/*
* Copyright (C) 2017 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.internal.asn1;
import com.android.apksig.internal.asn1.ber.BerEncoding;
import java.io.ByteArrayOutputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* Encoder of ASN.1 structures into DER-encoded form.
*
* <p>Structure is described to the encoder by providing a class annotated with {@link Asn1Class},
* containing fields annotated with {@link Asn1Field}.
*/
public final class Asn1DerEncoder {
private Asn1DerEncoder() {}
/**
* Returns the DER-encoded form of the provided ASN.1 structure.
*
* @param container container to be encoded. The container's class must meet the following
* requirements:
* <ul>
* <li>The class must be annotated with {@link Asn1Class}.</li>
* <li>Member fields of the class which are to be encoded must be annotated with
* {@link Asn1Field} and be public.</li>
* </ul>
*
* @throws Asn1EncodingException if the input could not be encoded
*/
public static byte[] encode(Object container) throws Asn1EncodingException {
Class<?> containerClass = container.getClass();
Asn1Class containerAnnotation = containerClass.getDeclaredAnnotation(Asn1Class.class);
if (containerAnnotation == null) {
throw new Asn1EncodingException(
containerClass.getName() + " not annotated with " + Asn1Class.class.getName());
}
Asn1Type containerType = containerAnnotation.type();
switch (containerType) {
case CHOICE:
return toChoice(container);
case SEQUENCE:
return toSequence(container);
case UNENCODED_CONTAINER:
return toSequence(container, true);
default:
throw new Asn1EncodingException("Unsupported container type: " + containerType);
}
}
private static byte[] toChoice(Object container) throws Asn1EncodingException {
Class<?> containerClass = container.getClass();
List<AnnotatedField> fields = getAnnotatedFields(container);
if (fields.isEmpty()) {
throw new Asn1EncodingException(
"No fields annotated with " + Asn1Field.class.getName()
+ " in CHOICE class " + containerClass.getName());
}
AnnotatedField resultField = null;
for (AnnotatedField field : fields) {
Object fieldValue = getMemberFieldValue(container, field.getField());
if (fieldValue != null) {
if (resultField != null) {
throw new Asn1EncodingException(
"Multiple non-null fields in CHOICE class " + containerClass.getName()
+ ": " + resultField.getField().getName()
+ ", " + field.getField().getName());
}
resultField = field;
}
}
if (resultField == null) {
throw new Asn1EncodingException(
"No non-null fields in CHOICE class " + containerClass.getName());
}
return resultField.toDer();
}
private static byte[] toSequence(Object container) throws Asn1EncodingException {
return toSequence(container, false);
}
private static byte[] toSequence(Object container, boolean omitTag)
throws Asn1EncodingException {
Class<?> containerClass = container.getClass();
List<AnnotatedField> fields = getAnnotatedFields(container);
Collections.sort(
fields, (f1, f2) -> f1.getAnnotation().index() - f2.getAnnotation().index());
if (fields.size() > 1) {
AnnotatedField lastField = null;
for (AnnotatedField field : fields) {
if ((lastField != null)
&& (lastField.getAnnotation().index() == field.getAnnotation().index())) {
throw new Asn1EncodingException(
"Fields have the same index: " + containerClass.getName()
+ "." + lastField.getField().getName()
+ " and ." + field.getField().getName());
}
lastField = field;
}
}
List<byte[]> serializedFields = new ArrayList<>(fields.size());
int contentLen = 0;
for (AnnotatedField field : fields) {
byte[] serializedField;
try {
serializedField = field.toDer();
} catch (Asn1EncodingException e) {
throw new Asn1EncodingException(
"Failed to encode " + containerClass.getName()
+ "." + field.getField().getName(),
e);
}
if (serializedField != null) {
serializedFields.add(serializedField);
contentLen += serializedField.length;
}
}
if (omitTag) {
byte[] unencodedResult = new byte[contentLen];
int index = 0;
for (byte[] serializedField : serializedFields) {
System.arraycopy(serializedField, 0, unencodedResult, index, serializedField.length);
index += serializedField.length;
}
return unencodedResult;
} else {
return createTag(
BerEncoding.TAG_CLASS_UNIVERSAL, true, BerEncoding.TAG_NUMBER_SEQUENCE,
serializedFields.toArray(new byte[0][]));
}
}
private static byte[] toSetOf(Collection<?> values, Asn1Type elementType) throws Asn1EncodingException {
return toSequenceOrSetOf(values, elementType, true);
}
private static byte[] toSequenceOf(Collection<?> values, Asn1Type elementType) throws Asn1EncodingException {
return toSequenceOrSetOf(values, elementType, false);
}
private static byte[] toSequenceOrSetOf(Collection<?> values, Asn1Type elementType, boolean toSet)
throws Asn1EncodingException {
List<byte[]> serializedValues = new ArrayList<>(values.size());
for (Object value : values) {
serializedValues.add(JavaToDerConverter.toDer(value, elementType, null));
}
int tagNumber;
if (toSet) {
if (serializedValues.size() > 1) {
Collections.sort(serializedValues, ByteArrayLexicographicComparator.INSTANCE);
}
tagNumber = BerEncoding.TAG_NUMBER_SET;
} else {
tagNumber = BerEncoding.TAG_NUMBER_SEQUENCE;
}
return createTag(
BerEncoding.TAG_CLASS_UNIVERSAL, true, tagNumber,
serializedValues.toArray(new byte[0][]));
}
/**
* Compares two bytes arrays based on their lexicographic order. Corresponding elements of the
* two arrays are compared in ascending order. Elements at out of range indices are assumed to
* be smaller than the smallest possible value for an element.
