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Code Releases Wiki Activity

Redmi Smart Band Pro: Ignore MAC during decryption

Browse Source 
https://codeberg.org/Freeyourgadget/Gadgetbridge/issues/3766#issuecomment-2182676
This commit is contained in:
José Rebelo 2024-08-20 10:00:04 +01:00
parent 2fe53ee563
commit d3957ddf9a
3 changed files with 29 additions and 8 deletions
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4
app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/xiaomi/XiaomiCoordinator.java
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@ -577,4 +577,8 @@ public abstract class XiaomiCoordinator extends AbstractBLEDeviceCoordinator {
public boolean supports(final GBDevice device, final String feature) {
return getPrefs(device).getBoolean(feature, false);
}
public boolean checkDecryptionMac() {
return true;
}
}

6
app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/xiaomi/redmismartbandpro/RedmiSmartBandProCoordinator.java
View File

@ -66,4 +66,10 @@ public class RedmiSmartBandProCoordinator extends XiaomiCoordinator {
public PasswordCapabilityImpl.Mode getPasswordCapability() {
return PasswordCapabilityImpl.Mode.NUMBERS_4_DIGITS_0_TO_9;
}
@Override
public boolean checkDecryptionMac() {
// https://codeberg.org/Freeyourgadget/Gadgetbridge/issues/3766
return false;
}
}

27
app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiAuthService.java
View File

@ -16,6 +16,7 @@
along with this program. If not, see <https://www.gnu.org/licenses/>. */
package nodomain.freeyourgadget.gadgetbridge.service.devices.xiaomi;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Build;
import android.widget.Toast;
@ -46,7 +47,6 @@ import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import nodomain.freeyourgadget.gadgetbridge.BuildConfig;
import nodomain.freeyourgadget.gadgetbridge.GBApplication;
import nodomain.freeyourgadget.gadgetbridge.R;
import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice;
@ -65,6 +65,7 @@ public class XiaomiAuthService extends AbstractXiaomiService {
public static final int CMD_AUTH = 27;
private boolean encryptionInitialized = false;
private boolean checkDecryptionMac = true;
private final byte[] secretKey = new byte[16];
private final byte[] nonce = new byte[16];
@ -104,6 +105,12 @@ public class XiaomiAuthService extends AbstractXiaomiService {
getSupport().sendCommand("auth step 1", command);
}
@Override
public void setContext(final Context context) {
super.setContext(context);
this.checkDecryptionMac = getCoordinator().checkDecryptionMac();
}
@Override
public void handleCommand(final XiaomiProto.Command cmd) {
if (cmd.getType() != COMMAND_TYPE) {
@ -180,7 +187,7 @@ public class XiaomiAuthService extends AbstractXiaomiService {
packetNonce.putInt(0);
try {
return decrypt(decryptionKey, packetNonce.array(), arr);
return decrypt(decryptionKey, packetNonce.array(), arr, checkDecryptionMac);
} catch (final CryptoException e) {
throw new RuntimeException("failed to decrypt", e);
}
@ -323,7 +330,7 @@ public class XiaomiAuthService extends AbstractXiaomiService {
public static byte[] encrypt(final byte[] key, final byte[] nonce, final byte[] payload) throws
CryptoException {
final CCMBlockCipher cipher = createBlockCipher(true, new SecretKeySpec(key, "AES"), nonce);
final CCMBlockCipher cipher = createBlockCipher(true, new SecretKeySpec(key, "AES"), 32, nonce);
final byte[] out = new byte[cipher.getOutputSize(payload.length)];
final int outBytes = cipher.processBytes(payload, 0, payload.length, out, 0);
cipher.doFinal(out, outBytes);
@ -332,20 +339,24 @@ public class XiaomiAuthService extends AbstractXiaomiService {
public static byte[] decrypt(final byte[] key,
final byte[] nonce,
final byte[] encryptedPayload) throws CryptoException {
final CCMBlockCipher cipher = createBlockCipher(false, new SecretKeySpec(key, "AES"), nonce);
final byte[] decrypted = new byte[cipher.getOutputSize(encryptedPayload.length)];
cipher.doFinal(decrypted, cipher.processBytes(encryptedPayload, 0, encryptedPayload.length, decrypted, 0));
final byte[] encryptedPayload,
final boolean checkMac) throws CryptoException {
final int macSizeBits = checkMac ? 32 : 0;
final int actualEncryptedLength = checkMac ? encryptedPayload.length : encryptedPayload.length - 4;
final CCMBlockCipher cipher = createBlockCipher(false, new SecretKeySpec(key, "AES"), macSizeBits, nonce);
final byte[] decrypted = new byte[cipher.getOutputSize(actualEncryptedLength)];
cipher.doFinal(decrypted, cipher.processBytes(encryptedPayload, 0, actualEncryptedLength, decrypted, 0));
return decrypted;
}
public static CCMBlockCipher createBlockCipher(final boolean forEncrypt,
final SecretKey secretKey,
final int macSizeBits,
final byte[] nonce) {
final AESEngine aesFastEngine = new AESEngine();
aesFastEngine.init(forEncrypt, new KeyParameter(secretKey.getEncoded()));
final CCMBlockCipher blockCipher = new CCMBlockCipher(aesFastEngine);
blockCipher.init(forEncrypt, new AEADParameters(new KeyParameter(secretKey.getEncoded()), 32, nonce, null));
blockCipher.init(forEncrypt, new AEADParameters(new KeyParameter(secretKey.getEncoded()), macSizeBits, nonce, null));
return blockCipher;
}
}