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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.util.jar;
import android.util.apk.ApkSignatureSchemeV2Verifier;
import android.util.apk.ApkSignatureSchemeV3Verifier;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.jar.Attributes;
import java.util.jar.JarFile;
import sun.security.jca.Providers;
import sun.security.pkcs.PKCS7;
import sun.security.pkcs.SignerInfo;
/**
* Non-public class used by {@link JarFile} and {@link JarInputStream} to manage
* the verification of signed JARs. {@code JarFile} and {@code JarInputStream}
* objects are expected to have a {@code JarVerifier} instance member which
* can be used to carry out the tasks associated with verifying a signed JAR.
* These tasks would typically include:
*
* - verification of all signed signature files
*
- confirmation that all signed data was signed only by the party or parties
* specified in the signature block data
*
- verification that the contents of all signature files (i.e. {@code .SF}
* files) agree with the JAR entries information found in the JAR manifest.
*
*/
class StrictJarVerifier {
/**
* {@code .SF} file header section attribute indicating that the APK is signed not just with
* JAR signature scheme but also with APK Signature Scheme v2 or newer. This attribute
* facilitates v2 signature stripping detection.
*
* The attribute contains a comma-separated set of signature scheme IDs.
*/
private static final String SF_ATTRIBUTE_ANDROID_APK_SIGNED_NAME = "X-Android-APK-Signed";
/**
* List of accepted digest algorithms. This list is in order from most
* preferred to least preferred.
*/
private static final String[] DIGEST_ALGORITHMS = new String[] {
"SHA-512",
"SHA-384",
"SHA-256",
"SHA1",
};
private final String jarName;
private final StrictJarManifest manifest;
private final HashMap metaEntries;
private final int mainAttributesEnd;
private final boolean signatureSchemeRollbackProtectionsEnforced;
private final Hashtable> signatures =
new Hashtable>(5);
private final Hashtable certificates =
new Hashtable(5);
private final Hashtable verifiedEntries =
new Hashtable();
/**
* Stores and a hash and a message digest and verifies that massage digest
* matches the hash.
*/
static class VerifierEntry extends OutputStream {
private final String name;
private final MessageDigest digest;
private final byte[] hash;
private final Certificate[][] certChains;
private final Hashtable verifiedEntries;
VerifierEntry(String name, MessageDigest digest, byte[] hash,
Certificate[][] certChains, Hashtable verifedEntries) {
this.name = name;
this.digest = digest;
this.hash = hash;
this.certChains = certChains;
this.verifiedEntries = verifedEntries;
}
/**
* Updates a digest with one byte.
*/
@Override
public void write(int value) {
digest.update((byte) value);
}
/**
* Updates a digest with byte array.
*/
@Override
public void write(byte[] buf, int off, int nbytes) {
digest.update(buf, off, nbytes);
}
/**
* Verifies that the digests stored in the manifest match the decrypted
* digests from the .SF file. This indicates the validity of the
* signing, not the integrity of the file, as its digest must be
* calculated and verified when its contents are read.
*
* @throws SecurityException
* if the digest value stored in the manifest does not
* agree with the decrypted digest as recovered from the
* .SF file.
*/
void verify() {
byte[] d = digest.digest();
if (!verifyMessageDigest(d, hash)) {
throw invalidDigest(JarFile.MANIFEST_NAME, name, name);
}
verifiedEntries.put(name, certChains);
}
}
private static SecurityException invalidDigest(String signatureFile, String name,
String jarName) {
throw new SecurityException(signatureFile + " has invalid digest for " + name +
" in " + jarName);
}
private static SecurityException failedVerification(String jarName, String signatureFile) {
throw new SecurityException(jarName + " failed verification of " + signatureFile);
}
private static SecurityException failedVerification(String jarName, String signatureFile,
Throwable e) {
throw new SecurityException(jarName + " failed verification of " + signatureFile, e);
}
/**
* Constructs and returns a new instance of {@code JarVerifier}.
*
* @param name
* the name of the JAR file being verified.
*
* @param signatureSchemeRollbackProtectionsEnforced {@code true} to enforce protections against
* stripping newer signature schemes (e.g., APK Signature Scheme v2) from the file, or
* {@code false} to ignore any such protections.
