feat(admin): admin session JWTs + admin_sessions queries [operator §0.3]

Admin tokens are cryptographically distinct from user tokens: a dedicated
ADMIN_JWT_SECRET, a distinct audience (smirk-admin) plus an explicit scope, and
the centralized strict Validation (HS256 pinned, zero leeway, aud required) —
Validation::default() is never used on this path. Access TTL 15 min (carries a
jti recorded in the session row, so a soft-revoked admin's still-valid token is
rejected at the next call), refresh TTL 8 h (binds a session id).

- core::admin_session: AdminSessionManager (mint/verify access+refresh) with the
  four required regressions + scope check: user token fails admin decode;
  wrong/absent aud fails; HS512 (alg confusion) fails; expired fails at zero
  leeway; non-admin scope fails.
- core::session::strict_validation made pub(crate) and shared (no drift).
- db::admin_sessions: create, find-active-by-jti (guard), find-active-by-id +
  rotate-jti (refresh), revoke (logout), revoke-all-for-key (key cascade), and a
  dead-session sweep. Lookups return only live (unrevoked, unexpired) rows.
- NewAdminSession model; 2 L1 tests (lookup/rotate/logout, key->session cascade).

src/core/admin_session.rs

@@ -0,0 +1,286 @@
+//! Admin session JWTs — cryptographically distinct from user sessions.
+//!
+//! Admin tokens are signed with a dedicated `ADMIN_JWT_SECRET` and carry a
+//! distinct audience (`smirk-admin`) plus an explicit `scope`, so a user token
+//! can never be presented on the admin plane and vice versa. Verification reuses
+//! the centralized strict [`crate::core::session::strict_validation`] (HS256
+//! pinned, zero leeway, `aud` required) — `Validation::default()` is never used.
+//! Access tokens are short-lived (15 min) and carry a `jti` recorded in the
+//! `admin_sessions` row, so a soft-revoked admin's still-valid token is rejected
+//! at the next call; refresh tokens (8 h) bind a session id.
+
+use chrono::{Duration, Utc};
+use jsonwebtoken::{decode, encode, Algorithm, DecodingKey, EncodingKey, Header};
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+
+use crate::core::session::strict_validation;
+use crate::error::AppError;
+
+const ADMIN_ACCESS_AUD: &str = "smirk-admin";
+const ADMIN_REFRESH_AUD: &str = "smirk-admin-refresh";
+const ADMIN_SCOPE: &str = "admin";
+const ACCESS_TTL_MINUTES: i64 = 15;
+const REFRESH_TTL_HOURS: i64 = 8;
+
+/// Admin access-token claims. `sub` is the admin **pubkey** (not a UUID) so the
+/// live allowlist re-check in the guard is meaningful.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AdminAccessClaims {
+    pub sub: String,
+    pub aud: String,
+    pub scope: String,
+    pub jti: String,
+    pub iat: i64,
+    pub exp: i64,
+}
+
+/// Admin refresh-token claims. `sid` is the `admin_sessions` row id.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AdminRefreshClaims {
+    pub sub: String,
+    pub aud: String,
+    pub sid: String,
+    pub iat: i64,
+    pub exp: i64,
+}
+
+/// Decoded admin access token: the pubkey to re-authorize and the `jti` to look
+/// up the live session row.
+#[derive(Debug, Clone)]
+pub struct AdminAccessInfo {
+    pub pubkey: String,
+    pub jti: String,
+}
+
+/// A freshly minted admin token pair. `access_jti` must be recorded in the
+/// session row so the guard can match (and revocation can invalidate) it.
+#[derive(Debug, Clone)]
+pub struct AdminTokenPair {
+    pub access_token: String,
+    pub refresh_token: String,
+    pub access_jti: String,
+    pub expires_in: i64,
+}
+
+/// Mints and verifies admin JWTs under a dedicated secret.
+#[derive(Clone)]
+pub struct AdminSessionManager {
+    encoding_key: EncodingKey,
+    decoding_key: DecodingKey,
+    access_validation: jsonwebtoken::Validation,
+    refresh_validation: jsonwebtoken::Validation,
+}
+
+impl AdminSessionManager {
+    /// `admin_jwt_secret` must be >= 32 bytes (enforced by config validation when
+    /// the admin surface is enabled).
+    pub fn new(admin_jwt_secret: &str) -> Self {
