parlov-elicit 0.3.0

//! `IfMatchElicitation` -- probes with a bogus `If-Match` precondition header.
//!
//! Sends `If-Match: "bogus-etag"` on the probe request. Per RFC 9110 S13.1.1 a
//! server MUST respond 412 when the precondition fails on an existing resource,
//! but returns 404 for a nonexistent one. The differential reveals existence.

use http::Method;
use parlov_core::{
    NormativeStrength, OracleClass, ProbeDefinition, Technique, Vector,
};

use crate::strategy::Strategy;
use crate::types::{ProbePair, ProbeSpec, RiskLevel, StrategyMetadata};
use crate::util::{clone_headers_with, json_body, substitute_url};
use crate::ScanContext;

fn metadata() -> StrategyMetadata {
    StrategyMetadata {
        strategy_id: "if-match-elicit",
        strategy_name: "If-Match Elicitation",
        risk: RiskLevel::MethodDestructive,
    }
}

fn technique() -> Technique {
    Technique {
        id: "if-match",
        name: "If-Match precondition probe",
        oracle_class: OracleClass::Existence,
        vector: Vector::StatusCodeDiff,
        strength: NormativeStrength::Must,
    }
}

/// Elicits existence differentials via an `If-Match` precondition header.
pub struct IfMatchElicitation;

impl Strategy for IfMatchElicitation {
    fn id(&self) -> &'static str {
        "if-match-elicit"
    }

    fn name(&self) -> &'static str {
        "If-Match Elicitation"
    }

    fn risk(&self) -> RiskLevel {
        RiskLevel::MethodDestructive
    }

    fn methods(&self) -> &[Method] {
        &[Method::PUT, Method::PATCH, Method::DELETE]
    }

    fn is_applicable(&self, _ctx: &ScanContext) -> bool {
        true
    }

    fn generate(&self, ctx: &ScanContext) -> Vec<ProbeSpec> {
        let mut specs = Vec::with_capacity(3);
        let baseline_url = substitute_url(&ctx.target, &ctx.baseline_id);
        let probe_url = substitute_url(&ctx.target, &ctx.probe_id);
        let probe_headers = clone_headers_with(&ctx.headers, "if-match", "\"bogus-etag\"");
        for method in [Method::PUT, Method::PATCH, Method::DELETE] {
            let body = if method == Method::DELETE {
                None
            } else {
                Some(json_body(&[]))
            };
            let pair = ProbePair {
                baseline: ProbeDefinition {
                    url: baseline_url.clone(),
                    method: method.clone(),
                    headers: ctx.headers.clone(),
                    body: body.clone(),
                },
                probe: ProbeDefinition {
                    url: probe_url.clone(),
                    method,
                    headers: probe_headers.clone(),
                    body,
                },
                metadata: metadata(),
                technique: technique(),
            };
            specs.push(ProbeSpec::Pair(pair));
        }
        specs
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use http::{HeaderMap, Method};

    fn make_ctx() -> ScanContext {
        ScanContext {
            target: "https://api.example.com/users/{id}".to_string(),
            baseline_id: "1001".to_string(),
            probe_id: "9999".to_string(),
            headers: HeaderMap::new(),
            max_risk: RiskLevel::MethodDestructive,
            known_duplicate: None,
            state_field: None,
            alt_credential: None,
            body_template: None,
        }
    }

    #[test]
    fn risk_is_method_destructive() {
        assert_eq!(IfMatchElicitation.risk(), RiskLevel::MethodDestructive);
    }

    #[test]
    fn generate_returns_three_items() {
        assert_eq!(IfMatchElicitation.generate(&make_ctx()).len(), 3);
    }

    #[test]
    fn probe_has_if_match_bogus_etag() {
        let specs = IfMatchElicitation.generate(&make_ctx());
        let ProbeSpec::Pair(pair) = &specs[0] else { panic!("expected Pair") };
        assert_eq!(pair.probe.headers.get("if-match").unwrap(), "\"bogus-etag\"");
    }

    #[test]
    fn delete_pair_probe_has_no_body() {
        let specs = IfMatchElicitation.generate(&make_ctx());
        let del_pair = specs.iter().find_map(|s| {
            if let ProbeSpec::Pair(p) = s {
                if p.probe.method == Method::DELETE { return Some(p); }
            }
            None
        });
        assert!(del_pair.expect("DELETE pair must exist").probe.body.is_none());
    }

    #[test]
    fn technique_strength_is_must() {
        let specs = IfMatchElicitation.generate(&make_ctx());
        assert_eq!(specs[0].technique().strength, NormativeStrength::Must);
    }
}