| public ValidateFooterChecksum ( byte chunkCount, byte chunkOverallLength, byte ephemeralKey, int footerChecksumLength ) : void | ||
| chunkCount | byte | Number of chunks in the file. |
| chunkOverallLength | byte | Length of all chunks in the file. |
| ephemeralKey | byte | A 64 byte key. |
| footerChecksumLength | int | The length of the checksum. |
| return | void | |
/// <summary>
/// Decrypts a file asynchron with libsodium and protobuf-net.
/// </summary>
/// <param name="recipientPrivateKey">A 32 byte private key.</param>
/// <param name="inputFile">An encrypted file.</param>
/// <param name="outputFolder">There the decrypted file will be stored.</param>
/// <param name="decryptionProgress">StreamCryptorTaskAsyncProgress object.</param>
/// <param name="overWrite">Overwrite the output file if it exist.</param>
/// <param name="cancellationToken">Token to request task cancellation.</param>
/// <returns>The fullpath to the decrypted file.</returns>
/// <remarks>This method needs a revision.</remarks>
/// <exception cref="ArgumentOutOfRangeException"></exception>
/// <exception cref="FileNotFoundException"></exception>
/// <exception cref="DirectoryNotFoundException"></exception>
/// <exception cref="BadLastFileChunkException"></exception>
/// <exception cref="BadFileChunkException"></exception>
/// <exception cref="BadFileFooterException"></exception>
/// <exception cref="BadFileHeaderException"></exception>
/// <exception cref="IOException"></exception>
/// <exception cref="ArgumentException"></exception>
/// <exception cref="OperationCanceledException"></exception>
public static async Task<string> DecryptFileWithStreamAsync(byte[] recipientPrivateKey, string inputFile, string outputFolder, IProgress<StreamCryptorTaskAsyncProgress> decryptionProgress = null, bool overWrite = false, CancellationToken cancellationToken = default(CancellationToken))
{
string outputFile = String.Empty;
string outputFullPath = String.Empty;
//used to check the file length of the unencrypted file, will be renamed to the outputFile (if the file is valid)
string tmpFile = String.Empty;
string tmpFullPath = String.Empty;
try
{
//validate the recipientPrivateKey
if (recipientPrivateKey == null || recipientPrivateKey.Length != ASYNC_KEY_LENGTH)
{
throw new ArgumentOutOfRangeException("recipientPrivateKey", "invalid recipientPrivateKey");
}
//validate the inputFile
if (string.IsNullOrEmpty(inputFile))
{
throw new ArgumentOutOfRangeException("inputFile", (inputFile == null) ? 0 : inputFile.Length,
string.Format("inputFile must be greater {0} in length.", 0));
}
if (!File.Exists(inputFile))
{
throw new FileNotFoundException("inputFile", "inputFile could not be found.");
}
//validate the outputFolder
if (string.IsNullOrEmpty(outputFolder) || !Directory.Exists(outputFolder))
{
throw new DirectoryNotFoundException("outputFolder must exist");
}
if (outputFolder.IndexOfAny(Path.GetInvalidPathChars()) > -1)
throw new ArgumentException("The given path to the output folder contains invalid characters!");
//get a tmp name
tmpFile = Utils.GetRandomFileName(MASKED_FILENAME_LENGTH, TEMP_FILE_EXTENSION);
tmpFullPath = Path.Combine(outputFolder, tmpFile);
using (FileStream fileStreamEncrypted = File.OpenRead(inputFile))
{
//first read the file header
EncryptedFileHeader encryptedFileHeader = Serializer.DeserializeWithLengthPrefix<EncryptedFileHeader>(fileStreamEncrypted, PrefixStyle.Base128, 1);
if (encryptedFileHeader == null)
{
throw new BadFileHeaderException("Missing file header: maybe not a StreamCryptor encrypted file");
}
//decrypt the ephemeral key with our public box
byte[] ephemeralKey = PublicKeyBox.Open(encryptedFileHeader.Key, encryptedFileHeader.EphemeralNonce, recipientPrivateKey, encryptedFileHeader.SenderPublicKey);
//validate our file header
encryptedFileHeader.ValidateHeaderChecksum(ephemeralKey, HEADER_CHECKSUM_LENGTH);
//check file header for compatibility
if ((encryptedFileHeader.Version >= MIN_VERSION) && (encryptedFileHeader.BaseNonce.Length == CHUNK_BASE_NONCE_LENGTH))
{
long overallChunkLength = 0;
