fraiseql-auth 2.6.0

//! HTTP handlers for the built-in authentication endpoints (`/auth/start`,
//! `/auth/callback`, `/auth/refresh`, `/auth/logout`).
use std::{fmt, net::SocketAddr, sync::Arc};

use axum::{
    Json,
    extract::{ConnectInfo, Query, State},
    http::StatusCode,
    response::IntoResponse,
};
use serde::{Deserialize, Serialize};

use crate::{
    audit::logger::{AuditEventType, SecretType, get_audit_logger},
    error::{AuthError, Result},
    provider::OAuthProvider,
    rate_limiting::RateLimiters,
    session::SessionStore,
    state_store::StateStore,
};

/// AuthState holds the auth configuration and backends
#[derive(Clone)]
pub struct AuthState {
    /// OAuth provider
    pub oauth_provider: Arc<dyn OAuthProvider>,
    /// Session store backend
    pub session_store:  Arc<dyn SessionStore>,
    /// CSRF state store backend (in-memory for single-instance, Redis for distributed)
    pub state_store:    Arc<dyn StateStore>,
    /// Rate limiters for auth endpoints (per-IP based)
    pub rate_limiters:  Arc<RateLimiters>,
}

/// Request body for auth/start endpoint
#[derive(Debug, Deserialize)]
pub struct AuthStartRequest {
    /// Optional provider name (for multi-provider setups)
    pub provider: Option<String>,
}

/// Response body for the `POST /auth/start` endpoint.
#[derive(Debug, Serialize)]
pub struct AuthStartResponse {
    /// Authorization URL to redirect user to
    pub authorization_url: String,
}

/// Query parameters for auth/callback endpoint
#[derive(Debug, Deserialize)]
pub struct AuthCallbackQuery {
    /// Authorization code from provider
    pub code:              String,
    /// State parameter for CSRF protection
    pub state:             String,
    /// Error from provider if present
    pub error:             Option<String>,
    /// Error description from provider
    pub error_description: Option<String>,
}

/// Response body for the `GET /auth/callback` endpoint.
///
/// Returned after a successful OAuth authorization-code exchange.
/// In a production browser-facing flow, the server would instead redirect
/// the user agent to the frontend application with tokens in a URL fragment;
/// this JSON form is suitable for API clients and testing.
///
/// # Debug redaction
///
/// `Debug` is implemented manually so the `access_token` and `refresh_token`
/// fields are never written to logs. Calling `{:?}` yields placeholders
/// (`"<redacted>"` / `Some("<redacted>")` / `None`) for both fields.
#[derive(Serialize)]
#[non_exhaustive]
#[doc(hidden)] // Internal-pub: HTTP response body for /auth/callback; serialized to JSON for clients. Adopters consume the JSON wire format, not the Rust type.
pub struct AuthCallbackResponse {
    /// Access token for API requests
    pub access_token:  String,
    /// Optional refresh token
    pub refresh_token: Option<String>,
    /// Token type (usually "Bearer")
    pub token_type:    String,
    /// Time in seconds until token expires
    pub expires_in:    u64,
}

impl fmt::Debug for AuthCallbackResponse {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // SECURITY: never write the raw access_token/refresh_token to Debug
        // output — they would otherwise leak into structured logs via any
        // `debug!(?resp)` call. See IMPROVEMENTS.md F045.
        f.debug_struct("AuthCallbackResponse")
            .field("access_token", &"<redacted>")
            .field("refresh_token", &self.refresh_token.as_ref().map(|_| "<redacted>"))
            .field("token_type", &self.token_type)
            .field("expires_in", &self.expires_in)
            .finish()
    }
}

impl AuthCallbackResponse {
    /// Creates a new `AuthCallbackResponse`.
    #[must_use]
    pub const fn new(
        access_token: String,
        refresh_token: Option<String>,
        token_type: String,
        expires_in: u64,
    ) -> Self {
        Self {
            access_token,
            refresh_token,
            token_type,
            expires_in,
        }
    }
}

/// Request body for auth/refresh endpoint
#[derive(Debug, Deserialize)]
pub struct AuthRefreshRequest {
    /// Refresh token to exchange for new access token
    pub refresh_token: String,
}

