d-OAuth-Server/tests/e2e_grants.rs

//! `test(e2e_)` token-grant rows over the live router: the wired dispatcher.
//!
//! Every test boots the REAL production router ([`d_oauth::routes::build_router`])
//! over a REAL loopback socket against REAL testcontainers Postgres + Redis
//! and asserts only observable HTTP behavior: the five grants dispatch, the
//! sender-constraint matrix holds, and every failure is the specified 4xx.
//!
//! The `oauth2` crate drives the baseline shapes (PKCE material, code
//! redemption, client-credentials exchange); DPoP proofs and the extension
//! grants are hand-rolled `reqwest`.

#[path = "e2e/harness.rs"]
mod harness;

#[path = "e2e/dpop.rs"]
mod dpop;

#[path = "e2e/clients.rs"]
mod clients;

use d_oauth::db::TokenEndpointAuthMethod;
use d_oauth::protocol::code::{CodeClientKind, CodeIssueRequest, CodeIssuer, IssuedCode};
use d_oauth::protocol::scope::ScopeSet;
use d_oauth::protocol::token::ClientKind;
use dpop::DpopKey;
use harness::{
  TestError, World, attach_redirect, ensure, fail, json_body, open_rate_limit, seed_client,
  seed_client_bound, seed_scope,
};
use oauth2::TokenResponse as _;

/// Fixture confidential client.
const CLIENT_ID: &str = "e2e-grant-client";
/// Fixture secret.
const CLIENT_SECRET: &str = "e2e-grant-secret-1a2b3c4d5e6f708192";
/// Fixture public client (DPoP-bound by policy).
const PUBLIC_ID: &str = "e2e-grant-public";
/// Registered loopback redirect.
const REDIRECT_URI: &str = "http://127.0.0.1:9/cb";

/// One world plus seeded confidential + public clients, scopes, redirect.
async fn setup() -> Result<World, TestError> {
  let world = World::start(open_rate_limit()).await?;
  seed_client(
    &world.pool,
    CLIENT_ID,
    Some(CLIENT_SECRET),
    &[
      "authorization_code",
      "refresh_token",
      "client_credentials",
      "urn:ietf:params:oauth:grant-type:device_code",
      "urn:ietf:params:oauth:grant-type:token-exchange",
    ],
    "read write",
    TokenEndpointAuthMethod::ClientSecretBasic,
  )
  .await?;
  seed_client(
    &world.pool,
    PUBLIC_ID,
    None,
    &["authorization_code", "refresh_token"],
    "read",
    TokenEndpointAuthMethod::None,
  )
  .await?;
  seed_scope(&world.pool, "read").await?;
  seed_scope(&world.pool, "write").await?;
  attach_redirect(&world.pool, CLIENT_ID, REDIRECT_URI).await?;
  attach_redirect(&world.pool, PUBLIC_ID, REDIRECT_URI).await?;
  Ok(world)
}

/// Assert a token failure is the specified OAuth error, minting nothing.
fn ensure_error(status: reqwest::StatusCode, body: &str, code: &str) -> Result<(), TestError> {
  ensure(
    status == reqwest::StatusCode::BAD_REQUEST,
    format!("must be 400, got {status}: {body}"),
  )?;
  let value = json_body(body)?;
  ensure(
    value["error"] == code,
    format!("failure must be {code}, got {value}"),
  )?;
  ensure(!body.contains("access_token"), "failure must mint nothing")?;
  ensure(
    !body.contains(CLIENT_SECRET),
    "failure must not leak the secret",
  )?;
  Ok(())
}

/// PKCE downgrade is rejected at the authorize layer (`plain` → 302
/// `invalid_request`); redemption of a stale code is `invalid_grant`.
#[tokio::test]
async fn e2e_pkce_downgrade_rejected() -> Result<(), TestError> {
  let world = setup().await?;
  let (challenge, _verifier) = oauth2_pkce();
  let (status, headers, _) = world
    .get(
      &format!(
        "/authorize?client_id={PUBLIC_ID}&redirect_uri={}&response_type=code\
         &code_challenge={challenge}&code_challenge_method=plain",
        encoded(REDIRECT_URI)
      ),
      &[],
    )
    .await?;
  ensure(status == reqwest::StatusCode::FOUND, "plain PKCE must 302")?;
  let location = location_of(&headers)?;
  ensure(
    location.contains("error=invalid_request"),
    "plain PKCE must be invalid_request",
  )?;

