rust-webx-host 1.3.0

//! JWT authentication module for the rust-webx framework.
//!
//! Provides `JwtAuth` —an `IAuthenticationHandler` implementation that reads
//! a Bearer token from the `Authorization` header and validates it using
//! the `jsonwebtoken` crate.
//!
//! # Issuance and revocation (WEBX-2)
//!
//! Minting and invalidation are ports, so application code does not need its
//! own signing or session code:
//!
//! * [`JwtTokenIssuer`] implements `ITokenIssuer` and is registered
//!   automatically by `HostBuilder::add_authentication()` from `Jwt.Secret`.
//!   A login handler injects `Arc<dyn ITokenIssuer>` and calls
//!   [`ITokenIssuer::issue`].
//! * `.use_session_store(store)` registers an `ISessionStore`; the auth
//!   middleware then rejects a token whose `jti` was revoked. Revocation is
//!   opt-in: without a store the middleware only verifies signatures.
//!
//! # Secret sources (XR-2)
//!
//! The signing secret comes from the first non-empty of `APP__Jwt__Secret` /
//! `JWT_SECRET`, `Jwt.Secret`, and `Jwt.SecretFile`. The last one is read by
//! [`apply_jwt_secret_file`] during host start-up — a missing, unreadable,
//! short or (on Unix) group/other-accessible file aborts start-up with a
//! readable error instead of signing tokens with a broken key.
//!
//! ```ignore
//! // login: issue and remember the jti (or give it to the client)
//! let issued = token_issuer.issue(TokenClaims::new(&user.id)).await?;
//! // logout: revoke it; the next request with that token is 401
//! session_store.revoke(&issued.jti).await?;
//! ```
//!
//! # Example
//!
//! ```ignore
//! use webx_host::auth_jwt::{JwtAuth, jwt_middleware};
//! use jsonwebtoken::{DecodingKey, Validation};
//!
//! let auth = JwtAuth::new(
//!     DecodingKey::from_secret(b"my-secret"),
//!     Validation::default(),
//! );
//! let middleware = jwt_middleware(Arc::new(auth));
//! ```

use jsonwebtoken::{decode, encode, DecodingKey, EncodingKey, Header, Validation};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::ops::ControlFlow;
use std::path::Path;
use std::sync::{Arc, OnceLock};
use std::time::{Duration, SystemTime, UNIX_EPOCH};
use webx_core::auth::{IAuthenticationHandler, IClaims};
use webx_core::config::AppOptions;
use webx_core::error::{Error, Result};
use webx_core::http::IHttpContext;
use webx_core::middleware::IMiddleware;
use webx_core::security::{ISessionStore, ITokenIssuer, IssuedToken, TokenClaims};

// ---------------------------------------------------------------------------
// JwtClaims —IClaims implementation backed by JWT payload
// ---------------------------------------------------------------------------

/// Claims extracted from a JWT token.
///
/// By default, looks for `sub`, `roles`, and `permissions` claims.
/// All other claims are accessible via `claims()` as stringified values.
pub struct JwtClaims {
    sub: String,
    roles: Vec<String>,
    permissions: Vec<String>,
    /// Pre-flattened raw claims map for the `claims()` method.
    raw: HashMap<String, String>,
}

/// Intermediate deserialization target. After deserialization we convert
/// into `JwtClaims` which stores pre-computed data for `IClaims`.
#[derive(Debug, Deserialize, Serialize)]
struct RawClaims {
    #[serde(default)]
    sub: String,
    #[serde(default)]
    roles: Vec<String>,
    #[serde(default)]
    permissions: Vec<String>,
    #[serde(flatten)]
    extra: HashMap<String, serde_json::Value>,
}

impl JwtClaims {
    /// Create empty claims with just a subject.
    pub fn new(subject: impl Into<String>) -> Self {
        let sub = subject.into();
        let mut raw = HashMap::new();
        raw.insert("sub".to_string(), sub.clone());
        Self {
            sub,
            roles: Vec::new(),
            permissions: Vec::new(),
            raw,
        }
    }
}

impl From<RawClaims> for JwtClaims {
    fn from(rc: RawClaims) -> Self {
        let mut raw = HashMap::new();
        raw.insert("sub".to_string(), rc.sub.clone());
        for (k, v) in &rc.extra {
            match v {
                serde_json::Value::String(s) => {
                    raw.insert(k.clone(), s.clone());
                }
                other => {
                    raw.insert(k.clone(), other.to_string());
                }
            }
        }
        Self {
            sub: rc.sub,
            roles: rc.roles,
            permissions: rc.permissions,
            raw,
        }
    }
}

impl IClaims for JwtClaims {
    fn subject(&self) -> &str {
        &self.sub
    }

    fn roles(&self) -> &[String] {
        &self.roles
    }

    fn permissions(&self) -> &[String] {
        &self.permissions
    }

    fn claims(&self) -> &HashMap<String, String> {
        &self.raw
    }

    fn clone_box(&self) -> Box<dyn IClaims> {
        Box::new(Self {
            sub: self.sub.clone(),
            roles: self.roles.clone(),
            permissions: self.permissions.clone(),
            raw: self.raw.clone(),
        })
    }
}

