forked from gitea/gitea
144 lines
4.3 KiB
Go
144 lines
4.3 KiB
Go
// Copyright 2021 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package typesniffer
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import (
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"bytes"
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"fmt"
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"io"
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"net/http"
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"regexp"
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"strings"
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"code.gitea.io/gitea/modules/util"
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)
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// Use at most this many bytes to determine Content Type.
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const sniffLen = 1024
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const (
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// SvgMimeType MIME type of SVG images.
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SvgMimeType = "image/svg+xml"
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// ApplicationOctetStream MIME type of binary files.
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ApplicationOctetStream = "application/octet-stream"
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)
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var (
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svgComment = regexp.MustCompile(`(?s)<!--.*?-->`)
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svgTagRegex = regexp.MustCompile(`(?si)\A\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
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svgTagInXMLRegex = regexp.MustCompile(`(?si)\A<\?xml\b.*?\?>\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
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)
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// SniffedType contains information about a blobs type.
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type SniffedType struct {
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contentType string
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}
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// IsText etects if content format is plain text.
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func (ct SniffedType) IsText() bool {
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return strings.Contains(ct.contentType, "text/")
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}
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// IsImage detects if data is an image format
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func (ct SniffedType) IsImage() bool {
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return strings.Contains(ct.contentType, "image/")
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}
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// IsSvgImage detects if data is an SVG image format
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func (ct SniffedType) IsSvgImage() bool {
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return strings.Contains(ct.contentType, SvgMimeType)
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}
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// IsPDF detects if data is a PDF format
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func (ct SniffedType) IsPDF() bool {
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return strings.Contains(ct.contentType, "application/pdf")
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}
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// IsVideo detects if data is an video format
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func (ct SniffedType) IsVideo() bool {
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return strings.Contains(ct.contentType, "video/")
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}
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// IsAudio detects if data is an video format
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func (ct SniffedType) IsAudio() bool {
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return strings.Contains(ct.contentType, "audio/")
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}
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// IsRepresentableAsText returns true if file content can be represented as
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// plain text or is empty.
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func (ct SniffedType) IsRepresentableAsText() bool {
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return ct.IsText() || ct.IsSvgImage()
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}
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// IsBrowsableBinaryType returns whether a non-text type can be displayed in a browser
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func (ct SniffedType) IsBrowsableBinaryType() bool {
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return ct.IsImage() || ct.IsSvgImage() || ct.IsPDF() || ct.IsVideo() || ct.IsAudio()
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}
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// GetMimeType returns the mime type
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func (ct SniffedType) GetMimeType() string {
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return strings.SplitN(ct.contentType, ";", 2)[0]
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}
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// DetectContentType extends http.DetectContentType with more content types. Defaults to text/unknown if input is empty.
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func DetectContentType(data []byte) SniffedType {
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if len(data) == 0 {
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return SniffedType{"text/unknown"}
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}
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ct := http.DetectContentType(data)
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if len(data) > sniffLen {
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data = data[:sniffLen]
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}
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// SVG is unsupported by http.DetectContentType, https://github.com/golang/go/issues/15888
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detectByHTML := strings.Contains(ct, "text/plain") || strings.Contains(ct, "text/html")
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detectByXML := strings.Contains(ct, "text/xml")
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if detectByHTML || detectByXML {
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dataProcessed := svgComment.ReplaceAll(data, nil)
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dataProcessed = bytes.TrimSpace(dataProcessed)
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if detectByHTML && svgTagRegex.Match(dataProcessed) ||
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detectByXML && svgTagInXMLRegex.Match(dataProcessed) {
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ct = SvgMimeType
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}
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}
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if strings.HasPrefix(ct, "audio/") && bytes.HasPrefix(data, []byte("ID3")) {
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// The MP3 detection is quite inaccurate, any content with "ID3" prefix will result in "audio/mpeg".
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// So remove the "ID3" prefix and detect again, if result is text, then it must be text content.
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// This works especially because audio files contain many unprintable/invalid characters like `0x00`
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ct2 := http.DetectContentType(data[3:])
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if strings.HasPrefix(ct2, "text/") {
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ct = ct2
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}
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}
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if ct == "application/ogg" {
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dataHead := data
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if len(dataHead) > 256 {
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dataHead = dataHead[:256] // only need to do a quick check for the file header
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}
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if bytes.Contains(dataHead, []byte("theora")) || bytes.Contains(dataHead, []byte("dirac")) {
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ct = "video/ogg" // ogg is only used for some video formats, and it's not popular
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} else {
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ct = "audio/ogg" // for most cases, it is used as an audio container
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}
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}
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return SniffedType{ct}
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}
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// DetectContentTypeFromReader guesses the content type contained in the reader.
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func DetectContentTypeFromReader(r io.Reader) (SniffedType, error) {
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buf := make([]byte, sniffLen)
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n, err := util.ReadAtMost(r, buf)
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if err != nil {
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return SniffedType{}, fmt.Errorf("DetectContentTypeFromReader io error: %w", err)
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}
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buf = buf[:n]
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return DetectContentType(buf), nil
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}
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