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