diff options
4 files changed, 225 insertions, 33 deletions
diff --git a/service/java/com/android/server/wifi/WifiConfigManager.java b/service/java/com/android/server/wifi/WifiConfigManager.java index 0c175acd2..4ac4fb7a6 100644 --- a/service/java/com/android/server/wifi/WifiConfigManager.java +++ b/service/java/com/android/server/wifi/WifiConfigManager.java @@ -76,6 +76,8 @@ import java.util.List; import java.util.Map; import java.util.Set; +import javax.crypto.Mac; + /** * This class provides the APIs to manage configured Wi-Fi networks. * It deals with the following: @@ -228,6 +230,9 @@ public class WifiConfigManager { private static final int WIFI_PNO_FREQUENCY_CULLING_ENABLED_DEFAULT = 1; // 0 = disabled private static final int WIFI_PNO_RECENCY_SORTING_ENABLED_DEFAULT = 1; // 0 = disabled: + private static final MacAddress DEFAULT_MAC_ADDRESS = + MacAddress.fromString(WifiInfo.DEFAULT_MAC_ADDRESS); + /** * Expiration timeout for deleted ephemeral ssids. (1 day) */ @@ -263,6 +268,7 @@ public class WifiConfigManager { */ private final Context mContext; private final Clock mClock; + private final Mac mMac; private final UserManager mUserManager; private final BackupManagerProxy mBackupManagerProxy; private final TelephonyManager mTelephonyManager; @@ -443,6 +449,11 @@ public class WifiConfigManager { } catch (PackageManager.NameNotFoundException e) { Log.e(TAG, "Unable to resolve SystemUI's UID."); } + mMac = WifiConfigurationUtil.obtainMacRandHashFunction(Process.WIFI_UID); + if (mMac == null) { + Log.wtf(TAG, "Failed to obtain secret for MAC randomization." + + " All randomized MAC addresses are lost!"); + } } /** @@ -461,6 +472,59 @@ public class WifiConfigManager { return sb.toString(); } + @VisibleForTesting + protected int getRandomizedMacAddressMappingSize() { + return mRandomizedMacAddressMapping.size(); + } + + /** + * The persistent randomized MAC address is locally generated for each SSID and does not + * change until factory reset of the device. In the initial Q release the per-SSID randomized + * MAC is saved on the device, but in an update the storing of randomized MAC is removed. + * Instead, the randomized MAC is calculated directly from the SSID and a on device secret. + * For backward compatibility, this method first checks the device storage for saved + * randomized MAC. If it is not found or the saved MAC is invalid then it will calculate the + * randomized MAC directly. + * + * In the future as devices launched on Q no longer get supported, this method should get + * simplified to return the calculated MAC address directly. + * @param config the WifiConfiguration to obtain MAC address for. + * @return persistent MAC address for this WifiConfiguration + */ + private MacAddress getPersistentMacAddress(WifiConfiguration config) { + // mRandomizedMacAddressMapping had been the location to save randomized MAC addresses. + String persistentMacString = mRandomizedMacAddressMapping.get( + config.getSsidAndSecurityTypeString()); + // Use the MAC address stored in the storage if it exists and is valid. Otherwise + // use the MAC address calculated from a hash function as the persistent MAC. + if (persistentMacString != null) { + try { + return MacAddress.fromString(persistentMacString); + } catch (IllegalArgumentException e) { + Log.e(TAG, "Error creating randomized MAC address from stored value."); + mRandomizedMacAddressMapping.remove(config.getSsidAndSecurityTypeString()); + } + } + return WifiConfigurationUtil.calculatePersistentMacForConfiguration(config, mMac); + } + + /** + * Obtain the persistent MAC address by first reading from an internal database. If non exists + * then calculate the persistent MAC using HMAC-SHA256. + * Finally set the randomized MAC of the