mcs/class/corlib/Mono.Security.Cryptography/PKCS1.cs

   1 //
   2 // PKCS1.cs - Implements PKCS#1 primitives.
   3 //
   4 // Author:
   5 //      Sebastien Pouliot <sebastien@ximian.com>
   6 //
   7 // (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
   8 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 using System;
  31 using System.Security.Cryptography;
  32
  33 namespace Mono.Security.Cryptography {
  34
  35         // References:
  36         // a.   PKCS#1: RSA Cryptography Standard
  37         //      http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/index.html
  38
  39 #if INSIDE_CORLIB
  40         internal
  41 #else
  42         public
  43 #endif
  44         sealed class PKCS1 {
  45
  46                 private PKCS1 ()
  47                 {
  48                 }
  49
  50                 private static bool Compare (byte[] array1, byte[] array2)
  51                 {
  52                         bool result = (array1.Length == array2.Length);
  53                         if (result) {
  54                                 for (int i=0; i < array1.Length; i++)
  55                                         if (array1[i] != array2[i])
  56                                                 return false;
  57                         }
  58                         return result;
  59                 }
  60
  61                 private static byte[] xor (byte[] array1, byte[] array2)
  62                 {
  63                         byte[] result = new byte [array1.Length];
  64                         for (int i=0; i < result.Length; i++)
  65                                 result[i] = (byte) (array1[i] ^ array2[i]);
  66                         return result;
  67                 }
  68
  69                 private static byte[] emptySHA1   = { 0xda, 0x39, 0xa3, 0xee, 0x5e, 0x6b, 0x4b, 0x0d, 0x32, 0x55, 0xbf, 0xef, 0x95, 0x60, 0x18, 0x90, 0xaf, 0xd8, 0x07, 0x09 };
  70                 private static byte[] emptySHA256 = { 0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c, 0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55 };
  71                 private static byte[] emptySHA384 = { 0x38, 0xb0, 0x60, 0xa7, 0x51, 0xac, 0x96, 0x38, 0x4c, 0xd9, 0x32, 0x7e, 0xb1, 0xb1, 0xe3, 0x6a, 0x21, 0xfd, 0xb7, 0x11, 0x14, 0xbe, 0x07, 0x43, 0x4c, 0x0c, 0xc7, 0xbf, 0x63, 0xf6, 0xe1, 0xda, 0x27, 0x4e, 0xde, 0xbf, 0xe7, 0x6f, 0x65, 0xfb, 0xd5, 0x1a, 0xd2, 0xf1, 0x48, 0x98, 0xb9, 0x5b };
  72                 private static byte[] emptySHA512 = { 0xcf, 0x83, 0xe1, 0x35, 0x7e, 0xef, 0xb8, 0xbd, 0xf1, 0x54, 0x28, 0x50, 0xd6, 0x6d, 0x80, 0x07, 0xd6, 0x20, 0xe4, 0x05, 0x0b, 0x57, 0x15, 0xdc, 0x83, 0xf4, 0xa9, 0x21, 0xd3, 0x6c, 0xe9, 0xce, 0x47, 0xd0, 0xd1, 0x3c, 0x5d, 0x85, 0xf2, 0xb0, 0xff, 0x83, 0x18, 0xd2, 0x87, 0x7e, 0xec, 0x2f, 0x63, 0xb9, 0x31, 0xbd, 0x47, 0x41, 0x7a, 0x81, 0xa5, 0x38, 0x32, 0x7a, 0xf9, 0x27, 0xda, 0x3e };
  73
  74                 private static byte[] GetEmptyHash (HashAlgorithm hash)
  75                 {
  76                         if (hash is SHA1)
  77                                 return emptySHA1;
  78                         else if (hash is SHA256)
  79                                 return emptySHA256;
  80                         else if (hash is SHA384)
  81                                 return emptySHA384;
  82                         else if (hash is SHA512)
  83                                 return emptySHA512;
  84                         else
  85                                 return hash.ComputeHash ((byte[])null);
  86                 }
  87
  88                 // PKCS #1 v.2.1, Section 4.1
  89                 // I2OSP converts a non-negative integer to an octet string of a specified length.
