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233
iTechSharp/srcbc/openpgp/PgpPublicKeyEncryptedData.cs
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233
iTechSharp/srcbc/openpgp/PgpPublicKeyEncryptedData.cs
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using System;
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using System.IO;
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using Org.BouncyCastle.Crypto;
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using Org.BouncyCastle.Crypto.IO;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Math;
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using Org.BouncyCastle.Security;
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using Org.BouncyCastle.Utilities.IO;
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namespace Org.BouncyCastle.Bcpg.OpenPgp
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{
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/// <remarks>A public key encrypted data object.</remarks>
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public class PgpPublicKeyEncryptedData
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: PgpEncryptedData
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{
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private PublicKeyEncSessionPacket keyData;
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internal PgpPublicKeyEncryptedData(
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PublicKeyEncSessionPacket keyData,
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InputStreamPacket encData)
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: base(encData)
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{
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this.keyData = keyData;
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}
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private static IBufferedCipher GetKeyCipher(
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PublicKeyAlgorithmTag algorithm)
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{
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try
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{
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switch (algorithm)
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{
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case PublicKeyAlgorithmTag.RsaEncrypt:
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case PublicKeyAlgorithmTag.RsaGeneral:
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return CipherUtilities.GetCipher("RSA//PKCS1Padding");
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case PublicKeyAlgorithmTag.ElGamalEncrypt:
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case PublicKeyAlgorithmTag.ElGamalGeneral:
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return CipherUtilities.GetCipher("ElGamal/ECB/PKCS1Padding");
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default:
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throw new PgpException("unknown asymmetric algorithm: " + algorithm);
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}
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}
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catch (PgpException e)
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{
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throw e;
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}
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catch (Exception e)
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{
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throw new PgpException("Exception creating cipher", e);
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}
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}
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private bool ConfirmCheckSum(
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byte[] sessionInfo)
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{
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int check = 0;
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for (int i = 1; i != sessionInfo.Length - 2; i++)
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{
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check += sessionInfo[i] & 0xff;
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}
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return (sessionInfo[sessionInfo.Length - 2] == (byte)(check >> 8))
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&& (sessionInfo[sessionInfo.Length - 1] == (byte)(check));
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}
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/// <summary>The key ID for the key used to encrypt the data.</summary>
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public long KeyId
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{
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get { return keyData.KeyId; }
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}
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/// <summary>Return the decrypted data stream for the packet.</summary>
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public Stream GetDataStream(
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PgpPrivateKey privKey)
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{
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IBufferedCipher c1 = GetKeyCipher(keyData.Algorithm);
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try
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{
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c1.Init(false, privKey.Key);
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}
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catch (InvalidKeyException e)
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{
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throw new PgpException("error setting asymmetric cipher", e);
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}
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BigInteger[] keyD = keyData.GetEncSessionKey();
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if (keyData.Algorithm == PublicKeyAlgorithmTag.RsaEncrypt
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|| keyData.Algorithm == PublicKeyAlgorithmTag.RsaGeneral)
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{
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c1.ProcessBytes(keyD[0].ToByteArrayUnsigned());
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}
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else
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{
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ElGamalPrivateKeyParameters k = (ElGamalPrivateKeyParameters)privKey.Key;
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int size = (k.Parameters.P.BitLength + 7) / 8;
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byte[] bi = keyD[0].ToByteArray();
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int diff = bi.Length - size;
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if (diff >= 0)
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{
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c1.ProcessBytes(bi, diff, size);
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}
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else
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{
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byte[] zeros = new byte[-diff];
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c1.ProcessBytes(zeros);
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c1.ProcessBytes(bi);
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}
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bi = keyD[1].ToByteArray();
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diff = bi.Length - size;
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if (diff >= 0)
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{
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c1.ProcessBytes(bi, diff, size);
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}
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else
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{
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byte[] zeros = new byte[-diff];
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c1.ProcessBytes(zeros);
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c1.ProcessBytes(bi);
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}
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}
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byte[] plain;
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try
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{
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plain = c1.DoFinal();
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}
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catch (Exception e)
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{
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throw new PgpException("exception decrypting secret key", e);
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}
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if (!ConfirmCheckSum(plain))
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throw new PgpKeyValidationException("key checksum failed");
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IBufferedCipher c2;
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string cipherName = PgpUtilities.GetSymmetricCipherName((SymmetricKeyAlgorithmTag) plain[0]);
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string cName = cipherName;
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try
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{
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if (encData is SymmetricEncIntegrityPacket)
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{
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cName += "/CFB/NoPadding";
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}
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else
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{
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cName += "/OpenPGPCFB/NoPadding";
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}
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c2 = CipherUtilities.GetCipher(cName);
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}
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catch (PgpException e)
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{
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throw e;
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}
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catch (Exception e)
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{
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throw new PgpException("exception creating cipher", e);
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}
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if (c2 == null)
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return encData.GetInputStream();
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try
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{
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KeyParameter key = ParameterUtilities.CreateKeyParameter(
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cipherName, plain, 1, plain.Length - 3);
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byte[] iv = new byte[c2.GetBlockSize()];
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c2.Init(false, new ParametersWithIV(key, iv));
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encStream = BcpgInputStream.Wrap(new CipherStream(encData.GetInputStream(), c2, null));
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if (encData is SymmetricEncIntegrityPacket)
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{
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truncStream = new TruncatedStream(encStream);
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string digestName = PgpUtilities.GetDigestName(HashAlgorithmTag.Sha1);
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IDigest digest = DigestUtilities.GetDigest(digestName);
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encStream = new DigestStream(truncStream, digest, null);
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}
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if (Streams.ReadFully(encStream, iv, 0, iv.Length) < iv.Length)
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throw new EndOfStreamException("unexpected end of stream.");
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int v1 = encStream.ReadByte();
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int v2 = encStream.ReadByte();
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if (v1 < 0 || v2 < 0)
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throw new EndOfStreamException("unexpected end of stream.");
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// Note: the oracle attack on the "quick check" bytes is deemed
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// a security risk for typical public key encryption usages,
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// therefore we do not perform the check.
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// bool repeatCheckPassed =
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// iv[iv.Length - 2] == (byte)v1
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// && iv[iv.Length - 1] == (byte)v2;
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//
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// // Note: some versions of PGP appear to produce 0 for the extra
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// // bytes rather than repeating the two previous bytes
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// bool zeroesCheckPassed =
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// v1 == 0
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// && v2 == 0;
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//
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// if (!repeatCheckPassed && !zeroesCheckPassed)
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// {
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// throw new PgpDataValidationException("quick check failed.");
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// }
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return encStream;
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}
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catch (PgpException e)
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{
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throw e;
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}
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catch (Exception e)
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{
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throw new PgpException("Exception starting decryption", e);
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}
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}
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}
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}
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