[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"

#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
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"
4095f623	26
	27	#include <sys/types.h>
	28	#include <sys/stat.h>
013eab17	29
ea067773	30	#include "ssh.h"
013eab17	31	#include "ssh2.h"
	32	#include "xmalloc.h"
	33	#include "packet.h"
	34	#include "buffer.h"
	35	#include "log.h"
	36	#include "servconf.h"
	37	#include "compat.h"
	38	#include "bufaux.h"
	39	#include "auth.h"
	40	#include "key.h"
	41	#include "pathnames.h"
	42	#include "uidswap.h"
	43	#include "auth-options.h"
	44	#include "canohost.h"
	45	#include "monitor_wrap.h"
41feb690	46	#include "misc.h"
013eab17	47
	48	/* import */
	49	extern ServerOptions options;
	50	extern u_char *session_id2;
a27002e5	51	extern u_int session_id2_len;
013eab17	52
	53	static int
	54	userauth_pubkey(Authctxt *authctxt)
	55	{
	56	Buffer b;
	57	Key *key = NULL;
	58	char *pkalg;
	59	u_char pkblob, sig;
	60	u_int alen, blen, slen;
	61	int have_sig, pktype;
	62	int authenticated = 0;
	63
	64	if (!authctxt->valid) {
	65	debug2("userauth_pubkey: disabled because of invalid user");
	66	return 0;
	67	}
	68	have_sig = packet_get_char();
	69	if (datafellows & SSH_BUG_PKAUTH) {
	70	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	71	/* no explicit pkalg given */
	72	pkblob = packet_get_string(&blen);
	73	buffer_init(&b);
	74	buffer_append(&b, pkblob, blen);
	75	/* so we have to extract the pkalg from the pkblob */
	76	pkalg = buffer_get_string(&b, &alen);
	77	buffer_free(&b);
	78	} else {
	79	pkalg = packet_get_string(&alen);
	80	pkblob = packet_get_string(&blen);
	81	}
	82	pktype = key_type_from_name(pkalg);
	83	if (pktype == KEY_UNSPEC) {
	84	/* this is perfectly legal */
bbe88b6d	85	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	86	pkalg);
	87	goto done;
	88	}
	89	key = key_from_blob(pkblob, blen);
	90	if (key == NULL) {
	91	error("userauth_pubkey: cannot decode key: %s", pkalg);
	92	goto done;
	93	}
	94	if (key->type != pktype) {
	95	error("userauth_pubkey: type mismatch for decoded key "
	96	"(received %d, expected %d)", key->type, pktype);
	97	goto done;
	98	}
	99	if (have_sig) {
	100	sig = packet_get_string(&slen);
	101	packet_check_eom();
	102	buffer_init(&b);
	103	if (datafellows & SSH_OLD_SESSIONID) {
	104	buffer_append(&b, session_id2, session_id2_len);
	105	} else {
	106	buffer_put_string(&b, session_id2, session_id2_len);
	107	}
	108	/* reconstruct packet */
	109	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	110	buffer_put_cstring(&b, authctxt->user);
	111	buffer_put_cstring(&b,
	112	datafellows & SSH_BUG_PKSERVICE ?
