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Avoid ByteBuffer#asReadOnlyBuffer() #29

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merged 2 commits into from
Feb 7, 2022
Merged

Avoid ByteBuffer#asReadOnlyBuffer() #29

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5bdd487
Avoid ByteBuffer#asReadOnlyBuffer(), because hasArray() will return f…
overheadhunter Jan 25, 2022
10544a6
variable no longer used
overheadhunter Jan 26, 2022
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33 changes: 12 additions & 21 deletions src/main/java/org/cryptomator/cryptolib/v1/FileContentCryptorImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -115,9 +115,9 @@ void encryptChunk(ByteBuffer cleartextChunk, ByteBuffer ciphertextChunk, long ch
int bytesEncrypted = cipher.doFinal(cleartextChunk, ciphertextChunk);

// mac:
final ByteBuffer ciphertextBuf = ciphertextChunk.asReadOnlyBuffer();
ciphertextBuf.position(NONCE_SIZE).limit(NONCE_SIZE + bytesEncrypted);
byte[] authenticationCode = calcChunkMac(headerNonce, chunkNumber, nonce, ciphertextBuf);
ByteBuffer nonceAndPayload = ciphertextChunk.duplicate();
nonceAndPayload.flip();
byte[] authenticationCode = calcChunkMac(headerNonce, chunkNumber, nonceAndPayload);
assert authenticationCode.length == MAC_SIZE;
ciphertextChunk.put(authenticationCode);
} catch (ShortBufferException e) {
Expand All @@ -134,12 +134,10 @@ void decryptChunk(ByteBuffer ciphertextChunk, ByteBuffer cleartextChunk, Destroy
try (DestroyableSecretKey fk = fileKey.copy()) {
// nonce:
final byte[] nonce = new byte[NONCE_SIZE];
final ByteBuffer chunkNonceBuf = ciphertextChunk.asReadOnlyBuffer();
chunkNonceBuf.position(0).limit(NONCE_SIZE);
chunkNonceBuf.get(nonce);
ciphertextChunk.get(nonce, 0, NONCE_SIZE);

// payload:
final ByteBuffer payloadBuf = ciphertextChunk.asReadOnlyBuffer();
final ByteBuffer payloadBuf = ciphertextChunk.duplicate();
payloadBuf.position(NONCE_SIZE).limit(ciphertextChunk.limit() - MAC_SIZE);

// payload:
Expand All @@ -157,37 +155,30 @@ void decryptChunk(ByteBuffer ciphertextChunk, ByteBuffer cleartextChunk, Destroy
boolean checkChunkMac(byte[] headerNonce, long chunkNumber, ByteBuffer chunkBuf) {
assert chunkBuf.remaining() >= NONCE_SIZE + MAC_SIZE;

// get three components: nonce + payload + mac
final ByteBuffer chunkNonceBuf = chunkBuf.asReadOnlyBuffer();
chunkNonceBuf.position(0).limit(NONCE_SIZE);
final ByteBuffer payloadBuf = chunkBuf.asReadOnlyBuffer();
payloadBuf.position(NONCE_SIZE).limit(chunkBuf.limit() - MAC_SIZE);
final ByteBuffer expectedMacBuf = chunkBuf.asReadOnlyBuffer();
// get nonce + payload
final ByteBuffer nonceAndPayload = chunkBuf.duplicate();
nonceAndPayload.position(0).limit(chunkBuf.limit() - MAC_SIZE);
final ByteBuffer expectedMacBuf = chunkBuf.duplicate();
expectedMacBuf.position(chunkBuf.limit() - MAC_SIZE);

// get nonce:
final byte[] chunkNonce = new byte[NONCE_SIZE];
chunkNonceBuf.get(chunkNonce);

// get expected MAC:
final byte[] expectedMac = new byte[MAC_SIZE];
expectedMacBuf.get(expectedMac);

// get actual MAC:
final byte[] calculatedMac = calcChunkMac(headerNonce, chunkNumber, chunkNonce, payloadBuf);
final byte[] calculatedMac = calcChunkMac(headerNonce, chunkNumber, nonceAndPayload);

// time-constant equality check of two MACs:
return MessageDigest.isEqual(expectedMac, calculatedMac);
}

private byte[] calcChunkMac(byte[] headerNonce, long chunkNumber, byte[] chunkNonce, ByteBuffer ciphertext) {
private byte[] calcChunkMac(byte[] headerNonce, long chunkNumber, ByteBuffer nonceAndCiphertext) {
try (DestroyableSecretKey mk = masterkey.getMacKey()) {
final byte[] chunkNumberBigEndian = ByteBuffer.allocate(Long.SIZE / Byte.SIZE).order(ByteOrder.BIG_ENDIAN).putLong(chunkNumber).array();
final Mac mac = MacSupplier.HMAC_SHA256.withKey(mk);
mac.update(headerNonce);
mac.update(chunkNumberBigEndian);
mac.update(chunkNonce);
mac.update(ciphertext);
mac.update(nonceAndCiphertext);
return mac.doFinal();
}
}
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2 changes: 1 addition & 1 deletion src/main/java/org/cryptomator/cryptolib/v1/FileHeaderCryptorImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -88,7 +88,7 @@ public FileHeader decryptHeader(ByteBuffer ciphertextHeaderBuf) throws Authentic
if (ciphertextHeaderBuf.remaining() < FileHeaderImpl.SIZE) {
throw new IllegalArgumentException("Malformed ciphertext header");
}
ByteBuffer buf = ciphertextHeaderBuf.asReadOnlyBuffer();
ByteBuffer buf = ciphertextHeaderBuf.duplicate();
byte[] nonce = new byte[FileHeaderImpl.NONCE_LEN];
buf.position(FileHeaderImpl.NONCE_POS);
buf.get(nonce);
Expand Down
6 changes: 2 additions & 4 deletions src/main/java/org/cryptomator/cryptolib/v2/FileContentCryptorImpl.java
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Expand Up @@ -124,12 +124,10 @@ void decryptChunk(ByteBuffer ciphertextChunk, ByteBuffer cleartextChunk, long ch
try (DestroyableSecretKey fk = fileKey.copy()) {
// nonce:
final byte[] nonce = new byte[GCM_NONCE_SIZE];
final ByteBuffer chunkNonceBuf = ciphertextChunk.asReadOnlyBuffer();
chunkNonceBuf.position(0).limit(GCM_NONCE_SIZE);
chunkNonceBuf.get(nonce);
ciphertextChunk.get(nonce, 0, GCM_NONCE_SIZE);

// payload:
final ByteBuffer payloadBuf = ciphertextChunk.asReadOnlyBuffer();
final ByteBuffer payloadBuf = ciphertextChunk.duplicate();
payloadBuf.position(GCM_NONCE_SIZE);
assert payloadBuf.remaining() >= GCM_TAG_SIZE;

Expand Down
2 changes: 1 addition & 1 deletion src/main/java/org/cryptomator/cryptolib/v2/FileHeaderCryptorImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,7 @@ public FileHeader decryptHeader(ByteBuffer ciphertextHeaderBuf) throws Authentic
if (ciphertextHeaderBuf.remaining() < FileHeaderImpl.SIZE) {
throw new IllegalArgumentException("Malformed ciphertext header");
}
ByteBuffer buf = ciphertextHeaderBuf.asReadOnlyBuffer();
ByteBuffer buf = ciphertextHeaderBuf.duplicate();
byte[] nonce = new byte[FileHeaderImpl.NONCE_LEN];
buf.position(FileHeaderImpl.NONCE_POS);
buf.get(nonce);
Expand Down