nghttpx: Allow user to specify static obfuscated value via command-line

src/shrpx.cc

@@ -2576,7 +2576,8 @@ int main(int argc, char **argv) {
     }
   }
 
-  if (get_config()->forwarded_by_node_type == FORWARDED_NODE_OBFUSCATED) {
+  if (get_config()->forwarded_by_node_type == FORWARDED_NODE_OBFUSCATED &&
+      get_config()->forwarded_by_obfuscated.empty()) {
     std::random_device rd;
     std::mt19937 gen(rd());
     auto &dst = mod_config()->forwarded_by_obfuscated;

src/shrpx_client_handler.cc

@@ -406,9 +406,13 @@ ClientHandler::ClientHandler(Worker *worker, int fd, SSL *ssl,
 
   if ((get_config()->forwarded_params & FORWARDED_FOR) &&
       get_config()->forwarded_for_node_type == FORWARDED_NODE_OBFUSCATED) {
+    if (get_config()->forwarded_for_obfuscated.empty()) {
       forwarded_for_obfuscated_ = "_";
       forwarded_for_obfuscated_ += util::random_alpha_digit(
           worker_->get_randgen(), SHRPX_OBFUSCATED_NODE_LENGTH);
+    } else {
+      forwarded_for_obfuscated_ = get_config()->forwarded_for_obfuscated;
+    }
   }
 }
 

src/shrpx_config.cc

@@ -638,8 +638,19 @@ int parse_forwarded_node_type(const std::string &optarg) {
     return FORWARDED_NODE_IP;
   }
 
+  if (optarg.size() < 2 || optarg[0] != '_') {
     return -1;
   }
+
+  if (std::find_if_not(std::begin(optarg), std::end(optarg), [](char c) {
+        return util::is_alpha(c) || util::is_digit(c) || c == '.' || c == '_' ||
+               c == '-';
+      }) != std::end(optarg)) {
+    return -1;
+  }
+
+  return FORWARDED_NODE_OBFUSCATED;
+}
 } // namespace
 
 // generated by gennghttpxfun.py
@@ -2083,7 +2094,8 @@ int parse_config(const char *opt, const char *optarg,
     auto type = parse_forwarded_node_type(optarg);
 
     if (type == -1) {
-      LOG(ERROR) << opt << ": unknown node type " << optarg;
+      LOG(ERROR) << opt << ": unknown node type or illegal obfuscated string "
+                 << optarg;
       return -1;
     }
 
@@ -2091,10 +2103,16 @@ int parse_config(const char *opt, const char *optarg,
     case SHRPX_OPTID_FORWARDED_BY:
       mod_config()->forwarded_by_node_type =
           static_cast<shrpx_forwarded_node_type>(type);
+      if (optarg[0] == '_') {
+        mod_config()->forwarded_by_obfuscated = optarg;
+      }
       break;
     case SHRPX_OPTID_FORWARDED_FOR:
       mod_config()->forwarded_for_node_type =
           static_cast<shrpx_forwarded_node_type>(type);
+      if (optarg[0] == '_') {
+        mod_config()->forwarded_for_obfuscated = optarg;
+      }
       break;
     }
 

src/shrpx_config.h

@@ -306,6 +306,10 @@ struct Config {
   // obfuscated value used in "by" parameter of Forwarded header
   // field.
   std::string forwarded_by_obfuscated;
+  // obfuscated value used in "for" parameter of Forwarded header
+  // field.  This is only used when user defined static obfuscated
+  // string is provided.
+  std::string forwarded_for_obfuscated;
   std::chrono::seconds tls_session_timeout;
   ev_tstamp http2_upstream_read_timeout;
   ev_tstamp upstream_read_timeout;