Modify data_reduction_proxy_header to support tamper detection logic.

components/data_reduction_proxy/common/data_reduction_proxy_headers.cc

Index: components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
diff --git a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
index 773d14c7042f1443b5c757196c84bec974f702cd..a27f290d94783b064b48ab2e065e62dd2c6aa518 100644
--- a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
+++ b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
@@ -20,10 +20,35 @@ using net::ProxyService;
 
 namespace data_reduction_proxy {
 
+bool GetDataReductionProxyActionValue(
+    const net::HttpResponseHeaders* headers,
+    const std::string& action_prefix,
+    std::string* action_value) {
+  DCHECK(action_prefix.size());

[bengr, 2014/07/16 19:23:56]

DCHECK(!action_prefix.empty());

[xingx, 2014/07/16 21:22:33]

Done.

+  void* iter = NULL;
+  std::string value;
+  std::string name = "chrome-proxy";

[bengr, 2014/07/16 19:23:56]

Add an anonymous namespace above this namespace and add this as const char [],
e.g.:

namespace {
const char kChromeProxyHeader[] = "chrome-proxy";
}

Use this constant directly in EnumerateHeader here and below.

[xingx, 2014/07/16 21:22:33]

Done.

+
+  while (headers->EnumerateHeader(&iter, name, &value)) {
+    if (value.size() > action_prefix.size()) {
+      if (LowerCaseEqualsASCII(value.begin(),
+                               value.begin() + action_prefix.size(),
+                               action_prefix.c_str()) &&
+          value[action_prefix.size()] == '=') {

[bengr, 2014/07/16 19:23:56]

I think it's better to add '=' to the prefix before the loop. You should enforce
that the last character of the prefix is not an '=' before doing so.

[xingx, 2014/07/16 21:22:33]

Done. 

"enforce the last character is not '='", by DCHECK? If so, Done.

+        if (action_value)
+          *action_value = value.substr(action_prefix.size() + 1);
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 bool GetDataReductionProxyBypassDuration(
     const net::HttpResponseHeaders* headers,
     const std::string& action_prefix,
     base::TimeDelta* duration) {
+  DCHECK(action_prefix.size());
   void* iter = NULL;
   std::string value;
   std::string name = "chrome-proxy";
@@ -32,10 +57,12 @@ bool GetDataReductionProxyBypassDuration(
     if (value.size() > action_prefix.size()) {
       if (LowerCaseEqualsASCII(value.begin(),
                                value.begin() + action_prefix.size(),
-                               action_prefix.c_str())) {
+                               action_prefix.c_str()) &&
+          value[action_prefix.size()] == '=') {

[bengr, 2014/07/16 19:23:56]

See above comment. The loop logic shouldn't change.

[xingx, 2014/07/16 21:22:33]

Done.

[xingx, 2014/07/16 21:22:33]

Done.

         int64 seconds;
         if (!base::StringToInt64(
-                StringPiece(value.begin() + action_prefix.size(), value.end()),
+                StringPiece(value.begin() + action_prefix.size() + 1,
+                            value.end()),
                 &seconds) || seconds < 0) {
           continue;  // In case there is a well formed instruction.
         }
@@ -63,20 +90,21 @@ bool GetDataReductionProxyInfo(const net::HttpResponseHeaders* headers,
   // 'block' takes precedence over 'bypass', so look for it first.
   // TODO(bengr): Reduce checks for 'block' and 'bypass' to a single loop.
   if (GetDataReductionProxyBypassDuration(
-      headers, "block=", &proxy_info->bypass_duration)) {
+      headers, "block", &proxy_info->bypass_duration)) {
     proxy_info->bypass_all = true;
     return true;
   }
 
   // Next, look for 'bypass'.
   if (GetDataReductionProxyBypassDuration(
-      headers, "bypass=", &proxy_info->bypass_duration)) {
+      headers, "bypass", &proxy_info->bypass_duration)) {
     return true;
   }
   return false;
 }
 
-bool HasDataReductionProxyViaHeader(const net::HttpResponseHeaders* headers) {
+bool HasDataReductionProxyViaHeader(const net::HttpResponseHeaders* headers,
+                                    bool* is_the_last) {

[bengr, 2014/07/16 19:23:56]

change to has_intermediary.

[xingx, 2014/07/16 21:22:33]

Done.

   const size_t kVersionSize = 4;
   const char kDataReductionProxyViaValue[] = "Chrome-Compression-Proxy";
   size_t value_len = strlen(kDataReductionProxyViaValue);
@@ -88,8 +116,11 @@ bool HasDataReductionProxyViaHeader(const net::HttpResponseHeaders* headers) {
   // 'Via: 1.1 Chrome-Compression-Proxy'
   while (headers->EnumerateHeader(&iter, "via", &value)) {
     if (value.size() >= kVersionSize + value_len &&
-        !value.compare(kVersionSize, value_len, kDataReductionProxyViaValue))
+        !value.compare(kVersionSize, value_len, kDataReductionProxyViaValue)) {
+      if (is_the_last)
+        *is_the_last = !(headers->EnumerateHeader(&iter, "via", &value));
       return true;
+    }
   }
 
   // TODO(bengr): Remove deprecated header value.
@@ -97,8 +128,11 @@ bool HasDataReductionProxyViaHeader(const net::HttpResponseHeaders* headers) {
       "1.1 Chrome Compression Proxy";
   iter = NULL;
   while (headers->EnumerateHeader(&iter, "via", &value))
-    if (value == kDeprecatedDataReductionProxyViaValue)
+    if (value == kDeprecatedDataReductionProxyViaValue) {
+      if (is_the_last)
+        *is_the_last = !(headers->EnumerateHeader(&iter, "via", &value));
       return true;
+    }
 
   return false;
 }
@@ -121,7 +155,7 @@ GetDataReductionProxyBypassEventType(
     // Fall back if a 500, 502 or 503 is returned.
     return ProxyService::INTERNAL_SERVER_ERROR_BYPASS;
   }
-  if (!HasDataReductionProxyViaHeader(headers) &&
+  if (!HasDataReductionProxyViaHeader(headers, NULL) &&
       (headers->response_code() != net::HTTP_NOT_MODIFIED)) {
     // A Via header might not be present in a 304. Since the goal of a 304
     // response is to minimize information transfer, a sender in general