/*
* Copyright (C) 2018 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.apksig;
import static com.android.apksig.internal.apk.ApkSigningBlockUtils.getLengthPrefixedSlice;
import com.android.apksig.apk.ApkFormatException;
import com.android.apksig.apk.ApkUtils;
import com.android.apksig.internal.apk.ApkSigningBlockUtils;
import com.android.apksig.internal.apk.SignatureAlgorithm;
import com.android.apksig.internal.apk.SignatureInfo;
import com.android.apksig.internal.apk.v3.V3SchemeConstants;
import com.android.apksig.internal.apk.v3.V3SchemeSigner;
import com.android.apksig.internal.apk.v3.V3SigningCertificateLineage;
import com.android.apksig.internal.apk.v3.V3SigningCertificateLineage.SigningCertificateNode;
import com.android.apksig.internal.util.AndroidSdkVersion;
import com.android.apksig.internal.util.ByteBufferUtils;
import com.android.apksig.internal.util.Pair;
import com.android.apksig.internal.util.RandomAccessFileDataSink;
import com.android.apksig.util.DataSink;
import com.android.apksig.util.DataSource;
import com.android.apksig.util.DataSources;
import com.android.apksig.zip.ZipFormatException;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SignatureException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/**
* APK Signer Lineage.
*
* <p>The signer lineage contains a history of signing certificates with each ancestor attesting to
* the validity of its descendant. Each additional descendant represents a new identity that can be
* used to sign an APK, and each generation has accompanying attributes which represent how the
* APK would like to view the older signing certificates, specifically how they should be trusted in
* certain situations.
*
* <p> Its primary use is to enable APK Signing Certificate Rotation. The Android platform verifies
* the APK Signer Lineage, and if the current signing certificate for the APK is in the Signer
* Lineage, and the Lineage contains the certificate the platform associates with the APK, it will
* allow upgrades to the new certificate.
*
* @see <a href="https://source.android.com/security/apksigning/index.html">Application Signing</a>
*/
public class SigningCertificateLineage {
public final static int MAGIC = 0x3eff39d1;
private final static int FIRST_VERSION = 1;
private static final int CURRENT_VERSION = FIRST_VERSION;
/** accept data from already installed pkg with this cert */
private static final int PAST_CERT_INSTALLED_DATA = 1;
/** accept sharedUserId with pkg with this cert */
private static final int PAST_CERT_SHARED_USER_ID = 2;
/** grant SIGNATURE permissions to pkgs with this cert */
private static final int PAST_CERT_PERMISSION = 4;
/**
* Enable updates back to this certificate. WARNING: this effectively removes any benefit of
* signing certificate changes, since a compromised key could retake control of an app even
* after change, and should only be used if there is a problem encountered when trying to ditch
* an older cert.
*/
private static final int PAST_CERT_ROLLBACK = 8;
/**
* Preserve authenticator module-based access in AccountManager gated by signing certificate.
*/
private static final int PAST_CERT_AUTH = 16;
private final int mMinSdkVersion;
/**
* The signing lineage is just a list of nodes, with the first being the original signing
* certificate and the most recent being the one with which the APK is to actually be signed.
*/
private final List<SigningCertificateNode> mSigningLineage;
private SigningCertificateLineage(int minSdkVersion, List<SigningCertificateNode> list) {
mMinSdkVersion = minSdkVersion;
mSigningLineage = list;
}
/**
* Creates a {@code SigningCertificateLineage} with a single signer in the lineage.
*/
private static SigningCertificateLineage createSigningLineage(int minSdkVersion,
SignerConfig signer, SignerCapabilities capabilities) {
SigningCertificateLineage signingCertificateLineage = new SigningCertificateLineage(
minSdkVersion, new ArrayList<>());
return signingCertificateLineage.spawnFirstDescendant(signer, capabilities);
}
private static SigningCertificateLineage createSigningLineage(
int minSdkVersion, SignerConfig parent, SignerCapabilities parentCapabilities,
SignerConfig child, SignerCapabilities childCapabilities)
throws CertificateEncodingException, InvalidKeyException, NoSuchAlgorithmException,
SignatureException {
SigningCertificateLineage signingCertificateLineage =
new SigningCertificateLineage(minSdkVersion, new ArrayList<>());
signingCertificateLineage =
signingCertificateLineage.spawnFirstDescendant(parent, parentCapabilities);
return signingCertificateLineage.spawnDescendant(parent, child, childCapabilities);
}
public static SigningCertificateLineage readFromBytes(byte[] lineageBytes)
throws IOException {
return readFromDataSource(DataSources.asDataSource(ByteBuffer.wrap(lineageBytes)));
}
public static SigningCertificateLineage readFromFile(File file)
throws IOException {
if (file == null) {
throw new NullPointerException("file == null");
}
RandomAccessFile inputFile = new RandomAccessFile(file, "r");
return readFromDataSource(DataSources.asDataSource(inputFile));
}
public static SigningCertificateLineage readFromDataSource(DataSource dataSource)
throws IOException {
if (dataSource == null) {
throw new NullPointerException("dataSource == null");
}
ByteBuffer inBuff = dataSource.getByteBuffer(0, (int) dataSource.size());
inBuff.order(ByteOrder.LITTLE_ENDIAN);
return read(inBuff);
}
/**
* Extracts a Signing Certificate Lineage from a v3 signer proof-of-rotation attribute.
*
* <note>
* this may not give a complete representation of an APK's signing certificate history,
* since the APK may have multiple signers corresponding to different platform versions.
* Use <code> readFromApkFile</code> to handle this case.
* </note>
* @param attrValue
*/
public static SigningCertificateLineage readFromV3AttributeValue(byte[] attrValue)
throws IOException {
List<SigningCertificateNode> parsedLineage =
V3SigningCertificateLineage.readSigningCertificateLineage(ByteBuffer.wrap(
attrValue).order(ByteOrder.LITTLE_ENDIAN));
int minSdkVersion = calculateMinSdkVersion(parsedLineage);
return new SigningCertificateLineage(minSdkVersion, parsedLineage);
}
/**
* Extracts a Signing Certificate Lineage from the proof-of-rotation attribute in the V3
* signature block of the provided APK File.
