/*
* Copyright (C) 2013 Square, Inc.
*
* 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.koushikdutta.async.http.spdy;
import com.koushikdutta.async.ByteBufferList;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
/**
* Read and write HPACK v08.
* <p/>
* http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08
* <p/>
* This implementation uses an array for the header table with a bitset for
* references. Dynamic entries are added to the array, starting in the last
* position moving forward. When the array fills, it is doubled.
*/
final class HpackDraft08 {
private static final int PREFIX_4_BITS = 0x0f;
private static final int PREFIX_6_BITS = 0x3f;
private static final int PREFIX_7_BITS = 0x7f;
private static final Header[] STATIC_HEADER_TABLE = new Header[]{
new Header(Header.TARGET_AUTHORITY, ""),
new Header(Header.TARGET_METHOD, "GET"),
new Header(Header.TARGET_METHOD, "POST"),
new Header(Header.TARGET_PATH, "/"),
new Header(Header.TARGET_PATH, "/index.html"),
new Header(Header.TARGET_SCHEME, "http"),
new Header(Header.TARGET_SCHEME, "https"),
new Header(Header.RESPONSE_STATUS, "200"),
new Header(Header.RESPONSE_STATUS, "204"),
new Header(Header.RESPONSE_STATUS, "206"),
new Header(Header.RESPONSE_STATUS, "304"),
new Header(Header.RESPONSE_STATUS, "400"),
new Header(Header.RESPONSE_STATUS, "404"),
new Header(Header.RESPONSE_STATUS, "500"),
new Header("accept-charset", ""),
new Header("accept-encoding", "gzip, deflate"),
new Header("accept-language", ""),
new Header("accept-ranges", ""),
new Header("accept", ""),
new Header("access-control-allow-origin", ""),
new Header("age", ""),
new Header("allow", ""),
new Header("authorization", ""),
new Header("cache-control", ""),
new Header("content-disposition", ""),
new Header("content-encoding", ""),
new Header("content-language", ""),
new Header("content-length", ""),
new Header("content-location", ""),
new Header("content-range", ""),
new Header("content-type", ""),
new Header("cookie", ""),
new Header("date", ""),
new Header("etag", ""),
new Header("expect", ""),
new Header("expires", ""),
new Header("from", ""),
new Header("host", ""),
new Header("if-match", ""),
new Header("if-modified-since", ""),
new Header("if-none-match", ""),
new Header("if-range", ""),
new Header("if-unmodified-since", ""),
new Header("last-modified", ""),
new Header("link", ""),
new Header("location", ""),
new Header("max-forwards", ""),
new Header("proxy-authenticate", ""),
new Header("proxy-authorization", ""),
new Header("range", ""),
new Header("referer", ""),
new Header("refresh", ""),
new Header("retry-after", ""),
new Header("server", ""),
new Header("set-cookie", ""),
new Header("strict-transport-security", ""),
new Header("transfer-encoding", ""),
new Header("user-agent", ""),
new Header("vary", ""),
new Header("via", ""),
new Header("www-authenticate", "")
};
private HpackDraft08() {
}
// http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08#section-3.2
static final class Reader {
private final List<Header> emittedHeaders = new ArrayList<Header>();
private final ByteBufferList source = new ByteBufferList();
private int maxHeaderTableByteCountSetting;
private int maxHeaderTableByteCount;
// Visible for testing.
Header[] headerTable = new Header[8];
// Array is populated back to front, so new entries always have lowest index.
int nextHeaderIndex = headerTable.length - 1;
int headerCount = 0;
/**
* Set bit positions indicate {@code headerTable[pos]} should be emitted.
*/
// Using a BitArray as it has left-shift operator.
BitArray referencedHeaders = new BitArray.FixedCapacity();
/**
* Set bit positions indicate {@code headerTable[pos]} was already emitted.
*/
BitArray emittedReferencedHeaders = new BitArray.FixedCapacity();
int headerTableByteCount = 0;
Reader(int maxHeaderTableByteCountSetting) {
this.maxHeaderTableByteCountSetting = maxHeaderTableByteCountSetting;
this.maxHeaderTableByteCount = maxHeaderTableByteCountSetting;
}
public void refill(ByteBufferList bb) {
bb.get(source);
}
int maxHeaderTableByteCount() {
return maxHeaderTableByteCount;
}
/**
* Called by the reader when the peer sent a new header table size setting.