// ---------------------------------------------------------------------------
// JwtAuth —IAuthenticationHandler implementation
// ---------------------------------------------------------------------------

/// JWT-based authentication handler.
///
/// Reads the `Authorization: Bearer <token>` header, decodes and validates
/// the JWT, and returns the resulting claims. Only a **valid** token produces
/// claims: a missing header, a non-`Bearer` scheme or a token that fails
/// validation all yield `Ok(None)` — the request simply continues as anonymous.
pub struct JwtAuth {
    decoding_key: DecodingKey,
    validation: Validation,
}

impl JwtAuth {
    /// Create a new JWT authenticator.
    pub fn new(decoding_key: DecodingKey, validation: Validation) -> Self {
        Self {
            decoding_key,
            validation,
        }
    }
}

#[async_trait::async_trait]
impl IAuthenticationHandler for JwtAuth {
    async fn authenticate(&self, ctx: &mut dyn IHttpContext) -> Result<Option<Box<dyn IClaims>>> {
        // Extract token synchronously —avoids holding &dyn IHttpContext
        // across any async boundary, keeping the future Send.
        let header = match ctx.request().header("authorization") {
            Some(h) => h,
            None => return Ok(None),
        };

        // RFC 6750: scheme is case-insensitive
        let token = if header.len() >= 7 && header[..7].eq_ignore_ascii_case("Bearer ") {
            header[7..].trim().to_string()
        } else {
            return Ok(None);
        };

        if token.is_empty() {
            return Ok(None);
        }

        // A rejected token means "not authenticated", not "reject the request":
        // the request continues as anonymous and the endpoint decides. This is
        // what keeps a public endpoint (login, health, docs) reachable while a
        // client still holds an expired token, instead of dead-locking it with a
        // 401 on every call. Protected endpoints respond 401 further down the
        // pipeline (`#[authorize]` rules or a required `#[fromclaim]` identity),
        // through the single unauthorized writer (detail "authentication
        // required" + `WWW-Authenticate`).
        let token_data = match decode::<RawClaims>(&token, &self.decoding_key, &self.validation) {
            Ok(data) => data,
            Err(e) => {
                // The decoder's message is for operators, not for the client
                // (it names InvalidToken/ExpiredSignature/InvalidAlgorithm/...).
                tracing::debug!(reason = %e, "JWT rejected");
                return Ok(None);
            }
        };

        let claims: JwtClaims = token_data.claims.into();
        Ok(Some(Box::new(claims)))
    }
}

// ---------------------------------------------------------------------------
// JwtTokenIssuer —ITokenIssuer implementation (default token minting)
// ---------------------------------------------------------------------------

/// Default token lifetime used by [`JwtTokenIssuer::from_secret`] when the
/// caller does not pass one explicitly.
///
/// The host does **not** use this constant: `add_authentication()` builds the
/// issuer from the `Jwt.ExpirationMinutes` appsettings key (default 60 minutes).
pub const DEFAULT_TOKEN_LIFETIME: Duration = Duration::from_secs(3600);

fn unix_now() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|elapsed| elapsed.as_secs())
        .unwrap_or_default()
}

/// JWT token issuer — the default [`ITokenIssuer`].
///
/// **HS256 only.** The token is signed with `HS256` and verified by this
/// crate's `JwtAuth`, whose `Validation::default()` also expects `HS256`, so
/// issuer and verifier agree out of the box. Asymmetric algorithms (RSA/EC)
/// are not supported by this type: using one requires *both* a custom
/// [`ITokenIssuer`] and a custom [`IAuthenticationHandler`] (the host's
/// `jwt_middleware` always verifies with `Validation::default()`).
///
/// Mints a token carrying `sub`, `roles`, `permissions`, the caller's extra
/// claims, and the framework-managed `jti` / `iat` / `exp`. The `jti` is what
/// [`ISessionStore::revoke`] later invalidates, so a login endpoint only needs:
///
/// ```ignore
/// let issued = issuer.issue(TokenClaims::new(&user.id)).await?;
/// sessions.revoke(&issued.jti).await?; // logout
/// ```
///
/// `HostBuilder::add_authentication()` registers one from the configured
/// `Jwt.Secret` / `Jwt.ExpirationMinutes`; register a custom [`ITokenIssuer`] in
/// DI to replace it.
pub struct JwtTokenIssuer {
    encoding_key: EncodingKey,
    default_lifetime: Duration,
    issuer: Option<String>,
    audience: Option<String>,
}

