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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// The basic usage of the Filter interface is described in the comment at
// the beginning of filter.h. If Filter::Factory is passed a vector of
// size greater than 1, that interface is implemented by a series of filters
// connected in a chain. In such a case the first filter
// in the chain proxies calls to ReadData() so that its return values
// apply to the entire chain.
// In a filter chain, the data flows from first filter (held by the
// caller) down the chain. When ReadData() is called on any filter
// except for the last filter, it proxies the call down the chain,
// filling in the input buffers of subsequent filters if needed (==
// that filter's last_status() value is FILTER_NEED_MORE_DATA) and
// available (== the current filter has data it can output). The last
// Filter will then output data if possible, and return
// FILTER_NEED_MORE_DATA if not. Because the indirection pushes
// data along the filter chain at each level if it's available and the
// next filter needs it, a return value of FILTER_NEED_MORE_DATA from the
// final filter will apply to the entire chain.
#include "net/filter/filter.h"
#include "base/files/file_path.h"
#include "base/strings/string_util.h"
#include "net/base/filename_util_unsafe.h"
#include "net/base/io_buffer.h"
#include "net/base/mime_util.h"
#include "net/base/sdch_net_log_params.h"
#include "net/filter/gzip_filter.h"
#include "net/filter/sdch_filter.h"
#include "net/url_request/url_request_context.h"
#include "url/gurl.h"
namespace net {
namespace {
// Filter types (using canonical lower case only):
const char kDeflate[] = "deflate";
const char kGZip[] = "gzip";
const char kXGZip[] = "x-gzip";
const char kSdch[] = "sdch";
// compress and x-compress are currently not supported. If we decide to support
// them, we'll need the same mime type compatibility hack we have for gzip. For
// more information, see Firefox's nsHttpChannel::ProcessNormal.
// Mime types:
const char kApplicationXGzip[] = "application/x-gzip";
const char kApplicationGzip[] = "application/gzip";
const char kApplicationXGunzip[] = "application/x-gunzip";
const char kTextHtml[] = "text/html";
// Buffer size allocated when de-compressing data.
const int kFilterBufSize = 32 * 1024;
void LogSdchProblem(const FilterContext& filter_context,
SdchProblemCode problem) {
base::Bind(&NetLogSdchResourceProblemCallback, problem));
std::string FilterTypeAsString(Filter::FilterType type_id) {
switch (type_id) {
case Filter::FILTER_TYPE_GZIP:
case Filter::FILTER_TYPE_SDCH:
return "";
} // namespace
FilterContext::~FilterContext() {
Filter::~Filter() {}
// static
Filter* Filter::Factory(const std::vector<FilterType>& filter_types,
const FilterContext& filter_context) {
if (filter_types.empty())
return NULL;
Filter* filter_list = NULL; // Linked list of filters.
for (size_t i = 0; i < filter_types.size(); i++) {
filter_list = PrependNewFilter(filter_types[i], filter_context,
kFilterBufSize, filter_list);
if (!filter_list)
return NULL;
return filter_list;
// static
Filter* Filter::GZipFactory() {
return InitGZipFilter(FILTER_TYPE_GZIP, kFilterBufSize);
// static
Filter* Filter::FactoryForTests(const std::vector<FilterType>& filter_types,
const FilterContext& filter_context,
int buffer_size) {
if (filter_types.empty())
return NULL;
Filter* filter_list = NULL; // Linked list of filters.
for (size_t i = 0; i < filter_types.size(); i++) {
filter_list = PrependNewFilter(filter_types[i], filter_context,
buffer_size, filter_list);
if (!filter_list)
return NULL;
return filter_list;
Filter::FilterStatus Filter::ReadData(char* dest_buffer, int* dest_len) {
const int dest_buffer_capacity = *dest_len;
if (last_status_ == FILTER_ERROR)
return last_status_;
if (!next_filter_.get())
return last_status_ = ReadFilteredData(dest_buffer, dest_len);
// This filter needs more data, but it's not clear that the rest of
// the chain does; delegate the actual status return to the next filter.