  90                 public static byte[] I2OSP (int x, int size)
  91                 {
  92                         byte[] array = BitConverterLE.GetBytes (x);
  93                         Array.Reverse (array, 0, array.Length);
  94                         return I2OSP (array, size);
  95                 }
  96
  97                 public static byte[] I2OSP (byte[] x, int size)
  98                 {
  99                         byte[] result = new byte [size];
 100                         Buffer.BlockCopy (x, 0, result, (result.Length - x.Length), x.Length);
 101                         return result;
 102                 }
 103
 104                 // PKCS #1 v.2.1, Section 4.2
 105                 // OS2IP converts an octet string to a nonnegative integer.
 106                 public static byte[] OS2IP (byte[] x)
 107                 {
 108                         int i = 0;
 109                         while ((x [i++] == 0x00) && (i < x.Length)) {
 110                                 // confuse compiler into reporting a warning with {}
 111                         }
 112                         i--;
 113                         if (i > 0) {
 114                                 byte[] result = new byte [x.Length - i];
 115                                 Buffer.BlockCopy (x, i, result, 0, result.Length);
 116                                 return result;
 117                         }
 118                         else
 119                                 return x;
 120                 }
 121
 122                 // PKCS #1 v.2.1, Section 5.1.1
 123                 public static byte[] RSAEP (RSA rsa, byte[] m)
 124                 {
 125                         // c = m^e mod n
 126                         return rsa.EncryptValue (m);
 127                 }
 128
 129                 // PKCS #1 v.2.1, Section 5.1.2
 130                 public static byte[] RSADP (RSA rsa, byte[] c)
 131                 {
 132                         // m = c^d mod n
 133                         // Decrypt value may apply CRT optimizations
 134                         return rsa.DecryptValue (c);
 135                 }
 136
 137                 // PKCS #1 v.2.1, Section 5.2.1
 138                 public static byte[] RSASP1 (RSA rsa, byte[] m)
 139                 {
 140                         // first form: s = m^d mod n
 141                         // Decrypt value may apply CRT optimizations
 142                         return rsa.DecryptValue (m);
 143                 }
 144
 145                 // PKCS #1 v.2.1, Section 5.2.2
 146                 public static byte[] RSAVP1 (RSA rsa, byte[] s)
 147                 {
 148                         // m = s^e mod n
 149                         return rsa.EncryptValue (s);
 150                 }
 151
 152                 // PKCS #1 v.2.1, Section 7.1.1
 153                 // RSAES-OAEP-ENCRYPT ((n, e), M, L)
 154                 public static byte[] Encrypt_OAEP (RSA rsa, HashAlgorithm hash, RandomNumberGenerator rng, byte[] M)
 155                 {
 156                         int size = rsa.KeySize / 8;
 157                         int hLen = hash.HashSize / 8;
 158                         if (M.Length > size - 2 * hLen - 2)
 159                                 throw new CryptographicException ("message too long");
 160                         // empty label L SHA1 hash
 161                         byte[] lHash = GetEmptyHash (hash);
 162                         int PSLength = (size - M.Length - 2 * hLen - 2);
 163                         // DB = lHash || PS || 0x01 || M
 164                         byte[] DB = new byte [lHash.Length + PSLength + 1 + M.Length];
 165                         Buffer.BlockCopy (lHash, 0, DB, 0, lHash.Length);
 166                         DB [(lHash.Length + PSLength)] = 0x01;
 167                         Buffer.BlockCopy (M, 0, DB, (DB.Length - M.Length), M.Length);
 168
 169                         byte[] seed = new byte [hLen];
 170                         rng.GetBytes (seed);
 171
 172                         byte[] dbMask = MGF1 (hash, seed, size - hLen - 1);
 173                         byte[] maskedDB = xor (DB, dbMask);
 174                         byte[] seedMask = MGF1 (hash, maskedDB, hLen);
