huskarl-core 0.6.4

use std::{
    collections::HashMap,
    sync::{Arc, Mutex, RwLock},
    time::Duration,
};

use base64::prelude::*;
use bon::Builder;
use http::{Method, Uri, uri::Scheme};
use serde::Serialize;
use sha2::{Digest as _, Sha256};

use crate::{
    crypto::signer::{
        AsymmetricJwsSigner, AsymmetricJwsSignerSelector, BoxedAsymmetricJwsSignerSelector,
        JwsSigner,
    },
    dpop::{AuthorizationServerDPoP, ResourceServerDPoP},
    jwt::{JwsSerializationError, Jwt},
    secrets::SecretString,
};

// Used internally to track the origin value for a Uri (nonces are matched by origin).
type Origin = (Option<Scheme>, Option<String>, Option<u16>);

impl<Sgn: AsymmetricJwsSignerSelector> super::sealed::Sealed for DPoP<Sgn> {}

/// This respresents a grant with the ability to create DPoP-bound tokens and sign requests with them.
#[derive(Debug, Clone, Builder)]
pub struct DPoP<Sgn: AsymmetricJwsSignerSelector = BoxedAsymmetricJwsSignerSelector> {
    signer: Sgn,
    #[builder(skip)]
    nonce: Arc<Mutex<Option<Arc<String>>>>,
}

impl<Sgn: AsymmetricJwsSignerSelector> AuthorizationServerDPoP for DPoP<Sgn> {
    type Error = JwsSerializationError<<Sgn::Signer as JwsSigner>::Error>;
    type ResourceServerDPoP = ResourceDPoP<Sgn>;

    fn update_nonce(&self, nonce: String) {
        // If the lock is poisoned (a thread panicked while holding it), we recover
        // the guard and proceed. A stale nonce just causes the server to reject the
        // next DPoP proof and return a fresh nonce, so the worst case is one extra
        // round-trip rather than a hard failure.
        let _ = self
            .nonce
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .insert(Arc::new(nonce));
    }

    fn get_current_thumbprint(&self) -> Option<String> {
        Some(self.signer.select_signer().public_key_jwk().thumbprint())
    }

    async fn proof(
        &self,
        method: &Method,
        uri: &Uri,
        dpop_jkt: Option<&str>,
    ) -> Result<Option<SecretString>, Self::Error> {
        // See comment in `update_nonce` for why poison recovery is intentional here.
        let nonce = self
            .nonce
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .clone();

        let Some(dpop_jkt) = dpop_jkt else {
            return Err(JwsSerializationError::NoThumbprint);
        };

        let signer = self
            .signer
            .select_signer_by_thumbprint(dpop_jkt)
            .ok_or(JwsSerializationError::NoMatchingKeyForThumbprint)?;

        sign_proof(&signer, method, uri, None, nonce).await
    }

    fn to_resource_server_dpop(&self) -> Self::ResourceServerDPoP {
        ResourceDPoP::builder().signer(self.signer.clone()).build()
    }
}

impl<Sgn: AsymmetricJwsSignerSelector> super::sealed::Sealed for ResourceDPoP<Sgn> {}

/// This respresents the ability to create proofs for resource servers from DPoP-bound access tokens.
#[derive(Debug, Clone, Builder)]
pub struct ResourceDPoP<Sgn: AsymmetricJwsSignerSelector> {
    signer: Sgn,
    #[builder(default)]
    nonces: Arc<RwLock<HashMap<Origin, Arc<String>>>>,
}

impl<Sgn: AsymmetricJwsSignerSelector> ResourceServerDPoP for ResourceDPoP<Sgn> {
    type Error = JwsSerializationError<<Sgn::Signer as JwsSigner>::Error>;

    fn update_nonce(&self, uri: &Uri, nonce: String) {
        let origin = origin_from_uri(uri);
        // If the lock is poisoned (a thread panicked while holding it), we recover
        // the guard and proceed. A stale nonce just causes the server to reject the
        // next DPoP proof and return a fresh nonce, so the worst case is one extra
        // round-trip rather than a hard failure.
        self.nonces
            .write()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .insert(origin, Arc::new(nonce));
    }