+        Self {
+            encoding_key: EncodingKey::from_secret(admin_jwt_secret.as_bytes()),
+            decoding_key: DecodingKey::from_secret(admin_jwt_secret.as_bytes()),
+            access_validation: strict_validation(ADMIN_ACCESS_AUD),
+            refresh_validation: strict_validation(ADMIN_REFRESH_AUD),
+        }
+    }
+
+    /// Mint an access + refresh pair for `admin_pubkey`, binding the refresh
+    /// token to `session_id`. Returns the pair plus the access `jti` to persist.
+    pub fn create_token_pair(
+        &self,
+        admin_pubkey: &str,
+        session_id: Uuid,
+    ) -> Result<AdminTokenPair, AppError> {
+        let now = Utc::now();
+        let jti = Uuid::new_v4().to_string();
+        let header = Header::new(Algorithm::HS256);
+
+        let access = AdminAccessClaims {
+            sub: admin_pubkey.to_string(),
+            aud: ADMIN_ACCESS_AUD.to_string(),
+            scope: ADMIN_SCOPE.to_string(),
+            jti: jti.clone(),
+            iat: now.timestamp(),
+            exp: (now + Duration::minutes(ACCESS_TTL_MINUTES)).timestamp(),
+        };
+        let access_token = encode(&header, &access, &self.encoding_key)
+            .map_err(|e| AppError::Internal(format!("admin access token: {e}")))?;
+
+        let refresh = AdminRefreshClaims {
+            sub: admin_pubkey.to_string(),
+            aud: ADMIN_REFRESH_AUD.to_string(),
+            sid: session_id.to_string(),
+            iat: now.timestamp(),
+            exp: (now + Duration::hours(REFRESH_TTL_HOURS)).timestamp(),
+        };
+        let refresh_token = encode(&header, &refresh, &self.encoding_key)
+            .map_err(|e| AppError::Internal(format!("admin refresh token: {e}")))?;
+
+        Ok(AdminTokenPair {
+            access_token,
+            refresh_token,
+            access_jti: jti,
+            expires_in: ACCESS_TTL_MINUTES * 60,
+        })
+    }
+
+    /// Verify an admin access token. Beyond the strict `aud` check, the `scope`
+    /// is re-asserted. The error is a literal (never the inner Display) so the
+    /// token cannot become an oracle.
+    pub fn verify_access(&self, token: &str) -> Result<AdminAccessInfo, AppError> {
+        let data = decode::<AdminAccessClaims>(token, &self.decoding_key, &self.access_validation)
+            .map_err(|_| AppError::AuthError("Invalid or expired admin token".into()))?;
+        if data.claims.scope != ADMIN_SCOPE {
+            return Err(AppError::AuthError("Invalid or expired admin token".into()));
+        }
+        Ok(AdminAccessInfo {
+            pubkey: data.claims.sub,
+            jti: data.claims.jti,
+        })
+    }
+
+    /// Verify an admin refresh token, returning `(admin_pubkey, session_id)`.
+    pub fn verify_refresh(&self, token: &str) -> Result<(String, Uuid), AppError> {
+        let data =
+            decode::<AdminRefreshClaims>(token, &self.decoding_key, &self.refresh_validation)
+                .map_err(|_| AppError::AuthError("Invalid or expired admin token".into()))?;
+        let sid = Uuid::parse_str(&data.claims.sid)
+            .map_err(|_| AppError::AuthError("Invalid or expired admin token".into()))?;
+        Ok((data.claims.sub, sid))
+    }
+
+    pub fn access_ttl_secs(&self) -> i64 {
+        ACCESS_TTL_MINUTES * 60
+    }
+
+    pub fn refresh_ttl(&self) -> Duration {
+        Duration::hours(REFRESH_TTL_HOURS)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::core::session::{Platform, SessionManager};
+
+    const ADMIN_SECRET: &str = "admin-jwt-secret-at-least-32-bytes-long!!";
+    const PK: &str = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+
+    #[test]
+    fn mint_and_verify_roundtrip() {
+        let m = AdminSessionManager::new(ADMIN_SECRET);
+        let sid = Uuid::new_v4();
+        let pair = m.create_token_pair(PK, sid).unwrap();
+
+        let info = m.verify_access(&pair.access_token).unwrap();
+        assert_eq!(info.pubkey, PK);
+        assert_eq!(info.jti, pair.access_jti);
