/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* 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 org.wildfly.security.asn1;
import static org.wildfly.security._private.ElytronMessages.log;
import static org.wildfly.security.asn1.ASN1.*;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.util.ArrayDeque;
import java.util.NoSuchElementException;
import org.wildfly.security.util.ByteIterator;
/**
* A class used to decode ASN.1 values that have been encoded using the Distinguished Encoding Rules (DER).
*
* @author <a href="mailto:fjuma@redhat.com">Farah Juma</a>
*/
public class DERDecoder implements ASN1Decoder {
private final ByteIterator bi;
private final ArrayDeque<DecoderState> states = new ArrayDeque<DecoderState>();
private int implicitTag = -1;
/**
* Create a DER decoder that will decode values from the given byte array.
*
* @param buf the byte array to decode
*/
public DERDecoder(byte[] buf) {
this.bi = ByteIterator.ofBytes(buf);
}
/**
* Create a DER decoder that will decode values from the given byte array.
*
* @param buf the byte array to decode
* @param offset the offset in the byte array of the first byte to read
* @param length the maximum number of bytes to read from the byte array
*/
public DERDecoder(byte[] buf, int offset, int length) {
this.bi = ByteIterator.ofBytes(buf, offset, length);
}
/**
* Create a DER decoder that will decode values from the given {@code ByteIterator}.
*
* @param bi the {@code ByteIterator} from which DER encoded values will be decoded
*/
public DERDecoder(ByteIterator bi) {
this.bi = bi;
}
@Override
public void startSequence() throws ASN1Exception {
readTag(SEQUENCE_TYPE);
int length = readLength();
states.add(new DecoderState(SEQUENCE_TYPE, bi.offset() + length));
}
@Override
public void endSequence() throws ASN1Exception {
DecoderState lastState = states.peekLast();
if ((lastState == null) || (lastState.getTag() != SEQUENCE_TYPE)) {
throw log.noSequenceToEnd();
}
endConstructedElement(lastState.getNextElementIndex());
states.removeLast();
}
@Override
public void startSet() throws ASN1Exception {
readTag(SET_TYPE);
int length = readLength();
states.add(new DecoderState(SET_TYPE, bi.offset() + length));
}
@Override
public void endSet() throws ASN1Exception {
DecoderState lastState = states.peekLast();
if ((lastState == null) || (lastState.getTag() != SET_TYPE)) {
throw log.noSetToEnd();
}
endConstructedElement(lastState.getNextElementIndex());
states.removeLast();
}
@Override
public void startSetOf() throws ASN1Exception {
startSet();
}
@Override
public void endSetOf() throws ASN1Exception {
endSet();
}
@Override
public void startExplicit(int number) throws ASN1Exception {
startExplicit(CONTEXT_SPECIFIC_MASK, number);
}
@Override
public void startExplicit(int clazz, int number) throws ASN1Exception {
int explicitTag = clazz | CONSTRUCTED_MASK | number;
readTag(explicitTag);
int length = readLength();
states.add(new DecoderState(explicitTag, bi.offset() + length));
}
@Override
public void endExplicit() throws ASN1Exception {
DecoderState lastState = states.peekLast();
if ((lastState == null) || (lastState.getTag() == SEQUENCE_TYPE)
|| (lastState.getTag() == SET_TYPE) || ((lastState.getTag() & CONSTRUCTED_MASK) == 0)) {
throw log.noExplicitlyTaggedElementToEnd();
}
endConstructedElement(lastState.getNextElementIndex());
states.removeLast();
}
private void endConstructedElement(int nextElementIndex) throws ASN1Exception {
int pos = bi.offset();
if (pos < nextElementIndex) {
// Any elements in this constructed element that have not yet been read will be discarded
int i;
for (i = 0; i < (nextElementIndex - pos) && bi.hasNext(); i++) {
bi.next();
}
if (i != (nextElementIndex - pos)) {
throw log.asnUnexpectedEndOfInput();
}
} else if (pos > nextElementIndex) {
// Shouldn't happen
throw new IllegalStateException();
}
}
@Override
public byte[] decodeOctetString() throws ASN1Exception {
readTag(OCTET_STRING_TYPE);
int length = readLength();
byte[] result = new byte[length];
if ((length != 0) && (bi.drain(result, 0, length) != length)) {
throw log.asnUnexpectedEndOfInput();
}
return result;
}
@Override
public String decodeOctetStringAsString() throws ASN1Exception {
return decodeOctetStringAsString(StandardCharsets.UTF_8.name());
}
@Override
public String decodeOctetStringAsString(String charSet) throws ASN1Exception {
readTag(OCTET_STRING_TYPE);
int length = readLength();
byte[] octets = new byte[length];
