[openssh.git] / auth2-pubkey.c

/* $OpenBSD: auth2-pubkey.c,v 1.15 2006/08/03 03:34:41 deraadt Exp $ */
/*
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#include <sys/types.h>
#include <sys/stat.h>

#include <pwd.h>
#include <stdio.h>
#include <stdarg.h>

#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "servconf.h"
#include "compat.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "pathnames.h"
#include "uidswap.h"
#include "auth-options.h"
#include "canohost.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "misc.h"

/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern u_int session_id2_len;

static int
userauth_pubkey(Authctxt *authctxt)
{
	Buffer b;
	Key *key = NULL;
	char *pkalg;
	u_char *pkblob, *sig;
	u_int alen, blen, slen;
	int have_sig, pktype;
	int authenticated = 0;

	if (!authctxt->valid) {
		debug2("userauth_pubkey: disabled because of invalid user");
		return 0;
	}
	have_sig = packet_get_char();
	if (datafellows & SSH_BUG_PKAUTH) {
		debug2("userauth_pubkey: SSH_BUG_PKAUTH");
		/* no explicit pkalg given */
		pkblob = packet_get_string(&blen);
		buffer_init(&b);
		buffer_append(&b, pkblob, blen);
		/* so we have to extract the pkalg from the pkblob */
		pkalg = buffer_get_string(&b, &alen);
		buffer_free(&b);
	} else {
		pkalg = packet_get_string(&alen);
		pkblob = packet_get_string(&blen);
	}
	pktype = key_type_from_name(pkalg);
	if (pktype == KEY_UNSPEC) {
		/* this is perfectly legal */
		logit("userauth_pubkey: unsupported public key algorithm: %s",
		    pkalg);
		goto done;
	}
	key = key_from_blob(pkblob, blen);
	if (key == NULL) {
		error("userauth_pubkey: cannot decode key: %s", pkalg);
		goto done;
	}
	if (key->type != pktype) {
		error("userauth_pubkey: type mismatch for decoded key "
		    "(received %d, expected %d)", key->type, pktype);
		goto done;
	}
	if (have_sig) {
		sig = packet_get_string(&slen);
		packet_check_eom();
		buffer_init(&b);
		if (datafellows & SSH_OLD_SESSIONID) {
			buffer_append(&b, session_id2, session_id2_len);
		} else {
			buffer_put_string(&b, session_id2, session_id2_len);
		}
		/* reconstruct packet */
		buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
		buffer_put_cstring(&b, authctxt->user);
		buffer_put_cstring(&b,
		    datafellows & SSH_BUG_PKSERVICE ?
		    "ssh-userauth" :
		    authctxt->service);
		if (datafellows & SSH_BUG_PKAUTH) {
			buffer_put_char(&b, have_sig);
		} else {
			buffer_put_cstring(&b, "publickey");
			buffer_put_char(&b, have_sig);
			buffer_put_cstring(&b, pkalg);
		}
		buffer_put_string(&b, pkblob, blen);
#ifdef DEBUG_PK
		buffer_dump(&b);
#endif
		/* test for correct signature */
		authenticated = 0;
		if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
		    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
		    buffer_len(&b))) == 1)
			authenticated = 1;
		buffer_free(&b);
		xfree(sig);
	} else {
		debug("test whether pkalg/pkblob are acceptable");
		packet_check_eom();

		/* XXX fake reply and always send PK_OK ? */
		/*
		 * XXX this allows testing whether a user is allowed
		 * to login: if you happen to have a valid pubkey this
		 * message is sent. the message is NEVER sent at all
		 * if a user is not allowed to login. is this an
		 * issue? -markus
		 */
		if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
			packet_start(SSH2_MSG_USERAUTH_PK_OK);
			packet_put_string(pkalg, alen);
			packet_put_string(pkblob, blen);
			packet_send();
			packet_write_wait();
			authctxt->postponed = 1;
		}
	}
	if (authenticated != 1)
		auth_clear_options();
done:
	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	if (key != NULL)
		key_free(key);
	xfree(pkalg);
	xfree(pkblob);
#ifdef HAVE_CYGWIN
	if (check_nt_auth(0, authctxt->pw) == 0)
		authenticated = 0;
#endif
	return authenticated;
}

