[openssh.git] / auth2-pubkey.c

/* $OpenBSD: auth2-pubkey.c,v 1.14 2006/08/01 23:22:47 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 <stdio.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
cf851879	1	/* $OpenBSD: auth2-pubkey.c,v 1.14 2006/08/01 23:22:47 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>
cf851879	32	#include <stdio.h>
b1842393	33
ea067773	34	#include "ssh.h"
013eab17	35	#include "ssh2.h"
	36	#include "xmalloc.h"
	37	#include "packet.h"
	38	#include "buffer.h"
	39	#include "log.h"
	40	#include "servconf.h"
	41	#include "compat.h"
	42	#include "bufaux.h"
	43	#include "auth.h"
	44	#include "key.h"
	45	#include "pathnames.h"
	46	#include "uidswap.h"
	47	#include "auth-options.h"
	48	#include "canohost.h"
	49	#include "monitor_wrap.h"
41feb690	50	#include "misc.h"
013eab17	51
	52	/* import */
	53	extern ServerOptions options;
	54	extern u_char *session_id2;
a27002e5	55	extern u_int session_id2_len;
013eab17	56
	57	static int
	58	userauth_pubkey(Authctxt *authctxt)
	59	{
	60	Buffer b;
	61	Key *key = NULL;
	62	char *pkalg;
	63	u_char pkblob, sig;
	64	u_int alen, blen, slen;
	65	int have_sig, pktype;
	66	int authenticated = 0;
	67
	68	if (!authctxt->valid) {
	69	debug2("userauth_pubkey: disabled because of invalid user");
	70	return 0;
	71	}
	72	have_sig = packet_get_char();
	73	if (datafellows & SSH_BUG_PKAUTH) {
	74	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	75	/* no explicit pkalg given */
	76	pkblob = packet_get_string(&blen);
	77	buffer_init(&b);
	78	buffer_append(&b, pkblob, blen);
	79	/* so we have to extract the pkalg from the pkblob */
	80	pkalg = buffer_get_string(&b, &alen);
	81	buffer_free(&b);
	82	} else {
	83	pkalg = packet_get_string(&alen);
	84	pkblob = packet_get_string(&blen);
	85	}
	86	pktype = key_type_from_name(pkalg);
	87	if (pktype == KEY_UNSPEC) {
	88	/* this is perfectly legal */
bbe88b6d	89	logit("userauth_pubkey: unsupported public key algorithm: %s",
013eab17	90	pkalg);
	91	goto done;
	92	}
	93	key = key_from_blob(pkblob, blen);
	94	if (key == NULL) {
	95	error("userauth_pubkey: cannot decode key: %s", pkalg);
	96	goto done;
	97	}
	98	if (key->type != pktype) {
	99	error("userauth_pubkey: type mismatch for decoded key "
	100	"(received %d, expected %d)", key->type, pktype);
	101	goto done;
	102	}
	103	if (have_sig) {
	104	sig = packet_get_string(&slen);
	105	packet_check_eom();
	106	buffer_init(&b);
	107	if (datafellows & SSH_OLD_SESSIONID) {
	108	buffer_append(&b, session_id2, session_id2_len);
	109	} else {
	110	buffer_put_string(&b, session_id2, session_id2_len);
	111	}
	112	/* reconstruct packet */
	113	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	114	buffer_put_cstring(&b, authctxt->user);
	115	buffer_put_cstring(&b,
	116	datafellows & SSH_BUG_PKSERVICE ?
