box_open_sdk/runtime/

auth.rs

// Code generated by box-gantry (vendored from runtimes/rust/gantryruntime/src/auth.rs). DO NOT EDIT.

//! The Box auth flows, each producing an [`Auth`] passed to
//! [`Client::new`](super::Client::new). `developer_token` is a fixed token;
//! `client_credentials` (CCG) and `oauth` exchange credentials at Box's token
//! endpoint and cache the resulting access token until shortly before it
//! expires (TR-Rust.5).
//!
//! JWT server auth (signing-key assertions) lands in the next runtime slice;
//! the three flows here cover fixed-token and both refresh-based exchanges.

use std::sync::Arc;
use std::time::{Duration, Instant};

use tokio::sync::Mutex;

use super::jwt::{JwtConfig, Signer};
use super::Error;

/// Box's OAuth 2.0 token endpoint, shared by every exchange flow.
const DEFAULT_TOKEN_URL: &str = "https://api.box.com/oauth2/token";

/// Where a user is sent to grant an OAuth 2.0 app access.
const AUTHORIZE_URL: &str = "https://account.box.com/api/oauth2/authorize";

/// Refresh a cached token this long before expiry so in-flight requests never
/// race an expiry.
const REFRESH_MARGIN: Duration = Duration::from_secs(60);

/// The configured authentication flow. Build one with [`Auth::developer_token`],
/// [`Auth::client_credentials`], or [`Auth::oauth`], then pass it to
/// [`Client::new`](super::Client::new).
pub struct Auth {
    source: Source,
}

/// One of the supported token sources.
enum Source {
    /// A fixed developer-console token.
    Developer(String),
    /// A cached token refreshed by re-posting a fixed grant form (CCG).
    Form(FormSource),
    /// A cached token refreshed with a rotating refresh token (OAuth 2.0).
    OAuth(OAuthSource),
    /// A cached token refreshed by signing a fresh JWT bearer assertion. Boxed:
    /// the parsed RSA key makes this variant far larger than the others.
    Jwt(Box<JwtSource>),
}

impl Auth {
    /// The simplest flow: a fixed access token from the Box developer console.
    pub fn developer_token(token: impl Into<String>) -> Auth {
        Auth {
            source: Source::Developer(token.into()),
        }
    }

    /// Client Credentials Grant: server-to-server auth with no signing key. Set
    /// exactly one subject on the config — `enterprise_id` for the service
    /// account, or `user_id` to act as a managed user.
    pub fn client_credentials(config: CcgConfig) -> Auth {
        let (subject_type, subject_id) = match &config.user_id {
            Some(user) => ("user", user.clone()),
            None => ("enterprise", config.enterprise_id.clone()),
        };
        let form = vec![
            ("grant_type".to_string(), "client_credentials".to_string()),
            ("client_id".to_string(), config.client_id),
            ("client_secret".to_string(), config.client_secret),
            ("box_subject_type".to_string(), subject_type.to_string()),
            ("box_subject_id".to_string(), subject_id),
        ];
        Auth {
            source: Source::Form(FormSource {
                http: auth_http_client(),
                token_url: config.token_url.unwrap_or_else(default_token_url),
                form,
                cached: Mutex::new(Cached::empty()),
            }),
        }
    }

    /// JWT server auth: sign a short-lived RSA assertion (from the app's
    /// `box_config.json`) and exchange it for an access token. Set exactly one
    /// subject on the config — `enterprise_id` or `user_id`.
    ///
    /// Fallible: the RSA private key is parsed (and if needed decrypted) up
    /// front, so a bad key fails here rather than on the first request.
    pub fn jwt(config: JwtConfig) -> Result<Auth, Error> {
        let signer = Signer::new(&config)?;
        Ok(Auth {
            source: Source::Jwt(Box::new(JwtSource {
                http: auth_http_client(),
                token_url: config.token_url.unwrap_or_else(default_token_url),
                client_id: config.client_id,
                client_secret: config.client_secret,
                signer,
                cached: Mutex::new(Cached::empty()),
            })),
        })
    }

    /// Resume the OAuth 2.0 authorization-code flow from a previously stored
    /// refresh token, exchanging it for access tokens as needed. Box rotates
    /// the refresh token on each exchange, so the newest one is retained.
    ///
    /// The rotated token is held in memory only; use [`Auth::oauth_with_store`]
    /// to persist each rotation durably across restarts.
    pub fn oauth(config: OAuthConfig, refresh_token: impl Into<String>) -> Auth {
        Self::oauth_source(config, refresh_token.into(), None)
    }

