/// <summary>
/// Verifies the signature of a signed message
/// </summary>
/// <remarks>
/// The expected structure of the signed message buffer is as follows:
/// - 4 bytes, unsigned integer in big endian format indicating the length of the plaintext message
/// - 2 bytes, unsigned integer in big endian format indicating the length of the signture
/// - The plaintext message
/// - The message's signature.
/// </remarks>
/// <param name="signedMessage">The packed signed message.</param>
/// <param name="origMessage">The extracted original message.</param>
/// <returns>True if the message has a valid signature, false otherwise.</returns>
public bool VerifySignature( byte[] signedMessage, out byte[] origMessage )
{
SecurityStatus status = SecurityStatus.InternalError;
SecPkgContext_Sizes sizes;
SecureBuffer dataBuffer;
SecureBuffer signatureBuffer;
SecureBufferAdapter adapter;
CheckLifecycle();
sizes = QueryBufferSizes();
if ( signedMessage.Length < 2 + 4 + sizes.MaxSignature )
{
throw new ArgumentException( "Input message is too small to possibly fit a valid message" );
}
int position = 0;
int messageLen;
int sigLen;
messageLen = ByteWriter.ReadInt32_BE( signedMessage, 0 );
position += 4;
sigLen = ByteWriter.ReadInt16_BE( signedMessage, position );
position += 2;
if ( messageLen + sigLen + 2 + 4 > signedMessage.Length )
{
throw new ArgumentException( "The buffer contains invalid data - the embedded length data does not add up." );
}
dataBuffer = new SecureBuffer( new byte[messageLen], BufferType.Data );
Array.Copy( signedMessage, position, dataBuffer.Buffer, 0, messageLen );
position += messageLen;
signatureBuffer = new SecureBuffer( new byte[sigLen], BufferType.Token );
Array.Copy( signedMessage, position, signatureBuffer.Buffer, 0, sigLen );
position += sigLen;
using ( adapter = new SecureBufferAdapter( new[] { dataBuffer, signatureBuffer } ) )
{
status = ContextNativeMethods.SafeVerifySignature(
this.ContextHandle,
0,
adapter,
0
);
}
if ( status == SecurityStatus.OK )
{
origMessage = dataBuffer.Buffer;
return true;
}
else if ( status == SecurityStatus.MessageAltered ||
status == SecurityStatus.OutOfSequence )
{
origMessage = null;
return false;
}
else
{
throw new SspiException( "Failed to determine the veracity of a signed message.", status );
}
}
/// <summary>
/// Signs the message using the context's session key.
/// </summary>
/// <remarks>
/// The structure of the returned buffer is as follows:
/// - 4 bytes, unsigned big-endian integer indicating the length of the plaintext message
/// - 2 bytes, unsigned big-endian integer indicating the length of the signture
/// - The plaintext message
/// - The message's signature.
/// </remarks>
/// <param name="message"></param>
/// <returns></returns>
public byte[] MakeSignature( byte[] message )
{
SecurityStatus status = SecurityStatus.InternalError;
SecPkgContext_Sizes sizes;
SecureBuffer dataBuffer;
SecureBuffer signatureBuffer;
SecureBufferAdapter adapter;
CheckLifecycle();
sizes = QueryBufferSizes();
dataBuffer = new SecureBuffer( new byte[message.Length], BufferType.Data );
signatureBuffer = new SecureBuffer( new byte[sizes.MaxSignature], BufferType.Token );
Array.Copy( message, dataBuffer.Buffer, message.Length );
using ( adapter = new SecureBufferAdapter( new[] { dataBuffer, signatureBuffer } ) )
{
status = ContextNativeMethods.SafeMakeSignature(
this.ContextHandle,
0,
adapter,
0
);
}
if ( status != SecurityStatus.OK )
{
throw new SspiException( "Failed to create message signature.", status );
}
byte[] outMessage;
int position = 0;
// Enough room for
// - original message length (4 bytes)
// - signature length (2 bytes)
// - original message
// - signature
outMessage = new byte[4 + 2 + dataBuffer.Length + signatureBuffer.Length];
ByteWriter.WriteInt32_BE( dataBuffer.Length, outMessage, position );
position += 4;
ByteWriter.WriteInt16_BE( (Int16)signatureBuffer.Length, outMessage, position );
position += 2;
Array.Copy( dataBuffer.Buffer, 0, outMessage, position, dataBuffer.Length );
position += dataBuffer.Length;
Array.Copy( signatureBuffer.Buffer, 0, outMessage, position, signatureBuffer.Length );
position += signatureBuffer.Length;
return outMessage;
}
/// <summary>
/// Decrypts a previously encrypted message.