    async fn proof(
        &self,
        method: &Method,
        uri: &Uri,
        access_token: &SecretString,
        dpop_jkt: &str,
    ) -> Result<Option<SecretString>, Self::Error> {
        let origin = origin_from_uri(uri);
        // See comment in `update_nonce` for why poison recovery is intentional here.
        let nonce = self
            .nonces
            .read()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
            .get(&origin)
            .cloned();

        let signer = self
            .signer
            .select_signer_by_thumbprint(dpop_jkt)
            .ok_or(JwsSerializationError::NoMatchingKeyForThumbprint)?;

        sign_proof(
            &signer,
            method,
            uri,
            Some(access_token.expose_secret()),
            nonce,
        )
        .await
    }
}

fn origin_from_uri(uri: &Uri) -> Origin {
    (
        uri.scheme().cloned(),
        uri.host().map(str::to_string),
        uri.port_u16(),
    )
}

async fn sign_proof<Sgn: AsymmetricJwsSigner>(
    signer: &Sgn,
    htm: &Method,
    htu: &Uri,
    token: Option<&str>,
    nonce: Option<Arc<String>>,
) -> Result<Option<SecretString>, JwsSerializationError<Sgn::Error>> {
    #[derive(Debug, Clone, Serialize)]
    struct DPoPClaims<'a> {
        htm: &'a str,
        htu: String,
        #[serde(skip_serializing_if = "Option::is_none")]
        ath: Option<String>,
        #[serde(skip_serializing_if = "Option::is_none")]
        nonce: Option<Arc<String>>,
    }

    let extra_claims = DPoPClaims {
        htm: htm.as_str(),
        htu: normalize_uri_for_dpop(htu)
            .map_err(|source| JwsSerializationError::NormalizeUri { source })?
            .to_string(),
        ath: token.map(hash_access_token_for_dpop),
        nonce,
    };

    let jwt = Jwt::builder()
        .typ("dpop+jwt")
        .issued_now_expires_after(Duration::from_mins(1))
        .jwk(signer.public_key_jwk().into_owned())
        .claims(extra_claims)
        .build();

    jwt.to_jws_compact(signer).await.map(Some)
}

/// Normalizes a URI for inclusion in a `DPoP` proof by stripping query and fragment components.
///
/// # Errors
///
/// Returns an error if the resulting URI cannot be constructed (e.g. invalid authority).
pub fn normalize_uri_for_dpop(uri: &Uri) -> Result<Uri, http::Error> {
    let mut builder = http::uri::Builder::new();

    if let Some(scheme) = uri.scheme() {
        builder = builder.scheme(scheme.clone());
    }
    if let Some(authority) = uri.authority() {
        builder = builder.authority(authority.clone());
    }
    builder = builder.path_and_query(uri.path());
    builder.build()
}

/// Computes the SHA-256 `ath` hash of an access token for inclusion in a `DPoP` proof.
#[must_use]
pub fn hash_access_token_for_dpop(access_token: &str) -> String {
    let mut hasher = Sha256::new();
    hasher.update(access_token.as_bytes());
    let hash_digest = hasher.finalize();
    BASE64_URL_SAFE_NO_PAD.encode(hash_digest)
}

#[cfg(test)]
mod tests {
    use std::{borrow::Cow, convert::Infallible};

    use base64::prelude::*;

    use super::*;
    use crate::{
        crypto::signer::{
            AsymmetricJwsSigner, AsymmetricJwsSignerSelector, JwsSigner, JwsSignerSelector,
        },
        dpop::{AuthorizationServerDPoP, ResourceServerDPoP},
        jwk::{EcPublicKey, PublicJwk},
    };

    fn mock_public_jwk() -> PublicJwk {
        PublicJwk::builder()
            .key(
                EcPublicKey::builder()
                    .crv("P-256")
                    .x([1u8; 32])
                    .y([2u8; 32])
                    .build(),
            )
            .build()
    }