*/
private static class ByteArrayLexicographicComparator implements Comparator<byte[]> {
private static final ByteArrayLexicographicComparator INSTANCE =
new ByteArrayLexicographicComparator();
@Override
public int compare(byte[] arr1, byte[] arr2) {
int commonLength = Math.min(arr1.length, arr2.length);
for (int i = 0; i < commonLength; i++) {
int diff = (arr1[i] & 0xff) - (arr2[i] & 0xff);
if (diff != 0) {
return diff;
}
}
return arr1.length - arr2.length;
}
}
private static List<AnnotatedField> getAnnotatedFields(Object container)
throws Asn1EncodingException {
Class<?> containerClass = container.getClass();
Field[] declaredFields = containerClass.getDeclaredFields();
List<AnnotatedField> result = new ArrayList<>(declaredFields.length);
for (Field field : declaredFields) {
Asn1Field annotation = field.getDeclaredAnnotation(Asn1Field.class);
if (annotation == null) {
continue;
}
if (Modifier.isStatic(field.getModifiers())) {
throw new Asn1EncodingException(
Asn1Field.class.getName() + " used on a static field: "
+ containerClass.getName() + "." + field.getName());
}
AnnotatedField annotatedField;
try {
annotatedField = new AnnotatedField(container, field, annotation);
} catch (Asn1EncodingException e) {
throw new Asn1EncodingException(
"Invalid ASN.1 annotation on "
+ containerClass.getName() + "." + field.getName(),
e);
}
result.add(annotatedField);
}
return result;
}
private static byte[] toInteger(int value) {
return toInteger((long) value);
}
private static byte[] toInteger(long value) {
return toInteger(BigInteger.valueOf(value));
}
private static byte[] toInteger(BigInteger value) {
return createTag(
BerEncoding.TAG_CLASS_UNIVERSAL, false, BerEncoding.TAG_NUMBER_INTEGER,
value.toByteArray());
}
private static byte[] toBoolean(boolean value) {
// A boolean should be encoded in a single byte with a value of 0 for false and any non-zero
// value for true.
byte[] result = new byte[1];
if (value == false) {
result[0] = 0;
} else {
result[0] = 1;
}
return createTag(BerEncoding.TAG_CLASS_UNIVERSAL, false, BerEncoding.TAG_NUMBER_BOOLEAN, result);
}
private static byte[] toOid(String oid) throws Asn1EncodingException {
ByteArrayOutputStream encodedValue = new ByteArrayOutputStream();
String[] nodes = oid.split("\\.");
if (nodes.length < 2) {
throw new Asn1EncodingException(
"OBJECT IDENTIFIER must contain at least two nodes: " + oid);
}
int firstNode;
try {
firstNode = Integer.parseInt(nodes[0]);
} catch (NumberFormatException e) {
throw new Asn1EncodingException("Node #1 not numeric: " + nodes[0]);
}
if ((firstNode > 6) || (firstNode < 0)) {
throw new Asn1EncodingException("Invalid value for node #1: " + firstNode);
}
int secondNode;
try {
secondNode = Integer.parseInt(nodes[1]);
} catch (NumberFormatException e) {
throw new Asn1EncodingException("Node #2 not numeric: " + nodes[1]);
}
if ((secondNode >= 40) || (secondNode < 0)) {
throw new Asn1EncodingException("Invalid value for node #2: " + secondNode);
}
int firstByte = firstNode * 40 + secondNode;
if (firstByte > 0xff) {
throw new Asn1EncodingException(
"First two nodes out of range: " + firstNode + "." + secondNode);
}
encodedValue.write(firstByte);
for (int i = 2; i < nodes.length; i++) {
String nodeString = nodes[i];
int node;
try {
node = Integer.parseInt(nodeString);
} catch (NumberFormatException e) {
throw new Asn1EncodingException("Node #" + (i + 1) + " not numeric: " + nodeString);
}
if (node < 0) {
throw new Asn1EncodingException("Invalid value for node #" + (i + 1) + ": " + node);
}
if (node <= 0x7f) {
encodedValue.write(node);
continue;
}
if (node < 1 << 14) {
encodedValue.write(0x80 | (node >> 7));
encodedValue.write(node & 0x7f);
continue;
}
if (node < 1 << 21) {
encodedValue.write(0x80 | (node >> 14));
encodedValue.write(0x80 | ((node >> 7) & 0x7f));
encodedValue.write(node & 0x7f);
continue;
