nghttpx: Add options for X-Forwarded-Proto header field

This commit adds 2 new options to handle X-Forwarded-Proto header
field.  The --no-add-x-forwarded-proto option makes nghttpx not to
append X-Forwarded-Proto value.  The
--no-strip-incoming-x-forwarded-proto option prevents nghttpx from
stripping the header field from client.

Previously, nghttpx always strips incoming header field, and set its
own header field.  This commit preserves this behaviour, and adds
additional knobs.

gennghttpxfun.py

@@ -164,6 +164,8 @@ OPTIONS = [
     "frontend-max-requests",
     "single-thread",
     "single-process",
+    "no-add-x-forwarded-proto",
+    "no-strip-incoming-x-forwarded-proto",
 ]
 
 LOGVARS = [

src/shrpx.cc

@@ -1478,6 +1478,8 @@ void fill_default_config(Config *config) {
   httpconf.max_response_header_fields = 500;
   httpconf.redirect_https_port = StringRef::from_lit("443");
   httpconf.max_requests = std::numeric_limits<size_t>::max();
+  httpconf.xfp.add = true;
+  httpconf.xfp.strip_incoming = true;
 
   auto &http2conf = config->http2;
   {
@@ -2485,6 +2487,15 @@ HTTP:
   --strip-incoming-x-forwarded-for
               Strip X-Forwarded-For  header field from  inbound client
               requests.
+  --no-add-x-forwarded-proto
+              Don't append  additional X-Forwarded-Proto  header field
+              to  the   backend  request.   If  inbound   client  sets
+              X-Forwarded-Proto,                                   and
+              --no-strip-incoming-x-forwarded-proto  option  is  used,
+              they are passed to the backend.
+  --no-strip-incoming-x-forwarded-proto
+              Don't strip X-Forwarded-Proto  header field from inbound
+              client requests.
   --add-forwarded=<LIST>
               Append RFC  7239 Forwarded header field  with parameters
               specified in comma delimited list <LIST>.  The supported
@@ -3327,6 +3338,9 @@ int main(int argc, char **argv) {
         {SHRPX_OPT_FRONTEND_MAX_REQUESTS.c_str(), required_argument, &flag,
          155},
         {SHRPX_OPT_SINGLE_THREAD.c_str(), no_argument, &flag, 156},
+        {SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO.c_str(), no_argument, &flag, 157},
+        {SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO.c_str(), no_argument,
+         &flag, 158},
         {SHRPX_OPT_SINGLE_PROCESS.c_str(), no_argument, &flag, 159},
         {nullptr, 0, nullptr, 0}};
 
@@ -4064,6 +4078,16 @@ int main(int argc, char **argv) {
         cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_THREAD,
                              StringRef::from_lit("yes"));
         break;
+      case 157:
+        // --no-add-x-forwarded-proto
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO,
+                             StringRef::from_lit("yes"));
+        break;
+      case 158:
+        // --no-strip-incoming-x-forwarded-proto
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO,
+                             StringRef::from_lit("yes"));
+        break;
       case 159:
         // --single-process
         cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_PROCESS,

src/shrpx_config.cc

@@ -1905,6 +1905,11 @@ int option_lookup_token(const char *name, size_t namelen) {
         return SHRPX_OPTID_FETCH_OCSP_RESPONSE_FILE;
       }
       break;
+    case 'o':
+      if (util::strieq_l("no-add-x-forwarded-prot", name, 23)) {
+        return SHRPX_OPTID_NO_ADD_X_FORWARDED_PROTO;
+      }
+      break;
     case 't':
       if (util::strieq_l("listener-disable-timeou", name, 23)) {
         return SHRPX_OPTID_LISTENER_DISABLE_TIMEOUT;
@@ -2101,6 +2106,11 @@ int option_lookup_token(const char *name, size_t namelen) {
         return SHRPX_OPTID_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE;
       }
       break;
+    case 'o':
+      if (util::strieq_l("no-strip-incoming-x-forwarded-prot", name, 34)) {
+        return SHRPX_OPTID_NO_STRIP_INCOMING_X_FORWARDED_PROTO;
+      }
+      break;
     case 'r':
       if (util::strieq_l("frontend-http2-dump-response-heade", name, 34)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER;
@@ -3363,6 +3373,14 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_SINGLE_PROCESS:
     config->single_process = util::strieq_l("yes", optarg);
 
