Albirew/nyaa-pantsu
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nyaa-pantsu/util/markdown.go
2017-05-24 17:11:13 +10:00

276 lignes
7,8 Kio
Go

package util
import (
"bytes"
"html/template"
"log"
"regexp"
"strings"
"github.com/microcosm-cc/bluemonday"
md "github.com/russross/blackfriday"
"golang.org/x/net/html"
)
//Some default rules, plus and minus some.
var mdOptions = 0 |
md.EXTENSION_AUTOLINK |
md.EXTENSION_HARD_LINE_BREAK |
md.EXTENSION_NO_EMPTY_LINE_BEFORE_BLOCK |
md.EXTENSION_NO_INTRA_EMPHASIS |
md.EXTENSION_SPACE_HEADERS |
md.EXTENSION_STRIKETHROUGH
var htmlFlags = 0 |
md.HTML_USE_XHTML |
md.HTML_SMARTYPANTS_FRACTIONS |
md.HTML_SAFELINK |
md.HTML_NOREFERRER_LINKS |
md.HTML_HREF_TARGET_BLANK
func init() {
HtmlMdRenderer = md.HtmlRenderer(htmlFlags, "", "")
}
var HtmlMdRenderer md.Renderer
// TODO: restrict certain types of markdown
func MarkdownToHTML(markdown string) template.HTML {
if len(markdown) >= 3 && markdown[:3] == ">" {
markdown = ">" + markdown[3:]
}
markdown = strings.Replace(markdown, "\n>", "\n>", -1)
unsafe := md.MarkdownOptions([]byte(markdown), HtmlMdRenderer, md.Options{Extensions: mdOptions})
html := bluemonday.UGCPolicy().SanitizeBytes(unsafe)
return template.HTML(html)
}
/*
* Sanitize a message passed as a string according to a setted model or allowing a set of html tags and output a string
*/
func Sanitize(msg string, elements ...string) string {
msg = repairHTMLTags(msg) // We repair possible broken html tags
p := bluemonday.NewPolicy()
if len(elements) > 0 {
if elements[0] == "default" { // default model same as UGC without div
///////////////////////
// Global attributes //
///////////////////////
// "class" is not permitted as we are not allowing users to style their own
// content
p.AllowStandardAttributes()
//////////////////////////////
// Global URL format policy //
//////////////////////////////
p.AllowStandardURLs()
////////////////////////////////
// Declarations and structure //
////////////////////////////////
// "xml" "xslt" "DOCTYPE" "html" "head" are not permitted as we are
// expecting user generated content to be a fragment of HTML and not a full
// document.
//////////////////////////
// Sectioning root tags //
//////////////////////////
// "article" and "aside" are permitted and takes no attributes
p.AllowElements("article", "aside")
// "body" is not permitted as we are expecting user generated content to be a fragment
// of HTML and not a full document.
// "details" is permitted, including the "open" attribute which can either
// be blank or the value "open".
p.AllowAttrs(
"open",
).Matching(regexp.MustCompile(`(?i)^(|open)$`)).OnElements("details")
// "fieldset" is not permitted as we are not allowing forms to be created.
// "figure" is permitted and takes no attributes
p.AllowElements("figure")
// "nav" is not permitted as it is assumed that the site (and not the user)
// has defined navigation elements
// "section" is permitted and takes no attributes
p.AllowElements("section")
// "summary" is permitted and takes no attributes
p.AllowElements("summary")
//////////////////////////
// Headings and footers //
//////////////////////////
// "footer" is not permitted as we expect user content to be a fragment and
// not structural to this extent
// "h1" through "h6" are permitted and take no attributes
p.AllowElements("h1", "h2", "h3", "h4", "h5", "h6")
// "header" is not permitted as we expect user content to be a fragment and
// not structural to this extent
// "hgroup" is permitted and takes no attributes
p.AllowElements("hgroup")
/////////////////////////////////////
// Content grouping and separating //
/////////////////////////////////////
// "blockquote" is permitted, including the "cite" attribute which must be
// a standard URL.