configuration to the randomized MAC obtained. + * @param config the WifiConfiguration to make the update + * @return the persistent MacAddress or null if the operation is unsuccessful + */ + private MacAddress setRandomizedMacToPersistentMac(WifiConfiguration config) { + MacAddress persistentMac = getPersistentMacAddress(config); + if (persistentMac == null || persistentMac.equals(config.getRandomizedMacAddress())) { + return persistentMac; + } + WifiConfiguration internalConfig = getInternalConfiguredNetwork(config.networkId); + internalConfig.setRandomizedMacAddress(persistentMac); + return persistentMac; + } + /** * Enable/disable verbose logging in WifiConfigManager & its helper classes. */ @@ -517,8 +581,7 @@ public class WifiConfigManager { * @param configuration WifiConfiguration to hide the MAC address */ private void maskRandomizedMacAddressInWifiConfiguration(WifiConfiguration configuration) { - MacAddress defaultMac = MacAddress.fromString(WifiInfo.DEFAULT_MAC_ADDRESS); - configuration.setRandomizedMacAddress(defaultMac); + configuration.setRandomizedMacAddress(DEFAULT_MAC_ADDRESS); } /** @@ -1044,34 +1107,11 @@ public class WifiConfigManager { packageName != null ? packageName : mContext.getPackageManager().getNameForUid(uid); newInternalConfig.creationTime = newInternalConfig.updateTime = createDebugTimeStampString(mClock.getWallClockMillis()); - updateRandomizedMacAddress(newInternalConfig); - - return newInternalConfig; - } - - /** - * Sets the randomized address for the given configuration from stored map if it exist. - * Otherwise generates a new randomized address and save to the stored map. - * @param config - */ - private void updateRandomizedMacAddress(WifiConfiguration config) { - // Update randomized MAC address according to stored map - final String key = config.getSsidAndSecurityTypeString(); - // If the key is not found in the current store, then it means this network has never been - // seen before. So add it to store. - if (!mRandomizedMacAddressMapping.containsKey(key)) { - mRandomizedMacAddressMapping.put(key, - config.getOrCreateRandomizedMacAddress().toString()); - } else { // Otherwise read from the store and set the WifiConfiguration - try { - config.setRandomizedMacAddress( - MacAddress.fromString(mRandomizedMacAddressMapping.get(key))); - } catch (IllegalArgumentException e) { - Log.e(TAG, "Error creating randomized MAC address from stored value."); - mRandomizedMacAddressMapping.put(key, - config.getOrCreateRandomizedMacAddress().toString()); - } + MacAddress randomizedMac = getPersistentMacAddress(newInternalConfig); + if (randomizedMac != null) { + newInternalConfig.setRandomizedMacAddress(randomizedMac); } + return newInternalConfig; } /** @@ -3027,12 +3067,16 @@ public class WifiConfigManager { } /** - * Generate randomized MAC addresses for configured networks and persist mapping to storage. + * Assign randomized MAC addresses for configured networks. + * This is needed to generate persistent randomized MAC address for existing networks when + * a device updates to Q+ for the first time since we are not calling addOrUpdateNetwork when + * we load configuration at boot. */ private void generateRandomizedMacAddresses() { for (WifiConfiguration config : getInternalConfiguredNetworks()) { - mRandomizedMacAddressMapping.put(config.getSsidAndSecurityTypeString(), - config.getOrCreateRandomizedMacAddress().toString()); + if (DEFAULT_MAC_ADDRESS.equals(config.getRandomizedMacAddress())) { + setRandomizedMacToPersistentMac(config); + } } } diff --git a/service/java/com/android/server/wifi/WifiConfigurationUtil.java b/service/java/com/android/server/wifi/WifiConfigurationUtil.java index a99253463..c59d4faf7 100644 --- a/service/java/com/android/server/wifi/WifiConfigurationUtil.java +++ b/service/java/com/android/server/wifi/WifiConfigurationUtil.java @@ -28,6 +28,9 @@ import android.net.wifi.WifiNetworkSpecifier; import android.net.wifi.WifiScanner; import android.os.PatternMatcher; import android.os.UserHandle; +import android.security.keystore.AndroidKeyStoreProvider; +import android.security.keystore.KeyGenParameterSpec; +import android.security.keystore.KeyProperties; import android.text.TextUtils; import android.util.Log; import android.util.Pair; @@ -36,7 +39,17 @@ import com.android.internal.annotations.VisibleForTesting; import com.android.server.wifi.util.NativeUtil; import com.android.server.wifi.util.TelephonyUtil; +import java.nio.ByteBuffer; import java.nio.charset.StandardCharsets; +import java.security.InvalidAlgorithmParameterException; +import java.security.InvalidKeyException; +import java.security.Key; +import java.security.KeyStore; +import java.security.KeyStoreException; +import java.security.NoSuchAlgorithmException; +import java.security.NoSuchProviderException; +import java.security.ProviderException; +import java.security.UnrecoverableKeyException; import java.security.cert.X509Certificate; import java.util.Arrays; import java.util.BitSet; @@ -44,6 +57,10 @@ import java.util.Comparator; import java.util.List; import java.util.Objects; +import javax.crypto.KeyGenerator; +import javax.crypto.Mac; +import javax.crypto.SecretKey; + /** * WifiConfiguration utility for any {@link android.net.wifi.WifiConfiguration} related operations. * Currently contains: @@ -72,6 +89,10 @@ public class WifiConfigurationUtil { new Pair(MacAddress.BROADCAST_ADDRESS, MacAddress.BROADCAST_ADDRESS); private static final Pair<MacAddress, MacAddress> MATCH_ALL_BSSID_PATTERN = new Pair(MacAddress.ALL_ZEROS_ADDRESS, MacAddress.ALL_ZEROS_ADDRESS); + private static final String MAC_RANDOMIZATION_ALIAS = "MacRandSecret"; + private static final long MAC_ADDRESS_VALID_LONG_MASK = (1L << 48) - 1; + private static final long MAC_ADDRESS_LOCALLY_ASSIGNED_MASK = 1L << 41; + private static final long MAC_ADDRESS_MULTICAST_MASK = 1L << 40; /** * Check whether a network configuration is visible to a user or any of its managed profiles. @@ -227,6 +248,87 @@ public class WifiConfigurationUtil { } /** + * Computes the persistent randomized MAC of the given configuration using the given + * hash function. + * @param config the WifiConfiguration to compute MAC address for + * @param hashFunction the hash function that will perform the MAC address computation. + * @return The persistent randomized MAC address or null if inputs are invalid. + */ + public static MacAddress calculatePersistentMacForConfiguration(WifiConfiguration config, + Mac hashFunction) { + if (config == null || hashFunction == null) { + return null; + } + byte[] hashedBytes = hashFunction.doFinal( + config.getSsidAndSecurityTypeString().getBytes(StandardCharsets.UTF_8)); + ByteBuffer bf = ByteBuffer.wrap(hashedBytes); + long longFromSsid = bf.getLong(); + /** + * Masks the generated long so that it represents a valid randomized MAC address. + * Specifically, this sets the locally assigned bit to 1, multicast bit to 0 + */ + longFromSsid &= MAC_ADDRESS_VALID_LONG_MASK; + longFromSsid |= MAC_ADDRESS_LOCALLY_ASSIGNED_MASK; + longFromSsid &= ~MAC_ADDRESS_MULTICAST_MASK; + bf.clear(); + bf.putLong(0, longFromSsid); + + // MacAddress.fromBytes requires input of length 6, which is obtained from the + // last 6 bytes from the generated long. + MacAddress macAddress = MacAddress.fromBytes(Arrays.copyOfRange(bf.array(), 2, 8)); + return macAddress; + } + + /** + * Retrieves a Hash function that could be used to calculate the persistent randomized MAC + * for a WifiConfiguration. + * @param uid the UID of the