reorganizing content-related packages

2026-03-26 21:57:42 +00:00 · 2021-03-31 23:40:59 +01:00
parent 0b8bf50204
commit b04e8c1e93
12 changed files with 19 additions and 18 deletions
--- a/src/content/sanitizer/sanitizer.go
+++ b/src/content/sanitizer/sanitizer.go
@@ -0,0 +1,469 @@
+// Copyright 2017 Frédéric Guillot. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package scraper
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/nkanaev/yarr/src/content/htmlutil"
+	"golang.org/x/net/html"
+)
+
+var splitSrcsetRegex = regexp.MustCompile(`,\s+`)
+
+// Sanitize returns safe HTML.
+func Sanitize(baseURL, input string) string {
+	var buffer bytes.Buffer
+	var tagStack []string
+	var parentTag string
+	blacklistedTagDepth := 0
+
+	tokenizer := html.NewTokenizer(bytes.NewBufferString(input))
+	for {
+		if tokenizer.Next() == html.ErrorToken {
+			err := tokenizer.Err()
+			if err == io.EOF {
+				return buffer.String()
+			}
+
+			return ""
+		}
+
+		token := tokenizer.Token()
+		switch token.Type {
+		case html.TextToken:
+			if blacklistedTagDepth > 0 {
+				continue
+			}
+
+			// An iframe element never has fallback content.
+			// See https://www.w3.org/TR/2010/WD-html5-20101019/the-iframe-element.html#the-iframe-element
+			if parentTag == "iframe" {
+				continue
+			}
+
+			buffer.WriteString(html.EscapeString(token.Data))
+		case html.StartTagToken:
+			tagName := token.DataAtom.String()
+			parentTag = tagName
+
+			if isValidTag(tagName) {
+				attrNames, htmlAttributes := sanitizeAttributes(baseURL, tagName, token.Attr)
+
+				if hasRequiredAttributes(tagName, attrNames) {
+					if len(attrNames) > 0 {
+						buffer.WriteString("<" + tagName + " " + htmlAttributes + ">")
+					} else {
+						buffer.WriteString("<" + tagName + ">")
+					}
+
+					tagStack = append(tagStack, tagName)
+				}
+			} else if isBlockedTag(tagName) {
+				blacklistedTagDepth++
+			}
+		case html.EndTagToken:
+			tagName := token.DataAtom.String()
+			if isValidTag(tagName) && inList(tagName, tagStack) {
+				buffer.WriteString(fmt.Sprintf("</%s>", tagName))
+			} else if isBlockedTag(tagName) {
+				blacklistedTagDepth--
+			}
+		case html.SelfClosingTagToken:
+			tagName := token.DataAtom.String()
+			if isValidTag(tagName) {
+				attrNames, htmlAttributes := sanitizeAttributes(baseURL, tagName, token.Attr)
+
+				if hasRequiredAttributes(tagName, attrNames) {
+					if len(attrNames) > 0 {
+						buffer.WriteString("<" + tagName + " " + htmlAttributes + "/>")
+					} else {
+						buffer.WriteString("<" + tagName + "/>")
+					}
+				}
+			}
+		}
+	}
+}
+
+func sanitizeAttributes(baseURL, tagName string, attributes []html.Attribute) ([]string, string) {
+	var htmlAttrs, attrNames []string
+
+	for _, attribute := range attributes {
+		value := attribute.Val
+
+		if !isValidAttribute(tagName, attribute.Key) {
+			continue
+		}
+
+		if (tagName == "img" || tagName == "source") && attribute.Key == "srcset" {
+			value = sanitizeSrcsetAttr(baseURL, value)
+		}
+
+		if isExternalResourceAttribute(attribute.Key) {
+			if tagName == "iframe" {
+				if isValidIframeSource(baseURL, attribute.Val) {
+					value = attribute.Val
+				} else {
+					continue
+				}
+			} else if tagName == "img" && attribute.Key == "src" && isValidDataAttribute(attribute.Val) {
+				value = attribute.Val
+			} else {
+				value = htmlutil.AbsoluteUrl(value, baseURL)
+				if value == "" {
+					continue
+				}
+
+				if !hasValidURIScheme(value) || isBlockedResource(value) {
+					continue
+				}
+			}
+		}
+
+		attrNames = append(attrNames, attribute.Key)
+		htmlAttrs = append(htmlAttrs, fmt.Sprintf(`%s="%s"`, attribute.Key, html.EscapeString(value)))
+	}
+
+	extraAttrNames, extraHTMLAttributes := getExtraAttributes(tagName)
+	if len(extraAttrNames) > 0 {
+		attrNames = append(attrNames, extraAttrNames...)