  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "authorization_code"),
        ("code", "stale-code"),
        ("redirect_uri", REDIRECT_URI),
        ("client_id", CLIENT_ID),
      ],
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;
  Ok(())
}

/// Code replay and cross-client redemption never succeed: an unknown or
/// already-consumed code is always `invalid_grant`.
#[tokio::test]
async fn e2e_code_replay_expiry_cross_client_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let redemption = [
    ("grant_type", "authorization_code"),
    ("code", "one-time-code"),
    ("redirect_uri", REDIRECT_URI),
    ("client_id", CLIENT_ID),
  ];
  for attempt in 1..=2 {
    let (status, _, body) = world
      .post_form("/token", &redemption, Some((CLIENT_ID, CLIENT_SECRET)), &[])
      .await?;
    ensure_error(status, &body, "invalid_grant")
      .map_err(|error| fail(format!("replay attempt {attempt}: {error}")))?;
  }
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "authorization_code"),
        ("code", "one-time-code"),
        ("redirect_uri", REDIRECT_URI),
        ("client_id", PUBLIC_ID),
      ],
      None,
      &[],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;
  Ok(())
}

/// A replayed DPoP `jti` mints once and is `invalid_dpop_proof` on reuse.
#[tokio::test]
async fn e2e_dpop_jti_replay_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let key = DpopKey::generate()?;
  let htu = format!("{}/token", world.state.config.issuer);
  let proof = key.proof("POST", &htu)?;
  let attempt = [("grant_type", "client_credentials")];

  let (status, _, body) = world
    .post_form(
      "/token",
      &attempt,
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[("dpop", proof.as_str())],
    )
    .await?;
  ensure(
    status == reqwest::StatusCode::OK,
    format!("fresh proof must mint: {status} {body}"),
  )?;
  let value = json_body(&body)?;
  ensure(
    value["token_type"] == "DPoP",
    "proof-bound issuance must be DPoP",
  )?;

  let (status, _, body) = world
    .post_form(
      "/token",
      &attempt,
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[("dpop", proof.as_str())],
    )
    .await?;
  ensure_error(status, &body, "invalid_dpop_proof")?;
  Ok(())
}

/// A DPoP proof bound to the wrong `htu` is `invalid_dpop_proof`.
#[tokio::test]
async fn e2e_dpop_htu_mismatch_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let key = DpopKey::generate()?;
  let wrong = key.proof("POST", "https://auth.example.test/wrong-token")?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[("grant_type", "client_credentials")],
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[("dpop", wrong.as_str())],
    )
    .await?;
  ensure_error(status, &body, "invalid_dpop_proof")?;
  Ok(())
}

/// Refresh reuse rotates once, then `invalid_grant` and cascade-revokes the
/// grant family (the first access token reads inactive).
#[tokio::test]
async fn e2e_refresh_rotation_reuse_cascade_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let key = DpopKey::generate()?;
  let jkt =
    d_oauth::jose::jwk::thumbprint(&key.jwk()).map_err(|error| fail(format!("jwk: {error}")))?;
  let minted = world
    .mint(CLIENT_ID, "read", ClientKind::Confidential, Some(&jkt))
    .await?;
  let htu = format!("{}/token", world.state.config.issuer);
  let refresh = [
    ("grant_type", "refresh_token"),
    ("refresh_token", minted.refresh_token.as_str()),
  ];
  let first_proof = key.proof("POST", &htu)?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &refresh,
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[("dpop", first_proof.as_str())],
    )
    .await?;
  ensure(
    status == reqwest::StatusCode::OK,
    format!("first rotation must mint: {status} {body}"),
  )?;
  let rotated = json_body(&body)?;
  ensure(
    rotated["access_token"]
      .as_str()
      .is_some_and(|t| !t.is_empty()),
    "rotation must return an access token",
  )?;
  ensure(
    rotated["refresh_token"]
      .as_str()
      .is_some_and(|t| !t.is_empty()),
    "rotation must return a refresh token",
  )?;

  let second_proof = key.proof("POST", &htu)?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &refresh,
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[("dpop", second_proof.as_str())],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;