	113	"ssh-userauth" :
	114	authctxt->service);
	115	if (datafellows & SSH_BUG_PKAUTH) {
	116	buffer_put_char(&b, have_sig);
	117	} else {
	118	buffer_put_cstring(&b, "publickey");
	119	buffer_put_char(&b, have_sig);
	120	buffer_put_cstring(&b, pkalg);
	121	}
	122	buffer_put_string(&b, pkblob, blen);
	123	#ifdef DEBUG_PK
	124	buffer_dump(&b);
	125	#endif
	126	/* test for correct signature */
	127	authenticated = 0;
	128	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	129	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	130	buffer_len(&b))) == 1)
013eab17	131	authenticated = 1;
43f7a4b8	132	buffer_free(&b);
013eab17	133	xfree(sig);
	134	} else {
	135	debug("test whether pkalg/pkblob are acceptable");
	136	packet_check_eom();
	137
	138	/* XXX fake reply and always send PK_OK ? */
	139	/*
	140	* XXX this allows testing whether a user is allowed
	141	* to login: if you happen to have a valid pubkey this
	142	* message is sent. the message is NEVER sent at all
	143	* if a user is not allowed to login. is this an
	144	* issue? -markus
	145	*/
	146	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	147	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	148	packet_put_string(pkalg, alen);
	149	packet_put_string(pkblob, blen);
	150	packet_send();
	151	packet_write_wait();
	152	authctxt->postponed = 1;
	153	}
	154	}
	155	if (authenticated != 1)
	156	auth_clear_options();
	157	done:
	158	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	159	if (key != NULL)
	160	key_free(key);
	161	xfree(pkalg);
	162	xfree(pkblob);
	163	#ifdef HAVE_CYGWIN
	164	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	165	authenticated = 0;
013eab17	166	#endif
	167	return authenticated;
	168	}
	169
	170	/* return 1 if user allows given key */
	171	static int
	172	user_key_allowed2(struct passwd pw, Key key, char *file)
	173	{
ea067773	174	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	175	int found_key = 0;
	176	FILE *f;
	177	u_long linenum = 0;
	178	struct stat st;
	179	Key *found;
	180	char *fp;
	181
013eab17	182	/* Temporarily use the user's uid. */
	183	temporarily_use_uid(pw);
	184
	185	debug("trying public key file %s", file);
	186
	187	/* Fail quietly if file does not exist */
	188	if (stat(file, &st) < 0) {
	189	/* Restore the privileged uid. */
	190	restore_uid();
	191	return 0;
	192	}
	193	/* Open the file containing the authorized keys. */
	194	f = fopen(file, "r");
	195	if (!f) {
	196	/* Restore the privileged uid. */
	197	restore_uid();
	198	return 0;
	199	}
	200	if (options.strict_modes &&
	201	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	202	fclose(f);
bbe88b6d	203	logit("Authentication refused: %s", line);
013eab17	204	restore_uid();
	205	return 0;
	206	}
	207
	208	found_key = 0;
	209	found = key_new(key->type);
	210
ea067773	211	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	212	char cp, key_options = NULL;
ea067773	213
013eab17	214	/* Skip leading whitespace, empty and comment lines. */
	215	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	216	;
	217	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	218	continue;
	219
	220	if (key_read(found, &cp) != 1) {
	221	/* no key? check if there are options for this key */
	222	int quoted = 0;
	223	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	224	key_options = cp;
013eab17	225	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	226	if (*cp == '\\' && cp[1] == '"')
	227	cp++; /* Skip both */
	228	else if (*cp == '"')
	229	quoted = !quoted;
	230	}
	231	/* Skip remaining whitespace. */
	232	for (; cp == ' ' \|\| cp == '\t'; cp++)
	233	;
	234	if (key_read(found, &cp) != 1) {
	235	debug2("user_key_allowed: advance: '%s'", cp);
	236	/* still no key? advance to next line*/
	237	continue;
	238	}
	239	}
	240	if (key_equal(found, key) &&
ca75d7de	241	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	242	found_key = 1;
	243	debug("matching key found: file %s, line %lu",
	244	file, linenum);
	245	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	246	verbose("Found matching %s key: %s",
	247	key_type(found), fp);
	248	xfree(fp);
	249	break;
	250	}
	251	}
	252	restore_uid();
	253	fclose(f);
	254	key_free(found);
	255	if (!found_key)
	256	debug2("key not found");
	257	return found_key;
	258	}
	259
	260	/* check whether given key is in .ssh/authorized_keys* */
	261	int
	262	user_key_allowed(struct passwd pw, Key key)
	263	{
	264	int success;
	265	char *file;
	266
	267	file = authorized_keys_file(pw);
	268	success = user_key_allowed2(pw, key, file);
	269	xfree(file);
	270	if (success)
	271	return success;
	272
	273	/* try suffix "2" for backward compat, too */
	274	file = authorized_keys_file2(pw);
	275	success = user_key_allowed2(pw, key, file);
	276	xfree(file);
	277	return success;
	278	}
	279
	280	Authmethod method_pubkey = {
	281	"publickey",
	282	userauth_pubkey,
	283	&options.pubkey_authentication
	284	};