 175                         byte[] maskedSeed = xor (seed, seedMask);
 176                         // EM = 0x00 || maskedSeed || maskedDB
 177                         byte[] EM = new byte [maskedSeed.Length + maskedDB.Length + 1];
 178                         Buffer.BlockCopy (maskedSeed, 0, EM, 1, maskedSeed.Length);
 179                         Buffer.BlockCopy (maskedDB, 0, EM, maskedSeed.Length + 1, maskedDB.Length);
 180
 181                         byte[] m = OS2IP (EM);
 182                         byte[] c = RSAEP (rsa, m);
 183                         return I2OSP (c, size);
 184                 }
 185
 186                 // PKCS #1 v.2.1, Section 7.1.2
 187                 // RSAES-OAEP-DECRYPT (K, C, L)
 188                 public static byte[] Decrypt_OAEP (RSA rsa, HashAlgorithm hash, byte[] C)
 189                 {
 190                         int size = rsa.KeySize / 8;
 191                         int hLen = hash.HashSize / 8;
 192                         if ((size < (2 * hLen + 2)) || (C.Length != size))
 193                                 throw new CryptographicException ("decryption error");
 194
 195                         byte[] c = OS2IP (C);
 196                         byte[] m = RSADP (rsa, c);
 197                         byte[] EM = I2OSP (m, size);
 198
 199                         // split EM = Y || maskedSeed || maskedDB
 200                         byte[] maskedSeed = new byte [hLen];
 201                         Buffer.BlockCopy (EM, 1, maskedSeed, 0, maskedSeed.Length);
 202                         byte[] maskedDB = new byte [size - hLen - 1];
 203                         Buffer.BlockCopy (EM, (EM.Length - maskedDB.Length), maskedDB, 0, maskedDB.Length);
 204
 205                         byte[] seedMask = MGF1 (hash, maskedDB, hLen);
 206                         byte[] seed = xor (maskedSeed, seedMask);
 207                         byte[] dbMask = MGF1 (hash, seed, size - hLen - 1);
 208                         byte[] DB = xor (maskedDB, dbMask);
 209
 210                         byte[] lHash = GetEmptyHash (hash);
 211                         // split DB = lHash' || PS || 0x01 || M
 212                         byte[] dbHash = new byte [lHash.Length];
 213                         Buffer.BlockCopy (DB, 0, dbHash, 0, dbHash.Length);
 214                         bool h = Compare (lHash, dbHash);
 215
 216                         // find separator 0x01
 217                         int nPos = lHash.Length;
 218                         while (DB[nPos] == 0)
 219                                 nPos++;
 220
 221                         int Msize = DB.Length - nPos - 1;
 222                         byte[] M = new byte [Msize];
 223                         Buffer.BlockCopy (DB, (nPos + 1), M, 0, Msize);
 224
 225                         // we could have returned EM[0] sooner but would be helping a timing attack
 226                         if ((EM[0] != 0) || (!h) || (DB[nPos] != 0x01))
 227                                 return null;
 228                         return M;
 229                 }
 230
 231                 // PKCS #1 v.2.1, Section 7.2.1
 232                 // RSAES-PKCS1-V1_5-ENCRYPT ((n, e), M)
 233                 public static byte[] Encrypt_v15 (RSA rsa, RandomNumberGenerator rng, byte[] M)
 234                 {
 235                         int size = rsa.KeySize / 8;
 236                         if (M.Length > size - 11)
 237                                 throw new CryptographicException ("message too long");
 238                         int PSLength = System.Math.Max (8, (size - M.Length - 3));
 239                         byte[] PS = new byte [PSLength];
 240                         rng.GetNonZeroBytes (PS);
 241                         byte[] EM = new byte [size];
 242                         EM [1] = 0x02;
 243                         Buffer.BlockCopy (PS, 0, EM, 2, PSLength);
 244                         Buffer.BlockCopy (M, 0, EM, (size - M.Length), M.Length);
 245
 246                         byte[] m = OS2IP (EM);
 247                         byte[] c = RSAEP (rsa, m);
 248                         byte[] C = I2OSP (c, size);
 249                         return C;
 250                 }
