protected SecureBuffer Expand (DisposeContext d, HMac hmac, string label, SecureBuffer seed, int length)
{
var blockSize = hmac.MacSize;
var iterations = (int)(length / blockSize);
if ((length % blockSize) > 0)
iterations++;
var resMacs = d.CreateBuffer (length);
var resOff = 0;
var tempBuf = d.CreateBuffer (blockSize);
var labelBytes = Encoding.ASCII.GetBytes (label);
for (int i = 1; i <= iterations; i++) {
hmac.Reset ();
if (i == 1) {
hmac.TransformBlock (labelBytes, 0, labelBytes.Length);
hmac.TransformBlock (seed.Buffer, 0, seed.Size);
} else {
hmac.TransformBlock (tempBuf.Buffer, 0, blockSize);
}
hmac.TransformFinalBlock (tempBuf.Buffer, 0, blockSize);
hmac.Reset ();
hmac.TransformBlock (tempBuf.Buffer, 0, blockSize);
hmac.TransformBlock (labelBytes, 0, labelBytes.Length);
hmac.TransformBlock (seed.Buffer, 0, seed.Size);
hmac.TransformFinalBlock (resMacs.Buffer, resOff, Min (length - resOff, blockSize));
resOff += blockSize;
}
return new SecureBuffer (resMacs.StealBuffer ());
}
void ComputeMasterSecret (DisposeContext d, TlsContext ctx, SecureBuffer preMasterSecret)
{
// Compute ClientRandom + ServerRandom
int clen = ctx.HandshakeParameters.ClientRandom.Size;
int slen = ctx.HandshakeParameters.ServerRandom.Size;
int rlen = clen + slen;
var cs = d.CreateBuffer (rlen);
Buffer.BlockCopy (ctx.HandshakeParameters.ClientRandom.Buffer, 0, cs.Buffer, 0, clen);
Buffer.BlockCopy (ctx.HandshakeParameters.ServerRandom.Buffer, 0, cs.Buffer, clen, slen);
// Server Random + Client Random
var sc = d.CreateBuffer (rlen);
Buffer.BlockCopy (ctx.HandshakeParameters.ServerRandom.Buffer, 0, sc.Buffer, 0, slen);
Buffer.BlockCopy (ctx.HandshakeParameters.ClientRandom.Buffer, 0, sc.Buffer, slen, clen);
// Create master secret
var crypto = ctx.Session.PendingCrypto;
crypto.MasterSecret = crypto.Cipher.PRF.ComputeMasterSecret (preMasterSecret, cs);
#if DEBUG_FULL
if (ctx.EnableDebugging) {
DebugHelper.WriteLine ("CS", cs);
DebugHelper.WriteLine ("SC", sc);
DebugHelper.WriteLine ("PRE-MASTER", preMasterSecret);
DebugHelper.WriteLine ("MASTER SECRET", crypto.MasterSecret.Buffer);
}
#endif
var keyBlock = crypto.Cipher.PRF.ComputeKeyExpansion (d, crypto.MasterSecret, sc, crypto.Cipher.KeyBlockSize);
#if DEBUG_FULL
if (ctx.EnableDebugging) {
DebugHelper.WriteLine ("KEY BLOCK SIZE: {0}", crypto.Cipher.KeyBlockSize);
DebugHelper.WriteLine ("KEY BLOCK", keyBlock.Buffer);
}
#endif
crypto.ClientWriteMac = keyBlock.ReadSecureBuffer (crypto.Cipher.HashSize);
crypto.ServerWriteMac = keyBlock.ReadSecureBuffer (crypto.Cipher.HashSize);
crypto.ClientWriteKey = keyBlock.ReadSecureBuffer (crypto.Cipher.KeyMaterialSize);
crypto.ServerWriteKey = keyBlock.ReadSecureBuffer (crypto.Cipher.KeyMaterialSize);
if (crypto.Cipher.HasFixedIV) {
crypto.ClientWriteIV = keyBlock.ReadSecureBuffer (crypto.Cipher.FixedIvSize);
crypto.ServerWriteIV = keyBlock.ReadSecureBuffer (crypto.Cipher.FixedIvSize);
#if DEBUG_FULL
if (ctx.EnableDebugging) {
DebugHelper.WriteLine ("CLIENT IV", crypto.ClientWriteIV.Buffer);
DebugHelper.WriteLine ("SERVER IV", crypto.ServerWriteIV.Buffer);
}
#endif
}
}
protected override SecureBuffer PRF(DisposeContext d, SecureBuffer secret, string label, SecureBuffer data, int length)
{
/* Secret Length calc exmplain from the RFC2246. Section 5
*
* S1 and S2 are the two halves of the secret and each is the same
* length. S1 is taken from the first half of the secret, S2 from the
* second half. Their length is created by rounding up the length of the
* overall secret divided by two; thus, if the original secret is an odd
* number of bytes long, the last byte of S1 will be the same as the
* first byte of S2.