}
throw new Asn1EncodingException("Node #" + (i + 1) + " too large: " + node);
}
return createTag(
BerEncoding.TAG_CLASS_UNIVERSAL, false, BerEncoding.TAG_NUMBER_OBJECT_IDENTIFIER,
encodedValue.toByteArray());
}
private static Object getMemberFieldValue(Object obj, Field field)
throws Asn1EncodingException {
try {
return field.get(obj);
} catch (ReflectiveOperationException e) {
throw new Asn1EncodingException(
"Failed to read " + obj.getClass().getName() + "." + field.getName(), e);
}
}
private static final class AnnotatedField {
private final Field mField;
private final Object mObject;
private final Asn1Field mAnnotation;
private final Asn1Type mDataType;
private final Asn1Type mElementDataType;
private final Asn1TagClass mTagClass;
private final int mDerTagClass;
private final int mDerTagNumber;
private final Asn1Tagging mTagging;
private final boolean mOptional;
public AnnotatedField(Object obj, Field field, Asn1Field annotation)
throws Asn1EncodingException {
mObject = obj;
mField = field;
mAnnotation = annotation;
mDataType = annotation.type();
mElementDataType = annotation.elementType();
Asn1TagClass tagClass = annotation.cls();
if (tagClass == Asn1TagClass.AUTOMATIC) {
if (annotation.tagNumber() != -1) {
tagClass = Asn1TagClass.CONTEXT_SPECIFIC;
} else {
tagClass = Asn1TagClass.UNIVERSAL;
}
}
mTagClass = tagClass;
mDerTagClass = BerEncoding.getTagClass(mTagClass);
int tagNumber;
if (annotation.tagNumber() != -1) {
tagNumber = annotation.tagNumber();
} else if ((mDataType == Asn1Type.CHOICE) || (mDataType == Asn1Type.ANY)) {
tagNumber = -1;
} else {
tagNumber = BerEncoding.getTagNumber(mDataType);
}
mDerTagNumber = tagNumber;
mTagging = annotation.tagging();
if (((mTagging == Asn1Tagging.EXPLICIT) || (mTagging == Asn1Tagging.IMPLICIT))
&& (annotation.tagNumber() == -1)) {
throw new Asn1EncodingException(
"Tag number must be specified when tagging mode is " + mTagging);
}
mOptional = annotation.optional();
}
public Field getField() {
return mField;
}
public Asn1Field getAnnotation() {
return mAnnotation;
}
public byte[] toDer() throws Asn1EncodingException {
Object fieldValue = getMemberFieldValue(mObject, mField);
if (fieldValue == null) {
if (mOptional) {
return null;
}
throw new Asn1EncodingException("Required field not set");
}
byte[] encoded = JavaToDerConverter.toDer(fieldValue, mDataType, mElementDataType);
switch (mTagging) {
case NORMAL:
return encoded;
case EXPLICIT:
return createTag(mDerTagClass, true, mDerTagNumber, encoded);
case IMPLICIT:
int originalTagNumber = BerEncoding.getTagNumber(encoded[0]);
if (originalTagNumber == 0x1f) {
throw new Asn1EncodingException("High-tag-number form not supported");
}
if (mDerTagNumber >= 0x1f) {
throw new Asn1EncodingException(
"Unsupported high tag number: " + mDerTagNumber);
}
encoded[0] = BerEncoding.setTagNumber(encoded[0], mDerTagNumber);
encoded[0] = BerEncoding.setTagClass(encoded[0], mDerTagClass);
return encoded;
default:
throw new RuntimeException("Unknown tagging mode: " + mTagging);
}
}
}
private static byte[] createTag(
int tagClass, boolean constructed, int tagNumber, byte[]... contents) {
if (tagNumber >= 0x1f) {
throw new IllegalArgumentException("High tag numbers not supported: " + tagNumber);
}
// tag class & number fit into the first byte
byte firstIdentifierByte =
(byte) ((tagClass << 6) | (constructed ? 1 << 5 : 0) | tagNumber);
int contentsLength = 0;
for (byte[] c : contents) {
contentsLength += c.length;
}
int contentsPosInResult;
byte[] result;
if (contentsLength < 0x80) {
// Length fits into one byte
contentsPosInResult = 2;
result = new byte[contentsPosInResult + contentsLength];
result[0] = firstIdentifierByte;
result[1] = (byte) contentsLength;
} else {
// Length is represented as multiple bytes
// The low 7 bits of the first byte represent the number of length bytes (following the
