[openssh.git] / auth2-pubkey.c

/* $OpenBSD: auth2-pubkey.c,v 1.13 2006/07/06 16:03:53 stevesk 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 "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
b1842393	1	/* $OpenBSD: auth2-pubkey.c,v 1.13 2006/07/06 16:03:53 stevesk 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>
b1842393	32
ea067773	33	#include "ssh.h"
013eab17	34	#include "ssh2.h"
	35	#include "xmalloc.h"
	36	#include "packet.h"
	37	#include "buffer.h"
	38	#include "log.h"
	39	#include "servconf.h"
	40	#include "compat.h"
	41	#include "bufaux.h"
	42	#include "auth.h"
	43	#include "key.h"
	44	#include "pathnames.h"
	45	#include "uidswap.h"
	46	#include "auth-options.h"
	47	#include "canohost.h"
	48	#include "monitor_wrap.h"
41feb690	49	#include "misc.h"
013eab17	50
	51	/* import */
	52	extern ServerOptions options;
	53	extern u_char *session_id2;
a27002e5	54	extern u_int session_id2_len;
013eab17	55
	56	static int
	57	userauth_pubkey(Authctxt *authctxt)
	58	{
	59	Buffer b;
	60	Key *key = NULL;
	61	char *pkalg;
	62	u_char pkblob, sig;
	63	u_int alen, blen, slen;
	64	int have_sig, pktype;
	65	int authenticated = 0;
	66
	67	if (!authctxt->valid) {
	68	debug2("userauth_pubkey: disabled because of invalid user");
	69	return 0;
	70	}
	71	have_sig = packet_get_char();
	72	if (datafellows & SSH_BUG_PKAUTH) {
	73	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	74	/* no explicit pkalg given */
	75	pkblob = packet_get_string(&blen);
	76	buffer_init(&b);
	77	buffer_append(&b, pkblob, blen);
	78	/* so we have to extract the pkalg from the pkblob */
	79	pkalg = buffer_get_string(&b, &alen);
	80	buffer_free(&b);
	81	} else {
	82	pkalg = packet_get_string(&alen);
	83	pkblob = packet_get_string(&blen);
	84	}
	85	pktype = key_type_from_name(pkalg);
	86	if (pktype == KEY_UNSPEC) {
	87	/* this is perfectly legal */
bbe88b6d	88	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	89	pkalg);
	90	goto done;
	91	}
	92	key = key_from_blob(pkblob, blen);
	93	if (key == NULL) {
	94	error("userauth_pubkey: cannot decode key: %s", pkalg);
	95	goto done;
	96	}
	97	if (key->type != pktype) {
	98	error("userauth_pubkey: type mismatch for decoded key "
	99	"(received %d, expected %d)", key->type, pktype);
	100	goto done;
	101	}
	102	if (have_sig) {
	103	sig = packet_get_string(&slen);
	104	packet_check_eom();
	105	buffer_init(&b);
	106	if (datafellows & SSH_OLD_SESSIONID) {
	107	buffer_append(&b, session_id2, session_id2_len);
	108	} else {
	109	buffer_put_string(&b, session_id2, session_id2_len);
	110	}
	111	/* reconstruct packet */
	112	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	113	buffer_put_cstring(&b, authctxt->user);
	114	buffer_put_cstring(&b,
	115	datafellows & SSH_BUG_PKSERVICE ?
