[feature] media: add webp support (#1155)

* media: add webp support

Signed-off-by: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se>

* bump exif-terminator to v0.5.0

Signed-off-by: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se>

Signed-off-by: Sigrid Solveig Haflínudóttir <sigrid@ftrv.se>

vendor/github.com/superseriousbusiness/exif-terminator/jpeg.go

@@ -91,7 +91,7 @@ func (v *jpegVisitor) HandleSegment(segmentMarker byte, _ string, _ int, _ bool)
 	if segmentMarker == jpegstructure.MARKER_EOI {
 		// take account of the last 2 bytes taken up by the EOI
 		eoiLength := 2
-		
+
 		// this is the total file size we will
 		// have written including the EOI
 		willHaveWritten := v.writtenTotalBytes + eoiLength

vendor/github.com/superseriousbusiness/exif-terminator/terminator.go

@@ -43,6 +43,8 @@ func Terminate(in io.Reader, fileSize int, mediaType string) (io.Reader, error)
 	switch mediaType {
 	case "image/jpeg", "jpeg", "jpg":
 		err = terminateJpeg(scanner, pipeWriter, fileSize)
+	case "image/webp", "webp":
+		err = terminateWebp(scanner, pipeWriter)
 	case "image/png", "png":
 		// for pngs we need to skip the header bytes, so read them in
 		// and check we're really dealing with a png here
@@ -86,6 +88,18 @@ func terminateJpeg(scanner *bufio.Scanner, writer io.WriteCloser, expectedFileSi
 	return nil
 }
 
+func terminateWebp(scanner *bufio.Scanner, writer io.WriteCloser) error {
+	v := &webpVisitor{
+		writer: writer,
+	}
+
+	// use the webp visitor's 'split' function, which satisfies the bufio.SplitFunc interface
+	scanner.Split(v.split)
+
+	scanAndClose(scanner, writer)
+	return nil
+}
+
 func terminatePng(scanner *bufio.Scanner, writer io.WriteCloser) error {
 	ps := pngstructure.NewPngSplitter()
 

vendor/github.com/superseriousbusiness/exif-terminator/webp.go

@@ -0,0 +1,101 @@
+/*
+   exif-terminator
+   Copyright (C) 2022 SuperSeriousBusiness admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package terminator
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+const (
+	riffHeaderSize = 4 * 3
+)
+
+var (
+	riffHeader = [4]byte{'R', 'I', 'F', 'F'}
+	webpHeader = [4]byte{'W', 'E', 'B', 'P'}
+	exifFourcc = [4]byte{'E', 'X', 'I', 'F'}
+	xmpFourcc  = [4]byte{'X', 'M', 'P', ' '}
+
+	errNoRiffHeader = errors.New("no RIFF header")
+	errNoWebpHeader = errors.New("not a WEBP file")
+)
+
+type webpVisitor struct {
+	writer     io.Writer
+	doneHeader bool
+}
+
+func fourCC(b []byte) [4]byte {
+	return [4]byte{b[0], b[1], b[2], b[3]}
+}
+
+func (v *webpVisitor) split(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	// parse/write the header first
+	if !v.doneHeader {
+		if len(data) < riffHeaderSize {
+			// need the full header
+			return
+		}
+		if fourCC(data) != riffHeader {
+			err = errNoRiffHeader
+			return
+		}
+		if fourCC(data[8:]) != webpHeader {
+			err = errNoWebpHeader
+			return
+		}
+		if _, err = v.writer.Write(data[:riffHeaderSize]); err != nil {
+			return
+		}
+		advance += riffHeaderSize
+		data = data[riffHeaderSize:]
+		v.doneHeader = true
+	}
+
+	// need enough for fourcc and size
+	if len(data) < 8 {
+		return
+	}
+	size := int64(binary.LittleEndian.Uint32(data[4:]))
+	if (size & 1) != 0 {
+		// odd chunk size - extra padding byte
+		size++
+	}
+	// wait until there is enough
+	if int64(len(data)-8) < size {
+		return
+	}
+
+	fourcc := fourCC(data)
+	rawChunkData := data[8 : 8+size]
+	if fourcc == exifFourcc || fourcc == xmpFourcc {
+		// replace exif/xmp with blank
+		rawChunkData = make([]byte, size)
+	}
+
+	if _, err = v.writer.Write(data[:8]); err == nil {
+		if _, err = v.writer.Write(rawChunkData); err == nil {
+			advance += 8 + int(size)
+		}
+	}
+
+	return
+}