parlov-elicit 0.3.0

//! `StateTransitionElicitation` -- probes with a body triggering an invalid state transition.
//!
//! Sends a JSON body containing a known-invalid field value (from `ctx.state_field`)
//! on both baseline and probe requests. The oracle signal is the server returning
//! 409 for an existing resource versus 404 for a nonexistent one.

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

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

fn metadata() -> StrategyMetadata {
    StrategyMetadata {
        strategy_id: "state-transition-elicit",
        strategy_name: "State Transition Elicitation",
        risk: RiskLevel::MethodDestructive,
    }
}

fn technique() -> Technique {
    Technique {
        id: "state-transition",
        name: "Invalid state transition probe",
        oracle_class: OracleClass::Existence,
        vector: Vector::StatusCodeDiff,
        strength: NormativeStrength::May,
    }
}

/// Elicits existence differentials via an invalid state-transition body payload.
pub struct StateTransitionElicitation;

impl Strategy for StateTransitionElicitation {
    fn id(&self) -> &'static str {
        "state-transition-elicit"
    }

    fn name(&self) -> &'static str {
        "State Transition Elicitation"
    }

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

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

    fn is_applicable(&self, ctx: &ScanContext) -> bool {
        ctx.state_field.is_some()
    }

    fn generate(&self, ctx: &ScanContext) -> Vec<ProbeSpec> {
        let Some(sf) = &ctx.state_field else { return vec![] };
        let body = Some(json_body(&[(&sf.field, &sf.value)]));
        let mut specs = Vec::with_capacity(2);
        for method in [Method::PATCH, Method::PUT] {
            let headers =
                clone_headers_with(&ctx.headers, "content-type", "application/json");
            let pair = build_pair(
                ctx, method, headers.clone(), headers,
                body.clone(), metadata(), technique(),
            );
            specs.push(ProbeSpec::Pair(pair));
        }
        specs
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::StateField;
    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::MethodDestructive,
            known_duplicate: None,
            state_field: None,
            alt_credential: None,
            body_template: None,
        }
    }

    fn make_ctx_with_state() -> ScanContext {
        ScanContext {
            state_field: Some(StateField {
                field: "status".to_string(),
                value: "invalid_state".to_string(),
            }),
            ..make_ctx()
        }
    }

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

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

    #[test]
    fn is_applicable_true_when_state_field_some() {
        assert!(StateTransitionElicitation.is_applicable(&make_ctx_with_state()));
    }

    #[test]
    fn generate_returns_two_items_when_applicable() {
        assert_eq!(StateTransitionElicitation.generate(&make_ctx_with_state()).len(), 2);
    }

    #[test]
    fn probe_body_contains_state_field_as_valid_json() {
        let specs = StateTransitionElicitation.generate(&make_ctx_with_state());
        let ProbeSpec::Pair(pair) = &specs[0] else { panic!("expected Pair") };
        let body = pair.probe.body.as_deref().expect("body must be present");
        let parsed: serde_json::Value = serde_json::from_slice(body).expect("valid JSON");
        assert_eq!(parsed["status"], "invalid_state");
    }

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