basic url previews

Signed-off-by: Rudraksh Pareek <54525605+DelusionalOptimist@users.noreply.github.com>

mediaapi/routing/preview_url.go

@@ -0,0 +1,400 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// 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 routing
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"path"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.org/x/net/html"
+
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/mediaapi/fileutils"
+	"github.com/matrix-org/dendrite/mediaapi/storage"
+	"github.com/matrix-org/dendrite/mediaapi/types"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/util"
+	log "github.com/sirupsen/logrus"
+)
+
+// the parameters included in the incoming preview_url request
+type PreviewUrlRequest struct {
+	url url.URL
+	ts  types.UnixMs
+}
+
+// metadata of the url (media/html) to be previewed
+type mediaInfo struct {
+	MediaMetadata *types.MediaMetadata
+	Logger        *log.Entry
+}
+
+// PreviewUrlResponse defines the format of the JSON response
+// https://matrix.org/docs/spec/client_server/latest#get-matrix-media-r0-preview-url
+// TODO: add more fields to the response
+type PreviewUrlResponse struct {
+	MatrixImageSize int64  `json:"matrix:image:size"`
+	OgImage         string `json:"og:image"`
+	OgSiteName      string `json:"og:site_name"`
+	OgType          string `json:"og:type"`
+	OgTitle         string `json:"og:title"`
+	OgUrl           string `json:"og:url"`
+	OgDescription   string `json:"og:description"`
+}
+
+// PreviewUrl implements GET /preview_url.
+// Current implementation gets the url, parses the meta tags to obtain OG
+// data and returns a JSONResponse for the client to process.
+// TODO: avoid this endpoint in encrypted rooms
+func PreviewUrl(
+	req *http.Request, cfg *config.MediaAPI, db storage.Database) util.JSONResponse {
+
+	// parsing the request
+	r, err := parseRequest(req)
+	if err != nil {
+		return *err
+	}
+
+	// downloading metadata for the url
+	mediaInfo, err := r.downloadUrl(cfg, req.Context(), db)
+	if err != nil {
+		return *err
+	}
+
+	// preparing the response
+	response, err := mediaInfo.prepareResponse(cfg)
+	if err != nil {
+		return *err
+	}
+
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: response,
+	}
+}
+
+// parseRequest parses the incoming preview request to extract the url and ts.
+// Returns either a parsed PreviewUrlRequest or error formatted as
+// util.JSONResponse
+func parseRequest(req *http.Request) (*PreviewUrlRequest, *util.JSONResponse) {
+
+	// get the url to be previewed from the request
+	urlToPreview := req.URL.Query().Get("url")
+	if len(urlToPreview) == 0 {
+		return nil, &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.MissingArgument("Missing URL"),
+		}
+	}
+
+	// parse the url
+	parsedUrl, err := url.Parse(urlToPreview)
+	if err != nil {
+		return nil, &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.InvalidArgumentValue(
+				"Unable to parse url " + err.Error()),
+		}
+	}
+
+	// get the ts if provided in the request
+	if tsStr := req.URL.Query().Get("ts"); len(tsStr) > 0 {
+		ts, err := strconv.ParseInt(tsStr, 10, 64)
+		if err != nil {
+			return nil, &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidArgumentValue(
+					"Couldn't parse 'ts' to a valid integer" + err.Error()),
+			}
+		}
+
+		request := &PreviewUrlRequest{
+			url: *parsedUrl,
+			// Convert timestamp to ms
+			ts: types.UnixMs(ts / 1000000),
+		}
+
+		return request, nil
+	}
+
+	// set ts to current time if none provided
+	ts := time.Now().UnixNano()
+
+	request := &PreviewUrlRequest{
+		url: *parsedUrl,
+		ts:  types.UnixMs(ts / 1000000),
+	}
+
+	return request, nil
+}
+
+// downloadUrl downloads the url and saves the response body.
+// Returns either mediaInfo (metadata about the file to preview) or error
+// formatted as util.JSONResponse.
+// Current implementation for saving response is heavily similar to /upload,
+// need to work on this.
+// TODO: better logging
+func (previewReq *PreviewUrlRequest) downloadUrl(cfg *config.MediaAPI, ctx context.Context, db storage.Database) (*mediaInfo, *util.JSONResponse) {
+
+	urlString := previewReq.url.String()
+
+	// Get the URL