/// Response body for the `POST /auth/refresh` endpoint.
///
/// # Debug redaction
///
/// `Debug` is implemented manually so the `access_token` field is never
/// written to logs. Calling `{:?}` yields `"<redacted>"` for the token value.
#[derive(Serialize)]
pub struct AuthRefreshResponse {
    /// New access token
    pub access_token: String,
    /// Token type
    pub token_type:   String,
    /// Time in seconds until token expires
    pub expires_in:   u64,
}

impl fmt::Debug for AuthRefreshResponse {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // SECURITY: never write the raw access_token to Debug output. See
        // IMPROVEMENTS.md F045.
        f.debug_struct("AuthRefreshResponse")
            .field("access_token", &"<redacted>")
            .field("token_type", &self.token_type)
            .field("expires_in", &self.expires_in)
            .finish()
    }
}

/// Request body for auth/logout endpoint
#[derive(Debug, Deserialize)]
pub struct AuthLogoutRequest {
    /// Refresh token to revoke
    pub refresh_token: Option<String>,
}

/// POST /auth/start - Initiate OAuth flow
///
/// Returns an authorization URL that the client should redirect the user to.
///
/// # Rate Limiting
///
/// This endpoint is rate-limited per IP address to prevent brute-force attacks.
/// The limit is configurable via FRAISEQL_AUTH_START_MAX_REQUESTS and
/// FRAISEQL_AUTH_START_WINDOW_SECS environment variables.
///
/// # Errors
///
/// Returns `AuthError::RateLimited` if the per-IP rate limit is exceeded.
/// Returns `AuthError::SystemTimeError` if the system clock is unavailable.
/// Returns `AuthError` if the state store write fails.
pub async fn auth_start(
    State(state): State<AuthState>,
    ConnectInfo(addr): ConnectInfo<SocketAddr>,
    Json(req): Json<AuthStartRequest>,
) -> Result<Json<AuthStartResponse>> {
    // SECURITY: Check rate limiting for auth/start endpoint (per IP)
    let client_ip = addr.ip().to_string();
    if state.rate_limiters.auth_start.check(&client_ip).is_err() {
        return Err(AuthError::RateLimited {
            retry_after_secs: state.rate_limiters.auth_start.clone_config().window_secs,
        });
    }

    // Generate random state for CSRF protection using cryptographically secure RNG
    let state_value = generate_secure_state();

    // Get current time with explicit error handling (not unwrap_or_default)
    let now = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map_err(|_| AuthError::SystemTimeError {
            message: "Failed to get current system time".to_string(),
        })?
        .as_secs();

    // Store state with expiry (10 minutes)
    let expiry = now + 600;

    // SECURITY: Store state using configurable backend (in-memory or distributed)
    let provider = req.provider.unwrap_or_else(|| "default".to_string());
    state.state_store.store(state_value.clone(), provider, expiry).await?;

    // Generate authorization URL
    let authorization_url = state.oauth_provider.authorization_url(&state_value);

    Ok(Json(AuthStartResponse { authorization_url }))
}

/// GET /auth/callback - OAuth provider redirects here
///
/// Exchanges the authorization code for tokens and creates a session.
///
/// # Rate Limiting
///
/// This endpoint is rate-limited per IP address to prevent brute-force attacks.
/// The limit is configurable via FRAISEQL_AUTH_CALLBACK_MAX_REQUESTS and
/// FRAISEQL_AUTH_CALLBACK_WINDOW_SECS environment variables.
///
/// # Errors
///
/// Returns `AuthError::RateLimited` if the per-IP rate limit is exceeded.
/// Returns `AuthError::OAuthError` if the provider returned an error.
/// Returns `AuthError::InvalidState` if the CSRF state token is expired or invalid.
/// Returns `AuthError` if the token exchange or session creation fails.
pub async fn auth_callback(
    State(state): State<AuthState>,
    ConnectInfo(addr): ConnectInfo<SocketAddr>,
    Query(query): Query<AuthCallbackQuery>,
) -> Result<impl IntoResponse> {
    // SECURITY: Check rate limiting for auth/callback endpoint (per IP)
    let client_ip = addr.ip().to_string();
    if state.rate_limiters.auth_callback.check(&client_ip).is_err() {
        return Err(AuthError::RateLimited {
            retry_after_secs: state.rate_limiters.auth_callback.clone_config().window_secs,
        });
    }

