Certificate Transparency: Add STH Fetching capability.

components/certificate_transparency/log_proof_fetcher.h

Index: components/certificate_transparency/log_proof_fetcher.h
diff --git a/components/certificate_transparency/log_proof_fetcher.h b/components/certificate_transparency/log_proof_fetcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..f3be4a4c4ade13b64ef60a0d807c8ad0bc754b78
--- /dev/null
+++ b/components/certificate_transparency/log_proof_fetcher.h
@@ -0,0 +1,86 @@
+// Copyright 2015 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 COMPONENTS_CERTIFICATE_TRANSPARENCY_LOG_PROOF_FETCHER_H_
+#define COMPONENTS_CERTIFICATE_TRANSPARENCY_LOG_PROOF_FETCHER_H_
+
+#include <map>
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "net/url_request/url_request.h"
+#include "url/gurl.h"
+
+namespace base {
+class Value;
+}  // namespace base
+
+namespace net {
+
+class URLRequestContext;
+
+namespace ct {
+struct SignedTreeHead;
+}  // namespace ct
+
+}  // namespace net
+
+namespace certificate_transparency {
+
+// Fetches STHs and consistency proofs from Certificate Transparency logs
+// using the URLRequestContext provided during the instance construction.
+class LogProofFetcher : public net::URLRequest::Delegate {
+ public:
+  using FetchSTHCallback =

[mmenke, 2015/07/17 17:57:47]

Google style discourages use of uncommon abbreviations, which I'd say "STH" is.

[Eran Messeri, 2015/07/29 15:16:59]

Done, renamed to SignedTreeHeadFetchedCallback.
Also renamed FetchSTH to FetchSignedTreeHead.

+      base::Callback<void(const std::string&, const net::ct::SignedTreeHead&)>;
+  using FetchFailedCallback = base::Callback<void(const std::string&, int)>;

[mmenke, 2015/07/17 17:57:47]

I believe the callback arguments should be named

[mmenke, 2015/07/17 17:57:48]

Callbacks should be documented.

[mmenke, 2015/07/17 17:57:48]

Need to include callback header.

[Eran Messeri, 2015/07/29 15:16:59]

Done.

[Eran Messeri, 2015/07/29 15:16:59]

Done.

[Eran Messeri, 2015/07/29 15:16:59]

Done.

+  explicit LogProofFetcher(net::URLRequestContext* request_context);

[mmenke, 2015/07/17 17:57:48]

nit:  Add blank line above constructor.

[Eran Messeri, 2015/07/29 15:16:59]

Done.

+  ~LogProofFetcher() override;
+
+  // Fetch the latest Signed Tree Head from the log identified by |log_id|
+  // from |log_url|.
+  void FetchSTH(const GURL& log_url,
+                const std::string& log_id,
+                FetchSTHCallback fetched_cb,
+                FetchFailedCallback failed_cb);

[mmenke, 2015/07/17 17:57:47]

Write out callback.

[mmenke, 2015/07/17 17:57:47]

Callbacks are generally passed via const ref (Even though they technically can
be mutated by invoking them).

[Eran Messeri, 2015/07/29 15:16:59]

Done.

[Eran Messeri, 2015/07/29 15:16:59]

Done.

+
+  // net::URLRequest::Delegate
+  void OnResponseStarted(net::URLRequest* request) override;
+  void OnReadCompleted(net::URLRequest* request, int bytes_read) override;
+
+ private:
+  struct FetchState;
+
+  bool CheckReadStatus(net::URLRequest* request, FetchState* params);
+  void KickOffARead(net::URLRequest* request, FetchState* params);
+
+  // Performs post-report cleanup.
+  void RequestComplete(net::URLRequest* request);
+  // Returns the FetchState associated with the request. The caller takes
+  // ownership of the returned value in case the params should be used before
+  // being deleted.
+  scoped_ptr<FetchState> CleanupRequest(net::URLRequest* request);
+
+  // Actually create the request
+  scoped_ptr<net::URLRequest> CreateURLRequest(const GURL& fetch_sth_url);
+
+  // Callbacks for parsing the STH's JSON by the SafeJsonParser
+  void OnSTHJsonParseSuccess(FetchState params,
+                             scoped_ptr<base::Value> parsed_json);
+  void OnSTHJsonParseError(FetchState params, const std::string& error);
+
+  net::URLRequestContext* const request_context_;
+
+  // Owns the contained requests, as well as FetchState.
+  std::map<net::URLRequest*, FetchState*> inflight_requests_;
+
+  base::WeakPtrFactory<LogProofFetcher> weak_factory_;

[mmenke, 2015/07/17 17:57:47]

Include weak_ptr.h

[Eran Messeri, 2015/07/29 15:16:59]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(LogProofFetcher);

[mmenke, 2015/07/17 17:57:47]

Include base/macros.h for DISALLOW_COPY_AND_ASSIGN.

[Eran Messeri, 2015/07/29 15:16:59]

Done.

+};
+
+}  // namespace certificate_transparency
+
+#endif  // COMPONENTS_CERTIFICATE_TRANSPARENCY_LOG_PROOF_FETCHER_H_