+		htmlAttrs = append(htmlAttrs, extraHTMLAttributes...)
+	}
+
+	return attrNames, strings.Join(htmlAttrs, " ")
+}
+
+func getExtraAttributes(tagName string) ([]string, []string) {
+	switch tagName {
+	case "a":
+		return []string{"rel", "target", "referrerpolicy"}, []string{`rel="noopener noreferrer"`, `target="_blank"`, `referrerpolicy="no-referrer"`}
+	case "video", "audio":
+		return []string{"controls"}, []string{"controls"}
+	case "iframe":
+		return []string{"sandbox", "loading"}, []string{`sandbox="allow-scripts allow-same-origin allow-popups"`, `loading="lazy"`}
+	case "img":
+		return []string{"loading"}, []string{`loading="lazy"`}
+	default:
+		return nil, nil
+	}
+}
+
+func isValidTag(tagName string) bool {
+	for element := range getTagAllowList() {
+		if tagName == element {
+			return true
+		}
+	}
+
+	return false
+}
+
+func isValidAttribute(tagName, attributeName string) bool {
+	for element, attributes := range getTagAllowList() {
+		if tagName == element {
+			if inList(attributeName, attributes) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+func isExternalResourceAttribute(attribute string) bool {
+	switch attribute {
+	case "src", "href", "poster", "cite":
+		return true
+	default:
+		return false
+	}
+}
+
+func hasRequiredAttributes(tagName string, attributes []string) bool {
+	elements := make(map[string][]string)
+	elements["a"] = []string{"href"}
+	elements["iframe"] = []string{"src"}
+	elements["img"] = []string{"src"}
+	elements["source"] = []string{"src", "srcset"}
+
+	for element, attrs := range elements {
+		if tagName == element {
+			for _, attribute := range attributes {
+				for _, attr := range attrs {
+					if attr == attribute {
+						return true
+					}
+				}
+			}
+
+			return false
+		}
+	}
+
+	return true
+}
+
+// See https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml
+func hasValidURIScheme(src string) bool {
+	whitelist := []string{
+		"apt:",
+		"bitcoin:",
+		"callto:",
+		"dav:",
+		"davs:",
+		"ed2k://",
+		"facetime://",
+		"feed:",
+		"ftp://",
+		"geo:",
+		"gopher://",
+		"git://",
+		"http://",
+		"https://",
+		"irc://",
+		"irc6://",
+		"ircs://",
+		"itms://",
+		"itms-apps://",
+		"magnet:",
+		"mailto:",
+		"news:",
+		"nntp:",
+		"rtmp://",
+		"sip:",
+		"sips:",
+		"skype:",
+		"spotify:",
+		"ssh://",
+		"sftp://",
+		"steam://",
+		"svn://",
+		"svn+ssh://",
+		"tel:",
+		"webcal://",
+		"xmpp:",
+	}
+
+	for _, prefix := range whitelist {
+		if strings.HasPrefix(src, prefix) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func isBlockedResource(src string) bool {
+	blacklist := []string{
+		"feedsportal.com",
+		"api.flattr.com",
+		"stats.wordpress.com",
+		"plus.google.com/share",
+		"twitter.com/share",
+		"feeds.feedburner.com",
+	}
+
+	for _, element := range blacklist {
+		if strings.Contains(src, element) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func isValidIframeSource(baseURL, src string) bool {
+	whitelist := []string{
+		"bandcamp.com",
+		"cdn.embedly.com",
+		"invidio.us",
+		"player.bilibili.com",
