[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 1.8 2004/12/06 11:41:03 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"

/* 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"
ea067773	26	RCSID("$OpenBSD: auth2-pubkey.c,v 1.8 2004/12/06 11:41:03 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"
	44
	45	/* import */
	46	extern ServerOptions options;
	47	extern u_char *session_id2;
a27002e5	48	extern u_int session_id2_len;
013eab17	49
	50	static int
	51	userauth_pubkey(Authctxt *authctxt)
	52	{
	53	Buffer b;
	54	Key *key = NULL;
	55	char *pkalg;
	56	u_char pkblob, sig;
	57	u_int alen, blen, slen;
	58	int have_sig, pktype;
	59	int authenticated = 0;
	60
	61	if (!authctxt->valid) {
	62	debug2("userauth_pubkey: disabled because of invalid user");
	63	return 0;
	64	}
	65	have_sig = packet_get_char();
	66	if (datafellows & SSH_BUG_PKAUTH) {
	67	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	68	/* no explicit pkalg given */
	69	pkblob = packet_get_string(&blen);
	70	buffer_init(&b);
	71	buffer_append(&b, pkblob, blen);
	72	/* so we have to extract the pkalg from the pkblob */
	73	pkalg = buffer_get_string(&b, &alen);
	74	buffer_free(&b);
	75	} else {
	76	pkalg = packet_get_string(&alen);
	77	pkblob = packet_get_string(&blen);
	78	}
	79	pktype = key_type_from_name(pkalg);
	80	if (pktype == KEY_UNSPEC) {
	81	/* this is perfectly legal */
bbe88b6d	82	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	83	pkalg);
	84	goto done;
	85	}
	86	key = key_from_blob(pkblob, blen);
	87	if (key == NULL) {
	88	error("userauth_pubkey: cannot decode key: %s", pkalg);
	89	goto done;
	90	}
	91	if (key->type != pktype) {
	92	error("userauth_pubkey: type mismatch for decoded key "
	93	"(received %d, expected %d)", key->type, pktype);
	94	goto done;
	95	}
	96	if (have_sig) {
	97	sig = packet_get_string(&slen);
	98	packet_check_eom();
	99	buffer_init(&b);
	100	if (datafellows & SSH_OLD_SESSIONID) {
	101	buffer_append(&b, session_id2, session_id2_len);
	102	} else {
	103	buffer_put_string(&b, session_id2, session_id2_len);
	104	}
	105	/* reconstruct packet */
	106	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	107	buffer_put_cstring(&b, authctxt->user);
	108	buffer_put_cstring(&b,
	109	datafellows & SSH_BUG_PKSERVICE ?
	110	"ssh-userauth" :
	111	authctxt->service);
	112	if (datafellows & SSH_BUG_PKAUTH) {
	113	buffer_put_char(&b, have_sig);
	114	} else {
	115	buffer_put_cstring(&b, "publickey");
	116	buffer_put_char(&b, have_sig);
	117	buffer_put_cstring(&b, pkalg);
	118	}
	119	buffer_put_string(&b, pkblob, blen);
	120	#ifdef DEBUG_PK
	121	buffer_dump(&b);
	122	#endif
	123	/* test for correct signature */
	124	authenticated = 0;
	125	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	126	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	127	buffer_len(&b))) == 1)
013eab17	128	authenticated = 1;
43f7a4b8	129	buffer_free(&b);
013eab17	130	xfree(sig);
	131	} else {
	132	debug("test whether pkalg/pkblob are acceptable");
	133	packet_check_eom();
	134
	135	/* XXX fake reply and always send PK_OK ? */
	136	/*
	137	* XXX this allows testing whether a user is allowed
	138	* to login: if you happen to have a valid pubkey this
	139	* message is sent. the message is NEVER sent at all
	140	* if a user is not allowed to login. is this an
	141	* issue? -markus
	142	*/
	143	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	144	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	145	packet_put_string(pkalg, alen);
	146	packet_put_string(pkblob, blen);
	147	packet_send();
	148	packet_write_wait();
