mirror of
https://github.com/nkanaev/yarr.git
synced 2025-11-09 19:08:57 +00:00
reorganizing content-related packages
This commit is contained in:
Nazar Kanaev
469
src/content/sanitizer/sanitizer.go
Normal file
469
src/content/sanitizer/sanitizer.go
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@@ -0,0 +1,469 @@
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// Copyright 2017 Frédéric Guillot. All rights reserved.
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// Use of this source code is governed by the Apache 2.0
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// license that can be found in the LICENSE file.
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package scraper
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import (
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"bytes"
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"fmt"
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"io"
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"regexp"
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"strconv"
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"strings"
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"github.com/nkanaev/yarr/src/content/htmlutil"
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"golang.org/x/net/html"
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)
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var splitSrcsetRegex = regexp.MustCompile(`,\s+`)
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// Sanitize returns safe HTML.
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func Sanitize(baseURL, input string) string {
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var buffer bytes.Buffer
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var tagStack []string
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var parentTag string
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blacklistedTagDepth := 0
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tokenizer := html.NewTokenizer(bytes.NewBufferString(input))
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for {
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if tokenizer.Next() == html.ErrorToken {
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err := tokenizer.Err()
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if err == io.EOF {
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return buffer.String()
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}
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return ""
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}
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token := tokenizer.Token()
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switch token.Type {
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case html.TextToken:
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if blacklistedTagDepth > 0 {
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continue
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}
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// An iframe element never has fallback content.
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// See https://www.w3.org/TR/2010/WD-html5-20101019/the-iframe-element.html#the-iframe-element
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if parentTag == "iframe" {
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continue
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}
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buffer.WriteString(html.EscapeString(token.Data))
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case html.StartTagToken:
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tagName := token.DataAtom.String()
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parentTag = tagName
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if isValidTag(tagName) {
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attrNames, htmlAttributes := sanitizeAttributes(baseURL, tagName, token.Attr)
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if hasRequiredAttributes(tagName, attrNames) {
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if len(attrNames) > 0 {
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buffer.WriteString("<" + tagName + " " + htmlAttributes + ">")
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} else {
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buffer.WriteString("<" + tagName + ">")
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}
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tagStack = append(tagStack, tagName)
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}
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} else if isBlockedTag(tagName) {
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blacklistedTagDepth++
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}
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case html.EndTagToken:
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tagName := token.DataAtom.String()
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if isValidTag(tagName) && inList(tagName, tagStack) {
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buffer.WriteString(fmt.Sprintf("</%s>", tagName))
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} else if isBlockedTag(tagName) {
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blacklistedTagDepth--
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}
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case html.SelfClosingTagToken:
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tagName := token.DataAtom.String()
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if isValidTag(tagName) {
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attrNames, htmlAttributes := sanitizeAttributes(baseURL, tagName, token.Attr)
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if hasRequiredAttributes(tagName, attrNames) {
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if len(attrNames) > 0 {
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buffer.WriteString("<" + tagName + " " + htmlAttributes + "/>")
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} else {
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buffer.WriteString("<" + tagName + "/>")
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}
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}
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}
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}
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}
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}
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func sanitizeAttributes(baseURL, tagName string, attributes []html.Attribute) ([]string, string) {
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var htmlAttrs, attrNames []string
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for _, attribute := range attributes {
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value := attribute.Val
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if !isValidAttribute(tagName, attribute.Key) {
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continue
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}
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if (tagName == "img" || tagName == "source") && attribute.Key == "srcset" {
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value = sanitizeSrcsetAttr(baseURL, value)
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}
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if isExternalResourceAttribute(attribute.Key) {
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if tagName == "iframe" {
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if isValidIframeSource(baseURL, attribute.Val) {
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value = attribute.Val
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} else {
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continue
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}
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} else if tagName == "img" && attribute.Key == "src" && isValidDataAttribute(attribute.Val) {
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value = attribute.Val
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} else {
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value = htmlutil.AbsoluteUrl(value, baseURL)
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if value == "" {
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continue
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}
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if !hasValidURIScheme(value) || isBlockedResource(value) {
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continue
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}
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}
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}
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attrNames = append(attrNames, attribute.Key)
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htmlAttrs = append(htmlAttrs, fmt.Sprintf(`%s="%s"`, attribute.Key, html.EscapeString(value)))
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}
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extraAttrNames, extraHTMLAttributes := getExtraAttributes(tagName)
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if len(extraAttrNames) > 0 {
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attrNames = append(attrNames, extraAttrNames...)
