ssh-keysign.c - third_party/openssh-portable - Git at Google

 /* $OpenBSD: ssh-keysign.c,v 1.55 2018/07/27 05:34:42 dtucker Exp $ */
 /*
  * Copyright (c) 2002 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 <fcntl.h>
 #ifdef HAVE_PATHS_H
 #include <paths.h>
 #endif
 #include <pwd.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>

 #ifdef WITH_OPENSSL
 #include <openssl/evp.h>
 #include <openssl/rand.h>
 #include <openssl/rsa.h>
 #endif

 #include "xmalloc.h"
 #include "log.h"
 #include "sshkey.h"
 #include "ssh.h"
 #include "ssh2.h"
 #include "misc.h"
 #include "sshbuf.h"
 #include "authfile.h"
 #include "msg.h"
 #include "canohost.h"
 #include "pathnames.h"
 #include "readconf.h"
 #include "uidswap.h"
 #include "sshkey.h"
 #include "ssherr.h"

 struct ssh *active_state = NULL; /* XXX needed for linking */

 extern char *__progname;

 static int
 valid_request(struct passwd *pw, char *host, struct sshkey **ret,
     u_char *data, size_t datalen)
 {
 	struct sshbuf *b;
 	struct sshkey *key = NULL;
 	u_char type, *pkblob;
 	char *p;
 	size_t blen, len;
 	char *pkalg, *luser;
 	int r, pktype, fail;

 	if (ret != NULL)
 		*ret = NULL;
 	fail = 0;

 	if ((b = sshbuf_from(data, datalen)) == NULL)
 		fatal("%s: sshbuf_from failed", __func__);

 	/* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */
 	if ((r = sshbuf_get_string(b, NULL, &len)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 	if (len != 20 && len != 32)
 		fail++;

 	if ((r = sshbuf_get_u8(b, &type)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 	if (type != SSH2_MSG_USERAUTH_REQUEST)
 		fail++;

 	/* server user */
 	if ((r = sshbuf_skip_string(b)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));

 	/* service */
 	if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 	if (strcmp("ssh-connection", p) != 0)
 		fail++;
 	free(p);

 	/* method */
 	if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 	if (strcmp("hostbased", p) != 0)
 		fail++;
 	free(p);

 	/* pubkey */
 	if ((r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 ||
 	    (r = sshbuf_get_string(b, &pkblob, &blen)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));

 	pktype = sshkey_type_from_name(pkalg);
 	if (pktype == KEY_UNSPEC)
 		fail++;
 	else if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
 		error("%s: bad key blob: %s", __func__, ssh_err(r));
 		fail++;
 	} else if (key->type != pktype)
 		fail++;
 	free(pkalg);
 	free(pkblob);

 	/* client host name, handle trailing dot */
 	if ((r = sshbuf_get_cstring(b, &p, &len)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 	debug2("%s: check expect chost %s got %s", __func__, host, p);
 	if (strlen(host) != len - 1)
 		fail++;
 	else if (p[len - 1] != '.')
 		fail++;
 	else if (strncasecmp(host, p, len - 1) != 0)
 		fail++;
 	free(p);

 	/* local user */
 	if ((r = sshbuf_get_cstring(b, &luser, NULL)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));

 	if (strcmp(pw->pw_name, luser) != 0)
 		fail++;
 	free(luser);

 	/* end of message */
 	if (sshbuf_len(b) != 0)
 		fail++;
 	sshbuf_free(b);

 	debug3("%s: fail %d", __func__, fail);

 	if (fail)
 		sshkey_free(key);
 	else if (ret != NULL)
 		*ret = key;

 	return (fail ? -1 : 0);
 }

 int
 main(int argc, char **argv)
 {
 	struct sshbuf *b;
 	Options options;
 #define NUM_KEYTYPES 5
 	struct sshkey *keys[NUM_KEYTYPES], *key = NULL;
 	struct passwd *pw;
 	int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
 	u_char *signature, *data, rver;
 	char *host, *fp;
 	size_t slen, dlen;
 #ifdef WITH_OPENSSL
 	u_int32_t rnd[256];
 #endif

 	ssh_malloc_init();	/* must be called before any mallocs */
 	if (pledge("stdio rpath getpw dns id", NULL) != 0)
 		fatal("%s: pledge: %s", __progname, strerror(errno));

