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// Copyright (c) 2014, David Kitchen <david@buro9.com>
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// * Neither the name of the organisation (Microcosm) nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package bluemonday
import (
"regexp"
)
// StrictPolicy returns an empty policy, which will effectively strip all HTML
// elements and their attributes from a document.
func StrictPolicy() *Policy {
return NewPolicy()
}
// StripTagsPolicy is DEPRECATED. Use StrictPolicy instead.
func StripTagsPolicy() *Policy {
return StrictPolicy()
}
// UGCPolicy returns a policy aimed at user generated content that is a result
// of HTML WYSIWYG tools and Markdown conversions.
//
// This is expected to be a fairly rich document where as much markup as
// possible should be retained. Markdown permits raw HTML so we are basically
// providing a policy to sanitise HTML5 documents safely but with the
// least intrusion on the formatting expectations of the user.
func UGCPolicy() *Policy {
p := NewPolicy()
///////////////////////
// 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)$`)).OnElements("details")
// "fieldset" is not permitted as we are not allowing forms to be created.
// "figure" is permitted and takes no attributes
p.AllowElements("figure")
// "nav" is not permitted as it is assumed that the site (and not the user)
// has defined navigation elements
// "section" is permitted and takes no attributes
p.AllowElements("section")
// "summary" is permitted and takes no attributes
p.AllowElements("summary")
//////////////////////////
// Headings and footers //
//////////////////////////
// "footer" is not permitted as we expect user content to be a fragment and
// not structural to this extent
// "h1" through "h6" are permitted and take no attributes
p.AllowElements("h1", "h2", "h3", "h4", "h5", "h6")
// "header" is not permitted as we expect user content to be a fragment and
// not structural to this extent
// "hgroup" is permitted and takes no attributes
p.AllowElements("hgroup")
/////////////////////////////////////
// Content grouping and separating //
/////////////////////////////////////
// "blockquote" is permitted, including the "cite" attribute which must be
// a standard URL.
p.AllowAttrs("cite").OnElements("blockquote")
// "br" "div" "hr" "p" "span" "wbr" are permitted and take no attributes
p.AllowElements("br", "div", "hr", "p", "span", "wbr")
///////////
// Links //
///////////
// "a" is permitted
p.AllowAttrs("href").OnElements("a")
// "area" is permitted along with the attributes that map image maps work
p.AllowAttrs("name").Matching(
regexp.MustCompile(`^([\p{L}\p{N}_-]+)$`),
).OnElements("map")
p.AllowAttrs("alt").Matching(Paragraph).OnElements("area")
p.AllowAttrs("coords").Matching(
regexp.MustCompile(`^([0-9]+,)+[0-9]+$`),
).OnElements("area")
p.AllowAttrs("href").OnElements("area")
p.AllowAttrs("rel").Matching(SpaceSeparatedTokens).OnElements("area")
p.AllowAttrs("shape").Matching(
regexp.MustCompile(`(?i)^(default|circle|rect|poly)$`),
).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(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(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(Paragraph).OnElements("del", "ins")
p.AllowAttrs("datetime").Matching(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(Number).OnElements("meter")
// "progress" is permitted
p.AllowAttrs("value", "max").Matching(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()
return p
}