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htmlAttrs = append(htmlAttrs, extraHTMLAttributes...)
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}
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return attrNames, strings.Join(htmlAttrs, " ")
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}
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func getExtraAttributes(tagName string) ([]string, []string) {
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switch tagName {
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case "a":
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return []string{"rel", "target", "referrerpolicy"}, []string{`rel="noopener noreferrer"`, `target="_blank"`, `referrerpolicy="no-referrer"`}
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case "video", "audio":
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return []string{"controls"}, []string{"controls"}
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case "iframe":
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return []string{"sandbox", "loading"}, []string{`sandbox="allow-scripts allow-same-origin allow-popups"`, `loading="lazy"`}
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case "img":
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return []string{"loading"}, []string{`loading="lazy"`}
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default:
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return nil, nil
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}
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}
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func isValidTag(tagName string) bool {
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for element := range getTagAllowList() {
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if tagName == element {
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return true
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}
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}
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return false
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}
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func isValidAttribute(tagName, attributeName string) bool {
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for element, attributes := range getTagAllowList() {
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if tagName == element {
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if inList(attributeName, attributes) {
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return true
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}
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}
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}
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return false
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}
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func isExternalResourceAttribute(attribute string) bool {
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switch attribute {
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case "src", "href", "poster", "cite":
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return true
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default:
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return false
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}
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}
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func hasRequiredAttributes(tagName string, attributes []string) bool {
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elements := make(map[string][]string)
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elements["a"] = []string{"href"}
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elements["iframe"] = []string{"src"}
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elements["img"] = []string{"src"}
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elements["source"] = []string{"src", "srcset"}
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for element, attrs := range elements {
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if tagName == element {
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for _, attribute := range attributes {
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for _, attr := range attrs {
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if attr == attribute {
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return true
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}
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}
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}
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return false
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}
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}
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return true
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}
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// See https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml
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func hasValidURIScheme(src string) bool {
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whitelist := []string{
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"apt:",
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"bitcoin:",
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"callto:",
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"dav:",
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"davs:",
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"ed2k://",
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"facetime://",
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"feed:",
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"ftp://",
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"geo:",
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"gopher://",
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"git://",
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"http://",
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"https://",
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"irc://",
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"irc6://",
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"ircs://",
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"itms://",
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"itms-apps://",
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"magnet:",
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"mailto:",
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"news:",
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"nntp:",
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"rtmp://",
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"sip:",
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"sips:",
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"skype:",
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"spotify:",
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"ssh://",
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"sftp://",
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"steam://",
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"svn://",
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"svn+ssh://",
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"tel:",
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"webcal://",
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"xmpp:",
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}
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for _, prefix := range whitelist {
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if strings.HasPrefix(src, prefix) {
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return true
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}
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}
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return false
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}
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func isBlockedResource(src string) bool {
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blacklist := []string{
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"feedsportal.com",
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"api.flattr.com",
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"stats.wordpress.com",
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"plus.google.com/share",
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"twitter.com/share",
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"feeds.feedburner.com",
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}
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for _, element := range blacklist {
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if strings.Contains(src, element) {
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return true
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}
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}
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return false
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}
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func isValidIframeSource(baseURL, src string) bool {
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whitelist := []string{
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"bandcamp.com",
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"cdn.embedly.com",
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"invidio.us",
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"player.bilibili.com",
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"player.vimeo.com",
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"soundcloud.com",
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"vk.com",
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"w.soundcloud.com",
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"www.dailymotion.com",
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"www.youtube-nocookie.com",
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"www.youtube.com",
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}
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domain := htmlutil.URLDomain(src)
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// allow iframe from same origin
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if htmlutil.URLDomain(baseURL) == domain {
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return true
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}
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for _, safeDomain := range whitelist {
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if safeDomain == domain {
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return true
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}
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}
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return false
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}
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func getTagAllowList() map[string][]string {
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whitelist := make(map[string][]string)