if ((length != 0) && (bi.drain(octets, 0, length) != length)) {
throw log.asnUnexpectedEndOfInput();
}
try {
return new String(octets, charSet);
} catch (UnsupportedEncodingException e) {
throw new ASN1Exception(e);
}
}
@Override
public String decodeIA5String() throws ASN1Exception {
byte[] octets = decodeIA5StringAsBytes();
return new String(octets, StandardCharsets.US_ASCII);
}
@Override
public byte[] decodeIA5StringAsBytes() throws ASN1Exception {
readTag(IA5_STRING_TYPE);
int length = readLength();
byte[] result = new byte[length];
if ((length != 0) && (bi.drain(result, 0, length) != length)) {
throw log.asnUnexpectedEndOfInput();
}
return result;
}
@Override
public byte[] decodeBitString() throws ASN1Exception {
readTag(BIT_STRING_TYPE);
int length = readLength();
byte[] result = new byte[length - 1];
int numUnusedBits = bi.next();
if (numUnusedBits < 0 || numUnusedBits > 7) {
throw log.asnInvalidNumberOfUnusedBits();
}
if (numUnusedBits == 0) {
for (int i = 0; i < (length -1); i++) {
result[i] = (byte) bi.next();
}
} else {
// Any unused bits will be removed
int leftShift = 8 - numUnusedBits;
int previous = 0;
int next;
for (int i = 0; i < (length -1); i++) {
next = bi.next();
if (i == 0) {
result[i] = (byte) (next >>> numUnusedBits);
} else {
result[i] = (byte) ((next >>> numUnusedBits) | (previous << leftShift));
}
previous = next;
}
}
return result;
}
@Override
public BigInteger decodeBitStringAsInteger() {
DERDecoder decoder = new DERDecoder(decodeBitString());
if (decoder.peekType() != INTEGER_TYPE) {
throw log.asnUnexpectedTag();
}
return decoder.decodeInteger();
}
@Override
public String decodeBitStringAsString() throws ASN1Exception {
readTag(BIT_STRING_TYPE);
int length = readLength();
int numUnusedBits = bi.next();
if (numUnusedBits < 0 || numUnusedBits > 7) {
throw log.asnInvalidNumberOfUnusedBits();
}
int k = 0, next;
int numBits = (length - 1) * 8 - numUnusedBits;
StringBuilder result = new StringBuilder(numBits);
for (int i = 0; i < (length - 1); i++) {
next = bi.next();
for (int j = 7; j >= 0 && k < numBits; j--) {
if ((next & (1 << j)) != 0) {
result.append("1");
} else {
result.append("0");
}
k += 1;
}
}
return result.toString();
}
@Override
public String decodePrintableString() throws ASN1Exception {
return new String(decodePrintableStringAsBytes(), StandardCharsets.US_ASCII);
}
@Override
public byte[] decodePrintableStringAsBytes() throws ASN1Exception {
readTag(PRINTABLE_STRING_TYPE);
final int length = readLength();
int c = 0;
byte[] result = new byte[length];
while (bi.hasNext() && c < length) {
final int b = bi.next();
validatePrintableByte(b);
result[c++] = (byte) b;
}
if (c < length) {
throw log.asnUnexpectedEndOfInput();
}
return result;
}
@Override
public String decodeObjectIdentifier() throws ASN1Exception {
readTag(OBJECT_IDENTIFIER_TYPE);
int length = readLength();
int octet;
long value = 0;
BigInteger bigInt = null;
boolean processedFirst = false;
StringBuilder objectIdentifierStr = new StringBuilder();
for (int i = 0; i < length; i++) {
octet = bi.next();
if (value < 0x80000000000000L) {
value = (value << 7) + (octet & 0x7f);
if ((octet & 0x80) == 0) {
// Reached the end of a component value
if (!processedFirst) {
int first = ((int) value / 40);
if (first == 0) {
objectIdentifierStr.append("0");
} else if (first == 1) {
value = value - 40;
objectIdentifierStr.append("1");
} else if (first == 2) {
value = value - 80;
objectIdentifierStr.append("2");
}
processedFirst = true;
}
objectIdentifierStr.append('.');
objectIdentifierStr.append(value);
// Reset for the next component value
value = 0;
}
} else {
if (bigInt == null) {
bigInt = BigInteger.valueOf(value);
}
bigInt = bigInt.shiftLeft(7).add(BigInteger.valueOf(octet & 0x7f));
if ((octet & 0x80) == 0) {
// Reached the end of a component value
objectIdentifierStr.append('.');
objectIdentifierStr.append(bigInt);
// Reset for the next component value
bigInt = null;
value = 0;
}
}
}
return objectIdentifierStr.toString();
}
@Override
public BigInteger decodeInteger() throws ASN1Exception {
if (INTEGER_TYPE != peekType()) {
throw log.asnUnexpectedTag();
}
return new BigInteger(drainElementValue());
}
@Override
public void decodeNull() throws ASN1Exception {
readTag(NULL_TYPE);
int length = readLength();
if (length != 0) {
throw log.asnNonZeroLengthForNullTypeTag();
}
}
@Override
public void decodeImplicit(int number) {
