/// <summary>
/// PGP-decrypt all data from source stream into destination stream
/// </summary>
/// <param name="privatekeysource">Input stream containing private keyring bundle</param>
/// <param name="privatekeypassphrase">Passphrase to access private key (if required)</param>
/// <param name="encryptedinput">Input stream containing source data to be decrypted</param>
/// <param name="clearoutput">Output stream to receive decrypted data</param>
/// <remarks>
/// Destination data stream will be written asynchronously, but source data stream will be read synchronously (due to limitation in PGP
/// library; all source data must be available to perform decryption, but source library does not provide async option). If this is a concern,
/// caller should consider asynchronously pulling source data into local stream first and passing local stream to this function (if increased
/// use of memory outweighs waiting for blocked thread to perform I/O)
/// </remarks>
public static async Task Decrypt(Stream privatekeysource, string privatekeypassphrase, Stream encryptedinput, Stream clearoutput)
{
// Create object factory using DecoderStream to read PGP data from source, use factory to extract encrypted data:
using (var decoder = PgpUtilities.GetDecoderStream(encryptedinput))
{
var encrypteddata = new PgpObjectFactory(decoder).GetEncryptedData() ?? throw new ArgumentException("No PGP-encrypted data found");
// Extract private key from key source (using key ID required by encrypted data object), use to open clear stream:
using (var clearsource = encrypteddata.GetDataStream(await ExtractPrivateKey(privatekeysource, privatekeypassphrase, encrypteddata.KeyId)))
{
// Create new object factory from clear stream and use to write cleartext data to destination:
await new PgpObjectFactory(clearsource).WriteClearData(clearoutput);
}
}
}