if (last_status_ == FILTER_NEED_MORE_DATA && !stream_data_len())
return next_filter_->ReadData(dest_buffer, dest_len);
do {
if (next_filter_->last_status() == FILTER_NEED_MORE_DATA) {
if (FILTER_ERROR == last_status_)
*dest_len = dest_buffer_capacity; // Reset the input/output parameter.
next_filter_->ReadData(dest_buffer, dest_len);
if (FILTER_NEED_MORE_DATA == last_status_)
return next_filter_->last_status();
// In the case where this filter has data internally, and is indicating such
// with a last_status_ of FILTER_OK, but at the same time the next filter in
// the chain indicated it FILTER_NEED_MORE_DATA, we have to be cautious
// about confusing the caller. The API confusion can appear if we return
// FILTER_OK (suggesting we have more data in aggregate), but yet we don't
// populate our output buffer. When that is the case, we need to
// alternately call our filter element, and the next_filter element until we
// get out of this state (by pumping data into the next filter until it
// outputs data, or it runs out of data and reports that it NEED_MORE_DATA.)
} while (FILTER_OK == last_status_ &&
FILTER_NEED_MORE_DATA == next_filter_->last_status() &&
0 == *dest_len);
if (next_filter_->last_status() == FILTER_ERROR)
return FILTER_OK;
bool Filter::FlushStreamBuffer(int stream_data_len) {
DCHECK_LE(stream_data_len, stream_buffer_size_);
if (stream_data_len <= 0 || stream_data_len > stream_buffer_size_)
return false;
// Bail out if there is more data in the stream buffer to be filtered.
if (!stream_buffer() || stream_data_len_)
return false;
next_stream_data_ = stream_buffer()->data();
stream_data_len_ = stream_data_len;
last_status_ = FILTER_OK;
return true;
// static
Filter::FilterType Filter::ConvertEncodingToType(
const std::string& filter_type) {
FilterType type_id;
if (LowerCaseEqualsASCII(filter_type, kDeflate)) {
} else if (LowerCaseEqualsASCII(filter_type, kGZip) ||
LowerCaseEqualsASCII(filter_type, kXGZip)) {
} else if (LowerCaseEqualsASCII(filter_type, kSdch)) {
} else {
// Note we also consider "identity" and "uncompressed" UNSUPPORTED as
// filter should be disabled in such cases.
return type_id;
// static
void Filter::FixupEncodingTypes(
const FilterContext& filter_context,
std::vector<FilterType>* encoding_types) {
std::string mime_type;
bool success = filter_context.GetMimeType(&mime_type);
DCHECK(success || mime_type.empty());
if ((1 == encoding_types->size()) &&
(FILTER_TYPE_GZIP == encoding_types->front())) {
if (LowerCaseEqualsASCII(mime_type, kApplicationXGzip) ||
LowerCaseEqualsASCII(mime_type, kApplicationGzip) ||
LowerCaseEqualsASCII(mime_type, kApplicationXGunzip))
// The server has told us that it sent us gziped content with a gzip
// content encoding. Sadly, Apache mistakenly sets these headers for all
// .gz files. We match Firefox's nsHttpChannel::ProcessNormal and ignore
// the Content-Encoding here.
GURL url;
std::string disposition;
success = filter_context.GetURL(&url);
// Don't supply a MIME type here, since that may cause disk IO.
base::FilePath::StringType extension =
GenerateFileExtensionUnsafe(url, disposition, "UTF-8", "", "", "");
if (filter_context.IsDownload()) {
// We don't want to decompress gzipped files when the user explicitly
// asks to download them.
// For the case of svgz files, we use the extension to distinguish
// between svgz files and svg files compressed with gzip by the server.
// When viewing a .svgz file, we need to uncompress it, but we don't
// want to do that when downloading.