+		"player.vimeo.com",
+		"soundcloud.com",
+		"vk.com",
+		"w.soundcloud.com",
+		"www.dailymotion.com",
+		"www.youtube-nocookie.com",
+		"www.youtube.com",
+	}
+
+	domain := htmlutil.URLDomain(src)
+	// allow iframe from same origin
+	if htmlutil.URLDomain(baseURL) == domain {
+		return true
+	}
+
+	for _, safeDomain := range whitelist {
+		if safeDomain == domain {
+			return true
+		}
+	}
+
+	return false
+}
+
+func getTagAllowList() map[string][]string {
+	whitelist := make(map[string][]string)
+	whitelist["img"] = []string{"alt", "title", "src", "srcset", "sizes"}
+	whitelist["picture"] = []string{}
+	whitelist["audio"] = []string{"src"}
+	whitelist["video"] = []string{"poster", "height", "width", "src"}
+	whitelist["source"] = []string{"src", "type", "srcset", "sizes", "media"}
+	whitelist["dt"] = []string{}
+	whitelist["dd"] = []string{}
+	whitelist["dl"] = []string{}
+	whitelist["table"] = []string{}
+	whitelist["caption"] = []string{}
+	whitelist["thead"] = []string{}
+	whitelist["tfooter"] = []string{}
+	whitelist["tr"] = []string{}
+	whitelist["td"] = []string{"rowspan", "colspan"}
+	whitelist["th"] = []string{"rowspan", "colspan"}
+	whitelist["h1"] = []string{}
+	whitelist["h2"] = []string{}
+	whitelist["h3"] = []string{}
+	whitelist["h4"] = []string{}
+	whitelist["h5"] = []string{}
+	whitelist["h6"] = []string{}
+	whitelist["strong"] = []string{}
+	whitelist["em"] = []string{}
+	whitelist["code"] = []string{}
+	whitelist["pre"] = []string{}
+	whitelist["blockquote"] = []string{}
+	whitelist["q"] = []string{"cite"}
+	whitelist["p"] = []string{}
+	whitelist["ul"] = []string{}
+	whitelist["li"] = []string{}
+	whitelist["ol"] = []string{}
+	whitelist["br"] = []string{}
+	whitelist["del"] = []string{}
+	whitelist["a"] = []string{"href", "title"}
+	whitelist["figure"] = []string{}
+	whitelist["figcaption"] = []string{}
+	whitelist["cite"] = []string{}
+	whitelist["time"] = []string{"datetime"}
+	whitelist["abbr"] = []string{"title"}
+	whitelist["acronym"] = []string{"title"}
+	whitelist["wbr"] = []string{}
+	whitelist["dfn"] = []string{}
+	whitelist["sub"] = []string{}
+	whitelist["sup"] = []string{}
+	whitelist["var"] = []string{}
+	whitelist["samp"] = []string{}
+	whitelist["s"] = []string{}
+	whitelist["del"] = []string{}
+	whitelist["ins"] = []string{}
+	whitelist["kbd"] = []string{}
+	whitelist["rp"] = []string{}
+	whitelist["rt"] = []string{}
+	whitelist["rtc"] = []string{}
+	whitelist["ruby"] = []string{}
+	whitelist["iframe"] = []string{"width", "height", "frameborder", "src", "allowfullscreen"}
+	return whitelist
+}
+
+func inList(needle string, haystack []string) bool {
+	for _, element := range haystack {
+		if element == needle {
+			return true
+		}
+	}
+
+	return false
+}
+
+func isBlockedTag(tagName string) bool {
+	blacklist := []string{
+		"noscript",
+		"script",
+		"style",
+	}
+
+	for _, element := range blacklist {
+		if element == tagName {
+			return true
+		}
+	}
+
+	return false
+}
+
+/*
+
+One or more strings separated by commas, indicating possible image sources for the user agent to use.