long overallBytesRead = 0;
//restore the original file name
byte[] decryptedPaddedFileName = SecretBox.Open(encryptedFileHeader.Filename, encryptedFileHeader.FilenameNonce, Utils.GetEphemeralEncryptionKey(ephemeralKey));
//remove the padding
outputFile = Utils.PaddedByteArrayToString(decryptedPaddedFileName);
//check the decrypted outputFile name for invalid characters to prevent directory traversal
if (outputFile.IndexOfAny(Path.GetInvalidFileNameChars()) > -1)
throw new ArgumentException("The given name of the decrypted output filename contains invalid characters!");
outputFullPath = Path.Combine(outputFolder, outputFile);
//check for the correct result of Path.Combine
if (!outputFullPath.StartsWith(outputFolder))
throw new ArgumentException("The given output path seems to be bad!");
//keep the position for the footer
long fileStreamEncryptedPosition = 0;
int chunkNumber = CHUNK_COUNT_START;
//write the file to the tmpFullPath
using (FileStream fileStreamUnencrypted = File.OpenWrite(tmpFullPath))
{
//start reading the chunks
EncryptedFileChunk encryptedFileChunk = new EncryptedFileChunk();
while ((encryptedFileChunk = Serializer.DeserializeWithLengthPrefix<EncryptedFileChunk>(fileStreamEncrypted, PrefixStyle.Base128, 2)) != null)
{
//cancel the task if requested
cancellationToken.ThrowIfCancellationRequested();
//indicates if ChunkIsLast was found, to prepend more than one last chnunks.
bool isLastChunkFound = false;
byte[] chunkNonce = new byte[NONCE_LENGTH];
//check if this is the last chunk
if (encryptedFileChunk.ChunkIsLast)
{
if (!isLastChunkFound)
{
//last
chunkNonce = GetChunkNonce(encryptedFileHeader.BaseNonce, chunkNumber, true);
isLastChunkFound = true;
}
else
{
throw new BadLastFileChunkException("there are more than one last chunk, file could be damaged or manipulated!");
}
}
else
{
//there will propably come more
chunkNonce = GetChunkNonce(encryptedFileHeader.BaseNonce, chunkNumber, false);
}
//check the current chunk checksum
encryptedFileChunk.ValidateChunkChecksum(ephemeralKey, CHUNK_CHECKSUM_LENGTH);
byte[] decrypted = SecretBox.Open(encryptedFileChunk.Chunk, chunkNonce, Utils.GetEphemeralEncryptionKey(ephemeralKey));
await fileStreamUnencrypted.WriteAsync(decrypted, 0, decrypted.Length, cancellationToken).ConfigureAwait(false);
overallBytesRead += (long)decrypted.Length;
chunkNumber++;
overallChunkLength += encryptedFileChunk.ChunkLength;
fileStreamEncryptedPosition = fileStreamEncrypted.Position;
//report status
if (decryptionProgress != null)
{
var args = new StreamCryptorTaskAsyncProgress();
args.ProgressPercentage = (int)(encryptedFileHeader.UnencryptedFileLength <= 0 ? 0 : (100 * overallBytesRead) / encryptedFileHeader.UnencryptedFileLength);
decryptionProgress.Report(args);
}
}
}
//set the last position
fileStreamEncrypted.Position = fileStreamEncryptedPosition;
//prepare the EncryptedFileFooter
EncryptedFileFooter encryptedFileFooter = new EncryptedFileFooter();
//get the file footer and validate him
encryptedFileFooter = Serializer.DeserializeWithLengthPrefix<EncryptedFileFooter>(fileStreamEncrypted, PrefixStyle.Base128, 3);
if (encryptedFileFooter == null)
{
throw new BadFileFooterException("Missing file footer: file could be damaged or manipulated!");
}
//validate the footer checksum
encryptedFileFooter.ValidateFooterChecksum(BitConverter.GetBytes(chunkNumber), BitConverter.GetBytes(overallChunkLength), ephemeralKey, FOOTER_CHECKSUM_LENGTH);
}
else
{
throw new BadFileHeaderException("Incompatible file header: maybe different library version!");
}
//check the produced output for the correct length
if (encryptedFileHeader.UnencryptedFileLength == new FileInfo(tmpFullPath).Length)
{
//check if the new output file already exists
if (File.Exists(outputFullPath))
{
if (!overWrite)
{
//we don`t overwrite the file
throw new IOException("Decrypted file aleary exits, won`t overwrite");
}
else
{
//just delete the output file, so we can write a new one
File.Delete(outputFullPath);
}
}
File.Move(tmpFullPath, outputFullPath);
}
else
{
//File is not valid (return null)
