Magisk/crypto/src/main/java/com/topjohnwu/crypto/SignBoot.java

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2017-12-04 08:16:41 +01:00
package com.topjohnwu.crypto;
import org.bouncycastle.asn1.ASN1Encodable;
import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.ASN1Integer;
import org.bouncycastle.asn1.ASN1Object;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.DEROctetString;
import org.bouncycastle.asn1.DERPrintableString;
import org.bouncycastle.asn1.DERSequence;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Security;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.Arrays;
public class SignBoot {
static {
Security.addProvider(new BouncyCastleProvider());
}
public static boolean doSignature(String target, InputStream imgIn, OutputStream imgOut,
InputStream keyIn, InputStream certIn) {
try {
ByteArrayStream bas = new ByteArrayStream();
bas.readFrom(imgIn);
byte[] image = bas.toByteArray();
bas.close();
int signableSize = getSignableImageSize(image);
if (signableSize < image.length) {
System.err.println("NOTE: truncating input from " +
image.length + " to " + signableSize + " bytes");
image = Arrays.copyOf(image, signableSize);
} else if (signableSize > image.length) {
throw new IllegalArgumentException("Invalid image: too short, expected " +
signableSize + " bytes");
}
BootSignature bootsig = new BootSignature(target, image.length);
X509Certificate cert = CryptoUtils.readPublicKey(certIn);
bootsig.setCertificate(cert);
PrivateKey key = CryptoUtils.readPrivateKey(keyIn);
bootsig.setSignature(bootsig.sign(image, key),
CryptoUtils.getSignatureAlgorithmIdentifier(key));
byte[] encoded_bootsig = bootsig.getEncoded();
imgOut.write(image);
imgOut.write(encoded_bootsig);
imgOut.flush();
return true;
} catch (Exception e) {
e.printStackTrace(System.err);
return false;
}
}
public static boolean verifySignature(InputStream imgIn, InputStream certPath) {
try {
ByteArrayStream bas = new ByteArrayStream();
bas.readFrom(imgIn);
byte[] image = bas.toByteArray();
bas.close();
int signableSize = getSignableImageSize(image);
if (signableSize >= image.length) {
System.err.println("Invalid image: not signed");
return false;
}
byte[] signature = Arrays.copyOfRange(image, signableSize, image.length);
BootSignature bootsig = new BootSignature(signature);
if (certPath != null) {
bootsig.setCertificate(CryptoUtils.readPublicKey(certPath));
}
if (bootsig.verify(Arrays.copyOf(image, signableSize))) {
System.err.println("Signature is VALID");
return true;
} else {
System.err.println("Signature is INVALID");
}
} catch (Exception e) {
e.printStackTrace(System.err);
System.err.println("Invalid image: not signed");
}
return false;
}
public static int getSignableImageSize(byte[] data) throws Exception {
if (!Arrays.equals(Arrays.copyOfRange(data, 0, 8),
"ANDROID!".getBytes("US-ASCII"))) {
throw new IllegalArgumentException("Invalid image header: missing magic");
}
ByteBuffer image = ByteBuffer.wrap(data);
image.order(ByteOrder.LITTLE_ENDIAN);
image.getLong(); // magic
int kernelSize = image.getInt();
image.getInt(); // kernel_addr
int ramdskSize = image.getInt();
image.getInt(); // ramdisk_addr
int secondSize = image.getInt();
image.getLong(); // second_addr + tags_addr
int pageSize = image.getInt();
int length = pageSize // include the page aligned image header
+ ((kernelSize + pageSize - 1) / pageSize) * pageSize
+ ((ramdskSize + pageSize - 1) / pageSize) * pageSize
+ ((secondSize + pageSize - 1) / pageSize) * pageSize;
length = ((length + pageSize - 1) / pageSize) * pageSize;
if (length <= 0) {
throw new IllegalArgumentException("Invalid image header: invalid length");