    // SECURITY: Reject oversized code/state before any parsing or store access.
    validate_auth_input_len(&query.code, MAX_AUTH_CODE_BYTES, "code")?;
    validate_auth_input_len(&query.state, MAX_STATE_BYTES, "state")?;

    // Check for provider error
    if let Some(error) = query.error {
        let audit_logger = get_audit_logger();
        audit_logger.log_failure(
            AuditEventType::OauthCallback,
            SecretType::AuthorizationCode,
            None,
            "exchange",
            &error,
        );
        return Err(AuthError::OAuthError {
            message: format!("{}: {}", error, query.error_description.unwrap_or_default()),
        });
    }

    // SECURITY: Validate state using configurable backend (distributed-safe)
    let (_provider_name, expiry) = state.state_store.retrieve(&query.state).await?;

    // Check state expiry with explicit error handling
    let now = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map_err(|_| AuthError::SystemTimeError {
            message: "Failed to get current system time".to_string(),
        })?
        .as_secs();

    if now > expiry {
        let audit_logger = get_audit_logger();
        audit_logger.log_failure(
            AuditEventType::CsrfStateValidated,
            SecretType::StateToken,
            None,
            "validate",
            "State token expired",
        );
        return Err(AuthError::InvalidState);
    }

    // Audit log: CSRF state validation success
    let audit_logger = get_audit_logger();
    audit_logger.log_success(
        AuditEventType::CsrfStateValidated,
        SecretType::StateToken,
        None,
        "validate",
    );

    // Exchange code for tokens
    let token_response = state.oauth_provider.exchange_code(&query.code).await?;

    // Audit log: Token exchange success
    let audit_logger = get_audit_logger();
    audit_logger.log_success(
        AuditEventType::OauthCallback,
        SecretType::AuthorizationCode,
        None,
        "exchange",
    );

    // Get user info
    let user_info = state.oauth_provider.user_info(&token_response.access_token).await?;

    // Create session (expires in 7 days)
    let expires_at = now + (7 * 24 * 60 * 60);
    let session_tokens = state.session_store.create_session(&user_info.id, expires_at).await?;

    // Audit log: Session token created
    let audit_logger = get_audit_logger();
    audit_logger.log_success(
        AuditEventType::SessionTokenCreated,
        SecretType::SessionToken,
        Some(user_info.id.clone()),
        "create",
    );

    // Audit log: Auth success
    let audit_logger = get_audit_logger();
    audit_logger.log_success(
        AuditEventType::AuthSuccess,
        SecretType::SessionToken,
        Some(user_info.id),
        "oauth_flow",
    );

    let response = AuthCallbackResponse {
        access_token:  session_tokens.access_token,
        refresh_token: Some(session_tokens.refresh_token),
        token_type:    "Bearer".to_string(),
        expires_in:    session_tokens.expires_in,
    };

    // In a real app, would redirect to frontend with tokens in URL fragment
    // For now, return JSON
    Ok(Json(response))
}

/// POST /auth/refresh - Refresh access token
///
/// Uses refresh token to obtain a new access token.
///
/// # Rate Limiting
///
/// This endpoint is rate-limited per user ID to prevent token refresh attacks.
/// The limit is configurable via FRAISEQL_AUTH_REFRESH_MAX_REQUESTS and
/// FRAISEQL_AUTH_REFRESH_WINDOW_SECS environment variables.
///
/// # Errors
///
/// Returns `AuthError::TokenExpired` if the session has expired.
/// Returns `AuthError::RateLimited` if the per-user rate limit is exceeded.
/// Returns `AuthError::Internal` if JWT signing is not yet configured.
pub async fn auth_refresh(
    State(state): State<AuthState>,
    Json(req): Json<AuthRefreshRequest>,
) -> Result<Json<AuthRefreshResponse>> {
    use crate::session::hash_token;

    // SECURITY: Reject oversized refresh tokens before hitting the session store.
    validate_auth_input_len(&req.refresh_token, MAX_REFRESH_TOKEN_BYTES, "refresh_token")?;