 	/* Ensure that stdin and stdout are connected */
 	if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
 		exit(1);
 	/* Leave /dev/null fd iff it is attached to stderr */
 	if (fd > 2)
 		close(fd);

 	i = 0;
 	/* XXX This really needs to read sshd_config for the paths */
 	key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
 	key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY);
 	key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY);
 	key_fd[i++] = open(_PATH_HOST_XMSS_KEY_FILE, O_RDONLY);
 	key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);

 	if ((pw = getpwuid(getuid())) == NULL)
 		fatal("getpwuid failed");
 	pw = pwcopy(pw);

 	permanently_set_uid(pw);

 	seed_rng();

 #ifdef DEBUG_SSH_KEYSIGN
 	log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
 #endif

 	/* verify that ssh-keysign is enabled by the admin */
 	initialize_options(&options);
 	(void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "", &options, 0);
 	fill_default_options(&options);
 	if (options.enable_ssh_keysign != 1)
 		fatal("ssh-keysign not enabled in %s",
 		    _PATH_HOST_CONFIG_FILE);

 	for (i = found = 0; i < NUM_KEYTYPES; i++) {
 		if (key_fd[i] != -1)
 			found = 1;
 	}
 	if (found == 0)
 		fatal("could not open any host key");

 #ifdef WITH_OPENSSL
 	OpenSSL_add_all_algorithms();
 	arc4random_buf(rnd, sizeof(rnd));
 	RAND_seed(rnd, sizeof(rnd));
 #endif

 	found = 0;
 	for (i = 0; i < NUM_KEYTYPES; i++) {
 		keys[i] = NULL;
 		if (key_fd[i] == -1)
 			continue;
 		r = sshkey_load_private_type_fd(key_fd[i], KEY_UNSPEC,
 		    NULL, &key, NULL);
 		close(key_fd[i]);
 		if (r != 0)
 			debug("parse key %d: %s", i, ssh_err(r));
 		else if (key != NULL) {
 			keys[i] = key;
 			found = 1;
 		}
 	}
 	if (!found)
 		fatal("no hostkey found");

 	if (pledge("stdio dns", NULL) != 0)
 		fatal("%s: pledge: %s", __progname, strerror(errno));

 	if ((b = sshbuf_new()) == NULL)
 		fatal("%s: sshbuf_new failed", __progname);
 	if (ssh_msg_recv(STDIN_FILENO, b) < 0)
 		fatal("ssh_msg_recv failed");
 	if ((r = sshbuf_get_u8(b, &rver)) != 0)
 		fatal("%s: buffer error: %s", __progname, ssh_err(r));
 	if (rver != version)
 		fatal("bad version: received %d, expected %d", rver, version);
 	if ((r = sshbuf_get_u32(b, (u_int *)&fd)) != 0)
 		fatal("%s: buffer error: %s", __progname, ssh_err(r));
 	if (fd < 0 || fd == STDIN_FILENO || fd == STDOUT_FILENO)
 		fatal("bad fd");
 	if ((host = get_local_name(fd)) == NULL)
 		fatal("cannot get local name for fd");

 	if ((r = sshbuf_get_string(b, &data, &dlen)) != 0)
 		fatal("%s: buffer error: %s", __progname, ssh_err(r));
 	if (valid_request(pw, host, &key, data, dlen) < 0)
 		fatal("not a valid request");
 	free(host);

 	found = 0;
 	for (i = 0; i < NUM_KEYTYPES; i++) {
 		if (keys[i] != NULL &&
 		    sshkey_equal_public(key, keys[i])) {
 			found = 1;
 			break;
 		}
 	}
 	if (!found) {
 		if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
 		    SSH_FP_DEFAULT)) == NULL)
 			fatal("%s: sshkey_fingerprint failed", __progname);
 		fatal("no matching hostkey found for key %s %s",
 		    sshkey_type(key), fp ? fp : "");
 	}

 	if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen, NULL, 0))
 	    != 0)
 		fatal("sshkey_sign failed: %s", ssh_err(r));
 	free(data);

