/// <param name="data"></param>
/// <param name="cryptoKey"></param>
/// <param name="IVec"></param>
/// <exception cref="UnsupportedEncodingException"></exception>
/// <returns></returns>
public static byte[] decryptData(byte[] data, byte[] cryptoKey, byte[] IVec)
{
return(AESHelper.decryptData(data, cryptoKey, IVec, true)); // true =^ PKCS7 padding
}
public static byte[] DecryptFile(
string encryptedFilePath,
byte[] fileCryptoKey,
string baseIVec,
int blockSize,
int offset,
int padding)
{
Console.WriteLine($"AES Decryption of file '{encryptedFilePath}' started");
if (fileCryptoKey.Length <= 0 || blockSize <= 0)
{
throw new Exception("Crypto key for file can't be empty and block size must be bigger than zero");
}
// read the encrypted file
byte[] fileBytes;
try
{
fileBytes = File.ReadAllBytes(Path.GetFullPath(encryptedFilePath));
}
catch (IOException e)
{
throw new Exception("Could not read file", e);
}
// IVec in file header is base 64 encoded
byte[] decodedFileIV = Base64Helper.decode(baseIVec);
// report initial status
int fileSize = fileBytes.Length;
long fileSizeFivePer = Convert.ToInt64(Math.Floor(fileSize * 0.05)); // 5% of file size; for status reporting
string byteProgress = $" (0 / {fileSize} bytes)";
StringBuilder routeString = new StringBuilder();
StringBuilder spaceString = new StringBuilder();
for (int i = 0; i < 20; i++)
{
spaceString.Append(" ");
}
Console.WriteLine($"Progress: [{spaceString}]{byteProgress}");
// decrypt each block separately with its own initialization vector
int blockNo = 0;
byte[] result = new byte[fileSize - offset - padding];
for (int byteNo = offset, nextStatusThreshold = offset, currentStep = 0; byteNo <= fileSize; byteNo += blockSize, ++blockNo)
{
byte[] blockIVec = AESHelper.ComputeBlockIVec(decodedFileIV, blockNo, fileCryptoKey);
// get the input data for the current block (the last block may be shorter than [blockSize] bytes)
int end = (byteNo + blockSize >= fileSize) ? fileSize : byteNo + blockSize;
byte[] blockInput = new byte[end - byteNo];
BlockCopy(fileBytes, byteNo, blockInput, 0, end - byteNo);
PaddingMode currentPadding = (end == fileSize && padding > 0) ? PaddingMode.PKCS7 : PaddingMode.None;
// get the decrypted data for this block ...
byte[] decryptedBlock = AESHelper.DecryptData(blockInput, fileCryptoKey, blockIVec, true, currentPadding);
// ... and append it to the previous data
BlockCopy(decryptedBlock, 0, result, byteNo - offset, decryptedBlock.Length);
// report intermediate status every 5%
if (byteNo > nextStatusThreshold)
{
int steps = byteNo / nextStatusThreshold;
nextStatusThreshold += Convert.ToInt32(fileSizeFivePer * steps);
currentStep += steps;
byteProgress = $" ({byteNo} / {fileSize} bytes)";
routeString.Length = 0;
for (int i = 0; i < currentStep; i++)
{
routeString.Append("#");
}
spaceString.Length = 0;
for (int i = 0; i < 20 - currentStep; i++)
{
spaceString.Append(" ");
}
Console.WriteLine($"Progress: [{routeString}{spaceString}]{byteProgress}");
}
}
// newline after Status report
byteProgress = $" ({fileSize} / {fileSize} bytes)";
routeString.Length = 0;
for (int i = 0; i < 20; i++)
{
routeString.Append("#");
}
Console.WriteLine($"Progress: [{routeString}]{byteProgress}");
Console.WriteLine("AES decryption of file finished");
return(result);
}
/// <exception cref="UnsupportedEncodingException"></exception>
public static byte[] decryptFile(
string encryptedFilePath,
byte[] fileCryptoKey,
string baseIVec,
int blockSize,
int offset,
int padding)
{
Console.WriteLine("AES Decryption of file '" + encryptedFilePath + "' started");
if (fileCryptoKey.Length <= 0 || blockSize <= 0)
{
throw new SystemException("Crypto key for file can't be empty and block size must be bigger than zero");
}
// read the encrypted file
byte[] fileBytes;
try
{
fileBytes = File.ReadAllBytes(Path.GetFullPath(encryptedFilePath));
}
catch (IOException e)
{
throw new SystemException("Could not read file", e);
}
// IVec in file header is base 64 encoded
byte[] decodedFileIV = Base64Helper.decode(baseIVec);
// report initial status
int fileSize = fileBytes.Length;
long fileSizeFivePer = Convert.ToInt64(Math.Floor(fileSize * 0.05)); // 5% of file size; for status reporting
string byteProgress = " (0 / " + fileSize + " bytes)";
StringBuilder routeString = new StringBuilder();
StringBuilder spaceString = new StringBuilder();
for (int i = 0; i < 20; i++)
{
spaceString.Append(" ");
}
Console.WriteLine("Progress: [{0}]{1}", spaceString, byteProgress);
// decrypt each block separately with its own initialization vector
int blockNo = 0;
byte[] result = new byte[fileSize - offset - padding];
for (int byteNo = offset, nextStatusThreshold = offset, currentStep = 0; byteNo <= fileSize; byteNo += blockSize, ++blockNo)
{
byte[] blockIVec = AESHelper.computeBlockIVec(decodedFileIV, blockNo, fileCryptoKey);
// get the input data for the current block (the last block may be shorter than [blockSize] bytes)
int end = (byteNo + blockSize >= fileSize) ? fileSize : byteNo + blockSize;
byte[] blockInput = new byte[end - byteNo];
System.Buffer.BlockCopy(fileBytes, byteNo, blockInput, 0, end - byteNo);
// PKCS7 padding for the last block if a cipher padding size greater than 0 was specified in file header
// Note: the only differnce between PKCS5 and 7 is the block size (8 and 0-255 bytes respectively),
// Java only offers the 'PKCS5PADDING' identifier (legacy from the time only 8 byte block ciphers were available)
bool currentPadding = (end == fileSize && padding > 0) ? true : false;
// get the decrypted data for this block ...
