[openssh.git] / auth2-pubkey.c

/*
 * 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"
RCSID("$OpenBSD: auth2-pubkey.c,v 1.9 2004/12/11 01:48:56 dtucker Exp $");

#include "ssh.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "servconf.h"
#include "compat.h"
#include "bufaux.h"
#include "auth.h"
#include "key.h"
#include "pathnames.h"
#include "uidswap.h"
#include "auth-options.h"
#include "canohost.h"
#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
013eab17	1	/*
	2	* Copyright (c) 2000 Markus Friedl. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	7	* 1. Redistributions of source code must retain the above copyright
	8	* notice, this list of conditions and the following disclaimer.
	9	* 2. Redistributions in binary form must reproduce the above copyright
	10	* notice, this list of conditions and the following disclaimer in the
	11	* documentation and/or other materials provided with the distribution.
	12	*
	13	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	14	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	15	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	16	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	17	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	18	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	19	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	20	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	21	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	22	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	23	*/
	24
	25	#include "includes.h"
41feb690	26	RCSID("$OpenBSD: auth2-pubkey.c,v 1.9 2004/12/11 01:48:56 dtucker Exp $");
013eab17	27
ea067773	28	#include "ssh.h"
013eab17	29	#include "ssh2.h"
	30	#include "xmalloc.h"
	31	#include "packet.h"
	32	#include "buffer.h"
	33	#include "log.h"
	34	#include "servconf.h"
	35	#include "compat.h"
	36	#include "bufaux.h"
	37	#include "auth.h"
	38	#include "key.h"
	39	#include "pathnames.h"
	40	#include "uidswap.h"
	41	#include "auth-options.h"
	42	#include "canohost.h"
	43	#include "monitor_wrap.h"
41feb690	44	#include "misc.h"
013eab17	45
	46	/* import */
	47	extern ServerOptions options;
	48	extern u_char *session_id2;
a27002e5	49	extern u_int session_id2_len;
013eab17	50
	51	static int
	52	userauth_pubkey(Authctxt *authctxt)
	53	{
	54	Buffer b;
	55	Key *key = NULL;
	56	char *pkalg;
	57	u_char pkblob, sig;
	58	u_int alen, blen, slen;
	59	int have_sig, pktype;
	60	int authenticated = 0;
	61
	62	if (!authctxt->valid) {
	63	debug2("userauth_pubkey: disabled because of invalid user");
	64	return 0;
	65	}
	66	have_sig = packet_get_char();
	67	if (datafellows & SSH_BUG_PKAUTH) {
	68	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	69	/* no explicit pkalg given */
	70	pkblob = packet_get_string(&blen);
	71	buffer_init(&b);
	72	buffer_append(&b, pkblob, blen);
	73	/* so we have to extract the pkalg from the pkblob */
	74	pkalg = buffer_get_string(&b, &alen);
	75	buffer_free(&b);
	76	} else {
	77	pkalg = packet_get_string(&alen);
	78	pkblob = packet_get_string(&blen);
	79	}
	80	pktype = key_type_from_name(pkalg);
	81	if (pktype == KEY_UNSPEC) {
	82	/* this is perfectly legal */
bbe88b6d	83	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	84	pkalg);
	85	goto done;
	86	}
	87	key = key_from_blob(pkblob, blen);
	88	if (key == NULL) {
	89	error("userauth_pubkey: cannot decode key: %s", pkalg);
	90	goto done;
	91	}
	92	if (key->type != pktype) {
	93	error("userauth_pubkey: type mismatch for decoded key "
	94	"(received %d, expected %d)", key->type, pktype);
	95	goto done;
	96	}
	97	if (have_sig) {
	98	sig = packet_get_string(&slen);
	99	packet_check_eom();
	100	buffer_init(&b);
	101	if (datafellows & SSH_OLD_SESSIONID) {
	102	buffer_append(&b, session_id2, session_id2_len);
	103	} else {
	104	buffer_put_string(&b, session_id2, session_id2_len);
	105	}
	106	/* reconstruct packet */
	107	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	108	buffer_put_cstring(&b, authctxt->user);
	109	buffer_put_cstring(&b,
	110	datafellows & SSH_BUG_PKSERVICE ?