 	/* send reply */
 	sshbuf_reset(b);
 	if ((r = sshbuf_put_string(b, signature, slen)) != 0)
 		fatal("%s: buffer error: %s", __progname, ssh_err(r));
 	if (ssh_msg_send(STDOUT_FILENO, version, b) == -1)
 		fatal("ssh_msg_send failed");

 	return (0);
 }
	/* $OpenBSD: ssh-keysign.c,v 1.55 2018/07/27 05:34:42 dtucker Exp $ */
	/*
	* Copyright (c) 2002 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 <fcntl.h>
	#ifdef HAVE_PATHS_H
	#include <paths.h>
	#endif
	#include <pwd.h>
	#include <stdarg.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <errno.h>

	#ifdef WITH_OPENSSL
	#include <openssl/evp.h>
	#include <openssl/rand.h>
	#include <openssl/rsa.h>
	#endif

	#include "xmalloc.h"
	#include "log.h"
	#include "sshkey.h"
	#include "ssh.h"
	#include "ssh2.h"
	#include "misc.h"
	#include "sshbuf.h"
	#include "authfile.h"
	#include "msg.h"
	#include "canohost.h"
	#include "pathnames.h"
	#include "readconf.h"
	#include "uidswap.h"
	#include "sshkey.h"
	#include "ssherr.h"

	struct ssh active_state = NULL; / XXX needed for linking */

	extern char *__progname;

	static int
	valid_request(struct passwd pw, char host, struct sshkey **ret,
	u_char *data, size_t datalen)
	{
	struct sshbuf *b;
	struct sshkey *key = NULL;
	u_char type, *pkblob;
	char *p;
	size_t blen, len;
	char pkalg, luser;
	int r, pktype, fail;

	if (ret != NULL)
	*ret = NULL;
	fail = 0;

	if ((b = sshbuf_from(data, datalen)) == NULL)
	fatal("%s: sshbuf_from failed", __func__);

	/* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */
	if ((r = sshbuf_get_string(b, NULL, &len)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (len != 20 && len != 32)
	fail++;

	if ((r = sshbuf_get_u8(b, &type)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (type != SSH2_MSG_USERAUTH_REQUEST)
	fail++;

	/* server user */
	if ((r = sshbuf_skip_string(b)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));

	/* service */
	if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (strcmp("ssh-connection", p) != 0)
	fail++;
	free(p);

	/* method */
	if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (strcmp("hostbased", p) != 0)
	fail++;
	free(p);

	/* pubkey */
	if ((r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 \|\|
	(r = sshbuf_get_string(b, &pkblob, &blen)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));

	pktype = sshkey_type_from_name(pkalg);
	if (pktype == KEY_UNSPEC)
	fail++;
	else if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
	error("%s: bad key blob: %s", __func__, ssh_err(r));
	fail++;
	} else if (key->type != pktype)
	fail++;
	free(pkalg);
	free(pkblob);

	/* client host name, handle trailing dot */
	if ((r = sshbuf_get_cstring(b, &p, &len)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));
	debug2("%s: check expect chost %s got %s", __func__, host, p);
	if (strlen(host) != len - 1)
	fail++;
	else if (p[len - 1] != '.')
	fail++;
	else if (strncasecmp(host, p, len - 1) != 0)
	fail++;
	free(p);

	/* local user */
	if ((r = sshbuf_get_cstring(b, &luser, NULL)) != 0)
	fatal("%s: buffer error: %s", __func__, ssh_err(r));

	if (strcmp(pw->pw_name, luser) != 0)
	fail++;
	free(luser);

	/* end of message */
	if (sshbuf_len(b) != 0)
	fail++;
	sshbuf_free(b);

	debug3("%s: fail %d", __func__, fail);

	if (fail)
	sshkey_free(key);
	else if (ret != NULL)
	*ret = key;

	return (fail ? -1 : 0);
	}

	int
	main(int argc, char **argv)
	{
	struct sshbuf *b;
	Options options;
	#define NUM_KEYTYPES 5
	struct sshkey keys[NUM_KEYTYPES], key = NULL;
	struct passwd *pw;
	int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
	u_char signature, data, rver;
	char host, fp;
	size_t slen, dlen;
	#ifdef WITH_OPENSSL
	u_int32_t rnd[256];
	#endif

	ssh_malloc_init(); /* must be called before any mallocs */
	if (pledge("stdio rpath getpw dns id", NULL) != 0)
	fatal("%s: pledge: %s", __progname, strerror(errno));

