ssh-keysign.c revision 215116
1215116Sdes/* $OpenBSD: ssh-keysign.c,v 1.32 2010/08/04 06:08:40 djm Exp $ */ 298675Sdes/* 398675Sdes * Copyright (c) 2002 Markus Friedl. All rights reserved. 498675Sdes * 598675Sdes * Redistribution and use in source and binary forms, with or without 698675Sdes * modification, are permitted provided that the following conditions 798675Sdes * are met: 898675Sdes * 1. Redistributions of source code must retain the above copyright 998675Sdes * notice, this list of conditions and the following disclaimer. 1098675Sdes * 2. Redistributions in binary form must reproduce the above copyright 1198675Sdes * notice, this list of conditions and the following disclaimer in the 1298675Sdes * documentation and/or other materials provided with the distribution. 1398675Sdes * 1498675Sdes * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 1598675Sdes * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 1698675Sdes * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 1798675Sdes * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 1898675Sdes * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 1998675Sdes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 2098675Sdes * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 2198675Sdes * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 2298675Sdes * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 2398675Sdes * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 2498675Sdes */ 25162852Sdes 2698675Sdes#include "includes.h" 2798675Sdes 28162852Sdes#include <fcntl.h> 29162852Sdes#ifdef HAVE_PATHS_H 30162852Sdes#include <paths.h> 31162852Sdes#endif 32162852Sdes#include <pwd.h> 33162852Sdes#include <stdarg.h> 34162852Sdes#include <stdlib.h> 35162852Sdes#include <string.h> 36162852Sdes#include <unistd.h> 37162852Sdes 3898675Sdes#include <openssl/evp.h> 39106121Sdes#include <openssl/rand.h> 40106121Sdes#include <openssl/rsa.h> 4198675Sdes 42162852Sdes#include "xmalloc.h" 4398675Sdes#include "log.h" 4498675Sdes#include "key.h" 45106121Sdes#include "ssh.h" 4698675Sdes#include "ssh2.h" 4798675Sdes#include "misc.h" 4898675Sdes#include "buffer.h" 4998675Sdes#include "authfile.h" 5098675Sdes#include "msg.h" 5198675Sdes#include "canohost.h" 5298675Sdes#include "pathnames.h" 53106121Sdes#include "readconf.h" 54137015Sdes#include "uidswap.h" 5598675Sdes 56124208Sdes/* XXX readconf.c needs these */ 57124208Sdesuid_t original_real_uid; 58106121Sdes 5998937Sdesextern char *__progname; 6098937Sdes 6198675Sdesstatic int 6298675Sdesvalid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 6398675Sdes u_int datalen) 6498675Sdes{ 6598675Sdes Buffer b; 66124208Sdes Key *key = NULL; 6798675Sdes u_char *pkblob; 6898675Sdes u_int blen, len; 6998675Sdes char *pkalg, *p; 7098675Sdes int pktype, fail; 7198675Sdes 7298675Sdes fail = 0; 7398675Sdes 7498675Sdes buffer_init(&b); 7598675Sdes buffer_append(&b, data, datalen); 7698675Sdes 77162852Sdes /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ 7898675Sdes p = buffer_get_string(&b, &len); 79162852Sdes if (len != 20 && len != 32) 8098675Sdes fail++; 8198675Sdes xfree(p); 8298675Sdes 8398675Sdes if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 8498675Sdes fail++; 8598675Sdes 8698675Sdes /* server user */ 8798675Sdes buffer_skip_string(&b); 8898675Sdes 8998675Sdes /* service */ 9098675Sdes p = buffer_get_string(&b, NULL); 9198675Sdes if (strcmp("ssh-connection", p) != 0) 9298675Sdes fail++; 9398675Sdes xfree(p); 9498675Sdes 9598675Sdes /* method */ 9698675Sdes p = buffer_get_string(&b, NULL); 9798675Sdes if (strcmp("hostbased", p) != 0) 9898675Sdes fail++; 9998675Sdes xfree(p); 10098675Sdes 10198675Sdes /* pubkey */ 10298675Sdes pkalg = buffer_get_string(&b, NULL); 10398675Sdes pkblob = buffer_get_string(&b, &blen); 10498675Sdes 10598675Sdes pktype = key_type_from_name(pkalg); 10698675Sdes if (pktype == KEY_UNSPEC) 10798675Sdes fail++; 10898675Sdes else if ((key = key_from_blob(pkblob, blen)) == NULL) 10998675Sdes fail++; 11098675Sdes else if (key->type != pktype) 11198675Sdes fail++; 11298675Sdes xfree(pkalg); 11398675Sdes xfree(pkblob); 11498675Sdes 11598675Sdes /* client host name, handle trailing dot */ 11698675Sdes p = buffer_get_string(&b, &len); 11798675Sdes debug2("valid_request: check expect chost %s got %s", host, p); 11898675Sdes if (strlen(host) != len - 1) 11998675Sdes fail++; 12098675Sdes else if (p[len - 1] != '.') 