// See Firefox's nonDecodableExtensions in nsExternalHelperAppService.cpp
if (EndsWith(extension, FILE_PATH_LITERAL(".gz"), false) ||
LowerCaseEqualsASCII(extension, ".tgz") ||
LowerCaseEqualsASCII(extension, ".svgz"))
} else {
// When the user does not explicitly ask to download a file, if we get a
// supported mime type, then we attempt to decompress in order to view it.
// However, if it's not a supported mime type, then we will attempt to
// download it, and in that case, don't decompress .gz/.tgz files.
if ((EndsWith(extension, FILE_PATH_LITERAL(".gz"), false) ||
LowerCaseEqualsASCII(extension, ".tgz")) &&
// If the request was for SDCH content, then we might need additional fixups.
if (!filter_context.SdchDictionariesAdvertised()) {
// It was not an SDCH request, so we'll just record stats.
if (1 < encoding_types->size()) {
// Multiple filters were intended to only be used for SDCH (thus far!)
if ((1 == encoding_types->size()) &&
(FILTER_TYPE_SDCH == encoding_types->front())) {
// The request was tagged as an SDCH request, which means the server supplied
// a dictionary, and we advertised it in the request. Some proxies will do
// very strange things to the request, or the response, so we have to handle
// them gracefully.
// If content encoding included SDCH, then everything is "relatively" fine.
if (!encoding_types->empty() &&
(FILTER_TYPE_SDCH == encoding_types->front())) {
// Some proxies (found currently in Argentina) strip the Content-Encoding
// text from "sdch,gzip" to a mere "sdch" without modifying the compressed
// payload. To handle this gracefully, we simulate the "probably" deleted
// ",gzip" by appending a tentative gzip decode, which will default to a
// no-op pass through filter if it doesn't get gzip headers where expected.
if (1 == encoding_types->size()) {
LogSdchProblem(filter_context, SDCH_OPTIONAL_GUNZIP_ENCODING_ADDED);
// There are now several cases to handle for an SDCH request. Foremost, if
// the outbound request was stripped so as not to advertise support for
// encodings, we might get back content with no encoding, or (for example)
// just gzip. We have to be sure that any changes we make allow for such
// minimal coding to work. That issue is why we use TENTATIVE filters if we
// add any, as those filters sniff the content, and act as pass-through
// filters if headers are not found.
// If the outbound GET is not modified, then the server will generally try to
// send us SDCH encoded content. As that content returns, there are several
// corruptions of the header "content-encoding" that proxies may perform (and
// have been detected in the wild). We already dealt with the a honest
// content encoding of "sdch,gzip" being corrupted into "sdch" with on change
// of the actual content. Another common corruption is to either disscard
// the accurate content encoding, or to replace it with gzip only (again, with
// no change in actual content). The last observed corruption it to actually
// change the content, such as by re-gzipping it, and that may happen along
// with corruption of the stated content encoding (wow!).
// The one unresolved failure mode comes when we advertise a dictionary, and
// the server tries to *send* a gzipped file (not gzip encode content), and
// then we could do a gzip decode :-(. Since SDCH is only (currently)
// supported server side on paths that only send HTML content, this mode has
// never surfaced in the wild (and is unlikely to).
// We will gather a lot of stats as we perform the fixups
if (StartsWithASCII(mime_type, kTextHtml, false)) {
// Suspicious case: Advertised dictionary, but server didn't use sdch, and
// we're HTML tagged.
if (encoding_types->empty()) {
LogSdchProblem(filter_context, SDCH_ADDED_CONTENT_ENCODING);
} else if (1 == encoding_types->size()) {
LogSdchProblem(filter_context, SDCH_FIXED_CONTENT_ENCODING);
} else {
LogSdchProblem(filter_context, SDCH_FIXED_CONTENT_ENCODINGS);
} else {
// Remarkable case!?! We advertised an SDCH dictionary, content-encoding
// was not marked for SDCH processing: Why did the server suggest an SDCH
// dictionary in the first place??. Also, the content isn't
// tagged as HTML, despite the fact that SDCH encoding is mostly likely for
// HTML: Did some anti-virus system strip this tag (sometimes they strip
// accept-encoding headers on the request)?? Does the content encoding not
// start with "text/html" for some other reason?? We'll report this as a
// fixup to a binary file, but it probably really is text/html (some how).
