/*
* Copyright (C) 2008 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.content.pm;
import android.os.Parcel;
import android.os.Parcelable;
import com.android.internal.util.ArrayUtils;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.security.PublicKey;
import java.security.cert.Certificate;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.Arrays;
/**
* Opaque, immutable representation of a signing certificate associated with an
* application package.
* <p>
* This class name is slightly misleading, since it's not actually a signature.
*/
public class Signature implements Parcelable {
private final byte[] mSignature;
private int mHashCode;
private boolean mHaveHashCode;
private SoftReference<String> mStringRef;
private Certificate[] mCertificateChain;
/**
* Create Signature from an existing raw byte array.
*/
public Signature(byte[] signature) {
mSignature = signature.clone();
mCertificateChain = null;
}
/**
* Create signature from a certificate chain. Used for backward
* compatibility.
*
* @throws CertificateEncodingException
* @hide
*/
public Signature(Certificate[] certificateChain) throws CertificateEncodingException {
mSignature = certificateChain[0].getEncoded();
if (certificateChain.length > 1) {
mCertificateChain = Arrays.copyOfRange(certificateChain, 1, certificateChain.length);
}
}
private static final int parseHexDigit(int nibble) {
if ('0' <= nibble && nibble <= '9') {
return nibble - '0';
} else if ('a' <= nibble && nibble <= 'f') {
return nibble - 'a' + 10;
} else if ('A' <= nibble && nibble <= 'F') {
return nibble - 'A' + 10;
} else {
throw new IllegalArgumentException("Invalid character " + nibble + " in hex string");
}
}
/**
* Create Signature from a text representation previously returned by
* {@link #toChars} or {@link #toCharsString()}. Signatures are expected to
* be a hex-encoded ASCII string.
*
* @param text hex-encoded string representing the signature
* @throws IllegalArgumentException when signature is odd-length
*/
public Signature(String text) {
final byte[] input = text.getBytes();
final int N = input.length;
if (N % 2 != 0) {
throw new IllegalArgumentException("text size " + N + " is not even");
}
final byte[] sig = new byte[N / 2];
int sigIndex = 0;
for (int i = 0; i < N;) {
final int hi = parseHexDigit(input[i++]);
final int lo = parseHexDigit(input[i++]);
sig[sigIndex++] = (byte) ((hi << 4) | lo);
}
mSignature = sig;
}
/**
* Encode the Signature as ASCII text.
*/
public char[] toChars() {
return toChars(null, null);
}
/**
* Encode the Signature as ASCII text in to an existing array.
*
* @param existingArray Existing char array or null.
* @param outLen Output parameter for the number of characters written in
* to the array.
* @return Returns either <var>existingArray</var> if it was large enough
* to hold the ASCII representation, or a newly created char[] array if
* needed.
*/
public char[] toChars(char[] existingArray, int[] outLen) {
byte[] sig = mSignature;
final int N = sig.length;
final int N2 = N*2;
char[] text = existingArray == null || N2 > existingArray.length
? new char[N2] : existingArray;
for (int j=0; j<N; j++) {
byte v = sig[j];
int d = (v>>4)&0xf;
text[j*2] = (char)(d >= 10 ? ('a' + d - 10) : ('0' + d));
d = v&0xf;
text[j*2+1] = (char)(d >= 10 ? ('a' + d - 10) : ('0' + d));
}
if (outLen != null) outLen[0] = N;
return text;
}
/**
* Return the result of {@link #toChars()} as a String.
*/
public String toCharsString() {
String str = mStringRef == null ? null : mStringRef.get();
if (str != null) {
return str;
}
str = new String(toChars());
mStringRef = new SoftReference<String>(str);
return str;
}
/**
* @return the contents of this signature as a byte array.
*/
public byte[] toByteArray() {
byte[] bytes = new byte[mSignature.length];
System.arraycopy(mSignature, 0, bytes, 0, mSignature.length);
return bytes;
}
/**
* Returns the public key for this signature.