    /// Like [`Auth::oauth`], but persists each rotated refresh token through a
    /// [`RefreshTokenStore`] before returning — so an app restart reloads the
    /// live token instead of a refresh token Box has already invalidated.
    pub fn oauth_with_store(
        config: OAuthConfig,
        refresh_token: impl Into<String>,
        store: Arc<dyn RefreshTokenStore>,
    ) -> Auth {
        Self::oauth_source(config, refresh_token.into(), Some(store))
    }

    fn oauth_source(
        config: OAuthConfig,
        refresh_token: String,
        store: Option<Arc<dyn RefreshTokenStore>>,
    ) -> Auth {
        Auth {
            source: Source::OAuth(OAuthSource {
                http: auth_http_client(),
                token_url: config.token_url.clone().unwrap_or_else(default_token_url),
                client_id: config.client_id,
                client_secret: config.client_secret,
                store,
                state: Mutex::new(OAuthState {
                    token: String::new(),
                    expiry: Instant::now(),
                    refresh_token,
                    // The caller-supplied token is already durable.
                    refresh_token_persisted: true,
                }),
            }),
        }
    }

    /// A valid access token for the configured flow.
    pub(crate) async fn access_token(&self) -> Result<String, Error> {
        match &self.source {
            Source::Developer(token) => Ok(token.clone()),
            Source::Form(source) => source.access_token().await,
            Source::OAuth(source) => source.access_token().await,
            Source::Jwt(source) => source.access_token().await,
        }
    }

    /// Force-acquire a token after the current one was rejected (a 401),
    /// bypassing the freshness cache. Single-flight: if another task already
    /// replaced the rejected `stale` token, that new token is returned instead
    /// of refreshing again. A fixed developer token has nothing to refresh, so
    /// it is returned unchanged (the retry then surfaces the 401).
    pub(crate) async fn force_refresh(&self, stale: &str) -> Result<String, Error> {
        match &self.source {
            Source::Developer(token) => Ok(token.clone()),
            Source::Form(source) => source.force_refresh(stale).await,
            Source::OAuth(source) => source.force_refresh(stale).await,
            Source::Jwt(source) => source.force_refresh(stale).await,
        }
    }
}

/// A durable store for the rotating OAuth refresh token. Box invalidates the
/// previous refresh token on each exchange, so an app that restarts must reload
/// the newest one — implement this to persist each rotation (a file, a DB row,
/// a secret manager).
///
/// `save` is `async` so a store can do real I/O without blocking the executor
/// (do the I/O with async APIs, or offload sync work via
/// `tokio::task::spawn_blocking`). It runs before a freshly rotated token is
/// returned; its failure propagates on the rotating call, and the runtime keeps
/// retrying persistence on later calls until it succeeds, so a rotation is never
/// silently treated as durable when it is not.
#[async_trait::async_trait]
pub trait RefreshTokenStore: Send + Sync {
    /// Persist the newly rotated refresh token durably.
    async fn save(&self, refresh_token: &str) -> Result<(), Error>;
}

/// The cached token if it is present and not within the refresh margin of
/// expiry (shared by both caching sources).
fn fresh_token(token: &str, expiry: Instant) -> Option<String> {
    if !token.is_empty() && expiry.saturating_duration_since(Instant::now()) > REFRESH_MARGIN {
        Some(token.to_string())
    } else {
        None
    }
}

/// A cached access token and its expiry instant.
struct Cached {
    token: String,
    expiry: Instant,
}

impl Cached {
    fn empty() -> Cached {
        Cached {
            token: String::new(),
            expiry: Instant::now(),
        }
    }

    fn fresh(&self) -> Option<String> {
        fresh_token(&self.token, self.expiry)
    }

    fn store(&mut self, token: String, ttl: Duration) {
        self.expiry = Instant::now() + ttl;
        self.token = token;
    }
}

