public static void Initialize(string inputFilePath, string outputFilePath, byte[] keyEncryptionKey)
{
byte[] dataEncryptionKey = new byte[Constants.EncryptionKeyLength];
try
{
byte[] encryptedHeader = FileHeaders.ReadEncryptedHeader(inputFilePath);
byte[] nonce = FileHeaders.ReadNonce(inputFilePath);
byte[] header = DecryptFileHeader(inputFilePath, encryptedHeader, nonce, keyEncryptionKey);
if (header == null)
{
throw new ArgumentException("Incorrect password/keyfile or this file has been tampered with.");
}
ChunkHandling.ValidateKeyCommitmentBlock(header);
int lastChunkLength = FileHeaders.GetLastChunkLength(header);
int fileNameLength = FileHeaders.GetFileNameLength(header);
dataEncryptionKey = FileHeaders.GetDataEncryptionKey(header);
Utilities.ZeroArray(header);
using (var inputFile = new FileStream(inputFilePath, FileMode.Open, FileAccess.Read, FileShare.Read, Constants.FileStreamBufferSize, FileOptions.SequentialScan))
using (var outputFile = new FileStream(outputFilePath, FileMode.Create, FileAccess.ReadWrite, FileShare.Read, Constants.FileStreamBufferSize, FileOptions.SequentialScan))
{
nonce = Sodium.Utilities.Increment(nonce);
byte[] additionalData = ChunkHandling.GetPreviousPoly1305Tag(encryptedHeader);
Decrypt(inputFile, outputFile, nonce, dataEncryptionKey, additionalData, lastChunkLength);
}
Finalize(inputFilePath, outputFilePath, fileNameLength);
}
catch (Exception ex) when(ExceptionFilters.Cryptography(ex))
{
Utilities.ZeroArray(dataEncryptionKey);
throw;
}
}
private static byte[] Decrypt(byte[] passwordBytes, byte[] privateKey)
{
byte[] keyAlgorithm = GetKeyAlgorithm(privateKey);
byte[] keyVersion = GetKeyVersion(privateKey);
byte[] salt = GetSalt(privateKey);
byte[] nonce = GetNonce(privateKey);
byte[] additionalData = Utilities.ConcatArrays(keyAlgorithm, keyVersion);
byte[] encryptedPrivateKey = GetEncryptedPrivateKey(privateKey);
byte[] key = Argon2.DeriveKey(passwordBytes, salt);
Utilities.ZeroArray(passwordBytes);
byte[] decryptedPrivateKey = SecretAeadXChaCha20Poly1305.Decrypt(encryptedPrivateKey, nonce, key, additionalData);
Utilities.ZeroArray(key);
ChunkHandling.ValidateKeyCommitmentBlock(decryptedPrivateKey);
return(ChunkHandling.RemoveKeyCommitmentBlock(decryptedPrivateKey));
}
private static void Decrypt(FileStream inputFile, FileStream outputFile, byte[] nonce, byte[] dataEncryptionKey, byte[] additionalData, int lastChunkLength)
{
int headersLength = FileHeaders.GetHeadersLength();
inputFile.Seek(headersLength, SeekOrigin.Begin);
const int offset = 0;
byte[] ciphertextChunk = new byte[Constants.TotalChunkLength];
while (inputFile.Read(ciphertextChunk, offset, ciphertextChunk.Length) > 0)
{
byte[] plaintextChunk = SecretAeadXChaCha20Poly1305.Decrypt(ciphertextChunk, nonce, dataEncryptionKey, additionalData);
ChunkHandling.ValidateKeyCommitmentBlock(plaintextChunk);
nonce = Sodium.Utilities.Increment(nonce);
additionalData = ChunkHandling.GetPreviousPoly1305Tag(ciphertextChunk);
plaintextChunk = ChunkHandling.RemoveKeyCommitmentBlock(plaintextChunk);
outputFile.Write(plaintextChunk, offset, plaintextChunk.Length);
}
outputFile.SetLength((outputFile.Length - Constants.FileChunkSize) + lastChunkLength);
Utilities.ZeroArray(dataEncryptionKey);
}