byte[] decryptedBlock = AESHelper.decryptData(blockInput, fileCryptoKey, blockIVec, currentPadding);
// ... and append it to the previous data
System.Buffer.BlockCopy(decryptedBlock, 0, result, byteNo - offset, decryptedBlock.Length);
// report intermediate status every 5%
if (byteNo > nextStatusThreshold)
{
int steps = byteNo / nextStatusThreshold;
nextStatusThreshold += Convert.ToInt32(fileSizeFivePer * steps);
currentStep += steps;
byteProgress = " (" + byteNo + " / " + fileSize + " bytes)";
routeString.Length = 0;
for (int i = 0; i < currentStep; i++)
{
routeString.Append("#");
}
spaceString.Length = 0;
for (int i = 0; i < 20 - currentStep; i++)
{
spaceString.Append(" ");
}
Console.WriteLine("Progress: [{0}{1}]{2}", routeString, spaceString, byteProgress);
}
}
// newline after Status report
byteProgress = " (" + fileSize + " / " + fileSize + " bytes)";
routeString.Length = 0;
for (int i = 0; i < 20; i++)
{
routeString.Append("#");
}
Console.WriteLine("Progress: [{0}]{1}", routeString, byteProgress);
Console.WriteLine("AES decryption of file finished");
return(result);
}
static void Main(string[] args)
{
if (args.Length < 3)
{
Console.WriteLine("Usage: bc-file-decryptor \n"
+ "[path to .bckey file] "
+ "[path to encrypted file] "
+ "[pwd] "
+ "[path for output (optional)]");
return;
}
try
{
Console.WriteLine("Decryption process started");
// ============================================
// AES decryption of private key in .bckey file
// =============================================
// collect information about the user account
AccountData accountInfo = new AccountData();
accountInfo.ParseBCKeyFile(args[0]);
accountInfo.Password = args[2];
// decrypt the private key from the .bckey file
byte[] decryptedPrivateKey = AESHelper.DecryptDataPBKDF2(
accountInfo.EncryptedPrivateKey, accountInfo.Password,
accountInfo.PBKDF2Salt, accountInfo.PBKDF2Iterations
);
// =============================================
// RSA decryption of file information (header)
// =============================================
// collect information about the file to be decrypted
FileData fileData = new FileData();
string outputFilePath = args.Length > 3 ? args[3] : "";
fileData.ParseHeader(args[1], outputFilePath);
// decrypt the file key (from the header) used for decryption of file data
byte[] decryptedFileKey = RSAHelper.DecryptData(fileData.EncryptedFileKey, decryptedPrivateKey);
byte[] fileCryptoKey = new byte[32];
BlockCopy(decryptedFileKey, 32, fileCryptoKey, 0, 32);
// =============================================
// AES decryption of encrypted file
// =============================================
// decrypt the file data ...
byte[] decryptedFileBytes = AESHelper.DecryptFile(
fileData.EncryptedFilePath, fileCryptoKey, fileData.BaseIVec,
fileData.BlockSize, fileData.HeaderLen, fileData.CipherPadding);
File.WriteAllBytes(Path.GetFullPath(fileData.OutputFilePath), decryptedFileBytes);
Console.WriteLine($"Successfully decrypted file '{fileData.EncryptedFilePath}', "
+ $"output: '{fileData.OutputFilePath}'");
}
catch (Exception e)
{
Console.WriteLine(e.Message);
if (e.StackTrace != null)
{
Console.WriteLine(e.StackTrace);
}
}
}