*
* @throws IllegalArgumentException if the provided APK does not contain a V3 signature block,
* or if the V3 signature block does not contain a valid lineage.
*/
public static SigningCertificateLineage readFromApkFile(File apkFile)
throws IOException, ApkFormatException {
try (RandomAccessFile f = new RandomAccessFile(apkFile, "r")) {
DataSource apk = DataSources.asDataSource(f, 0, f.length());
return readFromApkDataSource(apk);
}
}
/**
* Extracts a Signing Certificate Lineage from the proof-of-rotation attribute in the V3 and
* V3.1 signature blocks of the provided APK DataSource.
*
* @throws IllegalArgumentException if the provided APK does not contain a V3 nor V3.1
* signature block, or if the V3 and V3.1 signature blocks do not contain a valid lineage.
*/
public static SigningCertificateLineage readFromApkDataSource(DataSource apk)
throws IOException, ApkFormatException {
return readFromApkDataSource(apk, /* readV31Lineage= */ true, /* readV3Lineage= */true);
}
/**
* Extracts a Signing Certificate Lineage from the proof-of-rotation attribute in the V3.1
* signature blocks of the provided APK DataSource.
*
* @throws IllegalArgumentException if the provided APK does not contain a V3.1 signature block,
* or if the V3.1 signature block does not contain a valid lineage.
*/
public static SigningCertificateLineage readV31FromApkDataSource(DataSource apk)
throws IOException, ApkFormatException {
return readFromApkDataSource(apk, /* readV31Lineage= */ true,
/* readV3Lineage= */ false);
}
private static SigningCertificateLineage readFromApkDataSource(
DataSource apk,
boolean readV31Lineage,
boolean readV3Lineage)
throws IOException, ApkFormatException {
ApkUtils.ZipSections zipSections;
try {
zipSections = ApkUtils.findZipSections(apk);
} catch (ZipFormatException e) {
throw new ApkFormatException(e.getMessage());
}
List<SignatureInfo> signatureInfoList = new ArrayList<>();
if (readV31Lineage) {
try {
ApkSigningBlockUtils.Result result = new ApkSigningBlockUtils.Result(
ApkSigningBlockUtils.VERSION_APK_SIGNATURE_SCHEME_V31);
signatureInfoList.add(
ApkSigningBlockUtils.findSignature(apk, zipSections,
V3SchemeConstants.APK_SIGNATURE_SCHEME_V31_BLOCK_ID, result));
} catch (ApkSigningBlockUtils.SignatureNotFoundException ignored) {
// This could be expected if there's only a V3 signature block.
}
}
if (readV3Lineage) {
try {
ApkSigningBlockUtils.Result result = new ApkSigningBlockUtils.Result(
ApkSigningBlockUtils.VERSION_APK_SIGNATURE_SCHEME_V3);
signatureInfoList.add(
ApkSigningBlockUtils.findSignature(apk, zipSections,
V3SchemeConstants.APK_SIGNATURE_SCHEME_V3_BLOCK_ID, result));
} catch (ApkSigningBlockUtils.SignatureNotFoundException ignored) {
// This could be expected if the provided APK is not signed with the V3 signature
// scheme
}
}
if (signatureInfoList.isEmpty()) {
String message;
if (readV31Lineage && readV3Lineage) {
message = "The provided APK does not contain a valid V3 nor V3.1 signature block.";
} else if (readV31Lineage) {
message = "The provided APK does not contain a valid V3.1 signature block.";
} else if (readV3Lineage) {
message = "The provided APK does not contain a valid V3 signature block.";
} else {
message = "No signature blocks were requested.";
}
throw new IllegalArgumentException(message);
}
List<SigningCertificateLineage> lineages = new ArrayList<>(1);
for (SignatureInfo signatureInfo : signatureInfoList) {
// FORMAT:
// * length-prefixed sequence of length-prefixed signers:
// * length-prefixed signed data
// * minSDK
// * maxSDK
// * length-prefixed sequence of length-prefixed signatures
// * length-prefixed public key
ByteBuffer signers = getLengthPrefixedSlice(signatureInfo.signatureBlock);
while (signers.hasRemaining()) {
ByteBuffer signer = getLengthPrefixedSlice(signers);
ByteBuffer signedData = getLengthPrefixedSlice(signer);
try {
SigningCertificateLineage lineage = readFromSignedData(signedData);
lineages.add(lineage);
} catch (IllegalArgumentException ignored) {
// The current signer block does not contain a valid lineage, but it is possible
// another block will.
}
}
}
SigningCertificateLineage result;
if (lineages.isEmpty()) {
throw new IllegalArgumentException(
"The provided APK does not contain a valid lineage.");
} else if (lineages.size() > 1) {
result = consolidateLineages(lineages);
} else {
result = lineages.get(0);
}
return result;
}
/**
* Extracts a Signing Certificate Lineage from the proof-of-rotation attribute in the provided
* signed data portion of a signer in a V3 signature block.
*
* @throws IllegalArgumentException if the provided signed data does not contain a valid
* lineage.
*/
public static SigningCertificateLineage readFromSignedData(ByteBuffer signedData)
throws IOException, ApkFormatException {
// FORMAT:
// * length-prefixed sequence of length-prefixed digests:
// * length-prefixed sequence of certificates:
// * length-prefixed bytes: X.509 certificate (ASN.1 DER encoded).
