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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.
#include "extensions/browser/content_verifier.h"
#include <algorithm>
#include "base/command_line.h"
#include "base/files/file_path.h"
#include "base/metrics/field_trial.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/common/content_switches.h"
#include "extensions/browser/content_hash_fetcher.h"
#include "extensions/browser/content_hash_reader.h"
#include "extensions/browser/content_verifier_delegate.h"
#include "extensions/browser/extension_registry.h"
#include "extensions/common/constants.h"
#include "extensions/common/extension_l10n_util.h"
#include "extensions/common/switches.h"
namespace {
const char kExperimentName[] = "ExtensionContentVerification";
} // namespace
namespace extensions {
ContentVerifier::ContentVerifier(content::BrowserContext* context,
ContentVerifierDelegate* delegate)
: mode_(GetMode()),
context_(context),
delegate_(delegate),
fetcher_(new ContentHashFetcher(
context,
delegate,
base::Bind(&ContentVerifier::OnFetchComplete, this))) {
}
ContentVerifier::~ContentVerifier() {
}
void ContentVerifier::Start() {
if (mode_ >= BOOTSTRAP)
fetcher_->Start();
}
void ContentVerifier::Shutdown() {
fetcher_.reset();
delegate_.reset();
}
ContentVerifyJob* ContentVerifier::CreateJobFor(
const std::string& extension_id,
const base::FilePath& extension_root,
const base::FilePath& relative_path) {
if (mode_ < BOOTSTRAP || !delegate_)
return NULL;
ExtensionRegistry* registry = ExtensionRegistry::Get(context_);
const Extension* extension =
registry->GetExtensionById(extension_id, ExtensionRegistry::EVERYTHING);
std::set<base::FilePath> paths;
paths.insert(relative_path);
if (!ShouldVerifyAnyPaths(extension, paths))
return NULL;
// TODO(asargent) - we can probably get some good performance wins by having
// a cache of ContentHashReader's that we hold onto past the end of each job.
return new ContentVerifyJob(
new ContentHashReader(extension_id,
*extension->version(),
extension_root,
relative_path,
delegate_->PublicKey()),
base::Bind(&ContentVerifier::VerifyFailed, this, extension->id()));
}
void ContentVerifier::VerifyFailed(const std::string& extension_id,
ContentVerifyJob::FailureReason reason) {
if (!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI)) {
content::BrowserThread::PostTask(
content::BrowserThread::UI,
FROM_HERE,
base::Bind(&ContentVerifier::VerifyFailed, this, extension_id, reason));
return;
}
VLOG(1) << "VerifyFailed " << extension_id << " reason:" << reason;
if (!delegate_ || !fetcher_.get() || mode_ < ENFORCE)
return;
if (reason == ContentVerifyJob::MISSING_ALL_HASHES) {
// If we failed because there were no hashes yet for this extension, just
// request some.
ExtensionRegistry* registry = ExtensionRegistry::Get(context_);
const Extension* extension =
registry->GetExtensionById(extension_id, ExtensionRegistry::EVERYTHING);
if (extension)
fetcher_->DoFetch(extension, true /* force */);
} else {
delegate_->VerifyFailed(extension_id);
}
}
void ContentVerifier::OnFetchComplete(
const std::string& extension_id,
bool success,
bool was_force_check,
const std::set<base::FilePath>& hash_mismatch_paths) {
VLOG(1) << "OnFetchComplete " << extension_id << " success:" << success;
if (!delegate_ || mode_ < ENFORCE)
return;
if (!success && mode_ < ENFORCE_STRICT)
return;
ExtensionRegistry* registry = ExtensionRegistry::Get(context_);
const Extension* extension =
registry->GetExtensionById(extension_id, ExtensionRegistry::EVERYTHING);
if (!extension)
return;
if ((was_force_check && !success) ||
ShouldVerifyAnyPaths(extension, hash_mismatch_paths))
delegate_->VerifyFailed(extension_id);
}
bool ContentVerifier::ShouldVerifyAnyPaths(
const Extension* extension,
const std::set<base::FilePath>& relative_paths) {
if (!extension || !extension->version() ||
!delegate_->ShouldBeVerified(*extension))
return false;
// Images used in the browser get transcoded during install, so skip
// checking them for now. TODO(asargent) - see if we can cache this list
// for a given extension id/version pair.
std::set<base::FilePath> browser_images =
delegate_->GetBrowserImagePaths(extension);
base::FilePath locales_dir = extension->path().Append(kLocaleFolder);
scoped_ptr<std::set<std::string> > all_locales;
for (std::set<base::FilePath>::const_iterator i = relative_paths.begin();
i != relative_paths.end();
++i) {
const base::FilePath& relative_path = *i;
if (relative_path == base::FilePath(kManifestFilename))
continue;
if (ContainsKey(browser_images, relative_path))
continue;
base::FilePath full_path = extension->path().Append(relative_path);
if (locales_dir.IsParent(full_path)) {
if (!all_locales) {
// TODO(asargent) - see if we can cache this list longer to avoid
// having to fetch it more than once for a given run of the
// browser. Maybe it can never change at runtime? (Or if it can, maybe
// there is an event we can listen for to know to drop our cache).
all_locales.reset(new std::set<std::string>);
extension_l10n_util::GetAllLocales(all_locales.get());
}
// Since message catalogs get transcoded during installation, we want
// to skip those paths.
if (full_path.DirName().DirName() == locales_dir &&
!extension_l10n_util::ShouldSkipValidation(
locales_dir, full_path.DirName(), *all_locales))
continue;
}
return true;
}
return false;
}
// static
ContentVerifier::Mode ContentVerifier::GetMode() {
base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
Mode experiment_value = NONE;
const std::string group = base::FieldTrialList::FindFullName(kExperimentName);
if (group == "EnforceStrict")
experiment_value = ENFORCE_STRICT;
else if (group == "Enforce")
experiment_value = ENFORCE;
else if (group == "Bootstrap")
experiment_value = BOOTSTRAP;
// The field trial value that normally comes from the server can be
// overridden on the command line, which we don't want to allow since malware
// can set chrome command line flags. There isn't currently a way to find out
// what the server-provided value is in this case, so we conservatively
// default to the strictest mode if we detect our experiment name being
// overridden.
if (command_line->HasSwitch(::switches::kForceFieldTrials)) {
std::string forced_trials =
command_line->GetSwitchValueASCII(::switches::kForceFieldTrials);
if (forced_trials.find(kExperimentName) != std::string::npos)
experiment_value = ENFORCE_STRICT;
}
Mode cmdline_value = NONE;
if (command_line->HasSwitch(switches::kExtensionContentVerification)) {
std::string switch_value = command_line->GetSwitchValueASCII(
switches::kExtensionContentVerification);
if (switch_value == switches::kExtensionContentVerificationBootstrap)
cmdline_value = BOOTSTRAP;
else if (switch_value == switches::kExtensionContentVerificationEnforce)
cmdline_value = ENFORCE;
else if (switch_value ==
switches::kExtensionContentVerificationEnforceStrict)
cmdline_value = ENFORCE_STRICT;
else
// If no value was provided (or the wrong one), just default to enforce.
cmdline_value = ENFORCE;
}
// We don't want to allow the command-line flags to eg disable enforcement if
// the experiment group says it should be on, or malware may just modify the
// command line flags. So return the more restrictive of the 2 values.
return std::max(experiment_value, cmdline_value);
}
} // namespace extensions
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