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read file header instead of allBytes to determine Scheme

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This commit is contained in:
Jan-Peter Klein
2025-07-02 11:29:01 +02:00
parent 81307b6d75
commit 8a1ec1d073
1 changed files with 23 additions and 10 deletions
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33
src/main/java/org/cryptomator/common/recovery/MasterkeyService.java
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@@ -13,15 +13,16 @@ import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.Stream;
import static org.cryptomator.common.Constants.MASTERKEY_FILENAME;
@@ -81,16 +82,28 @@ public final class MasterkeyService {
}
private static Optional<CryptorProvider.Scheme> determineScheme(Path c9rFile, byte[] masterkey) {
try {
ByteBuffer header = ByteBuffer.wrap(Files.readAllBytes(c9rFile));
return Arrays.stream(CryptorProvider.Scheme.values())
.filter(s -> isDecryptable(header, new Masterkey(masterkey), s))
.findFirst();
} catch (IOException e) {
LOG.info("Unable to detect Crypto scheme: Failed to decrypt .c9r file", e);
return Optional.empty();
}
return Arrays.stream(CryptorProvider.Scheme.values()).filter(scheme -> {
try {
try (Masterkey mk = new Masterkey(masterkey); Cryptor cryptor = CryptorProvider.forScheme(scheme).provide(mk, SecureRandom.getInstanceStrong())) {
int headerSize = cryptor.fileHeaderCryptor().headerSize();
ByteBuffer headerBuf = ByteBuffer.allocate(headerSize);
try (FileChannel channel = FileChannel.open(c9rFile, StandardOpenOption.READ)) {
channel.read(headerBuf, 0);
}
headerBuf.flip();
return isDecryptable(headerBuf, mk, scheme);
}
} catch (IOException | CryptoException | NoSuchAlgorithmException e) {
LOG.info("Unable to detect Crypto scheme: Failed to decrypt .c9r file", e);
return false;
}
}).findFirst();
}
private static boolean isDecryptable(ByteBuffer header, Masterkey masterkey, CryptorProvider.Scheme scheme) {
try (Cryptor cryptor = CryptorProvider.forScheme(scheme).provide(masterkey, SecureRandom.getInstanceStrong())) {
cryptor.fileHeaderCryptor().decryptHeader(header.duplicate());