/* return 1 if user allows given key */
static int
user_key_allowed2(struct passwd *pw, Key *key, char *file)
{
	char line[SSH_MAX_PUBKEY_BYTES];
	int found_key = 0;
	FILE *f;
	u_long linenum = 0;
	struct stat st;
	Key *found;
	char *fp;

	/* Temporarily use the user's uid. */
	temporarily_use_uid(pw);

	debug("trying public key file %s", file);

	/* Fail quietly if file does not exist */
	if (stat(file, &st) < 0) {
		/* Restore the privileged uid. */
		restore_uid();
		return 0;
	}
	/* Open the file containing the authorized keys. */
	f = fopen(file, "r");
	if (!f) {
		/* Restore the privileged uid. */
		restore_uid();
		return 0;
	}
	if (options.strict_modes &&
	    secure_filename(f, file, pw, line, sizeof(line)) != 0) {
		fclose(f);
		logit("Authentication refused: %s", line);
		restore_uid();
		return 0;
	}

	found_key = 0;
	found = key_new(key->type);

	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
		char *cp, *key_options = NULL;

		/* Skip leading whitespace, empty and comment lines. */
		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
			;
		if (!*cp || *cp == '\n' || *cp == '#')
			continue;

		if (key_read(found, &cp) != 1) {
			/* no key?  check if there are options for this key */
			int quoted = 0;
			debug2("user_key_allowed: check options: '%s'", cp);
			key_options = cp;
			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
				if (*cp == '\\' && cp[1] == '"')
					cp++;	/* Skip both */
				else if (*cp == '"')
					quoted = !quoted;
			}
			/* Skip remaining whitespace. */
			for (; *cp == ' ' || *cp == '\t'; cp++)
				;
			if (key_read(found, &cp) != 1) {
				debug2("user_key_allowed: advance: '%s'", cp);
				/* still no key?  advance to next line*/
				continue;
			}
		}
		if (key_equal(found, key) &&
		    auth_parse_options(pw, key_options, file, linenum) == 1) {
			found_key = 1;
			debug("matching key found: file %s, line %lu",
			    file, linenum);
			fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
			verbose("Found matching %s key: %s",
			    key_type(found), fp);
			xfree(fp);
			break;
		}
	}
	restore_uid();
	fclose(f);
	key_free(found);
	if (!found_key)
		debug2("key not found");
	return found_key;
}

/* check whether given key is in .ssh/authorized_keys* */
int
user_key_allowed(struct passwd *pw, Key *key)
{
	int success;
	char *file;

	file = authorized_keys_file(pw);
	success = user_key_allowed2(pw, key, file);
	xfree(file);
	if (success)
		return success;

	/* try suffix "2" for backward compat, too */
	file = authorized_keys_file2(pw);
	success = user_key_allowed2(pw, key, file);
	xfree(file);
	return success;
}