 251
 252                 // PKCS #1 v.2.1, Section 7.2.2
 253                 // RSAES-PKCS1-V1_5-DECRYPT (K, C)
 254                 public static byte[] Decrypt_v15 (RSA rsa, byte[] C)
 255                 {
 256                         int size = rsa.KeySize / 8;
 257                         if ((size < 11) || (C.Length != size))
 258                                 throw new CryptographicException ("decryption error");
 259                         byte[] c = OS2IP (C);
 260                         byte[] m = RSADP (rsa, c);
 261                         byte[] EM = I2OSP (m, size);
 262
 263                         if ((EM [0] != 0x00) || (EM [1] != 0x02))
 264                                 return null;
 265
 266                         int mPos = 10;
 267                         // PS is a minimum of 8 bytes + 2 bytes for header
 268                         while ((EM [mPos] != 0x00) && (mPos < EM.Length))
 269                                 mPos++;
 270                         if (EM [mPos] != 0x00)
 271                                 return null;
 272                         mPos++;
 273                         byte[] M = new byte [EM.Length - mPos];
 274                         Buffer.BlockCopy (EM, mPos, M, 0, M.Length);
 275                         return M;
 276                 }
 277
 278                 // PKCS #1 v.2.1, Section 8.2.1
 279                 // RSASSA-PKCS1-V1_5-SIGN (K, M)
 280                 public static byte[] Sign_v15 (RSA rsa, HashAlgorithm hash, byte[] hashValue)
 281                 {
 282                         int size = (rsa.KeySize >> 3); // div 8
 283                         byte[] EM = Encode_v15 (hash, hashValue, size);
 284                         byte[] m = OS2IP (EM);
 285                         byte[] s = RSASP1 (rsa, m);
 286                         byte[] S = I2OSP (s, size);
 287                         return S;
 288                 }
 289
 290                 // PKCS #1 v.2.1, Section 8.2.2
 291                 // RSASSA-PKCS1-V1_5-VERIFY ((n, e), M, S)
 292                 public static bool Verify_v15 (RSA rsa, HashAlgorithm hash, byte[] hashValue, byte[] signature)
 293                 {
 294                         int size = (rsa.KeySize >> 3); // div 8
 295                         byte[] s = OS2IP (signature);
 296                         byte[] m = RSAVP1 (rsa, s);
 297                         byte[] EM2 = I2OSP (m, size);
 298                         byte[] EM = Encode_v15 (hash, hashValue, size);
 299                         bool result = Compare (EM, EM2);
 300                         if (!result) {
 301                                 // NOTE: some signatures don't include the hash OID (pretty lame but real)
 302                                 // and compatible with MS implementation
 303                                 if ((EM2 [0] != 0x00) || (EM2 [1] != 0x01))
 304                                         return false;
 305                                 // TODO: add more validation
 306                                 byte[] decryptedHash = new byte [hashValue.Length];
 307                                 Buffer.BlockCopy (EM2, EM2.Length - hashValue.Length, decryptedHash, 0, decryptedHash.Length);
 308                                 result = Compare (decryptedHash, hashValue);
 309                         }
 310                         return result;
 311                 }
 312
 313                 // PKCS #1 v.2.1, Section 9.2
 314                 // EMSA-PKCS1-v1_5-Encode
 315                 public static byte[] Encode_v15 (HashAlgorithm hash, byte[] hashValue, int emLength)
 316                 {
 317                         if (hashValue.Length != (hash.HashSize >> 3))
 318                                 throw new CryptographicException ("bad hash length for " + hash.ToString ());
 319
 320                         // DigestInfo ::= SEQUENCE {
 321                         //      digestAlgorithm AlgorithmIdentifier,
 322                         //      digest OCTET STRING
 323                         // }
 324
 325                         byte[] t = null;
 326
 327                         string oid = CryptoConfig.MapNameToOID (hash.ToString ());
 328                         if (oid != null)
