242 lines
7.1 KiB
Go
242 lines
7.1 KiB
Go
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/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package proxy
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import (
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"bytes"
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"compress/gzip"
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"fmt"
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"io"
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"io/ioutil"
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"net/http"
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"net/url"
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"path"
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"strings"
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"github.com/golang/glog"
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"golang.org/x/net/html"
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"golang.org/x/net/html/atom"
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"k8s.io/apimachinery/pkg/util/net"
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"k8s.io/apimachinery/pkg/util/sets"
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)
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// atomsToAttrs states which attributes of which tags require URL substitution.
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// Sources: http://www.w3.org/TR/REC-html40/index/attributes.html
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// http://www.w3.org/html/wg/drafts/html/master/index.html#attributes-1
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var atomsToAttrs = map[atom.Atom]sets.String{
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atom.A: sets.NewString("href"),
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atom.Applet: sets.NewString("codebase"),
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atom.Area: sets.NewString("href"),
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atom.Audio: sets.NewString("src"),
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atom.Base: sets.NewString("href"),
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atom.Blockquote: sets.NewString("cite"),
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atom.Body: sets.NewString("background"),
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atom.Button: sets.NewString("formaction"),
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atom.Command: sets.NewString("icon"),
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atom.Del: sets.NewString("cite"),
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atom.Embed: sets.NewString("src"),
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atom.Form: sets.NewString("action"),
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atom.Frame: sets.NewString("longdesc", "src"),
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atom.Head: sets.NewString("profile"),
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atom.Html: sets.NewString("manifest"),
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atom.Iframe: sets.NewString("longdesc", "src"),
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atom.Img: sets.NewString("longdesc", "src", "usemap"),
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atom.Input: sets.NewString("src", "usemap", "formaction"),
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atom.Ins: sets.NewString("cite"),
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atom.Link: sets.NewString("href"),
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atom.Object: sets.NewString("classid", "codebase", "data", "usemap"),
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atom.Q: sets.NewString("cite"),
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atom.Script: sets.NewString("src"),
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atom.Source: sets.NewString("src"),
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atom.Video: sets.NewString("poster", "src"),
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// TODO: css URLs hidden in style elements.
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}
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// Transport is a transport for text/html content that replaces URLs in html
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// content with the prefix of the proxy server
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type Transport struct {
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Scheme string
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Host string
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PathPrepend string
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http.RoundTripper
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}
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// RoundTrip implements the http.RoundTripper interface
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func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
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// Add reverse proxy headers.
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forwardedURI := path.Join(t.PathPrepend, req.URL.Path)
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if strings.HasSuffix(req.URL.Path, "/") {
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forwardedURI = forwardedURI + "/"
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}
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req.Header.Set("X-Forwarded-Uri", forwardedURI)
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if len(t.Host) > 0 {
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req.Header.Set("X-Forwarded-Host", t.Host)
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}
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if len(t.Scheme) > 0 {
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req.Header.Set("X-Forwarded-Proto", t.Scheme)
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}
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rt := t.RoundTripper
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if rt == nil {
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rt = http.DefaultTransport
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}
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resp, err := rt.RoundTrip(req)
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if err != nil {
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message := fmt.Sprintf("Error: '%s'\nTrying to reach: '%v'", err.Error(), req.URL.String())
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resp = &http.Response{
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StatusCode: http.StatusServiceUnavailable,
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Body: ioutil.NopCloser(strings.NewReader(message)),
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}
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return resp, nil
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}
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if redirect := resp.Header.Get("Location"); redirect != "" {
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resp.Header.Set("Location", t.rewriteURL(redirect, req.URL))
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return resp, nil
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}
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cType := resp.Header.Get("Content-Type")
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cType = strings.TrimSpace(strings.SplitN(cType, ";", 2)[0])
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if cType != "text/html" {
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// Do nothing, simply pass through
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return resp, nil
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}
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return t.rewriteResponse(req, resp)
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}
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var _ = net.RoundTripperWrapper(&Transport{})
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func (rt *Transport) WrappedRoundTripper() http.RoundTripper {
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return rt.RoundTripper
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}
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// rewriteURL rewrites a single URL to go through the proxy, if the URL refers
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// to the same host as sourceURL, which is the page on which the target URL
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// occurred. If any error occurs (e.g. parsing), it returns targetURL.