*/
StrictJarVerifier(String name, StrictJarManifest manifest,
HashMap metaEntries, boolean signatureSchemeRollbackProtectionsEnforced) {
jarName = name;
this.manifest = manifest;
this.metaEntries = metaEntries;
this.mainAttributesEnd = manifest.getMainAttributesEnd();
this.signatureSchemeRollbackProtectionsEnforced =
signatureSchemeRollbackProtectionsEnforced;
}
/**
* Invoked for each new JAR entry read operation from the input
* stream. This method constructs and returns a new {@link VerifierEntry}
* which contains the certificates used to sign the entry and its hash value
* as specified in the JAR MANIFEST format.
*
* @param name
* the name of an entry in a JAR file which is not in the
* {@code META-INF} directory.
* @return a new instance of {@link VerifierEntry} which can be used by
* callers as an {@link OutputStream}.
*/
VerifierEntry initEntry(String name) {
// If no manifest is present by the time an entry is found,
// verification cannot occur. If no signature files have
// been found, do not verify.
if (manifest == null || signatures.isEmpty()) {
return null;
}
Attributes attributes = manifest.getAttributes(name);
// entry has no digest
if (attributes == null) {
return null;
}
ArrayList certChains = new ArrayList();
Iterator>> it = signatures.entrySet().iterator();
while (it.hasNext()) {
Map.Entry> entry = it.next();
HashMap hm = entry.getValue();
if (hm.get(name) != null) {
// Found an entry for entry name in .SF file
String signatureFile = entry.getKey();
Certificate[] certChain = certificates.get(signatureFile);
if (certChain != null) {
certChains.add(certChain);
}
}
}
// entry is not signed
if (certChains.isEmpty()) {
return null;
}
Certificate[][] certChainsArray = certChains.toArray(new Certificate[certChains.size()][]);
for (int i = 0; i < DIGEST_ALGORITHMS.length; i++) {
final String algorithm = DIGEST_ALGORITHMS[i];
final String hash = attributes.getValue(algorithm + "-Digest");
if (hash == null) {
continue;
}
byte[] hashBytes = hash.getBytes(StandardCharsets.ISO_8859_1);
try {
return new VerifierEntry(name, MessageDigest.getInstance(algorithm), hashBytes,
certChainsArray, verifiedEntries);
} catch (NoSuchAlgorithmException ignored) {
}
}
return null;
}
/**
* Add a new meta entry to the internal collection of data held on each JAR
* entry in the {@code META-INF} directory including the manifest
* file itself. Files associated with the signing of a JAR would also be
* added to this collection.
*
* @param name
* the name of the file located in the {@code META-INF}
* directory.
* @param buf
* the file bytes for the file called {@code name}.
* @see #removeMetaEntries()
*/
void addMetaEntry(String name, byte[] buf) {
metaEntries.put(name.toUpperCase(Locale.US), buf);
}
/**
* If the associated JAR file is signed, check on the validity of all of the
* known signatures.
*
* @return {@code true} if the associated JAR is signed and an internal
* check verifies the validity of the signature(s). {@code false} if
* the associated JAR file has no entries at all in its {@code
* META-INF} directory. This situation is indicative of an invalid
* JAR file.
*
* Will also return {@code true} if the JAR file is not
* signed.
* @throws SecurityException
* if the JAR file is signed and it is determined that a
* signature block file contains an invalid signature for the
* corresponding signature file.
*/
synchronized boolean readCertificates() {
if (metaEntries.isEmpty()) {
return false;
}
Iterator it = metaEntries.keySet().iterator();
while (it.hasNext()) {
String key = it.next();
if (key.endsWith(".DSA") || key.endsWith(".RSA") || key.endsWith(".EC")) {
verifyCertificate(key);
it.remove();
}
}
return true;
}
/**
* Verifies that the signature computed from {@code sfBytes} matches
* that specified in {@code blockBytes} (which is a PKCS7 block). Returns
* certificates listed in the PKCS7 block. Throws a {@code GeneralSecurityException}
* if something goes wrong during verification.
