Class Whitelist
Whitelists define what HTML (elements and attributes) to allow through the cleaner.
Inheritance
Namespace: Supremes.Safety
Assembly: Supremes.dll
Syntax
public sealed class Whitelist : object
Remarks
Everything else is removed.
Start with one of the defaults:
If you need to allow more through (please be careful!), tweak a base whitelist with:
- AddTags(String[])
- AddAttributes(String, String[])
- AddEnforcedAttribute(String, String, String)
- AddProtocols(String, String, String[])
The cleaner and these whitelists assume that you want to clean a body
fragment of HTML (to add user
supplied HTML into a templated page), and not to clean a full HTML document. If the latter is the case, either wrap the
document HTML around the cleaned body HTML, or create a whitelist that allows html
and head
elements as appropriate.
If you are going to extend a whitelist, please be very careful. Make sure you understand what attributes may lead to XSS attack vectors. URL attributes are particularly vulnerable and require careful validation. See http://ha.ckers.org/xss.html for some XSS attack examples.
Constructors
Whitelist()
Create a new, empty whitelist.
Declaration
public Whitelist()
Remarks
Generally it will be better to start with a default prepared whitelist instead.
See Also
Properties
Basic
This whitelist allows a fuller range of text nodes: a, b, blockquote, br, cite, code, dd, dl, dt, em, i, li,
ol, p, pre, q, small, span, strike, strong, sub, sup, u, ul
, and appropriate attributes.
Declaration
public static Whitelist Basic { get; }
Property Value
Type | Description |
---|---|
Whitelist | whitelist |
Remarks
Links (a
elements) can point to http, https, ftp, mailto
, and have an enforced
rel=nofollow
attribute.
Does not allow images.
BasicWithImages
This whitelist allows the same text tags as
Basic
, and also allows img
tags, with appropriate
attributes, with src
pointing to http
or https
.
Declaration
public static Whitelist BasicWithImages { get; }
Property Value
Type | Description |
---|---|
Whitelist | whitelist |
None
This whitelist allows only text nodes: all HTML will be stripped.
Declaration
public static Whitelist None { get; }
Property Value
Type | Description |
---|---|
Whitelist | whitelist |
Relaxed
This whitelist allows a full range of text and structural body HTML: a, b, blockquote, br, caption, cite,
code, col, colgroup, dd, div, dl, dt, em, h1, h2, h3, h4, h5, h6, i, img, li, ol, p, pre, q, small, span, strike, strong, sub,
sup, table, tbody, td, tfoot, th, thead, tr, u, ul
Links do not have an enforced rel=nofollow
attribute, but you can add that if desired.
Declaration
public static Whitelist Relaxed { get; }
Property Value
Type | Description |
---|---|
Whitelist | whitelist |
Remarks
This whitelist allows a full range of text and structural body HTML: a, b, blockquote, br, caption, cite,
code, col, colgroup, dd, div, dl, dt, em, h1, h2, h3, h4, h5, h6, i, img, li, ol, p, pre, q, small, span, strike, strong, sub,
sup, table, tbody, td, tfoot, th, thead, tr, u, ul
Links do not have an enforced rel=nofollow
attribute, but you can add that if desired.
SimpleText
This whitelist allows only simple text formatting: b, em, i, strong, u
.
Declaration
public static Whitelist SimpleText { get; }
Property Value
Type | Description |
---|---|
Whitelist | whitelist |
Remarks
All other HTML (tags and attributes) will be removed.
Methods
AddAttributes(String, String[])
Add a list of allowed attributes to a tag.
Declaration
public Whitelist AddAttributes(string tag, params string[] keys)
Parameters
Type | Name | Description |
---|---|---|
System.String | tag | The tag the attributes are for. The tag will be added to the allowed tag list if necessary. |
System.String[] | keys | List of valid attributes for the tag |
Returns
Type | Description |
---|---|
Whitelist | this (for chaining) |
Remarks
(If an attribute is not allowed on an element, it will be removed.)
E.g.: addAttributes("a", "href", "class")
allows href
and class
attributes
on a
tags.
To make an attribute valid for all tags, use the pseudo tag :all
, e.g.
addAttributes(":all", "class")
.
AddEnforcedAttribute(String, String, String)
Add an enforced attribute to a tag.
Declaration
public Whitelist AddEnforcedAttribute(string tag, string key, string value)
Parameters
Type | Name | Description |
---|---|---|
System.String | tag | The tag the enforced attribute is for. The tag will be added to the allowed tag list if necessary. |
System.String | key | The attribute key |
System.String | value | The enforced attribute value |
Returns
Type | Description |
---|---|
Whitelist | this (for chaining) |
Remarks
An enforced attribute will always be added to the element. If the element already has the attribute set, it will be overridden.
E.g.: AddEnforcedAttribute("a", "rel", "nofollow")
will make all a
tags output as
<a href="..." rel="nofollow">
AddProtocols(String, String, String[])
Add allowed URL protocols for an element's URL attribute.
Declaration
public Whitelist AddProtocols(string tag, string key, params string[] protocols)
Parameters
Type | Name | Description |
---|---|---|
System.String | tag | Tag the URL protocol is for |
System.String | key | Attribute key |
System.String[] | protocols | List of valid protocols |
Returns
Type | Description |
---|---|
Whitelist | this, for chaining |
Remarks
This restricts the possible values of the attribute to URLs with the defined protocol.
E.g.: AddProtocols("a", "href", "ftp", "http", "https")
AddTags(String[])
Add a list of allowed elements to a whitelist.
Declaration
public Whitelist AddTags(params string[] tags)
Parameters
Type | Name | Description |
---|---|---|
System.String[] | tags | tag names to allow |
Returns
Type | Description |
---|---|
Whitelist | this (for chaining) |
Remarks
(If a tag is not allowed, it will be removed from the HTML.)
PreserveRelativeLinks(Boolean)
Configure this Whitelist to preserve relative links in an element's URL attribute, or convert them to absolute links.
Declaration
public Whitelist PreserveRelativeLinks(bool preserve)
Parameters
Type | Name | Description |
---|---|---|
System.Boolean | preserve |
|
Returns
Type | Description |
---|---|
Whitelist | this Whitelist, for chaining. |
Remarks
Configure this Whitelist to preserve relative links in an element's URL attribute, or convert them to absolute
links. By default, this is false: URLs will be made absolute (e.g. start with an allowed protocol, like
e.g.
http://
.
Note that when handling relative links, the input document must have an appropriate
base URI
set when
parsing, so that the link's protocol can be confirmed. Regardless of the setting of the
preserve relative
links
option, the link must be resolvable against the base URI to an allowed protocol; otherwise the attribute
will be removed.