gtsocial-umbx

helpers.go (11443B)

---

 // 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 (
 	"encoding/base64"
 	"net/url"
 	"regexp"
 )
 
 // A selection of regular expressions that can be used as .Matching() rules on
 // HTML attributes.
 var (
 	// CellAlign handles the `align` attribute
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/td#attr-align
 	CellAlign = regexp.MustCompile(`(?i)^(center|justify|left|right|char)$`)
 
 	// CellVerticalAlign handles the `valign` attribute
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/td#attr-valign
 	CellVerticalAlign = regexp.MustCompile(`(?i)^(baseline|bottom|middle|top)$`)
 
 	// Direction handles the `dir` attribute
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/bdo#attr-dir
 	Direction = regexp.MustCompile(`(?i)^(rtl|ltr)$`)
 
 	// ImageAlign handles the `align` attribute on the `image` tag
 	// http://www.w3.org/MarkUp/Test/Img/imgtest.html
 	ImageAlign = regexp.MustCompile(
 		`(?i)^(left|right|top|texttop|middle|absmiddle|baseline|bottom|absbottom)$`,
 	)
 
 	// Integer describes whole positive integers (including 0) used in places
 	// like td.colspan
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/td#attr-colspan
 	Integer = regexp.MustCompile(`^[0-9]+$`)
 
 	// ISO8601 according to the W3 group is only a subset of the ISO8601
 	// standard: http://www.w3.org/TR/NOTE-datetime
 	//
 	// Used in places like time.datetime
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/time#attr-datetime
 	//
 	// Matches patterns:
 	//  Year:
 	//     YYYY (eg 1997)
 	//  Year and month:
 	//     YYYY-MM (eg 1997-07)
 	//  Complete date:
 	//     YYYY-MM-DD (eg 1997-07-16)
 	//  Complete date plus hours and minutes:
 	//     YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)
 	//  Complete date plus hours, minutes and seconds:
 	//     YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)
 	//  Complete date plus hours, minutes, seconds and a decimal fraction of a
 	//  second
 	//      YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)
 	ISO8601 = regexp.MustCompile(
 		`^[0-9]{4}(-[0-9]{2}(-[0-9]{2}([ T][0-9]{2}(:[0-9]{2}){1,2}(.[0-9]{1,6})` +
 			`?Z?([\+-][0-9]{2}:[0-9]{2})?)?)?)?$`,
 	)
 
 	// ListType encapsulates the common value as well as the latest spec
 	// values for lists
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ol#attr-type
 	ListType = regexp.MustCompile(`(?i)^(circle|disc|square|a|A|i|I|1)$`)
 
 	// SpaceSeparatedTokens is used in places like `a.rel` and the common attribute
 	// `class` which both contain space delimited lists of data tokens
 	// http://www.w3.org/TR/html-markup/datatypes.html#common.data.tokens-def
 	// Regexp: \p{L} matches unicode letters, \p{N} matches unicode numbers
 	SpaceSeparatedTokens = regexp.MustCompile(`^([\s\p{L}\p{N}_-]+)$`)
 
 	// Number is a double value used on HTML5 meter and progress elements
 	// http://www.whatwg.org/specs/web-apps/current-work/multipage/the-button-element.html#the-meter-element
 	Number = regexp.MustCompile(`^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$`)
 
 	// NumberOrPercent is used predominantly as units of measurement in width
 	// and height attributes
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img#attr-height
 	NumberOrPercent = regexp.MustCompile(`^[0-9]+[%]?$`)
 
 	// Paragraph of text in an attribute such as *.'title', img.alt, etc
 	// https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes#attr-title
 	// Note that we are not allowing chars that could close tags like '>'
 	Paragraph = regexp.MustCompile(`^[\p{L}\p{N}\s\-_',\[\]!\./\\\(\)]*$`)
 