*/
// split secret in 2
int secretLen = secret.Size >> 1;
// rounding up
if ((secret.Size & 0x1) == 0x1)
{
secretLen++;
}
// Secret 1
var secret1 = d.CreateBuffer(secretLen);
Buffer.BlockCopy(secret.Buffer, 0, secret1.Buffer, 0, secretLen);
// Secret2
var secret2 = d.CreateBuffer(secretLen);
Buffer.BlockCopy(secret.Buffer, (secret.Size - secretLen), secret2.Buffer, 0, secretLen);
// Secret 1 processing
var p_md5 = d.Add(Expand(d, HMac.Create(HashAlgorithmType.Md5, secret1), label, data, length));
// Secret 2 processing
var p_sha = d.Add(Expand(d, HMac.Create(HashAlgorithmType.Sha1, secret2), label, data, length));
// Perfor XOR of both results
var masterSecret = new SecureBuffer(length);
for (int i = 0; i < length; i++)
{
masterSecret.Buffer[i] = (byte)(p_md5.Buffer[i] ^ p_sha.Buffer[i]);
}
return(masterSecret);
}
protected override int Decrypt(DisposeContext d, ContentType contentType, IBufferOffsetSize input, IBufferOffsetSize output)
{
var implicitNonce = IsClient ? ServerWriteIV : ClientWriteIV;
var writeKey = IsClient ? ServerWriteKey : ClientWriteKey;
#if DEBUG_FULL
if (Cipher.EnableDebugging)
{
DebugHelper.WriteLine("FIXED IV", implicitNonce);
DebugHelper.WriteLine("WRITE KEY", writeKey);
DebugHelper.WriteLine("SEQUENCE: {0}", ReadSequenceNumber);
}
#endif
var length = input.Size - ExplicitNonceSize;
var aad = new TlsBuffer(13);
aad.Write(ReadSequenceNumber);
aad.Write((byte)contentType);
aad.Write((short)Protocol);
aad.Write((short)(length - MacSize));
#if DEBUG_FULL
if (Cipher.EnableDebugging)
{
DebugHelper.WriteFull("TAG", aad);
}
#endif
var gcm = new GcmBlockCipher(new AesEngine());
var key = new KeyParameter(writeKey.Buffer);
var nonce = d.CreateBuffer(ImplicitNonceSize + ExplicitNonceSize);
Buffer.BlockCopy(implicitNonce.Buffer, 0, nonce.Buffer, 0, ImplicitNonceSize);
Buffer.BlockCopy(input.Buffer, input.Offset, nonce.Buffer, ImplicitNonceSize, ExplicitNonceSize);
#if DEBUG_FULL
if (Cipher.EnableDebugging)
{
DebugHelper.WriteLine("NONCE", nonce);
}
#endif
var parameters = new AeadParameters(key, 128, nonce.Buffer, aad.Buffer);
gcm.Init(false, parameters);
int ret;
try {
ret = gcm.ProcessBytes(input.Buffer, input.Offset + ExplicitNonceSize, length, output.Buffer, output.Offset);
ret += gcm.DoFinal(output.Buffer, output.Offset + ret);
} catch (CryptoException ex) {
throw new TlsException(AlertDescription.BadRecordMAC, ex.Message);
}
return(ret);
}
protected override SecureBuffer PRF (DisposeContext d, SecureBuffer secret, string label, SecureBuffer data, int length)
{
/* Secret Length calc exmplain from the RFC2246. Section 5
*
* S1 and S2 are the two halves of the secret and each is the same
* length. S1 is taken from the first half of the secret, S2 from the
* second half. Their length is created by rounding up the length of the
* overall secret divided by two; thus, if the original secret is an odd
* number of bytes long, the last byte of S1 will be the same as the
* first byte of S2.
