diff options
Diffstat (limited to 'crypto/src/openpgp/PgpPublicKeyEncryptedData.cs')
| -rw-r--r-- | crypto/src/openpgp/PgpPublicKeyEncryptedData.cs | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/crypto/src/openpgp/PgpPublicKeyEncryptedData.cs b/crypto/src/openpgp/PgpPublicKeyEncryptedData.cs new file mode 100644 index 000000000..b6504cbcd --- /dev/null +++ b/crypto/src/openpgp/PgpPublicKeyEncryptedData.cs @@ -0,0 +1,252 @@ +using System; +using System.IO; + +using Org.BouncyCastle.Crypto; +using Org.BouncyCastle.Crypto.IO; +using Org.BouncyCastle.Crypto.Parameters; +using Org.BouncyCastle.Math; +using Org.BouncyCastle.Security; +using Org.BouncyCastle.Utilities.IO; + +namespace Org.BouncyCastle.Bcpg.OpenPgp +{ + /// <remarks>A public key encrypted data object.</remarks> + public class PgpPublicKeyEncryptedData + : PgpEncryptedData + { + private PublicKeyEncSessionPacket keyData; + + internal PgpPublicKeyEncryptedData( + PublicKeyEncSessionPacket keyData, + InputStreamPacket encData) + : base(encData) + { + this.keyData = keyData; + } + + private static IBufferedCipher GetKeyCipher( + PublicKeyAlgorithmTag algorithm) + { + try + { + switch (algorithm) + { + case PublicKeyAlgorithmTag.RsaEncrypt: + case PublicKeyAlgorithmTag.RsaGeneral: + return CipherUtilities.GetCipher("RSA//PKCS1Padding"); + case PublicKeyAlgorithmTag.ElGamalEncrypt: + case PublicKeyAlgorithmTag.ElGamalGeneral: + return CipherUtilities.GetCipher("ElGamal/ECB/PKCS1Padding"); + default: + throw new PgpException("unknown asymmetric algorithm: " + algorithm); + } + } + catch (PgpException e) + { + throw e; + } + catch (Exception e) + { + throw new PgpException("Exception creating cipher", e); + } + } + + private bool ConfirmCheckSum( + byte[] sessionInfo) + { + int check = 0; + + for (int i = 1; i != sessionInfo.Length - 2; i++) + { + check += sessionInfo[i] & 0xff; + } + + return (sessionInfo[sessionInfo.Length - 2] == (byte)(check >> 8)) + && (sessionInfo[sessionInfo.Length - 1] == (byte)(check)); + } + + /// <summary>The key ID for the key used to encrypt the data.</summary> + public long KeyId + { + get { return keyData.KeyId; } + } + + /// <summary> + /// Return the algorithm code for the symmetric algorithm used to encrypt the data. + /// </summary> + public SymmetricKeyAlgorithmTag GetSymmetricAlgorithm( + PgpPrivateKey privKey) + { + byte[] plain = fetchSymmetricKeyData(privKey); + + return (SymmetricKeyAlgorithmTag) plain[0]; + } + + /// <summary>Return the decrypted data stream for the packet.</summary> + public Stream GetDataStream( + PgpPrivateKey privKey) + { + byte[] plain = fetchSymmetricKeyData(privKey); + + IBufferedCipher c2; + string cipherName = PgpUtilities.GetSymmetricCipherName((SymmetricKeyAlgorithmTag) plain[0]); + string cName = cipherName; + + try + { + if (encData is SymmetricEncIntegrityPacket) + { + cName += "/CFB/NoPadding"; + } + else + { + cName += "/OpenPGPCFB/NoPadding"; + } + + c2 = CipherUtilities.GetCipher(cName); + } + catch (PgpException e) + { + throw e; + } + catch (Exception e) + { + throw new PgpException("exception creating cipher", e); + } + + if (c2 == null) + return encData.GetInputStream(); + + try + { + KeyParameter key = ParameterUtilities.CreateKeyParameter( + cipherName, plain, 1, plain.Length - 3); + + byte[] iv = new byte[c2.GetBlockSize()]; + + c2.Init(false, new ParametersWithIV(key, iv)); + + encStream = BcpgInputStream.Wrap(new CipherStream(encData.GetInputStream(), c2, null)); + + if (encData is SymmetricEncIntegrityPacket) + { + truncStream = new TruncatedStream(encStream); + + string digestName = PgpUtilities.GetDigestName(HashAlgorithmTag.Sha1); + IDigest digest = DigestUtilities.GetDigest(digestName); + + encStream = new DigestStream(truncStream, digest, null); + } + + if (Streams.ReadFully(encStream, iv, 0, iv.Length) < iv.Length) + throw new EndOfStreamException("unexpected end of stream."); + + int v1 = encStream.ReadByte(); + int v2 = encStream.ReadByte(); + + if (v1 < 0 || v2 < 0) + throw new EndOfStreamException("unexpected end of stream."); + + // Note: the oracle attack on the "quick check" bytes is deemed + // a security risk for typical public key encryption usages, + // therefore we do not perform the check. + +// bool repeatCheckPassed = +// iv[iv.Length - 2] == (byte)v1 +// && iv[iv.Length - 1] == (byte)v2; +// +// // Note: some versions of PGP appear to produce 0 for the extra +// // bytes rather than repeating the two previous bytes +// bool zeroesCheckPassed = +// v1 == 0 +// && v2 == 0; +// +// if (!repeatCheckPassed && !zeroesCheckPassed) +// { +// throw new PgpDataValidationException("quick check failed."); +// } + + return encStream; + } + catch (PgpException e) + { + throw e; + } + catch (Exception e) + { + throw new PgpException("Exception starting decryption", e); + } + } + + private byte[] fetchSymmetricKeyData( + PgpPrivateKey privKey) + { + IBufferedCipher c1 = GetKeyCipher(keyData.Algorithm); + + try + { + c1.Init(false, privKey.Key); + } + catch (InvalidKeyException e) + { + throw new PgpException("error setting asymmetric cipher", e); + } + + BigInteger[] keyD = keyData.GetEncSessionKey(); + + if (keyData.Algorithm == PublicKeyAlgorithmTag.RsaEncrypt + || keyData.Algorithm == PublicKeyAlgorithmTag.RsaGeneral) + { + c1.ProcessBytes(keyD[0].ToByteArrayUnsigned()); + } + else + { + ElGamalPrivateKeyParameters k = (ElGamalPrivateKeyParameters)privKey.Key; + int size = (k.Parameters.P.BitLength + 7) / 8; + + byte[] bi = keyD[0].ToByteArray(); + + int diff = bi.Length - size; + if (diff >= 0) + { + c1.ProcessBytes(bi, diff, size); + } + else + { + byte[] zeros = new byte[-diff]; + c1.ProcessBytes(zeros); + c1.ProcessBytes(bi); + } + + bi = keyD[1].ToByteArray(); + + diff = bi.Length - size; + if (diff >= 0) + { + c1.ProcessBytes(bi, diff, size); + } + else + { + byte[] zeros = new byte[-diff]; + c1.ProcessBytes(zeros); + c1.ProcessBytes(bi); + } + } + + byte[] plain; + try + { + plain = c1.DoFinal(); + } + catch (Exception e) + { + throw new PgpException("exception decrypting secret key", e); + } + + if (!ConfirmCheckSum(plain)) + throw new PgpKeyValidationException("key checksum failed"); + + return plain; + } + } +} |