KeyStore to get the secret of the hash function from. + */ + public static Mac obtainMacRandHashFunction(int uid) { + try { + KeyStore keyStore = AndroidKeyStoreProvider.getKeyStoreForUid(uid); + // tries to retrieve the secret, and generate a new one if it's unavailable. + Key key = keyStore.getKey(MAC_RANDOMIZATION_ALIAS, null); + if (key == null) { + key = generateAndPersistNewMacRandomizationSecret(uid); + } + if (key == null) { + Log.e(TAG, "Failed to generate secret for " + MAC_RANDOMIZATION_ALIAS); + return null; + } + Mac result = Mac.getInstance("HmacSHA256"); + result.init(key); + return result; + } catch (KeyStoreException | NoSuchAlgorithmException | InvalidKeyException + | UnrecoverableKeyException | NoSuchProviderException e) { + Log.e(TAG, "Failure in obtainMacRandHashFunction", e); + return null; + } + } + + /** + * Generates and returns a secret key to use for Mac randomization. + * Will also persist the generated secret inside KeyStore, accessible in the + * future with KeyGenerator#getKey. + */ + private static SecretKey generateAndPersistNewMacRandomizationSecret(int uid) { + try { + KeyGenerator keyGenerator = KeyGenerator.getInstance( + KeyProperties.KEY_ALGORITHM_HMAC_SHA256, "AndroidKeyStore"); + keyGenerator.init( + new KeyGenParameterSpec.Builder(MAC_RANDOMIZATION_ALIAS, + KeyProperties.PURPOSE_SIGN) + .setUid(uid) + .build()); + return keyGenerator.generateKey(); + } catch (NoSuchAlgorithmException | InvalidAlgorithmParameterException + | NoSuchProviderException | ProviderException e) { + Log.e(TAG, "Failure in generateMacRandomizationSecret", e); + return null; + } + } + + /** * Compare existing and new WifiEnterpriseConfig objects after a network update and return if * credential parameters have changed or not. * diff --git a/tests/wifitests/src/com/android/server/wifi/WifiConfigManagerTest.java b/tests/wifitests/src/com/android/server/wifi/WifiConfigManagerTest.java index 9d5ed04c7..dad88f3c0 100644 --- a/tests/wifitests/src/com/android/server/wifi/WifiConfigManagerTest.java +++ b/tests/wifitests/src/com/android/server/wifi/WifiConfigManagerTest.java @@ -63,6 +63,7 @@ import org.mockito.InOrder; import org.mockito.Mock; import org.mockito.MockitoAnnotations; import org.mockito.MockitoSession; +import org.mockito.quality.Strictness; import java.io.FileDescriptor; import java.io.PrintWriter; @@ -111,6 +112,8 @@ public class WifiConfigManagerTest { private static final int TEST_FREQUENCY_1 = 2412; private static final int TEST_FREQUENCY_2 = 5180; private static final int TEST_FREQUENCY_3 = 5240; + private static final MacAddress TEST_RANDOMIZED_MAC = + MacAddress.fromString("d2:11:19:34:a5:20"); @Mock private Context mContext; @Mock private Clock mClock; @@ -227,10 +230,14 @@ public class WifiConfigManagerTest { // static mocking mSession = ExtendedMockito.mockitoSession() .mockStatic(WifiConfigStore.class, withSettings().lenient()) + .spyStatic(WifiConfigurationUtil.class) + .strictness(Strictness.LENIENT) .startMocking(); when(WifiConfigStore.createUserFiles(anyInt(), any(UserManager.class))) .thenReturn(mock(List.class)); when(mTelephonyManager.createForSubscriptionId(anyInt())).thenReturn(mDataTelephonyManager); + when(WifiConfigurationUtil.calculatePersistentMacForConfiguration(any(), any())) + .thenReturn(TEST_RANDOMIZED_MAC); } /** @@ -239,7 +246,9 @@ public class WifiConfigManagerTest { @After public void cleanup() { validateMockitoUsage(); - mSession.finishMocking(); + if (mSession != null) { + mSession.finishMocking(); + } } /** @@ -368,6 +377,7 @@ public class WifiConfigManagerTest { */ @Test public void testAddingNetworkWithMatchingMacAddressOverridesField() { + int prevMappingSize = mWifiConfigManager.getRandomizedMacAddressMappingSize(); WifiConfiguration