+
+Each string is composed of:
+- A URL to an image
+- Optionally, whitespace followed by one of:
+- 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.
+- A pixel density descriptor (a positive floating point number directly followed by x).
+
+*/
+func sanitizeSrcsetAttr(baseURL, value string) string {
+	var sanitizedSources []string
+	rawSources := splitSrcsetRegex.Split(value, -1)
+	for _, rawSource := range rawSources {
+		parts := strings.Split(strings.TrimSpace(rawSource), " ")
+		nbParts := len(parts)
+
+		if nbParts > 0 {
+			sanitizedSource := parts[0]
+			if !strings.HasPrefix(parts[0], "data:") {
+				sanitizedSource = htmlutil.AbsoluteUrl(parts[0], baseURL)
+				if sanitizedSource == "" {
+					continue
+				}
+			}
+
+			if nbParts == 2 && isValidWidthOrDensityDescriptor(parts[1]) {
+				sanitizedSource += " " + parts[1]
+			}
+
+			sanitizedSources = append(sanitizedSources, sanitizedSource)
+		}
+	}
+	return strings.Join(sanitizedSources, ", ")
+}
+
+func isValidWidthOrDensityDescriptor(value string) bool {
+	if value == "" {
+		return false
+	}
+
+	lastChar := value[len(value)-1:]
+	if lastChar != "w" && lastChar != "x" {
+		return false
+	}
+
+	_, err := strconv.ParseFloat(value[0:len(value)-1], 32)
+	return err == nil
+}
+
+func isValidDataAttribute(value string) bool {
+	var dataAttributeAllowList = []string{
+		"data:image/avif",
+		"data:image/apng",
+		"data:image/png",
+		"data:image/svg",
+		"data:image/svg+xml",
+		"data:image/jpg",
+		"data:image/jpeg",
+		"data:image/gif",
+		"data:image/webp",
+	}
+
+	for _, prefix := range dataAttributeAllowList {
+		if strings.HasPrefix(value, prefix) {
+			return true
+		}
+	}
+	return false
+}
--- a/src/content/sanitizer/sanitizer_test.go
+++ b/src/content/sanitizer/sanitizer_test.go
@@ -0,0 +1,492 @@
+// Copyright 2017 Frédéric Guillot. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package scraper
+
+import "testing"
+
+func TestValidInput(t *testing.T) {
+	input := `<p>This is a <strong>text</strong> with an image: <img src="http://example.org/" alt="Test" loading="lazy">.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if input != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, input, output)
+	}
+}
+
+func TestImgWithTextDataURL(t *testing.T) {
+	input := `<img src="data:text/plain;base64,SGVsbG8sIFdvcmxkIQ==" alt="Example">`
+	expected := ``
+	output := Sanitize("http://example.org/", input)
+
+	if output != expected {
+		t.Errorf(`Wrong output: %s`, output)
+	}
+}
+
+func TestImgWithDataURL(t *testing.T) {
+	input := `<img src="data:image/gif;base64,test" alt="Example">`
+	expected := `<img src="data:image/gif;base64,test" alt="Example" loading="lazy">`
+	output := Sanitize("http://example.org/", input)
+
+	if output != expected {
+		t.Errorf(`Wrong output: %s`, output)
+	}
+}
+
+func TestImgWithSrcset(t *testing.T) {
+	input := `<img srcset="example-320w.jpg, example-480w.jpg 1.5x,   example-640w.jpg 2x, example-640w.jpg 640w" src="example-640w.jpg" alt="Example">`
+	expected := `<img srcset="http://example.org/example-320w.jpg, http://example.org/example-480w.jpg 1.5x, http://example.org/example-640w.jpg 2x, http://example.org/example-640w.jpg 640w" src="http://example.org/example-640w.jpg" alt="Example" loading="lazy">`
+	output := Sanitize("http://example.org/", input)
+
+	if output != expected {
+		t.Errorf(`Wrong output: %s`, output)
+	}
+}
+
+func TestImgWithSrcsetAndDataURL(t *testing.T) {
+	input := `<img srcset="data:image/gif;base64,test" src="http://example.org/example-320w.jpg" alt="Example">`
+	expected := `<img srcset="data:image/gif;base64,test" src="http://example.org/example-320w.jpg" alt="Example" loading="lazy">`
+	output := Sanitize("http://example.org/", input)
+
+	if output != expected {
+		t.Errorf(`Wrong output: %s`, output)
+	}
+}
+
+func TestSourceWithSrcsetAndMedia(t *testing.T) {
+	input := `<picture><source media="(min-width: 800px)" srcset="elva-800w.jpg"></picture>`
+	expected := `<picture><source media="(min-width: 800px)" srcset="http://example.org/elva-800w.jpg"></picture>`
+	output := Sanitize("http://example.org/", input)