12198675Sdes fail++; 12298675Sdes else if (strncasecmp(host, p, len - 1) != 0) 12398675Sdes fail++; 12498675Sdes xfree(p); 12598675Sdes 12698675Sdes /* local user */ 12798675Sdes p = buffer_get_string(&b, NULL); 12898675Sdes 12998675Sdes if (strcmp(pw->pw_name, p) != 0) 13098675Sdes fail++; 13198675Sdes xfree(p); 13298675Sdes 13398675Sdes /* end of message */ 13498675Sdes if (buffer_len(&b) != 0) 13598675Sdes fail++; 136126274Sdes buffer_free(&b); 13798675Sdes 13898675Sdes debug3("valid_request: fail %d", fail); 13998675Sdes 14098675Sdes if (fail && key != NULL) 14198675Sdes key_free(key); 14298675Sdes else 14398675Sdes *ret = key; 14498675Sdes 14598675Sdes return (fail ? -1 : 0); 14698675Sdes} 14798675Sdes 14898675Sdesint 14998675Sdesmain(int argc, char **argv) 15098675Sdes{ 15198675Sdes Buffer b; 152106121Sdes Options options; 153162852Sdes Key *keys[2], *key = NULL; 15498675Sdes struct passwd *pw; 15598675Sdes int key_fd[2], i, found, version = 2, fd; 15698675Sdes u_char *signature, *data; 15798675Sdes char *host; 15898675Sdes u_int slen, dlen; 159106121Sdes u_int32_t rnd[256]; 16098675Sdes 161157016Sdes /* Ensure that stdin and stdout are connected */ 162157016Sdes if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) 163157016Sdes exit(1); 164157016Sdes /* Leave /dev/null fd iff it is attached to stderr */ 165157016Sdes if (fd > 2) 166157016Sdes close(fd); 167157016Sdes 16898675Sdes key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 16998675Sdes key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 17098675Sdes 171146998Sdes original_real_uid = getuid(); /* XXX readconf.c needs this */ 172146998Sdes if ((pw = getpwuid(original_real_uid)) == NULL) 173137015Sdes fatal("getpwuid failed"); 174137015Sdes pw = pwcopy(pw); 17598675Sdes 176137015Sdes permanently_set_uid(pw); 177137015Sdes 17898937Sdes init_rng(); 17998937Sdes seed_rng(); 18098937Sdes arc4random_stir(); 18198937Sdes 18298675Sdes#ifdef DEBUG_SSH_KEYSIGN 18398675Sdes log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 18498675Sdes#endif 18598675Sdes 186106121Sdes /* verify that ssh-keysign is enabled by the admin */ 187106121Sdes initialize_options(&options); 188137015Sdes (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); 189106121Sdes fill_default_options(&options); 190113908Sdes if (options.enable_ssh_keysign != 1) 191113908Sdes fatal("ssh-keysign not enabled in %s", 192106121Sdes _PATH_HOST_CONFIG_FILE); 193106121Sdes 19498675Sdes if (key_fd[0] == -1 && key_fd[1] == -1) 19598675Sdes fatal("could not open any host key"); 19698675Sdes 19798675Sdes SSLeay_add_all_algorithms(); 198106121Sdes for (i = 0; i < 256; i++) 199106121Sdes rnd[i] = arc4random(); 200106121Sdes RAND_seed(rnd, sizeof(rnd)); 20198675Sdes 20298675Sdes found = 0; 20398675Sdes for (i = 0; i < 2; i++) { 20498675Sdes keys[i] = NULL; 20598675Sdes if (key_fd[i] == -1) 20698675Sdes continue; 20798675Sdes keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 20898675Sdes NULL, NULL); 20998675Sdes close(key_fd[i]); 21098675Sdes if (keys[i] != NULL) 21198675Sdes found = 1; 21298675Sdes } 21398675Sdes if (!found) 21498675Sdes fatal("no hostkey found"); 21598675Sdes 21698675Sdes buffer_init(&b); 217106121Sdes if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 218106121Sdes fatal("ssh_msg_recv failed"); 21998675Sdes if (buffer_get_char(&b) != version) 22098675Sdes fatal("bad version"); 22198675Sdes fd = buffer_get_int(&b); 22298675Sdes if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 22398675Sdes fatal("bad fd"); 22498675Sdes if ((host = get_local_name(fd)) == NULL) 225204917Sdes fatal("cannot get local name for fd"); 22698675Sdes 22798675Sdes data = buffer_get_string(&b, &dlen); 22898675Sdes if (valid_request(pw, host, &key, data, dlen) < 0) 22998675Sdes fatal("not a valid request"); 23098675Sdes xfree(host); 23198675Sdes 23298675Sdes found = 0; 23398675Sdes for (i = 0; i < 2; i++) { 23498675Sdes if (keys[i] != NULL && 235215116Sdes key_equal_public(key, keys[i])) { 23698675Sdes found = 1; 23798675Sdes break; 23898675Sdes } 23998675Sdes } 24098675Sdes if (!found) 24198675Sdes fatal("no matching hostkey found"); 24298675Sdes 24398675Sdes if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 24498675Sdes fatal("key_sign failed"); 245106121Sdes xfree(data); 24698675Sdes 24798675Sdes /* send reply */ 24898675Sdes buffer_clear(&b); 24998675Sdes buffer_put_string(&b, signature, slen); 250126274Sdes if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 251126274Sdes fatal("ssh_msg_send failed"); 25298675Sdes 25398675Sdes return (0); 25498675Sdes} 255