Disable sockets and DNS if process lacks INTERNET permission.

This is a Client-only solution.
  - Add to NetdClient a per-process std::atomic_boolean
    similar to netIdForProcess and netIdForResolv.
  - The boolean says whether the process should be
    allowed Internet connectivity.
  - Add an @hide method to NetUtils.java to set the boolean;
    call it from the initialization code of the new
    process just after forking from zygote.
  - Make netdClientSocket and dnsOpenProxy check the
    boolean. If the boolean is false, return EPERM from
    socket calls.

Bug: 150028556
Test: atest NetworkUtilsTest
Test: atest CtsAppSecurityHostTestCases:UseProcessTest
Change-Id: If002280fbad493dfc2db3d9d505c0257d49a9056
Exempt-From-Owner-Approval: OWNERS already approved identical patchset 5

tests/net/java/android/net/NetworkUtilsTest.java

@@ -16,10 +16,24 @@
 
 package android.net;
 
+import static android.system.OsConstants.AF_INET;
+import static android.system.OsConstants.AF_INET6;
+import static android.system.OsConstants.AF_UNIX;
+import static android.system.OsConstants.EPERM;
+import static android.system.OsConstants.SOCK_DGRAM;
+import static android.system.OsConstants.SOCK_STREAM;
+
 import static junit.framework.Assert.assertEquals;
 
+import static org.junit.Assert.fail;
+
+import android.system.ErrnoException;
+import android.system.Os;
+
 import androidx.test.runner.AndroidJUnit4;
 
+import libcore.io.IoUtils;
+
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -125,4 +139,50 @@ public class NetworkUtilsTest {
         assertEquals(BigInteger.valueOf(7l - 4 + 4 + 16 + 65536),
                 NetworkUtils.routedIPv6AddressCount(set));
     }
+
+    private static void expectSocketSuccess(String msg, int domain, int type) {
+        try {
+            IoUtils.closeQuietly(Os.socket(domain, type, 0));
+        } catch (ErrnoException e) {
+            fail(msg + e.getMessage());
+        }
+    }
+
+    private static void expectSocketPemissionError(String msg, int domain, int type) {
+        try {
+            IoUtils.closeQuietly(Os.socket(domain, type, 0));
+            fail(msg);
+        } catch (ErrnoException e) {
+            assertEquals(msg, e.errno, EPERM);
+        }
+    }
+
+    private static void expectHasNetworking() {
+        expectSocketSuccess("Creating a UNIX socket should not have thrown ErrnoException",
+                AF_UNIX, SOCK_STREAM);
+        expectSocketSuccess("Creating a AF_INET socket shouldn't have thrown ErrnoException",
+                AF_INET, SOCK_DGRAM);
+        expectSocketSuccess("Creating a AF_INET6 socket shouldn't have thrown ErrnoException",
+                AF_INET6, SOCK_DGRAM);
+    }
+
+    private static void expectNoNetworking() {
+        expectSocketSuccess("Creating a UNIX socket should not have thrown ErrnoException",
+                AF_UNIX, SOCK_STREAM);
+        expectSocketPemissionError(
+                "Creating a AF_INET socket should have thrown ErrnoException(EPERM)",
+                AF_INET, SOCK_DGRAM);
+        expectSocketPemissionError(
+                "Creating a AF_INET6 socket should have thrown ErrnoException(EPERM)",
+                AF_INET6, SOCK_DGRAM);
+    }
+
+    @Test
+    public void testSetAllowNetworkingForProcess() {
+        expectHasNetworking();
+        NetworkUtils.setAllowNetworkingForProcess(false);
+        expectNoNetworking();
+        NetworkUtils.setAllowNetworkingForProcess(true);
+        expectHasNetworking();
+    }
 }