Authmethod method_pubkey = {
	"publickey",
	userauth_pubkey,
	&options.pubkey_authentication
};
Commit	Line	Data
31652869	1	/* $OpenBSD: auth2-pubkey.c,v 1.15 2006/08/03 03:34:41 deraadt Exp $ */
013eab17	2	/*
	3	* Copyright (c) 2000 Markus Friedl. All rights reserved.
	4	*
	5	* Redistribution and use in source and binary forms, with or without
	6	* modification, are permitted provided that the following conditions
	7	* are met:
	8	* 1. Redistributions of source code must retain the above copyright
	9	* notice, this list of conditions and the following disclaimer.
	10	* 2. Redistributions in binary form must reproduce the above copyright
	11	* notice, this list of conditions and the following disclaimer in the
	12	* documentation and/or other materials provided with the distribution.
	13	*
	14	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	17	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	24	*/
	25
	26	#include "includes.h"
4095f623	27
	28	#include <sys/types.h>
	29	#include <sys/stat.h>
013eab17	30
b1842393	31	#include <pwd.h>
cf851879	32	#include <stdio.h>
31652869	33	#include <stdarg.h>
b1842393	34
31652869	35	#include "xmalloc.h"
ea067773	36	#include "ssh.h"
013eab17	37	#include "ssh2.h"
013eab17	38	#include "packet.h"
	39	#include "buffer.h"
	40	#include "log.h"
	41	#include "servconf.h"
	42	#include "compat.h"
013eab17	43	#include "key.h"
31652869	44	#include "hostfile.h"
31652869	45	#include "auth.h"
013eab17	46	#include "pathnames.h"
	47	#include "uidswap.h"
	48	#include "auth-options.h"
	49	#include "canohost.h"
31652869	50	#ifdef GSSAPI
	51	#include "ssh-gss.h"
	52	#endif
013eab17	53	#include "monitor_wrap.h"
41feb690	54	#include "misc.h"
013eab17	55
	56	/* import */
	57	extern ServerOptions options;
	58	extern u_char *session_id2;
a27002e5	59	extern u_int session_id2_len;
013eab17	60
	61	static int
	62	userauth_pubkey(Authctxt *authctxt)
	63	{
	64	Buffer b;
	65	Key *key = NULL;
	66	char *pkalg;
	67	u_char pkblob, sig;
	68	u_int alen, blen, slen;
	69	int have_sig, pktype;
	70	int authenticated = 0;
	71
	72	if (!authctxt->valid) {
	73	debug2("userauth_pubkey: disabled because of invalid user");
	74	return 0;
	75	}
	76	have_sig = packet_get_char();
	77	if (datafellows & SSH_BUG_PKAUTH) {
	78	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	79	/* no explicit pkalg given */
	80	pkblob = packet_get_string(&blen);
	81	buffer_init(&b);
	82	buffer_append(&b, pkblob, blen);
	83	/* so we have to extract the pkalg from the pkblob */
	84	pkalg = buffer_get_string(&b, &alen);
	85	buffer_free(&b);
	86	} else {
	87	pkalg = packet_get_string(&alen);
	88	pkblob = packet_get_string(&blen);
	89	}
	90	pktype = key_type_from_name(pkalg);
	91	if (pktype == KEY_UNSPEC) {
	92	/* this is perfectly legal */
bbe88b6d	93	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	94	pkalg);
	95	goto done;
	96	}
	97	key = key_from_blob(pkblob, blen);
	98	if (key == NULL) {
	99	error("userauth_pubkey: cannot decode key: %s", pkalg);
	100	goto done;
	101	}
	102	if (key->type != pktype) {
	103	error("userauth_pubkey: type mismatch for decoded key "
	104	"(received %d, expected %d)", key->type, pktype);
	105	goto done;
	106	}
	107	if (have_sig) {
	108	sig = packet_get_string(&slen);
	109	packet_check_eom();
	110	buffer_init(&b);
	111	if (datafellows & SSH_OLD_SESSIONID) {
	112	buffer_append(&b, session_id2, session_id2_len);
	113	} else {
	114	buffer_put_string(&b, session_id2, session_id2_len);
	115	}
	116	/* reconstruct packet */
	117	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	118	buffer_put_cstring(&b, authctxt->user);
	119	buffer_put_cstring(&b,
	120	datafellows & SSH_BUG_PKSERVICE ?
	121	"ssh-userauth" :
	122	authctxt->service);
	123	if (datafellows & SSH_BUG_PKAUTH) {
	124	buffer_put_char(&b, have_sig);
	125	} else {
	126	buffer_put_cstring(&b, "publickey");
	127	buffer_put_char(&b, have_sig);
	128	buffer_put_cstring(&b, pkalg);
	129	}
	130	buffer_put_string(&b, pkblob, blen);
	131	#ifdef DEBUG_PK
	132	buffer_dump(&b);
	133	#endif
	134	/* test for correct signature */
	135	authenticated = 0;
	136	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	137	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	138	buffer_len(&b))) == 1)
013eab17	139	authenticated = 1;
43f7a4b8	140	buffer_free(&b);
