TUN-528: Move cloudflared into a separate repo

vendor/github.com/mholt/caddy/caddyhttp/header/header.go

@@ -0,0 +1,124 @@
+// Copyright 2015 Light Code Labs, LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package header provides middleware that appends headers to
+// requests based on a set of configuration rules that define
+// which routes receive which headers.
+package header
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/mholt/caddy/caddyhttp/httpserver"
+)
+
+// Headers is middleware that adds headers to the responses
+// for requests matching a certain path.
+type Headers struct {
+	Next  httpserver.Handler
+	Rules []Rule
+}
+
+// ServeHTTP implements the httpserver.Handler interface and serves requests,
+// setting headers on the response according to the configured rules.
+func (h Headers) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
+	replacer := httpserver.NewReplacer(r, nil, "")
+	rww := &responseWriterWrapper{
+		ResponseWriterWrapper: &httpserver.ResponseWriterWrapper{ResponseWriter: w},
+	}
+	for _, rule := range h.Rules {
+		if httpserver.Path(r.URL.Path).Matches(rule.Path) {
+			for name := range rule.Headers {
+
+				// One can either delete a header, add multiple values to a header, or simply
+				// set a header.
+
+				if strings.HasPrefix(name, "-") {
+					rww.delHeader(strings.TrimLeft(name, "-"))
+				} else if strings.HasPrefix(name, "+") {
+					for _, value := range rule.Headers[name] {
+						rww.Header().Add(strings.TrimLeft(name, "+"), replacer.Replace(value))
+					}
+				} else {
+					for _, value := range rule.Headers[name] {
+						rww.Header().Set(name, replacer.Replace(value))
+					}
+				}
+			}
+		}
+	}
+	return h.Next.ServeHTTP(rww, r)
+}
+
+type (
+	// Rule groups a slice of HTTP headers by a URL pattern.
+	Rule struct {
+		Path    string
+		Headers http.Header
+	}
+)
+
+// headerOperation represents an operation on the header
+type headerOperation func(http.Header)
+
+// responseWriterWrapper wraps the real ResponseWriter.
+// It defers header operations until writeHeader
+type responseWriterWrapper struct {
+	*httpserver.ResponseWriterWrapper
+	ops         []headerOperation
+	wroteHeader bool
+}
+
+func (rww *responseWriterWrapper) Header() http.Header {
+	return rww.ResponseWriterWrapper.Header()
+}
+
+func (rww *responseWriterWrapper) Write(d []byte) (int, error) {
+	if !rww.wroteHeader {
+		rww.WriteHeader(http.StatusOK)
+	}
+	return rww.ResponseWriterWrapper.Write(d)
+}
+
+func (rww *responseWriterWrapper) WriteHeader(status int) {
+	if rww.wroteHeader {
+		return
+	}
+	rww.wroteHeader = true
+	// capture the original headers
+	h := rww.Header()
+
+	// perform our revisions
+	for _, op := range rww.ops {
+		op(h)
+	}
+
+	rww.ResponseWriterWrapper.WriteHeader(status)
+}
+
+// delHeader deletes the existing header according to the key
+// Also it will delete that header added later.
+func (rww *responseWriterWrapper) delHeader(key string) {
+	// remove the existing one if any
+	rww.Header().Del(key)
+
+	// register a future deletion
+	rww.ops = append(rww.ops, func(h http.Header) {
+		h.Del(key)
+	})
+}
+
+// Interface guards
+var _ httpserver.HTTPInterfaces = (*responseWriterWrapper)(nil)