[CS] Add an option to block sensitive network specifier

Network specifiers are used for 2 purposes:

- As part of network requests to specify more information on the type
  of requested networks.
- On network agents to specify information about their networks.

The network specifiers of the requests and agents are matched to each
other. However, the agent network specifier may contain sensitive
information which we do not want forwarded to any app.

This CL adds an option to strip out this agent network specifier before
the network capabilities are forwarded to the app.

Bug: 161853197
Bug: 161370134
Test: atest ConnectivityServiceTest (frameworks/base/tests/net)
Test: atest frameworks/base/tests/net
Test: atest frameworks/opt/net/wifi/tests/wifitests
Test: atest frameworks/opt/telephony/tests/telephonytests
Test: atest frameworks/opt/net/ethernet/tests
Test: atest android.net.cts - some flakiness!
Test: act.py ThroughputTest
Test: act.py DataPathTest
Test: atest SingleDeviceTest (cts)
Change-Id: I38ed3ff88532ef522ab167c88d87e6e82295ffc5
Merged-In: If08d312ff814bdde1147518f923199e6349503d5
(cherry picked from commit 9b1d701af461899a03b046dbf97316abc1465ac3)
diff --git a/core/java/android/net/NetworkSpecifier.java b/core/java/android/net/NetworkSpecifier.java
index 9ce2a5b..12cdc34 100644
--- a/core/java/android/net/NetworkSpecifier.java
+++ b/core/java/android/net/NetworkSpecifier.java
@@ -17,7 +17,7 @@
 package android.net;
 
 /**
- * Describes specific properties of a network for use in a {@link NetworkRequest}.
+ * Describes specific properties of a requested network for use in a {@link NetworkRequest}.
  *
  * Applications cannot instantiate this class by themselves, but can obtain instances of
  * subclasses of this class via other APIs.
@@ -49,4 +49,29 @@
     public void assertValidFromUid(int requestorUid) {
         // empty
     }
+
+    /**
+     * Optional method which can be overridden by concrete implementations of NetworkSpecifier to
+     * perform any redaction of information from the NetworkSpecifier, e.g. if it contains
+     * sensitive information. The default implementation simply returns the object itself - i.e.
+     * no information is redacted. A concrete implementation may return a modified (copy) of the
+     * NetworkSpecifier, or even return a null to fully remove all information.
+     * <p>
+     * This method is relevant to NetworkSpecifier objects used by agents - those are shared with
+     * apps by default. Some agents may store sensitive matching information in the specifier,
+     * e.g. a Wi-Fi SSID (which should not be shared since it may leak location). Those classes
+     * can redact to a null. Other agents use the Network Specifier to share public information
+     * with apps - those should not be redacted.
+     * <p>
+     * The default implementation redacts no information.
+     *
+     * @return A NetworkSpecifier object to be passed along to the requesting app.
+     *
+     * @hide
+     */
+    public NetworkSpecifier redact() {
+        // TODO (b/122160111): convert default to null once all platform NetworkSpecifiers
+        // implement this method.
+        return this;
+    }
 }
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index bdb6d08..6eec3bc 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -1424,6 +1424,9 @@
             newNc.setUids(null);
             newNc.setSSID(null);
         }
+        if (newNc.getNetworkSpecifier() != null) {
+            newNc.setNetworkSpecifier(newNc.getNetworkSpecifier().redact());
+        }
         return newNc;
     }
 
@@ -5092,7 +5095,8 @@
         }
         switch (notificationType) {
             case ConnectivityManager.CALLBACK_AVAILABLE: {
-                putParcelable(bundle, new NetworkCapabilities(networkAgent.networkCapabilities));
+                putParcelable(bundle, networkCapabilitiesRestrictedForCallerPermissions(
+                        networkAgent.networkCapabilities, nri.mPid, nri.mUid));
                 putParcelable(bundle, new LinkProperties(networkAgent.linkProperties));
                 break;
             }
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index 4826120..34ced30 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -111,7 +111,6 @@
 import android.net.NetworkSpecifier;
 import android.net.NetworkUtils;
 import android.net.RouteInfo;
-import android.net.StringNetworkSpecifier;
 import android.net.UidRange;
 import android.net.VpnService;
 import android.net.captiveportal.CaptivePortalProbeResult;
@@ -133,6 +132,7 @@
 import android.support.test.filters.SmallTest;
 import android.support.test.runner.AndroidJUnit4;
 import android.test.mock.MockContentResolver;
+import android.text.TextUtils;
 import android.util.ArraySet;
 import android.util.Log;
 