* While this establishes the maximum header table size, the
* {@link #maxHeaderTableByteCount} set during processing may limit the
* table size to a smaller amount.
* <p> Evicts entries or clears the table as needed.
*/
void maxHeaderTableByteCountSetting(int newMaxHeaderTableByteCountSetting) {
this.maxHeaderTableByteCountSetting = newMaxHeaderTableByteCountSetting;
this.maxHeaderTableByteCount = maxHeaderTableByteCountSetting;
adjustHeaderTableByteCount();
}
private void adjustHeaderTableByteCount() {
if (maxHeaderTableByteCount < headerTableByteCount) {
if (maxHeaderTableByteCount == 0) {
clearHeaderTable();
} else {
evictToRecoverBytes(headerTableByteCount - maxHeaderTableByteCount);
}
}
}
private void clearHeaderTable() {
clearReferenceSet();
Arrays.fill(headerTable, null);
nextHeaderIndex = headerTable.length - 1;
headerCount = 0;
headerTableByteCount = 0;
}
/**
* Returns the count of entries evicted.
*/
private int evictToRecoverBytes(int bytesToRecover) {
int entriesToEvict = 0;
if (bytesToRecover > 0) {
// determine how many headers need to be evicted.
for (int j = headerTable.length - 1; j >= nextHeaderIndex && bytesToRecover > 0; j--) {
bytesToRecover -= headerTable[j].hpackSize;
headerTableByteCount -= headerTable[j].hpackSize;
headerCount--;
entriesToEvict++;
}
referencedHeaders.shiftLeft(entriesToEvict);
emittedReferencedHeaders.shiftLeft(entriesToEvict);
System.arraycopy(headerTable, nextHeaderIndex + 1, headerTable,
nextHeaderIndex + 1 + entriesToEvict, headerCount);
nextHeaderIndex += entriesToEvict;
}
return entriesToEvict;
}
/**
* Read {@code byteCount} bytes of headers from the source stream into the
* set of emitted headers. This implementation does not propagate the never
* indexed flag of a header.
*/
void readHeaders() throws IOException {
while (source.hasRemaining()) {
int b = source.get() & 0xff;
if (b == 0x80) { // 10000000
throw new IOException("index == 0");
} else if ((b & 0x80) == 0x80) { // 1NNNNNNN
int index = readInt(b, PREFIX_7_BITS);
readIndexedHeader(index - 1);
} else if (b == 0x40) { // 01000000
readLiteralHeaderWithIncrementalIndexingNewName();
} else if ((b & 0x40) == 0x40) { // 01NNNNNN
int index = readInt(b, PREFIX_6_BITS);
readLiteralHeaderWithIncrementalIndexingIndexedName(index - 1);
} else if ((b & 0x20) == 0x20) { // 001NNNNN
if ((b & 0x10) == 0x10) { // 0011NNNN
if ((b & 0x0f) != 0)
throw new IOException("Invalid header table state change " + b);
clearReferenceSet(); // 00110000
} else { // 0010NNNN
maxHeaderTableByteCount = readInt(b, PREFIX_4_BITS);
if (maxHeaderTableByteCount < 0
|| maxHeaderTableByteCount > maxHeaderTableByteCountSetting) {
throw new IOException("Invalid header table byte count " + maxHeaderTableByteCount);
}
adjustHeaderTableByteCount();
}
} else if (b == 0x10 || b == 0) { // 000?0000 - Ignore never indexed bit.
readLiteralHeaderWithoutIndexingNewName();
} else { // 000?NNNN - Ignore never indexed bit.
int index = readInt(b, PREFIX_4_BITS);
readLiteralHeaderWithoutIndexingIndexedName(index - 1);
}
}
}
private void clearReferenceSet() {
referencedHeaders.clear();
emittedReferencedHeaders.clear();
}
void emitReferenceSet() {
for (int i = headerTable.length - 1; i != nextHeaderIndex; --i) {
if (referencedHeaders.get(i) && !emittedReferencedHeaders.get(i)) {
emittedHeaders.add(headerTable[i]);
}
}
}
/**
* Returns all headers emitted since they were last cleared, then clears the
* emitted headers.
