795	    authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL)
796		fatal("%s: reallocarray failed", __func__);
797	authctxt->prev_userkeys = tmp;
798	authctxt->prev_userkeys[authctxt->nprev_userkeys] = key;
799	authctxt->nprev_userkeys++;
800}
801
802/* Checks whether a key has already been used successfully for authentication */
803int
804auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key)
805{
806	u_int i;
807
808	for (i = 0; i < authctxt->nprev_userkeys; i++) {
809		if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
810			return 1;
811		}
812	}
813	return 0;
814}
815
816Authmethod method_pubkey = {
817	"publickey",
818	userauth_pubkey,
819	&options.pubkey_authentication
820};
821