ssh-keysign.c revision 157016
198675Sdes/*
298675Sdes * Copyright (c) 2002 Markus Friedl.  All rights reserved.
398675Sdes *
498675Sdes * Redistribution and use in source and binary forms, with or without
598675Sdes * modification, are permitted provided that the following conditions
698675Sdes * are met:
798675Sdes * 1. Redistributions of source code must retain the above copyright
898675Sdes *    notice, this list of conditions and the following disclaimer.
998675Sdes * 2. Redistributions in binary form must reproduce the above copyright
1098675Sdes *    notice, this list of conditions and the following disclaimer in the
1198675Sdes *    documentation and/or other materials provided with the distribution.
1298675Sdes *
1398675Sdes * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
1498675Sdes * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
1598675Sdes * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
1698675Sdes * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
1798675Sdes * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
1898675Sdes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
1998675Sdes * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
2098675Sdes * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
2198675Sdes * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
2298675Sdes * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
2398675Sdes */
2498675Sdes#include "includes.h"
25157016SdesRCSID("$OpenBSD: ssh-keysign.c,v 1.19 2005/09/13 23:40:07 djm Exp $");
2698675Sdes
2798675Sdes#include <openssl/evp.h>
28106121Sdes#include <openssl/rand.h>
29106121Sdes#include <openssl/rsa.h>
3098675Sdes
3198675Sdes#include "log.h"
3298675Sdes#include "key.h"
33106121Sdes#include "ssh.h"
3498675Sdes#include "ssh2.h"
3598675Sdes#include "misc.h"
3698675Sdes#include "xmalloc.h"
3798675Sdes#include "buffer.h"
3898675Sdes#include "bufaux.h"
3998675Sdes#include "authfile.h"
4098675Sdes#include "msg.h"
4198675Sdes#include "canohost.h"
4298675Sdes#include "pathnames.h"
43106121Sdes#include "readconf.h"
44137015Sdes#include "uidswap.h"
4598675Sdes
46124208Sdes/* XXX readconf.c needs these */
47124208Sdesuid_t original_real_uid;
48106121Sdes
4998937Sdesextern char *__progname;
5098937Sdes
5198675Sdesstatic int
5298675Sdesvalid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
5398675Sdes    u_int datalen)
5498675Sdes{
5598675Sdes	Buffer b;
56124208Sdes	Key *key = NULL;
5798675Sdes	u_char *pkblob;
5898675Sdes	u_int blen, len;
5998675Sdes	char *pkalg, *p;
6098675Sdes	int pktype, fail;
6198675Sdes
6298675Sdes	fail = 0;
6398675Sdes
6498675Sdes	buffer_init(&b);
6598675Sdes	buffer_append(&b, data, datalen);
6698675Sdes
6798675Sdes	/* session id, currently limited to SHA1 (20 bytes) */
6898675Sdes	p = buffer_get_string(&b, &len);
6998675Sdes	if (len != 20)
7098675Sdes		fail++;
7198675Sdes	xfree(p);
7298675Sdes
7398675Sdes	if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
7498675Sdes		fail++;
7598675Sdes
7698675Sdes	/* server user */
7798675Sdes	buffer_skip_string(&b);
7898675Sdes
7998675Sdes	/* service */
8098675Sdes	p = buffer_get_string(&b, NULL);
8198675Sdes	if (strcmp("ssh-connection", p) != 0)
8298675Sdes		fail++;
8398675Sdes	xfree(p);
8498675Sdes
8598675Sdes	/* method */
8698675Sdes	p = buffer_get_string(&b, NULL);
8798675Sdes	if (strcmp("hostbased", p) != 0)
8898675Sdes		fail++;
8998675Sdes	xfree(p);
9098675Sdes
9198675Sdes	/* pubkey */
9298675Sdes	pkalg = buffer_get_string(&b, NULL);
9398675Sdes	pkblob = buffer_get_string(&b, &blen);
9498675Sdes
9598675Sdes	pktype = key_type_from_name(pkalg);
9698675Sdes	if (pktype == KEY_UNSPEC)
9798675Sdes		fail++;
9898675Sdes	else if ((key = key_from_blob(pkblob, blen)) == NULL)
9998675Sdes		fail++;
10098675Sdes	else if (key->type != pktype)
10198675Sdes		fail++;
10298675Sdes	xfree(pkalg);
10398675Sdes	xfree(pkblob);
10498675Sdes
10598675Sdes	/* client host name, handle trailing dot */
10698675Sdes	p = buffer_get_string(&b, &len);
10798675Sdes	debug2("valid_request: check expect chost %s got %s", host, p);
10898675Sdes	if (strlen(host) != len - 1)
10998675Sdes		fail++;
11098675Sdes	else if (p[len - 1] != '.')