  // The replay mapping masks the tombstone by design (a same-request retry
  // is rejected without cascading); expire it to exercise the reuse path.
  let mut conn = world.state.redis.clone();
  let found = world
    .service
    .find_refresh(&mut conn, &world.store, &minted.refresh_token)
    .await
    .map_err(|error| fail(format!("refresh lookup: {error}")))?
    .ok_or_else(|| fail("rotated refresh token must resolve to its tombstone"))?;
  let request_id = world
    .service
    .request_id_for(&found.hash)
    .map_err(|error| fail(format!("request id: {error}")))?;
  let _: () = redis::cmd("DEL")
    .arg(world.store.rotation_map_key(&request_id))
    .query_async(&mut conn)
    .await?;

  let third_proof = key.proof("POST", &htu)?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &refresh,
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[("dpop", third_proof.as_str())],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;

  let first_access = minted.access_token.as_str();
  let (status, _, body) = world
    .post_form(
      "/introspect",
      &[("token", first_access)],
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[],
    )
    .await?;
  ensure(
    status == reqwest::StatusCode::OK,
    "introspection must answer",
  )?;
  ensure(
    json_body(&body)?["active"] == false,
    "reuse must cascade-revoke the rotated access token",
  )?;
  Ok(())
}

/// Concurrent rotations of one refresh token: exactly one mints, every other
/// racer is `invalid_grant`.
#[tokio::test]
async fn e2e_concurrent_rotation_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let key = DpopKey::generate()?;
  let jkt =
    d_oauth::jose::jwk::thumbprint(&key.jwk()).map_err(|error| fail(format!("jwk: {error}")))?;
  let minted = world
    .mint(CLIENT_ID, "read", ClientKind::Confidential, Some(&jkt))
    .await?;
  let htu = format!("{}/token", world.state.config.issuer);
  let mut proofs = Vec::with_capacity(8);
  for _ in 0..8 {
    proofs.push(key.proof("POST", &htu)?);
  }
  let mut set = tokio::task::JoinSet::new();
  let client = reqwest::Client::builder()
    .redirect(reqwest::redirect::Policy::none())
    .timeout(std::time::Duration::from_secs(60))
    .build()?;
  for proof in proofs {
    let client = client.clone();
    let base = world.base.clone();
    let refresh = minted.refresh_token.clone();
    set.spawn(async move {
      client
        .post(format!("{base}/token"))
        .basic_auth(CLIENT_ID, Some(CLIENT_SECRET))
        .header("dpop", proof)
        .form(&[
          ("grant_type", "refresh_token"),
          ("refresh_token", refresh.as_str()),
        ])
        .send()
        .await
    });
  }
  let mut successes = 0;
  let mut rejections = 0;
  let mut unavailable = 0;
  while let Some(outcome) = set.join_next().await {
    let response = outcome.map_err(|error| fail(format!("join failed: {error}")))??;
    let status = response.status();
    let body = response.text().await?;
    if status == reqwest::StatusCode::OK {
      successes += 1;
    } else if status == reqwest::StatusCode::SERVICE_UNAVAILABLE {
      ensure(
        json_body(&body)?["error"] == "temporarily_unavailable",
        format!("store outage must be temporarily_unavailable: {body}"),
      )?;
      ensure(!body.contains("access_token"), "failure must mint nothing")?;
      unavailable += 1;
    } else {
      ensure_error(status, &body, "invalid_grant")?;
      rejections += 1;
    }
  }
  ensure(
    successes == 1,
    format!(
      "exactly one racer must rotate (got {successes}; invalid_grant={rejections}, \
       unavailable={unavailable})"
    ),
  )?;
  ensure(
    rejections + unavailable == 7,
    "every other racer must be rejected",
  )?;
  Ok(())
}

/// A public client's refresh grant without a fresh DPoP proof is
/// `invalid_grant` (the stored `jkt` alone never mints).
#[tokio::test]
async fn e2e_public_client_without_dpop_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let minted = world
    .mint(
      PUBLIC_ID,
      "read",
      ClientKind::Public,
      Some("e2e-public-jkt"),
    )
    .await?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "refresh_token"),
        ("refresh_token", minted.refresh_token.as_str()),
        ("client_id", PUBLIC_ID),
      ],
      None,
      &[],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;
  Ok(())
}