	116	"ssh-userauth" :
	117	authctxt->service);
	118	if (datafellows & SSH_BUG_PKAUTH) {
	119	buffer_put_char(&b, have_sig);
	120	} else {
	121	buffer_put_cstring(&b, "publickey");
	122	buffer_put_char(&b, have_sig);
	123	buffer_put_cstring(&b, pkalg);
	124	}
	125	buffer_put_string(&b, pkblob, blen);
	126	#ifdef DEBUG_PK
	127	buffer_dump(&b);
	128	#endif
	129	/* test for correct signature */
	130	authenticated = 0;
	131	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	132	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	133	buffer_len(&b))) == 1)
013eab17	134	authenticated = 1;
43f7a4b8	135	buffer_free(&b);
013eab17	136	xfree(sig);
	137	} else {
	138	debug("test whether pkalg/pkblob are acceptable");
	139	packet_check_eom();
	140
	141	/* XXX fake reply and always send PK_OK ? */
	142	/*
	143	* XXX this allows testing whether a user is allowed
	144	* to login: if you happen to have a valid pubkey this
	145	* message is sent. the message is NEVER sent at all
	146	* if a user is not allowed to login. is this an
	147	* issue? -markus
	148	*/
	149	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	150	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	151	packet_put_string(pkalg, alen);
	152	packet_put_string(pkblob, blen);
	153	packet_send();
	154	packet_write_wait();
	155	authctxt->postponed = 1;
	156	}
	157	}
	158	if (authenticated != 1)
	159	auth_clear_options();
	160	done:
	161	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	162	if (key != NULL)
	163	key_free(key);
	164	xfree(pkalg);
	165	xfree(pkblob);
	166	#ifdef HAVE_CYGWIN
	167	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	168	authenticated = 0;
013eab17	169	#endif
	170	return authenticated;
	171	}
	172
	173	/* return 1 if user allows given key */
	174	static int
	175	user_key_allowed2(struct passwd pw, Key key, char *file)
	176	{
ea067773	177	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	178	int found_key = 0;
	179	FILE *f;
	180	u_long linenum = 0;
	181	struct stat st;
	182	Key *found;
	183	char *fp;
	184
013eab17	185	/* Temporarily use the user's uid. */
	186	temporarily_use_uid(pw);
	187
	188	debug("trying public key file %s", file);
	189
	190	/* Fail quietly if file does not exist */
	191	if (stat(file, &st) < 0) {
	192	/* Restore the privileged uid. */
	193	restore_uid();
	194	return 0;
	195	}
	196	/* Open the file containing the authorized keys. */
	197	f = fopen(file, "r");
	198	if (!f) {
	199	/* Restore the privileged uid. */
	200	restore_uid();
	201	return 0;
	202	}
	203	if (options.strict_modes &&
	204	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	205	fclose(f);
bbe88b6d	206	logit("Authentication refused: %s", line);
013eab17	207	restore_uid();
	208	return 0;
	209	}
	210
	211	found_key = 0;
	212	found = key_new(key->type);
	213
ea067773	214	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	215	char cp, key_options = NULL;
ea067773	216
013eab17	217	/* Skip leading whitespace, empty and comment lines. */
	218	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	219	;
	220	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	221	continue;
	222
	223	if (key_read(found, &cp) != 1) {
	224	/* no key? check if there are options for this key */
	225	int quoted = 0;
	226	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	227	key_options = cp;
013eab17	228	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	229	if (*cp == '\\' && cp[1] == '"')
	230	cp++; /* Skip both */
	231	else if (*cp == '"')
	232	quoted = !quoted;
	233	}
	234	/* Skip remaining whitespace. */
	235	for (; cp == ' ' \|\| cp == '\t'; cp++)
	236	;
	237	if (key_read(found, &cp) != 1) {
	238	debug2("user_key_allowed: advance: '%s'", cp);
	239	/* still no key? advance to next line*/
	240	continue;
	241	}
	242	}
	243	if (key_equal(found, key) &&
ca75d7de	244	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	245	found_key = 1;
	246	debug("matching key found: file %s, line %lu",
	247	file, linenum);
	248	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	249	verbose("Found matching %s key: %s",
	250	key_type(found), fp);
	251	xfree(fp);
	252	break;
	253	}
	254	}
	255	restore_uid();
	256	fclose(f);
	257	key_free(found);
	258	if (!found_key)
	259	debug2("key not found");
	260	return found_key;
	261	}
	262
	263	/* check whether given key is in .ssh/authorized_keys* */
	264	int
	265	user_key_allowed(struct passwd pw, Key key)
	266	{
	267	int success;
	268	char *file;
	269
	270	file = authorized_keys_file(pw);
	271	success = user_key_allowed2(pw, key, file);
	272	xfree(file);
	273	if (success)
	274	return success;
	275
	276	/* try suffix "2" for backward compat, too */
	277	file = authorized_keys_file2(pw);
	278	success = user_key_allowed2(pw, key, file);
	279	xfree(file);
	280	return success;
	281	}
	282
	283	Authmethod method_pubkey = {
	284	"publickey",
	285	userauth_pubkey,
	286	&options.pubkey_authentication
	287	};