+
+        let (pk, got_sid) = m.verify_refresh(&pair.refresh_token).unwrap();
+        assert_eq!(pk, PK);
+        assert_eq!(got_sid, sid);
+    }
+
+    #[test]
+    fn user_access_token_fails_admin_decode() {
+        // A user token (distinct secret + audience) must not verify as admin.
+        let user = SessionManager::new("user-jwt-secret-at-least-32-bytes-long!", 24);
+        let pair = user
+            .create_token_pair(Uuid::new_v4(), Platform::Web, Uuid::new_v4())
+            .unwrap();
+        let admin = AdminSessionManager::new(ADMIN_SECRET);
+        assert!(admin.verify_access(&pair.access_token).is_err());
+    }
+
+    #[test]
+    fn admin_access_not_accepted_as_refresh() {
+        let m = AdminSessionManager::new(ADMIN_SECRET);
+        let pair = m.create_token_pair(PK, Uuid::new_v4()).unwrap();
+        // Distinct audiences within the admin secret too.
+        assert!(m.verify_refresh(&pair.access_token).is_err());
+        assert!(m.verify_access(&pair.refresh_token).is_err());
+    }
+
+    #[test]
+    fn wrong_audience_fails() {
+        // A token with the right secret/alg but a foreign audience must fail.
+        let claims = AdminAccessClaims {
+            sub: PK.into(),
+            aud: "some-other-aud".into(),
+            scope: ADMIN_SCOPE.into(),
+            jti: Uuid::new_v4().to_string(),
+            iat: Utc::now().timestamp(),
+            exp: (Utc::now() + Duration::minutes(5)).timestamp(),
+        };
+        let token = encode(
+            &Header::new(Algorithm::HS256),
+            &claims,
+            &EncodingKey::from_secret(ADMIN_SECRET.as_bytes()),
+        )
+        .unwrap();
+        let m = AdminSessionManager::new(ADMIN_SECRET);
+        assert!(m.verify_access(&token).is_err());
+    }
+
+    #[test]
+    fn wrong_algorithm_fails() {
+        // HS512 token must be rejected (HS256 pinned, no alg confusion).
+        let claims = AdminAccessClaims {
+            sub: PK.into(),
+            aud: ADMIN_ACCESS_AUD.into(),
+            scope: ADMIN_SCOPE.into(),
+            jti: Uuid::new_v4().to_string(),
+            iat: Utc::now().timestamp(),
+            exp: (Utc::now() + Duration::minutes(5)).timestamp(),
+        };
+        let token = encode(
+            &Header::new(Algorithm::HS512),
+            &claims,
+            &EncodingKey::from_secret(ADMIN_SECRET.as_bytes()),
+        )
+        .unwrap();
+        let m = AdminSessionManager::new(ADMIN_SECRET);
+        assert!(m.verify_access(&token).is_err());
+    }
+
+    #[test]
+    fn expired_token_fails_with_zero_leeway() {
+        let claims = AdminAccessClaims {
+            sub: PK.into(),
+            aud: ADMIN_ACCESS_AUD.into(),
+            scope: ADMIN_SCOPE.into(),
+            jti: Uuid::new_v4().to_string(),
+            iat: (Utc::now() - Duration::hours(1)).timestamp(),
+            exp: (Utc::now() - Duration::minutes(1)).timestamp(),
+        };
+        let token = encode(
+            &Header::new(Algorithm::HS256),
+            &claims,
+            &EncodingKey::from_secret(ADMIN_SECRET.as_bytes()),
+        )
+        .unwrap();
+        let m = AdminSessionManager::new(ADMIN_SECRET);
+        assert!(m.verify_access(&token).is_err());
+    }
+
+    #[test]
+    fn scope_must_be_admin() {
+        // Right aud/alg/secret but a non-admin scope is rejected.
+        let claims = AdminAccessClaims {
+            sub: PK.into(),
+            aud: ADMIN_ACCESS_AUD.into(),
+            scope: "user".into(),
+            jti: Uuid::new_v4().to_string(),
+            iat: Utc::now().timestamp(),
+            exp: (Utc::now() + Duration::minutes(5)).timestamp(),
+        };
+        let token = encode(
+            &Header::new(Algorithm::HS256),
+            &claims,
+            &EncodingKey::from_secret(ADMIN_SECRET.as_bytes()),
+        )
+        .unwrap();
+        let m = AdminSessionManager::new(ADMIN_SECRET);
+        assert!(m.verify_access(&token).is_err());
+    }
+}