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whitelist["img"] = []string{"alt", "title", "src", "srcset", "sizes"}
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whitelist["picture"] = []string{}
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whitelist["audio"] = []string{"src"}
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whitelist["video"] = []string{"poster", "height", "width", "src"}
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whitelist["source"] = []string{"src", "type", "srcset", "sizes", "media"}
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whitelist["dt"] = []string{}
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whitelist["dd"] = []string{}
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whitelist["dl"] = []string{}
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whitelist["table"] = []string{}
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whitelist["caption"] = []string{}
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whitelist["thead"] = []string{}
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whitelist["tfooter"] = []string{}
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whitelist["tr"] = []string{}
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whitelist["td"] = []string{"rowspan", "colspan"}
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whitelist["th"] = []string{"rowspan", "colspan"}
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whitelist["h1"] = []string{}
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whitelist["h2"] = []string{}
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whitelist["h3"] = []string{}
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whitelist["h4"] = []string{}
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whitelist["h5"] = []string{}
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whitelist["h6"] = []string{}
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whitelist["strong"] = []string{}
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whitelist["em"] = []string{}
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whitelist["code"] = []string{}
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whitelist["pre"] = []string{}
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whitelist["blockquote"] = []string{}
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whitelist["q"] = []string{"cite"}
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whitelist["p"] = []string{}
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whitelist["ul"] = []string{}
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whitelist["li"] = []string{}
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whitelist["ol"] = []string{}
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whitelist["br"] = []string{}
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whitelist["del"] = []string{}
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whitelist["a"] = []string{"href", "title"}
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whitelist["figure"] = []string{}
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whitelist["figcaption"] = []string{}
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whitelist["cite"] = []string{}
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whitelist["time"] = []string{"datetime"}
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whitelist["abbr"] = []string{"title"}
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whitelist["acronym"] = []string{"title"}
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whitelist["wbr"] = []string{}
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whitelist["dfn"] = []string{}
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whitelist["sub"] = []string{}
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whitelist["sup"] = []string{}
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whitelist["var"] = []string{}
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whitelist["samp"] = []string{}
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whitelist["s"] = []string{}
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whitelist["del"] = []string{}
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whitelist["ins"] = []string{}
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whitelist["kbd"] = []string{}
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whitelist["rp"] = []string{}
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whitelist["rt"] = []string{}
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whitelist["rtc"] = []string{}
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whitelist["ruby"] = []string{}
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whitelist["iframe"] = []string{"width", "height", "frameborder", "src", "allowfullscreen"}
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return whitelist
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}
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func inList(needle string, haystack []string) bool {
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for _, element := range haystack {
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if element == needle {
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return true
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}
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}
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return false
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}
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func isBlockedTag(tagName string) bool {
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blacklist := []string{
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"noscript",
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"script",
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"style",
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}
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for _, element := range blacklist {
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if element == tagName {
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return true
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}
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}
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return false
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}
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/*
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One or more strings separated by commas, indicating possible image sources for the user agent to use.
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Each string is composed of:
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- A URL to an image
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- Optionally, whitespace followed by one of:
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- A width descriptor (a positive integer directly followed by w). The width descriptor is divided by the source size given in the sizes attribute to calculate the effective pixel density.
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- A pixel density descriptor (a positive floating point number directly followed by x).
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*/
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func sanitizeSrcsetAttr(baseURL, value string) string {
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var sanitizedSources []string
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rawSources := splitSrcsetRegex.Split(value, -1)
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for _, rawSource := range rawSources {
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parts := strings.Split(strings.TrimSpace(rawSource), " ")
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nbParts := len(parts)
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if nbParts > 0 {
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sanitizedSource := parts[0]
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if !strings.HasPrefix(parts[0], "data:") {
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sanitizedSource = htmlutil.AbsoluteUrl(parts[0], baseURL)
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if sanitizedSource == "" {
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continue
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}
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}
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if nbParts == 2 && isValidWidthOrDensityDescriptor(parts[1]) {
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sanitizedSource += " " + parts[1]
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}
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sanitizedSources = append(sanitizedSources, sanitizedSource)
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}
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}
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return strings.Join(sanitizedSources, ", ")
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}
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func isValidWidthOrDensityDescriptor(value string) bool {
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if value == "" {
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return false
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}
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lastChar := value[len(value)-1:]
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if lastChar != "w" && lastChar != "x" {
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return false
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}
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_, err := strconv.ParseFloat(value[0:len(value)-1], 32)
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return err == nil
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}
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func isValidDataAttribute(value string) bool {
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var dataAttributeAllowList = []string{
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"data:image/avif",
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"data:image/apng",
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"data:image/png",
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"data:image/svg",
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"data:image/svg+xml",
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"data:image/jpg",
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"data:image/jpeg",
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"data:image/gif",
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"data:image/webp",
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}
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for _, prefix := range dataAttributeAllowList {
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if strings.HasPrefix(value, prefix) {
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return true
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}
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}
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return false
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}
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Reference in New Issue
Block a user