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Deal with null characters in string options.

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This currently truncates all strings at the first NULL character,
except for vendorInfo, which is an opaque string.

Bug: 19985674
Change-Id: Ie53b2c55eb8a5204d7b2c7e2d8587743d923647a
This commit is contained in:
Lorenzo Colitti
2015-03-31 16:26:57 +09:00
parent 3dda1fa418
commit c2abb2bf5e
3 changed files with 135 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
services/net/java/android/net/dhcp/DhcpPacket.java
View File

@@ -611,10 +611,22 @@ abstract class DhcpPacket {
/**
* Reads a string of specified length from the buffer.
*/
private static String readAsciiString(ByteBuffer buf, int byteCount) {
private static String readAsciiString(ByteBuffer buf, int byteCount, boolean nullOk) {
byte[] bytes = new byte[byteCount];
buf.get(bytes);
return new String(bytes, 0, bytes.length, StandardCharsets.US_ASCII);
int length = bytes.length;
if (!nullOk) {
// Stop at the first null byte. This is because some DHCP options (e.g., the domain
// name) are passed to netd via FrameworkListener, which refuses arguments containing
// null bytes. We don't do this by default because vendorInfo is an opaque string which
// could in theory contain null bytes.
for (length = 0; length < bytes.length; length++) {
if (bytes[length] == 0) {
break;
}
}
}
return new String(bytes, 0, length, StandardCharsets.US_ASCII);
}
/**
@@ -797,7 +809,7 @@ abstract class DhcpPacket {
break;
case DHCP_HOST_NAME:
expectedLen = optionLen;
hostName = readAsciiString(packet, optionLen);
hostName = readAsciiString(packet, optionLen, false);
break;
case DHCP_MTU:
expectedLen = 2;
@@ -805,7 +817,7 @@ abstract class DhcpPacket {
break;
case DHCP_DOMAIN_NAME:
expectedLen = optionLen;
domainName = readAsciiString(packet, optionLen);
domainName = readAsciiString(packet, optionLen, false);
break;
case DHCP_BROADCAST_ADDRESS:
bcAddr = readIpAddress(packet);
@@ -834,7 +846,7 @@ abstract class DhcpPacket {
break;
case DHCP_MESSAGE:
expectedLen = optionLen;
message = readAsciiString(packet, optionLen);
message = readAsciiString(packet, optionLen, false);
break;
case DHCP_MAX_MESSAGE_SIZE:
expectedLen = 2;
@@ -850,7 +862,7 @@ abstract class DhcpPacket {
break;
case DHCP_VENDOR_CLASS_ID:
expectedLen = optionLen;
vendorId = readAsciiString(packet, optionLen);
vendorId = readAsciiString(packet, optionLen, true);
break;
case DHCP_CLIENT_IDENTIFIER: { // Client identifier
byte[] id = new byte[optionLen];

1
services/tests/servicestests/Android.mk
View File

@@ -10,6 +10,7 @@ LOCAL_SRC_FILES := $(call all-java-files-under, src)
LOCAL_STATIC_JAVA_LIBRARIES := \
services.core \
services.devicepolicy \
services.net \
easymocklib \
guava \
mockito-target

116
services/tests/servicestests/src/android/net/dhcp/DhcpPacketTest.java Normal file
View File