 	// dataURIImagePrefix is used by AllowDataURIImages to define the acceptable
 	// prefix of data URIs that contain common web image formats.
 	//
 	// This is not exported as it's not useful by itself, and only has value
 	// within the AllowDataURIImages func
 	dataURIImagePrefix = regexp.MustCompile(
 		`^image/(gif|jpeg|png|svg\+xml|webp);base64,`,
 	)
 )
 
 // AllowStandardURLs is a convenience function that will enable rel="nofollow"
 // on "a", "area" and "link" (if you have allowed those elements) and will
 // ensure that the URL values are parseable and either relative or belong to the
 // "mailto", "http", or "https" schemes
 func (p *Policy) AllowStandardURLs() {
 	// URLs must be parseable by net/url.Parse()
 	p.RequireParseableURLs(true)
 
 	// !url.IsAbs() is permitted
 	p.AllowRelativeURLs(true)
 
 	// Most common URL schemes only
 	p.AllowURLSchemes("mailto", "http", "https")
 
 	// For linking elements we will add rel="nofollow" if it does not already exist
 	// This applies to "a" "area" "link"
 	p.RequireNoFollowOnLinks(true)
 }
 
 // AllowStandardAttributes will enable "id", "title" and the language specific
 // attributes "dir" and "lang" on all elements that are allowed
 func (p *Policy) AllowStandardAttributes() {
 	// "dir" "lang" are permitted as both language attributes affect charsets
 	// and direction of text.
 	p.AllowAttrs("dir").Matching(Direction).Globally()
 	p.AllowAttrs(
 		"lang",
 	).Matching(regexp.MustCompile(`[a-zA-Z]{2,20}`)).Globally()
 
 	// "id" is permitted. This is pretty much as some HTML elements require this
 	// to work well ("dfn" is an example of a "id" being value)
 	// This does create a risk that JavaScript and CSS within your web page
 	// might identify the wrong elements. Ensure that you select things
 	// accurately
 	p.AllowAttrs("id").Matching(
 		regexp.MustCompile(`[a-zA-Z0-9\:\-_\.]+`),
 	).Globally()
 
 	// "title" is permitted as it improves accessibility.
 	p.AllowAttrs("title").Matching(Paragraph).Globally()
 }
 
 // AllowStyling presently enables the class attribute globally.
 //
 // Note: When bluemonday ships a CSS parser and we can safely sanitise that,
 // this will also allow sanitized styling of elements via the style attribute.
 func (p *Policy) AllowStyling() {
 
 	// "class" is permitted globally
 	p.AllowAttrs("class").Matching(SpaceSeparatedTokens).Globally()
 }
 
 // AllowImages enables the img element and some popular attributes. It will also
 // ensure that URL values are parseable. This helper does not enable data URI
 // images, for that you should also use the AllowDataURIImages() helper.
 func (p *Policy) AllowImages() {
 
 	// "img" is permitted
 	p.AllowAttrs("align").Matching(ImageAlign).OnElements("img")
 	p.AllowAttrs("alt").Matching(Paragraph).OnElements("img")
 	p.AllowAttrs("height", "width").Matching(NumberOrPercent).OnElements("img")
 
 	// Standard URLs enabled
 	p.AllowStandardURLs()
 	p.AllowAttrs("src").OnElements("img")
 }
 
 // AllowDataURIImages permits the use of inline images defined in RFC2397
 // http://tools.ietf.org/html/rfc2397
 // http://en.wikipedia.org/wiki/Data_URI_scheme
 //
 // Images must have a mimetype matching:
 //
 //	image/gif
 //	image/jpeg
 //	image/png
 //	image/webp
 //
 // NOTE: There is a potential security risk to allowing data URIs and you should
 // only permit them on content you already trust.
 // http://palizine.plynt.com/issues/2010Oct/bypass-xss-filters/
 // https://capec.mitre.org/data/definitions/244.html
 func (p *Policy) AllowDataURIImages() {
 
