/*
* (non-Javadoc)
*
* @see java.io.FileInputStream#skip(long)
*/
@Override
public long skip(long n) throws IOException {
long bytesSkipped = 0;
int toSkip;
int bytesRead;
byte[] skipBuf = new byte[config.getBlockSize()];
if (n < 0) {
throw new IOException("Negative skip count");
}
while (bytesSkipped < n) {
toSkip = (int) Math.min(n - bytesSkipped, config.getBlockSize());
bytesRead = this.read(skipBuf, 0, toSkip);
bytesSkipped += bytesRead;
if (bytesRead == -1) {
return -1; // Already at EOF
} else if (bytesRead < toSkip) {
return bytesSkipped; // Hit EOF now
}
}
return bytesSkipped;
}
/**
* Create a new EncFSInputStream for reading decrypted data off a file on an EncFS volume
*
* @param volume Volume hosting the file to read
* @param in Input stream to access the raw (encrypted) file contents
* @param volumePath Volume path of the file being decrypted (needed for externalIVChaining)
* @throws EncFSCorruptDataException File data is corrupt
* @throws EncFSUnsupportedException Unsupported EncFS configuration
* @throws IOException File provider returned I/O error
*/
public EncFSInputStream(EncFSVolume volume, InputStream in, String volumePath)
throws EncFSCorruptDataException, EncFSUnsupportedException {
super(in);
this.volume = volume;
this.config = volume.getConfig();
this.blockSize = config.getBlockSize();
this.numMACBytes = config.getBlockMACBytes();
this.numRandBytes = config.getBlockMACRandBytes();
this.blockHeaderSize = this.numMACBytes + this.numRandBytes;
this.blockBuf = null;
this.bufCursor = 0;
this.blockNum = 0;
if (config.isUniqueIV()) {
// Compute file IV
byte[] fileHeader = new byte[EncFSFile.HEADER_SIZE];
try {
in.read(fileHeader);
} catch (IOException e) {
throw new EncFSCorruptDataException("Could't read file IV");
}
byte[] initIv;
if (config.isExternalIVChaining()) {
/*
* When using external IV chaining we compute initIv based on
* the file path.
*/
initIv = EncFSCrypto.computeChainIv(volume, volumePath);
} else {
// When not using external IV chaining initIv is just zero's.
initIv = new byte[8];
}
try {
this.fileIv = EncFSCrypto.streamDecode(volume, initIv, fileHeader);
} catch (InvalidAlgorithmParameterException e) {
e.printStackTrace();
} catch (IllegalBlockSizeException e) {
throw new EncFSCorruptDataException(e);
} catch (BadPaddingException e) {
throw new EncFSCorruptDataException(e);
}
} else {
// No unique IV per file, just use 0
this.fileIv = new byte[EncFSFile.HEADER_SIZE];
}
}