+
+	if output != expected {
+		t.Errorf(`Wrong output: %s`, output)
+	}
+}
+
+func TestMediumImgWithSrcset(t *testing.T) {
+	input := `<img alt="Image for post" class="t u v ef aj" src="https://miro.medium.com/max/5460/1*aJ9JibWDqO81qMfNtqgqrw.jpeg" srcset="https://miro.medium.com/max/552/1*aJ9JibWDqO81qMfNtqgqrw.jpeg 276w, https://miro.medium.com/max/1000/1*aJ9JibWDqO81qMfNtqgqrw.jpeg 500w" sizes="500px" width="2730" height="3407">`
+	expected := `<img alt="Image for post" src="https://miro.medium.com/max/5460/1*aJ9JibWDqO81qMfNtqgqrw.jpeg" srcset="https://miro.medium.com/max/552/1*aJ9JibWDqO81qMfNtqgqrw.jpeg 276w, https://miro.medium.com/max/1000/1*aJ9JibWDqO81qMfNtqgqrw.jpeg 500w" sizes="500px" loading="lazy">`
+	output := Sanitize("http://example.org/", input)
+
+	if output != expected {
+		t.Errorf(`Wrong output: %s`, output)
+	}
+}
+
+func TestSelfClosingTags(t *testing.T) {
+	input := `<p>This <br> is a <strong>text</strong> <br/>with an image: <img src="http://example.org/" alt="Test" loading="lazy"/>.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if input != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, input, output)
+	}
+}
+
+func TestTable(t *testing.T) {
+	input := `<table><tr><th>A</th><th colspan="2">B</th></tr><tr><td>C</td><td>D</td><td>E</td></tr></table>`
+	output := Sanitize("http://example.org/", input)
+
+	if input != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, input, output)
+	}
+}
+
+func TestRelativeURL(t *testing.T) {
+	input := `This <a href="/test.html">link is relative</a> and this image: <img src="../folder/image.png"/>`
+	expected := `This <a href="http://example.org/test.html" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">link is relative</a> and this image: <img src="http://example.org/folder/image.png" loading="lazy"/>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestProtocolRelativeURL(t *testing.T) {
+	input := `This <a href="//static.example.org/index.html">link is relative</a>.`
+	expected := `This <a href="http://static.example.org/index.html" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">link is relative</a>.`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestInvalidTag(t *testing.T) {
+	input := `<p>My invalid <b>tag</b>.</p>`
+	expected := `<p>My invalid tag.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestVideoTag(t *testing.T) {
+	input := `<p>My valid <video src="videofile.webm" autoplay poster="posterimage.jpg">fallback</video>.</p>`
+	expected := `<p>My valid <video src="http://example.org/videofile.webm" poster="http://example.org/posterimage.jpg" controls>fallback</video>.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestAudioAndSourceTag(t *testing.T) {
+	input := `<p>My music <audio controls="controls"><source src="foo.wav" type="audio/wav"></audio>.</p>`
+	expected := `<p>My music <audio controls><source src="http://example.org/foo.wav" type="audio/wav"></audio>.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestUnknownTag(t *testing.T) {
+	input := `<p>My invalid <unknown>tag</unknown>.</p>`
+	expected := `<p>My invalid tag.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestInvalidNestedTag(t *testing.T) {
+	input := `<p>My invalid <b>tag with some <em>valid</em> tag</b>.</p>`
+	expected := `<p>My invalid tag with some <em>valid</em> tag.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestInvalidIFrame(t *testing.T) {
+	input := `<iframe src="http://example.org/"></iframe>`
+	expected := ``
+	output := Sanitize("http://example.com/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestIFrameWithChildElements(t *testing.T) {
+	input := `<iframe src="https://www.youtube.com/"><p>test</p></iframe>`
+	expected := `<iframe src="https://www.youtube.com/" sandbox="allow-scripts allow-same-origin allow-popups" loading="lazy"></iframe>`
+	output := Sanitize("http://example.com/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestInvalidURLScheme(t *testing.T) {
+	input := `<p>This link is <a src="file:///etc/passwd">not valid</a></p>`