openNetwork = WifiConfigurationTestUtil.createOpenNetwork(); Map<String, String> randomizedMacAddressMapping = new HashMap<>(); final String randMac = "12:23:34:45:56:67"; @@ -382,6 +392,9 @@ public class WifiConfigManagerTest { List<WifiConfiguration> retrievedNetworks = mWifiConfigManager.getConfiguredNetworksWithPasswords(); assertEquals(randMac, retrievedNetworks.get(0).getRandomizedMacAddress().toString()); + // Verify that for networks that we already have randomizedMacAddressMapping saved + // we are still correctly writing into the WifiConfigStore. + assertEquals(prevMappingSize + 1, mWifiConfigManager.getRandomizedMacAddressMappingSize()); } /** @@ -391,6 +404,7 @@ public class WifiConfigManagerTest { */ @Test public void testRandomizedMacAddressIsPersistedOverForgetNetwork() { + int prevMappingSize = mWifiConfigManager.getRandomizedMacAddressMappingSize(); // Create and add an open network WifiConfiguration openNetwork = WifiConfigurationTestUtil.createOpenNetwork(); verifyAddNetworkToWifiConfigManager(openNetwork); @@ -410,6 +424,8 @@ public class WifiConfigManagerTest { verifyAddNetworkToWifiConfigManager(openNetwork); retrievedNetworks = mWifiConfigManager.getConfiguredNetworksWithPasswords(); assertEquals(randMac, retrievedNetworks.get(0).getRandomizedMacAddress().toString()); + // Verify that we are no longer persisting the randomized MAC address with WifiConfigStore. + assertEquals(prevMappingSize, mWifiConfigManager.getRandomizedMacAddressMappingSize()); } /** diff --git a/tests/wifitests/src/com/android/server/wifi/WifiConfigurationUtilTest.java b/tests/wifitests/src/com/android/server/wifi/WifiConfigurationUtilTest.java index c1640ce91..7173dae5b 100644 --- a/tests/wifitests/src/com/android/server/wifi/WifiConfigurationUtilTest.java +++ b/tests/wifitests/src/com/android/server/wifi/WifiConfigurationUtilTest.java @@ -25,6 +25,7 @@ import android.net.wifi.WifiConfiguration; import android.net.wifi.WifiEnterpriseConfig; import android.net.wifi.WifiNetworkSpecifier; import android.net.wifi.WifiScanner; +import android.os.Binder; import android.os.PatternMatcher; import android.os.UserHandle; import android.util.Pair; @@ -39,6 +40,8 @@ import java.util.Arrays; import java.util.Collections; import java.util.List; +import javax.crypto.Mac; + /** * Unit tests for {@link com.android.server.wifi.WifiConfigurationUtil}. */ @@ -961,6 +964,33 @@ public class WifiConfigurationUtilTest { existingConfig, newConfig)); } + /** + * Verifies that calculatePersistentMacForConfiguration produces persistent, locally generated + * MAC addresses that are valid for MAC randomization. + */ + @Test + public void testCalculatePersistentMacForConfiguration() { + // verify null inputs + assertNull(WifiConfigurationUtil.calculatePersistentMacForConfiguration(null, null)); + + // test multiple times since there is some randomness involved with hashing + int uid = Binder.getCallingUid(); + for (int i = 0; i < 10; i++) { + // Verify that a the MAC address calculated is valid + WifiConfiguration config = WifiConfigurationTestUtil.createOpenNetwork(); + Mac hashFunction = WifiConfigurationUtil.obtainMacRandHashFunction(uid); + MacAddress macAddress = WifiConfigurationUtil.calculatePersistentMacForConfiguration( + config, hashFunction); + assertTrue(WifiConfiguration.isValidMacAddressForRandomization(macAddress)); + + // Verify that the secret used to generate MAC address is persistent + Mac hashFunction2 = WifiConfigurationUtil.obtainMacRandHashFunction(uid); + MacAddress macAddress2 = WifiConfigurationUtil.calculatePersistentMacForConfiguration( + config, hashFunction2); + assertEquals(macAddress, macAddress2); + } + } + private static class EnterpriseConfig { public String eap; public String phase2; |