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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/filter/gzip_header.h"
#include <stdint.h>
#include <string.h>
#include <algorithm>
#include <array>
#include "base/check_op.h"
#include "base/containers/span.h"
#include "third_party/zlib/zlib.h"
namespace net {
// gzip magic header.
static constexpr std::array<uint8_t, 2> kGzipHeaderBytes = {0x1f, 0x8b};
GZipHeader::GZipHeader() {
Reset();
}
GZipHeader::~GZipHeader() = default;
void GZipHeader::Reset() {
state_ = IN_HEADER_ID1;
flags_ = 0;
extra_length_ = 0;
}
GZipHeader::Status GZipHeader::ReadMore(base::span<const uint8_t> inbuf,
size_t& header_end) {
auto pos = inbuf.begin();
while (pos != inbuf.end()) {
switch ( state_ ) {
case IN_HEADER_ID1:
if (*pos != kGzipHeaderBytes[0]) {
return INVALID_HEADER;
}
pos++;
state_++;
break;
case IN_HEADER_ID2:
if (*pos != kGzipHeaderBytes[1]) {
return INVALID_HEADER;
}
pos++;
state_++;
break;
case IN_HEADER_CM:
if ( *pos != Z_DEFLATED ) return INVALID_HEADER;
pos++;
state_++;
break;
case IN_HEADER_FLG:
flags_ = (*pos) & (FLAG_FHCRC | FLAG_FEXTRA |
FLAG_FNAME | FLAG_FCOMMENT);
pos++;
state_++;
break;
case IN_HEADER_MTIME_BYTE_0:
pos++;
state_++;
break;
case IN_HEADER_MTIME_BYTE_1:
pos++;
state_++;
break;
case IN_HEADER_MTIME_BYTE_2:
pos++;
state_++;
break;
case IN_HEADER_MTIME_BYTE_3:
pos++;
state_++;
break;
case IN_HEADER_XFL:
pos++;
state_++;
break;
case IN_HEADER_OS:
pos++;
state_++;
break;
case IN_XLEN_BYTE_0:
if ( !(flags_ & FLAG_FEXTRA) ) {
state_ = IN_FNAME;
break;
}
// We have a two-byte little-endian length, followed by a
// field of that length.
extra_length_ = *pos;
pos++;
state_++;
break;
case IN_XLEN_BYTE_1:
extra_length_ += *pos << 8;
pos++;
state_++;
// We intentionally fall through, because if we have a
// zero-length FEXTRA, we want to check to notice that we're
// done reading the FEXTRA before we exit this loop...
[[fallthrough]];
case IN_FEXTRA: {
// Grab the rest of the bytes in the extra field, or as many
// of them as are actually present so far.
const uint16_t num_extra_bytes = static_cast<uint16_t>(std::min(
static_cast<ptrdiff_t>(extra_length_), (inbuf.end() - pos)));
pos += num_extra_bytes;
extra_length_ -= num_extra_bytes;
if ( extra_length_ == 0 ) {
state_ = IN_FNAME; // advance when we've seen extra_length_ bytes
flags_ &= ~FLAG_FEXTRA; // we're done with the FEXTRA stuff
}
break;
}
case IN_FNAME:
if ( !(flags_ & FLAG_FNAME) ) {
state_ = IN_FCOMMENT;
break;
}
// See if we can find the end of the null-byte-terminated FNAME field.
pos = std::find(pos, inbuf.end(), 0u);
// If the null was found, the end of the FNAME has been reached, and
// need to advance to the next character.
if (pos != inbuf.end()) {
pos++; // Advance past the null-byte.
flags_ &= ~FLAG_FNAME; // We're done with the FNAME stuff.
state_ = IN_FCOMMENT;
}
// Otherwise, everything so far is part of the FNAME, and still have to
// continue looking for the null byte, so nothing else to do until more
// data is received.
break;
case IN_FCOMMENT:
if ( !(flags_ & FLAG_FCOMMENT) ) {
state_ = IN_FHCRC_BYTE_0;
break;
}
// See if we can find the end of the null-byte-terminated FCOMMENT
// field.
pos = std::find(pos, inbuf.end(), 0u);
// If the null was found, the end of the FNAME has been reached, and
// need to advance to the next character.
if (pos != inbuf.end()) {
pos++; // Advance past the null-byte.
flags_ &= ~FLAG_FCOMMENT; // We're done with the FCOMMENT stuff.
state_ = IN_FHCRC_BYTE_0;
}
// Otherwise, everything so far is part of the FCOMMENT, and still have
// to continue looking for the null byte, so nothing else to do until
// more data is received.
break;
case IN_FHCRC_BYTE_0:
if ( !(flags_ & FLAG_FHCRC) ) {
state_ = IN_DONE;
break;
}
pos++;
state_++;
break;
case IN_FHCRC_BYTE_1:
pos++;
flags_ &= ~FLAG_FHCRC; // we're done with the FHCRC stuff
state_++;
break;
case IN_DONE:
header_end = pos - inbuf.begin();
return COMPLETE_HEADER;
}
}
if ( (state_ > IN_HEADER_OS) && (flags_ == 0) ) {
header_end = pos - inbuf.begin();
return COMPLETE_HEADER;
} else {
return INCOMPLETE_HEADER;
}
}
bool GZipHeader::HasGZipHeader(base::span<const uint8_t> inbuf) {
size_t ignored_header_end = 0u;
return GZipHeader().ReadMore(inbuf, ignored_header_end) == COMPLETE_HEADER;
}
} // namespace net
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