// * uint-32: minSdkVersion
// * uint-32: maxSdkVersion
// * length-prefixed sequence of length-prefixed additional attributes:
// * uint32: ID
// * (length - 4) bytes: value
// * uint32: Proof-of-rotation ID: 0x3ba06f8c
// * length-prefixed proof-of-rotation structure
// consume the digests through the maxSdkVersion to reach the lineage in the attributes
getLengthPrefixedSlice(signedData);
getLengthPrefixedSlice(signedData);
signedData.getInt();
signedData.getInt();
// iterate over the additional attributes adding any lineages to the List
ByteBuffer additionalAttributes = getLengthPrefixedSlice(signedData);
List<SigningCertificateLineage> lineages = new ArrayList<>(1);
while (additionalAttributes.hasRemaining()) {
ByteBuffer attribute = getLengthPrefixedSlice(additionalAttributes);
int id = attribute.getInt();
if (id == V3SchemeConstants.PROOF_OF_ROTATION_ATTR_ID) {
byte[] value = ByteBufferUtils.toByteArray(attribute);
SigningCertificateLineage lineage = readFromV3AttributeValue(value);
lineages.add(lineage);
}
}
SigningCertificateLineage result;
// There should only be a single attribute with the lineage, but if there are multiple then
// attempt to consolidate the lineages.
if (lineages.isEmpty()) {
throw new IllegalArgumentException("The signed data does not contain a valid lineage.");
} else if (lineages.size() > 1) {
result = consolidateLineages(lineages);
} else {
result = lineages.get(0);
}
return result;
}
public byte[] getBytes() {
return write().array();
}
public void writeToFile(File file) throws IOException {
if (file == null) {
throw new NullPointerException("file == null");
}
RandomAccessFile outputFile = new RandomAccessFile(file, "rw");
writeToDataSink(new RandomAccessFileDataSink(outputFile));
}
public void writeToDataSink(DataSink dataSink) throws IOException {
if (dataSink == null) {
throw new NullPointerException("dataSink == null");
}
dataSink.consume(write());
}
/**
* Add a new signing certificate to the lineage. This effectively creates a signing certificate
* rotation event, forcing APKs which include this lineage to be signed by the new signer. The
* flags associated with the new signer are set to a default value.
*
* @param parent current signing certificate of the containing APK
* @param child new signing certificate which will sign the APK contents
*/
public SigningCertificateLineage spawnDescendant(SignerConfig parent, SignerConfig child)
throws CertificateEncodingException, InvalidKeyException, NoSuchAlgorithmException,
SignatureException {
if (parent == null || child == null) {
throw new NullPointerException("can't add new descendant to lineage with null inputs");
}
SignerCapabilities signerCapabilities = new SignerCapabilities.Builder().build();
return spawnDescendant(parent, child, signerCapabilities);
}
/**
* Add a new signing certificate to the lineage. This effectively creates a signing certificate
* rotation event, forcing APKs which include this lineage to be signed by the new signer.
*
* @param parent current signing certificate of the containing APK
* @param child new signing certificate which will sign the APK contents
* @param childCapabilities flags
*/
public SigningCertificateLineage spawnDescendant(
SignerConfig parent, SignerConfig child, SignerCapabilities childCapabilities)
throws CertificateEncodingException, InvalidKeyException,
NoSuchAlgorithmException, SignatureException {
if (parent == null) {
throw new NullPointerException("parent == null");
}
if (child == null) {
throw new NullPointerException("child == null");
}
if (childCapabilities == null) {
throw new NullPointerException("childCapabilities == null");
}
if (mSigningLineage.isEmpty()) {
throw new IllegalArgumentException("Cannot spawn descendant signing certificate on an"
+ " empty SigningCertificateLineage: no parent node");
}
// make sure that the parent matches our newest generation (leaf node/sink)
SigningCertificateNode currentGeneration = mSigningLineage.get(mSigningLineage.size() - 1);
if (!Arrays.equals(currentGeneration.signingCert.getEncoded(),
parent.getCertificate().getEncoded())) {
throw new IllegalArgumentException("SignerConfig Certificate containing private key"
+ " to sign the new SigningCertificateLineage record does not match the"
+ " existing most recent record");
}
// create data to be signed, including the algorithm we're going to use
SignatureAlgorithm signatureAlgorithm = getSignatureAlgorithm(parent);
ByteBuffer prefixedSignedData = ByteBuffer.wrap(
V3SigningCertificateLineage.encodeSignedData(
child.getCertificate(), signatureAlgorithm.getId()));
prefixedSignedData.position(4);
ByteBuffer signedDataBuffer = ByteBuffer.allocate(prefixedSignedData.remaining());
signedDataBuffer.put(prefixedSignedData);
byte[] signedData = signedDataBuffer.array();
// create SignerConfig to do the signing
List<X509Certificate> certificates = new ArrayList<>(1);
certificates.add(parent.getCertificate());
ApkSigningBlockUtils.SignerConfig newSignerConfig =
new ApkSigningBlockUtils.SignerConfig();
newSignerConfig.privateKey = parent.getPrivateKey();
newSignerConfig.certificates = certificates;
newSignerConfig.signatureAlgorithms = Collections.singletonList(signatureAlgorithm);
// sign it
List<Pair<Integer, byte[]>> signatures =
ApkSigningBlockUtils.generateSignaturesOverData(newSignerConfig, signedData);
// finally, add it to our lineage
SignatureAlgorithm sigAlgorithm = SignatureAlgorithm.findById(signatures.get(0).getFirst());
byte[] signature = signatures.get(0).getSecond();
currentGeneration.sigAlgorithm = sigAlgorithm;
SigningCertificateNode childNode =
new SigningCertificateNode(
child.getCertificate(), sigAlgorithm, null,
signature, childCapabilities.getFlags());
List<SigningCertificateNode> lineageCopy = new ArrayList<>(mSigningLineage);
lineageCopy.add(childNode);
return new SigningCertificateLineage(mMinSdkVersion, lineageCopy);
}
/**
* The number of signing certificates in the lineage, including the current signer, which means
* this value can also be used to V2determine the number of signing certificate rotations by
* subtracting 1.