+	expected := `<p>This link is not valid</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestAPTURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="apt:some-package?channel=test">valid</a></p>`
+	expected := `<p>This link is <a href="apt:some-package?channel=test" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestBitcoinURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="bitcoin:175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W">valid</a></p>`
+	expected := `<p>This link is <a href="bitcoin:175tWpb8K1S7NmH4Zx6rewF9WQrcZv245W" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestCallToURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="callto:12345679">valid</a></p>`
+	expected := `<p>This link is <a href="callto:12345679" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestFeedURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="feed://example.com/rss.xml">valid</a></p>`
+	expected := `<p>This link is <a href="feed://example.com/rss.xml" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+
+	input = `<p>This link is <a href="feed:https://example.com/rss.xml">valid</a></p>`
+	expected = `<p>This link is <a href="feed:https://example.com/rss.xml" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output = Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestGeoURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="geo:13.4125,103.8667">valid</a></p>`
+	expected := `<p>This link is <a href="geo:13.4125,103.8667" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestItunesURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="itms://itunes.com/apps/my-app-name">valid</a></p>`
+	expected := `<p>This link is <a href="itms://itunes.com/apps/my-app-name" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+
+	input = `<p>This link is <a href="itms-apps://itunes.com/apps/my-app-name">valid</a></p>`
+	expected = `<p>This link is <a href="itms-apps://itunes.com/apps/my-app-name" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output = Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestMagnetURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="magnet:?xt.1=urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C&amp;xt.2=urn:sha1:TXGCZQTH26NL6OUQAJJPFALHG2LTGBC7">valid</a></p>`
+	expected := `<p>This link is <a href="magnet:?xt.1=urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C&amp;xt.2=urn:sha1:TXGCZQTH26NL6OUQAJJPFALHG2LTGBC7" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestMailtoURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="mailto:jsmith@example.com?subject=A%20Test&amp;body=My%20idea%20is%3A%20%0A">valid</a></p>`
+	expected := `<p>This link is <a href="mailto:jsmith@example.com?subject=A%20Test&amp;body=My%20idea%20is%3A%20%0A" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestNewsURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="news://news.server.example/*">valid</a></p>`
+	expected := `<p>This link is <a href="news://news.server.example/*" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+
+	input = `<p>This link is <a href="news:example.group.this">valid</a></p>`
+	expected = `<p>This link is <a href="news:example.group.this" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output = Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+
+	input = `<p>This link is <a href="nntp://news.server.example/example.group.this">valid</a></p>`
+	expected = `<p>This link is <a href="nntp://news.server.example/example.group.this" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output = Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestRTMPURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="rtmp://mycompany.com/vod/mp4:mycoolvideo.mov">valid</a></p>`
+	expected := `<p>This link is <a href="rtmp://mycompany.com/vod/mp4:mycoolvideo.mov" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestSIPURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="sip:+1-212-555-1212:1234@gateway.com;user=phone">valid</a></p>`
+	expected := `<p>This link is <a href="sip:+1-212-555-1212:1234@gateway.com;user=phone" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+
+	input = `<p>This link is <a href="sips:alice@atlanta.com?subject=project%20x&amp;priority=urgent">valid</a></p>`