	117	"ssh-userauth" :
	118	authctxt->service);
	119	if (datafellows & SSH_BUG_PKAUTH) {
	120	buffer_put_char(&b, have_sig);
	121	} else {
	122	buffer_put_cstring(&b, "publickey");
	123	buffer_put_char(&b, have_sig);
	124	buffer_put_cstring(&b, pkalg);
	125	}
	126	buffer_put_string(&b, pkblob, blen);
	127	#ifdef DEBUG_PK
	128	buffer_dump(&b);
	129	#endif
	130	/* test for correct signature */
	131	authenticated = 0;
	132	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	133	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
43f7a4b8	134	buffer_len(&b))) == 1)
013eab17	135	authenticated = 1;
43f7a4b8	136	buffer_free(&b);
013eab17	137	xfree(sig);
	138	} else {
	139	debug("test whether pkalg/pkblob are acceptable");
	140	packet_check_eom();
	141
	142	/* XXX fake reply and always send PK_OK ? */
	143	/*
	144	* XXX this allows testing whether a user is allowed
	145	* to login: if you happen to have a valid pubkey this
	146	* message is sent. the message is NEVER sent at all
	147	* if a user is not allowed to login. is this an
	148	* issue? -markus
	149	*/
	150	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	151	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	152	packet_put_string(pkalg, alen);
	153	packet_put_string(pkblob, blen);
	154	packet_send();
	155	packet_write_wait();
	156	authctxt->postponed = 1;
	157	}
	158	}
	159	if (authenticated != 1)
	160	auth_clear_options();
	161	done:
	162	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	163	if (key != NULL)
	164	key_free(key);
	165	xfree(pkalg);
	166	xfree(pkblob);
	167	#ifdef HAVE_CYGWIN
	168	if (check_nt_auth(0, authctxt->pw) == 0)
73b1ee82	169	authenticated = 0;
013eab17	170	#endif
	171	return authenticated;
	172	}
	173
	174	/* return 1 if user allows given key */
	175	static int
	176	user_key_allowed2(struct passwd pw, Key key, char *file)
	177	{
ea067773	178	char line[SSH_MAX_PUBKEY_BYTES];
013eab17	179	int found_key = 0;
	180	FILE *f;
	181	u_long linenum = 0;
	182	struct stat st;
	183	Key *found;
	184	char *fp;
	185
013eab17	186	/* Temporarily use the user's uid. */
	187	temporarily_use_uid(pw);
	188
	189	debug("trying public key file %s", file);
	190
	191	/* Fail quietly if file does not exist */
	192	if (stat(file, &st) < 0) {
	193	/* Restore the privileged uid. */
	194	restore_uid();
	195	return 0;
	196	}
	197	/* Open the file containing the authorized keys. */
	198	f = fopen(file, "r");
	199	if (!f) {
	200	/* Restore the privileged uid. */
	201	restore_uid();
	202	return 0;
	203	}
	204	if (options.strict_modes &&
	205	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	206	fclose(f);
bbe88b6d	207	logit("Authentication refused: %s", line);
013eab17	208	restore_uid();
	209	return 0;
	210	}
	211
	212	found_key = 0;
	213	found = key_new(key->type);
	214
ea067773	215	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
ca75d7de	216	char cp, key_options = NULL;
ea067773	217
013eab17	218	/* Skip leading whitespace, empty and comment lines. */
	219	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	220	;
	221	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	222	continue;
	223
	224	if (key_read(found, &cp) != 1) {
	225	/* no key? check if there are options for this key */
	226	int quoted = 0;
	227	debug2("user_key_allowed: check options: '%s'", cp);
ca75d7de	228	key_options = cp;
013eab17	229	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	230	if (*cp == '\\' && cp[1] == '"')
	231	cp++; /* Skip both */
	232	else if (*cp == '"')
	233	quoted = !quoted;
	234	}
	235	/* Skip remaining whitespace. */
	236	for (; cp == ' ' \|\| cp == '\t'; cp++)
	237	;
	238	if (key_read(found, &cp) != 1) {
	239	debug2("user_key_allowed: advance: '%s'", cp);
	240	/* still no key? advance to next line*/
	241	continue;
	242	}
	243	}
	244	if (key_equal(found, key) &&
ca75d7de	245	auth_parse_options(pw, key_options, file, linenum) == 1) {
013eab17	246	found_key = 1;
	247	debug("matching key found: file %s, line %lu",
	248	file, linenum);
	249	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	250	verbose("Found matching %s key: %s",
	251	key_type(found), fp);
	252	xfree(fp);
	253	break;
	254	}
	255	}
	256	restore_uid();
	257	fclose(f);
	258	key_free(found);
	259	if (!found_key)
	260	debug2("key not found");
	261	return found_key;
	262	}
	263
	264	/* check whether given key is in .ssh/authorized_keys* */
	265	int
	266	user_key_allowed(struct passwd pw, Key key)
	267	{
	268	int success;
	269	char *file;
	270
	271	file = authorized_keys_file(pw);
	272	success = user_key_allowed2(pw, key, file);
	273	xfree(file);
	274	if (success)
	275	return success;
	276
	277	/* try suffix "2" for backward compat, too */
	278	file = authorized_keys_file2(pw);
	279	success = user_key_allowed2(pw, key, file);
	280	xfree(file);
	281	return success;
	282	}
	283
	284	Authmethod method_pubkey = {
	285	"publickey",
	286	userauth_pubkey,
	287	&options.pubkey_authentication
	288	};