/// A token source that refreshes by re-posting a fixed grant form (CCG).
struct FormSource {
    http: reqwest::Client,
    token_url: String,
    form: Vec<(String, String)>,
    cached: Mutex<Cached>,
}

impl FormSource {
    async fn access_token(&self) -> Result<String, Error> {
        let mut cached = self.cached.lock().await;
        if let Some(token) = cached.fresh() {
            return Ok(token);
        }
        self.refresh_locked(&mut cached).await
    }

    async fn force_refresh(&self, stale: &str) -> Result<String, Error> {
        let mut cached = self.cached.lock().await;
        // Single-flight: a concurrent 401 may already have replaced the token.
        if let Some(token) = cached.fresh() {
            if token != stale {
                return Ok(token);
            }
        }
        self.refresh_locked(&mut cached).await
    }

    async fn refresh_locked(&self, cached: &mut Cached) -> Result<String, Error> {
        let response = post_token_form(&self.http, &self.token_url, &self.form).await?;
        cached.store(response.access_token.clone(), response.ttl());
        Ok(response.access_token)
    }
}

/// A token source that refreshes by signing a fresh JWT bearer assertion and
/// exchanging it (server auth with a signing key). Like [`FormSource`], but the
/// grant form is re-minted each refresh — each assertion is single-use.
struct JwtSource {
    http: reqwest::Client,
    token_url: String,
    client_id: String,
    client_secret: String,
    signer: Signer,
    cached: Mutex<Cached>,
}

impl JwtSource {
    async fn access_token(&self) -> Result<String, Error> {
        let mut cached = self.cached.lock().await;
        if let Some(token) = cached.fresh() {
            return Ok(token);
        }
        self.refresh_locked(&mut cached).await
    }

    async fn force_refresh(&self, stale: &str) -> Result<String, Error> {
        let mut cached = self.cached.lock().await;
        // Single-flight: a concurrent 401 may already have replaced the token.
        if let Some(token) = cached.fresh() {
            if token != stale {
                return Ok(token);
            }
        }
        self.refresh_locked(&mut cached).await
    }

    async fn refresh_locked(&self, cached: &mut Cached) -> Result<String, Error> {
        let assertion = self.signer.assertion(&self.token_url)?;
        let form = vec![
            (
                "grant_type".to_string(),
                "urn:ietf:params:oauth:grant-type:jwt-bearer".to_string(),
            ),
            ("assertion".to_string(), assertion),
            ("client_id".to_string(), self.client_id.clone()),
            ("client_secret".to_string(), self.client_secret.clone()),
        ];
        let response = post_token_form(&self.http, &self.token_url, &form).await?;
        cached.store(response.access_token.clone(), response.ttl());
        Ok(response.access_token)
    }
}

/// The OAuth 2.0 refresh-token source: it rotates the refresh token Box returns
/// (Box invalidates the old one each exchange) and, when configured, persists
/// each rotation through a [`RefreshTokenStore`].
struct OAuthSource {
    http: reqwest::Client,
    token_url: String,
    client_id: String,
    client_secret: String,
    store: Option<Arc<dyn RefreshTokenStore>>,
    state: Mutex<OAuthState>,
}

struct OAuthState {
    token: String,
    expiry: Instant,
    refresh_token: String,
    /// Whether `refresh_token` is known durable in the store. The initial token
    /// came from the caller (already stored); only later rotations start `false`
    /// until their `save` succeeds.
    refresh_token_persisted: bool,
}

impl OAuthSource {
    async fn access_token(&self) -> Result<String, Error> {
        let mut state = self.state.lock().await;
        self.retry_persist(&mut state).await;
        if let Some(token) = fresh_token(&state.token, state.expiry) {
            return Ok(token);
        }
        self.refresh_locked(&mut state).await
    }

    async fn force_refresh(&self, stale: &str) -> Result<String, Error> {
        let mut state = self.state.lock().await;
        self.retry_persist(&mut state).await;
        // Single-flight: a concurrent 401 may already have replaced the token.
        if let Some(token) = fresh_token(&state.token, state.expiry) {
            if token != stale {
                return Ok(token);
            }
        }
        self.refresh_locked(&mut state).await
    }