*/
List<Header> getAndReset() {
List<Header> result = new ArrayList<Header>(emittedHeaders);
emittedHeaders.clear();
emittedReferencedHeaders.clear();
return result;
}
private void readIndexedHeader(int index) throws IOException {
if (isStaticHeader(index)) {
index -= headerCount;
if (index > STATIC_HEADER_TABLE.length - 1) {
throw new IOException("Header index too large " + (index + 1));
}
Header staticEntry = STATIC_HEADER_TABLE[index];
if (maxHeaderTableByteCount == 0) {
emittedHeaders.add(staticEntry);
} else {
insertIntoHeaderTable(-1, staticEntry);
}
} else {
int headerTableIndex = headerTableIndex(index);
if (!referencedHeaders.get(headerTableIndex)) { // When re-referencing, emit immediately.
emittedHeaders.add(headerTable[headerTableIndex]);
emittedReferencedHeaders.set(headerTableIndex);
}
referencedHeaders.toggle(headerTableIndex);
}
}
// referencedHeaders is relative to nextHeaderIndex + 1.
private int headerTableIndex(int index) {
return nextHeaderIndex + 1 + index;
}
private void readLiteralHeaderWithoutIndexingIndexedName(int index) throws IOException {
ByteString name = getName(index);
ByteString value = readByteString();
emittedHeaders.add(new Header(name, value));
}
private void readLiteralHeaderWithoutIndexingNewName() throws IOException {
ByteString name = checkLowercase(readByteString());
ByteString value = readByteString();
emittedHeaders.add(new Header(name, value));
}
private void readLiteralHeaderWithIncrementalIndexingIndexedName(int nameIndex)
throws IOException {
ByteString name = getName(nameIndex);
ByteString value = readByteString();
insertIntoHeaderTable(-1, new Header(name, value));
}
private void readLiteralHeaderWithIncrementalIndexingNewName() throws IOException {
ByteString name = checkLowercase(readByteString());
ByteString value = readByteString();
insertIntoHeaderTable(-1, new Header(name, value));
}
private ByteString getName(int index) {
if (isStaticHeader(index)) {
return STATIC_HEADER_TABLE[index - headerCount].name;
} else {
return headerTable[headerTableIndex(index)].name;
}
}
private boolean isStaticHeader(int index) {
return index >= headerCount;
}
/**
* index == -1 when new.
*/
private void insertIntoHeaderTable(int index, Header entry) {
int delta = entry.hpackSize;
if (index != -1) { // Index -1 == new header.
delta -= headerTable[headerTableIndex(index)].hpackSize;
}
// if the new or replacement header is too big, drop all entries.
if (delta > maxHeaderTableByteCount) {
clearHeaderTable();
// emit the large header to the callback.
emittedHeaders.add(entry);
return;
}
// Evict headers to the required length.
int bytesToRecover = (headerTableByteCount + delta) - maxHeaderTableByteCount;
int entriesEvicted = evictToRecoverBytes(bytesToRecover);
if (index == -1) { // Adding a value to the header table.
if (headerCount + 1 > headerTable.length) { // Need to grow the header table.
Header[] doubled = new Header[headerTable.length * 2];
System.arraycopy(headerTable, 0, doubled, headerTable.length, headerTable.length);
if (doubled.length == 64) {
referencedHeaders = ((BitArray.FixedCapacity) referencedHeaders).toVariableCapacity();
emittedReferencedHeaders =
((BitArray.FixedCapacity) emittedReferencedHeaders).toVariableCapacity();
}
referencedHeaders.shiftLeft(headerTable.length);
emittedReferencedHeaders.shiftLeft(headerTable.length);
nextHeaderIndex = headerTable.length - 1;
headerTable = doubled;
}
index = nextHeaderIndex--;
referencedHeaders.set(index);
headerTable[index] = entry;
headerCount++;
} else { // Replace value at same position.
index += headerTableIndex(index) + entriesEvicted;
referencedHeaders.set(index);
headerTable[index] = entry;
}
headerTableByteCount += delta;
}
private int readByte() throws IOException {
return source.get() & 0xff;
}
int readInt(int firstByte, int prefixMask) throws IOException {
int prefix = firstByte & prefixMask;
if (prefix < prefixMask) {
return prefix; // This was a single byte value.
