parlov-elicit 0.5.0

//! `EmgQueryValidation` -- resource-aware query parameter validation differential.
//!
//! Appends `?fields=_parlov_invalid` to both baseline and probe URLs. If the
//! server resolves the resource ID before validating query parameters, an
//! existing resource returns a 400 "field not permitted" while a nonexistent
//! resource returns 404, revealing existence through execution order.

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

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

static METADATA: StrategyMetadata = StrategyMetadata {
    strategy_id: "emg-query-validation",
    strategy_name: "EMG: Query Parameter Validation",
    risk: RiskLevel::Safe,
};

static TECHNIQUE: Technique = Technique {
    id: "emg-query-validation",
    name: "Resource-aware query validation differential",
    oracle_class: OracleClass::Existence,
    vector: Vector::ErrorMessageGranularity,
    strength: NormativeStrength::May,
    normalization_weight: None,
    inverted_signal_weight: None,
    method_relevant: false,
    parser_relevant: false,
    applicability: always_applicable,
    contradiction_surface: SignalSurface::Body,
};

/// Appends `param` to `url`, using `'?'` if no query string is present, `'&'` otherwise.
fn append_query_param(url: &mut String, param: &str) {
    let sep = if url.contains('?') { '&' } else { '?' };
    url.push(sep);
    url.push_str(param);
}

/// Elicits existence differentials via query parameter validation ordering.
pub struct EmgQueryValidation;

impl Strategy for EmgQueryValidation {
    fn metadata(&self) -> &'static StrategyMetadata {
        &METADATA
    }

    fn technique_def(&self) -> &'static Technique {
        &TECHNIQUE
    }

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

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

    fn generate(&self, ctx: &ScanContext) -> Vec<ProbeSpec> {
        let mut pair = build_pair(
            ctx,
            Method::GET,
            ctx.headers.clone(),
            ctx.headers.clone(),
            None,
            METADATA.clone(),
            TECHNIQUE,
        );
        append_query_param(&mut pair.baseline.url, "fields=_parlov_invalid");
        append_query_param(&mut pair.probe.url, "fields=_parlov_invalid");
        vec![ProbeSpec::Pair(pair)]
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::test_utils::minimal_ctx;

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

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

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

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

    #[test]
    fn generates_get_method() {
        let specs = EmgQueryValidation.generate(&minimal_ctx());
        let ProbeSpec::Pair(pair) = &specs[0] else {
            panic!("expected Pair variant")
        };
        assert_eq!(pair.baseline.method, Method::GET);
    }

    #[test]
    fn urls_have_query_param() {
        let specs = EmgQueryValidation.generate(&minimal_ctx());
        let ProbeSpec::Pair(pair) = &specs[0] else {
            panic!("expected Pair variant")
        };
        assert!(
            pair.baseline.url.contains("?fields=_parlov_invalid"),
            "baseline URL missing query param: {}",
            pair.baseline.url
        );
        assert!(
            pair.probe.url.contains("?fields=_parlov_invalid"),
            "probe URL missing query param: {}",
            pair.probe.url
        );
    }

    #[test]
    fn urls_use_ampersand_when_query_already_present() {
        let ctx = ScanContext {
            target: "https://api.example.com/users/{id}?version=2".to_string(),
            ..minimal_ctx()
        };
        let specs = EmgQueryValidation.generate(&ctx);
        let ProbeSpec::Pair(pair) = &specs[0] else {
            panic!("expected Pair variant")
        };
        assert!(
            pair.baseline
                .url
                .contains("?version=2&fields=_parlov_invalid"),
            "baseline URL has malformed query string: {}",
            pair.baseline.url
        );
        assert!(
            pair.probe.url.contains("?version=2&fields=_parlov_invalid"),
            "probe URL has malformed query string: {}",
            pair.probe.url
        );
    }
}