*/
// split secret in 2
int secretLen = secret.Size >> 1;
// rounding up
if ((secret.Size & 0x1) == 0x1)
secretLen++;
// Secret 1
var secret1 = d.CreateBuffer (secretLen);
Buffer.BlockCopy (secret.Buffer, 0, secret1.Buffer, 0, secretLen);
// Secret2
var secret2 = d.CreateBuffer (secretLen);
Buffer.BlockCopy (secret.Buffer, (secret.Size - secretLen), secret2.Buffer, 0, secretLen);
// Secret 1 processing
var p_md5 = d.Add (Expand (d, HMac.Create (HashAlgorithmType.Md5, secret1), label, data, length));
// Secret 2 processing
var p_sha = d.Add (Expand (d, HMac.Create (HashAlgorithmType.Sha1, secret2), label, data, length));
// Perfor XOR of both results
var masterSecret = new SecureBuffer (length);
for (int i = 0; i < length; i++)
masterSecret.Buffer[i] = (byte)(p_md5.Buffer[i] ^ p_sha.Buffer[i]);
return masterSecret;
}
void ComputeMasterSecret(DisposeContext d, TlsContext ctx, SecureBuffer preMasterSecret)
{
// Compute ClientRandom + ServerRandom
int clen = ctx.HandshakeParameters.ClientRandom.Size;
int slen = ctx.HandshakeParameters.ServerRandom.Size;
int rlen = clen + slen;
var cs = d.CreateBuffer(rlen);
Buffer.BlockCopy(ctx.HandshakeParameters.ClientRandom.Buffer, 0, cs.Buffer, 0, clen);
Buffer.BlockCopy(ctx.HandshakeParameters.ServerRandom.Buffer, 0, cs.Buffer, clen, slen);
// Server Random + Client Random
var sc = d.CreateBuffer(rlen);
Buffer.BlockCopy(ctx.HandshakeParameters.ServerRandom.Buffer, 0, sc.Buffer, 0, slen);
Buffer.BlockCopy(ctx.HandshakeParameters.ClientRandom.Buffer, 0, sc.Buffer, slen, clen);
// Create master secret
var crypto = ctx.Session.PendingCrypto;
crypto.MasterSecret = crypto.Cipher.PRF.ComputeMasterSecret(preMasterSecret, cs);
#if DEBUG_FULL
if (ctx.EnableDebugging)
{
DebugHelper.WriteLine("CS", cs);
DebugHelper.WriteLine("SC", sc);
DebugHelper.WriteLine("PRE-MASTER", preMasterSecret);
DebugHelper.WriteLine("MASTER SECRET", crypto.MasterSecret.Buffer);
}
#endif
var keyBlock = crypto.Cipher.PRF.ComputeKeyExpansion(d, crypto.MasterSecret, sc, crypto.Cipher.KeyBlockSize);
#if DEBUG_FULL
if (ctx.EnableDebugging)
{
DebugHelper.WriteLine("KEY BLOCK SIZE: {0}", crypto.Cipher.KeyBlockSize);
DebugHelper.WriteLine("KEY BLOCK", keyBlock.Buffer);
}
#endif
crypto.ClientWriteMac = keyBlock.ReadSecureBuffer(crypto.Cipher.HashSize);
crypto.ServerWriteMac = keyBlock.ReadSecureBuffer(crypto.Cipher.HashSize);
crypto.ClientWriteKey = keyBlock.ReadSecureBuffer(crypto.Cipher.KeyMaterialSize);
crypto.ServerWriteKey = keyBlock.ReadSecureBuffer(crypto.Cipher.KeyMaterialSize);
if (crypto.Cipher.HasFixedIV)
{
crypto.ClientWriteIV = keyBlock.ReadSecureBuffer(crypto.Cipher.FixedIvSize);
crypto.ServerWriteIV = keyBlock.ReadSecureBuffer(crypto.Cipher.FixedIvSize);
#if DEBUG_FULL
if (ctx.EnableDebugging)
