DevTools protocol interception, blocking & modification of requests

content/browser/devtools/devtools_url_interceptor_request_job.h

Index: content/browser/devtools/devtools_url_interceptor_request_job.h
diff --git a/content/browser/devtools/devtools_url_interceptor_request_job.h b/content/browser/devtools/devtools_url_interceptor_request_job.h
new file mode 100644
index 0000000000000000000000000000000000000000..30bb21c98a67537a353558843b2602a522376cb7
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+++ b/content/browser/devtools/devtools_url_interceptor_request_job.h
@@ -0,0 +1,228 @@
+// 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.
+
+#ifndef CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_URL_INTERCEPTOR_REQUEST_JOB_H_
+#define CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_URL_INTERCEPTOR_REQUEST_JOB_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "content/browser/devtools/devtools_url_request_interceptor.h"
+#include "content/browser/devtools/protocol/network.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/base/net_errors.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_job.h"
+
+namespace content {
+namespace protocol {
+class NetworkHandler;
+}  // namespace
+
+// A URLRequestJob that allows programmatic request blocking / modification or
+// response mocking.
+class DevToolsURLInterceptorRequestJob : public net::URLRequestJob,

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

I'm wondering if there's any risk of wires getting crossed since
net::URLRequestJob is using the original request but this class uses a
subrequest? For instance URLRequestJob::NotifyHeadersComplete() looks at
request_ instead of the subrequest. I was wondering if it would help to delegate
to another URLRequestJob?

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

When we modify a request I think we do need to create a new net::URLRequest
since those changes are not supposed to be visible.  

+                                         public net::URLRequest::Delegate {
+ public:
+  DevToolsURLInterceptorRequestJob(
+      base::WeakPtr<DevToolsURLRequestInterceptor::State> interceptor_state,
+      const std::string& intercept_id,
+      net::URLRequest* origional_request,
+      net::NetworkDelegate* origional_network_delegate,
+      protocol::NetworkHandler* network_handler,
+      bool is_redirect);
+
+  ~DevToolsURLInterceptorRequestJob() override;
+
+  // net::URLRequestJob implementation:
+  void SetExtraRequestHeaders(const net::HttpRequestHeaders& headers) override;
+  void Start() override;
+  void Kill() override;
+  int ReadRawData(net::IOBuffer* buf, int buf_size) override;
+  int GetResponseCode() const override;
+  void GetResponseInfo(net::HttpResponseInfo* info) override;
+  bool GetMimeType(std::string* mime_type) const override;
+  bool GetCharset(std::string* charset) override;
+  void GetLoadTimingInfo(net::LoadTimingInfo* load_timing_info) const override;
+
+  // net::URLRequest::Delegate methods:
+  void OnAuthRequired(net::URLRequest* request,
+                      net::AuthChallengeInfo* auth_info) override;
+  void OnSSLCertificateError(net::URLRequest* request,
+                             const net::SSLInfo& ssl_info,
+                             bool fatal) override;
+  void OnResponseStarted(net::URLRequest* request, int net_error) override;
+  void OnReadCompleted(net::URLRequest* request, int bytes_read) override;
+  void OnReceivedRedirect(net::URLRequest* request,
+                          const net::RedirectInfo& redirect_info,
+                          bool* defer_redirect) override;
+
+  bool OnAllow();

[Sami, 2017/03/22 17:00:45]

minor naming nit: These 4 seem like normal methods rather than event handlers so
I'd drop the "On" prefix.

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

Done.

+  bool OnBlock(net::Error error_reason);
+  bool OnModifyRequest(protocol::Maybe<protocol::String> url,
+                       protocol::Maybe<protocol::String> method,
+                       protocol::Maybe<protocol::String> post_data,
+                       protocol::Maybe<protocol::Network::Headers> headers);
+  bool OnMockResponse(const protocol::String& raw_response);
+
+  void OnNetworkHandlerDeleted();
+
+  // We keep a copy of the original request details to facilitate the
+  // Network.modifyRequest command which could potentially change any of these
+  // fields.
+  struct RequestDetails {
+    RequestDetails(const GURL& url,
+                   const std::string& method,
+                   const std::string& post_data,
+                   const net::HttpRequestHeaders& extra_request_headers,
+                   const net::RequestPriority& priority,
+                   const net::URLRequestContext* url_request_context);
+    ~RequestDetails();
+
+    GURL url;
+    std::string method;
+    std::string post_data;
+    net::HttpRequestHeaders extra_request_headers;
+    net::RequestPriority priority;
+    const net::URLRequestContext* url_request_context;
+  };
+
+ private:
+  class SubRequest;
+
+  struct ModifyRequest {
+    ModifyRequest(protocol::Maybe<protocol::String> url,
+                  protocol::Maybe<protocol::String> method,
+                  protocol::Maybe<protocol::String> post_data,
+                  protocol::Maybe<protocol::Network::Headers> headers);
+    ModifyRequest(ModifyRequest&& other);
+    ~ModifyRequest();
+
+    protocol::Maybe<protocol::String> url;
+    protocol::Maybe<protocol::String> method;
+    protocol::Maybe<protocol::String> post_data;
+    protocol::Maybe<protocol::Network::Headers> headers;
+  };
+
+  // If the request was either allowed or modified, a SubRequest will be used to
+  // perform the fetch and the results proxied to the original request.
+  class SubRequest {
+   public:
+    SubRequest(
+        const DevToolsURLInterceptorRequestJob::RequestDetails& request_details,
+        base::WeakPtr<DevToolsURLRequestInterceptor::State> interceptor_state,
+        DevToolsURLInterceptorRequestJob* devtools_interceptor_request_job);
+    ~SubRequest();
+
+    void Cancel();
+
+    net::URLRequest* request() const { return request_.get(); }
+
+   private:
+    enum { kBufSize = 4096 };
+
+    std::unique_ptr<net::URLRequest> request_;
+
+    // Buffer that |request| writes into.
+    scoped_refptr<net::IOBuffer> buf_;

