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cleanup

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This commit is contained in:
Sebastian Stenzel 2015-05-04 22:02:47 +02:00
parent 040f260bf0
commit 4d08e9d72b
2 changed files with 21 additions and 48 deletions
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61
main/crypto-aes/src/main/java/org/cryptomator/crypto/aes256/Aes256Cryptor.java
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@ -389,27 +389,6 @@ public class Aes256Cryptor implements Cryptor, AesCryptographicConfiguration, Fi
return fileSize;
}
// private void encryptedContentLength(SeekableByteChannel encryptedFile, Long contentLength) throws IOException {
// final ByteBuffer encryptedFileSizeBuffer;
//
// // encrypt content length in ECB mode (content length is less than one block):
// try {
// final ByteBuffer fileSizeBuffer = ByteBuffer.allocate(Long.BYTES);
// fileSizeBuffer.putLong(contentLength);
// final Cipher sizeCipher = aesEcbCipher(primaryMasterKey, Cipher.ENCRYPT_MODE);
// final byte[] encryptedFileSize = sizeCipher.doFinal(fileSizeBuffer.array());
// encryptedFileSizeBuffer = ByteBuffer.wrap(encryptedFileSize);
// } catch (IllegalBlockSizeException | BadPaddingException e) {
// throw new IllegalStateException("Block size must be valid, as padding is requested. BadPaddingException not possible in encrypt mode.", e);
// }
//
// // skip 128bit IV:
// encryptedFile.position(16l);
//
// // write result:
// encryptedFile.write(encryptedFileSizeBuffer);
// }
private long decryptContentLength(byte[] encryptedContentLengthBytes) {
try {
final Cipher sizeCipher = aesEcbCipher(primaryMasterKey, Cipher.DECRYPT_MODE);
@ -563,16 +542,18 @@ public class Aes256Cryptor implements Cryptor, AesCryptographicConfiguration, Fi
// truncate file
encryptedFile.truncate(0);
// 96 byte header buffer (16 IV, 16 size, 32 headerMac, 32 contentMac):
final ByteBuffer headerBuf = ByteBuffer.allocate(96);
encryptedFile.write(headerBuf);
// use an IV, whose last 8 bytes store a long used in counter mode and write initial value to file.
final ByteBuffer iv = ByteBuffer.wrap(randomData(AES_BLOCK_LENGTH));
iv.putInt(AES_BLOCK_LENGTH - Integer.BYTES, 0);
// encrypt and write "zero length" as a placeholder, which will be read by concurrent requests, as long as encryption didn't finish:
// encryptedContentLength(encryptedFile, 0l);
// 96 byte header buffer (16 IV, 16 size, 32 headerMac, 32 contentMac)
// prefilled with "zero" content length for impatient processes, which want to know the size, before file has been completely written:
final ByteBuffer headerBuf = ByteBuffer.allocate(96);
headerBuf.position(16);
headerBuf.put(encryptContentLength(0l));
headerBuf.flip();
headerBuf.limit(96);
encryptedFile.write(headerBuf);
// content encryption:
final Cipher cipher = this.aesCtrCipher(primaryMasterKey, iv.array(), Cipher.ENCRYPT_MODE);
@ -586,25 +567,19 @@ public class Aes256Cryptor implements Cryptor, AesCryptographicConfiguration, Fi
try {
plaintextSize = IOUtils.copyLarge(lengthLimitingIn, blockSizeBufferedOut);
} catch (CounterAwareInputLimitReachedException ex) {
encryptedFile.truncate(64l + CounterAwareInputStream.SIXTY_FOUR_GIGABYE);
// TODO
// encryptedContentLength(encryptedFile, CounterAwareInputStream.SIXTY_FOUR_GIGABYE);
// no additional padding needed here, as 64GiB is a multiple of 128bit
encryptedFile.truncate(0l);
throw new CounterOverflowException("File size exceeds limit (64Gib). Aborting to prevent counter overflow.");
}
// ensure total byte count is a multiple of the block size, in CTR mode:
// final int remainderToFillLastBlock = AES_BLOCK_LENGTH - (int) (plaintextSize % AES_BLOCK_LENGTH);
// blockSizeBufferedOut.write(new byte[remainderToFillLastBlock]);
// for filesizes of up to 16GiB: append a few blocks of fake data:
if (plaintextSize < (long) (Integer.MAX_VALUE / 4) * AES_BLOCK_LENGTH) {
final int numberOfPlaintextBlocks = (int) Math.ceil(plaintextSize / AES_BLOCK_LENGTH);
final int upToTenPercentFakeBlocks = (int) Math.ceil(Math.random() * 0.1 * numberOfPlaintextBlocks);
final byte[] emptyBytes = this.randomData(AES_BLOCK_LENGTH);
for (int i = 0; i < upToTenPercentFakeBlocks; i += AES_BLOCK_LENGTH) {
blockSizeBufferedOut.write(emptyBytes);
}
// add random length padding to obfuscate file length:
final long numberOfPlaintextBlocks = (int) Math.ceil(plaintextSize / AES_BLOCK_LENGTH);
final long minAdditionalBlocks = 4;
final long maxAdditionalBlocks = Math.min(numberOfPlaintextBlocks >> 3, 1024 * 1024); // 12,5% of original blocks, but not more than 1M blocks (16MiBs)
final long availableBlocks = (1l << 32) - numberOfPlaintextBlocks; // before reaching limit of 2^32 blocks
final long additionalBlocks = (long) Math.min(Math.random() * Math.max(minAdditionalBlocks, maxAdditionalBlocks), availableBlocks);
final byte[] randomPadding = this.randomData(AES_BLOCK_LENGTH);
for (int i = 0; i < additionalBlocks; i += AES_BLOCK_LENGTH) {
blockSizeBufferedOut.write(randomPadding);
}
blockSizeBufferedOut.flush();

8
main/crypto-aes/src/main/java/org/cryptomator/crypto/aes256/CounterAwareInputStream.java
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@ -5,20 +5,18 @@ import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.atomic.AtomicLong;
import javax.crypto.Mac;
/**
* Updates a {@link Mac} with the bytes read from this stream.
* Throws an exception, if more than (2^32)-1 16 byte blocks will be encrypted (would result in an counter overflow).<br/>
* From https://tools.ietf.org/html/rfc3686: <cite> Using the encryption process described in section 2.1, this construction permits each packet to consist of up to: (2^32)-1 blocks</cite>
*/
class CounterAwareInputStream extends FilterInputStream {
static final long SIXTY_FOUR_GIGABYE = 1024l * 1024l * 1024l * 64l;
static final long SIXTY_FOUR_GIGABYE = ((1l << 32) - 1) * 16;
private final AtomicLong counter;
/**
* @param in Stream from which to read contents, which will update the Mac.
* @param mac Mac to be updated during writes.
*/
public CounterAwareInputStream(InputStream in) {
super(in);