/*
* 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 org.apache.tomcat.util.buf;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.util.ArrayDeque;
import java.util.Deque;
import org.apache.tomcat.util.res.StringManager;
/**
* This is a very basic ASN.1 parser that provides the limited functionality required by Tomcat. It is a long way from a
* complete parser.
* <p>
* TODO: Consider extending/re-writing this parser and refactoring the SpnegoTokenFixer to use it.
*/
public class Asn1Parser {
private static final StringManager sm = StringManager.getManager(Asn1Parser.class);
public static final int TAG_INTEGER = 0x02;
public static final int TAG_OCTET_STRING = 0x04;
public static final int TAG_NULL = 0x05;
public static final int TAG_OID = 0x06;
public static final int TAG_UTF8STRING = 0x0C;
public static final int TAG_SEQUENCE = 0x30;
public static final int TAG_ATTRIBUTE_BASE = 0xA0;
private final byte[] source;
private int pos = 0;
/*
* This is somewhat of a hack to work around the simplified design of the parsing API that could result in ambiguous
* results when nested sequences were optional. Checking the current nesting level of sequence tags enables a user
* of the parser to determine if an optional sequence is present or not.
*
* See https://bz.apache.org/bugzilla/show_bug.cgi?id=67675#c24
*/
private final Deque<Integer> nestedSequenceEndPositions = new ArrayDeque<>();
public Asn1Parser(byte[] source) {
this.source = source;
}
public boolean eof() {
return pos == source.length;
}
public int peekTag() {
return source[pos] & 0xFF;
}
public void parseTagSequence() {
/*
* Check to see if the parser has completely parsed, based on end position for the sequence, any previous
* sequences and remove those sequences from the sequence nesting tracking mechanism if they have been
* completely parsed.
*/
while (!nestedSequenceEndPositions.isEmpty()) {
if (nestedSequenceEndPositions.peekLast().intValue() <= pos) {
nestedSequenceEndPositions.pollLast();
} else {
break;
}
}
// Add the new sequence to the sequence nesting tracking mechanism.
parseTag(TAG_SEQUENCE);
nestedSequenceEndPositions.addLast(Integer.valueOf(-1));
}
public void parseTag(int tag) {
int value = next();
if (value != tag) {
throw new IllegalArgumentException(
sm.getString("asn1Parser.tagMismatch", Integer.valueOf(tag), Integer.valueOf(value)));
}
}
public void parseFullLength() {
int len = parseLength();
if (len + pos != source.length) {
throw new IllegalArgumentException(sm.getString("asn1Parser.lengthInvalid", Integer.valueOf(len),
Integer.valueOf(source.length - pos)));
}
}
public int parseLength() {
int len = next();
if (len > 127) {
int bytes = len - 128;
len = 0;
for (int i = 0; i < bytes; i++) {
len = len << 8;
len = len + next();
}
}
/*
* If this is the first length parsed after a sequence has been added to the sequence nesting tracking mechanism
* it must be the length of the sequence so update the entry to record the end position of the sequence. Note
* that position recorded is actually the start of the first element after the sequence ends.
*/
if (nestedSequenceEndPositions.peekLast() != null && nestedSequenceEndPositions.peekLast().intValue() == -1) {
nestedSequenceEndPositions.pollLast();
nestedSequenceEndPositions.addLast(Integer.valueOf(pos + len));
}
return len;
}
public BigInteger parseInt() {
byte[] val = parseBytes(TAG_INTEGER);
return new BigInteger(val);
}
public byte[] parseOctetString() {
return parseBytes(TAG_OCTET_STRING);
}
public void parseNull() {
parseBytes(TAG_NULL);
}
public byte[] parseOIDAsBytes() {
return parseBytes(TAG_OID);
}
public String parseUTF8String() {
byte[] val = parseBytes(TAG_UTF8STRING);
return new String(val, StandardCharsets.UTF_8);
}
public byte[] parseAttributeAsBytes(int index) {
return parseBytes(TAG_ATTRIBUTE_BASE + index);
}
private byte[] parseBytes(int tag) {
parseTag(tag);
int len = parseLength();
byte[] result = new byte[len];
System.arraycopy(source, pos, result, 0, result.length);
pos += result.length;
return result;
}
public void parseBytes(byte[] dest) {
System.arraycopy(source, pos, dest, 0, dest.length);
pos += dest.length;
}
private int next() {
return source[pos++] & 0xFF;
}
public int getNestedSequenceLevel() {
return nestedSequenceEndPositions.size();
}
}