[openssh.git] / auth2-pubkey.c

/* $OpenBSD: auth2-pubkey.c,v 1.12 2006/03/25 13:17:01 djm 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 "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
c1cb7bae	1	/* $OpenBSD: auth2-pubkey.c,v 1.12 2006/03/25 13:17:01 djm 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
ea067773	31	#include "ssh.h"
013eab17	32	#include "ssh2.h"
	33	#include "xmalloc.h"
	34	#include "packet.h"
	35	#include "buffer.h"
	36	#include "log.h"
	37	#include "servconf.h"
	38	#include "compat.h"
	39	#include "bufaux.h"
	40	#include "auth.h"
	41	#include "key.h"
	42	#include "pathnames.h"
	43	#include "uidswap.h"
	44	#include "auth-options.h"
	45	#include "canohost.h"
	46	#include "monitor_wrap.h"
41feb690	47	#include "misc.h"
013eab17	48
	49	/* import */
	50	extern ServerOptions options;
	51	extern u_char *session_id2;
a27002e5	52	extern u_int session_id2_len;
013eab17	53
	54	static int
	55	userauth_pubkey(Authctxt *authctxt)
	56	{
	57	Buffer b;
	58	Key *key = NULL;
	59	char *pkalg;
	60	u_char pkblob, sig;
	61	u_int alen, blen, slen;
	62	int have_sig, pktype;
	63	int authenticated = 0;
	64
	65	if (!authctxt->valid) {
	66	debug2("userauth_pubkey: disabled because of invalid user");
	67	return 0;
	68	}
	69	have_sig = packet_get_char();
	70	if (datafellows & SSH_BUG_PKAUTH) {
	71	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	72	/* no explicit pkalg given */
	73	pkblob = packet_get_string(&blen);
	74	buffer_init(&b);
	75	buffer_append(&b, pkblob, blen);
	76	/* so we have to extract the pkalg from the pkblob */
	77	pkalg = buffer_get_string(&b, &alen);
	78	buffer_free(&b);
	79	} else {
	80	pkalg = packet_get_string(&alen);
	81	pkblob = packet_get_string(&blen);
	82	}
	83	pktype = key_type_from_name(pkalg);
	84	if (pktype == KEY_UNSPEC) {
	85	/* this is perfectly legal */
bbe88b6d	86	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	87	pkalg);
	88	goto done;
	89	}
	90	key = key_from_blob(pkblob, blen);
	91	if (key == NULL) {
	92	error("userauth_pubkey: cannot decode key: %s", pkalg);
	93	goto done;
	94	}
	95	if (key->type != pktype) {
	96	error("userauth_pubkey: type mismatch for decoded key "
	97	"(received %d, expected %d)", key->type, pktype);
	98	goto done;
	99	}
	100	if (have_sig) {
	101	sig = packet_get_string(&slen);
	102	packet_check_eom();
	103	buffer_init(&b);
	104	if (datafellows & SSH_OLD_SESSIONID) {
	105	buffer_append(&b, session_id2, session_id2_len);
	106	} else {
	107	buffer_put_string(&b, session_id2, session_id2_len);
	108	}
	109	/* reconstruct packet */
	110	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	111	buffer_put_cstring(&b, authctxt->user);
	112	buffer_put_cstring(&b,
	113	datafellows & SSH_BUG_PKSERVICE ?