+	response, err := http.Get(urlString)
+	if err != nil {
+		return nil, &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.InvalidArgumentValue("Couldn't get the URL " + err.Error()),
+		}
+	}
+
+	// TODO: check for other status codes too
+	if response.StatusCode == 404 {
+		return nil, &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.NotFound("Given url returned 404"),
+		}
+	}
+
+	// Save the response body to the temporary dir
+	// TODO: should be a new directory like url_cache maybe and
+	hash, bytesWritten, tmpDir, err := fileutils.WriteTempFile(ctx, response.Body, cfg.AbsBasePath)
+	if err != nil {
+		return nil, &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.Unknown("Failed to store URL response " + err.Error()),
+		}
+	}
+
+	// metadata of the media/webpage to preview
+	urlMetadata := &mediaInfo{
+		MediaMetadata: &types.MediaMetadata{
+			Origin:        cfg.Matrix.ServerName,
+			FileSizeBytes: bytesWritten,
+			Base64Hash:    hash,
+			ContentType:   types.ContentType(response.Header["Content-Type"][0]),
+		},
+		Logger: util.GetLogger(ctx).WithField("Origin", cfg.Matrix.ServerName),
+	}
+
+	// :-\
+	// Look up the media by the file hash. If we already have the file but under a
+	// different media ID then we won't upload the file again - instead we'll just
+	// add a new metadata entry that refers to the same file.
+	existingMetadata, err := db.GetMediaMetadataByHash(
+		ctx, hash, urlMetadata.MediaMetadata.Origin,
+	)
+	if err != nil {
+		fileutils.RemoveDir(tmpDir, urlMetadata.Logger)
+		urlMetadata.Logger.WithError(err).Error("Error querying the database by hash.")
+		resErr := jsonerror.InternalServerError()
+		return nil, &resErr
+	}
+	if existingMetadata != nil {
+		// The file already exists, delete the uploaded temporary file.
+		defer fileutils.RemoveDir(tmpDir, urlMetadata.Logger)
+		// The file already exists. Make a new media ID up for it.
+		mediaID, merr := urlMetadata.generateMediaID(ctx, db)
+		if merr != nil {
+			urlMetadata.Logger.WithError(merr).Error("Failed to generate media ID for existing file")
+			resErr := jsonerror.InternalServerError()
+			return nil, &resErr
+		}
+
+		// Then amend the upload metadata.
+		urlMetadata.MediaMetadata = &types.MediaMetadata{
+			MediaID:           mediaID,
+			Origin:            urlMetadata.MediaMetadata.Origin,
+			ContentType:       urlMetadata.MediaMetadata.ContentType,
+			FileSizeBytes:     urlMetadata.MediaMetadata.FileSizeBytes,
+			CreationTimestamp: urlMetadata.MediaMetadata.CreationTimestamp,
+			UploadName:        urlMetadata.MediaMetadata.UploadName,
+			Base64Hash:        hash,
+			UserID:            urlMetadata.MediaMetadata.UserID,
+		}
+	} else {
+		// The file doesn't exist. Update the request metadata.
+		urlMetadata.MediaMetadata.FileSizeBytes = bytesWritten
+		urlMetadata.MediaMetadata.Base64Hash = hash
+		urlMetadata.MediaMetadata.MediaID, err = urlMetadata.generateMediaID(ctx, db)
+		if err != nil {
+			fileutils.RemoveDir(tmpDir, urlMetadata.Logger)
+			urlMetadata.Logger.WithError(err).Error("Failed to generate media ID for new download")
+			resErr := jsonerror.InternalServerError()
+			return nil, &resErr
+		}
+	}
+
+	urlMetadata.Logger = urlMetadata.Logger.WithField("media_id", urlMetadata.MediaMetadata.MediaID)
+	urlMetadata.Logger.WithFields(log.Fields{
+		"Base64Hash":    urlMetadata.MediaMetadata.Base64Hash,
+		"UploadName":    urlMetadata.MediaMetadata.UploadName,
+		"FileSizeBytes": urlMetadata.MediaMetadata.FileSizeBytes,
+		"ContentType":   urlMetadata.MediaMetadata.ContentType,
+	}).Info("File downloaded")
+
+	if resErr := urlMetadata.storeFileAndMetadata(ctx, tmpDir, cfg.AbsBasePath, db); resErr != nil {
+		return nil, resErr
+	}
+
+	return urlMetadata, nil
+}
+
+func (m *mediaInfo) generateMediaID(ctx context.Context, db storage.Database) (types.MediaID, error) {
+	for {
+		// First try generating a media ID. We'll do this by
+		// generating some random bytes and then hex-encoding.
+		mediaIDBytes := make([]byte, 32)
+		_, err := rand.Read(mediaIDBytes)
+		if err != nil {
+			return "", fmt.Errorf("rand.Read: %w", err)
+		}
+		mediaID := types.MediaID(hex.EncodeToString(mediaIDBytes))
