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Add support for certificate key types for users and hosts.

OpenSSH certificate key types are not X.509 certificates, but a much
simpler format that encodes a public key, identity information and
some validity constraints and signs it with a CA key. CA keys are
regular SSH keys. This certificate style avoids the attack surface
of X.509 certificates and is very easy to deploy.

Certified host keys allow automatic acceptance of new host keys
when a CA certificate is marked as trusted in ~/.ssh/known_hosts.
see VERIFYING HOST KEYS in ssh(1) for details.

Certified user keys allow authentication of users when the signing
CA key is marked as trusted in authorized_keys. See "AUTHORIZED_KEYS
FILE FORMAT" in sshd(8) for details.

Certificates are minted using ssh-keygen(1), documentation is in
the "CERTIFICATES" section of that manpage.

Documentation on the format of certificates is in the file
PROTOCOL.certkeys

feedback and ok markus@

/* $OpenBSD: ssh-add.c,v 1.93 2010/02/26 20:29:54 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Adds an identity to the authentication server, or removes an identity.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * SSH2 implementation,
 * Copyright (c) 2000, 2001 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 <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>

#include <openssl/evp.h>

#include <fcntl.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "xmalloc.h"
#include "ssh.h"
#include "rsa.h"
#include "log.h"
#include "key.h"
#include "buffer.h"
#include "authfd.h"
#include "authfile.h"
#include "pathnames.h"
#include "misc.h"

/* argv0 */
extern char *__progname;

/* Default files to add */
static char *default_files[] = {
	_PATH_SSH_CLIENT_ID_RSA,
	_PATH_SSH_CLIENT_ID_DSA,
	_PATH_SSH_CLIENT_IDENTITY,
	NULL
};

/* Default lifetime (0 == forever) */
static int lifetime = 0;

/* User has to confirm key use */
static int confirm = 0;

/* we keep a cache of one passphrases */
static char *pass = NULL;
static void
clear_pass(void)
{
	if (pass) {
		memset(pass, 0, strlen(pass));
		xfree(pass);
		pass = NULL;
	}
}

static int
delete_file(AuthenticationConnection *ac, const char *filename)
{
	Key *public;
	char *comment = NULL;
	int ret = -1;

	public = key_load_public(filename, &comment);
	if (public == NULL) {
		printf("Bad key file %s\n", filename);
		return -1;
	}
	if (ssh_remove_identity(ac, public)) {
		fprintf(stderr, "Identity removed: %s (%s)\n", filename, comment);
		ret = 0;
	} else
		fprintf(stderr, "Could not remove identity: %s\n", filename);

	key_free(public);
	xfree(comment);

	return ret;
}

/* Send a request to remove all identities. */
static int
delete_all(AuthenticationConnection *ac)
{
	int ret = -1;

	if (ssh_remove_all_identities(ac, 1))
		ret = 0;
	/* ignore error-code for ssh2 */
	ssh_remove_all_identities(ac, 2);

	if (ret == 0)
		fprintf(stderr, "All identities removed.\n");
	else
		fprintf(stderr, "Failed to remove all identities.\n");

	return ret;
}

static int
add_file(AuthenticationConnection *ac, const char *filename)
{
	Key *private, *cert;
	char *comment = NULL;
	char msg[1024], *certpath;
	int fd, perms_ok, ret = -1;

	if ((fd = open(filename, O_RDONLY)) < 0) {
		perror(filename);
		return -1;
	}

	/*
	 * Since we'll try to load a keyfile multiple times, permission errors
	 * will occur multiple times, so check perms first and bail if wrong.
	 */
	perms_ok = key_perm_ok(fd, filename);
	close(fd);
	if (!perms_ok)
		return -1;