/// </summary>
/// <remarks>
/// The expected format of the buffer is as follows:
/// - 2 bytes, an unsigned big-endian integer indicating the length of the trailer buffer size
/// - 4 bytes, an unsigned big-endian integer indicating the length of the message buffer size.
/// - 2 bytes, an unsigned big-endian integer indicating the length of the encryption padding buffer size.
/// - The trailer buffer
/// - The message buffer
/// - The padding buffer.
/// </remarks>
/// <param name="input">The packed and encrypted data.</param>
/// <returns>The original plaintext message.</returns>
public byte[] Decrypt( byte[] input )
{
SecPkgContext_Sizes sizes;
SecureBuffer trailerBuffer;
SecureBuffer dataBuffer;
SecureBuffer paddingBuffer;
SecureBufferAdapter adapter;
SecurityStatus status;
byte[] result = null;
int remaining;
int position;
int trailerLength;
int dataLength;
int paddingLength;
CheckLifecycle();
sizes = QueryBufferSizes();
// This check is required, but not sufficient. We could be stricter.
if( input.Length < 2 + 4 + 2 + sizes.SecurityTrailer )
{
throw new ArgumentException( "Buffer is too small to possibly contain an encrypted message" );
}
position = 0;
trailerLength = ByteWriter.ReadInt16_BE( input, position );
position += 2;
dataLength = ByteWriter.ReadInt32_BE( input, position );
position += 4;
paddingLength = ByteWriter.ReadInt16_BE( input, position );
position += 2;
if ( trailerLength + dataLength + paddingLength + 2 + 4 + 2 > input.Length )
{
throw new ArgumentException( "The buffer contains invalid data - the embedded length data does not add up." );
}
trailerBuffer = new SecureBuffer( new byte[trailerLength], BufferType.Token );
dataBuffer = new SecureBuffer( new byte[dataLength], BufferType.Data );
paddingBuffer = new SecureBuffer( new byte[paddingLength], BufferType.Padding );
remaining = input.Length - position;
if( trailerBuffer.Length <= remaining )
{
Array.Copy( input, position, trailerBuffer.Buffer, 0, trailerBuffer.Length );
position += trailerBuffer.Length;
remaining -= trailerBuffer.Length;
}
else
{
throw new ArgumentException( "Input is missing data - it is not long enough to contain a fully encrypted message" );
}
if( dataBuffer.Length <= remaining )
{
Array.Copy( input, position, dataBuffer.Buffer, 0, dataBuffer.Length );
position += dataBuffer.Length;
remaining -= dataBuffer.Length;
}
else
{
throw new ArgumentException( "Input is missing data - it is not long enough to contain a fully encrypted message" );
}
if( paddingBuffer.Length <= remaining )
{
Array.Copy( input, position, paddingBuffer.Buffer, 0, paddingBuffer.Length );
}
// else there was no padding.
using( adapter = new SecureBufferAdapter( new [] { trailerBuffer, dataBuffer, paddingBuffer } ) )
{
status = ContextNativeMethods.SafeDecryptMessage(
this.ContextHandle,
0,
adapter,
0
);
}
if( status != SecurityStatus.OK )
{
throw new SspiException( "Failed to encrypt message", status );
}
result = new byte[dataBuffer.Length];
Array.Copy( dataBuffer.Buffer, 0, result, 0, dataBuffer.Length );
return result;
}
/// <summary>
/// Encrypts the byte array using the context's session key.
/// </summary>
/// <remarks>
/// The structure of the returned data is as follows:
/// - 2 bytes, an unsigned big-endian integer indicating the length of the trailer buffer size
/// - 4 bytes, an unsigned big-endian integer indicating the length of the message buffer size.
/// - 2 bytes, an unsigned big-endian integer indicating the length of the encryption padding buffer size.