src/core/mod.rs

@@ -3,6 +3,7 @@
 //! Functions take their inputs (config, decoded bytes) as parameters, keeping
 //! this layer straightforward to test in isolation.
 
+pub mod admin_session;
 pub mod crypto;
 pub mod pow;
 pub mod secret;

src/core/session.rs

@@ -148,7 +148,10 @@ pub struct SessionManager {
     refresh_token_expiry_days: i64,
 }
 
-fn strict_validation(audience: &str) -> Validation {
+/// Centralized strict JWT validation: HS256 pinned (no alg-confusion), zero
+/// leeway, `exp`/`sub`/`aud` required, and the audience fixed. Shared by the user
+/// and admin session managers so neither can drift to `Validation::default()`.
+pub(crate) fn strict_validation(audience: &str) -> Validation {
     let mut v = Validation::new(Algorithm::HS256);
     v.leeway = 0;
     v.validate_exp = true;

src/infra/db/admin_sessions.rs

@@ -0,0 +1,136 @@
+//! Admin session queries.
+//!
+//! Admin sessions live in their own table (never user `sessions`). The guard
+//! looks a session up by the access token's `jti`; refresh and logout act by
+//! session id; revoking a key cascades to every session it owns. A lookup only
+//! returns a session that is neither revoked nor expired.
+
+use tracing::instrument;
+use uuid::Uuid;
+
+use crate::error::AppError;
+use crate::models::db::{AdminSession, NewAdminSession};
+
+use super::Database;
+
+const COLS: &str = "id, admin_key_id, pubkey, refresh_token_hash, access_jti, \
+     device_info, ip_address, created_at, expires_at, revoked_at";
+
+impl Database {
+    /// Persist a new admin session.
+    #[instrument(skip(self, input), fields(admin_key_id = %input.admin_key_id))]
+    pub async fn create_admin_session(
+        &self,
+        input: NewAdminSession,
+    ) -> Result<AdminSession, AppError> {
+        let sql = format!(
+            "INSERT INTO admin_sessions \
+             (id, admin_key_id, pubkey, refresh_token_hash, access_jti, device_info, ip_address, expires_at) \
+             VALUES ($1, $2, $3, $4, $5, $6, $7, $8) RETURNING {COLS}"
+        );
+        let s = sqlx::query_as::<_, AdminSession>(&sql)
+            .bind(input.id)
+            .bind(input.admin_key_id)
+            .bind(&input.pubkey)
+            .bind(&input.refresh_token_hash)
+            .bind(&input.access_jti)
+            .bind(&input.device_info)
+            .bind(input.ip_address)
+            .bind(input.expires_at)
+            .fetch_one(self.pool())
+            .await?;
+        Ok(s)
+    }
+
+    /// The live session whose access token carries `jti` (not revoked/expired).
+    #[instrument(skip(self, jti))]
+    pub async fn find_active_admin_session_by_jti(
+        &self,
+        jti: &str,
+    ) -> Result<Option<AdminSession>, AppError> {
+        let sql = format!(
+            "SELECT {COLS} FROM admin_sessions \
+             WHERE access_jti = $1 AND revoked_at IS NULL AND expires_at > NOW()"
+        );
+        let s = sqlx::query_as::<_, AdminSession>(&sql)
+            .bind(jti)
+            .fetch_optional(self.pool())
+            .await?;
+        Ok(s)
+    }
+
+    /// The live session with this id (used by the refresh path).
+    #[instrument(skip(self))]
+    pub async fn find_active_admin_session_by_id(
+        &self,
+        id: Uuid,
+    ) -> Result<Option<AdminSession>, AppError> {
+        let sql = format!(