 	// URLs must be parseable by net/url.Parse()
 	p.RequireParseableURLs(true)
 
 	// Supply a function to validate images contained within data URI
 	p.AllowURLSchemeWithCustomPolicy(
 		"data",
 		func(url *url.URL) (allowUrl bool) {
 			if url.RawQuery != "" || url.Fragment != "" {
 				return false
 			}
 
 			matched := dataURIImagePrefix.FindString(url.Opaque)
 			if matched == "" {
 				return false
 			}
 
 			_, err := base64.StdEncoding.DecodeString(url.Opaque[len(matched):])
 			if err != nil {
 				return false
 			}
 
 			return true
 		},
 	)
 }
 
 // AllowLists will enabled ordered and unordered lists, as well as definition
 // lists
 func (p *Policy) AllowLists() {
 	// "ol" "ul" are permitted
 	p.AllowAttrs("type").Matching(ListType).OnElements("ol", "ul")
 
 	// "li" is permitted
 	p.AllowAttrs("type").Matching(ListType).OnElements("li")
 	p.AllowAttrs("value").Matching(Integer).OnElements("li")
 
 	// "dl" "dt" "dd" are permitted
 	p.AllowElements("dl", "dt", "dd")
 }
 
 // AllowTables will enable a rich set of elements and attributes to describe
 // HTML tables
 func (p *Policy) AllowTables() {
 
 	// "table" is permitted
 	p.AllowAttrs("height", "width").Matching(NumberOrPercent).OnElements("table")
 	p.AllowAttrs("summary").Matching(Paragraph).OnElements("table")
 
 	// "caption" is permitted
 	p.AllowElements("caption")
 
 	// "col" "colgroup" are permitted
 	p.AllowAttrs("align").Matching(CellAlign).OnElements("col", "colgroup")
 	p.AllowAttrs("height", "width").Matching(
 		NumberOrPercent,
 	).OnElements("col", "colgroup")
 	p.AllowAttrs("span").Matching(Integer).OnElements("colgroup", "col")
 	p.AllowAttrs("valign").Matching(
 		CellVerticalAlign,
 	).OnElements("col", "colgroup")
 
 	// "thead" "tr" are permitted
 	p.AllowAttrs("align").Matching(CellAlign).OnElements("thead", "tr")
 	p.AllowAttrs("valign").Matching(CellVerticalAlign).OnElements("thead", "tr")
 
 	// "td" "th" are permitted
 	p.AllowAttrs("abbr").Matching(Paragraph).OnElements("td", "th")
 	p.AllowAttrs("align").Matching(CellAlign).OnElements("td", "th")
 	p.AllowAttrs("colspan", "rowspan").Matching(Integer).OnElements("td", "th")
 	p.AllowAttrs("headers").Matching(
 		SpaceSeparatedTokens,
 	).OnElements("td", "th")
 	p.AllowAttrs("height", "width").Matching(
 		NumberOrPercent,
 	).OnElements("td", "th")
 	p.AllowAttrs(
 		"scope",
 	).Matching(
 		regexp.MustCompile(`(?i)(?:row|col)(?:group)?`),
 	).OnElements("td", "th")
 	p.AllowAttrs("valign").Matching(CellVerticalAlign).OnElements("td", "th")
 	p.AllowAttrs("nowrap").Matching(
 		regexp.MustCompile(`(?i)|nowrap`),
 	).OnElements("td", "th")
 
 	// "tbody" "tfoot"
 	p.AllowAttrs("align").Matching(CellAlign).OnElements("tbody", "tfoot")
 	p.AllowAttrs("valign").Matching(
 		CellVerticalAlign,
 	).OnElements("tbody", "tfoot")
 }
 
 func (p *Policy) AllowIFrames(vals ...SandboxValue) {
 	p.AllowAttrs("sandbox").OnElements("iframe")
 
 	p.RequireSandboxOnIFrame(vals...)
 }