+    return 0;
+  case SHRPX_OPTID_NO_ADD_X_FORWARDED_PROTO:
+    config->http.xfp.add = !util::strieq_l("yes", optarg);
+
+    return 0;
+  case SHRPX_OPTID_NO_STRIP_INCOMING_X_FORWARDED_PROTO:
+    config->http.xfp.strip_incoming = !util::strieq_l("yes", optarg);
+
     return 0;
   case SHRPX_OPTID_CONF:
     LOG(WARN) << "conf: ignored";

src/shrpx_config.h

@@ -337,6 +337,10 @@ constexpr auto SHRPX_OPT_FRONTEND_MAX_REQUESTS =
     StringRef::from_lit("frontend-max-requests");
 constexpr auto SHRPX_OPT_SINGLE_THREAD = StringRef::from_lit("single-thread");
 constexpr auto SHRPX_OPT_SINGLE_PROCESS = StringRef::from_lit("single-process");
+constexpr auto SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO =
+    StringRef::from_lit("no-add-x-forwarded-proto");
+constexpr auto SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO =
+    StringRef::from_lit("no-strip-incoming-x-forwarded-proto");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -639,6 +643,10 @@ struct HttpConfig {
     bool add;
     bool strip_incoming;
   } xff;
+  struct {
+    bool add;
+    bool strip_incoming;
+  } xfp;
   std::vector<AltSvc> altsvcs;
   std::vector<ErrorPage> error_pages;
   HeaderRefs add_request_headers;
@@ -1023,6 +1031,7 @@ enum {
   SHRPX_OPTID_MAX_REQUEST_HEADER_FIELDS,
   SHRPX_OPTID_MAX_RESPONSE_HEADER_FIELDS,
   SHRPX_OPTID_MRUBY_FILE,
+  SHRPX_OPTID_NO_ADD_X_FORWARDED_PROTO,
   SHRPX_OPTID_NO_HOST_REWRITE,
   SHRPX_OPTID_NO_HTTP2_CIPHER_BLACK_LIST,
   SHRPX_OPTID_NO_KQUEUE,
@@ -1030,6 +1039,7 @@ enum {
   SHRPX_OPTID_NO_OCSP,
   SHRPX_OPTID_NO_SERVER_PUSH,
   SHRPX_OPTID_NO_SERVER_REWRITE,
+  SHRPX_OPTID_NO_STRIP_INCOMING_X_FORWARDED_PROTO,
   SHRPX_OPTID_NO_VIA,
   SHRPX_OPTID_NPN_LIST,
   SHRPX_OPTID_OCSP_UPDATE_INTERVAL,

src/shrpx_http2_downstream_connection.cc

@@ -371,8 +371,24 @@ int Http2DownstreamConnection::push_request_headers() {
   }
 
   if (!config->http2_proxy && req.method != HTTP_CONNECT) {
+    auto &xfpconf = httpconf.xfp;
+    auto xfp = xfpconf.strip_incoming
+                   ? nullptr
+                   : req.fs.header(http2::HD_X_FORWARDED_PROTO);
+
+    if (xfpconf.add) {
+      StringRef xfp_value;
       // We use same protocol with :scheme header field
-    nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-proto", req.scheme));
+      if (xfp) {
+        xfp_value = concat_string_ref(balloc, xfp->value,
+                                      StringRef::from_lit(", "), req.scheme);
+      } else {
+        xfp_value = req.scheme;
+      }
+      nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-proto", xfp_value));
+    } else if (xfp) {
+      nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-proto", xfp->value));
+    }
   }
 
   auto via = req.fs.header(http2::HD_VIA);

src/shrpx_http_downstream_connection.cc

@@ -630,10 +630,25 @@ int HttpDownstreamConnection::push_request_headers() {
     buf->append("\r\n");
   }
   if (!config->http2_proxy && !connect_method) {
+    auto &xfpconf = httpconf.xfp;
+    auto xfp = xfpconf.strip_incoming
+                   ? nullptr
+                   : req.fs.header(http2::HD_X_FORWARDED_PROTO);
+
+    if (xfpconf.add) {
       buf->append("X-Forwarded-Proto: ");
+      if (xfp) {
+        buf->append((*xfp).value);
+        buf->append(", ");
+      }
       assert(!req.scheme.empty());
       buf->append(req.scheme);
       buf->append("\r\n");
+    } else if (xfp) {
+      buf->append("X-Forwarded-Proto: ");
+      buf->append((*xfp).value);
+      buf->append("\r\n");
+    }
   }
   auto via = req.fs.header(http2::HD_VIA);
   if (httpconf.no_via) {