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Class DefaultFilterRules

Concrete implementation of IFilterRules with conservative rules for creating safe HTML code.

Inheritance
System.Object
DefaultFilterRules
Implements
Inherited Members
System.Object.ToString()
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.ReferenceEquals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
Namespace: EPiServer.HtmlParsing
Assembly: EPiServer.Framework.dll
Version: 11.20.7
Syntax
public class DefaultFilterRules : IFilterRules

Constructors

DefaultFilterRules()

Initializes a new instance of the DefaultFilterRules class.

Declaration
public DefaultFilterRules()

DefaultFilterRules(Func<ElementToken, IEnumerable<AttributeToken>>)

Initializes a new instance of the DefaultFilterRules class.

Declaration
public DefaultFilterRules(Func<ElementToken, IEnumerable<AttributeToken>> whiteList)
Parameters
Type Name Description
System.Func<ElementToken, System.Collections.Generic.IEnumerable<AttributeToken>> whiteList

The white list.
Remarks

The whiteList function will get called for each legal value of ElementToken (as defined by the enumeration) and you are expected to return null if the element should be regarded as unsafe, or return an IEnumerable of AttributeToken indicating which attributes that should be allowed for the requested element.

DefaultFilterRules(Func<ElementToken, IEnumerable<AttributeToken>>, DefaultFilterRules)

Initializes a new instance of the DefaultFilterRules class.

Declaration
public DefaultFilterRules(Func<ElementToken, IEnumerable<AttributeToken>> whiteList, DefaultFilterRules originalRules)
Parameters
Type Name Description
System.Func<ElementToken, System.Collections.Generic.IEnumerable<AttributeToken>> whiteList

The white list.
DefaultFilterRules originalRules

The original rules.
Remarks

Basically the same as the constructor that just takes the whiteList parameter, the change here is that we will inherit the whitelist from originalRules and simply append any additional information created by the whiteList function.

Methods

ElementFilterLevel(FilterContext)

Determine the level of filtering to apply to this element.

Declaration
public virtual ElementFilterAction ElementFilterLevel(FilterContext context)
Parameters
Type Name Description
FilterContext context

The filtering context.
Returns
Type Description
ElementFilterAction

An ElementFilterAction enumeration value.

IsSafeAttribute(FilterContext, AttributeToken, String)

Determines whether the attribute is safe in the specified context.

Declaration
public virtual bool IsSafeAttribute(FilterContext context, AttributeToken name, string value)
Parameters
Type Name Description
FilterContext context

The context.
AttributeToken name

The attribute name.
System.String value

The attribute value.
Returns
Type Description
System.Boolean

true if the attribute is safe; otherwise, false.
Remarks

The attribute value will be delivered with quotes removed, i e you do not need to do special quote handling of the attribute value. Note that it is still possible for the value to contain embedded quotes but they are part of the actual value.

IsSafeTextFragment(FilterContext, String)

Determines whether the text fragment should be regarded as safe in the current context.

Declaration
public virtual bool IsSafeTextFragment(FilterContext context, string content)
Parameters
Type Name Description
FilterContext context

The context.
System.String content

The content.
Returns
Type Description
System.Boolean

true if the content is safe; otherwise, false.
Remarks

The HTML filter will call this method when the fragment is a Special Text Fragment, i e the content of a style or script element. If the text fragment is determined to be unsafe (this method returns false) then the surrounding start and end elements will unconditionally be removed, ignoring the return value from KeepNakedElement.

KeepNakedElement(FilterContext)

Determine whether to keep an element even if it contains no attributes.

Declaration
public virtual bool KeepNakedElement(FilterContext context)
Parameters
Type Name Description
FilterContext context

The context.
Returns
Type Description
System.Boolean

true if the element should be kept even when it contains no attributes; otherwise, false.
Remarks

The default behavior should be to return true and special-case the false handling.

Typical scenario is an img element where the src attribute has been removed due to suspected XSS attack. An img without an image to show should be removed completely from the resulting HTML.

Implements

Extension Methods