public static long EncryptFile(System.IO.FileInfo SourceFile, FileStream DestinationFile, string[] Recipients, Keys SenderKeys)
{
// crypto variables
// THESE SHOULD BE RANDOM!
byte[] fileNonce = Utilities.GenerateRandomBytes(16);
byte[] fileKey = Utilities.GenerateRandomBytes(32);
Keys ephemeral = new Keys(true);
// these are dependant on recipients
byte[] sharedKey = null;
// validate parameters
//process chunks
Blake2sCSharp.Hasher b2s = Blake2sCSharp.Blake2S.Create();
UTF8Encoding utf8 = new UTF8Encoding();
// use cache file instead of a memory stream to conserve used memory MemoryStream ms = new MemoryStream(); // processed chunks go here
string tempFile = null;
FileStream cacheFs = GetTempFileStream(out tempFile);
FileStream fs = new FileStream(SourceFile.FullName, FileMode.Open, FileAccess.Read);
long fileCursor = 0;
byte[] chunk = null;
UInt64 chunkCount = 0;
byte[] chunkNonce = new byte[24]; // always a constant length
// this part of the nonce doesn't change
Array.Copy(fileNonce, chunkNonce, fileNonce.Length); // copy it once and be done with it
do
{
if (chunkCount == 0) // first chunk is always '\0'-padded filename
{
chunk = new byte[256];
byte[] filename = utf8.GetBytes(SourceFile.Name);
Array.Copy(filename, chunk, filename.Length);
filename.Wipe(); // DON'T LEAK!!!
}
else
{
if (fileCursor + MAX_CHUNK_SIZE >= SourceFile.Length)
{
// last chunk
chunkNonce[23] |= 0x80;
chunk = new byte[SourceFile.Length - fileCursor];
}
else
{
chunk = new byte[MAX_CHUNK_SIZE];
}
if (fs.Read(chunk, 0, chunk.Length) != chunk.Length)
{
// read error!
fs.Close();
fs.Dispose();
TrashTempFileStream(cacheFs, tempFile);
throw new System.IO.IOException("Abrupt end of file / read error from source.");
}
fileCursor += chunk.Length;
}
byte[] outBuffer = XSalsa20Poly1305.Encrypt(chunk, fileKey, chunkNonce);
byte[] chunkLengthBytes = Utilities.UInt32ToBytes((uint)chunk.Length);
cacheFs.Write(chunkLengthBytes, 0, 4); // use cache file
b2s.Update(chunkLengthBytes); // hash as we go
cacheFs.Write(outBuffer, 0, outBuffer.Length); // use cache file
b2s.Update(outBuffer); // hash as we go
// since the first chunkNonce is just the fileNonce and a bunch of 0x00's,
// it's safe to do the chunk counter as a post-process update
Utilities.UInt64ToBytes(++chunkCount, chunkNonce, 16);
} while (fileCursor < SourceFile.Length);
cacheFs.Flush(true); // make sure everything is flushed to the disk cache
cacheFs.Position = 0; // leave it open so that we can read it back into the destination
// get the ciphertext hash for the header
byte[] cipherTextHash = b2s.Finish();
// done encrypting to the cache, now to build the header
//build header (fileInfo needed first, but same for all recipients)...
FileInfo fi = new FileInfo(
fileKey.ToBase64String(),
fileNonce.ToBase64String(),
cipherTextHash.ToBase64String());
byte[] fiBytes = utf8.GetBytes(fi.ToJSON()); // encrypt this to the recipients next...
//build inner headers next (one for each recipient)
Dictionary <string, string> innerHeaders = new Dictionary <string, string>(Recipients.Length);
foreach (string recip in Recipients)
{
// each recipient is not identified in the outer header, only a random NONCE
byte[] recipientNonce = Utilities.GenerateRandomBytes(24);
sharedKey = // INNER SHARED KEY (Sender Secret + Recipient Public)
SenderKeys.GetShared(recip);
InnerHeaderInfo ih = new InnerHeaderInfo(
SenderKeys.PublicID,
recip,
XSalsa20Poly1305.Encrypt(fiBytes, sharedKey, recipientNonce).ToBase64String()); // fileInfo JSON object encrypted, Base64
sharedKey = // OUTER SHARED KEY (Ephemeral Secret + Recipient Public)
ephemeral.GetShared(recip);
string encryptedInnerHeader = ih.ToJSON();
encryptedInnerHeader = XSalsa20Poly1305.Encrypt(utf8.GetBytes(encryptedInnerHeader), sharedKey, recipientNonce).ToBase64String();
innerHeaders.Add(recipientNonce.ToBase64String(), encryptedInnerHeader);
}
// finally the outer header, ready for stuffing into the file
HeaderInfo hi = new HeaderInfo(1, ephemeral.PublicKey.ToBase64String(), innerHeaders);
string fileHeader = hi.ToJSON();
// build the final file...