    #[derive(Debug, Clone)]
    struct MockAsymmetricJwsSigner {
        jwk: PublicJwk,
    }

    impl JwsSigner for MockAsymmetricJwsSigner {
        type Error = Infallible;
        fn jws_algorithm(&self) -> Cow<'_, str> {
            "ES256".into()
        }
        fn key_id(&self) -> Option<Cow<'_, str>> {
            None
        }
        async fn sign(&self, _input: &[u8]) -> Result<Vec<u8>, Infallible> {
            Ok(vec![0xCA, 0xFE])
        }
    }

    impl AsymmetricJwsSigner for MockAsymmetricJwsSigner {
        fn public_key_jwk(&self) -> Cow<'_, PublicJwk> {
            Cow::Borrowed(&self.jwk)
        }
    }

    impl JwsSignerSelector for MockAsymmetricJwsSigner {
        type Signer = Self;
        fn select_signer(&self) -> Self {
            self.clone()
        }
    }

    impl AsymmetricJwsSignerSelector for MockAsymmetricJwsSigner {
        fn select_signer_by_thumbprint(&self, thumbprint: &str) -> Option<Self::Signer> {
            if thumbprint == self.jwk.thumbprint() {
                Some(self.clone())
            } else {
                None
            }
        }
    }

    // --- normalize_uri_for_dpop ---

    #[test]
    fn normalize_uri_strips_query_and_fragment() {
        let uri: Uri = "https://example.com/path?query=1#frag".parse().unwrap();
        let normalized = normalize_uri_for_dpop(&uri).unwrap();
        assert_eq!(normalized.to_string(), "https://example.com/path");
    }

    #[test]
    fn normalize_uri_passthrough() {
        let uri: Uri = "https://example.com/path".parse().unwrap();
        let normalized = normalize_uri_for_dpop(&uri).unwrap();
        assert_eq!(normalized.to_string(), "https://example.com/path");
    }

    #[test]
    fn normalize_uri_scheme_and_authority_only() {
        let uri: Uri = "https://example.com".parse().unwrap();
        let normalized = normalize_uri_for_dpop(&uri).unwrap();
        assert_eq!(normalized.to_string(), "https://example.com/");
    }

    // --- hash_access_token_for_dpop ---

    #[test]
    fn hash_access_token_known_value() {
        // SHA-256 of "test-token" = known value
        let hash = hash_access_token_for_dpop("test-token");
        // Verify it's a valid base64url string of 32 bytes
        let decoded = BASE64_URL_SAFE_NO_PAD.decode(&hash).unwrap();
        assert_eq!(decoded.len(), 32);

        // Same input always produces same output
        assert_eq!(hash, hash_access_token_for_dpop("test-token"));
        // Different input produces different output
        assert_ne!(hash, hash_access_token_for_dpop("other-token"));
    }

    // --- DPoP::proof ---

    #[tokio::test]
    async fn dpop_proof_success() {
        let jwk = mock_public_jwk();
        let thumbprint = jwk.thumbprint();
        let signer = MockAsymmetricJwsSigner { jwk };
        let dpop = DPoP::builder().signer(signer).build();

        let uri: Uri = "https://auth.example.com/token?foo=bar".parse().unwrap();
        let result = dpop
            .proof(&Method::POST, &uri, Some(&thumbprint))
            .await
            .unwrap();

        let token = result.unwrap();
        let parts: Vec<&str> = token.expose_secret().split('.').collect();
        assert_eq!(parts.len(), 3);

        // Decode header
        let header: serde_json::Value =
            serde_json::from_slice(&BASE64_URL_SAFE_NO_PAD.decode(parts[0]).unwrap()).unwrap();
        assert_eq!(header["typ"], "dpop+jwt");
        assert_eq!(header["alg"], "ES256");
        assert!(header.get("jwk").is_some());

        // Decode claims
        let claims: serde_json::Value =
            serde_json::from_slice(&BASE64_URL_SAFE_NO_PAD.decode(parts[1]).unwrap()).unwrap();
        assert_eq!(claims["htm"], "POST");
        // htu should not have query string
        let htu = claims["htu"].as_str().unwrap();
        assert!(!htu.contains('?'));
        assert!(htu.starts_with("https://auth.example.com"));
        assert!(claims.get("jti").is_some());
        assert!(claims.get("iat").is_some());
        assert!(claims.get("exp").is_some());
    }

    #[tokio::test]
    async fn dpop_proof_no_thumbprint() {
        let signer = MockAsymmetricJwsSigner {
            jwk: mock_public_jwk(),
        };
        let dpop = DPoP::builder().signer(signer).build();
        let uri: Uri = "https://auth.example.com/token".parse().unwrap();

        let result = dpop.proof(&Method::POST, &uri, None).await;
        assert!(matches!(result, Err(JwsSerializationError::NoThumbprint)));
    }