{
DebugHelper.WriteLine("CLIENT IV", crypto.ClientWriteIV.Buffer);
DebugHelper.WriteLine("SERVER IV", crypto.ServerWriteIV.Buffer);
}
#endif
}
}
protected override int Decrypt (DisposeContext d, ContentType contentType, IBufferOffsetSize input, IBufferOffsetSize output)
{
var implicitNonce = IsClient ? ServerWriteIV : ClientWriteIV;
var writeKey = IsClient ? ServerWriteKey : ClientWriteKey;
#if DEBUG_FULL
if (Cipher.EnableDebugging) {
DebugHelper.WriteLine ("FIXED IV", implicitNonce);
DebugHelper.WriteLine ("WRITE KEY", writeKey);
DebugHelper.WriteLine ("SEQUENCE: {0}", ReadSequenceNumber);
}
#endif
var length = input.Size - ExplicitNonceSize;
var aad = new TlsBuffer (13);
aad.Write (ReadSequenceNumber);
aad.Write ((byte)contentType);
aad.Write ((short)Protocol);
aad.Write ((short)(length - MacSize));
#if DEBUG_FULL
if (Cipher.EnableDebugging)
DebugHelper.WriteFull ("TAG", aad);
#endif
var gcm = new GcmBlockCipher (new AesEngine ());
var key = new KeyParameter (writeKey.Buffer);
var nonce = d.CreateBuffer (ImplicitNonceSize + ExplicitNonceSize);
Buffer.BlockCopy (implicitNonce.Buffer, 0, nonce.Buffer, 0, ImplicitNonceSize);
Buffer.BlockCopy (input.Buffer, input.Offset, nonce.Buffer, ImplicitNonceSize, ExplicitNonceSize);
#if DEBUG_FULL
if (Cipher.EnableDebugging)
DebugHelper.WriteLine ("NONCE", nonce);
#endif
var parameters = new AeadParameters (key, 128, nonce.Buffer, aad.Buffer);
gcm.Init (false, parameters);
int ret;
try {
ret = gcm.ProcessBytes (input.Buffer, input.Offset + ExplicitNonceSize, length, output.Buffer, output.Offset);
ret += gcm.DoFinal (output.Buffer, output.Offset + ret);
} catch (CryptoException ex) {
throw new TlsException (AlertDescription.BadRecordMAC, ex.Message);
}
return ret;
}
protected SecureBuffer Expand (DisposeContext d, HMac hmac, string label, SecureBuffer seed, int length)
{
var blockSize = hmac.MacSize;
var iterations = (int)(length / blockSize);
if ((length % blockSize) > 0)
iterations++;
var resMacs = d.CreateBuffer (length);
var resOff = 0;
var tempBuf = d.CreateBuffer (blockSize);
var labelBytes = Encoding.ASCII.GetBytes (label);
for (int i = 1; i <= iterations; i++) {
hmac.Reset ();
if (i == 1) {
hmac.TransformBlock (labelBytes, 0, labelBytes.Length);
hmac.TransformBlock (seed.Buffer, 0, seed.Size);
} else {
hmac.TransformBlock (tempBuf.Buffer, 0, blockSize);
}
hmac.TransformFinalBlock (tempBuf.Buffer, 0, blockSize);
hmac.Reset ();
hmac.TransformBlock (tempBuf.Buffer, 0, blockSize);
hmac.TransformBlock (labelBytes, 0, labelBytes.Length);
hmac.TransformBlock (seed.Buffer, 0, seed.Size);
hmac.TransformFinalBlock (resMacs.Buffer, resOff, Min (length - resOff, blockSize));
resOff += blockSize;
}
return new SecureBuffer (resMacs.StealBuffer ());
}