013eab17	141	xfree(sig);
	142	} else {
	143	debug("test whether pkalg/pkblob are acceptable");
	144	packet_check_eom();
	145
	146	/* XXX fake reply and always send PK_OK ? */
	147	/*
	148	* XXX this allows testing whether a user is allowed
	149	* to login: if you happen to have a valid pubkey this
	150	* message is sent. the message is NEVER sent at all
	151	* if a user is not allowed to login. is this an
	152	* issue? -markus
	153	*/
	154	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	155	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	156	packet_put_string(pkalg, alen);
	157	packet_put_string(pkblob, blen);
	158	packet_send();
	159	packet_write_wait();
	160	authctxt->postponed = 1;
	161	}
	162	}
	163	if (authenticated != 1)
	164	auth_clear_options();
	165	done:
	166	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	167	if (key != NULL)
	168	key_free(key);
	169	xfree(pkalg);
	170	xfree(pkblob);
	171	#ifdef HAVE_CYGWIN
	172	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	173	authenticated = 0;
013eab17	174	#endif
	175	return authenticated;
	176	}
	177
	178	/* return 1 if user allows given key */
	179	static int
	180	user_key_allowed2(struct passwd pw, Key key, char *file)
	181	{
ea067773	182	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	183	int found_key = 0;
	184	FILE *f;
	185	u_long linenum = 0;
	186	struct stat st;
	187	Key *found;
	188	char *fp;
	189
013eab17	190	/* Temporarily use the user's uid. */
	191	temporarily_use_uid(pw);
	192
	193	debug("trying public key file %s", file);
	194
	195	/* Fail quietly if file does not exist */
	196	if (stat(file, &st) < 0) {
	197	/* Restore the privileged uid. */
	198	restore_uid();
	199	return 0;
	200	}
	201	/* Open the file containing the authorized keys. */
	202	f = fopen(file, "r");
	203	if (!f) {
	204	/* Restore the privileged uid. */
	205	restore_uid();
	206	return 0;
	207	}
	208	if (options.strict_modes &&
	209	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	210	fclose(f);
bbe88b6d	211	logit("Authentication refused: %s", line);
013eab17	212	restore_uid();
	213	return 0;
	214	}
	215
	216	found_key = 0;
	217	found = key_new(key->type);
	218
ea067773	219	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	220	char cp, key_options = NULL;
ea067773	221
013eab17	222	/* Skip leading whitespace, empty and comment lines. */
	223	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	224	;
	225	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	226	continue;
	227
	228	if (key_read(found, &cp) != 1) {
	229	/* no key? check if there are options for this key */
	230	int quoted = 0;
	231	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	232	key_options = cp;
013eab17	233	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	234	if (*cp == '\\' && cp[1] == '"')
	235	cp++; /* Skip both */
	236	else if (*cp == '"')
	237	quoted = !quoted;
	238	}
	239	/* Skip remaining whitespace. */
	240	for (; cp == ' ' \|\| cp == '\t'; cp++)
	241	;
	242	if (key_read(found, &cp) != 1) {
	243	debug2("user_key_allowed: advance: '%s'", cp);
	244	/* still no key? advance to next line*/
	245	continue;
	246	}
	247	}
	248	if (key_equal(found, key) &&
ca75d7de	249	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	250	found_key = 1;
	251	debug("matching key found: file %s, line %lu",
	252	file, linenum);
	253	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	254	verbose("Found matching %s key: %s",
	255	key_type(found), fp);
	256	xfree(fp);
	257	break;
	258	}
	259	}
	260	restore_uid();
	261	fclose(f);
	262	key_free(found);
	263	if (!found_key)
	264	debug2("key not found");
	265	return found_key;
	266	}
	267
	268	/* check whether given key is in .ssh/authorized_keys* */
	269	int
	270	user_key_allowed(struct passwd pw, Key key)
	271	{
	272	int success;
	273	char *file;
	274
	275	file = authorized_keys_file(pw);
	276	success = user_key_allowed2(pw, key, file);
	277	xfree(file);
	278	if (success)
	279	return success;
	280
	281	/* try suffix "2" for backward compat, too */
	282	file = authorized_keys_file2(pw);
	283	success = user_key_allowed2(pw, key, file);
	284	xfree(file);
	285	return success;
	286	}
	287
	288	Authmethod method_pubkey = {
	289	"publickey",
	290	userauth_pubkey,
	291	&options.pubkey_authentication
	292	};