release/src/router/nettle/examples/rsa-decrypt.c

   1 /* rsa-decrypt.c
   2  *
   3  */
   4
   5 /* nettle, low-level cryptographics library
   6  *
   7  * Copyright (C) 2002 Niels Möller
   8  *
   9  * The nettle library is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU Lesser General Public License as published by
  11  * the Free Software Foundation; either version 2.1 of the License, or (at your
  12  * option) any later version.
  13  *
  14  * The nettle library is distributed in the hope that it will be useful, but
  15  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  16  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  17  * License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public License
  20  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  21  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  22  * MA 02111-1301, USA.
  23  */
  24
  25 #if HAVE_CONFIG_H
  26 # include "config.h"
  27 #endif
  28
  29 #include <ctype.h>
  30 #include <errno.h>
  31 #include <stdlib.h>
  32 #include <stdio.h>
  33 #include <string.h>
  34 #ifdef WIN32
  35 #include <fcntl.h>
  36 #endif
  37
  38 /* string.h must be included before gmp.h */
  39 #include "aes.h"
  40 #include "bignum.h"
  41 #include "buffer.h"
  42 #include "cbc.h"
  43 #include "hmac.h"
  44 #include "macros.h"
  45 #include "rsa.h"
  46 #include "yarrow.h"
  47
  48 #include "io.h"
  49 #include "rsa-session.h"
  50
  51 void
  52 rsa_session_set_decrypt_key(struct rsa_session *ctx,
  53                             const struct rsa_session_info *key)
  54 {
  55   const uint8_t *aes_key = SESSION_AES_KEY(key);
  56   const uint8_t *iv = SESSION_IV(key);
  57   const uint8_t *hmac_key = SESSION_HMAC_KEY(key);
  58
  59   aes_set_decrypt_key(&ctx->aes.ctx, AES_KEY_SIZE, aes_key);
  60   CBC_SET_IV(&ctx->aes, iv);
  61   hmac_sha1_set_key(&ctx->hmac, SHA1_DIGEST_SIZE, hmac_key);
  62 }
  63
  64 static int
  65 read_uint32(FILE *f, uint32_t *n)
  66 {
  67   uint8_t buf[4];
  68   if (fread(buf, 1, sizeof(buf), f) != sizeof(buf))
  69     return 0;
  70
  71   *n = READ_UINT32(buf);
  72   return 1;
  73 }
  74
  75 static int
  76 read_version(FILE *f)
  77 {
  78   uint32_t version;
  79   return read_uint32(f, &version) && version == RSA_VERSION;
  80 }
  81
  82 static int
  83 read_bignum(FILE *f, mpz_t x)
  84 {
  85   uint32_t size;
  86   if (read_uint32(f, &size)
  87       && size < 1000)
  88     {
  89       uint8_t *p = xalloc(size);
  90       if (fread(p, 1, size, f) != size)
  91         {
  92           free(p);
  93           return 0;
  94         }
  95
  96       nettle_mpz_set_str_256_u(x, size, p);
  97       free(p);
  98
  99       return 1;
 100     }
 101   return 0;
 102 }
 103
 104 struct process_ctx
 105 {
 106   struct CBC_CTX(struct aes_ctx, AES_BLOCK_SIZE) aes;
 107   struct hmac_sha1_ctx hmac;
 108   struct yarrow256_ctx yarrow;
 109 };
 110
 111 #define BUF_SIZE (100 * AES_BLOCK_SIZE)
 112
 113 /* Trailing data that needs special processing */
 114 #define BUF_FINAL (AES_BLOCK_SIZE + SHA1_DIGEST_SIZE)
 115
 116 static int
 117 process_file(struct rsa_session *ctx,
 118              FILE *in, FILE *out)
 119 {
 120   uint8_t buffer[BUF_SIZE + BUF_FINAL];
 121   uint8_t digest[SHA1_DIGEST_SIZE];
 122   size_t size;
 123   unsigned padding;
 124
 125   size = fread(buffer, 1, BUF_FINAL, in);
 126   if (size < BUF_FINAL)
 127     {
 128       if (ferror(in))
