144 lines
3.7 KiB
Go
144 lines
3.7 KiB
Go
// Copyright 2013 The Gorilla Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package handlers
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import (
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"compress/flate"
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"compress/gzip"
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"io"
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"net/http"
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"strings"
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"github.com/felixge/httpsnoop"
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)
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const acceptEncoding string = "Accept-Encoding"
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type compressResponseWriter struct {
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compressor io.Writer
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w http.ResponseWriter
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}
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func (cw *compressResponseWriter) WriteHeader(c int) {
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cw.w.Header().Del("Content-Length")
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cw.w.WriteHeader(c)
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}
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func (cw *compressResponseWriter) Write(b []byte) (int, error) {
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h := cw.w.Header()
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if h.Get("Content-Type") == "" {
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h.Set("Content-Type", http.DetectContentType(b))
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}
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h.Del("Content-Length")
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return cw.compressor.Write(b)
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}
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func (cw *compressResponseWriter) ReadFrom(r io.Reader) (int64, error) {
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return io.Copy(cw.compressor, r)
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}
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type flusher interface {
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Flush() error
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}
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func (cw *compressResponseWriter) Flush() {
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// Flush compressed data if compressor supports it.
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if f, ok := cw.compressor.(flusher); ok {
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_ = f.Flush()
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}
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// Flush HTTP response.
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if f, ok := cw.w.(http.Flusher); ok {
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f.Flush()
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}
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}
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// CompressHandler gzip compresses HTTP responses for clients that support it
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// via the 'Accept-Encoding' header.
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//
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// Compressing TLS traffic may leak the page contents to an attacker if the
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// page contains user input: http://security.stackexchange.com/a/102015/12208
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func CompressHandler(h http.Handler) http.Handler {
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return CompressHandlerLevel(h, gzip.DefaultCompression)
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}
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// CompressHandlerLevel gzip compresses HTTP responses with specified compression level
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// for clients that support it via the 'Accept-Encoding' header.
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//
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// The compression level should be gzip.DefaultCompression, gzip.NoCompression,
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// or any integer value between gzip.BestSpeed and gzip.BestCompression inclusive.
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// gzip.DefaultCompression is used in case of invalid compression level.
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func CompressHandlerLevel(h http.Handler, level int) http.Handler {
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if level < gzip.DefaultCompression || level > gzip.BestCompression {
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level = gzip.DefaultCompression
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}
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const (
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gzipEncoding = "gzip"
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flateEncoding = "deflate"
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)
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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// detect what encoding to use
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var encoding string
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for _, curEnc := range strings.Split(r.Header.Get(acceptEncoding), ",") {
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curEnc = strings.TrimSpace(curEnc)
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if curEnc == gzipEncoding || curEnc == flateEncoding {
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encoding = curEnc
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break
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}
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}
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// always add Accept-Encoding to Vary to prevent intermediate caches corruption
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w.Header().Add("Vary", acceptEncoding)
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// if we weren't able to identify an encoding we're familiar with, pass on the
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// request to the handler and return
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if encoding == "" {
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h.ServeHTTP(w, r)
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return
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}
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if r.Header.Get("Upgrade") != "" {
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h.ServeHTTP(w, r)
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return
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}
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// wrap the ResponseWriter with the writer for the chosen encoding
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var encWriter io.WriteCloser
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if encoding == gzipEncoding {
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encWriter, _ = gzip.NewWriterLevel(w, level)
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} else if encoding == flateEncoding {
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encWriter, _ = flate.NewWriter(w, level)
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}
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defer encWriter.Close()
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w.Header().Set("Content-Encoding", encoding)
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r.Header.Del(acceptEncoding)
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cw := &compressResponseWriter{
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w: w,
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compressor: encWriter,
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}
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w = httpsnoop.Wrap(w, httpsnoop.Hooks{
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Write: func(httpsnoop.WriteFunc) httpsnoop.WriteFunc {
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return cw.Write
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},
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WriteHeader: func(httpsnoop.WriteHeaderFunc) httpsnoop.WriteHeaderFunc {
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return cw.WriteHeader
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},
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Flush: func(httpsnoop.FlushFunc) httpsnoop.FlushFunc {
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return cw.Flush
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},
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ReadFrom: func(rff httpsnoop.ReadFromFunc) httpsnoop.ReadFromFunc {
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return cw.ReadFrom
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},
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})
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h.ServeHTTP(w, r)
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})
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}
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