}
// This is a multibyte value. Read 7 bits at a time.
int result = prefixMask;
int shift = 0;
while (true) {
int b = readByte();
if ((b & 0x80) != 0) { // Equivalent to (b >= 128) since b is in [0..255].
result += (b & 0x7f) << shift;
shift += 7;
} else {
result += b << shift; // Last byte.
break;
}
}
return result;
}
/**
* Reads a potentially Huffman encoded byte string.
*/
ByteString readByteString() throws IOException {
int firstByte = readByte();
boolean huffmanDecode = (firstByte & 0x80) == 0x80; // 1NNNNNNN
int length = readInt(firstByte, PREFIX_7_BITS);
if (huffmanDecode) {
return ByteString.of(Huffman.get().decode(source.getBytes(length)));
} else {
return ByteString.of(source.getBytes(length));
}
}
}
private static final Map<ByteString, Integer> NAME_TO_FIRST_INDEX = nameToFirstIndex();
private static Map<ByteString, Integer> nameToFirstIndex() {
Map<ByteString, Integer> result = new LinkedHashMap<ByteString, Integer>(STATIC_HEADER_TABLE.length);
for (int i = 0; i < STATIC_HEADER_TABLE.length; i++) {
if (!result.containsKey(STATIC_HEADER_TABLE[i].name)) {
result.put(STATIC_HEADER_TABLE[i].name, i);
}
}
return Collections.unmodifiableMap(result);
}
static final class Writer {
Writer() {
}
/**
* This does not use "never indexed" semantics for sensitive headers.
*/
// https://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08#section-4.3.3
ByteBufferList writeHeaders(List<Header> headerBlock) throws IOException {
ByteBufferList out = new ByteBufferList();
// TODO: implement index tracking
ByteBuffer current = ByteBufferList.obtain(8192);
for (int i = 0, size = headerBlock.size(); i < size; i++) {
if (current.remaining() < current.capacity() / 2) {
current.flip();
out.add(current);
current = ByteBufferList.obtain(current.capacity() * 2);
}
ByteString name = headerBlock.get(i).name.toAsciiLowercase();
Integer staticIndex = NAME_TO_FIRST_INDEX.get(name);
if (staticIndex != null) {
// Literal Header Field without Indexing - Indexed Name.
writeInt(current, staticIndex + 1, PREFIX_4_BITS, 0);
writeByteString(current, headerBlock.get(i).value);
} else {
current.put((byte) 0x00); // Literal Header without Indexing - New Name.
writeByteString(current, name);
writeByteString(current, headerBlock.get(i).value);
}
}
out.add(current);
return out;
}
// http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08#section-4.1.1
void writeInt(ByteBuffer out, int value, int prefixMask, int bits) throws IOException {
// Write the raw value for a single byte value.
if (value < prefixMask) {
out.put((byte) (bits | value));
return;
}
// Write the mask to start a multibyte value.
out.put((byte)(bits | prefixMask));
value -= prefixMask;
// Write 7 bits at a time 'til we're done.
while (value >= 0x80) {
int b = value & 0x7f;
out.put((byte) (b | 0x80));
value >>>= 7;
}
out.put((byte) value);
}
void writeByteString(ByteBuffer out, ByteString data) throws IOException {
writeInt(out, data.size(), PREFIX_7_BITS, 0);
out.put(data.toByteArray());
}
}
/**
* An HTTP/2 response cannot contain uppercase header characters and must
* be treated as malformed.
*/
private static ByteString checkLowercase(ByteString name) throws IOException {
for (int i = 0, length = name.size(); i < length; i++) {
byte c = name.getByte(i);
if (c >= 'A' && c <= 'Z') {
throw new IOException("PROTOCOL_ERROR response malformed: mixed case name: " + name.utf8());
}
}
return name;
}
}