DestinationFile.Write(utf8.GetBytes("miniLock"), 0, 8); // file identifier (aka "magic bytes")
DestinationFile.Write(Utilities.UInt32ToBytes((uint)fileHeader.Length), 0, 4); // header length in 4 little endian bytes
DestinationFile.Write(utf8.GetBytes(fileHeader), 0, fileHeader.Length); // the full JSON header object
// read back from the cache file into the destination file...
byte[] buffer;
for (int i = 0; i < cacheFs.Length; i += buffer.Length)
{
if (i + MAX_CHUNK_SIZE >= cacheFs.Length)
{
buffer = new byte[cacheFs.Length - i];
}
else
{
buffer = new byte[MAX_CHUNK_SIZE];
}
if (cacheFs.Read(buffer, 0, buffer.Length) != buffer.Length)
{
throw new System.IO.IOException("Abrupt end of cache file");
}
DestinationFile.Write(buffer, 0, buffer.Length); // the ciphertext
}
// now flush and close, and grab length for reporting to caller
DestinationFile.Flush();
long tempOutputFileLength = DestinationFile.Length;
DestinationFile.Close();
DestinationFile.Dispose();
// kill the cache and the directory created for it
TrashTempFileStream(cacheFs, tempFile);
return(tempOutputFileLength);
}
/// <summary>
/// Decrypt a miniLock file using the specified Keys
/// </summary>
/// <param name="TheFile"></param>
/// <param name="RecipientKeys"></param>
/// <returns>null on any error, or a DecryptedFile object with the raw file contents, a plaintext hash,
/// the SenderID, and the stored filename</returns>
public static DecryptedFileDetails DecryptFile(FileStream SourceFile, string DestinationFileFullPath, bool OverWriteDestination, miniLockManaged.Keys RecipientKeys)
{
if (SourceFile == null)
{
throw new ArgumentNullException("SourceFile");
}
if (DestinationFileFullPath == null)
{
throw new ArgumentNullException("DestinationFile");
}
if (!SourceFile.CanRead)
{
throw new InvalidOperationException("Source File not readable!");
}
if (System.IO.File.Exists(DestinationFileFullPath) && !OverWriteDestination)
{
// be fault tolerant
System.IO.FileInfo existing = new System.IO.FileInfo(DestinationFileFullPath);
string newFilename = DestinationFileFullPath;
int counter = 1;
do
{
newFilename = DestinationFileFullPath.Replace(existing.Extension, "");
newFilename += '(' + counter++.ToString() + ')' + existing.Extension;
} while (File.Exists(newFilename));
DestinationFileFullPath = newFilename;
// this is not fault tolerant
//throw new InvalidOperationException("Destination File already exists! Set OverWriteDestination true or choose a different filename.");
}
FullHeader fileStuff = new FullHeader();
HeaderInfo h;
byte[] buffer = null;
// after this call, the source file pointer should be positioned to the end of the header
int hLen = IngestHeader(ref SourceFile, out h);
if (hLen < 0)
{
SourceFile.Close();
SourceFile.Dispose();
return(null);
}
hLen += 12; // the 8 magic bytes and the 4 header length bytes and the length of the JSON header object
long theCliff = SourceFile.Length - hLen; // this is the ADJUSTED point where the file cursor falls off the cliff
if (!TryDecryptHeader(h, RecipientKeys, out fileStuff)) // ciphertext hash is compared later
{
fileStuff.Clear();
SourceFile.Close();
SourceFile.Dispose();
return(null);
}
Blake2sCSharp.Hasher b2sPlain = Blake2sCSharp.Blake2S.Create(); // a nice-to-have for the user
Blake2sCSharp.Hasher b2sCipher = Blake2sCSharp.Blake2S.Create(); // a check to make sure the ciphertext wasn't altered
//note: in theory, if the ciphertext doesn't decrypt at any point, there is likely something wrong with it up to and
// including truncation/extension
// BUT the hash is included in the header, and should be checked.