*/
static Certificate[] verifyBytes(byte[] blockBytes, byte[] sfBytes)
throws GeneralSecurityException {
Object obj = null;
try {
obj = Providers.startJarVerification();
PKCS7 block = new PKCS7(blockBytes);
SignerInfo[] verifiedSignerInfos = block.verify(sfBytes);
if ((verifiedSignerInfos == null) || (verifiedSignerInfos.length == 0)) {
throw new GeneralSecurityException(
"Failed to verify signature: no verified SignerInfos");
}
// Ignore any SignerInfo other than the first one, to be compatible with older Android
// platforms which have been doing this for years. See
// libcore/luni/src/main/java/org/apache/harmony/security/utils/JarUtils.java
// verifySignature method of older platforms.
SignerInfo verifiedSignerInfo = verifiedSignerInfos[0];
List verifiedSignerCertChain =
verifiedSignerInfo.getCertificateChain(block);
if (verifiedSignerCertChain == null) {
// Should never happen
throw new GeneralSecurityException(
"Failed to find verified SignerInfo certificate chain");
} else if (verifiedSignerCertChain.isEmpty()) {
// Should never happen
throw new GeneralSecurityException(
"Verified SignerInfo certificate chain is emtpy");
}
return verifiedSignerCertChain.toArray(
new X509Certificate[verifiedSignerCertChain.size()]);
} catch (IOException e) {
throw new GeneralSecurityException("IO exception verifying jar cert", e);
} finally {
Providers.stopJarVerification(obj);
}
}
/**
* @param certFile
*/
private void verifyCertificate(String certFile) {
// Found Digital Sig, .SF should already have been read
String signatureFile = certFile.substring(0, certFile.lastIndexOf('.')) + ".SF";
byte[] sfBytes = metaEntries.get(signatureFile);
if (sfBytes == null) {
return;
}
byte[] manifestBytes = metaEntries.get(JarFile.MANIFEST_NAME);
// Manifest entry is required for any verifications.
if (manifestBytes == null) {
return;
}
byte[] sBlockBytes = metaEntries.get(certFile);
try {
Certificate[] signerCertChain = verifyBytes(sBlockBytes, sfBytes);
if (signerCertChain != null) {
certificates.put(signatureFile, signerCertChain);
}
} catch (GeneralSecurityException e) {
throw failedVerification(jarName, signatureFile, e);
}
// Verify manifest hash in .sf file
Attributes attributes = new Attributes();
HashMap entries = new HashMap();
try {
StrictJarManifestReader im = new StrictJarManifestReader(sfBytes, attributes);
im.readEntries(entries, null);
} catch (IOException e) {
return;
}
// If requested, check whether a newer APK Signature Scheme signature was stripped.
if (signatureSchemeRollbackProtectionsEnforced) {
String apkSignatureSchemeIdList =
attributes.getValue(SF_ATTRIBUTE_ANDROID_APK_SIGNED_NAME);
if (apkSignatureSchemeIdList != null) {
// This field contains a comma-separated list of APK signature scheme IDs which
// were used to sign this APK. If an ID is known to us, it means signatures of that
// scheme were stripped from the APK because otherwise we wouldn't have fallen back
// to verifying the APK using the JAR signature scheme.
boolean v2SignatureGenerated = false;
boolean v3SignatureGenerated = false;
StringTokenizer tokenizer = new StringTokenizer(apkSignatureSchemeIdList, ",");
while (tokenizer.hasMoreTokens()) {
String idText = tokenizer.nextToken().trim();
if (idText.isEmpty()) {
continue;
}
int id;
try {
id = Integer.parseInt(idText);
} catch (Exception ignored) {
continue;
}
if (id == ApkSignatureSchemeV2Verifier.SF_ATTRIBUTE_ANDROID_APK_SIGNED_ID) {
// This APK was supposed to be signed with APK Signature Scheme v2 but no
// such signature was found.
v2SignatureGenerated = true;
break;
}
if (id == ApkSignatureSchemeV3Verifier.SF_ATTRIBUTE_ANDROID_APK_SIGNED_ID) {
// This APK was supposed to be signed with APK Signature Scheme v3 but no
// such signature was found.
