143 lines
3.6 KiB
Go
143 lines
3.6 KiB
Go
package proxy
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import (
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"context"
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"encoding/base64"
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"io"
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"net/http"
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"strings"
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"time"
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"github.com/PuerkitoBio/goquery"
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"github.com/go-chi/chi"
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log "github.com/go-pkgz/lgr"
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"github.com/go-pkgz/repeater"
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"github.com/pkg/errors"
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"github.com/umputun/remark/backend/app/rest"
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)
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// Image extracts image src from comment's html and provides proxy for them
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// this is needed to keep remark42 running behind of HTTPS serve all images via https
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type Image struct {
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RemarkURL string
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RoutePath string
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Enabled bool
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Timeout time.Duration
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}
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// Convert all img src links without https to proxied links
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func (p Image) Convert(commentHTML string) string {
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if !p.Enabled || strings.HasPrefix(p.RemarkURL, "http://") {
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return commentHTML
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}
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imgs, err := p.extract(commentHTML)
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if err != nil {
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return commentHTML
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}
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return p.replace(commentHTML, imgs)
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}
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// Routes returns router group to respond to proxied request
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func (p Image) Routes() chi.Router {
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router := chi.NewRouter()
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if !p.Enabled {
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return router
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}
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router.Get("/", func(w http.ResponseWriter, r *http.Request) {
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src, err := base64.URLEncoding.DecodeString(r.URL.Query().Get("src"))
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if err != nil {
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rest.SendErrorJSON(w, r, http.StatusBadRequest, err, "can't decode image url")
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return
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}
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timeout := 60 * time.Second // default
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if p.Timeout > 0 {
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timeout = p.Timeout
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}
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ctx, cancel := context.WithTimeout(context.Background(), timeout)
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defer cancel()
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client := http.Client{Timeout: 30 * time.Second}
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var resp *http.Response
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err = repeater.NewDefault(5, time.Second).Do(ctx, func() error {
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var e error
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req, e := http.NewRequest("GET", string(src), nil)
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if e != nil {
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return errors.Wrapf(e, "failed to make request for %s", r.URL.Query().Get("src"))
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}
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resp, e = client.Do(req.WithContext(ctx))
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return e
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})
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if err != nil {
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rest.SendErrorJSON(w, r, http.StatusBadRequest, err, "can't get image "+string(src))
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return
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}
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defer func() {
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if e := resp.Body.Close(); e != nil {
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log.Printf("[WARN] can't close body, %s", e)
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}
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}()
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if resp.StatusCode != http.StatusOK {
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w.WriteHeader(resp.StatusCode)
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return
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}
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for k, v := range resp.Header {
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if strings.EqualFold(k, "Content-Type") {
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w.Header().Set(k, v[0])
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}
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if strings.EqualFold(k, "Content-Length") {
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w.Header().Set(k, v[0])
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}
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}
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// enforce client-side caching
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etag := `"` + r.URL.Query().Get("src") + `"`
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w.Header().Set("Etag", etag)
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w.Header().Set("Cache-Control", "max-age=2592000") // 30 days
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if match := r.Header.Get("If-None-Match"); match != "" {
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if strings.Contains(match, etag) {
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w.WriteHeader(http.StatusNotModified)
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return
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}
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}
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if _, e := io.Copy(w, resp.Body); e != nil {
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log.Printf("[WARN] can't copy image stream, %s", e)
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}
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})
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return router
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}
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// extract gets all non-https images and return list of src
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func (p Image) extract(commentHTML string) ([]string, error) {
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doc, err := goquery.NewDocumentFromReader(strings.NewReader(commentHTML))
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if err != nil {
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return nil, errors.Wrap(err, "can't create document")
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}
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result := []string{}
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doc.Find("img").Each(func(i int, s *goquery.Selection) {
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if im, ok := s.Attr("src"); ok {
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if strings.HasPrefix(im, "http://") {
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result = append(result, im)
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}
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}
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})
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return result, nil
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}
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// replace img links in commentHTML with route to proxy, base64 encoded original link
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func (p Image) replace(commentHTML string, imgs []string) string {
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for _, img := range imgs {
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encodedImgURL := base64.URLEncoding.EncodeToString([]byte(img))
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resImgURL := p.RemarkURL + p.RoutePath + "?src=" + encodedImgURL
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commentHTML = strings.Replace(commentHTML, img, resImgURL, -1)
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}
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return commentHTML
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}
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