class/System.Security/Mono.Security.Cryptography/ManagedProtection.cs

   1 //
   2 // ManagedProtection.cs -
   3 //      Protect (encrypt) data without (user involved) key management
   4 //
   5 // Author:
   6 //      Sebastien Pouliot  <sebastien@ximian.com>
   7 //
   8 // Copyright (C) 2005 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.IO;
  32 using System.Runtime.InteropServices;
  33 using System.Security;
  34 using System.Security.Cryptography;
  35 using System.Security.Permissions;
  36
  37 namespace Mono.Security.Cryptography {
  38
  39         // Managed Protection Implementation
  40         //
  41         // Features
  42         // * Separate RSA 1536 bits keypairs for each user and the computer
  43         // * AES 128 bits encryption (separate key for each data protected)
  44         // * SHA256 digest to ensure integrity
  45
  46 #if !NET_2_0
  47         internal enum DataProtectionScope {
  48                 CurrentUser,
  49                 LocalMachine
  50         }
  51 #endif
  52
  53         internal static class ManagedProtection {
  54
  55 // FIXME        [KeyContainerPermission (SecurityAction.Assert, KeyContainerName = "DAPI",
  56 //                      Flags = KeyContainerPermissionFlags.Open | KeyContainerPermissionFlags.Create)]
  57                 public static byte[] Protect (byte[] userData, byte[] optionalEntropy, DataProtectionScope scope)
  58                 {
  59                         if (userData == null)
  60                                 throw new ArgumentNullException ("userData");
  61
  62                         Rijndael aes = Rijndael.Create ();
  63                         aes.KeySize = 128;
  64
  65                         byte[] encdata = null;
  66                         using (MemoryStream ms = new MemoryStream ()) {
  67                                 ICryptoTransform t = aes.CreateEncryptor ();
  68                                 using (CryptoStream cs = new CryptoStream (ms, t, CryptoStreamMode.Write)) {
  69                                         cs.Write (userData, 0, userData.Length);
  70                                         cs.Close ();
  71                                         encdata = ms.ToArray ();
  72                                 }
  73                         }
  74
  75                         byte[] key = null;
  76                         byte[] iv = null;
  77                         byte[] secret = null;
  78                         byte[] header = null;
  79                         SHA256 hash = SHA256.Create ();
  80
  81                         try {
  82                                 key = aes.Key;
  83                                 iv = aes.IV;
  84                                 secret = new byte[1 + 1 + 16 + 1 + 16 + 1 + 32];
  85
  86                                 byte[] digest = hash.ComputeHash (userData);
  87                                 if ((optionalEntropy != null) && (optionalEntropy.Length > 0)) {
  88                                         // the same optionalEntropy will be required to get the data back
  89                                         byte[] mask = hash.ComputeHash (optionalEntropy);
  90                                         for (int i = 0; i < 16; i++) {
  91                                                 key[i] ^= mask[i];
  92                                                 iv[i] ^= mask[i + 16];
  93                                         }
  94                                         secret[0] = 2; // entropy
  95                                 } else {
  96                                         secret[0] = 1; // without entropy
  97                                 }
  98
  99                                 secret[1] = 16; // key size
 100                                 Buffer.BlockCopy (key, 0, secret, 2, 16);
 101                                 secret[18] = 16; // iv size
 102                                 Buffer.BlockCopy (iv, 0, secret, 19, 16);
 103                                 secret[35] = 32; // digest size
 104                                 Buffer.BlockCopy (digest, 0, secret, 36, 32);
 105
 106                                 RSAOAEPKeyExchangeFormatter formatter = new RSAOAEPKeyExchangeFormatter (GetKey (scope));
 107                                 header = formatter.CreateKeyExchange (secret);
 108                         }
 109                         finally {
 110                                 if (key != null) {
 111                                         Array.Clear (key, 0, key.Length);
 112                                         key = null;
 113                                 }
 114                                 if (secret != null) {
 115                                         Array.Clear (secret, 0, secret.Length);
 116                                         secret = null;
 117                                 }
 118                                 if (iv != null) {
 119                                         Array.Clear (iv, 0, iv.Length);
 120                                         iv = null;
 121                                 }
 122                                 aes.Clear ();
 123                                 hash.Clear ();
 124                         }
 125
 126                         byte[] result = new byte[header.Length + encdata.Length];
 127                         Buffer.BlockCopy (header, 0, result, 0, header.Length);
 128                         Buffer.BlockCopy (encdata, 0, result, header.Length, encdata.Length);
 129                         return result;
 130                 }
 131
 132 // FIXME        [KeyContainerPermission (SecurityAction.Assert, KeyContainerName = "DAPI",
 133 //                      Flags = KeyContainerPermissionFlags.Open | KeyContainerPermissionFlags.Decrypt)]
 134                 public static byte[] Unprotect (byte[] encryptedData, byte[] optionalEntropy, DataProtectionScope scope)
 135                 {
 136                         if (encryptedData == null)
 137                                 throw new ArgumentNullException ("encryptedData");
 138
 139                         byte[] decdata = null;
 140
 141                         Rijndael aes = Rijndael.Create ();
 142                         RSA rsa = GetKey (scope);
 143                         int headerSize = (rsa.KeySize >> 3);
 144                         bool valid1 = (encryptedData.Length >= headerSize);
 145                         if (!valid1)
 146                                 headerSize = encryptedData.Length;
 147
 148                         byte[] header = new byte[headerSize];
 149                         Buffer.BlockCopy (encryptedData, 0, header, 0, headerSize);
 150
 151                         byte[] secret = null;
 152                         byte[] key = null;