outputFile = null;
File.Delete(tmpFullPath);
}
}
}
catch (AggregateException ex)
{
//delete the temp file
File.Delete(tmpFullPath);
//and throw the exception
ExceptionDispatchInfo.Capture(ex).Throw();
}
catch (OperationCanceledException ex)
{
//delete the temp file
File.Delete(tmpFullPath);
//and throw the exception
ExceptionDispatchInfo.Capture(ex).Throw();
}
return outputFile;
}
/// <summary>
/// Decrypts a file asynchron into memory with libsodium and protobuf-net.
/// </summary>
/// <param name="recipientPrivateKey">A 32 byte private key.</param>
/// <param name="inputFile">An encrypted file.</param>
/// <param name="decryptionProgress">StreamCryptorTaskAsyncProgress object.</param>
/// <param name="cancellationToken">Token to request task cancellation.</param>
/// <returns>A DecryptedFile object.</returns>
/// <remarks>This method can throw an OutOfMemoryException when there is not enough ram to hold the DecryptedFile!</remarks>
/// <exception cref="ArgumentOutOfRangeException"></exception>
/// <exception cref="FileNotFoundException"></exception>
/// <exception cref="BadLastFileChunkException"></exception>
/// <exception cref="BadFileChunkException"></exception>
/// <exception cref="BadFileFooterException"></exception>
/// <exception cref="BadFileHeaderException"></exception>
/// <exception cref="IOException"></exception>
/// <exception cref="OutOfMemoryException"></exception>
/// <exception cref="OperationCanceledException"></exception>
public static async Task<DecryptedFile> DecryptFileWithStreamAsync(byte[] recipientPrivateKey, string inputFile, IProgress<StreamCryptorTaskAsyncProgress> decryptionProgress = null, CancellationToken cancellationToken = default(CancellationToken))
{
DecryptedFile decryptedFile = new DecryptedFile();
try
{
//validate the recipientPrivateKey
if (recipientPrivateKey == null || recipientPrivateKey.Length != ASYNC_KEY_LENGTH)
{
throw new ArgumentOutOfRangeException("recipientPrivateKey", "invalid recipientPrivateKey");
}
//validate the inputFile
if (string.IsNullOrEmpty(inputFile))
{
throw new ArgumentOutOfRangeException("inputFile", (inputFile == null) ? 0 : inputFile.Length,
string.Format("inputFile must be greater {0} in length.", 0));
}
if (!File.Exists(inputFile))
{
throw new FileNotFoundException("inputFile", "inputFile could not be found.");
}
using (FileStream fileStreamEncrypted = File.OpenRead(inputFile))
{
//first read the file header
EncryptedFileHeader encryptedFileHeader = new EncryptedFileHeader();
encryptedFileHeader = Serializer.DeserializeWithLengthPrefix<EncryptedFileHeader>(fileStreamEncrypted, PrefixStyle.Base128, 1);
//decrypt the ephemeral key with our public box
byte[] ephemeralKey = PublicKeyBox.Open(encryptedFileHeader.Key, encryptedFileHeader.EphemeralNonce, recipientPrivateKey, encryptedFileHeader.SenderPublicKey);
//validate our file header
encryptedFileHeader.ValidateHeaderChecksum(ephemeralKey, HEADER_CHECKSUM_LENGTH);
//check file header for compatibility
if ((encryptedFileHeader.Version >= MIN_VERSION) && (encryptedFileHeader.BaseNonce.Length == CHUNK_BASE_NONCE_LENGTH))
{
long overallChunkLength = 0;
long overallBytesRead = 0;
//restore the original file name
byte[] encryptedPaddedFileName = SecretBox.Open(encryptedFileHeader.Filename, encryptedFileHeader.FilenameNonce, Utils.GetEphemeralEncryptionKey(ephemeralKey));
//remove the padding
decryptedFile.FileName = Utils.PaddedByteArrayToString(encryptedPaddedFileName);
//keep the position for the footer
long fileStreamEncryptedPosition = 0;
int chunkNumber = CHUNK_COUNT_START;
//write the file to the tmpFullPath
using (MemoryStream fileStreamUnencrypted = new MemoryStream())
{
//start reading the chunks
EncryptedFileChunk encryptedFileChunk = new EncryptedFileChunk();
while ((encryptedFileChunk = Serializer.DeserializeWithLengthPrefix<EncryptedFileChunk>(fileStreamEncrypted, PrefixStyle.Base128, 2)) != null)
{
//cancel the task if requested
cancellationToken.ThrowIfCancellationRequested();
//indicates if ChunkIsLast was found, to prepend more than one last chnunks.