*/
public int size() {
return mSigningLineage.size();
}
private SignatureAlgorithm getSignatureAlgorithm(SignerConfig parent)
throws InvalidKeyException {
PublicKey publicKey = parent.getCertificate().getPublicKey();
// TODO switch to one signature algorithm selection, or add support for multiple algorithms
List<SignatureAlgorithm> algorithms = V3SchemeSigner.getSuggestedSignatureAlgorithms(
publicKey, mMinSdkVersion, false /* verityEnabled */,
false /* deterministicDsaSigning */);
return algorithms.get(0);
}
private SigningCertificateLineage spawnFirstDescendant(
SignerConfig parent, SignerCapabilities signerCapabilities) {
if (!mSigningLineage.isEmpty()) {
throw new IllegalStateException("SigningCertificateLineage already has its first node");
}
// check to make sure that the public key for the first node is acceptable for our minSdk
try {
getSignatureAlgorithm(parent);
} catch (InvalidKeyException e) {
throw new IllegalArgumentException("Algorithm associated with first signing certificate"
+ " invalid on desired platform versions", e);
}
// create "fake" signed data (there will be no signature over it, since there is no parent
SigningCertificateNode firstNode = new SigningCertificateNode(
parent.getCertificate(), null, null, new byte[0], signerCapabilities.getFlags());
return new SigningCertificateLineage(mMinSdkVersion, Collections.singletonList(firstNode));
}
private static SigningCertificateLineage read(ByteBuffer inputByteBuffer)
throws IOException {
ApkSigningBlockUtils.checkByteOrderLittleEndian(inputByteBuffer);
if (inputByteBuffer.remaining() < 8) {
throw new IllegalArgumentException(
"Improper SigningCertificateLineage format: insufficient data for header.");
}
if (inputByteBuffer.getInt() != MAGIC) {
throw new IllegalArgumentException(
"Improper SigningCertificateLineage format: MAGIC header mismatch.");
}
return read(inputByteBuffer, inputByteBuffer.getInt());
}
private static SigningCertificateLineage read(ByteBuffer inputByteBuffer, int version)
throws IOException {
switch (version) {
case FIRST_VERSION:
try {
List<SigningCertificateNode> nodes =
V3SigningCertificateLineage.readSigningCertificateLineage(
getLengthPrefixedSlice(inputByteBuffer));
int minSdkVersion = calculateMinSdkVersion(nodes);
return new SigningCertificateLineage(minSdkVersion, nodes);
} catch (ApkFormatException e) {
// unable to get a proper length-prefixed lineage slice
throw new IOException("Unable to read list of signing certificate nodes in "
+ "SigningCertificateLineage", e);
}
default:
throw new IllegalArgumentException(
"Improper SigningCertificateLineage format: unrecognized version.");
}
}
private static int calculateMinSdkVersion(List<SigningCertificateNode> nodes) {
if (nodes == null) {
throw new IllegalArgumentException("Can't calculate minimum SDK version of null nodes");
}
int minSdkVersion = AndroidSdkVersion.P; // lineage introduced in P
for (SigningCertificateNode node : nodes) {
if (node.sigAlgorithm != null) {
int nodeMinSdkVersion = node.sigAlgorithm.getMinSdkVersion();
if (nodeMinSdkVersion > minSdkVersion) {
minSdkVersion = nodeMinSdkVersion;
}
}
}
return minSdkVersion;
}
private ByteBuffer write() {
byte[] encodedLineage =
V3SigningCertificateLineage.encodeSigningCertificateLineage(mSigningLineage);
int payloadSize = 4 + 4 + 4 + encodedLineage.length;
ByteBuffer result = ByteBuffer.allocate(payloadSize);
result.order(ByteOrder.LITTLE_ENDIAN);
result.putInt(MAGIC);
result.putInt(CURRENT_VERSION);
result.putInt(encodedLineage.length);
result.put(encodedLineage);
result.flip();
return result;
}
public byte[] encodeSigningCertificateLineage() {
return V3SigningCertificateLineage.encodeSigningCertificateLineage(mSigningLineage);
}
public List<DefaultApkSignerEngine.SignerConfig> sortSignerConfigs(
List<DefaultApkSignerEngine.SignerConfig> signerConfigs) {
if (signerConfigs == null) {
throw new NullPointerException("signerConfigs == null");
}
// not the most elegant sort, but we expect signerConfigs to be quite small (1 or 2 signers
// in most cases) and likely already sorted, so not worth the overhead of doing anything
// fancier
List<DefaultApkSignerEngine.SignerConfig> sortedSignerConfigs =
new ArrayList<>(signerConfigs.size());
for (int i = 0; i < mSigningLineage.size(); i++) {
for (int j = 0; j < signerConfigs.size(); j++) {
DefaultApkSignerEngine.SignerConfig config = signerConfigs.get(j);
if (mSigningLineage.get(i).signingCert.equals(config.getCertificates().get(0))) {
sortedSignerConfigs.add(config);
break;
}
}
}
if (sortedSignerConfigs.size() != signerConfigs.size()) {
throw new IllegalArgumentException("SignerConfigs supplied which are not present in the"
+ " SigningCertificateLineage");
}
return sortedSignerConfigs;
}
/**
* Returns the SignerCapabilities for the signer in the lineage that matches the provided
* config.
*/
public SignerCapabilities getSignerCapabilities(SignerConfig config) {
if (config == null) {
throw new NullPointerException("config == null");
}
X509Certificate cert = config.getCertificate();
return getSignerCapabilities(cert);
}
/**
* Returns the SignerCapabilities for the signer in the lineage that matches the provided
* certificate.
