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Add test utils for SVCB packet generation.

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This is based on patchset 22 of aosp/2453209.

Bug: 240259333
Test: test-only code, will be covered by NetworkMonitorTest
Change-Id: Ibede3fb519e6f1d0c3d99886f553ee006ddfebc9
This commit is contained in:
Lorenzo Colitti 2024-09-03 09:52:57 +09:00
commit 93f2efbe86
1 changed files with 202 additions and 0 deletions
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202
staticlibs/testutils/devicetests/com/android/testutils/DnsSvcbUtils.java Normal file
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/*
* Copyright (C) 2024 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.testutils;
import static android.net.DnsResolver.CLASS_IN;
import static com.android.net.module.util.DnsPacket.TYPE_SVCB;
import static com.android.net.module.util.DnsPacketUtils.DnsRecordParser.domainNameToLabels;
import static com.android.net.module.util.NetworkStackConstants.IPV4_ADDR_LEN;
import static com.android.net.module.util.NetworkStackConstants.IPV6_ADDR_LEN;
import static org.junit.Assert.fail;
import static java.nio.charset.StandardCharsets.US_ASCII;
import android.net.InetAddresses;
import androidx.annotation.NonNull;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class DnsSvcbUtils {
private static final Pattern SVC_PARAM_PATTERN = Pattern.compile("([a-z0-9-]+)=?(.*)");
/**
* Returns a DNS SVCB response with given hostname `hostname` and given SVCB records
* `records`. Each record must contain the service priority, the target name, and the service
* parameters.
* E.g. "1 doh.google alpn=h2,h3 port=443 ipv4hint=192.0.2.1 dohpath=/dns-query{?dns}"
*/
@NonNull
public static byte[] makeSvcbResponse(String hostname, String[] records) throws IOException {
if (records == null) throw new NullPointerException();
if (!hostname.startsWith("_dns.")) throw new UnsupportedOperationException();
final ByteArrayOutputStream os = new ByteArrayOutputStream();
// Write DNS header.
os.write(shortsToByteArray(
0x1234, /* Transaction ID */
0x8100, /* Flags */
1, /* qdcount */
records.length, /* ancount */
0, /* nscount */
0 /* arcount */
));
// Write Question.
// - domainNameToLabels() doesn't support the hostname starting with "_", so divide
// the writing into two steps.
os.write(new byte[] { 0x04, '_', 'd', 'n', 's' });
os.write(domainNameToLabels(hostname.substring(5)));
os.write(shortsToByteArray(TYPE_SVCB, CLASS_IN));
// Write Answer section.
for (String r : records) {
os.write(makeSvcbRecord(r));
}
return os.toByteArray();
}
@NonNull
private static byte[] makeSvcbRecord(String representation) throws IOException {
if (representation == null) return new byte[0];
final ByteArrayOutputStream os = new ByteArrayOutputStream();
os.write(shortsToByteArray(
0xc00c, /* Pointer to qname in question section */
TYPE_SVCB,
CLASS_IN,
0, 16, /* TTL = 16 */
0 /* Data Length = 0 */
));
final String[] strings = representation.split(" +");
// SvcPriority and TargetName are mandatory in the representation.
if (strings.length < 3) {
fail("Invalid SVCB representation: " + representation);
}
// Write SvcPriority, TargetName, and SvcParams.
os.write(shortsToByteArray(Short.parseShort(strings[0])));
os.write(domainNameToLabels(strings[1]));
for (int i = 2; i < strings.length; i++) {
try {
os.write(svcParamToByteArray(strings[i]));
} catch (UnsupportedEncodingException e) {
throw new IOException(e);
}
}
// Update rdata length.
final byte[] out = os.toByteArray();
ByteBuffer.wrap(out).putShort(10, (short) (out.length - 12));
return out;
}
@NonNull
private static byte[] svcParamToByteArray(String svcParam) throws IOException {
final Matcher matcher = SVC_PARAM_PATTERN.matcher(svcParam);
if (!matcher.matches() || matcher.groupCount() != 2) {
fail("Invalid SvcParam: " + svcParam);
}
final String svcParamkey = matcher.group(1);
final String svcParamValue = matcher.group(2);
final ByteArrayOutputStream os = new ByteArrayOutputStream();
os.write(svcParamKeyToBytes(svcParamkey));
switch (svcParamkey) {
case "mandatory":
final String[] keys = svcParamValue.split(",");
os.write(shortsToByteArray(keys.length));
for (String v : keys) {
os.write(svcParamKeyToBytes(v));
}
break;
case "alpn":
os.write(shortsToByteArray((svcParamValue.length() + 1)));
for (String v : svcParamValue.split(",")) {
os.write(v.length());
// TODO: support percent-encoding per RFC 7838.
os.write(v.getBytes(US_ASCII));
}
break;
case "no-default-alpn":
os.write(shortsToByteArray(0));
break;
case "port":
os.write(shortsToByteArray(2));
os.write(shortsToByteArray(Short.parseShort(svcParamValue)));
break;
case "ipv4hint":
final String[] v4Addrs = svcParamValue.split(",");
os.write(shortsToByteArray((v4Addrs.length * IPV4_ADDR_LEN)));
for (String v : v4Addrs) {
os.write(InetAddresses.parseNumericAddress(v).getAddress());
}
break;
case "ech":
os.write(shortsToByteArray(svcParamValue.length()));
os.write(svcParamValue.getBytes(US_ASCII)); // base64 encoded
break;
case "ipv6hint":
final String[] v6Addrs = svcParamValue.split(",");
os.write(shortsToByteArray((v6Addrs.length * IPV6_ADDR_LEN)));
for (String v : v6Addrs) {
os.write(InetAddresses.parseNumericAddress(v).getAddress());
}
break;
case "dohpath":
os.write(shortsToByteArray(svcParamValue.length()));
// TODO: support percent-encoding, since this is a URI template.
os.write(svcParamValue.getBytes(US_ASCII));
break;
default:
os.write(shortsToByteArray(svcParamValue.length()));
os.write(svcParamValue.getBytes(US_ASCII));
break;
}
return os.toByteArray();
}
@NonNull
private static byte[] svcParamKeyToBytes(String key) {
switch (key) {
case "mandatory": return shortsToByteArray(0);
case "alpn": return shortsToByteArray(1);
case "no-default-alpn": return shortsToByteArray(2);
case "port": return shortsToByteArray(3);
case "ipv4hint": return shortsToByteArray(4);
case "ech": return shortsToByteArray(5);
case "ipv6hint": return shortsToByteArray(6);
case "dohpath": return shortsToByteArray(7);
default:
if (!key.startsWith("key")) fail("Invalid SvcParamKey " + key);
return shortsToByteArray(Short.parseShort(key.substring(3)));
}
}
@NonNull
private static byte[] shortsToByteArray(int... values) {
final ByteBuffer out = ByteBuffer.allocate(values.length * 2);
for (int value: values) {
if (value < 0 || value > 0xffff) {
throw new AssertionError("not an unsigned short: " + value);
}
out.putShort((short) value);
}
return out.array();
}
}