crypto/openssh-3.9p1/ssh-keysign.c

   1 /*
   2  * Copyright (c) 2002 Markus Friedl.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24 #include "includes.h"
  25 RCSID("$OpenBSD: ssh-keysign.c,v 1.16 2004/04/18 23:10:26 djm Exp $");
  26
  27 #include <openssl/evp.h>
  28 #include <openssl/rand.h>
  29 #include <openssl/rsa.h>
  30
  31 #include "log.h"
  32 #include "key.h"
  33 #include "ssh.h"
  34 #include "ssh2.h"
  35 #include "misc.h"
  36 #include "xmalloc.h"
  37 #include "buffer.h"
  38 #include "bufaux.h"
  39 #include "authfile.h"
  40 #include "msg.h"
  41 #include "canohost.h"
  42 #include "pathnames.h"
  43 #include "readconf.h"
  44 #include "uidswap.h"
  45
  46 /* XXX readconf.c needs these */
  47 uid_t original_real_uid;
  48
  49 extern char *__progname;
  50
  51 static int
  52 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
  53     u_int datalen)
  54 {
  55         Buffer b;
  56         Key *key = NULL;
  57         u_char *pkblob;
  58         u_int blen, len;
  59         char *pkalg, *p;
  60         int pktype, fail;
  61
  62         fail = 0;
  63
  64         buffer_init(&b);
  65         buffer_append(&b, data, datalen);
  66
  67         /* session id, currently limited to SHA1 (20 bytes) */
  68         p = buffer_get_string(&b, &len);
  69         if (len != 20)
  70                 fail++;
  71         xfree(p);
  72
  73         if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
  74                 fail++;
  75
  76         /* server user */
  77         buffer_skip_string(&b);
  78
  79         /* service */
  80         p = buffer_get_string(&b, NULL);
  81         if (strcmp("ssh-connection", p) != 0)
  82                 fail++;
  83         xfree(p);
  84
  85         /* method */
  86         p = buffer_get_string(&b, NULL);
  87         if (strcmp("hostbased", p) != 0)
  88                 fail++;
  89         xfree(p);
  90
  91         /* pubkey */
  92         pkalg = buffer_get_string(&b, NULL);
  93         pkblob = buffer_get_string(&b, &blen);
  94
  95         pktype = key_type_from_name(pkalg);
  96         if (pktype == KEY_UNSPEC)
  97                 fail++;
  98         else if ((key = key_from_blob(pkblob, blen)) == NULL)
  99                 fail++;
 100         else if (key->type != pktype)
 101                 fail++;
 102         xfree(pkalg);
 103         xfree(pkblob);
 104
 105         /* client host name, handle trailing dot */
 106         p = buffer_get_string(&b, &len);
 107         debug2("valid_request: check expect chost %s got %s", host, p);
 108         if (strlen(host) != len - 1)
 109                 fail++;
 110         else if (p[len - 1] != '.')
 111                 fail++;
 112         else if (strncasecmp(host, p, len - 1) != 0)
 113                 fail++;
 114         xfree(p);
 115
 116         /* local user */
 117         p = buffer_get_string(&b, NULL);
 118
 119         if (strcmp(pw->pw_name, p) != 0)
 120                 fail++;
 121         xfree(p);
 122
 123         /* end of message */
 124         if (buffer_len(&b) != 0)
 125                 fail++;
 126         buffer_free(&b);
 127
 128         debug3("valid_request: fail %d", fail);
 129
 130         if (fail && key != NULL)
 131                 key_free(key);
 132         else
 133                 *ret = key;
 134
 135         return (fail ? -1 : 0);
 136 }
 137
 138 int
 139 main(int argc, char **argv)
 140 {
 141         Buffer b;
 142         Options options;
 143         Key *keys[2], *key;
 144         struct passwd *pw;
 145         int key_fd[2], i, found, version = 2, fd;
 146         u_char *signature, *data;
 147         char *host;
 148         u_int slen, dlen;
 149         u_int32_t rnd[256];
 150
 151         key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
 152         key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
 153
 154         if ((pw = getpwuid(getuid())) == NULL)
 155                 fatal("getpwuid failed");
 156         pw = pwcopy(pw);
 157
 158         permanently_set_uid(pw);
 159
 160         init_rng();
 161         seed_rng();
 162         arc4random_stir();
 163
 164 #ifdef DEBUG_SSH_KEYSIGN
 165         log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
 166 #endif
 167
 168         /* verify that ssh-keysign is enabled by the admin */
 169         original_real_uid = getuid();   /* XXX readconf.c needs this */
 170         initialize_options(&options);
 171         (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0);
 172         fill_default_options(&options);
 173         if (options.enable_ssh_keysign != 1)
 174                 fatal("ssh-keysign not enabled in %s",
 175                     _PATH_HOST_CONFIG_FILE);
 176
 177         if (key_fd[0] == -1 && key_fd[1] == -1)
 178                 fatal("could not open any host key");
 179
 180         SSLeay_add_all_algorithms();
 181         for (i = 0; i < 256; i++)
 182                 rnd[i] = arc4random();
 183         RAND_seed(rnd, sizeof(rnd));
 184
 185         found = 0;
 186         for (i = 0; i < 2; i++) {
 187                 keys[i] = NULL;
 188                 if (key_fd[i] == -1)
 189                         continue;
 190                 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
 191                     NULL, NULL);
 192                 close(key_fd[i]);
 193                 if (keys[i] != NULL)
 194                         found = 1;
 195         }
 196         if (!found)
 197                 fatal("no hostkey found");
 198
 199         buffer_init(&b);
 200         if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
 201                 fatal("ssh_msg_recv failed");
 202         if (buffer_get_char(&b) != version)
 203                 fatal("bad version");
 204         fd = buffer_get_int(&b);
 205         if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
 206                 fatal("bad fd");
 207         if ((host = get_local_name(fd)) == NULL)
 208                 fatal("cannot get sockname for fd");
 209
 210         data = buffer_get_string(&b, &dlen);
 211         if (valid_request(pw, host, &key, data, dlen) < 0)
 212                 fatal("not a valid request");
 213         xfree(host);
 214
 215         found = 0;
 216         for (i = 0; i < 2; i++) {
 217                 if (keys[i] != NULL &&
 218                     key_equal(key, keys[i])) {
 219                         found = 1;
 220                         break;
 221                 }
 222         }
 223         if (!found)
 224                 fatal("no matching hostkey found");
 225
 226         if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
 227                 fatal("key_sign failed");
 228         xfree(data);
 229
 230         /* send reply */
 231         buffer_clear(&b);
 232         buffer_put_string(&b, signature, slen);
 233         if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1)
 234                 fatal("ssh_msg_send failed");
 235
 236         return (0);
 237 }