Support DNS-over-TLS probes in NetworkDiagnostics

Probe DNS servers to see they support DNS-over-TLS. Use system
CAs to verify whether the certificates sent by DNS servers are
trusted or not. An error is thrown to cause the probe failed if
DNS servers send untrusted certificates.

Unlike the DnsResolver which doesn't verify the certificates
in opportunistic mode, all of the DoT probes from NetworkDiagnostics
check certificates.

DoT probes apply to the DNS servers gotten from LinkProperties
and the DoT servers gotten from PrivateDnsConfig whatever private
DNS mode is.

A common example in DNS strict mode:
.  DNS TLS dst{8.8.8.8} hostname{dns.google} src{192.168.43.2:48436} qtype{1} qname{815149-android-ds.metric.gstatic.com}: SUCCEEDED: 1/1 NOERROR (432ms)
F  DNS TLS dst{192.168.43.144} hostname{}: FAILED: java.net.ConnectException: failed to connect to /192.168.43.144 (port 853) from /192.168.43.2 (port 41770) after 2500ms: isConnected failed: ECONNREFUSED (Connection refused) (172ms)
.  DNS TLS dst{8.8.4.4} hostname{dns.google} src{192.168.43.2:37598} qtype{1} qname{759312-android-ds.metric.gstatic.com}: SUCCEEDED: 1/1 NOERROR (427ms)

An example when the CA is not trusted:
F  DNS TLS dst{8.8.8.8} hostname{dns.google}: FAILED: javax.net.ssl.SSLHandshakeException: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found. (16ms)

An example when TCP/TLS handshake timeout:
F  DNS TLS dst{8.8.8.8} hostname{dns.google}: FAILED: java.net.SocketTimeoutException: failed to connect to /8.8.8.8 (port 853) from /192.168.2.108 (port 45680) after 2500ms (2514ms)

Bug: 132925257
Bug: 118369977
Test: atest FrameworksNetTests
Change-Id: I1b54abed0e931ca4b8a97149459cde54da1c3d6f

1 files changed, 47 insertions, 0 deletions

diff --git a/tests/net/java/com/android/server/connectivity/DnsManagerTest.java b/tests/net/java/com/android/server/connectivity/DnsManagerTest.java
index 0a603b8e4b19..26a28da9755c 100644
--- a/tests/net/java/com/android/server/connectivity/DnsManagerTest.java
+++ b/tests/net/java/com/android/server/connectivity/DnsManagerTest.java
@@ -62,6 +62,8 @@ import androidx.test.runner.AndroidJUnit4;
 import com.android.internal.util.MessageUtils;
 import com.android.internal.util.test.FakeSettingsProvider;
 
+import libcore.net.InetAddressUtils;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -379,4 +381,49 @@ public class DnsManagerTest {
             assertEquals(name, dnsTransTypes.get(i));
         }
     }
+
+    @Test
+    public void testGetPrivateDnsConfigForNetwork() throws Exception {
+        final Network network = new Network(TEST_NETID);
+        final InetAddress dnsAddr = InetAddressUtils.parseNumericAddress("3.3.3.3");
+        final InetAddress[] tlsAddrs = new InetAddress[]{
+            InetAddressUtils.parseNumericAddress("6.6.6.6"),
+            InetAddressUtils.parseNumericAddress("2001:db8:66:66::1")
+        };
+        final String tlsName = "strictmode.com";
+        LinkProperties lp = new LinkProperties();
+        lp.addDnsServer(dnsAddr);
+
+        // The PrivateDnsConfig map is empty, so the default PRIVATE_DNS_OFF is returned.
+        PrivateDnsConfig privateDnsCfg = mDnsManager.getPrivateDnsConfig(network);
+        assertFalse(privateDnsCfg.useTls);
+        assertEquals("", privateDnsCfg.hostname);
+        assertEquals(new InetAddress[0], privateDnsCfg.ips);
+
+        // An entry with default PrivateDnsConfig is added to the PrivateDnsConfig map.
+        mDnsManager.updatePrivateDns(network, mDnsManager.getPrivateDnsConfig());
+        mDnsManager.noteDnsServersForNetwork(TEST_NETID, lp);
+        mDnsManager.updatePrivateDnsValidation(
+                new DnsManager.PrivateDnsValidationUpdate(TEST_NETID, dnsAddr, "", true));
+        mDnsManager.updatePrivateDnsStatus(TEST_NETID, lp);
+        privateDnsCfg = mDnsManager.getPrivateDnsConfig(network);
+        assertTrue(privateDnsCfg.useTls);
+        assertEquals("", privateDnsCfg.hostname);
+        assertEquals(new InetAddress[0], privateDnsCfg.ips);
+
+        // The original entry is overwritten by a new PrivateDnsConfig.
+        mDnsManager.updatePrivateDns(network, new PrivateDnsConfig(tlsName, tlsAddrs));
+        mDnsManager.updatePrivateDnsStatus(TEST_NETID, lp);
+        privateDnsCfg = mDnsManager.getPrivateDnsConfig(network);
+        assertTrue(privateDnsCfg.useTls);
+        assertEquals(tlsName, privateDnsCfg.hostname);
+        assertEquals(tlsAddrs, privateDnsCfg.ips);
+
+        // The network is removed, so the PrivateDnsConfig map becomes empty again.
+        mDnsManager.removeNetwork(network);
+        privateDnsCfg = mDnsManager.getPrivateDnsConfig(network);
+        assertFalse(privateDnsCfg.useTls);
+        assertEquals("", privateDnsCfg.hostname);
+        assertEquals(new InetAddress[0], privateDnsCfg.ips);
+    }
 }