    // Validate refresh token exists in session store
    let token_hash = hash_token(&req.refresh_token);
    let session = state.session_store.get_session(&token_hash).await?;

    // SECURITY: Reject expired sessions before any further processing.
    // Without this check, a stolen refresh token from an expired session
    // could be used indefinitely to mint new access tokens.
    if session.is_expired() {
        let audit_logger = get_audit_logger();
        audit_logger.log_failure(
            AuditEventType::JwtRefresh,
            SecretType::RefreshToken,
            Some(session.user_id),
            "refresh",
            "Session expired",
        );
        return Err(AuthError::TokenExpired);
    }

    // SECURITY: Check rate limiting for auth/refresh endpoint (per user)
    if state.rate_limiters.auth_refresh.check(&session.user_id).is_err() {
        return Err(AuthError::RateLimited {
            retry_after_secs: state.rate_limiters.auth_refresh.clone_config().window_secs,
        });
    }

    // Audit log: Refresh token validation success
    let audit_logger = get_audit_logger();
    audit_logger.log_success(
        AuditEventType::SessionTokenValidation,
        SecretType::RefreshToken,
        Some(session.user_id),
        "validate",
    );

    // JWT signing requires an RSA/EC private key, which is not yet wired
    // into the auth state. Return an explicit error rather than a fake token.
    Err(AuthError::Internal {
        message: "JWT signing not yet implemented — configure an OIDC provider for token issuance"
            .to_string(),
    })
}

/// POST /auth/logout - Logout and revoke session
///
/// Revokes the refresh token, effectively logging out the user.
///
/// # Rate Limiting
///
/// This endpoint is rate-limited per user ID to prevent logout token exhaustion attacks.
/// The limit is configurable via FRAISEQL_AUTH_LOGOUT_MAX_REQUESTS and
/// FRAISEQL_AUTH_LOGOUT_WINDOW_SECS environment variables.
///
/// # Errors
///
/// Returns `AuthError::RateLimited` if the per-user rate limit is exceeded.
/// Returns `AuthError` if the session lookup or deletion fails.
pub async fn auth_logout(
    State(state): State<AuthState>,
    ConnectInfo(addr): ConnectInfo<SocketAddr>,
    Json(req): Json<AuthLogoutRequest>,
) -> Result<StatusCode> {
    let client_ip = addr.ip().to_string();

    if let Some(refresh_token) = req.refresh_token {
        use crate::session::hash_token;
        let token_hash = hash_token(&refresh_token);

        // Get session to extract user ID for per-user rate limiting
        let session = state.session_store.get_session(&token_hash).await?;

        // SECURITY: Check rate limiting for auth/logout endpoint (per user)
        if state.rate_limiters.auth_logout.check(&session.user_id).is_err() {
            return Err(AuthError::RateLimited {
                retry_after_secs: state.rate_limiters.auth_logout.clone_config().window_secs,
            });
        }

        state.session_store.revoke_session(&token_hash).await?;

        // Audit log: Session revoked
        let audit_logger = get_audit_logger();
        audit_logger.log_success(
            AuditEventType::SessionTokenRevoked,
            SecretType::RefreshToken,
            Some(session.user_id),
            "revoke",
        );
    } else {
        // No refresh token - use IP-based rate limiting as fallback
        if state.rate_limiters.auth_logout.check(&client_ip).is_err() {
            return Err(AuthError::RateLimited {
                retry_after_secs: state.rate_limiters.auth_logout.clone_config().window_secs,
            });
        }
    }

    Ok(StatusCode::NO_CONTENT)
}

/// Generate a cryptographically random state for CSRF protection
/// Uses OsRng for cryptographically secure randomness
#[must_use]
pub fn generate_secure_state() -> String {
    use rand::RngCore as _;

    // Generate 32 random bytes for 256 bits of entropy
    let mut bytes = [0u8; 32];
    rand::rng().fill_bytes(&mut bytes);

    // Encode as hex string for safe transmission in URLs/headers
    hex::encode(bytes)
}

/// Maximum byte length for an OAuth authorization code received at the callback.
///
/// RFC 6749 §4.1.2 places no normative cap on authorization codes, but
/// real-world providers issue codes of 32–256 ASCII characters.  512 bytes is
/// an order of magnitude above any legitimate value and prevents heap-flooding
/// via the query-string parser.
pub const MAX_AUTH_CODE_BYTES: usize = 512;