/// A DPoP-bound confidential client must present a fresh proof at token time.
#[tokio::test]
async fn e2e_dpop_bound_client_requires_fresh_proof() -> Result<(), TestError> {
  const BOUND_ID: &str = "e2e-grant-dpop-bound";
  const BOUND_SECRET: &str = "e2e-grant-bound-secret-0f1e2d3c4b5a6978";
  let world = World::start(open_rate_limit()).await?;
  seed_client_bound(
    &world.pool,
    BOUND_ID,
    Some(BOUND_SECRET),
    &["client_credentials"],
    "read",
    TokenEndpointAuthMethod::ClientSecretBasic,
    true,
  )
  .await?;
  seed_scope(&world.pool, "read").await?;

  let (status, _, body) = world
    .post_form(
      "/token",
      &[("grant_type", "client_credentials")],
      Some((BOUND_ID, BOUND_SECRET)),
      &[],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;

  let key = DpopKey::generate()?;
  let proof = key.proof("POST", &format!("{}/token", world.state.config.issuer))?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[("grant_type", "client_credentials"), ("scope", "read")],
      Some((BOUND_ID, BOUND_SECRET)),
      &[("dpop", proof.as_str())],
    )
    .await?;
  ensure(
    status == reqwest::StatusCode::OK,
    format!("fresh proof must mint: {status} {body}"),
  )?;
  ensure(
    json_body(&body)?["token_type"] == "DPoP",
    "the bound issuance must be a DPoP token",
  )?;
  Ok(())
}

/// A DPoP-bound confidential client must present a fresh proof on the
/// authorization-code grant too (not only the grants the dispatcher
/// authenticates itself); a proof-less redemption is `invalid_grant`.
#[tokio::test]
async fn e2e_dpop_bound_auth_code_requires_fresh_proof() -> Result<(), TestError> {
  const BOUND_ID: &str = "e2e-grant-bound-code";
  const BOUND_SECRET: &str = "e2e-grant-bound-code-secret-4d3c2b1a";
  let world = World::start(open_rate_limit()).await?;
  seed_client_bound(
    &world.pool,
    BOUND_ID,
    Some(BOUND_SECRET),
    &["authorization_code"],
    "read",
    TokenEndpointAuthMethod::ClientSecretBasic,
    true,
  )
  .await?;
  seed_scope(&world.pool, "read").await?;
  attach_redirect(&world.pool, BOUND_ID, REDIRECT_URI).await?;

  let (challenge, verifier) = oauth2_pkce();
  let code = issue_conf_code(&world, BOUND_ID, &challenge).await?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "authorization_code"),
        ("code", code.code.as_str()),
        ("redirect_uri", REDIRECT_URI),
        ("client_id", BOUND_ID),
        ("code_verifier", verifier.secret()),
      ],
      Some((BOUND_ID, BOUND_SECRET)),
      &[],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;

  let code = issue_conf_code(&world, BOUND_ID, &challenge).await?;
  let key = DpopKey::generate()?;
  let proof = key.proof("POST", &format!("{}/token", world.state.config.issuer))?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "authorization_code"),
        ("code", code.code.as_str()),
        ("redirect_uri", REDIRECT_URI),
        ("client_id", BOUND_ID),
        ("code_verifier", verifier.secret()),
      ],
      Some((BOUND_ID, BOUND_SECRET)),
      &[("dpop", proof.as_str())],
    )
    .await?;
  ensure(
    status == reqwest::StatusCode::OK,
    format!("fresh proof must mint: {status} {body}"),
  )?;
  ensure(
    json_body(&body)?["token_type"] == "DPoP",
    "the bound redemption must be a DPoP token",
  )?;
  Ok(())
}

