source: trunk/third/openssh/ssh-keysign.c @ 18759

/*
 * 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"
RCSID("$OpenBSD: ssh-keysign.c,v 1.7 2002/07/03 14:21:05 markus Exp $");

#include <openssl/evp.h>
#include <openssl/rand.h>
#include <openssl/rsa.h>

#include "log.h"
#include "key.h"
#include "ssh.h"
#include "ssh2.h"
#include "misc.h"
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "authfile.h"
#include "msg.h"
#include "canohost.h"
#include "pathnames.h"
#include "readconf.h"

uid_t original_real_uid;        /* XXX readconf.c needs this */

#ifdef HAVE___PROGNAME
extern char *__progname;
#else
char *__progname;
#endif

static int
valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
    u_int datalen)
{
        Buffer b;
        Key *key;
        u_char *pkblob;
        u_int blen, len;
        char *pkalg, *p;
        int pktype, fail;

        fail = 0;

        buffer_init(&b);
        buffer_append(&b, data, datalen);

        /* session id, currently limited to SHA1 (20 bytes) */
        p = buffer_get_string(&b, &len);
        if (len != 20)
                fail++;
        xfree(p);

        if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
                fail++;

        /* server user */
        buffer_skip_string(&b);

        /* service */
        p = buffer_get_string(&b, NULL);
        if (strcmp("ssh-connection", p) != 0)
                fail++;
        xfree(p);

        /* method */
        p = buffer_get_string(&b, NULL);
        if (strcmp("hostbased", p) != 0)
                fail++;
        xfree(p);

        /* pubkey */
        pkalg = buffer_get_string(&b, NULL);
        pkblob = buffer_get_string(&b, &blen);

        pktype = key_type_from_name(pkalg);
        if (pktype == KEY_UNSPEC)
                fail++;
        else if ((key = key_from_blob(pkblob, blen)) == NULL)
                fail++;
        else if (key->type != pktype)
                fail++;
        xfree(pkalg);
        xfree(pkblob);

        /* client host name, handle trailing dot */
        p = buffer_get_string(&b, &len);
        debug2("valid_request: check expect chost %s got %s", host, p);
        if (strlen(host) != len - 1)
                fail++;
        else if (p[len - 1] != '.')
                fail++;
        else if (strncasecmp(host, p, len - 1) != 0)
                fail++;
        xfree(p);

        /* local user */
        p = buffer_get_string(&b, NULL);

        if (strcmp(pw->pw_name, p) != 0)
                fail++;
        xfree(p);

        /* end of message */
        if (buffer_len(&b) != 0)
                fail++;

        debug3("valid_request: fail %d", fail);

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

        return (fail ? -1 : 0);
}

int
main(int argc, char **argv)
{
        Buffer b;
        Options options;
        Key *keys[2], *key;
        struct passwd *pw;
        int key_fd[2], i, found, version = 2, fd;
        u_char *signature, *data;
        char *host;
        u_int slen, dlen;
        u_int32_t rnd[256];

        key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
        key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);

        seteuid(getuid());
        setuid(getuid());

        init_rng();
        seed_rng();
        arc4random_stir();

#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 */
        original_real_uid = getuid();   /* XXX readconf.c needs this */
        initialize_options(&options);
        (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options);
        fill_default_options(&options);
        if (options.hostbased_authentication != 1)
                fatal("Hostbased authentication not enabled in %s",
                    _PATH_HOST_CONFIG_FILE);

        if (key_fd[0] == -1 && key_fd[1] == -1)
                fatal("could not open any host key");

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

        SSLeay_add_all_algorithms();
        for (i = 0; i < 256; i++)
                rnd[i] = arc4random();
        RAND_seed(rnd, sizeof(rnd));

        found = 0;
        for (i = 0; i < 2; i++) {
                keys[i] = NULL;
                if (key_fd[i] == -1)
                        continue;
                keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
                    NULL, NULL);
                close(key_fd[i]);
                if (keys[i] != NULL && keys[i]->type == KEY_RSA) {
                        if (RSA_blinding_on(keys[i]->rsa, NULL) != 1) {
                                error("RSA_blinding_on failed");
                                key_free(keys[i]);
                                keys[i] = NULL;
                        }
                }
                if (keys[i] != NULL)
                        found = 1;
        }
        if (!found)
                fatal("no hostkey found");

        buffer_init(&b);
        if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
                fatal("ssh_msg_recv failed");
        if (buffer_get_char(&b) != version)
                fatal("bad version");
        fd = buffer_get_int(&b);
        if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
                fatal("bad fd");
        if ((host = get_local_name(fd)) == NULL)
                fatal("cannot get sockname for fd");

        data = buffer_get_string(&b, &dlen);
        if (valid_request(pw, host, &key, data, dlen) < 0)
                fatal("not a valid request");
        xfree(host);

        found = 0;
        for (i = 0; i < 2; i++) {
                if (keys[i] != NULL &&
                    key_equal(key, keys[i])) {
                        found = 1;
                        break;
                }
        }
        if (!found)
                fatal("no matching hostkey found");

        if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
                fatal("key_sign failed");
        xfree(data);

        /* send reply */
        buffer_clear(&b);
        buffer_put_string(&b, signature, slen);
        ssh_msg_send(STDOUT_FILENO, version, &b);

        return (0);
}