v3SignatureGenerated = true;
break;
}
}
if (v2SignatureGenerated) {
throw new SecurityException(signatureFile + " indicates " + jarName
+ " is signed using APK Signature Scheme v2, but no such signature was"
+ " found. Signature stripped?");
}
if (v3SignatureGenerated) {
throw new SecurityException(signatureFile + " indicates " + jarName
+ " is signed using APK Signature Scheme v3, but no such signature was"
+ " found. Signature stripped?");
}
}
}
// Do we actually have any signatures to look at?
if (attributes.get(Attributes.Name.SIGNATURE_VERSION) == null) {
return;
}
boolean createdBySigntool = false;
String createdBy = attributes.getValue("Created-By");
if (createdBy != null) {
createdBySigntool = createdBy.indexOf("signtool") != -1;
}
// Use .SF to verify the mainAttributes of the manifest
// If there is no -Digest-Manifest-Main-Attributes entry in .SF
// file, such as those created before java 1.5, then we ignore
// such verification.
if (mainAttributesEnd > 0 && !createdBySigntool) {
String digestAttribute = "-Digest-Manifest-Main-Attributes";
if (!verify(attributes, digestAttribute, manifestBytes, 0, mainAttributesEnd, false, true)) {
throw failedVerification(jarName, signatureFile);
}
}
// Use .SF to verify the whole manifest.
String digestAttribute = createdBySigntool ? "-Digest" : "-Digest-Manifest";
if (!verify(attributes, digestAttribute, manifestBytes, 0, manifestBytes.length, false, false)) {
Iterator> it = entries.entrySet().iterator();
while (it.hasNext()) {
Map.Entry entry = it.next();
StrictJarManifest.Chunk chunk = manifest.getChunk(entry.getKey());
if (chunk == null) {
return;
}
if (!verify(entry.getValue(), "-Digest", manifestBytes,
chunk.start, chunk.end, createdBySigntool, false)) {
throw invalidDigest(signatureFile, entry.getKey(), jarName);
}
}
}
metaEntries.put(signatureFile, null);
signatures.put(signatureFile, entries);
}
/**
* Returns a boolean indication of whether or not the
* associated jar file is signed.
*
* @return {@code true} if the JAR is signed, {@code false}
* otherwise.
*/
boolean isSignedJar() {
return certificates.size() > 0;
}
private boolean verify(Attributes attributes, String entry, byte[] data,
int start, int end, boolean ignoreSecondEndline, boolean ignorable) {
for (int i = 0; i < DIGEST_ALGORITHMS.length; i++) {
String algorithm = DIGEST_ALGORITHMS[i];
String hash = attributes.getValue(algorithm + entry);
if (hash == null) {
continue;
}
MessageDigest md;
try {
md = MessageDigest.getInstance(algorithm);
} catch (NoSuchAlgorithmException e) {
continue;
}
if (ignoreSecondEndline && data[end - 1] == '\n' && data[end - 2] == '\n') {
md.update(data, start, end - 1 - start);
} else {
md.update(data, start, end - start);
}
byte[] b = md.digest();
byte[] encodedHashBytes = hash.getBytes(StandardCharsets.ISO_8859_1);
return verifyMessageDigest(b, encodedHashBytes);
}
return ignorable;
}
private static boolean verifyMessageDigest(byte[] expected, byte[] encodedActual) {
byte[] actual;
try {
actual = java.util.Base64.getDecoder().decode(encodedActual);
} catch (IllegalArgumentException e) {
return false;
}
return MessageDigest.isEqual(expected, actual);
}
/**
* Returns all of the {@link java.security.cert.Certificate} chains that
* were used to verify the signature on the JAR entry called
* {@code name}. Callers must not modify the returned arrays.
*
* @param name
* the name of a JAR entry.
* @return an array of {@link java.security.cert.Certificate} chains.
*/
Certificate[][] getCertificateChains(String name) {
return verifiedEntries.get(name);
}
/**
* Remove all entries from the internal collection of data held about each
* JAR entry in the {@code META-INF} directory.
*/
void removeMetaEntries() {
metaEntries.clear();
}
}