impl JwtTokenIssuer {
    /// Build an HS256 issuer from a shared secret — the same secret
    /// `JwtAuth` verifies with.
    ///
    /// `default_lifetime` applies when [`TokenClaims::expires_in`] is `None`;
    /// `DEFAULT_TOKEN_LIFETIME` (1 hour) is the framework default.
    pub fn from_secret(secret: impl AsRef<[u8]>, default_lifetime: Duration) -> Self {
        Self {
            encoding_key: EncodingKey::from_secret(secret.as_ref()),
            default_lifetime,
            issuer: None,
            audience: None,
        }
    }

    /// Set the `iss` claim.
    pub fn with_issuer(mut self, issuer: impl Into<String>) -> Self {
        self.issuer = Some(issuer.into());
        self
    }

    /// Set the `aud` claim.
    pub fn with_audience(mut self, audience: impl Into<String>) -> Self {
        self.audience = Some(audience.into());
        self
    }
}

#[async_trait::async_trait]
impl ITokenIssuer for JwtTokenIssuer {
    async fn issue(&self, claims: TokenClaims) -> Result<IssuedToken> {
        let subject = claims.subject.trim();
        if subject.is_empty() {
            return Err(Error::Validation(
                "token subject must not be empty".to_string(),
            ));
        }

        let lifetime = claims.expires_in.unwrap_or(self.default_lifetime);
        let issued_at = unix_now();
        let expires_at_unix_secs = issued_at.saturating_add(lifetime.as_secs());
        let jti = uuid::Uuid::new_v4().to_string();

        // Extra claims first: reserved claims must win, otherwise a caller could
        // override `sub`/`exp`/`jti` through `TokenClaims::extra`.
        let mut payload = serde_json::Map::new();
        for (key, value) in &claims.extra {
            payload.insert(key.clone(), serde_json::Value::String(value.clone()));
        }
        payload.insert("sub".into(), serde_json::json!(subject));
        payload.insert("roles".into(), serde_json::json!(claims.roles));
        payload.insert("permissions".into(), serde_json::json!(claims.permissions));
        payload.insert("jti".into(), serde_json::json!(jti));
        payload.insert("iat".into(), serde_json::json!(issued_at));
        payload.insert("exp".into(), serde_json::json!(expires_at_unix_secs));
        if let Some(issuer) = &self.issuer {
            payload.insert("iss".into(), serde_json::json!(issuer));
        }
        if let Some(audience) = &self.audience {
            payload.insert("aud".into(), serde_json::json!(audience));
        }

        // `Header::default()` is `HS256` — the only algorithm this issuer
        // promises, and the one `JwtAuth` verifies.
        let token = encode(
            &Header::default(),
            &serde_json::Value::Object(payload),
            &self.encoding_key,
        )
        .map_err(|error| Error::Internal(format!("JWT signing failed: {error}")))?;

        Ok(IssuedToken {
            token,
            jti,
            expires_at_unix_secs,
        })
    }
}

// ---------------------------------------------------------------------------
// Middleware
// ---------------------------------------------------------------------------

/// Authentication middleware: verify the token, then reject revoked tokens.
struct AuthMiddleware {
    handler: Arc<dyn IAuthenticationHandler>,
    /// `None` = signature verification only (1.1 behaviour).
    session_store: Option<Arc<dyn ISessionStore>>,
}

#[async_trait::async_trait]
impl IMiddleware for AuthMiddleware {
    async fn invoke(&self, ctx: &mut dyn IHttpContext) -> Result<ControlFlow<()>> {
        if let Some(claims) = self.handler.authenticate(ctx).await? {
            if let Some(store) = &self.session_store {
                // A token without `jti` cannot be matched against a revocation
                // record; it keeps its `exp`-based lifetime (no re-reject).
                if let Some(jti) = claims.jti() {
                    if store.is_revoked(jti).await? {
                        // Revoked credentials are a credentials problem, not an
                        // anonymous request: fail here so the host writes its
                        // single 401 (problem+json + `WWW-Authenticate`).
                        return Err(Error::Unauthorized("token has been revoked".to_string()));
                    }
                }
            }
            // IHttpContext extends IClaimsExt, so set_claims is available directly.
            ctx.set_claims(claims);
        }
        Ok(ControlFlow::Continue(()))
    }
}