@@ -2488,16 +2488,76 @@
         return new NetworkRequest.Builder().addTransportType(TRANSPORT_WIFI);
     }
 
+    /**
+     * Verify request matching behavior with network specifiers.
+     *
+     * Note: this test is somewhat problematic since it involves removing capabilities from
+     * agents - i.e. agents rejecting requests which they previously accepted. This is flagged
+     * as a WTF bug in
+     * {@link ConnectivityService#mixInCapabilities(NetworkAgentInfo, NetworkCapabilities)} but
+     * does work.
+     */
     @Test
     public void testNetworkSpecifier() {
+        // A NetworkSpecifier subclass that matches all networks but must not be visible to apps.
+        class ConfidentialMatchAllNetworkSpecifier extends NetworkSpecifier implements
+                Parcelable {
+            @Override
+            public boolean satisfiedBy(NetworkSpecifier other) {
+                return true;
+            }
+
+            @Override
+            public int describeContents() {
+                return 0;
+            }
+
+            @Override
+            public void writeToParcel(Parcel dest, int flags) {}
+
+            @Override
+            public NetworkSpecifier redact() {
+                return null;
+            }
+        }
+
+        // A network specifier that matches either another LocalNetworkSpecifier with the same
+        // string or a ConfidentialMatchAllNetworkSpecifier, and can be passed to apps as is.
+        class LocalStringNetworkSpecifier extends NetworkSpecifier implements Parcelable {
+            private String mString;
+
+            LocalStringNetworkSpecifier(String string) {
+                mString = string;
+            }
+
+            @Override
+            public boolean satisfiedBy(NetworkSpecifier other) {
+                if (other instanceof LocalStringNetworkSpecifier) {
+                    return TextUtils.equals(mString,
+                            ((LocalStringNetworkSpecifier) other).mString);
+                }
+                if (other instanceof ConfidentialMatchAllNetworkSpecifier) return true;
+                return false;
+            }
+
+            @Override
+            public int describeContents() {
+                return 0;
+            }
+            @Override
+            public void writeToParcel(Parcel dest, int flags) {}
+        }
+
+
         NetworkRequest rEmpty1 = newWifiRequestBuilder().build();
         NetworkRequest rEmpty2 = newWifiRequestBuilder().setNetworkSpecifier((String) null).build();
         NetworkRequest rEmpty3 = newWifiRequestBuilder().setNetworkSpecifier("").build();
         NetworkRequest rEmpty4 = newWifiRequestBuilder().setNetworkSpecifier(
             (NetworkSpecifier) null).build();
-        NetworkRequest rFoo = newWifiRequestBuilder().setNetworkSpecifier("foo").build();
+        NetworkRequest rFoo = newWifiRequestBuilder().setNetworkSpecifier(
+                new LocalStringNetworkSpecifier("foo")).build();
         NetworkRequest rBar = newWifiRequestBuilder().setNetworkSpecifier(
-                new StringNetworkSpecifier("bar")).build();
+                new LocalStringNetworkSpecifier("bar")).build();
 
         TestNetworkCallback cEmpty1 = new TestNetworkCallback();
         TestNetworkCallback cEmpty2 = new TestNetworkCallback();
@@ -2506,7 +2566,7 @@
         TestNetworkCallback cFoo = new TestNetworkCallback();
         TestNetworkCallback cBar = new TestNetworkCallback();
         TestNetworkCallback[] emptyCallbacks = new TestNetworkCallback[] {
-                cEmpty1, cEmpty2, cEmpty3 };
+                cEmpty1, cEmpty2, cEmpty3, cEmpty4 };
 
         mCm.registerNetworkCallback(rEmpty1, cEmpty1);
         mCm.registerNetworkCallback(rEmpty2, cEmpty2);
@@ -2515,6 +2575,9 @@
         mCm.registerNetworkCallback(rFoo, cFoo);
         mCm.registerNetworkCallback(rBar, cBar);
 