*/
public SignerCapabilities getSignerCapabilities(X509Certificate cert) {
if (cert == null) {
throw new NullPointerException("cert == null");
}
for (int i = 0; i < mSigningLineage.size(); i++) {
SigningCertificateNode lineageNode = mSigningLineage.get(i);
if (lineageNode.signingCert.equals(cert)) {
int flags = lineageNode.flags;
return new SignerCapabilities.Builder(flags).build();
}
}
// the provided signer certificate was not found in the lineage
throw new IllegalArgumentException("Certificate (" + cert.getSubjectDN()
+ ") not found in the SigningCertificateLineage");
}
/**
* Updates the SignerCapabilities for the signer in the lineage that matches the provided
* config. Only those capabilities that have been modified through the setXX methods will be
* updated for the signer to prevent unset default values from being applied.
*/
public void updateSignerCapabilities(SignerConfig config, SignerCapabilities capabilities) {
if (config == null) {
throw new NullPointerException("config == null");
}
updateSignerCapabilities(config.getCertificate(), capabilities);
}
/**
* Updates the {@code capabilities} for the signer with the provided {@code certificate} in the
* lineage. Only those capabilities that have been modified through the setXX methods will be
* updated for the signer to prevent unset default values from being applied.
*/
public void updateSignerCapabilities(X509Certificate certificate,
SignerCapabilities capabilities) {
if (certificate == null) {
throw new NullPointerException("config == null");
}
for (int i = 0; i < mSigningLineage.size(); i++) {
SigningCertificateNode lineageNode = mSigningLineage.get(i);
if (lineageNode.signingCert.equals(certificate)) {
int flags = lineageNode.flags;
SignerCapabilities newCapabilities = new SignerCapabilities.Builder(
flags).setCallerConfiguredCapabilities(capabilities).build();
lineageNode.flags = newCapabilities.getFlags();
return;
}
}
// the provided signer config was not found in the lineage
throw new IllegalArgumentException("Certificate (" + certificate.getSubjectDN()
+ ") not found in the SigningCertificateLineage");
}
/**
* Returns a list containing all of the certificates in the lineage.
*/
public List<X509Certificate> getCertificatesInLineage() {
List<X509Certificate> certs = new ArrayList<>();
for (int i = 0; i < mSigningLineage.size(); i++) {
X509Certificate cert = mSigningLineage.get(i).signingCert;
certs.add(cert);
}
return certs;
}
/**
* Returns {@code true} if the specified config is in the lineage.
*/
public boolean isSignerInLineage(SignerConfig config) {
if (config == null) {
throw new NullPointerException("config == null");
}
X509Certificate cert = config.getCertificate();
return isCertificateInLineage(cert);
}
/**
* Returns {@code true} if the specified certificate is in the lineage.
*/
public boolean isCertificateInLineage(X509Certificate cert) {
if (cert == null) {
throw new NullPointerException("cert == null");
}
for (int i = 0; i < mSigningLineage.size(); i++) {
if (mSigningLineage.get(i).signingCert.equals(cert)) {
return true;
}
}
return false;
}
/**
* Returns whether the provided {@code cert} is the latest signing certificate in the lineage.
*
* <p>This method will only compare the provided {@code cert} against the latest signing
* certificate in the lineage; if a certificate that is not in the lineage is provided, this
* method will return false.
*/
public boolean isCertificateLatestInLineage(X509Certificate cert) {
if (cert == null) {
throw new NullPointerException("cert == null");
}
return mSigningLineage.get(mSigningLineage.size() - 1).signingCert.equals(cert);
}
private static int calculateDefaultFlags() {
return PAST_CERT_INSTALLED_DATA | PAST_CERT_PERMISSION
| PAST_CERT_SHARED_USER_ID | PAST_CERT_AUTH;
}
/**
* Returns a new SigningCertificateLineage which terminates at the node corresponding to the
* given certificate. This is useful in the event of rotating to a new signing algorithm that
* is only supported on some platform versions. It enables a v3 signature to be generated using
* this signing certificate and the shortened proof-of-rotation record from this sub lineage in
* conjunction with the appropriate SDK version values.
*
* @param x509Certificate the signing certificate for which to search
* @return A new SigningCertificateLineage if the given certificate is present.
*
* @throws IllegalArgumentException if the provided certificate is not in the lineage.
*/
public SigningCertificateLineage getSubLineage(X509Certificate x509Certificate) {
if (x509Certificate == null) {
throw new NullPointerException("x509Certificate == null");
}
for (int i = 0; i < mSigningLineage.size(); i++) {
if (mSigningLineage.get(i).signingCert.equals(x509Certificate)) {
return new SigningCertificateLineage(
mMinSdkVersion, new ArrayList<>(mSigningLineage.subList(0, i + 1)));
}
}
// looks like we didn't find the cert,
throw new IllegalArgumentException("Certificate not found in SigningCertificateLineage");
}
/**
* Consolidates all of the lineages found in an APK into one lineage. In so doing, it also
* checks that all of the lineages are contained in one common lineage.
*
* An APK may contain multiple lineages, one for each signer, which correspond to different
* supported platform versions. In this event, the lineage(s) from the earlier platform
* version(s) should be present in the most recent, either directly or via a sublineage
* that would allow the earlier lineages to merge with the most recent.
*
* <note> This does not verify that the largest lineage corresponds to the most recent supported
* platform version. That check is performed during v3 verification. </note>
*/
public static SigningCertificateLineage consolidateLineages(
List<SigningCertificateLineage> lineages) {
if (lineages == null || lineages.isEmpty()) {
return null;
}
SigningCertificateLineage consolidatedLineage = lineages.get(0);
for (int i = 1; i < lineages.size(); i++) {
consolidatedLineage = consolidatedLineage.mergeLineageWith(lineages.get(i));
}
return consolidatedLineage;
}
/**
* Merges this lineage with the provided {@code otherLineage}.
*
* <p>The merged lineage does not currently handle merging capabilities of common signers and
* should only be used to determine the full signing history of a collection of lineages.