// first byte) in which the length is in big-endian base-256 form
if (contentsLength <= 0xff) {
contentsPosInResult = 3;
result = new byte[contentsPosInResult + contentsLength];
result[1] = (byte) 0x81; // 1 length byte
result[2] = (byte) contentsLength;
} else if (contentsLength <= 0xffff) {
contentsPosInResult = 4;
result = new byte[contentsPosInResult + contentsLength];
result[1] = (byte) 0x82; // 2 length bytes
result[2] = (byte) (contentsLength >> 8);
result[3] = (byte) (contentsLength & 0xff);
} else if (contentsLength <= 0xffffff) {
contentsPosInResult = 5;
result = new byte[contentsPosInResult + contentsLength];
result[1] = (byte) 0x83; // 3 length bytes
result[2] = (byte) (contentsLength >> 16);
result[3] = (byte) ((contentsLength >> 8) & 0xff);
result[4] = (byte) (contentsLength & 0xff);
} else {
contentsPosInResult = 6;
result = new byte[contentsPosInResult + contentsLength];
result[1] = (byte) 0x84; // 4 length bytes
result[2] = (byte) (contentsLength >> 24);
result[3] = (byte) ((contentsLength >> 16) & 0xff);
result[4] = (byte) ((contentsLength >> 8) & 0xff);
result[5] = (byte) (contentsLength & 0xff);
}
result[0] = firstIdentifierByte;
}
for (byte[] c : contents) {
System.arraycopy(c, 0, result, contentsPosInResult, c.length);
contentsPosInResult += c.length;
}
return result;
}
private static final class JavaToDerConverter {
private JavaToDerConverter() {}
public static byte[] toDer(Object source, Asn1Type targetType, Asn1Type targetElementType)
throws Asn1EncodingException {
Class<?> sourceType = source.getClass();
if (Asn1OpaqueObject.class.equals(sourceType)) {
ByteBuffer buf = ((Asn1OpaqueObject) source).getEncoded();
byte[] result = new byte[buf.remaining()];
buf.get(result);
return result;
}
if ((targetType == null) || (targetType == Asn1Type.ANY)) {
return encode(source);
}
switch (targetType) {
case OCTET_STRING:
case BIT_STRING:
byte[] value = null;
if (source instanceof ByteBuffer) {
ByteBuffer buf = (ByteBuffer) source;
value = new byte[buf.remaining()];
buf.slice().get(value);
} else if (source instanceof byte[]) {
value = (byte[]) source;
}
if (value != null) {
return createTag(
BerEncoding.TAG_CLASS_UNIVERSAL,
false,
BerEncoding.getTagNumber(targetType),
value);
}
break;
case INTEGER:
if (source instanceof Integer) {
return toInteger((Integer) source);
} else if (source instanceof Long) {
return toInteger((Long) source);
} else if (source instanceof BigInteger) {
return toInteger((BigInteger) source);
}
break;
case BOOLEAN:
if (source instanceof Boolean) {
return toBoolean((Boolean) (source));
}
break;
case UTC_TIME:
case GENERALIZED_TIME:
if (source instanceof String) {
return createTag(BerEncoding.TAG_CLASS_UNIVERSAL, false,
BerEncoding.getTagNumber(targetType), ((String) source).getBytes());
}
break;
case OBJECT_IDENTIFIER:
if (source instanceof String) {
return toOid((String) source);
}
break;
case SEQUENCE:
{
Asn1Class containerAnnotation =
sourceType.getDeclaredAnnotation(Asn1Class.class);
if ((containerAnnotation != null)
&& (containerAnnotation.type() == Asn1Type.SEQUENCE)) {
return toSequence(source);
}
break;
}
case CHOICE:
{
Asn1Class containerAnnotation =
sourceType.getDeclaredAnnotation(Asn1Class.class);
if ((containerAnnotation != null)
&& (containerAnnotation.type() == Asn1Type.CHOICE)) {
return toChoice(source);
}
break;
}
case SET_OF:
return toSetOf((Collection<?>) source, targetElementType);
case SEQUENCE_OF:
return toSequenceOf((Collection<?>) source, targetElementType);
default:
break;
}
throw new Asn1EncodingException(
"Unsupported conversion: " + sourceType.getName() + " to ASN.1 " + targetType);
}
}
/** ASN.1 DER-encoded {@code NULL}. */
public static final Asn1OpaqueObject ASN1_DER_NULL =
new Asn1OpaqueObject(new byte[] {BerEncoding.TAG_NUMBER_NULL, 0});
}
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