+        LocalStringNetworkSpecifier nsFoo = new LocalStringNetworkSpecifier("foo");
+        LocalStringNetworkSpecifier nsBar = new LocalStringNetworkSpecifier("bar");
+
         mWiFiNetworkAgent = new MockNetworkAgent(TRANSPORT_WIFI);
         mWiFiNetworkAgent.connect(false);
         cEmpty1.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
@@ -2523,30 +2586,54 @@
         cEmpty4.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
         assertNoCallbacks(cFoo, cBar);
 
-        mWiFiNetworkAgent.setNetworkSpecifier(new StringNetworkSpecifier("foo"));
+        mWiFiNetworkAgent.setNetworkSpecifier(nsFoo);
         cFoo.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
         for (TestNetworkCallback c: emptyCallbacks) {
-            c.expectCallback(CallbackState.NETWORK_CAPABILITIES, mWiFiNetworkAgent);
+            c.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier().equals(nsFoo),
+                    mWiFiNetworkAgent);
         }
-        cFoo.expectCallback(CallbackState.NETWORK_CAPABILITIES, mWiFiNetworkAgent);
+        cFoo.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier().equals(nsFoo),
+                mWiFiNetworkAgent);
+        assertEquals(nsFoo,
+                mCm.getNetworkCapabilities(mWiFiNetworkAgent.getNetwork()).getNetworkSpecifier());
         cFoo.assertNoCallback();
 
-        mWiFiNetworkAgent.setNetworkSpecifier(new StringNetworkSpecifier("bar"));
+        mWiFiNetworkAgent.setNetworkSpecifier(nsBar);
         cFoo.expectCallback(CallbackState.LOST, mWiFiNetworkAgent);
         cBar.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
         for (TestNetworkCallback c: emptyCallbacks) {
-            c.expectCallback(CallbackState.NETWORK_CAPABILITIES, mWiFiNetworkAgent);
+            c.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier().equals(nsBar),
+                    mWiFiNetworkAgent);
         }
-        cBar.expectCallback(CallbackState.NETWORK_CAPABILITIES, mWiFiNetworkAgent);
+        cBar.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier().equals(nsBar),
+                mWiFiNetworkAgent);
+        assertEquals(nsBar,
+                mCm.getNetworkCapabilities(mWiFiNetworkAgent.getNetwork()).getNetworkSpecifier());
+        cBar.assertNoCallback();
+
+        mWiFiNetworkAgent.setNetworkSpecifier(new ConfidentialMatchAllNetworkSpecifier());
+        cFoo.expectAvailableCallbacksUnvalidated(mWiFiNetworkAgent);
+        for (TestNetworkCallback c : emptyCallbacks) {
+            c.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier() == null,
+                    mWiFiNetworkAgent);
+        }
+        cFoo.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier() == null,
+                mWiFiNetworkAgent);
+        cBar.expectCapabilitiesLike((caps) -> caps.getNetworkSpecifier() == null,
+                mWiFiNetworkAgent);
+        assertNull(
+                mCm.getNetworkCapabilities(mWiFiNetworkAgent.getNetwork()).getNetworkSpecifier());
+        cFoo.assertNoCallback();
         cBar.assertNoCallback();
 
         mWiFiNetworkAgent.setNetworkSpecifier(null);
+        cFoo.expectCallback(CallbackState.LOST, mWiFiNetworkAgent);
         cBar.expectCallback(CallbackState.LOST, mWiFiNetworkAgent);
         for (TestNetworkCallback c: emptyCallbacks) {
             c.expectCallback(CallbackState.NETWORK_CAPABILITIES, mWiFiNetworkAgent);
         }
 
-        assertNoCallbacks(cEmpty1, cEmpty2, cEmpty3, cFoo, cBar);
+        assertNoCallbacks(cEmpty1, cEmpty2, cEmpty3, cEmpty4, cFoo, cBar);
     }
 
     @Test