/// - The trailer buffer
/// - The message buffer
/// - The padding buffer.
/// </remarks>
/// <param name="input">The raw message to encrypt.</param>
/// <returns>The packed and encrypted message.</returns>
public byte[] Encrypt( byte[] input )
{
// The message is encrypted in place in the buffer we provide to Win32 EncryptMessage
SecPkgContext_Sizes sizes;
SecureBuffer trailerBuffer;
SecureBuffer dataBuffer;
SecureBuffer paddingBuffer;
SecureBufferAdapter adapter;
SecurityStatus status = SecurityStatus.InvalidHandle;
byte[] result;
CheckLifecycle();
sizes = QueryBufferSizes();
trailerBuffer = new SecureBuffer( new byte[sizes.SecurityTrailer], BufferType.Token );
dataBuffer = new SecureBuffer( new byte[input.Length], BufferType.Data );
paddingBuffer = new SecureBuffer( new byte[sizes.BlockSize], BufferType.Padding );
Array.Copy( input, dataBuffer.Buffer, input.Length );
using( adapter = new SecureBufferAdapter( new[] { trailerBuffer, dataBuffer, paddingBuffer } ) )
{
status = ContextNativeMethods.SafeEncryptMessage(
this.ContextHandle,
0,
adapter,
0
);
}
if( status != SecurityStatus.OK )
{
throw new SspiException( "Failed to encrypt message", status );
}
int position = 0;
// Enough room to fit:
// -- 2 bytes for the trailer buffer size
// -- 4 bytes for the message size
// -- 2 bytes for the padding size.
// -- The encrypted message
result = new byte[2 + 4 + 2 + trailerBuffer.Length + dataBuffer.Length + paddingBuffer.Length];
ByteWriter.WriteInt16_BE( (short)trailerBuffer.Length, result, position );
position += 2;
ByteWriter.WriteInt32_BE( dataBuffer.Length, result, position );
position += 4;
ByteWriter.WriteInt16_BE( (short)paddingBuffer.Length, result, position );
position += 2;
Array.Copy( trailerBuffer.Buffer, 0, result, position, trailerBuffer.Length );
position += trailerBuffer.Length;
Array.Copy( dataBuffer.Buffer, 0, result, position, dataBuffer.Length );
position += dataBuffer.Length;
Array.Copy( paddingBuffer.Buffer, 0, result, position, paddingBuffer.Length );
position += paddingBuffer.Length;
return result;
}
/// <summary>
/// Safely invokes the native VerifySignature function, making sure that handle ref counting is
/// performed in a proper CER.
/// </summary>
/// <param name="handle"></param>
/// <param name="qualityOfProtection"></param>
/// <param name="adapter"></param>
/// <param name="sequenceNumber"></param>
/// <returns></returns>
internal static SecurityStatus SafeVerifySignature(
SafeContextHandle handle,
int qualityOfProtection,
SecureBufferAdapter adapter,
int sequenceNumber )
{
bool gotRef = false;
SecurityStatus status = SecurityStatus.InternalError;
RuntimeHelpers.PrepareConstrainedRegions();
try
{
handle.DangerousAddRef( ref gotRef );
}
catch ( Exception )
{
if ( gotRef )
{
handle.DangerousRelease();
gotRef = false;
}
throw;
}
finally
{
if ( gotRef )
{
status = ContextNativeMethods.VerifySignature(
ref handle.rawHandle,
adapter.Handle,
sequenceNumber,
qualityOfProtection
);
handle.DangerousRelease();
}
}
return status;
}
/// <summary>
/// Performs and continues the authentication cycle.
/// </summary>
/// <remarks>
/// This method is performed iteratively to start, continue, and end the authentication cycle with the
/// server. Each stage works by acquiring a token from one side, presenting it to the other side
/// which in turn may generate a new token.
///
/// The cycle typically starts and ends with the client. On the first invocation on the client,
/// no server token exists, and null is provided in its place. The client returns its status, providing
/// its output token for the server. The server accepts the clients token as input and provides a
/// token as output to send back to the client. This cycle continues until the server and client
/// both indicate, typically, a SecurityStatus of 'OK'.