decodeImplicit(CONTEXT_SPECIFIC_MASK, number);
}
@Override
public void decodeImplicit(int clazz, int number) {
if (implicitTag == -1) {
implicitTag = clazz | number;
}
}
@Override
public boolean isNextType(int clazz, int number, boolean isConstructed) {
try {
return peekType() == (clazz | (isConstructed ? CONSTRUCTED_MASK : 0x00) | number);
} catch (ASN1Exception e) {
return false;
}
}
@Override
public int peekType() throws ASN1Exception {
int currOffset = bi.offset();
int tag = readTag();
while ((bi.offset() != currOffset) && bi.hasPrev()) {
bi.prev();
}
return tag;
}
@Override
public void skipElement() throws ASN1Exception {
readTag();
int length = readLength();
int i;
for (i = 0; i < length && bi.hasNext(); i++) {
bi.next();
}
if (i != length) {
throw log.asnUnexpectedEndOfInput();
}
}
@Override
public boolean hasNextElement() {
DecoderState lastState = states.peekLast();
boolean hasNext;
if (lastState != null) {
hasNext = ((bi.offset() < lastState.getNextElementIndex()) && hasCompleteElement());
} else {
hasNext = hasCompleteElement();
}
return hasNext;
}
private boolean hasCompleteElement() {
boolean hasNext;
int currOffset = bi.offset();
try {
readTag();
int length = readLength();
int i;
for (i = 0; (i < length) && bi.hasNext(); i++) {
bi.next();
}
hasNext = (i == length);
} catch (ASN1Exception e) {
hasNext = false;
}
while ((bi.offset() != currOffset) && bi.hasPrev()) {
bi.prev();
}
return hasNext;
}
@Override
public byte[] drainElementValue() throws ASN1Exception {
if (implicitTag != -1) {
implicitTag = -1;
}
readTag();
int length = readLength();
byte[] value = new byte[length];
if ((length != 0) && (bi.drain(value) != length)) {
throw log.asnUnexpectedEndOfInput();
}
return value;
}
@Override
public byte[] drainElement() throws ASN1Exception {
if (implicitTag != -1) {
implicitTag = -1;
}
int currOffset = bi.offset();
readTag();
int valueLength = readLength();
int length = (bi.offset() - currOffset) + valueLength;
while ((bi.offset() != currOffset) && bi.hasPrev()) {
bi.prev();
}
byte[] element = new byte[length];
if ((length != 0) && (bi.drain(element) != length)) {
throw log.asnUnexpectedEndOfInput();
}
return element;
}
private int readTag() throws ASN1Exception {
try {
int tag = bi.next();
int tagClass = tag & CLASS_MASK;
int constructed = tag & CONSTRUCTED_MASK;
int tagNumber = tag & TAG_NUMBER_MASK;
if (tagNumber == 0x1f) {
// High-tag-number form
tagNumber = 0;
int octet = bi.next();
if ((octet & 0x7f) == 0) {
// Bits 7 to 1 of the first subsequent octet cannot be 0
throw log.asnInvalidHighTagNumberForm();
}
while ((octet >= 0) && ((octet & 0x80) != 0)) {
tagNumber |= (octet & 0x7f);
tagNumber <<= 7;
octet = bi.next();
}
tagNumber |= (octet & 0x7f);
}
return (tagClass | constructed | tagNumber);
} catch (NoSuchElementException e) {
throw log.asnUnexpectedEndOfInput();
}
}
private void readTag(int expectedTag) throws ASN1Exception {
if (implicitTag != -1) {
expectedTag = implicitTag | (expectedTag & CONSTRUCTED_MASK);
implicitTag = -1;
}
int currOffset = bi.offset();
int actualTag = readTag();
if (actualTag != expectedTag) {
while ((bi.offset() != currOffset) && bi.hasPrev()) {
bi.prev();
}
throw log.asnUnexpectedTag();
}
}
private int readLength() throws ASN1Exception {
try {
int length = bi.next();
if (length > 127) {
// Long form
int numOctets = length & 0x7f;
if (numOctets > 4) {
throw log.asnLengthEncodingExceeds4bytes();
}
length = 0;
int nextOctet;
for (int i = 0; i < numOctets; i++) {
nextOctet = bi.next();
length = (length << 8) + nextOctet;
}
}
return length;
} catch (NoSuchElementException e) {
throw log.asnUnexpectedEndOfInput();
}
}
/**
* Decodes an OID and resolve its corresponding key algorithm.
*
* @return the key algorithm associated with the OID or null if no algorithm could be resolved
*/
public String decodeObjectIdentifierAsKeyAlgorithm() {
return keyAlgorithmFromOid(decodeObjectIdentifier());
}
/**
* A class used to maintain state information during DER decoding.
*/
private class DecoderState {
// Tag number for a constructed element
private final int tag;
// The position of the first character in the encoded buffer that occurs after
// the encoding of the constructed element
private final int nextElementIndex;
public DecoderState(int tag, int nextElementIndex) {
this.tag = tag;
this.nextElementIndex = nextElementIndex;
}
public int getTag() {
return tag;
}
public int getNextElementIndex() {
return nextElementIndex;
}
}
}