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func (t *Transport) rewriteURL(targetURL string, sourceURL *url.URL) string {
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url, err := url.Parse(targetURL)
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if err != nil {
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return targetURL
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}
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isDifferentHost := url.Host != "" && url.Host != sourceURL.Host
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isRelative := !strings.HasPrefix(url.Path, "/")
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if isDifferentHost || isRelative {
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return targetURL
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}
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url.Scheme = t.Scheme
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url.Host = t.Host
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origPath := url.Path
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// Do not rewrite URL if the sourceURL already contains the necessary prefix.
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if strings.HasPrefix(url.Path, t.PathPrepend) {
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return url.String()
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}
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url.Path = path.Join(t.PathPrepend, url.Path)
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if strings.HasSuffix(origPath, "/") {
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// Add back the trailing slash, which was stripped by path.Join().
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url.Path += "/"
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}
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return url.String()
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}
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// rewriteHTML scans the HTML for tags with url-valued attributes, and updates
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// those values with the urlRewriter function. The updated HTML is output to the
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// writer.
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func rewriteHTML(reader io.Reader, writer io.Writer, urlRewriter func(string) string) error {
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// Note: This assumes the content is UTF-8.
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tokenizer := html.NewTokenizer(reader)
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var err error
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for err == nil {
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tokenType := tokenizer.Next()
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switch tokenType {
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case html.ErrorToken:
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err = tokenizer.Err()
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case html.StartTagToken, html.SelfClosingTagToken:
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token := tokenizer.Token()
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if urlAttrs, ok := atomsToAttrs[token.DataAtom]; ok {
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for i, attr := range token.Attr {
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if urlAttrs.Has(attr.Key) {
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token.Attr[i].Val = urlRewriter(attr.Val)
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}
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}
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}
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_, err = writer.Write([]byte(token.String()))
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default:
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_, err = writer.Write(tokenizer.Raw())
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}
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}
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if err != io.EOF {
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return err
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}
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return nil
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}
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// rewriteResponse modifies an HTML response by updating absolute links referring
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// to the original host to instead refer to the proxy transport.
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func (t *Transport) rewriteResponse(req *http.Request, resp *http.Response) (*http.Response, error) {
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origBody := resp.Body
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defer origBody.Close()
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newContent := &bytes.Buffer{}
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var reader io.Reader = origBody
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var writer io.Writer = newContent
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encoding := resp.Header.Get("Content-Encoding")
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switch encoding {
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case "gzip":
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var err error
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reader, err = gzip.NewReader(reader)
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if err != nil {
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return nil, fmt.Errorf("errorf making gzip reader: %v", err)
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}
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gzw := gzip.NewWriter(writer)
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defer gzw.Close()
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writer = gzw
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// TODO: support flate, other encodings.
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case "":
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// This is fine
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default:
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// Some encoding we don't understand-- don't try to parse this
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glog.Errorf("Proxy encountered encoding %v for text/html; can't understand this so not fixing links.", encoding)
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return resp, nil
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}
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urlRewriter := func(targetUrl string) string {
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return t.rewriteURL(targetUrl, req.URL)
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}
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err := rewriteHTML(reader, writer, urlRewriter)
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if err != nil {
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glog.Errorf("Failed to rewrite URLs: %v", err)
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return resp, err
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}
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resp.Body = ioutil.NopCloser(newContent)
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// Update header node with new content-length
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// TODO: Remove any hash/signature headers here?
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resp.Header.Del("Content-Length")
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resp.ContentLength = int64(newContent.Len())
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return resp, err
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}
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