}
return length;
}
static class BootSignature extends ASN1Object {
private ASN1Integer formatVersion;
private ASN1Encodable certificate;
private AlgorithmIdentifier algorithmIdentifier;
private DERPrintableString target;
private ASN1Integer length;
private DEROctetString signature;
private PublicKey publicKey;
private static final int FORMAT_VERSION = 1;
/**
* Initializes the object for signing an image file
* @param target Target name, included in the signed data
* @param length Length of the image, included in the signed data
*/
public BootSignature(String target, int length) {
this.formatVersion = new ASN1Integer(FORMAT_VERSION);
this.target = new DERPrintableString(target);
this.length = new ASN1Integer(length);
}
/**
* Initializes the object for verifying a signed image file
* @param signature Signature footer
*/
public BootSignature(byte[] signature)
throws Exception {
ASN1InputStream stream = new ASN1InputStream(signature);
ASN1Sequence sequence = (ASN1Sequence) stream.readObject();
formatVersion = (ASN1Integer) sequence.getObjectAt(0);
if (formatVersion.getValue().intValue() != FORMAT_VERSION) {
throw new IllegalArgumentException("Unsupported format version");
}
certificate = sequence.getObjectAt(1);
byte[] encoded = ((ASN1Object) certificate).getEncoded();
ByteArrayInputStream bis = new ByteArrayInputStream(encoded);
CertificateFactory cf = CertificateFactory.getInstance("X.509");
X509Certificate c = (X509Certificate) cf.generateCertificate(bis);
publicKey = c.getPublicKey();
ASN1Sequence algId = (ASN1Sequence) sequence.getObjectAt(2);
algorithmIdentifier = new AlgorithmIdentifier(
(ASN1ObjectIdentifier) algId.getObjectAt(0));
ASN1Sequence attrs = (ASN1Sequence) sequence.getObjectAt(3);
target = (DERPrintableString) attrs.getObjectAt(0);
length = (ASN1Integer) attrs.getObjectAt(1);
this.signature = (DEROctetString) sequence.getObjectAt(4);
}
public ASN1Object getAuthenticatedAttributes() {
ASN1EncodableVector attrs = new ASN1EncodableVector();
attrs.add(target);
attrs.add(length);
return new DERSequence(attrs);
}
public byte[] getEncodedAuthenticatedAttributes() throws IOException {
return getAuthenticatedAttributes().getEncoded();
}
public void setSignature(byte[] sig, AlgorithmIdentifier algId) {
algorithmIdentifier = algId;
signature = new DEROctetString(sig);
}
public void setCertificate(X509Certificate cert)
throws Exception, IOException, CertificateEncodingException {
ASN1InputStream s = new ASN1InputStream(cert.getEncoded());
certificate = s.readObject();
publicKey = cert.getPublicKey();
}
public byte[] generateSignableImage(byte[] image) throws IOException {
byte[] attrs = getEncodedAuthenticatedAttributes();
byte[] signable = Arrays.copyOf(image, image.length + attrs.length);
for (int i=0; i < attrs.length; i++) {
signable[i+image.length] = attrs[i];
}
return signable;
}
public byte[] sign(byte[] image, PrivateKey key) throws Exception {
byte[] signable = generateSignableImage(image);
return CryptoUtils.sign(key, signable);
}
public boolean verify(byte[] image) throws Exception {
if (length.getValue().intValue() != image.length) {
throw new IllegalArgumentException("Invalid image length");
}
byte[] signable = generateSignableImage(image);
return CryptoUtils.verify(publicKey, signable, signature.getOctets(),
algorithmIdentifier);
}
@Override
public ASN1Primitive toASN1Primitive() {
ASN1EncodableVector v = new ASN1EncodableVector();
v.add(formatVersion);
v.add(certificate);
v.add(algorithmIdentifier);
v.add(getAuthenticatedAttributes());
v.add(signature);
return new DERSequence(v);
}
}
}