@@ -0,0 +1,116 @@
/*
* Copyright (C) 2015 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 android.net.dhcp;
import android.net.NetworkUtils;
import android.system.OsConstants;
import android.test.suitebuilder.annotation.SmallTest;
import junit.framework.TestCase;
import java.net.Inet4Address;
import java.nio.ByteBuffer;
import static android.net.dhcp.DhcpPacket.*;
public class DhcpPacketTest extends TestCase {
private static Inet4Address SERVER_ADDR =
(Inet4Address) NetworkUtils.numericToInetAddress("192.0.2.1");
private static Inet4Address CLIENT_ADDR =
(Inet4Address) NetworkUtils.numericToInetAddress("192.0.2.234");
private static byte[] CLIENT_MAC = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05 };
class TestDhcpPacket extends DhcpPacket {
private byte mType;
// TODO: Make this a map of option numbers to bytes instead.
private byte[] mDomainBytes, mVendorInfoBytes;
public TestDhcpPacket(byte type, byte[] domainBytes, byte[] vendorInfoBytes) {
super(0xdeadbeef, INADDR_ANY, CLIENT_ADDR, INADDR_ANY, INADDR_ANY, CLIENT_MAC, true);
mType = type;
mDomainBytes = domainBytes;
mVendorInfoBytes = vendorInfoBytes;
}
public ByteBuffer buildPacket(int encap, short unusedDestUdp, short unusedSrcUdp) {
ByteBuffer result = ByteBuffer.allocate(MAX_LENGTH);
fillInPacket(encap, CLIENT_ADDR, SERVER_ADDR,
DHCP_CLIENT, DHCP_SERVER, result, DHCP_BOOTREPLY, false);
return result;
}
public void finishPacket(ByteBuffer buffer) {
addTlv(buffer, DHCP_MESSAGE_TYPE, mType);
if (mDomainBytes != null) {
addTlv(buffer, DHCP_DOMAIN_NAME, mDomainBytes);
}
if (mVendorInfoBytes != null) {
addTlv(buffer, DHCP_VENDOR_CLASS_ID, mVendorInfoBytes);
}
addTlvEnd(buffer);
}
// Convenience method.
public ByteBuffer build() {
// ENCAP_BOOTP packets don't contain ports, so just pass in 0.
ByteBuffer pkt = buildPacket(ENCAP_BOOTP, (short) 0, (short) 0);
pkt.flip();
return pkt;
}
}
private void assertDomainAndVendorInfoParses(
String expectedDomain, byte[] domainBytes,
String expectedVendorInfo, byte[] vendorInfoBytes) {
ByteBuffer packet = new TestDhcpPacket(DHCP_MESSAGE_TYPE_OFFER,
domainBytes, vendorInfoBytes).build();
DhcpPacket offerPacket = DhcpPacket.decodeFullPacket(packet, ENCAP_BOOTP);
assertEquals(expectedDomain, offerPacket.mDomainName);
assertEquals(expectedVendorInfo, offerPacket.mVendorId);
}
@SmallTest
public void testDomainName() throws Exception {
byte[] nullByte = new byte[] { 0x00 };
byte[] twoNullBytes = new byte[] { 0x00, 0x00 };
byte[] nonNullDomain = new byte[] {
(byte) 'g', (byte) 'o', (byte) 'o', (byte) '.', (byte) 'g', (byte) 'l'
};
byte[] trailingNullDomain = new byte[] {
(byte) 'g', (byte) 'o', (byte) 'o', (byte) '.', (byte) 'g', (byte) 'l', 0x00
};
byte[] embeddedNullsDomain = new byte[] {
(byte) 'g', (byte) 'o', (byte) 'o', 0x00, 0x00, (byte) 'g', (byte) 'l'
};
byte[] metered = "ANDROID_METERED".getBytes("US-ASCII");
byte[] meteredEmbeddedNull = metered.clone();
meteredEmbeddedNull[7] = (char) 0;
byte[] meteredTrailingNull = metered.clone();
meteredTrailingNull[meteredTrailingNull.length - 1] = (char) 0;
assertDomainAndVendorInfoParses("", nullByte, "\u0000", nullByte);
assertDomainAndVendorInfoParses("", twoNullBytes, "\u0000\u0000", twoNullBytes);
assertDomainAndVendorInfoParses("goo.gl", nonNullDomain, "ANDROID_METERED", metered);
assertDomainAndVendorInfoParses("goo", embeddedNullsDomain,
"ANDROID\u0000METERED", meteredEmbeddedNull);
assertDomainAndVendorInfoParses("goo.gl", trailingNullDomain,
"ANDROID_METERE\u0000", meteredTrailingNull);
}
}