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 d97c35c52220fba7088e337880d3d7635b9d7802..ebd48c4fdabf358b3c3936c0568d371583b9871f 100644
--- a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
+++ b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
@@ -21,6 +21,18 @@ using net::ProxyService;
 
 namespace {
 
+const char kChromeProxyHeader[] = "chrome-proxy";
+const char kActionValueDelimiter = '=';
+
+const char kChromeProxyActionBlock[] = "block";
+const char kChromeProxyActionBypass[] = "bypass";
+
+// Actions for tamper detection fingerprints.
+const char kChromeProxyActionFingerprintChromeProxy[]   = "fcp";
+const char kChromeProxyActionFingerprintVia[]           = "fvia";
+const char kChromeProxyActionFingerprintOtherHeaders[]  = "foh";
+const char kChromeProxyActionFingerprintContentLength[] = "fcl";
+
 const int kShortBypassMaxSeconds = 59;
 const int kMediumBypassMaxSeconds = 300;
 
@@ -35,21 +47,51 @@ base::TimeDelta GetDefaultBypassDuration() {
 
 namespace data_reduction_proxy {
 
+bool GetDataReductionProxyActionValue(
+    const net::HttpResponseHeaders* headers,
+    const std::string& action_prefix,
+    std::string* action_value) {
+  DCHECK(headers);
+  DCHECK(!action_prefix.empty());
+  // A valid action does not include a trailing '='.
+  DCHECK(action_prefix[action_prefix.size() - 1] != kActionValueDelimiter);
+  void* iter = NULL;
+  std::string value;
+  std::string prefix = action_prefix + kActionValueDelimiter;
+
+  while (headers->EnumerateHeader(&iter, kChromeProxyHeader, &value)) {
+    if (value.size() > prefix.size()) {
+      if (LowerCaseEqualsASCII(value.begin(),
+                               value.begin() + prefix.size(),
+                               prefix.c_str())) {
+        if (action_value)
+          *action_value = value.substr(prefix.size());
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 bool ParseHeadersAndSetBypassDuration(const net::HttpResponseHeaders* headers,
                                       const std::string& action_prefix,
                                       base::TimeDelta* bypass_duration) {
+  DCHECK(headers);
+  DCHECK(!action_prefix.empty());
+  // A valid action does not include a trailing '='.
+  DCHECK(action_prefix[action_prefix.size() - 1] != kActionValueDelimiter);
   void* iter = NULL;
   std::string value;
-  std::string name = "chrome-proxy";
+  std::string prefix = action_prefix + kActionValueDelimiter;
 
-  while (headers->EnumerateHeader(&iter, name, &value)) {
-    if (value.size() > action_prefix.size()) {
+  while (headers->EnumerateHeader(&iter, kChromeProxyHeader, &value)) {
+    if (value.size() > prefix.size()) {
       if (LowerCaseEqualsASCII(value.begin(),
-                               value.begin() + action_prefix.size(),
-                               action_prefix.c_str())) {
+                               value.begin() + prefix.size(),
+                               prefix.c_str())) {
         int64 seconds;
         if (!base::StringToInt64(
-                StringPiece(value.begin() + action_prefix.size(), value.end()),
+                StringPiece(value.begin() + prefix.size(), value.end()),
                 &seconds) || seconds < 0) {
           continue;  // In case there is a well formed instruction.
         }
@@ -82,20 +124,21 @@ bool ParseHeadersAndSetProxyInfo(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 (ParseHeadersAndSetBypassDuration(
-          headers, "block=", &proxy_info->bypass_duration)) {
+          headers, kChromeProxyActionBlock, &proxy_info->bypass_duration)) {
     proxy_info->bypass_all = true;
     return true;
   }
 
   // Next, look for 'bypass'.
   if (ParseHeadersAndSetBypassDuration(
-          headers, "bypass=", &proxy_info->bypass_duration)) {
+          headers, kChromeProxyActionBypass, &proxy_info->bypass_duration)) {
     return true;
   }
   return false;
 }
 
-bool HasDataReductionProxyViaHeader(const net::HttpResponseHeaders* headers) {
+bool HasDataReductionProxyViaHeader(const net::HttpResponseHeaders* headers,
+                                    bool* has_intermediary) {
   const size_t kVersionSize = 4;
   const char kDataReductionProxyViaValue[] = "Chrome-Compression-Proxy";
   size_t value_len = strlen(kDataReductionProxyViaValue);
@@ -107,8 +150,13 @@ 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 (has_intermediary)
+        // We assume intermediary exists if there is another Via header after
+        // the data reduction proxy's Via header.
+        *has_intermediary = !(headers->EnumerateHeader(&iter, "via", &value));
       return true;
+    }
   }
 
   // TODO(bengr): Remove deprecated header value.
@@ -116,8 +164,11 @@ 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 (has_intermediary)
+        *has_intermediary = !(headers->EnumerateHeader(&iter, "via", &value));
       return true;
+    }
 
   return false;
 }
@@ -151,7 +202,7 @@ GetDataReductionProxyBypassType(
       !headers->HasHeader("Proxy-Authenticate")) {
     return ProxyService::MALFORMED_407;
   }
-  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
@@ -170,4 +221,59 @@ GetDataReductionProxyBypassType(
   return ProxyService::BYPASS_EVENT_TYPE_MAX;
 }
 
+bool GetDataReductionProxyActionFingerprintChromeProxy(
+    const net::HttpResponseHeaders* headers,
+    std::string* chrome_proxy_fingerprint) {
+  return GetDataReductionProxyActionValue(
+      headers,
+      kChromeProxyActionFingerprintChromeProxy,
+      chrome_proxy_fingerprint);
+}
+
+bool GetDataReductionProxyActionFingerprintVia(
+    const net::HttpResponseHeaders* headers,
+    std::string* via_fingerprint) {
+  return GetDataReductionProxyActionValue(
+      headers,
+      kChromeProxyActionFingerprintVia,
+      via_fingerprint);
+}
+
+bool GetDataReductionProxyActionFingerprintOtherHeaders(
+    const net::HttpResponseHeaders* headers,
+    std::string* other_headers_fingerprint) {
+  return GetDataReductionProxyActionValue(
+      headers,
+      kChromeProxyActionFingerprintOtherHeaders,
+      other_headers_fingerprint);
+}
+
+bool GetDataReductionProxyActionFingerprintContentLength(
+    const net::HttpResponseHeaders* headers,
+    std::string* content_length_fingerprint) {
+  return GetDataReductionProxyActionValue(
+      headers,
+      kChromeProxyActionFingerprintContentLength,
+      content_length_fingerprint);
+}
+
+void GetDataReductionProxyHeaderWithFingerprintRemoved(
+    const net::HttpResponseHeaders* headers,
+    std::vector<std::string>* values) {
+  DCHECK(values);
+  std::string chrome_proxy_fingerprint_prefix = std::string(
+      kChromeProxyActionFingerprintChromeProxy) + kActionValueDelimiter;
+
+  std::string value;
+  void* iter = NULL;
+  while (headers->EnumerateHeader(&iter, kChromeProxyHeader, &value)) {
+    if (!LowerCaseEqualsASCII(
+        value.begin(),
+        value.begin() + chrome_proxy_fingerprint_prefix.size(),
+        chrome_proxy_fingerprint_prefix.c_str())) {
+      values->push_back(value);
+    }
+  }
+}
+
 }  // namespace data_reduction_proxy