Modify data_reduction_proxy_header to support tamper detection logic.

components/data_reduction_proxy/common/data_reduction_proxy_headers.cc

 // 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 "components/data_reduction_proxy/common/data_reduction_proxy_headers.h"
 
 #include <string>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/time/time.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_status_code.h"
 #include "net/proxy/proxy_service.h"
 
 using base::StringPiece;
 using base::TimeDelta;
 using net::ProxyService;
 
 namespace data_reduction_proxy {
 
 const char* kDataReductionProxyViaValues[] = {"Chrome-Compression-Proxy",
                                               "Chrome Compression Proxy"};
 
+bool GetDataReductionProxyActionValue(
+    const net::HttpResponseHeaders* headers,
+    const std::string& action_prefix,
+    std::string* action_value) {
+  void* iter = NULL;
+  std::string value;
+  std::string name = "chrome-proxy";

[bolian, 2014/07/14 19:23:58]

inline this in the func call.  (Don't we have constant for this yet?)

[xingx, 2014/07/14 21:37:16]

Acknowledged.

[bolian, 2014/07/14 22:42:43]

?

[xingx, 2014/07/14 22:51:08]

Copied code from below.

+
+  while (headers->EnumerateHeader(&iter, name, &value)) {
+    if (value.size() > action_prefix.size()) {

[xingx, 2014/07/14 21:37:16]

Done.

It should be ">=" to get the empty value, but right now, at least action_prefix
+ "=", so it needs to be ">"

+      if (LowerCaseEqualsASCII(value.begin(),
+                               value.begin() + action_prefix.size(),
+                               action_prefix.c_str())) {
+        *action_value = value.substr(action_prefix.size());

[bengr, 2014/07/14 18:27:13]

Before the loop, either DCHECK that action_value is not NULL, or, if you allow
NULL, only write to action_value if not NULL.

[xingx, 2014/07/14 21:37:16]

Done.

+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 bool GetDataReductionProxyBypassDuration(
     const net::HttpResponseHeaders* headers,
     const std::string& action_prefix,
     base::TimeDelta* duration) {
   void* iter = NULL;
   std::string value;
   std::string name = "chrome-proxy";
 
   while (headers->EnumerateHeader(&iter, name, &value)) {
     if (value.size() > action_prefix.size()) {
@@ skipping 101 matching lines @@
         headers->response_code() < net::HTTP_INTERNAL_SERVER_ERROR) {
       return ProxyService::PROXY_4XX_BYPASS;
     }
     return ProxyService::MISSING_VIA_HEADER;
   }
   // There is no bypass event.
   return ProxyService::BYPASS_EVENT_TYPE_MAX;
 }
 
 }  // namespace data_reduction_proxy