DecryptedFileDetails results = new DecryptedFileDetails();
results.ActualDecryptedFilePath = DestinationFileFullPath; // if the filename got changed, it happened before this point
string tempFile = null; // save the filename of the temp file so that the temp directory created with it is also killed
System.IO.FileStream tempFS = GetTempFileStream(out tempFile);
int cursor = 0;
UInt64 chunkNumber = 0;
byte[] chunkNonce = new byte[24]; // always a constant length
Array.Copy(fileStuff.fileNonce, chunkNonce, fileStuff.fileNonce.Length); // copy it once and be done with it
do
{
// how big is this chunk? (32bit number, little endien)
buffer = new byte[4];
if (SourceFile.Read(buffer, 0, buffer.Length) != buffer.Length)
{
//read error
fileStuff.Clear();
SourceFile.Close();
SourceFile.Dispose();
TrashTempFileStream(tempFS, tempFile);
return(null);
}
b2sCipher.Update(buffer); // have to include ALL the bytes, even the chunk-length bytes
UInt32 chunkLength = Utilities.BytesToUInt32(buffer);
if (chunkLength > MAX_CHUNK_SIZE)
{
//something went wrong!
fileStuff.Clear();
SourceFile.Close();
SourceFile.Dispose();
TrashTempFileStream(tempFS, tempFile);
return(null);
}
cursor += 4; // move past the chunk length
//the XSalsa20Poly1305 process, ALWAYS expands the plaintext by MacSizeInBytes
// (authentication), so read the plaintext chunk length, add those bytes to the
// value, then read that many bytes out of the ciphertext buffer
byte[] chunk = new byte[chunkLength + XSalsa20Poly1305.MacSizeInBytes];
//Array.Copy(buffer, cursor,
// chunk, 0,
// chunk.Length);
if (SourceFile.Read(chunk, 0, chunk.Length) != chunk.Length)
{
//read error
fileStuff.Clear();
SourceFile.Close();
SourceFile.Dispose();
TrashTempFileStream(tempFS, tempFile);
return(null);
}
b2sCipher.Update(chunk); // get hash of cipher text to compare to stored File Info Object
cursor += chunk.Length; // move the cursor past this chunk
if (cursor >= theCliff) // this is the last chunk
{
// set most significant bit of nonce
chunkNonce[23] |= 0x80;
}
byte[] decryptBytes = XSalsa20Poly1305.TryDecrypt(chunk, fileStuff.fileKey, chunkNonce);
if (decryptBytes == null)
{
// nonce or key incorrect, or chunk has been altered (truncated?)
buffer = null;
fileStuff.Clear();
SourceFile.Close();
SourceFile.Dispose();
TrashTempFileStream(tempFS, tempFile);
return(null);
}
if (chunkNumber == 0) // first chunk is always filename '\0' padded
{
results.StoredFilename = new UTF8Encoding().GetString(decryptBytes).Replace("\0", "").Trim();
}
else
{
b2sPlain.Update(decryptBytes); // give the user a nice PlainText hash
tempFS.Write(decryptBytes, 0, decryptBytes.Length); // start building the output file
}
decryptBytes.Wipe(); // DON'T LEAK!!!
// since the first chunkNonce is just the fileNonce and a bunch of 0x00's,
// it's safe to do the chunk number update as a post-process operation
Utilities.UInt64ToBytes(++chunkNumber, chunkNonce, 16);
} while (cursor < theCliff);
SourceFile.Close();
SourceFile.Dispose();
byte[] ctActualHash = b2sCipher.Finish();
if (!CryptoBytes.ConstantTimeEquals(ctActualHash, fileStuff.ciphertextHash))
{
// ciphertext was altered
TrashTempFileStream(tempFS, tempFile);
return(null);
}
results.SenderID = Keys.GetPublicIDFromKeyBytes(fileStuff.senderID);
fileStuff.Clear(); // wipe the sensitive stuff!
tempFS.Flush();
tempFS.Close();
tempFS.Dispose();
//produce a handy hash for use by the end-user (not part of the spec)
results.PlainTextBlake2sHash = b2sPlain.Finish().ToBase64String();
System.IO.File.Move(tempFile, DestinationFileFullPath);
// WARNING: only use if the method that created the temp file also created a random subdir!
Directory.Delete(new System.IO.FileInfo(tempFile).DirectoryName, true); // this is done since we didn't use TrashTempfileStream
return(results);
}