 329                         {
 330                                 ASN1 digestAlgorithm = new ASN1 (0x30);
 331                                 digestAlgorithm.Add (new ASN1 (CryptoConfig.EncodeOID (oid)));
 332                                 digestAlgorithm.Add (new ASN1 (0x05));          // NULL
 333                                 ASN1 digest = new ASN1 (0x04, hashValue);
 334                                 ASN1 digestInfo = new ASN1 (0x30);
 335                                 digestInfo.Add (digestAlgorithm);
 336                                 digestInfo.Add (digest);
 337
 338                                 t = digestInfo.GetBytes ();
 339                         }
 340                         else
 341                         {
 342                                 // There are no valid OID, in this case t = hashValue
 343                                 // This is the case of the MD5SHA hash algorithm
 344                                 t = hashValue;
 345                         }
 346
 347                         Buffer.BlockCopy (hashValue, 0, t, t.Length - hashValue.Length, hashValue.Length);
 348
 349                         int PSLength = System.Math.Max (8, emLength - t.Length - 3);
 350                         // PS = PSLength of 0xff
 351
 352                         // EM = 0x00 | 0x01 | PS | 0x00 | T
 353                         byte[] EM = new byte [PSLength + t.Length + 3];
 354                         EM [1] = 0x01;
 355                         for (int i=2; i < PSLength + 2; i++)
 356                                 EM[i] = 0xff;
 357                         Buffer.BlockCopy (t, 0, EM, PSLength + 3, t.Length);
 358
 359                         return EM;
 360                 }
 361
 362                 // PKCS #1 v.2.1, Section B.2.1
 363                 public static byte[] MGF1 (HashAlgorithm hash, byte[] mgfSeed, int maskLen)
 364                 {
 365                         // 1. If maskLen > 2^32 hLen, output "mask too long" and stop.
 366                         // easy - this is impossible by using a int (31bits) as parameter ;-)
 367                         // BUT with a signed int we do have to check for negative values!
 368                         if (maskLen < 0)
 369                                 throw new OverflowException();
 370
 371                         int mgfSeedLength = mgfSeed.Length;
 372                         int hLen = (hash.HashSize >> 3); // from bits to bytes
 373                         int iterations = (maskLen / hLen);
 374                         if (maskLen % hLen != 0)
 375                                 iterations++;
 376                         // 2. Let T be the empty octet string.
 377                         byte[] T = new byte [iterations * hLen];
 378
 379                         byte[] toBeHashed = new byte [mgfSeedLength + 4];
 380                         int pos = 0;
 381                         // 3. For counter from 0 to \ceil (maskLen / hLen) - 1, do the following:
 382                         for (int counter = 0; counter < iterations; counter++) {
 383                                 // a.   Convert counter to an octet string C of length 4 octets
 384                                 byte[] C = I2OSP (counter, 4);
 385
 386                                 // b.   Concatenate the hash of the seed mgfSeed and C to the octet string T:
 387                                 //      T = T || Hash (mgfSeed || C)
 388                                 Buffer.BlockCopy (mgfSeed, 0, toBeHashed, 0, mgfSeedLength);
 389                                 Buffer.BlockCopy (C, 0, toBeHashed, mgfSeedLength, 4);
 390                                 byte[] output = hash.ComputeHash (toBeHashed);
 391                                 Buffer.BlockCopy (output, 0, T, pos, hLen);
 392                                 pos += mgfSeedLength;
 393                         }
 394
 395                         // 4. Output the leading maskLen octets of T as the octet string mask.
 396                         byte[] mask = new byte [maskLen];
 397                         Buffer.BlockCopy (T, 0, mask, 0, maskLen);
 398                         return mask;
 399                 }
 400         }
 401 }