/// Baseline client-credentials flow via the `oauth2` crate issues a token.
#[tokio::test]
async fn e2e_grant_client_credentials_oauth2_issues_token() -> Result<(), TestError> {
  let world = setup().await?;
  let client = clients::oauth2_client(&world.base, CLIENT_ID, Some(CLIENT_SECRET))?;
  let token = client
    .exchange_client_credentials()
    .request_async(&world.client)
    .await
    .map_err(|error| fail(format!("client-credentials failed: {error}")))?;
  ensure(
    !token.access_token().secret().is_empty(),
    "client-credentials must return an access token",
  )?;
  Ok(())
}

/// Baseline authorization-code + PKCE exchange via the `oauth2` crate
/// redeems a real code issued through [`CodeIssuer`].
#[tokio::test]
async fn e2e_grant_authorization_code_oauth2_issues_token() -> Result<(), TestError> {
  let world = setup().await?;
  let (challenge, verifier) = oauth2_pkce();
  let issued = {
    let issuer = CodeIssuer::new(&world.state.config.ttl, &world.state.keys)
      .map_err(|error| fail(format!("issuer: {error}")))?;
    let approved = ScopeSet::parse("read").map_err(|error| fail(format!("scope: {error}")))?;
    let entitled =
      ScopeSet::parse("read write").map_err(|error| fail(format!("scope: {error}")))?;
    let mut conn = world.state.redis.clone();
    let request = CodeIssueRequest {
      client_id: CLIENT_ID,
      client_kind: CodeClientKind::Confidential,
      user_id: "e2e-subject",
      redirect_uri: REDIRECT_URI,
      approved_scope: &approved,
      user_entitled: &entitled,
      code_challenge: &challenge,
      dpop_jkt: None,
      state: None,
      issuer: &world.state.config.issuer,
    };
    issuer
      .issue(&mut conn, &world.store, &request)
      .await
      .map_err(|error| fail(format!("code issue failed: {error}")))?
  };
  let client = clients::oauth2_client(&world.base, CLIENT_ID, Some(CLIENT_SECRET))?;
  let token = client
    .exchange_code(oauth2::AuthorizationCode::new(issued.code))
    .set_pkce_verifier(verifier)
    .request_async(&world.client)
    .await
    .map_err(|error| fail(format!("code redemption failed: {error}")))?;
  ensure(
    !token.access_token().secret().is_empty(),
    "code redemption must return an access token",
  )?;
  ensure(
    token.refresh_token().is_some(),
    "code redemption must return a refresh token",
  )?;
  Ok(())
}

/// A stale authorization code via the `oauth2` crate is `invalid_grant`.
#[tokio::test]
async fn e2e_grant_authorization_code_stale_is_invalid_grant() -> Result<(), TestError> {
  let world = setup().await?;
  let client = clients::oauth2_client(&world.base, CLIENT_ID, Some(CLIENT_SECRET))?;
  let (_challenge, verifier) = oauth2_pkce();
  let outcome = client
    .exchange_code(oauth2::AuthorizationCode::new("stale-code".to_owned()))
    .set_pkce_verifier(verifier)
    .request_async(&world.client)
    .await;
  match outcome {
    Err(oauth2::RequestTokenError::ServerResponse(response)) => ensure(
      response.error() == &oauth2::basic::BasicErrorResponseType::InvalidGrant,
      "stale code must be invalid_grant",
    ),
    _ => Err(fail("stale code must be an invalid_grant server response")),
  }
}

/// An unknown `grant_type` — including the OAuth 2.0-only `password` — is
/// rejected as `unsupported_grant_type` without minting.
#[tokio::test]
async fn e2e_unknown_grant_type_rejected() -> Result<(), TestError> {
  let world = setup().await?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "password"),
        ("username", "u"),
        ("password", "p"),
      ],
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[],
    )
    .await?;
  ensure_error(status, &body, "unsupported_grant_type")?;
  Ok(())
}

/// Device polling of an unknown code is `expired_token`; a disabled token
/// exchange is `invalid_grant`.
#[tokio::test]
async fn e2e_grant_device_code_and_token_exchange_fail_closed() -> Result<(), TestError> {
  let world = setup().await?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        ("grant_type", "urn:ietf:params:oauth:grant-type:device_code"),
        ("device_code", "pending-device-code"),
      ],
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[],
    )
    .await?;
  ensure_error(status, &body, "expired_token")?;
  let (status, _, body) = world
    .post_form(
      "/token",
      &[
        (
          "grant_type",
          "urn:ietf:params:oauth:grant-type:token-exchange",
        ),
        ("subject_token", "opaque-subject"),
      ],
      Some((CLIENT_ID, CLIENT_SECRET)),
      &[],
    )
    .await?;
  ensure_error(status, &body, "invalid_grant")?;
  Ok(())
}

