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

This commit adds 2 new options to handle X-Forwarded-Proto header
field.  The --add-x-forwarded-proto option makes nghttpx append
X-Forwarded-Proto value.  The --strip-incoming-x-forwarded-proto
option makes nghttpx to strip the header field from client.

Previously, nghttpx always strips incoming header field, and set its
own header field.  This commit changes this behaviour.  Now nghttpx
does not strip, and append X-Forwarded-Proto header field by default.
The X-Forwarded-For, and Forwarded header fields are also handled in
the same way.  To recover the old behaviour, use
--add-x-forwarded-proto and --strip-incoming-x-forwarded-proto
options.

gennghttpxfun.py

@@ -163,6 +163,8 @@ OPTIONS = [
     "redirect-https-port",
     "frontend-max-requests",
     "single-thread",
+    "no-add-x-forwarded-proto",
+    "strip-incoming-x-forwarded-proto",
 ]
 
 LOGVARS = [

src/shrpx.cc

@@ -2466,6 +2466,12 @@ HTTP:
   --strip-incoming-x-forwarded-for
               Strip X-Forwarded-For  header field from  inbound client
               requests.
+  --add-x-forwarded-proto
+              Append  X-Forwarded-Proto header  field  to the  backend
+              request.
+  --strip-incoming-x-forwarded-proto
+              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
@@ -3300,6 +3306,9 @@ 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_ADD_X_FORWARDED_PROTO.c_str(), no_argument, &flag, 157},
+        {SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_PROTO.c_str(), no_argument, &flag,
+         158},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -4036,6 +4045,16 @@ int main(int argc, char **argv) {
         cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_THREAD,
                              StringRef::from_lit("yes"));
         break;
+      case 157:
+        // --add-x-forwarded-proto
+        cmdcfgs.emplace_back(SHRPX_OPT_ADD_X_FORWARDED_PROTO,
+                             StringRef::from_lit("yes"));
+        break;
+      case 158:
+        // --strip-incoming-x-forwarded-proto
+        cmdcfgs.emplace_back(SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_PROTO,
+                             StringRef::from_lit("yes"));
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -1816,6 +1816,11 @@ int option_lookup_token(const char *name, size_t namelen) {
         return SHRPX_OPTID_TLS_MIN_PROTO_VERSION;
       }
       break;
+    case 'o':
+      if (util::strieq_l("add-x-forwarded-prot", name, 20)) {
+        return SHRPX_OPTID_ADD_X_FORWARDED_PROTO;
+      }
+      break;
     case 'r':
       if (util::strieq_l("tls-ticket-key-ciphe", name, 20)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_CIPHER;
@@ -2048,6 +2053,11 @@ int option_lookup_token(const char *name, size_t namelen) {
         return SHRPX_OPTID_BACKEND_CONNECTIONS_PER_FRONTEND;
       }
       break;
+    case 'o':
+      if (util::strieq_l("strip-incoming-x-forwarded-prot", name, 31)) {
+        return SHRPX_OPTID_STRIP_INCOMING_X_FORWARDED_PROTO;
+      }
+      break;
     }
     break;
   case 33:
@@ -3356,6 +3366,14 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_SINGLE_THREAD:
     config->single_thread = util::strieq_l("yes", optarg);
 
+    return 0;
+  case SHRPX_OPTID_ADD_X_FORWARDED_PROTO:
+    config->http.xfp.add = util::strieq_l("yes", optarg);
+
+    return 0;
+  case SHRPX_OPTID_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

@@ -336,6 +336,10 @@ constexpr auto SHRPX_OPT_REDIRECT_HTTPS_PORT =
 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_ADD_X_FORWARDED_PROTO =
+    StringRef::from_lit("add-x-forwarded-proto");
+constexpr auto SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_PROTO =
+    StringRef::from_lit("strip-incoming-x-forwarded-proto");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -638,6 +642,10 @@ 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;
@@ -928,6 +936,7 @@ enum {
   SHRPX_OPTID_ADD_REQUEST_HEADER,
   SHRPX_OPTID_ADD_RESPONSE_HEADER,
   SHRPX_OPTID_ADD_X_FORWARDED_FOR,
+  SHRPX_OPTID_ADD_X_FORWARDED_PROTO,
   SHRPX_OPTID_ALTSVC,
   SHRPX_OPTID_API_MAX_REQUEST_BODY,
   SHRPX_OPTID_BACKEND,
@@ -1045,6 +1054,7 @@ enum {
   SHRPX_OPTID_STREAM_WRITE_TIMEOUT,
   SHRPX_OPTID_STRIP_INCOMING_FORWARDED,
   SHRPX_OPTID_STRIP_INCOMING_X_FORWARDED_FOR,
+  SHRPX_OPTID_STRIP_INCOMING_X_FORWARDED_PROTO,
   SHRPX_OPTID_SUBCERT,
   SHRPX_OPTID_SYSLOG_FACILITY,
   SHRPX_OPTID_TLS_DYN_REC_IDLE_TIMEOUT,

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) {