	149	authctxt->postponed = 1;
	150	}
	151	}
	152	if (authenticated != 1)
	153	auth_clear_options();
	154	done:
	155	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	156	if (key != NULL)
	157	key_free(key);
	158	xfree(pkalg);
	159	xfree(pkblob);
	160	#ifdef HAVE_CYGWIN
	161	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	162	authenticated = 0;
013eab17	163	#endif
	164	return authenticated;
	165	}
	166
	167	/* return 1 if user allows given key */
	168	static int
	169	user_key_allowed2(struct passwd pw, Key key, char *file)
	170	{
ea067773	171	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	172	int found_key = 0;
	173	FILE *f;
	174	u_long linenum = 0;
	175	struct stat st;
	176	Key *found;
	177	char *fp;
	178
013eab17	179	/* Temporarily use the user's uid. */
	180	temporarily_use_uid(pw);
	181
	182	debug("trying public key file %s", file);
	183
	184	/* Fail quietly if file does not exist */
	185	if (stat(file, &st) < 0) {
	186	/* Restore the privileged uid. */
	187	restore_uid();
	188	return 0;
	189	}
	190	/* Open the file containing the authorized keys. */
	191	f = fopen(file, "r");
	192	if (!f) {
	193	/* Restore the privileged uid. */
	194	restore_uid();
	195	return 0;
	196	}
	197	if (options.strict_modes &&
	198	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	199	fclose(f);
bbe88b6d	200	logit("Authentication refused: %s", line);
013eab17	201	restore_uid();
	202	return 0;
	203	}
	204
	205	found_key = 0;
	206	found = key_new(key->type);
	207
ea067773	208	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	209	char cp, key_options = NULL;
ea067773	210
013eab17	211	/* Skip leading whitespace, empty and comment lines. */
	212	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	213	;
	214	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	215	continue;
	216
	217	if (key_read(found, &cp) != 1) {
	218	/* no key? check if there are options for this key */
	219	int quoted = 0;
	220	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	221	key_options = cp;
013eab17	222	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	223	if (*cp == '\\' && cp[1] == '"')
	224	cp++; /* Skip both */
	225	else if (*cp == '"')
	226	quoted = !quoted;
	227	}
	228	/* Skip remaining whitespace. */
	229	for (; cp == ' ' \|\| cp == '\t'; cp++)
	230	;
	231	if (key_read(found, &cp) != 1) {
	232	debug2("user_key_allowed: advance: '%s'", cp);
	233	/* still no key? advance to next line*/
	234	continue;
	235	}
	236	}
	237	if (key_equal(found, key) &&
ca75d7de	238	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	239	found_key = 1;
	240	debug("matching key found: file %s, line %lu",
	241	file, linenum);
	242	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	243	verbose("Found matching %s key: %s",
	244	key_type(found), fp);
	245	xfree(fp);
	246	break;
	247	}
	248	}
	249	restore_uid();
	250	fclose(f);
	251	key_free(found);
	252	if (!found_key)
	253	debug2("key not found");
	254	return found_key;
	255	}
	256
	257	/* check whether given key is in .ssh/authorized_keys* */
	258	int
	259	user_key_allowed(struct passwd pw, Key key)
	260	{
	261	int success;
	262	char *file;
	263
	264	file = authorized_keys_file(pw);
	265	success = user_key_allowed2(pw, key, file);
	266	xfree(file);
	267	if (success)
	268	return success;
	269
	270	/* try suffix "2" for backward compat, too */
	271	file = authorized_keys_file2(pw);
	272	success = user_key_allowed2(pw, key, file);
	273	xfree(file);
	274	return success;
	275	}
	276
	277	Authmethod method_pubkey = {
	278	"publickey",
	279	userauth_pubkey,
	280	&options.pubkey_authentication
	281	};