[Sami, 2017/03/22 17:00:45]

Is this used?

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

It was in earlier patch sets, can remove it now :)

+
+    base::WeakPtr<DevToolsURLRequestInterceptor::State> interceptor_state_;
+
+    DevToolsURLInterceptorRequestJob*
+        devtools_interceptor_request_job_;  // NOT OWNED.
+
+    bool fetch_in_progress_;
+  };
+
+  class MockResponse {
+   public:
+    MockResponse(std::string response_bytes,
+                 base::TimeTicks response_time,
+                 const std::string& intercept_id);
+
+    MockResponse(
+        const scoped_refptr<net::HttpResponseHeaders>& response_headers,
+        std::string response_bytes,
+        size_t read_offset,
+        base::TimeTicks response_time);
+
+    ~MockResponse();
+
+    const scoped_refptr<net::HttpResponseHeaders>& response_headers() const {
+      return response_headers_;
+    }
+
+    base::TimeTicks response_time() const { return response_time_; }
+
+    int ReadRawData(net::IOBuffer* buf, int buf_size);
+
+   private:
+    scoped_refptr<net::HttpResponseHeaders> response_headers_;
+    std::string response_bytes_;
+    size_t read_offset_;
+    base::TimeTicks response_time_;
+  };
+
+  // Retrieves the response headers from either the |sub_request_| or the
+  // |mock_response_|.  In some cases (e.g. file access) this may be null.
+  const net::HttpResponseHeaders* GetHttpResponseHeaders() const;
+
+  void DispatchError(net::Error reason);
+  void ModifyRequestOnIoThread(std::unique_ptr<ModifyRequest> modify_request);
+  void ProcessMockResponeOnIoThread(protocol::String response);
+  void ProcessOnAllowOnIoThread();
+  void SendInterceptedRequestEventOnUiThread();
+  void SendInterceptedRedirectEventOnUiThread(
+      protocol::DictionaryValue* headers_dict,
+      int http_status_code,
+      std::string redirect_url);
+
+  struct IoThreadOnly {
+    explicit IoThreadOnly(net::URLRequest* request);
+    ~IoThreadOnly();
+
+    RequestDetails request_details;
+    std::unique_ptr<SubRequest> sub_request;
+    std::unique_ptr<MockResponse> mock_response;
+    std::unique_ptr<net::RedirectInfo> redirect;
+  };
+
+  struct UiThreadOnly {
+    UiThreadOnly();
+
+    bool waiting_for_user_response;
+  };
+
+  IoThreadOnly io_thread_only_;
+  IoThreadOnly& io_thread_only() {

[Sami, 2017/03/22 17:00:45]

Thanks for making threading explicit!

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

Acknowledged.

+    DCHECK_CURRENTLY_ON(BrowserThread::IO);
+    return io_thread_only_;
+  }
+  const IoThreadOnly& io_thread_only() const {
+    DCHECK_CURRENTLY_ON(BrowserThread::IO);
+    return io_thread_only_;
+  }
+
+  UiThreadOnly ui_thread_only_;
+  UiThreadOnly& ui_thread_only() {
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
+    return ui_thread_only_;
+  }
+  const UiThreadOnly& ui_thread_only() const {
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
+    return ui_thread_only_;
+  }
+
+  const std::string intercept_id_;
+  protocol::NetworkHandler* network_handler_;  // NOT OWNED
+  const base::WeakPtr<DevToolsURLRequestInterceptor::State> interceptor_state_;
+  const scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner_;
+  const bool is_redirect_;
+
+  DISALLOW_COPY_AND_ASSIGN(DevToolsURLInterceptorRequestJob);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_URL_INTERCEPTOR_REQUEST_JOB_H_