11198675Sdes		fail++;
11298675Sdes	else if (strncasecmp(host, p, len - 1) != 0)
11398675Sdes		fail++;
11498675Sdes	xfree(p);
11598675Sdes
11698675Sdes	/* local user */
11798675Sdes	p = buffer_get_string(&b, NULL);
11898675Sdes
11998675Sdes	if (strcmp(pw->pw_name, p) != 0)
12098675Sdes		fail++;
12198675Sdes	xfree(p);
12298675Sdes
12398675Sdes	/* end of message */
12498675Sdes	if (buffer_len(&b) != 0)
12598675Sdes		fail++;
126126274Sdes	buffer_free(&b);
12798675Sdes
12898675Sdes	debug3("valid_request: fail %d", fail);
12998675Sdes
13098675Sdes	if (fail && key != NULL)
13198675Sdes		key_free(key);
13298675Sdes	else
13398675Sdes		*ret = key;
13498675Sdes
13598675Sdes	return (fail ? -1 : 0);
13698675Sdes}
13798675Sdes
13898675Sdesint
13998675Sdesmain(int argc, char **argv)
14098675Sdes{
14198675Sdes	Buffer b;
142106121Sdes	Options options;
14398675Sdes	Key *keys[2], *key;
14498675Sdes	struct passwd *pw;
14598675Sdes	int key_fd[2], i, found, version = 2, fd;
14698675Sdes	u_char *signature, *data;
14798675Sdes	char *host;
14898675Sdes	u_int slen, dlen;
149106121Sdes	u_int32_t rnd[256];
15098675Sdes
151157016Sdes	/* Ensure that stdin and stdout are connected */
152157016Sdes	if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
153157016Sdes		exit(1);
154157016Sdes	/* Leave /dev/null fd iff it is attached to stderr */
155157016Sdes	if (fd > 2)
156157016Sdes		close(fd);
157157016Sdes
15898675Sdes	key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
15998675Sdes	key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
16098675Sdes
161146998Sdes	original_real_uid = getuid();	/* XXX readconf.c needs this */
162146998Sdes	if ((pw = getpwuid(original_real_uid)) == NULL)
163137015Sdes		fatal("getpwuid failed");
164137015Sdes	pw = pwcopy(pw);
16598675Sdes
166137015Sdes	permanently_set_uid(pw);
167137015Sdes
16898937Sdes	init_rng();
16998937Sdes	seed_rng();
17098937Sdes	arc4random_stir();
17198937Sdes
17298675Sdes#ifdef DEBUG_SSH_KEYSIGN
17398675Sdes	log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
17498675Sdes#endif
17598675Sdes
176106121Sdes	/* verify that ssh-keysign is enabled by the admin */
177106121Sdes	initialize_options(&options);
178137015Sdes	(void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0);
179106121Sdes	fill_default_options(&options);
180113908Sdes	if (options.enable_ssh_keysign != 1)
181113908Sdes		fatal("ssh-keysign not enabled in %s",
182106121Sdes		    _PATH_HOST_CONFIG_FILE);
183106121Sdes
18498675Sdes	if (key_fd[0] == -1 && key_fd[1] == -1)
18598675Sdes		fatal("could not open any host key");
18698675Sdes
18798675Sdes	SSLeay_add_all_algorithms();
188106121Sdes	for (i = 0; i < 256; i++)
189106121Sdes		rnd[i] = arc4random();
190106121Sdes	RAND_seed(rnd, sizeof(rnd));
19198675Sdes
19298675Sdes	found = 0;
19398675Sdes	for (i = 0; i < 2; i++) {
19498675Sdes		keys[i] = NULL;
19598675Sdes		if (key_fd[i] == -1)
19698675Sdes			continue;
19798675Sdes		keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
19898675Sdes		    NULL, NULL);
19998675Sdes		close(key_fd[i]);
20098675Sdes		if (keys[i] != NULL)
20198675Sdes			found = 1;
20298675Sdes	}
20398675Sdes	if (!found)
20498675Sdes		fatal("no hostkey found");
20598675Sdes
20698675Sdes	buffer_init(&b);
207106121Sdes	if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
208106121Sdes		fatal("ssh_msg_recv failed");
20998675Sdes	if (buffer_get_char(&b) != version)
21098675Sdes		fatal("bad version");
21198675Sdes	fd = buffer_get_int(&b);
21298675Sdes	if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
21398675Sdes		fatal("bad fd");
21498675Sdes	if ((host = get_local_name(fd)) == NULL)
21598675Sdes		fatal("cannot get sockname for fd");
21698675Sdes
21798675Sdes	data = buffer_get_string(&b, &dlen);
21898675Sdes	if (valid_request(pw, host, &key, data, dlen) < 0)
21998675Sdes		fatal("not a valid request");
22098675Sdes	xfree(host);
22198675Sdes
22298675Sdes	found = 0;
22398675Sdes	for (i = 0; i < 2; i++) {
22498675Sdes		if (keys[i] != NULL &&
22598675Sdes		    key_equal(key, keys[i])) {
22698675Sdes			found = 1;
22798675Sdes			break;
22898675Sdes		}
22998675Sdes	}
23098675Sdes	if (!found)
23198675Sdes		fatal("no matching hostkey found");
23298675Sdes
23398675Sdes	if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
23498675Sdes		fatal("key_sign failed");
235106121Sdes	xfree(data);
23698675Sdes
23798675Sdes	/* send reply */
23898675Sdes	buffer_clear(&b);
23998675Sdes	buffer_put_string(&b, signature, slen);
240126274Sdes	if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1)
241126274Sdes		fatal("ssh_msg_send failed");
24298675Sdes
24398675Sdes	return (0);
24498675Sdes}
245