1 files changed, 76 insertions, 32 deletions

diff --git a/service/java/com/android/server/wifi/WifiConfigManager.java b/service/java/com/android/server/wifi/WifiConfigManager.java
index 683ace4c8..d1734d445 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)
      */
@@ -272,6 +277,7 @@ public class WifiConfigManager {
     private final WifiPermissionsWrapper mWifiPermissionsWrapper;
     private final WifiInjector mWifiInjector;
     private boolean mConnectedMacRandomzationSupported;
+    private final Mac mMac;
 
     /**
      * Local log used for debugging any WifiConfigManager issues.
@@ -446,6 +452,11 @@ 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!");
+        }
     }
 
     /**
@@ -464,6 +475,59 @@ 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.
      */
@@ -520,8 +584,7 @@ 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);
     }
 
     /**
@@ -1050,34 +1113,11 @@ 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;
     }
 
     /**
@@ -3026,12 +3066,16 @@ 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);
+            }
         }
     }