	114	"ssh-userauth" :
	115	authctxt->service);
	116	if (datafellows & SSH_BUG_PKAUTH) {
	117	buffer_put_char(&b, have_sig);
	118	} else {
	119	buffer_put_cstring(&b, "publickey");
	120	buffer_put_char(&b, have_sig);
	121	buffer_put_cstring(&b, pkalg);
	122	}
	123	buffer_put_string(&b, pkblob, blen);
	124	#ifdef DEBUG_PK
	125	buffer_dump(&b);
	126	#endif
	127	/* test for correct signature */
	128	authenticated = 0;
	129	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	130	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	131	buffer_len(&b))) == 1)
013eab17	132	authenticated = 1;
43f7a4b8	133	buffer_free(&b);
013eab17	134	xfree(sig);
	135	} else {
	136	debug("test whether pkalg/pkblob are acceptable");
	137	packet_check_eom();
	138
	139	/* XXX fake reply and always send PK_OK ? */
	140	/*
	141	* XXX this allows testing whether a user is allowed
	142	* to login: if you happen to have a valid pubkey this
	143	* message is sent. the message is NEVER sent at all
	144	* if a user is not allowed to login. is this an
	145	* issue? -markus
	146	*/
	147	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	148	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	149	packet_put_string(pkalg, alen);
	150	packet_put_string(pkblob, blen);
	151	packet_send();
	152	packet_write_wait();
	153	authctxt->postponed = 1;
	154	}
	155	}
	156	if (authenticated != 1)
	157	auth_clear_options();
	158	done:
	159	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	160	if (key != NULL)
	161	key_free(key);
	162	xfree(pkalg);
	163	xfree(pkblob);
	164	#ifdef HAVE_CYGWIN
	165	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	166	authenticated = 0;
013eab17	167	#endif
	168	return authenticated;
	169	}
	170
	171	/* return 1 if user allows given key */
	172	static int
	173	user_key_allowed2(struct passwd pw, Key key, char *file)
	174	{
ea067773	175	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	176	int found_key = 0;
	177	FILE *f;
	178	u_long linenum = 0;
	179	struct stat st;
	180	Key *found;
	181	char *fp;
	182
013eab17	183	/* Temporarily use the user's uid. */
	184	temporarily_use_uid(pw);
	185
	186	debug("trying public key file %s", file);
	187
	188	/* Fail quietly if file does not exist */
	189	if (stat(file, &st) < 0) {
	190	/* Restore the privileged uid. */
	191	restore_uid();
	192	return 0;
	193	}
	194	/* Open the file containing the authorized keys. */
	195	f = fopen(file, "r");
	196	if (!f) {
	197	/* Restore the privileged uid. */
	198	restore_uid();
	199	return 0;
	200	}
	201	if (options.strict_modes &&
	202	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	203	fclose(f);
bbe88b6d	204	logit("Authentication refused: %s", line);
013eab17	205	restore_uid();
	206	return 0;
	207	}
	208
	209	found_key = 0;
	210	found = key_new(key->type);
	211
ea067773	212	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	213	char cp, key_options = NULL;
ea067773	214
013eab17	215	/* Skip leading whitespace, empty and comment lines. */
	216	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	217	;
	218	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	219	continue;
	220
	221	if (key_read(found, &cp) != 1) {
	222	/* no key? check if there are options for this key */
	223	int quoted = 0;
	224	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	225	key_options = cp;
013eab17	226	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	227	if (*cp == '\\' && cp[1] == '"')
	228	cp++; /* Skip both */
	229	else if (*cp == '"')
	230	quoted = !quoted;
	231	}
	232	/* Skip remaining whitespace. */
	233	for (; cp == ' ' \|\| cp == '\t'; cp++)
	234	;
	235	if (key_read(found, &cp) != 1) {
	236	debug2("user_key_allowed: advance: '%s'", cp);
	237	/* still no key? advance to next line*/
	238	continue;
	239	}
	240	}
	241	if (key_equal(found, key) &&
ca75d7de	242	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	243	found_key = 1;
	244	debug("matching key found: file %s, line %lu",
	245	file, linenum);
	246	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	247	verbose("Found matching %s key: %s",
	248	key_type(found), fp);
	249	xfree(fp);
	250	break;
	251	}
	252	}
	253	restore_uid();
	254	fclose(f);
	255	key_free(found);
	256	if (!found_key)
	257	debug2("key not found");
	258	return found_key;
	259	}
	260
	261	/* check whether given key is in .ssh/authorized_keys* */
	262	int
	263	user_key_allowed(struct passwd pw, Key key)
	264	{
	265	int success;
	266	char *file;
	267
	268	file = authorized_keys_file(pw);
	269	success = user_key_allowed2(pw, key, file);
	270	xfree(file);
	271	if (success)
	272	return success;
	273
	274	/* try suffix "2" for backward compat, too */
	275	file = authorized_keys_file2(pw);
	276	success = user_key_allowed2(pw, key, file);
	277	xfree(file);
	278	return success;
	279	}
	280
	281	Authmethod method_pubkey = {
	282	"publickey",
	283	userauth_pubkey,
	284	&options.pubkey_authentication
	285	};