nghttpx: Add --padding option for debugging purpose

src/shrpx.cc

@@ -437,6 +437,7 @@ void fill_default_config()
   mod_config()->http2_upstream_dump_response_header = nullptr;
   mod_config()->http2_no_cookie_crumbling = false;
   mod_config()->upstream_frame_debug = false;
+  mod_config()->padding = 0;
 }
 } // namespace
 
@@ -675,6 +676,11 @@ void print_help(std::ostream& out)
       << "    --backend-no-tls   Disable SSL/TLS on backend connections.\n"
       << "    --http2-no-cookie-crumbling\n"
       << "                       Don't crumble cookie header field.\n"
+      << "    --padding=<BOUNDARY>\n"
+      << "                       Padding boundary for HTTP/2 frame payload.\n"
+      << "                       Specify 0 to disable padding. This option is\n"
+      << "                       meant for debugging purpose and not intended\n"
+      << "                       to enhance protocol security.\n"
       << "\n"
       << "  Mode:\n"
       << "    (default mode)     Accept HTTP/2.0, SPDY and HTTP/1.1 over\n"
@@ -824,6 +830,7 @@ int main(int argc, char **argv)
       {"frontend-http2-connection-window-bits", required_argument, &flag, 46},
       {"backend-http2-connection-window-bits", required_argument, &flag, 47},
       {"tls-proto-list", required_argument, &flag, 48},
+      {"padding", required_argument, &flag, 49},
       {nullptr, 0, nullptr, 0 }
     };
 
@@ -1060,6 +1067,10 @@ int main(int argc, char **argv)
         // --tls-proto-list
         cmdcfgs.emplace_back(SHRPX_OPT_TLS_PROTO_LIST, optarg);
         break;
+      case 49:
+        // --padding
+        cmdcfgs.emplace_back(SHRPX_OPT_PADDING, optarg);
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -116,6 +116,7 @@ const char SHRPX_OPT_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER[] =
   "frontend-http2-dump-response-header";
 const char SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING[] = "http2-no-cookie-crumbling";
 const char SHRPX_OPT_FRONTEND_FRAME_DEBUG[] = "frontend-frame-debug";
+const char SHRPX_OPT_PADDING[] = "padding";
 
 namespace {
 Config *config = nullptr;
@@ -483,6 +484,8 @@ int parse_config(const char *opt, const char *optarg)
     mod_config()->http2_no_cookie_crumbling = util::strieq(optarg, "yes");
   } else if(util::strieq(opt, SHRPX_OPT_FRONTEND_FRAME_DEBUG)) {
     mod_config()->upstream_frame_debug = util::strieq(optarg, "yes");
+  } else if(util::strieq(opt, SHRPX_OPT_PADDING)) {
+    mod_config()->padding = strtoul(optarg, nullptr, 10);
   } else if(util::strieq(opt, "conf")) {
     LOG(WARNING) << "conf is ignored";
   } else {

src/shrpx_config.h

@@ -103,6 +103,7 @@ extern const char SHRPX_OPT_FRONTEND_HTTP2_DUMP_REQUEST_HEADER[];
 extern const char SHRPX_OPT_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER[];
 extern const char SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING[];
 extern const char SHRPX_OPT_FRONTEND_FRAME_DEBUG[];
+extern const char SHRPX_OPT_PADDING[];
 
 union sockaddr_union {
   sockaddr sa;
@@ -180,6 +181,7 @@ struct Config {
   size_t npn_list_len;
   // The number of elements in tls_proto_list
   size_t tls_proto_list_len;
+  size_t padding;
   // downstream protocol; this will be determined by given options.
   shrpx_proto downstream_proto;
   int syslog_facility;

src/shrpx_http.cc

@@ -94,6 +94,17 @@ std::string colorizeHeaders(const char *hdrs)
   return nhdrs;
 }
 
+ssize_t select_padding_callback
+(nghttp2_session *session, const nghttp2_frame *frame, size_t max_payload,
+ void *user_data)
+{
+  auto bd = get_config()->padding;
+  if(frame->hd.length == 0) {
+    return bd;
+  }
+  return std::min(max_payload, (frame->hd.length + bd - 1) / bd * bd);
+}
+
 } // namespace http
 
 } // namespace shrpx

src/shrpx_http.h

@@ -29,6 +29,8 @@
 
 #include <string>
 
+#include <nghttp2/nghttp2.h>
+
 namespace shrpx {
 
 namespace http {
@@ -40,6 +42,10 @@ std::string create_via_header_value(int major, int minor);
 // Adds ANSI color codes to HTTP headers |hdrs|.
 std::string colorizeHeaders(const char *hdrs);
 
+ssize_t select_padding_callback
+(nghttp2_session *session, const nghttp2_frame *frame, size_t max_payload,
+ void *user_data);
+
 } // namespace http
 
 } // namespace shrpx

src/shrpx_http2_session.cc

@@ -1193,6 +1193,9 @@ int Http2Session::on_connect()
   callbacks.on_unknown_frame_recv_callback = on_unknown_frame_recv_callback;
   callbacks.on_header_callback = on_header_callback;
   callbacks.on_begin_headers_callback = on_begin_headers_callback;
+  if(get_config()->padding) {
+    callbacks.select_padding_callback = http::select_padding_callback;
+  }
 
   nghttp2_opt_set opt_set;
   opt_set.no_auto_stream_window_update = 1;

src/shrpx_http2_upstream.cc

@@ -519,6 +519,9 @@ Http2Upstream::Http2Upstream(ClientHandler *handler)
   callbacks.on_unknown_frame_recv_callback = on_unknown_frame_recv_callback;
   callbacks.on_header_callback = on_header_callback;
   callbacks.on_begin_headers_callback = on_begin_headers_callback;
+  if(get_config()->padding) {
+    callbacks.select_padding_callback = http::select_padding_callback;
+  }
 
   nghttp2_opt_set opt_set;
   opt_set.no_auto_stream_window_update = 1;