*/
public SigningCertificateLineage mergeLineageWith(SigningCertificateLineage otherLineage) {
// Determine the ancestor and descendant lineages; if the original signer is in the other
// lineage, then it is considered a descendant.
SigningCertificateLineage ancestorLineage;
SigningCertificateLineage descendantLineage;
X509Certificate signerCert = mSigningLineage.get(0).signingCert;
if (otherLineage.isCertificateInLineage(signerCert)) {
descendantLineage = this;
ancestorLineage = otherLineage;
} else {
descendantLineage = otherLineage;
ancestorLineage = this;
}
int ancestorIndex = 0;
int descendantIndex = 0;
SigningCertificateNode ancestorNode;
SigningCertificateNode descendantNode = descendantLineage.mSigningLineage.get(
descendantIndex++);
List<SigningCertificateNode> mergedLineage = new ArrayList<>();
// Iterate through the ancestor lineage and add the current node to the resulting lineage
// until the first node of the descendant is found.
while (ancestorIndex < ancestorLineage.size()) {
ancestorNode = ancestorLineage.mSigningLineage.get(ancestorIndex++);
if (ancestorNode.signingCert.equals(descendantNode.signingCert)) {
break;
}
mergedLineage.add(ancestorNode);
}
// If all of the nodes in the ancestor lineage have been added to the merged lineage, then
// there is no overlap between this and the provided lineage.
if (ancestorIndex == mergedLineage.size()) {
throw new IllegalArgumentException(
"The provided lineage is not a descendant or an ancestor of this lineage");
}
// The descendant lineage's first node was in the ancestor's lineage above; add it to the
// merged lineage.
mergedLineage.add(descendantNode);
while (ancestorIndex < ancestorLineage.size()
&& descendantIndex < descendantLineage.size()) {
ancestorNode = ancestorLineage.mSigningLineage.get(ancestorIndex++);
descendantNode = descendantLineage.mSigningLineage.get(descendantIndex++);
if (!ancestorNode.signingCert.equals(descendantNode.signingCert)) {
throw new IllegalArgumentException(
"The provided lineage diverges from this lineage");
}
mergedLineage.add(descendantNode);
}
// At this point, one or both of the lineages have been exhausted and all signers to this
// point were a match between the two lineages; add any remaining elements from either
// lineage to the merged lineage.
while (ancestorIndex < ancestorLineage.size()) {
mergedLineage.add(ancestorLineage.mSigningLineage.get(ancestorIndex++));
}
while (descendantIndex < descendantLineage.size()) {
mergedLineage.add(descendantLineage.mSigningLineage.get(descendantIndex++));
}
return new SigningCertificateLineage(Math.min(mMinSdkVersion, otherLineage.mMinSdkVersion),
mergedLineage);
}
/**
* Checks whether given lineages are compatible. Returns {@code true} if an installed APK with
* the oldLineage could be updated with an APK with the newLineage.
*/
public static boolean checkLineagesCompatibility(
SigningCertificateLineage oldLineage, SigningCertificateLineage newLineage) {
final ArrayList<X509Certificate> oldCertificates = oldLineage == null ?
new ArrayList<X509Certificate>()
: new ArrayList(oldLineage.getCertificatesInLineage());
final ArrayList<X509Certificate> newCertificates = newLineage == null ?
new ArrayList<X509Certificate>()
: new ArrayList(newLineage.getCertificatesInLineage());
if (oldCertificates.isEmpty()) {
return true;
}
if (newCertificates.isEmpty()) {
return false;
}
// Both lineages contain exactly the same certificates or the new lineage extends
// the old one. The capabilities of particular certificates may have changed though but it
// does not matter in terms of current compatibility.
if (newCertificates.size() >= oldCertificates.size()
&& newCertificates.subList(0, oldCertificates.size()).equals(oldCertificates)) {
return true;
}
ArrayList<X509Certificate> newCertificatesArray = new ArrayList(newCertificates);
ArrayList<X509Certificate> oldCertificatesArray = new ArrayList(oldCertificates);
int lastOldCertIndexInNew = newCertificatesArray.lastIndexOf(
oldCertificatesArray.get(oldCertificatesArray.size()-1));
// The new lineage trims some nodes from the beginning of the old lineage and possibly
// extends it at the end. The new lineage must contain the old signing certificate and
// the nodes up until the node with signing certificate must be in the same order.
// Good example 1:
// old: A -> B -> C
// new: B -> C -> D
// Good example 2:
// old: A -> B -> C
// new: C
// Bad example 1:
// old: A -> B -> C
// new: A -> C
// Bad example 1:
// old: A -> B
// new: C -> B
if (lastOldCertIndexInNew >= 0) {
return newCertificatesArray.subList(0, lastOldCertIndexInNew+1).equals(
oldCertificatesArray.subList(
oldCertificates.size()-1-lastOldCertIndexInNew,
oldCertificatesArray.size()));
}
// The new lineage can be shorter than the old one only if the last certificate of the new
// lineage exists in the old lineage and has a rollback capability there.
// Good example:
// old: A -> B_withRollbackCapability -> C
// new: A -> B
// Bad example 1:
// old: A -> B -> C
// new: A -> B
// Bad example 2:
// old: A -> B_withRollbackCapability -> C
// new: A -> B -> D
return oldCertificates.subList(0, newCertificates.size()).equals(newCertificates)
&& oldLineage.getSignerCapabilities(
oldCertificates.get(newCertificates.size()-1)).hasRollback();
}
/**
* Representation of the capabilities the APK would like to grant to its old signing
* certificates. The {@code SigningCertificateLineage} provides two conceptual data structures.
* 1) proof of rotation - Evidence that other parties can trust an APK's current signing
* certificate if they trust an older one in this lineage
* 2) self-trust - certain capabilities may have been granted by an APK to other parties based
* on its own signing certificate. When it changes its signing certificate it may want to
* allow the other parties to retain those capabilities.
* {@code SignerCapabilties} provides a representation of the second structure.