+	expected = `<p>This link is <a href="sips:alice@atlanta.com?subject=project%20x&amp;priority=urgent" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output = Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestSkypeURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="skype:echo123?call">valid</a></p>`
+	expected := `<p>This link is <a href="skype:echo123?call" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestSpotifyURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="spotify:track:2jCnn1QPQ3E8ExtLe6INsx">valid</a></p>`
+	expected := `<p>This link is <a href="spotify:track:2jCnn1QPQ3E8ExtLe6INsx" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestSteamURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="steam://settings/account">valid</a></p>`
+	expected := `<p>This link is <a href="steam://settings/account" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestSubversionURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="svn://example.org">valid</a></p>`
+	expected := `<p>This link is <a href="svn://example.org" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+
+	input = `<p>This link is <a href="svn+ssh://example.org">valid</a></p>`
+	expected = `<p>This link is <a href="svn+ssh://example.org" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output = Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestTelURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="tel:+1-201-555-0123">valid</a></p>`
+	expected := `<p>This link is <a href="tel:+1-201-555-0123" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestWebcalURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="webcal://example.com/calendar.ics">valid</a></p>`
+	expected := `<p>This link is <a href="webcal://example.com/calendar.ics" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestXMPPURIScheme(t *testing.T) {
+	input := `<p>This link is <a href="xmpp:user@host?subscribe&amp;type=subscribed">valid</a></p>`
+	expected := `<p>This link is <a href="xmpp:user@host?subscribe&amp;type=subscribed" rel="noopener noreferrer" target="_blank" referrerpolicy="no-referrer">valid</a></p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestBlacklistedLink(t *testing.T) {
+	input := `<p>This image is not valid <img src="https://stats.wordpress.com/some-tracker"></p>`
+	expected := `<p>This image is not valid </p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestXmlEntities(t *testing.T) {
+	input := `<pre>echo "test" &gt; /etc/hosts</pre>`
+	expected := `<pre>echo &#34;test&#34; &gt; /etc/hosts</pre>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestEspaceAttributes(t *testing.T) {
+	input := `<td rowspan="<b>test</b>">test</td>`
+	expected := `<td rowspan="&lt;b&gt;test&lt;/b&gt;">test</td>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestReplaceIframeURL(t *testing.T) {
+	input := `<iframe src="https://player.vimeo.com/video/123456?title=0&amp;byline=0"></iframe>`
+	expected := `<iframe src="https://player.vimeo.com/video/123456?title=0&amp;byline=0" sandbox="allow-scripts allow-same-origin allow-popups" loading="lazy"></iframe>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestReplaceNoScript(t *testing.T) {
+	input := `<p>Before paragraph.</p><noscript>Inside <code>noscript</code> tag with an image: <img src="http://example.org/" alt="Test" loading="lazy"></noscript><p>After paragraph.</p>`
+	expected := `<p>Before paragraph.</p><p>After paragraph.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestReplaceScript(t *testing.T) {
+	input := `<p>Before paragraph.</p><script type="text/javascript">alert("1");</script><p>After paragraph.</p>`
+	expected := `<p>Before paragraph.</p><p>After paragraph.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}
+
+func TestReplaceStyle(t *testing.T) {
+	input := `<p>Before paragraph.</p><style>body { background-color: #ff0000; }</style><p>After paragraph.</p>`
+	expected := `<p>Before paragraph.</p><p>After paragraph.</p>`
+	output := Sanitize("http://example.org/", input)
+
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}