	111	"ssh-userauth" :
	112	authctxt->service);
	113	if (datafellows & SSH_BUG_PKAUTH) {
	114	buffer_put_char(&b, have_sig);
	115	} else {
	116	buffer_put_cstring(&b, "publickey");
	117	buffer_put_char(&b, have_sig);
	118	buffer_put_cstring(&b, pkalg);
	119	}
	120	buffer_put_string(&b, pkblob, blen);
	121	#ifdef DEBUG_PK
	122	buffer_dump(&b);
	123	#endif
	124	/* test for correct signature */
	125	authenticated = 0;
	126	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	127	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	128	buffer_len(&b))) == 1)
013eab17	129	authenticated = 1;
43f7a4b8	130	buffer_free(&b);
013eab17	131	xfree(sig);
	132	} else {
	133	debug("test whether pkalg/pkblob are acceptable");
	134	packet_check_eom();
	135
	136	/* XXX fake reply and always send PK_OK ? */
	137	/*
	138	* XXX this allows testing whether a user is allowed
	139	* to login: if you happen to have a valid pubkey this
	140	* message is sent. the message is NEVER sent at all
	141	* if a user is not allowed to login. is this an
	142	* issue? -markus
	143	*/
	144	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	145	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	146	packet_put_string(pkalg, alen);
	147	packet_put_string(pkblob, blen);
	148	packet_send();
	149	packet_write_wait();
	150	authctxt->postponed = 1;
	151	}
	152	}
	153	if (authenticated != 1)
	154	auth_clear_options();
	155	done:
	156	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	157	if (key != NULL)
	158	key_free(key);
	159	xfree(pkalg);
	160	xfree(pkblob);
	161	#ifdef HAVE_CYGWIN
	162	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	163	authenticated = 0;
013eab17	164	#endif
	165	return authenticated;
	166	}
	167
	168	/* return 1 if user allows given key */
	169	static int
	170	user_key_allowed2(struct passwd pw, Key key, char *file)
	171	{
ea067773	172	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	173	int found_key = 0;
	174	FILE *f;
	175	u_long linenum = 0;
	176	struct stat st;
	177	Key *found;
	178	char *fp;
	179
013eab17	180	/* Temporarily use the user's uid. */
	181	temporarily_use_uid(pw);
	182
	183	debug("trying public key file %s", file);
	184
	185	/* Fail quietly if file does not exist */
	186	if (stat(file, &st) < 0) {
	187	/* Restore the privileged uid. */
	188	restore_uid();
	189	return 0;
	190	}
	191	/* Open the file containing the authorized keys. */
	192	f = fopen(file, "r");
	193	if (!f) {
	194	/* Restore the privileged uid. */
	195	restore_uid();
	196	return 0;
	197	}
	198	if (options.strict_modes &&
	199	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	200	fclose(f);
bbe88b6d	201	logit("Authentication refused: %s", line);
013eab17	202	restore_uid();
	203	return 0;
	204	}
	205
	206	found_key = 0;
	207	found = key_new(key->type);
	208
ea067773	209	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	210	char cp, key_options = NULL;
ea067773	211
013eab17	212	/* Skip leading whitespace, empty and comment lines. */
	213	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	214	;
	215	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	216	continue;
	217
	218	if (key_read(found, &cp) != 1) {
	219	/* no key? check if there are options for this key */
	220	int quoted = 0;
	221	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	222	key_options = cp;
013eab17	223	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	224	if (*cp == '\\' && cp[1] == '"')
	225	cp++; /* Skip both */
	226	else if (*cp == '"')
	227	quoted = !quoted;
	228	}
	229	/* Skip remaining whitespace. */
	230	for (; cp == ' ' \|\| cp == '\t'; cp++)
	231	;
	232	if (key_read(found, &cp) != 1) {
	233	debug2("user_key_allowed: advance: '%s'", cp);
	234	/* still no key? advance to next line*/
	235	continue;
	236	}
	237	}
	238	if (key_equal(found, key) &&
ca75d7de	239	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	240	found_key = 1;
	241	debug("matching key found: file %s, line %lu",
	242	file, linenum);
	243	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	244	verbose("Found matching %s key: %s",
	245	key_type(found), fp);
	246	xfree(fp);
	247	break;
	248	}
	249	}
	250	restore_uid();
	251	fclose(f);
	252	key_free(found);
	253	if (!found_key)
	254	debug2("key not found");
	255	return found_key;
	256	}
	257
	258	/* check whether given key is in .ssh/authorized_keys* */
	259	int
	260	user_key_allowed(struct passwd pw, Key key)
	261	{
	262	int success;
	263	char *file;
	264
	265	file = authorized_keys_file(pw);
	266	success = user_key_allowed2(pw, key, file);
	267	xfree(file);
	268	if (success)
	269	return success;
	270
	271	/* try suffix "2" for backward compat, too */
	272	file = authorized_keys_file2(pw);
	273	success = user_key_allowed2(pw, key, file);
	274	xfree(file);
	275	return success;
	276	}
	277
	278	Authmethod method_pubkey = {
	279	"publickey",
	280	userauth_pubkey,
	281	&options.pubkey_authentication
	282	};