 153                         byte[] iv = null;
 154                         bool valid2 = false;
 155                         bool valid3 = false;
 156                         bool valid4 = false;
 157                         SHA256 hash = SHA256.Create ();
 158
 159                         try {
 160                                 try {
 161                                         RSAOAEPKeyExchangeDeformatter deformatter = new RSAOAEPKeyExchangeDeformatter (rsa);
 162                                         secret = deformatter.DecryptKeyExchange (header);
 163                                         valid2 = (secret.Length == 68);
 164                                 }
 165                                 catch {
 166                                         valid2 = false;
 167                                 }
 168
 169                                 if (!valid2)
 170                                         secret = new byte[68];
 171
 172                                 // known values for structure (version 1 or 2)
 173                                 valid3 = ((secret[1] == 16) && (secret[18] == 16) && (secret[35] == 32));
 174
 175                                 key = new byte [16];
 176                                 Buffer.BlockCopy (secret, 2, key, 0, 16);
 177                                 iv = new byte [16];
 178                                 Buffer.BlockCopy (secret, 19, iv, 0, 16);
 179
 180                                 if ((optionalEntropy != null) && (optionalEntropy.Length > 0)) {
 181                                         // the decrypted data won't be valid if the entropy isn't
 182                                         // the same as the one used to protect (encrypt) it
 183                                         byte[] mask = hash.ComputeHash (optionalEntropy);
 184                                         for (int i = 0; i < 16; i++) {
 185                                                 key[i] ^= mask[i];
 186                                                 iv[i] ^= mask[i + 16];
 187                                         }
 188                                         valid3 &= (secret[0] == 2);     // with entropy
 189                                 } else {
 190                                         valid3 &= (secret[0] == 1);     // without entropy
 191                                 }
 192
 193                                 using (MemoryStream ms = new MemoryStream ()) {
 194                                         ICryptoTransform t = aes.CreateDecryptor (key, iv);
 195                                         using (CryptoStream cs = new CryptoStream (ms, t, CryptoStreamMode.Write)) {
 196                                                 try {
 197                                                         cs.Write (encryptedData, headerSize, encryptedData.Length - headerSize);
 198                                                         cs.Close ();
 199                                                 }
 200                                                 catch {
 201                                                         // whatever, we keep going
 202                                                 }
 203                                         }
 204                                         decdata = ms.ToArray ();
 205                                 }
 206
 207                                 byte[] digest = hash.ComputeHash (decdata);
 208                                 valid4 = true;
 209                                 for (int i=0; i < 32; i++) {
 210                                         if (digest [i] != secret [36 + i])
 211                                                 valid4 = false;
 212                                 }
 213                         }
 214                         finally {
 215                                 if (key != null) {
 216                                         Array.Clear (key, 0, key.Length);
 217                                         key = null;
 218                                 }
 219                                 if (secret != null) {
 220                                         Array.Clear (secret, 0, secret.Length);
 221                                         secret = null;
 222                                 }
 223                                 if (iv != null) {
 224                                         Array.Clear (iv, 0, iv.Length);
 225                                         iv = null;
 226                                 }
 227                                 aes.Clear ();
 228                                 hash.Clear ();
 229                         }
 230
 231                         // single point of error (also limits timing informations)
 232                         if (!valid1 || !valid2 || !valid3 || !valid4) {
 233                                 if (decdata != null) {
 234                                         Array.Clear (decdata, 0, decdata.Length);
 235                                         decdata = null;
 236                                 }
 237                                 throw new CryptographicException (Locale.GetText ("Invalid data."));
 238                         }
 239                         return decdata;
 240                 }
 241
 242                 // private stuff
 243
 244                 private static RSA user;
 245                 private static RSA machine;
 246
 247                 private static RSA GetKey (DataProtectionScope scope)
 248                 {
 249                         switch (scope) {
 250                         case DataProtectionScope.CurrentUser:
 251                                 if (user == null) {
 252                                         CspParameters csp = new CspParameters ();
 253                                         csp.KeyContainerName = "DAPI";
 254                                         user = new RSACryptoServiceProvider (1536, csp);
 255                                 }
 256                                 return user;
 257                         case DataProtectionScope.LocalMachine:
 258                                 if (machine == null) {
 259                                         CspParameters csp = new CspParameters ();
 260                                         csp.KeyContainerName = "DAPI";
 261                                         csp.Flags = CspProviderFlags.UseMachineKeyStore;
 262                                         machine = new RSACryptoServiceProvider (1536, csp);
 263                                 }
 264                                 return machine;
 265                         default:
 266                                 throw new CryptographicException (Locale.GetText ("Invalid scope."));
 267                         }
 268                 }
 269         }
 270 }