/// </remarks>
/// <param name="serverToken">The most recently received token from the server, or null if beginning
/// the authentication cycle.</param>
/// <param name="outToken">The clients next authentication token in the authentication cycle.</param>
/// <returns>A status message indicating the progression of the authentication cycle.
/// A status of 'OK' indicates that the cycle is complete, from the client's perspective. If the outToken
/// is not null, it must be sent to the server.
/// A status of 'Continue' indicates that the output token should be sent to the server and
/// a response should be anticipated.</returns>
public SecurityStatus Init( byte[] serverToken, out byte[] outToken )
{
TimeStamp rawExpiry = new TimeStamp();
SecurityStatus status;
SecureBuffer outTokenBuffer;
SecureBufferAdapter outAdapter;
SecureBuffer serverBuffer;
SecureBufferAdapter serverAdapter;
if( this.Disposed )
{
throw new ObjectDisposedException( "ClientContext" );
}
else if( ( serverToken != null ) && ( this.ContextHandle.IsInvalid ) )
{
throw new InvalidOperationException( "Out-of-order usage detected - have a server token, but no previous client token had been created." );
}
else if( ( serverToken == null ) && ( this.ContextHandle.IsInvalid == false ) )
{
throw new InvalidOperationException( "Must provide the server's response when continuing the init process." );
}
// The security package tells us how big its biggest token will be. We'll allocate a buffer
// that size, and it'll tell us how much it used.
outTokenBuffer = new SecureBuffer(
new byte[ this.Credential.PackageInfo.MaxTokenLength ],
BufferType.Token
);
serverBuffer = null;
if ( serverToken != null )
{
serverBuffer = new SecureBuffer( serverToken, BufferType.Token );
}
// Some notes on handles and invoking InitializeSecurityContext
// - The first time around, the phContext parameter (the 'old' handle) is a null pointer to what
// would be an RawSspiHandle, to indicate this is the first time it's being called.
// The phNewContext is a pointer (reference) to an RawSspiHandle struct of where to write the
// new handle's values.
// - The next time you invoke ISC, it takes a pointer to the handle it gave you last time in phContext,
// and takes a pointer to where it should write the new handle's values in phNewContext.
// - After the first time, you can provide the same handle to both parameters. From MSDN:
// "On the second call, phNewContext can be the same as the handle specified in the phContext
// parameter."
// It will overwrite the handle you gave it with the new handle value.
// - All handle structures themselves are actually *two* pointer variables, eg, 64 bits on 32-bit
// Windows, 128 bits on 64-bit Windows.
// - So in the end, on a 64-bit machine, we're passing a 64-bit value (the pointer to the struct) that
// points to 128 bits of memory (the struct itself) for where to write the handle numbers.
using ( outAdapter = new SecureBufferAdapter( outTokenBuffer ) )
{
if ( this.ContextHandle.IsInvalid )
{
status = ContextNativeMethods.InitializeSecurityContext_1(
ref this.Credential.Handle.rawHandle,
IntPtr.Zero,
this.serverPrinc,
this.requestedAttribs,
0,
SecureBufferDataRep.Network,
IntPtr.Zero,
0,
ref this.ContextHandle.rawHandle,
outAdapter.Handle,
ref this.finalAttribs,
ref rawExpiry
);
}
else
{
using ( serverAdapter = new SecureBufferAdapter( serverBuffer ) )
{
status = ContextNativeMethods.InitializeSecurityContext_2(
ref this.Credential.Handle.rawHandle,
ref this.ContextHandle.rawHandle,
this.serverPrinc,
this.requestedAttribs,
0,
SecureBufferDataRep.Network,
serverAdapter.Handle,
0,
ref this.ContextHandle.rawHandle,
outAdapter.Handle,
ref this.finalAttribs,
ref rawExpiry
);
}
}
}
if( status.IsError() == false )
{
if( status == SecurityStatus.OK )
{
base.Initialize( rawExpiry.ToDateTime() );
}
outToken = null;
if( outTokenBuffer.Length != 0 )
{
outToken = new byte[outTokenBuffer.Length];
Array.Copy( outTokenBuffer.Buffer, outToken, outToken.Length );
}
}
else
{
throw new SspiException( "Failed to invoke InitializeSecurityContext for a client", status );
}
return status;
}