	/* At first, try empty passphrase */
	private = key_load_private(filename, "", &comment);
	if (comment == NULL)
		comment = xstrdup(filename);
	/* try last */
	if (private == NULL && pass != NULL)
		private = key_load_private(filename, pass, NULL);
	if (private == NULL) {
		/* clear passphrase since it did not work */
		clear_pass();
		snprintf(msg, sizeof msg, "Enter passphrase for %.200s: ",
		    comment);
		for (;;) {
			pass = read_passphrase(msg, RP_ALLOW_STDIN);
			if (strcmp(pass, "") == 0) {
				clear_pass();
				xfree(comment);
				return -1;
			}
			private = key_load_private(filename, pass, &comment);
			if (private != NULL)
				break;
			clear_pass();
			snprintf(msg, sizeof msg,
			    "Bad passphrase, try again for %.200s: ", comment);
		}
	}

	if (ssh_add_identity_constrained(ac, private, comment, lifetime,
	    confirm)) {
		fprintf(stderr, "Identity added: %s (%s)\n", filename, comment);
		ret = 0;
		if (lifetime != 0)
			fprintf(stderr,
			    "Lifetime set to %d seconds\n", lifetime);
		if (confirm != 0)
			fprintf(stderr,
			    "The user has to confirm each use of the key\n");
	} else {
		fprintf(stderr, "Could not add identity: %s\n", filename);
	}


	/* Now try to add the certificate flavour too */
	xasprintf(&certpath, "%s-cert.pub", filename);
	if ((cert = key_load_public(certpath, NULL)) != NULL) {
		/* Graft with private bits */
		if (key_to_certified(private) != 0)
			fatal("%s: key_to_certified failed", __func__);
		key_cert_copy(cert, private);
		key_free(cert);

		if (ssh_add_identity_constrained(ac, private, comment,
		    lifetime, confirm)) {
			fprintf(stderr, "Certificate added: %s (%s)\n",
			    certpath, private->cert->key_id);
			if (lifetime != 0)
				fprintf(stderr, "Lifetime set to %d seconds\n",
				    lifetime);
			if (confirm != 0)
				fprintf(stderr, "The user has to confirm each "
				    "use of the key\n");
		} else {
			error("Certificate %s (%s) add failed", certpath,
			    private->cert->key_id);
		}
	} else
		fprintf(stderr, "Unable to load certificate %s", certpath);

	xfree(certpath);
	xfree(comment);
	key_free(private);

	return ret;
}

static int
update_card(AuthenticationConnection *ac, int add, const char *id)
{
	char *pin;
	int ret = -1;

	pin = read_passphrase("Enter passphrase for PKCS#11: ", RP_ALLOW_STDIN);
	if (pin == NULL)
		return -1;

	if (ssh_update_card(ac, add, id, pin, lifetime, confirm)) {
		fprintf(stderr, "Card %s: %s\n",
		    add ? "added" : "removed", id);
		ret = 0;
	} else {
		fprintf(stderr, "Could not %s card: %s\n",
		    add ? "add" : "remove", id);
		ret = -1;
	}
	xfree(pin);
	return ret;
}

static int
list_identities(AuthenticationConnection *ac, int do_fp)
{
	Key *key;
	char *comment, *fp;
	int had_identities = 0;
	int version;

	for (version = 1; version <= 2; version++) {
		for (key = ssh_get_first_identity(ac, &comment, version);
		    key != NULL;
		    key = ssh_get_next_identity(ac, &comment, version)) {
			had_identities = 1;
			if (do_fp) {
				fp = key_fingerprint(key, SSH_FP_MD5,
				    SSH_FP_HEX);
				printf("%d %s %s (%s)\n",
				    key_size(key), fp, comment, key_type(key));
				xfree(fp);
			} else {
				if (!key_write(key, stdout))
					fprintf(stderr, "key_write failed");
				fprintf(stdout, " %s\n", comment);
			}
			key_free(key);
			xfree(comment);
		}
	}
	if (!had_identities) {
		printf("The agent has no identities.\n");
		return -1;
	}
	return 0;
}

static int
lock_agent(AuthenticationConnection *ac, int lock)
{
	char prompt[100], *p1, *p2;
	int passok = 1, ret = -1;

	strlcpy(prompt, "Enter lock password: ", sizeof(prompt));
	p1 = read_passphrase(prompt, RP_ALLOW_STDIN);
	if (lock) {
		strlcpy(prompt, "Again: ", sizeof prompt);
		p2 = read_passphrase(prompt, RP_ALLOW_STDIN);
		if (strcmp(p1, p2) != 0) {
			fprintf(stderr, "Passwords do not match.\n");
			passok = 0;
		}
		memset(p2, 0, strlen(p2));
		xfree(p2);
	}
	if (passok && ssh_lock_agent(ac, lock, p1)) {
		fprintf(stderr, "Agent %slocked.\n", lock ? "" : "un");
		ret = 0;
	} else
		fprintf(stderr, "Failed to %slock agent.\n", lock ? "" : "un");
	memset(p1, 0, strlen(p1));
	xfree(p1);
	return (ret);
}