/// Maximum byte length for an OAuth `state` parameter received at the callback.
///
/// The `state` value in FraiseQL PKCE flows is a 64-character hex string
/// (32 random bytes).  When encrypted PKCE state is enabled the value is a
/// base64-encoded ciphertext that grows with the payload, but remains well
/// under 1 KiB in practice.  2048 bytes provides generous headroom while
/// bounding memory allocation from an attacker-supplied value.
pub const MAX_STATE_BYTES: usize = 2_048;

/// Maximum byte length for a refresh token submitted to `/auth/refresh`.
///
/// Session tokens are usually ≤ 2 KiB; 4 KiB covers all real-world formats
/// while bounding memory allocation for an attacker-supplied value.
pub const MAX_REFRESH_TOKEN_BYTES: usize = 4_096;

/// Guard oversized auth inputs before they reach session-store or provider logic.
///
/// Returns `AuthError::InvalidToken` with an internal reason string when
/// `input` exceeds `max_bytes`.  The reason is logged server-side and never
/// forwarded to the client.
///
/// # Errors
///
/// Returns `AuthError::InvalidToken` when `input.len() > max_bytes`.
pub fn validate_auth_input_len(
    input: &str,
    max_bytes: usize,
    field: &str,
) -> crate::error::Result<()> {
    if input.len() > max_bytes {
        return Err(crate::error::AuthError::InvalidToken {
            reason: format!("{field} exceeds maximum length ({} > {max_bytes} bytes)", input.len()),
        });
    }
    Ok(())
}

#[cfg(test)]
mod debug_redaction_tests {
    //! F045 regression — token fields in auth response types must be redacted
    //! from `Debug` output so they never reach structured logs via `?resp`.

    use super::*;

    const SECRET_ACCESS: &str = "eyJhbGciOiJIUzI1NiJ9.SUPER-SECRET-ACCESS-TOKEN.sig";
    const SECRET_REFRESH: &str = "RT-SUPER-SECRET-REFRESH-TOKEN-do-not-leak";

    #[test]
    fn auth_callback_response_debug_redacts_access_and_refresh_tokens() {
        let resp = AuthCallbackResponse {
            access_token:  SECRET_ACCESS.to_string(),
            refresh_token: Some(SECRET_REFRESH.to_string()),
            token_type:    "Bearer".to_string(),
            expires_in:    3600,
        };

        let debug_output = format!("{resp:?}");

        assert!(
            !debug_output.contains(SECRET_ACCESS),
            "access_token leaked in Debug output: {debug_output}",
        );
        assert!(
            !debug_output.contains(SECRET_REFRESH),
            "refresh_token leaked in Debug output: {debug_output}",
        );
        assert!(debug_output.contains("redacted"), "redaction marker missing: {debug_output}",);
        // The non-sensitive fields should still be present for diagnosability.
        assert!(debug_output.contains("Bearer"));
        assert!(debug_output.contains("3600"));
    }

    #[test]
    fn auth_callback_response_debug_with_no_refresh_token_shows_none() {
        let resp = AuthCallbackResponse {
            access_token:  SECRET_ACCESS.to_string(),
            refresh_token: None,
            token_type:    "Bearer".to_string(),
            expires_in:    900,
        };

        let debug_output = format!("{resp:?}");

        assert!(!debug_output.contains(SECRET_ACCESS));
        assert!(
            debug_output.contains("None"),
            "expected None to appear when refresh_token absent, got: {debug_output}",
        );
    }

    #[test]
    fn auth_refresh_response_debug_redacts_access_token() {
        let resp = AuthRefreshResponse {
            access_token: SECRET_ACCESS.to_string(),
            token_type:   "Bearer".to_string(),
            expires_in:   1800,
        };

        let debug_output = format!("{resp:?}");

        assert!(
            !debug_output.contains(SECRET_ACCESS),
            "access_token leaked in Debug output: {debug_output}",
        );
        assert!(debug_output.contains("redacted"), "redaction marker missing: {debug_output}",);
        assert!(debug_output.contains("Bearer"));
        assert!(debug_output.contains("1800"));
    }
}