*
* <p>Use {@link Builder} to obtain configuration instances.
*/
public static class SignerCapabilities {
private final int mFlags;
private final int mCallerConfiguredFlags;
private SignerCapabilities(int flags) {
this(flags, 0);
}
private SignerCapabilities(int flags, int callerConfiguredFlags) {
mFlags = flags;
mCallerConfiguredFlags = callerConfiguredFlags;
}
private int getFlags() {
return mFlags;
}
/**
* Returns {@code true} if the capabilities of this object match those of the provided
* object.
*/
@Override
public boolean equals(Object other) {
if (this == other) return true;
if (!(other instanceof SignerCapabilities)) return false;
return this.mFlags == ((SignerCapabilities) other).mFlags;
}
@Override
public int hashCode() {
return 31 * mFlags;
}
/**
* Returns {@code true} if this object has the installed data capability.
*/
public boolean hasInstalledData() {
return (mFlags & PAST_CERT_INSTALLED_DATA) != 0;
}
/**
* Returns {@code true} if this object has the shared UID capability.
*/
public boolean hasSharedUid() {
return (mFlags & PAST_CERT_SHARED_USER_ID) != 0;
}
/**
* Returns {@code true} if this object has the permission capability.
*/
public boolean hasPermission() {
return (mFlags & PAST_CERT_PERMISSION) != 0;
}
/**
* Returns {@code true} if this object has the rollback capability.
*/
public boolean hasRollback() {
return (mFlags & PAST_CERT_ROLLBACK) != 0;
}
/**
* Returns {@code true} if this object has the auth capability.
*/
public boolean hasAuth() {
return (mFlags & PAST_CERT_AUTH) != 0;
}
/**
* Builder of {@link SignerCapabilities} instances.
*/
public static class Builder {
private int mFlags;
private int mCallerConfiguredFlags;
/**
* Constructs a new {@code Builder}.
*/
public Builder() {
mFlags = calculateDefaultFlags();
}
/**
* Constructs a new {@code Builder} with the initial capabilities set to the provided
* flags.
*/
public Builder(int flags) {
mFlags = flags;
}
/**
* Set the {@code PAST_CERT_INSTALLED_DATA} flag in this capabilities object. This flag
* is used by the platform to determine if installed data associated with previous
* signing certificate should be trusted. In particular, this capability is required to
* perform signing certificate rotation during an upgrade on-device. Without it, the
* platform will not permit the app data from the old signing certificate to
* propagate to the new version. Typically, this flag should be set to enable signing
* certificate rotation, and may be unset later when the app developer is satisfied that
* their install base is as migrated as it will be.
*/
public Builder setInstalledData(boolean enabled) {
mCallerConfiguredFlags |= PAST_CERT_INSTALLED_DATA;
if (enabled) {
mFlags |= PAST_CERT_INSTALLED_DATA;
} else {
mFlags &= ~PAST_CERT_INSTALLED_DATA;
}
return this;
}
/**
* Set the {@code PAST_CERT_SHARED_USER_ID} flag in this capabilities object. This flag
* is used by the platform to determine if this app is willing to be sharedUid with
* other apps which are still signed with the associated signing certificate. This is
* useful in situations where sharedUserId apps would like to change their signing
* certificate, but can't guarantee the order of updates to those apps.
*/
public Builder setSharedUid(boolean enabled) {
mCallerConfiguredFlags |= PAST_CERT_SHARED_USER_ID;
if (enabled) {
mFlags |= PAST_CERT_SHARED_USER_ID;
} else {
mFlags &= ~PAST_CERT_SHARED_USER_ID;
}
return this;
}
/**
* Set the {@code PAST_CERT_PERMISSION} flag in this capabilities object. This flag
* is used by the platform to determine if this app is willing to grant SIGNATURE
* permissions to apps signed with the associated signing certificate. Without this
* capability, an application signed with the older certificate will not be granted the
* SIGNATURE permissions defined by this app. In addition, if multiple apps define the
* same SIGNATURE permission, the second one the platform sees will not be installable
* if this capability is not set and the signing certificates differ.
*/
public Builder setPermission(boolean enabled) {
mCallerConfiguredFlags |= PAST_CERT_PERMISSION;
if (enabled) {
mFlags |= PAST_CERT_PERMISSION;
} else {
mFlags &= ~PAST_CERT_PERMISSION;
}
return this;
}
/**
* Set the {@code PAST_CERT_ROLLBACK} flag in this capabilities object. This flag
* is used by the platform to determine if this app is willing to upgrade to a new
* version that is signed by one of its past signing certificates.
*
* <note> WARNING: this effectively removes any benefit of signing certificate changes,
* since a compromised key could retake control of an app even after change, and should
* only be used if there is a problem encountered when trying to ditch an older cert
* </note>
*/
public Builder setRollback(boolean enabled) {
mCallerConfiguredFlags |= PAST_CERT_ROLLBACK;
if (enabled) {
mFlags |= PAST_CERT_ROLLBACK;
} else {
mFlags &= ~PAST_CERT_ROLLBACK;
}
return this;
}
/**
* Set the {@code PAST_CERT_AUTH} flag in this capabilities object. This flag
* is used by the platform to determine whether or not privileged access based on
* authenticator module signing certificates should be granted.
*/
public Builder setAuth(boolean enabled) {
mCallerConfiguredFlags |= PAST_CERT_AUTH;
if (enabled) {
mFlags |= PAST_CERT_AUTH;
} else {
mFlags &= ~PAST_CERT_AUTH;
}
return this;
}
/**
* Applies the capabilities that were explicitly set in the provided capabilities object
* to this builder. Any values that were not set will not be applied to this builder
* to prevent unintentinoally setting a capability back to a default value.