/// Create a JWT authentication middleware from an authentication handler.
///
/// Reads the Bearer token from `Authorization` header, validates it, and
/// stores the resulting claims in the HTTP context for downstream use.
pub fn jwt_middleware(handler: Arc<dyn IAuthenticationHandler>) -> impl IMiddleware {
    AuthMiddleware {
        handler,
        session_store: None,
    }
}

/// Create a JWT authentication middleware that also rejects revoked tokens.
///
/// After the signature check, the token's `jti` is looked up in `session_store`;
/// a revoked token is answered with the framework's 401 (problem+json +
/// `WWW-Authenticate`) before the endpoint runs. Tokens without a `jti` pass
/// through unchanged.
///
/// **Advanced entry point** — only for a hand-assembled middleware pipeline.
/// A regular host enables revocation with
/// [`HostBuilder::use_session_store`](crate::server::HostBuilder::use_session_store),
/// which registers the store and wires this middleware itself.
pub fn jwt_middleware_with_revocation(
    handler: Arc<dyn IAuthenticationHandler>,
    session_store: Arc<dyn ISessionStore>,
) -> impl IMiddleware {
    AuthMiddleware {
        handler,
        session_store: Some(session_store),
    }
}

// ---------------------------------------------------------------------------
// Global JWT encoding secret (for token creation in handlers)
// ---------------------------------------------------------------------------

static JWT_ENCODING_SECRET: OnceLock<String> = OnceLock::new();

/// Initialize the global JWT encoding secret from the configured secret.
/// This is called automatically by `.add_authentication()` on the `HostBuilder`,
/// but can also be called manually if needed.
///
/// Idempotent: subsequent calls are no-ops (the first secret wins).
pub fn init_jwt_secret(secret: &str) {
    let _ = JWT_ENCODING_SECRET.set(secret.to_owned());
}

/// Retrieve the global JWT encoding secret previously set via [`init_jwt_secret`].
///
/// # Panics
/// Panics if [`init_jwt_secret`] has not been called yet.
pub fn jwt_secret() -> &'static str {
    JWT_ENCODING_SECRET
        .get()
        .expect("init_jwt_secret must be called before jwt_secret")
}

// ---------------------------------------------------------------------------
// Jwt.SecretFile resolution (XR-2)
// ---------------------------------------------------------------------------

/// Minimum accepted length, in bytes, of a JWT signing secret read from a file.
///
/// HS256 keys shorter than 256 bits are brute-forceable, so a too-short file is
/// a startup error rather than a warning.
pub const MIN_JWT_SECRET_LEN: usize = 32;