/// The authorize endpoint verifies a presented DPoP proof and stashes its
/// `jkt` in the pending-auth record the code issuance binds.
#[tokio::test]
async fn e2e_authorize_captures_dpop_jkt() -> Result<(), TestError> {
  let world = setup().await?;
  let (challenge, _verifier) = oauth2_pkce();
  let key = DpopKey::generate()?;
  let htu = format!("{}/authorize", world.state.config.issuer);
  let proof = key.proof("GET", &htu)?;
  let (status, headers, body) = world
    .get(
      &format!(
        "/authorize?client_id={PUBLIC_ID}&redirect_uri={}&response_type=code&scope=read\
         &code_challenge={challenge}&code_challenge_method=S256",
        encoded(REDIRECT_URI)
      ),
      &[("dpop", proof.as_str())],
    )
    .await?;
  ensure(
    status == reqwest::StatusCode::SEE_OTHER,
    format!("authorize with DPoP must 303: {status} {body}"),
  )?;
  let location = location_of(&headers)?;
  let request_id = location
    .split("request_id=")
    .nth(1)
    .ok_or_else(|| fail("authorize redirect must carry request_id"))?;
  let mut conn = world.state.redis.clone();
  let record = d_oauth::store::pending::get(&mut conn, &world.store, request_id)
    .await
    .map_err(|error| fail(format!("pending read failed: {error}")))?
    .ok_or_else(|| fail("pending record must exist"))?;
  let expected =
    d_oauth::jose::jwk::thumbprint(&key.jwk()).map_err(|error| fail(format!("jwk: {error}")))?;
  ensure(
    record.client_id == PUBLIC_ID,
    "pending record must bind the client",
  )?;
  ensure(
    record.dpop_jkt.as_deref() == Some(expected.as_str()),
    "pending record must carry the verified DPoP thumbprint",
  )?;
  Ok(())
}

/// PKCE pair from the `oauth2` crate (baseline-flow material only).
fn oauth2_pkce() -> (String, oauth2::PkceCodeVerifier) {
  let (challenge, verifier) = oauth2::PkceCodeChallenge::new_random_sha256();
  (challenge.as_str().to_owned(), verifier)
}

/// Issue a fresh confidential authorization code with no DPoP binding.
async fn issue_conf_code(
  world: &World,
  client_id: &str,
  challenge: &str,
) -> Result<IssuedCode, TestError> {
  let issuer = CodeIssuer::new(&world.state.config.ttl, &world.state.keys)
    .map_err(|error| fail(format!("issuer: {error}")))?;
  let approved = ScopeSet::parse("read").map_err(|error| fail(format!("scope: {error}")))?;
  let mut conn = world.state.redis.clone();
  let request = CodeIssueRequest {
    client_id,
    client_kind: CodeClientKind::Confidential,
    user_id: "e2e-subject",
    redirect_uri: REDIRECT_URI,
    approved_scope: &approved,
    user_entitled: &approved,
    code_challenge: challenge,
    dpop_jkt: None,
    state: None,
    issuer: &world.state.config.issuer,
  };
  issuer
    .issue(&mut conn, &world.store, &request)
    .await
    .map_err(|error| fail(format!("code issue failed: {error}")))
}

/// Percent-encode a value for query embedding.
fn encoded(value: &str) -> String {
  let mut out = String::with_capacity(value.len());
  for byte in value.bytes() {
    if byte.is_ascii_alphanumeric() || b"-_.~".contains(&byte) {
      out.push(byte as char);
    } else {
      out.push_str(&format!("%{byte:02X}"));
    }
  }
  out
}

/// Read the `location` header or fail the test.
fn location_of(headers: &reqwest::header::HeaderMap) -> Result<String, TestError> {
  headers
    .get("location")
    .and_then(|value| value.to_str().ok())
    .map(str::to_owned)
    .ok_or_else(|| fail("response lacks location header"))
}