bool isLastChunkFound = false;
byte[] chunkNonce = new byte[NONCE_LENGTH];
//check if this is the last chunk
if (encryptedFileChunk.ChunkIsLast)
{
if (!isLastChunkFound)
{
//last
chunkNonce = GetChunkNonce(encryptedFileHeader.BaseNonce, chunkNumber, true);
isLastChunkFound = true;
}
else
{
throw new BadLastFileChunkException("there are more than one last chunk, file could be damaged or manipulated!");
}
}
else
{
//there will propably come more
chunkNonce = GetChunkNonce(encryptedFileHeader.BaseNonce, chunkNumber);
}
//check the current chunk checksum
encryptedFileChunk.ValidateChunkChecksum(ephemeralKey, CHUNK_CHECKSUM_LENGTH);
byte[] decrypted = SecretBox.Open(encryptedFileChunk.Chunk, chunkNonce, Utils.GetEphemeralEncryptionKey(ephemeralKey));
await fileStreamUnencrypted.WriteAsync(decrypted, 0, decrypted.Length, cancellationToken).ConfigureAwait(false);
overallBytesRead += (long)decrypted.Length;
chunkNumber++;
overallChunkLength += encryptedFileChunk.ChunkLength;
fileStreamEncryptedPosition = fileStreamEncrypted.Position;
//report status
if (decryptionProgress != null)
{
var args = new StreamCryptorTaskAsyncProgress();
args.ProgressPercentage = (int)(encryptedFileHeader.UnencryptedFileLength <= 0 ? 0 : (100 * overallBytesRead) / encryptedFileHeader.UnencryptedFileLength);
decryptionProgress.Report(args);
}
}
decryptedFile.FileData = fileStreamUnencrypted.ToArray();
decryptedFile.FileSize = decryptedFile.FileData.Length;
}
//set the last position
fileStreamEncrypted.Position = fileStreamEncryptedPosition;
//prepare the EncryptedFileFooter
EncryptedFileFooter encryptedFileFooter = new EncryptedFileFooter();
//get the file footer and validate him
encryptedFileFooter = Serializer.DeserializeWithLengthPrefix<EncryptedFileFooter>(fileStreamEncrypted, PrefixStyle.Base128, 3);
if (encryptedFileFooter == null)
{
throw new BadFileFooterException("Missing file footer: file could be damaged or manipulated!");
}
//validate the footer checksum
encryptedFileFooter.ValidateFooterChecksum(BitConverter.GetBytes(chunkNumber), BitConverter.GetBytes(overallChunkLength), ephemeralKey, FOOTER_CHECKSUM_LENGTH);
}
else
{
throw new BadFileHeaderException("Incompatible file header: maybe different library version!");
}
//check the produced output for the correct length
if (encryptedFileHeader.UnencryptedFileLength != decryptedFile.FileSize)
{
//File is not valid (return null)
decryptedFile = null;
}
}
}
catch (AggregateException ex)
{
//and throw the exception
ExceptionDispatchInfo.Capture(ex).Throw();
}
return decryptedFile;
}