    #[tokio::test]
    async fn dpop_proof_wrong_thumbprint() {
        let signer = MockAsymmetricJwsSigner {
            jwk: mock_public_jwk(),
        };
        let dpop = DPoP::builder().signer(signer).build();
        let uri: Uri = "https://auth.example.com/token".parse().unwrap();

        let result = dpop
            .proof(&Method::POST, &uri, Some("wrong-thumbprint"))
            .await;
        assert!(matches!(
            result,
            Err(JwsSerializationError::NoMatchingKeyForThumbprint)
        ));
    }

    #[tokio::test]
    async fn dpop_proof_with_nonce() {
        let jwk = mock_public_jwk();
        let thumbprint = jwk.thumbprint();
        let signer = MockAsymmetricJwsSigner { jwk };
        let dpop = DPoP::builder().signer(signer).build();

        dpop.update_nonce("server-nonce-123".into());

        let uri: Uri = "https://auth.example.com/token".parse().unwrap();
        let result = dpop
            .proof(&Method::POST, &uri, Some(&thumbprint))
            .await
            .unwrap();
        let token = result.unwrap();
        let parts: Vec<&str> = token.expose_secret().split('.').collect();
        let claims: serde_json::Value =
            serde_json::from_slice(&BASE64_URL_SAFE_NO_PAD.decode(parts[1]).unwrap()).unwrap();
        assert_eq!(claims["nonce"], "server-nonce-123");
    }

    // --- ResourceDPoP ---

    #[tokio::test]
    async fn resource_dpop_proof_has_ath() {
        let jwk = mock_public_jwk();
        let thumbprint = jwk.thumbprint();
        let signer = MockAsymmetricJwsSigner { jwk };
        let dpop = DPoP::builder().signer(signer).build();
        let resource_dpop = dpop.to_resource_server_dpop();

        let uri: Uri = "https://api.example.com/resource".parse().unwrap();
        let access_token = SecretString::new("my-access-token");

        let result = resource_dpop
            .proof(&Method::GET, &uri, &access_token, &thumbprint)
            .await
            .unwrap();
        let token = result.unwrap();
        let parts: Vec<&str> = token.expose_secret().split('.').collect();
        let claims: serde_json::Value =
            serde_json::from_slice(&BASE64_URL_SAFE_NO_PAD.decode(parts[1]).unwrap()).unwrap();
        assert!(claims.get("ath").is_some());
        // Verify ath matches hash of access token
        assert_eq!(claims["ath"], hash_access_token_for_dpop("my-access-token"));
    }

    #[tokio::test]
    async fn resource_dpop_per_origin_nonce() {
        let jwk = mock_public_jwk();
        let thumbprint = jwk.thumbprint();
        let signer = MockAsymmetricJwsSigner { jwk };
        let dpop = DPoP::builder().signer(signer).build();
        let resource_dpop = dpop.to_resource_server_dpop();

        let uri1: Uri = "https://api1.example.com/resource".parse().unwrap();
        let uri2: Uri = "https://api2.example.com/resource".parse().unwrap();

        resource_dpop.update_nonce(&uri1, "nonce-1".into());
        resource_dpop.update_nonce(&uri2, "nonce-2".into());

        let at = SecretString::new("token");

        let result1 = resource_dpop
            .proof(&Method::GET, &uri1, &at, &thumbprint)
            .await
            .unwrap()
            .unwrap();
        let parts1: Vec<&str> = result1.expose_secret().split('.').collect();
        let claims1: serde_json::Value =
            serde_json::from_slice(&BASE64_URL_SAFE_NO_PAD.decode(parts1[1]).unwrap()).unwrap();
        assert_eq!(claims1["nonce"], "nonce-1");

        let result2 = resource_dpop
            .proof(&Method::GET, &uri2, &at, &thumbprint)
            .await
            .unwrap()
            .unwrap();
        let parts2: Vec<&str> = result2.expose_secret().split('.').collect();
        let claims2: serde_json::Value =
            serde_json::from_slice(&BASE64_URL_SAFE_NO_PAD.decode(parts2[1]).unwrap()).unwrap();
        assert_eq!(claims2["nonce"], "nonce-2");
    }
}