Struct LoopDetector

struct LoopDetector {
    depth: u8,
    references: u8,
}

An entity loop detector.

Limits:

• Entities depth is 10.
• Maximum number of entity references per entity reference is 255.

Basically, if a text or an attribute has an entity reference and this reference has more than 10 nested references - this is an error.

This is useful for simple loops like:

<!ENTITY a '&b;'>
<!ENTITY b '&a;'>

And, if a text or an attribute has an entity reference and it references more than 255 references - this is an error.

This is useful for cases like billion laughs attack, where depth can be pretty small, but the number of references is exponentially increasing:

<!ENTITY lol "lol">
<!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
<!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
<!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
<!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">

Fields

depth: u8

References depth.

references: u8

Number of references resolved by the root reference.

Implementations

impl LoopDetector

fn inc_depth(&mut self, stream: &Stream<'_>) -> Result<(), Error>

fn dec_depth(&mut self)

fn inc_references(&mut self, stream: &Stream<'_>) -> Result<(), Error>

Trait Implementations

impl Default for LoopDetector

fn default() -> LoopDetector

Returns the “default value” for a type.