*/
public Builder setCallerConfiguredCapabilities(SignerCapabilities capabilities) {
// The mCallerConfiguredFlags should have a bit set for each capability that was
// set by a caller. If a capability was explicitly set then the corresponding bit
// in mCallerConfiguredFlags should be set. This allows the provided capabilities
// to take effect for those set by the caller while those that were not set will
// be cleared by the bitwise and and the initial value for the builder will remain.
mFlags = (mFlags & ~capabilities.mCallerConfiguredFlags) |
(capabilities.mFlags & capabilities.mCallerConfiguredFlags);
return this;
}
/**
* Returns a new {@code SignerConfig} instance configured based on the configuration of
* this builder.
*/
public SignerCapabilities build() {
return new SignerCapabilities(mFlags, mCallerConfiguredFlags);
}
}
}
/**
* Configuration of a signer. Used to add a new entry to the {@link SigningCertificateLineage}
*
* <p>Use {@link Builder} to obtain configuration instances.
*/
public static class SignerConfig {
private final PrivateKey mPrivateKey;
private final X509Certificate mCertificate;
private SignerConfig(
PrivateKey privateKey,
X509Certificate certificate) {
mPrivateKey = privateKey;
mCertificate = certificate;
}
/**
* Returns the signing key of this signer.
*/
public PrivateKey getPrivateKey() {
return mPrivateKey;
}
/**
* Returns the certificate(s) of this signer. The first certificate's public key corresponds
* to this signer's private key.
*/
public X509Certificate getCertificate() {
return mCertificate;
}
/**
* Builder of {@link SignerConfig} instances.
*/
public static class Builder {
private final PrivateKey mPrivateKey;
private final X509Certificate mCertificate;
/**
* Constructs a new {@code Builder}.
*
* @param privateKey signing key
* @param certificate the X.509 certificate with a subject public key of the
* {@code privateKey}.
*/
public Builder(
PrivateKey privateKey,
X509Certificate certificate) {
mPrivateKey = privateKey;
mCertificate = certificate;
}
/**
* Returns a new {@code SignerConfig} instance configured based on the configuration of
* this builder.
*/
public SignerConfig build() {
return new SignerConfig(
mPrivateKey,
mCertificate);
}
}
}
/**
* Builder of {@link SigningCertificateLineage} instances.
*/
public static class Builder {
private final SignerConfig mOriginalSignerConfig;
private final SignerConfig mNewSignerConfig;
private SignerCapabilities mOriginalCapabilities;
private SignerCapabilities mNewCapabilities;
private int mMinSdkVersion;
/**
* Constructs a new {@code Builder}.
*
* @param originalSignerConfig first signer in this lineage, parent of the next
* @param newSignerConfig new signer in the lineage; the new signing key that the APK will
* use
*/
public Builder(
SignerConfig originalSignerConfig,
SignerConfig newSignerConfig) {
if (originalSignerConfig == null || newSignerConfig == null) {
throw new NullPointerException("Can't pass null SignerConfigs when constructing a "
+ "new SigningCertificateLineage");
}
mOriginalSignerConfig = originalSignerConfig;
mNewSignerConfig = newSignerConfig;
}
/**
* Constructs a new {@code Builder} that is intended to create a {@code
* SigningCertificateLineage} with a single signer in the signing history.
*
* @param originalSignerConfig first signer in this lineage
*/
public Builder(SignerConfig originalSignerConfig) {
if (originalSignerConfig == null) {
throw new NullPointerException("Can't pass null SignerConfigs when constructing a "
+ "new SigningCertificateLineage");
}
mOriginalSignerConfig = originalSignerConfig;
mNewSignerConfig = null;
}
/**
* Sets the minimum Android platform version (API Level) on which this lineage is expected
* to validate. It is possible that newer signers in the lineage may not be recognized on
* the given platform, but as long as an older signer is, the lineage can still be used to
* sign an APK for the given platform.
*
* <note> By default, this value is set to the value for the
* P release, since this structure was created for that release, and will also be set to
* that value if a smaller one is specified. </note>
*/
public Builder setMinSdkVersion(int minSdkVersion) {
mMinSdkVersion = minSdkVersion;
return this;
}
/**
* Sets capabilities to give {@code mOriginalSignerConfig}. These capabilities allow an
* older signing certificate to still be used in some situations on the platform even though
* the APK is now being signed by a newer signing certificate.
*/
public Builder setOriginalCapabilities(SignerCapabilities signerCapabilities) {
if (signerCapabilities == null) {
throw new NullPointerException("signerCapabilities == null");
}
mOriginalCapabilities = signerCapabilities;
return this;
}
/**
* Sets capabilities to give {@code mNewSignerConfig}. These capabilities allow an
* older signing certificate to still be used in some situations on the platform even though
* the APK is now being signed by a newer signing certificate. By default, the new signer
* will have all capabilities, so when first switching to a new signing certificate, these
* capabilities have no effect, but they will act as the default level of trust when moving
* to a new signing certificate.
*/
public Builder setNewCapabilities(SignerCapabilities signerCapabilities) {
if (signerCapabilities == null) {
throw new NullPointerException("signerCapabilities == null");
}
mNewCapabilities = signerCapabilities;
return this;
}
public SigningCertificateLineage build()
throws CertificateEncodingException, InvalidKeyException, NoSuchAlgorithmException,
SignatureException {
if (mMinSdkVersion < AndroidSdkVersion.P) {
mMinSdkVersion = AndroidSdkVersion.P;
}
if (mOriginalCapabilities == null) {
mOriginalCapabilities = new SignerCapabilities.Builder().build();
}
if (mNewSignerConfig == null) {
return createSigningLineage(mMinSdkVersion, mOriginalSignerConfig,
mOriginalCapabilities);
}
if (mNewCapabilities == null) {
mNewCapabilities = new SignerCapabilities.Builder().build();
}
return createSigningLineage(
mMinSdkVersion, mOriginalSignerConfig, mOriginalCapabilities,
mNewSignerConfig, mNewCapabilities);
}
}
}
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