parlov-elicit 0.4.0

//! `CpIfModifiedSince` -- conditional retrieval via `If-Modified-Since`.
//!
//! Sends `If-Modified-Since: <far future date>` on both baseline and probe.
//! Per RFC 9110 S13.1.3 a server SHOULD respond 304 when the resource has
//! not been modified since the given date. A nonexistent resource returns 404.

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

use crate::context::ScanContext;
use crate::strategy::Strategy;
use crate::types::{ProbeSpec, RiskLevel, StrategyMetadata};
use crate::util::{build_pair, clone_headers_with};

/// Far-future date that guarantees the resource has not been modified since.
const FAR_FUTURE: &str = "Sun, 01 Jan 2034 00:00:00 GMT";

fn metadata() -> StrategyMetadata {
    StrategyMetadata {
        strategy_id: "cp-if-modified-since",
        strategy_name: "Cache Probe: If-Modified-Since",
        risk: RiskLevel::Safe,
    }
}

fn technique() -> Technique {
    Technique {
        id: "cp-if-modified-since",
        name: "If-Modified-Since conditional retrieval",
        oracle_class: OracleClass::Existence,
        vector: Vector::CacheProbing,
        strength: NormativeStrength::Should,
    }
}

/// Elicits existence differentials via `If-Modified-Since` with a far-future date.
pub struct CpIfModifiedSince;

impl Strategy for CpIfModifiedSince {
    fn id(&self) -> &'static str {
        "cp-if-modified-since"
    }

    fn name(&self) -> &'static str {
        "Cache Probe: If-Modified-Since"
    }

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

    fn methods(&self) -> &[Method] {
        &[Method::GET, Method::HEAD]
    }

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

    fn generate(&self, ctx: &ScanContext) -> Vec<ProbeSpec> {
        let mut specs = Vec::with_capacity(2);
        for method in [Method::GET, Method::HEAD] {
            let hdrs = clone_headers_with(&ctx.headers, "if-modified-since", FAR_FUTURE);
            let pair = build_pair(
                ctx,
                method,
                hdrs.clone(),
                hdrs,
                None,
                metadata(),
                technique(),
            );
            specs.push(ProbeSpec::Pair(pair));
        }
        specs
    }
}

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

    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::Safe,
            known_duplicate: None,
            state_field: None,
            alt_credential: None,
            body_template: None,
        }
    }

    #[test]
    fn generates_correct_technique_vector() {
        let specs = CpIfModifiedSince.generate(&make_ctx());
        assert_eq!(specs[0].technique().vector, Vector::CacheProbing);
    }

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

    #[test]
    fn generates_probe_with_correct_header() {
        let specs = CpIfModifiedSince.generate(&make_ctx());
        let ProbeSpec::Pair(pair) = &specs[0] else {
            panic!("expected Pair variant")
        };
        assert_eq!(
            pair.probe.headers.get("if-modified-since").unwrap(),
            FAR_FUTURE
        );
    }

    #[test]
    fn is_always_applicable() {
        assert!(CpIfModifiedSince.is_applicable(&make_ctx()));
    }

    #[test]
    fn risk_is_safe() {
        assert_eq!(CpIfModifiedSince.risk(), RiskLevel::Safe);
    }
}