/// Resolve `Jwt.SecretFile` into `Jwt.Secret`, failing fast on a bad file.
///
/// This is the third source in the documented priority chain — the first
/// non-empty one wins:
///
/// 1. `APP__Jwt__Secret` / `JWT_SECRET` — applied over the JSON by
///    `webx_core::config::load_appsettings`, so they are already in `Secret`;
/// 2. `Jwt.Secret` — an explicit value in `appsettings.json` or a
///    `HostBuilder` `useOptions` override;
/// 3. `Jwt.SecretFile` — the path configured here, read from disk.
///
/// The host calls this once while preparing itself (before the default
/// `ITokenIssuer` and the authentication middleware are built), so every later
/// reader of `options.jwt.secret` — issuer, verifier, `init_jwt_secret`, the
/// Production weak-secret guard — sees the resolved value.
///
/// # Behaviour
///
/// * No-op (`Ok(())`) when a secret is already configured or `SecretFile` is
///   unset/blank, so existing appsettings are unaffected.
/// * The file's content is trimmed; its surrounding whitespace (e.g. the
///   trailing newline `echo` writes) is not part of the key.
/// * Fails with [`Error::Di`] — a host startup error, never a panic — when the
///   file is missing/unreadable, empty, shorter than [`MIN_JWT_SECRET_LEN`]
///   bytes, or (on Unix) accessible by group/other. `Error::Di` is what the
///   existing Production configuration guards return; the message names the
///   path and the fix so an operator can act on it.
/// * **Windows:** the ACL is *not* validated — the POSIX mode model does not
///   exist there. Restrict the file to the service account (and
///   `Administrators`) yourself. DPAPI-wrapped secrets are a future item, not
///   part of this release.
///
/// # Example
///
/// ```
/// use webx_core::config::AppOptions;
/// use webx_host::auth_jwt::apply_jwt_secret_file;
///
/// let path = std::env::temp_dir().join(format!(
///     "webx-jwt-secret-{}-{}.key",
///     std::process::id(),
///     std::time::SystemTime::now()
///         .duration_since(std::time::UNIX_EPOCH)
///         .unwrap()
///         .as_nanos()
/// ));
/// # #[cfg(unix)]
/// # {
/// # use std::os::unix::fs::PermissionsExt;
/// # std::fs::write(&path, b"test-only-secret-material-32-bytes\n").unwrap();
/// # std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o600)).unwrap();
/// # }
/// # #[cfg(not(unix))]
/// # std::fs::write(&path, b"test-only-secret-material-32-bytes\n").unwrap();
///
/// let mut options = AppOptions::default();
/// options.jwt.secret_file = Some(path.to_string_lossy().into_owned());
/// apply_jwt_secret_file(&mut options).unwrap();
/// assert_eq!(options.jwt.secret, "test-only-secret-material-32-bytes");
///
/// # std::fs::remove_file(&path).ok();
/// ```
pub fn apply_jwt_secret_file(options: &mut AppOptions) -> Result<()> {
    if !options.jwt.secret.trim().is_empty() {
        if options.jwt.secret_file.is_some() {
            // Deliberate, documented precedence — `Jwt.Secret` wins.
            tracing::debug!("[Auth] Jwt.Secret is set; ignoring Jwt.SecretFile");
        }
        return Ok(());
    }

    let Some(path) = options
        .jwt
        .secret_file
        .as_deref()
        .map(str::trim)
        .filter(|path| !path.is_empty())
    else {
        return Ok(());
    };

    let secret = read_jwt_secret_file(Path::new(path))?;
    tracing::info!(
        "[Auth] JWT signing secret loaded from '{}' ({} bytes)",
        path,
        secret.len()
    );
    options.jwt.secret = secret;
    Ok(())
}

fn read_jwt_secret_file(path: &Path) -> Result<String> {
    verify_secret_file_permissions(path)?;

    let content = std::fs::read_to_string(path).map_err(|error| {
        Error::Di(format!(
            "JWT secret file '{}' could not be read: {error}. \
             Provision a readable file (at least {MIN_JWT_SECRET_LEN} bytes, Unix mode 0600), \
             or set Jwt.Secret / APP__Jwt__Secret / JWT_SECRET.",
            path.display()
        ))
    })?;
    let secret = content.trim();
    if secret.is_empty() {
        return Err(Error::Di(format!(
            "JWT secret file '{}' is empty; it must contain at least {MIN_JWT_SECRET_LEN} bytes of secret material.",
            path.display()
        )));
    }
    if secret.len() < MIN_JWT_SECRET_LEN {
        return Err(Error::Di(format!(
            "JWT secret file '{}' contains only {} bytes; at least {MIN_JWT_SECRET_LEN} bytes are required.",
            path.display(),
            secret.len()
        )));
    }
    Ok(secret.to_string())
}

/// Reject a secret file that group/other can read or write (Unix only).
///
/// The POSIX analog of "the key file is private": anything but mode `0600`-or-
/// stricter (e.g. `0400`, `0700` for the owner) is refused. On Windows the ACL
/// is not inspected — start-up trusts the operator there.
#[cfg(unix)]
fn verify_secret_file_permissions(path: &Path) -> Result<()> {
    use std::os::unix::fs::PermissionsExt;

    let metadata = std::fs::metadata(path).map_err(|error| {
        Error::Di(format!(
            "JWT secret file '{}' could not be inspected: {error}. \
             Provision it (at least {MIN_JWT_SECRET_LEN} bytes, Unix mode 0600), \
             or set Jwt.Secret / APP__Jwt__Secret / JWT_SECRET.",
            path.display()
        ))
    })?;
    let mode = metadata.permissions().mode();
    // 0o077 covers group/other read, write and execute bits.
    if mode & 0o077 != 0 {
        return Err(Error::Di(format!(
            "JWT secret file '{}' has mode {mode:04o}; group/other access must be removed (`chmod 600`).",
            path.display()
        )));
    }
    Ok(())
}

/// Windows (and other non-Unix targets): no permission model to inspect.
#[cfg(not(unix))]
fn verify_secret_file_permissions(_path: &Path) -> Result<()> {
    Ok(())
}