+		// Then we will check if this media ID already exists in
+		// our database. If it does then we had best generate a
+		// new one.
+		existingMetadata, err := db.GetMediaMetadata(ctx, mediaID, m.MediaMetadata.Origin)
+		if err != nil {
+			return "", fmt.Errorf("db.GetMediaMetadata: %w", err)
+		}
+		if existingMetadata != nil {
+			// The media ID was already used - repeat the process
+			// and generate a new one instead.
+			continue
+		}
+		// The media ID was not already used - let's return that.
+		return mediaID, nil
+	}
+}
+
+func (r *mediaInfo) storeFileAndMetadata(
+	ctx context.Context,
+	tmpDir types.Path,
+	absBasePath config.Path,
+	db storage.Database,
+) *util.JSONResponse {
+	finalPath, duplicate, err := fileutils.MoveFileWithHashCheck(tmpDir, r.MediaMetadata, absBasePath, r.Logger)
+	if err != nil {
+		r.Logger.WithError(err).Error("Failed to move file.")
+		return &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.Unknown("Failed to upload"),
+		}
+	}
+	if duplicate {
+		r.Logger.WithField("dst", finalPath).Info("File was stored previously - discarding duplicate")
+	}
+
+	if err = db.StoreMediaMetadata(ctx, r.MediaMetadata); err != nil {
+		r.Logger.WithError(err).Warn("Failed to store metadata")
+		// If the file is a duplicate (has the same hash as an existing file) then
+		// there is valid metadata in the database for that file. As such we only
+		// remove the file if it is not a duplicate.
+		if !duplicate {
+			fileutils.RemoveDir(types.Path(path.Dir(string(finalPath))), r.Logger)
+		}
+		return &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.Unknown("Failed to upload"),
+		}
+	}
+
+	return nil
+}
+
+// parseContent returns the data stored in content attributes
+func parseContent(node *html.Node) string {
+	// iterating the attributes of the tag to get content
+	for _, attr := range node.Attr {
+		if attr.Key == "content" {
+			content := attr.Val
+			return content
+		}
+	}
+	return ""
+}
+
+// prepareResponse prepares the response to be returned to the client
+func (mediaInfo *mediaInfo) prepareResponse(cfg *config.MediaAPI) (*PreviewUrlResponse, *util.JSONResponse) {
+
+	// Reading the file in which the response body was stored and parsing the html.
+	pathToFile, err := fileutils.GetPathFromBase64Hash(mediaInfo.MediaMetadata.Base64Hash, cfg.AbsBasePath)
+	if err != nil {
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: jsonerror.Unknown("Couldn't get the path to the stored response" + err.Error()),
+		}
+	}
+
+	fileString, err := ioutil.ReadFile(pathToFile)
+	if err != nil {
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: jsonerror.Unknown("Couldn't read the stored response body" + err.Error()),
+		}
+	}
+
+	file := strings.NewReader(string(fileString))
+
+	tree, err := html.Parse(file)
+	if err != nil {
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: jsonerror.Unknown("Couldn't get the path to the stored file " + err.Error()),
+		}
+	}
+
+	// map for storing the content values
+	m := make(map[string]string)
+
+	// Iterating the *html.Node, looking for og data
+	var f func(*html.Node)
+	f = func(n *html.Node) {
+		//check if meta tag
+		if n.Type == html.ElementNode && n.Data == "meta" {
+			//parse attributes of the tag
+			for _, a := range n.Attr {
+				if a.Key == "property" && strings.HasPrefix(a.Val, "og:") {
+					slice := strings.Split(a.Val, ":")
+					m[slice[1]] = parseContent(n)
+				}
+			}
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			f(c)
+		}
+	}
+
+	f(tree)
+
+	response := &PreviewUrlResponse{
+		OgImage:       m["image"],
+		OgSiteName:    m["site_name"],
+		OgType:        m["type"],
+		OgTitle:       m["title"],
+		OgUrl:         m["url"],
+		OgDescription: m["description"],
+	}
+
+	return response, nil
+}

mediaapi/routing/routing.go

@@ -80,6 +80,12 @@ func Setup(
 			return Config(req, cfg)
 		}),
 	).Methods(http.MethodGet, http.MethodOptions)
+
+	r0mux.Handle("/preview_url",
+		httputil.MakeAuthAPI("preview_url", userAPI, func(req *http.Request, dev *userapi.Device) util.JSONResponse {
+			return PreviewUrl(req, cfg, db)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
 }
 
 func makeDownloadAPI(