	/* Ensure that stdin and stdout are connected */
	if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
	exit(1);
	/* Leave /dev/null fd iff it is attached to stderr */
	if (fd > 2)
	close(fd);

	i = 0;
	/* XXX This really needs to read sshd_config for the paths */
	key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
	key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY);
	key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY);
	key_fd[i++] = open(_PATH_HOST_XMSS_KEY_FILE, O_RDONLY);
	key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);

	if ((pw = getpwuid(getuid())) == NULL)
	fatal("getpwuid failed");
	pw = pwcopy(pw);

	permanently_set_uid(pw);

	seed_rng();

	#ifdef DEBUG_SSH_KEYSIGN
	log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
	#endif

	/* verify that ssh-keysign is enabled by the admin */
	initialize_options(&options);
	(void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "", &options, 0);
	fill_default_options(&options);
	if (options.enable_ssh_keysign != 1)
	fatal("ssh-keysign not enabled in %s",
	_PATH_HOST_CONFIG_FILE);

	for (i = found = 0; i < NUM_KEYTYPES; i++) {
	if (key_fd[i] != -1)
	found = 1;
	}
	if (found == 0)
	fatal("could not open any host key");

	#ifdef WITH_OPENSSL
	OpenSSL_add_all_algorithms();
	arc4random_buf(rnd, sizeof(rnd));
	RAND_seed(rnd, sizeof(rnd));
	#endif

	found = 0;
	for (i = 0; i < NUM_KEYTYPES; i++) {
	keys[i] = NULL;
	if (key_fd[i] == -1)
	continue;
	r = sshkey_load_private_type_fd(key_fd[i], KEY_UNSPEC,
	NULL, &key, NULL);
	close(key_fd[i]);
	if (r != 0)
	debug("parse key %d: %s", i, ssh_err(r));
	else if (key != NULL) {
	keys[i] = key;
	found = 1;
	}
	}
	if (!found)
	fatal("no hostkey found");

	if (pledge("stdio dns", NULL) != 0)
	fatal("%s: pledge: %s", __progname, strerror(errno));

	if ((b = sshbuf_new()) == NULL)
	fatal("%s: sshbuf_new failed", __progname);
	if (ssh_msg_recv(STDIN_FILENO, b) < 0)
	fatal("ssh_msg_recv failed");
	if ((r = sshbuf_get_u8(b, &rver)) != 0)
	fatal("%s: buffer error: %s", __progname, ssh_err(r));
	if (rver != version)
	fatal("bad version: received %d, expected %d", rver, version);
	if ((r = sshbuf_get_u32(b, (u_int *)&fd)) != 0)
	fatal("%s: buffer error: %s", __progname, ssh_err(r));
	if (fd < 0 \|\| fd == STDIN_FILENO \|\| fd == STDOUT_FILENO)
	fatal("bad fd");
	if ((host = get_local_name(fd)) == NULL)
	fatal("cannot get local name for fd");

	if ((r = sshbuf_get_string(b, &data, &dlen)) != 0)
	fatal("%s: buffer error: %s", __progname, ssh_err(r));
	if (valid_request(pw, host, &key, data, dlen) < 0)
	fatal("not a valid request");
	free(host);

	found = 0;
	for (i = 0; i < NUM_KEYTYPES; i++) {
	if (keys[i] != NULL &&
	sshkey_equal_public(key, keys[i])) {
	found = 1;
	break;
	}
	}
	if (!found) {
	if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
	SSH_FP_DEFAULT)) == NULL)
	fatal("%s: sshkey_fingerprint failed", __progname);
	fatal("no matching hostkey found for key %s %s",
	sshkey_type(key), fp ? fp : "");
	}

	if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen, NULL, 0))
	!= 0)
	fatal("sshkey_sign failed: %s", ssh_err(r));
	free(data);

	/* send reply */
	sshbuf_reset(b);
	if ((r = sshbuf_put_string(b, signature, slen)) != 0)
	fatal("%s: buffer error: %s", __progname, ssh_err(r));
	if (ssh_msg_send(STDOUT_FILENO, version, b) == -1)
	fatal("ssh_msg_send failed");

	return (0);
	}