p.AllowAttrs("cite").OnElements("blockquote")
// "br" "div" "hr" "p" "span" "wbr" are permitted and take no attributes
p.AllowElements("br", "hr", "p", "span", "wbr")
///////////
// Links //
///////////
// "a" is permitted
p.AllowAttrs("href").OnElements("a")
// "area" is permitted along with the attributes that map image maps work
p.AllowAttrs("name").Matching(
regexp.MustCompile(`^([\p{L}\p{N}_-]+)$`),
).OnElements("map")
p.AllowAttrs("alt").Matching(bluemonday.Paragraph).OnElements("area")
p.AllowAttrs("coords").Matching(
regexp.MustCompile(`^([0-9]+,)+[0-9]+$`),
).OnElements("area")
p.AllowAttrs("href").OnElements("area")
p.AllowAttrs("rel").Matching(bluemonday.SpaceSeparatedTokens).OnElements("area")
p.AllowAttrs("shape").Matching(
regexp.MustCompile(`(?i)^(default|circle|rect|poly)$`),
).OnElements("area")
p.AllowAttrs("usemap").Matching(
regexp.MustCompile(`(?i)^#[\p{L}\p{N}_-]+$`),
).OnElements("img")
// "link" is not permitted
/////////////////////
// Phrase elements //
/////////////////////
// The following are all inline phrasing elements
p.AllowElements("abbr", "acronym", "cite", "code", "dfn", "em",
"figcaption", "mark", "s", "samp", "strong", "sub", "sup", "var")
// "q" is permitted and "cite" is a URL and handled by URL policies
p.AllowAttrs("cite").OnElements("q")
// "time" is permitted
p.AllowAttrs("datetime").Matching(bluemonday.ISO8601).OnElements("time")
////////////////////
// Style elements //
////////////////////
// block and inline elements that impart no semantic meaning but style the
// document
p.AllowElements("b", "i", "pre", "small", "strike", "tt", "u")
// "style" is not permitted as we are not yet sanitising CSS and it is an
// XSS attack vector
//////////////////////
// HTML5 Formatting //
//////////////////////
// "bdi" "bdo" are permitted
p.AllowAttrs("dir").Matching(bluemonday.Direction).OnElements("bdi", "bdo")
// "rp" "rt" "ruby" are permitted
p.AllowElements("rp", "rt", "ruby")
///////////////////////////
// HTML5 Change tracking //
///////////////////////////
// "del" "ins" are permitted
p.AllowAttrs("cite").Matching(bluemonday.Paragraph).OnElements("del", "ins")
p.AllowAttrs("datetime").Matching(bluemonday.ISO8601).OnElements("del", "ins")
///////////
// Lists //
///////////
p.AllowLists()
////////////
// Tables //
////////////
p.AllowTables()
///////////
// Forms //
///////////
// By and large, forms are not permitted. However there are some form
// elements that can be used to present data, and we do permit those
//
// "button" "fieldset" "input" "keygen" "label" "output" "select" "datalist"
// "textarea" "optgroup" "option" are all not permitted
// "meter" is permitted
p.AllowAttrs(
"value",
"min",
"max",
"low",
"high",
"optimum",
).Matching(bluemonday.Number).OnElements("meter")
// "progress" is permitted
p.AllowAttrs("value", "max").Matching(bluemonday.Number).OnElements("progress")
//////////////////////
// Embedded content //
//////////////////////
// Vast majority not permitted
// "audio" "canvas" "embed" "iframe" "object" "param" "source" "svg" "track"
// "video" are all not permitted
p.AllowImages()
} else if elements[0] == "comment" {
p.AllowElements("b", "strong", "em", "i", "u", "blockquote", "q")
p.AllowImages()
p.AllowStandardURLs()
p.AllowAttrs("cite").OnElements("blockquote", "q")
p.AllowAttrs("href").OnElements("a")
p.AddTargetBlankToFullyQualifiedLinks(true)
} else { // allowing set of html tags
p.AllowElements(elements...)
}
}
return p.Sanitize(msg)
}
/*
* Should close any opened tags and strip any empty end tags
*/
func repairHTMLTags(brokenHtml string) string {
reader := strings.NewReader(brokenHtml)
root, err := html.Parse(reader)
if err != nil {
log.Fatal(err)
}
var b bytes.Buffer
html.Render(&b, root)
fixedHTML := b.String()
return fixedHTML
}