public static void SignStream(
string Username,
string Domain,
string Password,
Stream DataToSign, //The stream to read the data to be signed from
Stream SignatureData //The stream to write the signature data to
)
{
if (string.IsNullOrEmpty(Username))
{
throw new ArgumentNullException("Username");
}
if (string.IsNullOrEmpty(Password))
{
throw new ArgumentNullException("Password");
}
if (DataToSign == null)
{
throw new ArgumentNullException("DataToSign");
}
if (SignatureData == null)
{
throw new ArgumentNullException("SignatureData");
}
//Make sure the SAPI library is loaded into the current process
SAPIInit();
//Instantiate SAPI object
SAPICrypt SAPI = new SAPICrypt();
SESHandle hSes = null;
int rc = 0;
if ((rc = SAPI.HandleAcquire(out hSes)) != 0)
{
throw new Exception(string.Format(
"Memory allocation error (#{0})", rc.ToString("X")));
}
if ((rc = SAPI.Logon(hSes, Username, Domain, Password)) != 0)
{
SAPI.HandleRelease(hSes);
throw new Exception(string.Format(
"Failed to authenticate the user(#{0})", rc.ToString("X")));
}
//Allocate new signing context
SAPIContext ctxBuffSign = new SAPIContext();
if ((rc = SAPI.BufferSignInit(hSes, ctxBuffSign, 0)) != 0)
{
SAPI.Logoff(hSes);
SAPI.HandleRelease(hSes);
throw new Exception(string.Format(
"Failed to initialize buffer signing process(#{0})", rc.ToString("X")));
}
int remaining = (int)DataToSign.Length;
//Check that the stream is not empty
if ((int)DataToSign.Length < 1)
{
SAPI.Logoff(hSes);
SAPI.HandleRelease(hSes);
throw new Exception("Cannot sign empty stream!");
}
int chunkMaxSize = 1 << 20; //1MB
//Calculate first chunk size
int chunkSize = remaining < chunkMaxSize ?
remaining : chunkMaxSize;
while (remaining > 0)
{
Array chunk = new byte[chunkSize]; //Read in chunks of 1MB
int read = DataToSign.Read((byte[])chunk, 0, chunkSize);
if (read <= 0)
{
throw new EndOfStreamException(String.Format("End of stream reached with {0} bytes left to read", remaining));
}
//Build SAPI-Compatible bytes array
SAPIByteArray tmpBuff = new SAPIByteArray();
tmpBuff.FromArray(ref chunk);
//Add read buffer to the signature calculation
if ((rc = SAPI.BufferSignCont(hSes, ctxBuffSign, tmpBuff)) != 0)
{
SAPI.ContextRelease(ctxBuffSign);
SAPI.Logoff(hSes);
SAPI.HandleRelease(hSes);
throw new Exception(string.Format(
"An error occured while calculating the digital signature (#{0})", rc.ToString("X")));
}
remaining -= read;
chunkSize = Math.Min(remaining, chunkSize);
}
SAPIByteArray signature = new SAPIByteArray();
//Get the final signature
if ((rc = SAPI.BufferSignEnd(hSes, ctxBuffSign, signature)) != 0)
{
SAPI.ContextRelease(ctxBuffSign);
SAPI.Logoff(hSes);
SAPI.HandleRelease(hSes);
throw new Exception(string.Format(
"Failed to sign the data (#{0})", rc.ToString("X")));
}
//Write signature data to the stream
byte[] tmpSig = (byte[])signature.ToArray();
SignatureData.Write(tmpSig, 0, tmpSig.Length);
//Cleanup memory
SAPI.ContextRelease(ctxBuffSign);
SAPI.Logoff(hSes);
SAPI.HandleRelease(hSes);
}