 129         werror("Reading input failed: %s\n", strerror(errno));
 130       else
 131         werror("Unexpected EOF on input.\n");
 132       return 0;
 133     }
 134
 135   do
 136     {
 137       size = fread(buffer + BUF_FINAL, 1, BUF_SIZE, in);
 138
 139       if (size < BUF_SIZE && ferror(in))
 140         {
 141           werror("Reading input failed: %s\n", strerror(errno));
 142           return 0;
 143         }
 144
 145       if (size % AES_BLOCK_SIZE != 0)
 146         {
 147           werror("Unexpected EOF on input.\n");
 148           return 0;
 149         }
 150
 151       if (size)
 152         {
 153           CBC_DECRYPT(&ctx->aes, aes_decrypt, size, buffer, buffer);
 154           hmac_sha1_update(&ctx->hmac, size, buffer);
 155           if (!write_string(out, size, buffer))
 156             {
 157               werror("Writing output failed: %s\n", strerror(errno));
 158               return 0;
 159             }
 160           memmove(buffer, buffer + size, BUF_FINAL);
 161         }
 162     }
 163   while (size == BUF_SIZE);
 164
 165   /* Decrypt final block */
 166   CBC_DECRYPT(&ctx->aes, aes_decrypt, AES_BLOCK_SIZE, buffer, buffer);
 167   padding = buffer[AES_BLOCK_SIZE - 1];
 168   if (padding > AES_BLOCK_SIZE)
 169     {
 170       werror("Decryption failed: Invalid padding.\n");
 171       return 0;
 172     }
 173
 174   if (padding < AES_BLOCK_SIZE)
 175     {
 176       unsigned leftover = AES_BLOCK_SIZE - padding;
 177       hmac_sha1_update(&ctx->hmac, leftover, buffer);
 178       if (!write_string(out, leftover, buffer))
 179         {
 180           werror("Writing output failed: %s\n", strerror(errno));
 181           return 0;
 182         }
 183     }
 184   hmac_sha1_digest(&ctx->hmac, SHA1_DIGEST_SIZE, digest);
 185   if (memcmp(digest, buffer + AES_BLOCK_SIZE, SHA1_DIGEST_SIZE) != 0)
 186     {
 187       werror("Decryption failed: Invalid mac.\n");
 188       return 0;
 189     }
 190
 191   return 1;
 192 }
 193
 194 int
 195 main(int argc, char **argv)
 196 {
 197   struct rsa_private_key key;
 198   struct rsa_session ctx;
 199   struct rsa_session_info session;
 200
 201   unsigned length;
 202   mpz_t x;
 203
 204   mpz_init(x);
 205
 206   if (argc != 2)
 207     {
 208       werror("Usage: rsa-decrypt PRIVATE-KEY < ciphertext\n");
 209       return EXIT_FAILURE;
 210     }
 211
 212   rsa_private_key_init(&key);
 213
 214   if (!read_rsa_key(argv[1], NULL, &key))
 215     {
 216       werror("Invalid key\n");
 217       return EXIT_FAILURE;
 218     }
 219
 220 #ifdef WIN32
 221   _setmode(0, O_BINARY);
 222   _setmode(1, O_BINARY);
 223 #endif
 224
 225   if (!read_version(stdin))
 226     {
 227       werror("Bad version number in input file.\n");
 228       return EXIT_FAILURE;
 229     }
 230
 231   if (!read_bignum(stdin, x))
 232     {
 233       werror("Bad rsa header in input file.\n");
 234       return EXIT_FAILURE;
 235     }
 236
 237   length = sizeof(session.key);
 238   if (!rsa_decrypt(&key, &length, session.key, x) || length != sizeof(session.key))
 239     {
 240       werror("Failed to decrypt rsa header in input file.\n");
 241       return EXIT_FAILURE;
 242     }
 243   mpz_clear(x);
 244
 245   rsa_session_set_decrypt_key(&ctx, &session);
 246
 247   if (!process_file(&ctx,
 248                     stdin, stdout))
 249     return EXIT_FAILURE;
 250
 251   rsa_private_key_clear(&key);
 252
 253   return EXIT_SUCCESS;
 254 }