+            "SELECT {COLS} FROM admin_sessions \
+             WHERE id = $1 AND revoked_at IS NULL AND expires_at > NOW()"
+        );
+        let s = sqlx::query_as::<_, AdminSession>(&sql)
+            .bind(id)
+            .fetch_optional(self.pool())
+            .await?;
+        Ok(s)
+    }
+
+    /// Rotate the access `jti` on refresh (the old access token stops matching).
+    /// Returns the updated row, or `None` if the session is no longer live.
+    #[instrument(skip(self, new_jti))]
+    pub async fn rotate_admin_session_jti(
+        &self,
+        id: Uuid,
+        new_jti: &str,
+    ) -> Result<Option<AdminSession>, AppError> {
+        let sql = format!(
+            "UPDATE admin_sessions SET access_jti = $2 \
+             WHERE id = $1 AND revoked_at IS NULL AND expires_at > NOW() RETURNING {COLS}"
+        );
+        let s = sqlx::query_as::<_, AdminSession>(&sql)
+            .bind(id)
+            .bind(new_jti)
+            .fetch_optional(self.pool())
+            .await?;
+        Ok(s)
+    }
+
+    /// Revoke a single session (logout). Returns true if a live row was revoked.
+    #[instrument(skip(self))]
+    pub async fn revoke_admin_session(&self, id: Uuid) -> Result<bool, AppError> {
+        let res = sqlx::query(
+            "UPDATE admin_sessions SET revoked_at = NOW() \
+             WHERE id = $1 AND revoked_at IS NULL",
+        )
+        .bind(id)
+        .execute(self.pool())
+        .await?;
+        Ok(res.rows_affected() > 0)
+    }
+
+    /// Revoke every live session owned by an admin key (key-revocation cascade).
+    /// Returns the number revoked.
+    #[instrument(skip(self))]
+    pub async fn revoke_admin_sessions_for_key(&self, admin_key_id: Uuid) -> Result<u64, AppError> {
+        let res = sqlx::query(
+            "UPDATE admin_sessions SET revoked_at = NOW() \
+             WHERE admin_key_id = $1 AND revoked_at IS NULL",
+        )
+        .bind(admin_key_id)
+        .execute(self.pool())
+        .await?;
+        Ok(res.rows_affected())
+    }
+
+    /// Delete expired/revoked admin sessions older than now (hygiene sweep).
+    #[instrument(skip(self))]
+    pub async fn delete_dead_admin_sessions(&self) -> Result<u64, AppError> {
+        let res = sqlx::query(
+            "DELETE FROM admin_sessions WHERE expires_at <= NOW() OR revoked_at IS NOT NULL",
+        )
+        .execute(self.pool())
+        .await?;
+        Ok(res.rows_affected())
+    }
+}

src/infra/db/mod.rs

@@ -7,6 +7,7 @@
 //! reaches a column and the peppering cannot drift between call sites.
 
 mod admin_keys;
+mod admin_sessions;
 mod audit;
 mod challenges;
 mod grin_slatepacks;

src/models/db.rs

@@ -280,6 +280,20 @@ pub struct NewAdminKey {
     pub activation_deadline: Option<DateTime<Utc>>,
 }
 
+/// Input for an admin session row. The id and access_jti are generated by the
+/// caller (the refresh token embeds the id, the access token embeds the jti).
+#[derive(Debug, Clone)]
+pub struct NewAdminSession {
+    pub id: Uuid,
+    pub admin_key_id: Uuid,
+    pub pubkey: String,
+    pub refresh_token_hash: String,
+    pub access_jti: String,
+    pub device_info: Option<String>,
+    pub ip_address: Option<IpNetwork>,
+    pub expires_at: DateTime<Utc>,
+}
+
 #[derive(Debug, Clone)]
 pub struct NewAuditLog {
     pub user_id: Option<Uuid>,