DevTools protocol interception, blocking & modification of requests

content/browser/devtools/devtools_url_request_interceptor.cc

+// Copyright 2017 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 "content/browser/devtools/devtools_url_request_interceptor.h"
+
+#include "base/strings/stringprintf.h"
+#include "content/browser/devtools/devtools_agent_host_impl.h"
+#include "content/browser/devtools/devtools_url_interceptor_request_job.h"
+#include "content/browser/devtools/protocol/network_handler.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/devtools_agent_host.h"
+#include "net/http/http_request_headers.h"
+#include "net/url_request/url_request.h"
+
+namespace content {
+namespace {
+const char kDevToolsEmulateNetworkConditionsClientId[] =
+    "X-DevTools-Emulate-Network-Conditions-Client-Id";
+}  // namespace
+
+DevToolsURLRequestInterceptor::DevToolsURLRequestInterceptor()
+    : state_(new State()) {}
+
+DevToolsURLRequestInterceptor::~DevToolsURLRequestInterceptor() {}
+
+net::URLRequestJob* DevToolsURLRequestInterceptor::MaybeInterceptRequest(
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate) const {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  std::string client_id;
+  if (!request->extra_request_headers().GetHeader(
+          kDevToolsEmulateNetworkConditionsClientId, &client_id)) {
+    return nullptr;
+  }
+
+  // We don't want to intercept our own sub requests!
+  if (state_->IsSubRequest(request))
+    return nullptr;
+
+  DevToolsAgentHostImpl* devtools_agent_host_impl =
+      static_cast<DevToolsAgentHostImpl*>(
+          DevToolsAgentHost::GetForId(client_id).get());
+
+  if (!devtools_agent_host_impl)
+    return nullptr;
+
+  protocol::NetworkHandler* network_handler =
+      devtools_agent_host_impl->GetHandler<protocol::NetworkHandler>();
+
+  if (!network_handler || !network_handler->interception_enabled())
+    return nullptr;
+
+  std::string parent_id = state_->GetRedirectChainParentId(request);

[Sami, 2017/03/22 17:00:46]

Just to make sure I understand, does the same |request| get reused across
redirects, but a new job may get created?

[alex clarke (OOO till 29th), 2017/03/24 13:57:24]

Yes. If a 302 is served or mocked then it's sent to the parent |request| which
creates a new URLRequestJob.

+  if (parent_id.empty()) {
+    return new DevToolsURLInterceptorRequestJob(
+        state_->GetWeakPtr(), state_->GetNewId(), request, network_delegate,
+        network_handler, false);
+  } else {
+    return new DevToolsURLInterceptorRequestJob(
+        state_->GetWeakPtr(), std::move(parent_id), request, network_delegate,
+        network_handler, true);
+  }
+}
+
+net::URLRequestJob* DevToolsURLRequestInterceptor::MaybeInterceptRedirect(
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate,
+    const GURL& location) const {
+  return nullptr;
+}
+
+net::URLRequestJob* DevToolsURLRequestInterceptor::MaybeInterceptResponse(
+    net::URLRequest* request,
+    net::NetworkDelegate* network_delegate) const {
+  return nullptr;
+}
+
+DevToolsURLRequestInterceptor::State::State()
+    : next_id_(0), weak_ptr_factory_(this) {}
+
+DevToolsURLRequestInterceptor::State::~State() {}
+
+void DevToolsURLRequestInterceptor::State::RegisterSubRequest(
+    const net::URLRequest* request) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(sub_requests_.find(request) == sub_requests_.end());
+  sub_requests_.insert(request);
+}
+
+void DevToolsURLRequestInterceptor::State::UnregisterSubRequest(
+    const net::URLRequest* request) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(sub_requests_.find(request) != sub_requests_.end());
+  sub_requests_.erase(request);
+}
+
+bool DevToolsURLRequestInterceptor::State::IsSubRequest(
+    const net::URLRequest* request) const {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return sub_requests_.find(request) != sub_requests_.end();
+}
+
+void DevToolsURLRequestInterceptor::State::ExpectRequestAfterRedirect(
+    const net::URLRequest* request,
+    std::string id) {

[Sami, 2017/03/22 17:00:46]

nit: const ref

[alex clarke (OOO till 29th), 2017/03/24 13:57:23]

Done.

+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  expected_redirects_[request] = id;
+}
+
+std::string DevToolsURLRequestInterceptor::State::GetNewId() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return base::StringPrintf("id-%zu", ++next_id_);
+}
+
+std::string DevToolsURLRequestInterceptor::State::GetRedirectChainParentId(
+    const net::URLRequest* request) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  auto find_it = expected_redirects_.find(request);
+  if (find_it == expected_redirects_.end()) {
+    return "";
+  }
+  std::string id = std::move(find_it->second);
+  expected_redirects_.erase(find_it);
+  return id;
+}
+
+}  // namespace content