if (encoding_types->empty()) {
LogSdchProblem(filter_context, SDCH_BINARY_ADDED_CONTENT_ENCODING);
} else if (1 == encoding_types->size()) {
LogSdchProblem(filter_context, SDCH_BINARY_FIXED_CONTENT_ENCODING);
} else {
LogSdchProblem(filter_context, SDCH_BINARY_FIXED_CONTENT_ENCODINGS);
// Leave the existing encoding type to be processed first, and add our
// tentative decodings to be done afterwards. Vodaphone UK reportedyl will
// perform a second layer of gzip encoding atop the server's sdch,gzip
// encoding, and then claim that the content encoding is a mere gzip. As a
// result we'll need (in that case) to do the gunzip, plus our tentative
// gunzip and tentative SDCH decoding.
// This approach nicely handles the empty() list as well, and should work with
// other (as yet undiscovered) proxies the choose to re-compressed with some
// other encoding (such as bzip2, etc.).
encoding_types->insert(encoding_types->begin(), FILTER_TYPE_SDCH_POSSIBLE);
std::string Filter::OrderedFilterList() const {
if (next_filter_) {
return FilterTypeAsString(type_id_) + "," +
} else {
return FilterTypeAsString(type_id_);
Filter::Filter(FilterType type_id)
: stream_buffer_(NULL),
type_id_(type_id) {}
Filter::FilterStatus Filter::CopyOut(char* dest_buffer, int* dest_len) {
int out_len;
int input_len = *dest_len;
*dest_len = 0;
if (0 == stream_data_len_)
out_len = std::min(input_len, stream_data_len_);
memcpy(dest_buffer, next_stream_data_, out_len);
*dest_len += out_len;
stream_data_len_ -= out_len;
if (0 == stream_data_len_) {
next_stream_data_ = NULL;
} else {
next_stream_data_ += out_len;
return Filter::FILTER_OK;
// static
Filter* Filter::InitGZipFilter(FilterType type_id, int buffer_size) {
scoped_ptr<GZipFilter> gz_filter(new GZipFilter(type_id));
return gz_filter->InitDecoding(type_id) ? gz_filter.release() : NULL;
// static
Filter* Filter::InitSdchFilter(FilterType type_id,
const FilterContext& filter_context,
int buffer_size) {
scoped_ptr<SdchFilter> sdch_filter(new SdchFilter(type_id, filter_context));
return sdch_filter->InitDecoding(type_id) ? sdch_filter.release() : NULL;
// static
Filter* Filter::PrependNewFilter(FilterType type_id,
const FilterContext& filter_context,
int buffer_size,
Filter* filter_list) {
scoped_ptr<Filter> first_filter; // Soon to be start of chain.
switch (type_id) {
first_filter.reset(InitGZipFilter(type_id, buffer_size));
if (filter_context.GetURLRequestContext()->sdch_manager() &&
SdchManager::sdch_enabled()) {
InitSdchFilter(type_id, filter_context, buffer_size));
if (!first_filter.get())
return NULL;
return first_filter.release();
void Filter::InitBuffer(int buffer_size) {
DCHECK_GT(buffer_size, 0);
stream_buffer_ = new IOBuffer(buffer_size);
stream_buffer_size_ = buffer_size;
void Filter::PushDataIntoNextFilter() {
IOBuffer* next_buffer = next_filter_->stream_buffer();
int next_size = next_filter_->stream_buffer_size();
last_status_ = ReadFilteredData(next_buffer->data(), &next_size);
if (FILTER_ERROR != last_status_)
} // namespace net