static int
do_file(AuthenticationConnection *ac, int deleting, char *file)
{
	if (deleting) {
		if (delete_file(ac, file) == -1)
			return -1;
	} else {
		if (add_file(ac, file) == -1)
			return -1;
	}
	return 0;
}

static void
usage(void)
{
	fprintf(stderr, "usage: %s [options] [file ...]\n", __progname);
	fprintf(stderr, "Options:\n");
	fprintf(stderr, "  -l          List fingerprints of all identities.\n");
	fprintf(stderr, "  -L          List public key parameters of all identities.\n");
	fprintf(stderr, "  -d          Delete identity.\n");
	fprintf(stderr, "  -D          Delete all identities.\n");
	fprintf(stderr, "  -x          Lock agent.\n");
	fprintf(stderr, "  -X          Unlock agent.\n");
	fprintf(stderr, "  -t life     Set lifetime (in seconds) when adding identities.\n");
	fprintf(stderr, "  -c          Require confirmation to sign using identities\n");
	fprintf(stderr, "  -s pkcs11   Add keys from PKCS#11 provider.\n");
	fprintf(stderr, "  -e pkcs11   Remove keys provided by PKCS#11 provider.\n");
}

int
main(int argc, char **argv)
{
	extern char *optarg;
	extern int optind;
	AuthenticationConnection *ac = NULL;
	char *pkcs11provider = NULL;
	int i, ch, deleting = 0, ret = 0;

	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
	sanitise_stdfd();

	SSLeay_add_all_algorithms();

	/* At first, get a connection to the authentication agent. */
	ac = ssh_get_authentication_connection();
	if (ac == NULL) {
		fprintf(stderr,
		    "Could not open a connection to your authentication agent.\n");
		exit(2);
	}
	while ((ch = getopt(argc, argv, "lLcdDxXe:s:t:")) != -1) {
		switch (ch) {
		case 'l':
		case 'L':
			if (list_identities(ac, ch == 'l' ? 1 : 0) == -1)
				ret = 1;
			goto done;
		case 'x':
		case 'X':
			if (lock_agent(ac, ch == 'x' ? 1 : 0) == -1)
				ret = 1;
			goto done;
		case 'c':
			confirm = 1;
			break;
		case 'd':
			deleting = 1;
			break;
		case 'D':
			if (delete_all(ac) == -1)
				ret = 1;
			goto done;
		case 's':
			pkcs11provider = optarg;
			break;
		case 'e':
			deleting = 1;
			pkcs11provider = optarg;
			break;
		case 't':
			if ((lifetime = convtime(optarg)) == -1) {
				fprintf(stderr, "Invalid lifetime\n");
				ret = 1;
				goto done;
			}
			break;
		default:
			usage();
			ret = 1;
			goto done;
		}
	}
	argc -= optind;
	argv += optind;
	if (pkcs11provider != NULL) {
		if (update_card(ac, !deleting, pkcs11provider) == -1)
			ret = 1;
		goto done;
	}
	if (argc == 0) {
		char buf[MAXPATHLEN];
		struct passwd *pw;
		struct stat st;
		int count = 0;

		if ((pw = getpwuid(getuid())) == NULL) {
			fprintf(stderr, "No user found with uid %u\n",
			    (u_int)getuid());
			ret = 1;
			goto done;
		}

		for (i = 0; default_files[i]; i++) {
			snprintf(buf, sizeof(buf), "%s/%s", pw->pw_dir,
			    default_files[i]);
			if (stat(buf, &st) < 0)
				continue;
			if (do_file(ac, deleting, buf) == -1)
				ret = 1;
			else
				count++;
		}
		if (count == 0)
			ret = 1;
	} else {
		for (i = 0; i < argc; i++) {
			if (do_file(ac, deleting, argv[i]) == -1)
				ret = 1;
		}
	}
	clear_pass();

done:
	ssh_close_authentication_connection(ac);
	return ret;
}