*
* @throws CertificateException when Signature isn't a valid X.509
* certificate; shouldn't happen.
* @hide
*/
public PublicKey getPublicKey() throws CertificateException {
final CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
final ByteArrayInputStream bais = new ByteArrayInputStream(mSignature);
final Certificate cert = certFactory.generateCertificate(bais);
return cert.getPublicKey();
}
/**
* Used for compatibility code that needs to check the certificate chain
* during upgrades.
*
* @throws CertificateEncodingException
* @hide
*/
public Signature[] getChainSignatures() throws CertificateEncodingException {
if (mCertificateChain == null) {
return new Signature[] { this };
}
Signature[] chain = new Signature[1 + mCertificateChain.length];
chain[0] = this;
int i = 1;
for (Certificate c : mCertificateChain) {
chain[i++] = new Signature(c.getEncoded());
}
return chain;
}
@Override
public boolean equals(Object obj) {
try {
if (obj != null) {
Signature other = (Signature)obj;
return this == other || Arrays.equals(mSignature, other.mSignature);
}
} catch (ClassCastException e) {
}
return false;
}
@Override
public int hashCode() {
if (mHaveHashCode) {
return mHashCode;
}
mHashCode = Arrays.hashCode(mSignature);
mHaveHashCode = true;
return mHashCode;
}
public int describeContents() {
return 0;
}
public void writeToParcel(Parcel dest, int parcelableFlags) {
dest.writeByteArray(mSignature);
}
public static final Parcelable.Creator<Signature> CREATOR
= new Parcelable.Creator<Signature>() {
public Signature createFromParcel(Parcel source) {
return new Signature(source);
}
public Signature[] newArray(int size) {
return new Signature[size];
}
};
private Signature(Parcel source) {
mSignature = source.createByteArray();
}
/**
* Test if given {@link Signature} sets are exactly equal.
*
* @hide
*/
public static boolean areExactMatch(Signature[] a, Signature[] b) {
return (a.length == b.length) && ArrayUtils.containsAll(a, b)
&& ArrayUtils.containsAll(b, a);
}
/**
* Test if given {@link Signature} sets are effectively equal. In rare
* cases, certificates can have slightly malformed encoding which causes
* exact-byte checks to fail.
* <p>
* To identify effective equality, we bounce the certificates through an
* decode/encode pass before doing the exact-byte check. To reduce attack
* surface area, we only allow a byte size delta of a few bytes.
*
* @throws CertificateException if the before/after length differs
* substantially, usually a signal of something fishy going on.
* @hide
*/
public static boolean areEffectiveMatch(Signature[] a, Signature[] b)
throws CertificateException {
final CertificateFactory cf = CertificateFactory.getInstance("X.509");
final Signature[] aPrime = new Signature[a.length];
for (int i = 0; i < a.length; i++) {
aPrime[i] = bounce(cf, a[i]);
}
final Signature[] bPrime = new Signature[b.length];
for (int i = 0; i < b.length; i++) {
bPrime[i] = bounce(cf, b[i]);
}
return areExactMatch(aPrime, bPrime);
}
/**
* Bounce the given {@link Signature} through a decode/encode cycle.
*
* @throws CertificateException if the before/after length differs
* substantially, usually a signal of something fishy going on.
* @hide
*/
public static Signature bounce(CertificateFactory cf, Signature s) throws CertificateException {
final InputStream is = new ByteArrayInputStream(s.mSignature);
final X509Certificate cert = (X509Certificate) cf.generateCertificate(is);
final Signature sPrime = new Signature(cert.getEncoded());
if (Math.abs(sPrime.mSignature.length - s.mSignature.length) > 2) {
throw new CertificateException("Bounced cert length looks fishy; before "
+ s.mSignature.length + ", after " + sPrime.mSignature.length);
}
return sPrime;
}
}
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