public static void DecryptStream(Stream fin, Stream fout, string password, WrapProgressCallBack callback)
{
int size = (int)fin.Length; // the size of the file for progress notification
byte[] bytes = new byte[BUFFER_SIZE]; // byte buffer
int read = -1; // the amount of bytes read from the stream
int value = 0;
int outValue = 0; // the amount of bytes written out
// read off the IV and Salt
byte[] IV = new byte[16];
fin.Read(IV, 0, 16);
byte[] salt = new byte[16];
fin.Read(salt, 0, 16);
// create the crypting stream
SymmetricAlgorithm sma = FileWrapHelper.CreateRijndael(password, salt);
sma.IV = IV;
value = 32; // the value for the progress
long lSize = -1; // the size stored in the input stream
// create the hashing object, so that we can verify the file
HashAlgorithm hasher = SHA256.Create();
// create the cryptostreams that will process the file
using (CryptoStream cin = new CryptoStream(fin, sma.CreateDecryptor(), CryptoStreamMode.Read),
chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))
{
// read size from file
BinaryReader br = new BinaryReader(cin);
lSize = br.ReadInt64();
ulong tag = br.ReadUInt64();
if (FC_TAG != tag)
{
throw new FileWrapException("File Corrupted!");
}
//determine number of reads to process on the file
long numReads = lSize / BUFFER_SIZE;
// determine what is left of the file, after numReads
long slack = (long)lSize % BUFFER_SIZE;
// read the buffer_sized chunks
for (int i = 0; i < numReads; ++i)
{
read = cin.Read(bytes, 0, bytes.Length);
fout.Write(bytes, 0, read);
chash.Write(bytes, 0, read);
value += read;
outValue += read;
if (callback != null)
{
callback(0, size, value);
}
}
// now read the slack
if (slack > 0)
{
read = cin.Read(bytes, 0, (int)slack);
fout.Write(bytes, 0, read);
chash.Write(bytes, 0, read);
value += read;
outValue += read;
if (callback != null)
{
callback(0, size, value);
}
}
// flush and close the hashing stream
chash.Flush();
chash.Close();
// flush and close the output file
fout.Flush();
fout.Close();
// read the current hash value
byte[] curHash = hasher.Hash;
// get and compare the current and old hash values
byte[] oldHash = new byte[hasher.HashSize / 8];
read = cin.Read(oldHash, 0, oldHash.Length);
if ((oldHash.Length != read) || (!CheckByteArrays(oldHash, curHash)))
{
throw new FileWrapException("File Corrupted!");
}
}
// make sure the written and stored size are equal
if (outValue != lSize)
{
throw new FileWrapException("File Sizes don't match!");
}
}
/// <summary>
/// takes an input file and decrypts it to the output file
/// </summary>
/// <param name="inFile">the file to decrypt</param>
/// <param name="outFile">the to write the decrypted data to</param>
/// <param name="password">the password used as the key</param>
/// <param name="callback">the method to call to notify of progress</param>
public static void DecryptFile(string inFile, string outFile, string password, WrapProgressCallBack callback)
{
using (FileStream fin = File.OpenRead(inFile), fout = File.OpenWrite(outFile))
{
DecryptStream(fin, fout, password, callback);
}
}
public static void EncryptStream(Stream fin, Stream fout, string password, WrapProgressCallBack callback)
{
long lSize = fin.Length; // the size of the input file for storing
int size = (int)lSize; // the size of the input file for progress
byte[] bytes = new byte[BUFFER_SIZE]; // the buffer
int read = -1; // the amount of bytes read from the input file
int value = 0; // the amount overall read from the input file for progress
// generate IV and Salt
byte[] IV = GenerateRandomBytes(16);
byte[] salt = GenerateRandomBytes(16);
// create the crypting object
SymmetricAlgorithm sma = FileWrapHelper.CreateRijndael(password, salt);
sma.IV = IV;
// write the IV and salt to the beginning of the file
fout.Write(IV, 0, IV.Length);
fout.Write(salt, 0, salt.Length);
// create the hashing and crypto streams
HashAlgorithm hasher = SHA256.Create();
using (CryptoStream cout = new CryptoStream(fout, sma.CreateEncryptor(), CryptoStreamMode.Write),
chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))
{
// write the size of the file to the output file
BinaryWriter bw = new BinaryWriter(cout);
bw.Write(lSize);
// write the file cryptor tag to the file
bw.Write(FC_TAG);
// read and the write the bytes to the crypto stream in BUFFER_SIZEd chunks
while ((read = fin.Read(bytes, 0, bytes.Length)) != 0)
{
cout.Write(bytes, 0, read);
chash.Write(bytes, 0, read);
value += read;
if (callback != null)
{
callback(0, size, value);
}
}
// flush and close the hashing object
chash.Flush();
chash.Close();
// read the hash
byte[] hash = hasher.Hash;
// write the hash to the end of the file
cout.Write(hash, 0, hash.Length);
// flush and close the cryptostream
cout.Flush();
cout.Close();
cout.Dispose();
}
}