    /// Best-effort retry of a rotation whose earlier `save` failed, so a
    /// transient store outage doesn't leave the durable copy behind the live
    /// token forever. The first failure was already surfaced by `refresh_locked`;
    /// these retries stay silent so a still-down store can't wedge every call.
    async fn retry_persist(&self, state: &mut OAuthState) {
        if state.refresh_token_persisted {
            return;
        }
        match &self.store {
            Some(store) => {
                if store.save(&state.refresh_token).await.is_ok() {
                    state.refresh_token_persisted = true;
                }
            }
            None => state.refresh_token_persisted = true,
        }
    }

    async fn refresh_locked(&self, state: &mut OAuthState) -> Result<String, Error> {
        let form = vec![
            ("grant_type".to_string(), "refresh_token".to_string()),
            ("refresh_token".to_string(), state.refresh_token.clone()),
            ("client_id".to_string(), self.client_id.clone()),
            ("client_secret".to_string(), self.client_secret.clone()),
        ];
        let response = post_token_form(&self.http, &self.token_url, &form).await?;
        state.token = response.access_token.clone();
        state.expiry = Instant::now() + response.ttl();
        if let Some(refresh) = &response.refresh_token {
            state.refresh_token = refresh.clone();
            // The rotation isn't durable until the store confirms it. Box has
            // already invalidated the previous token, so on a save failure we
            // keep the new token in memory (marked unpersisted, retried on later
            // calls) but surface the error now.
            state.refresh_token_persisted = self.store.is_none();
            if let Some(store) = &self.store {
                store.save(refresh).await?;
                state.refresh_token_persisted = true;
            }
        }
        Ok(response.access_token)
    }
}

/// The Client Credentials Grant config: server-to-server auth with no signing
/// key. Set exactly one subject — `enterprise_id` for the service account, or
/// `user_id` to act as a managed user. Derives `Default` so the optional
/// `user_id`/`token_url` can be elided with `..Default::default()`.
#[derive(Clone, Default)]
pub struct CcgConfig {
    pub client_id: String,
    pub client_secret: String,
    pub enterprise_id: String,
    /// Optional: act as a managed user instead of the enterprise service account.
    pub user_id: Option<String>,
    /// Optional: defaults to Box's token endpoint (custom deployments).
    pub token_url: Option<String>,
}

/// The OAuth 2.0 authorization-code config. Use [`OAuthConfig::authorize_url`]
/// to build the redirect, [`OAuthConfig::exchange_code`] to turn the returned
/// code into an [`Auth`], or [`Auth::oauth`] to resume from a stored refresh
/// token.
#[derive(Clone)]
pub struct OAuthConfig {
    pub client_id: String,
    pub client_secret: String,
    /// Optional: defaults to Box's token endpoint (custom deployments).
    pub token_url: Option<String>,
}

impl OAuthConfig {
    /// Build the URL to redirect a user to so they can grant access. `state` is
    /// echoed back to the redirect URI for CSRF protection.
    pub fn authorize_url(&self, redirect_uri: &str, state: &str) -> String {
        let query = form_urlencode(&[
            ("response_type", "code"),
            ("client_id", &self.client_id),
            ("redirect_uri", redirect_uri),
            ("state", state),
        ]);
        format!("{AUTHORIZE_URL}?{query}")
    }

    /// Exchange an authorization code for an [`Auth`] that refreshes itself
    /// thereafter.
    pub async fn exchange_code(&self, code: &str, redirect_uri: &str) -> Result<Auth, Error> {
        let http = auth_http_client();
        let token_url = self.token_url.clone().unwrap_or_else(default_token_url);
        let form = vec![
            ("grant_type".to_string(), "authorization_code".to_string()),
            ("code".to_string(), code.to_string()),
            ("client_id".to_string(), self.client_id.clone()),
            ("client_secret".to_string(), self.client_secret.clone()),
            ("redirect_uri".to_string(), redirect_uri.to_string()),
        ];
        let response = post_token_form(&http, &token_url, &form).await?;
        let refresh_token = response.refresh_token.clone().ok_or_else(|| {
            Error::new("gantryruntime: authorization-code exchange returned no refresh_token")
        })?;
        let ttl = response.ttl();
        let source = OAuthSource {
            http,
            token_url,
            client_id: self.client_id.clone(),
            client_secret: self.client_secret.clone(),
            store: None,
            state: Mutex::new(OAuthState {
                token: response.access_token,
                expiry: Instant::now() + ttl,
                refresh_token,
                refresh_token_persisted: true,
            }),
        };
        Ok(Auth {
            source: Source::OAuth(source),
        })
    }
}

/// The subset of the token endpoint's JSON response we consume.
struct TokenResponse {
    access_token: String,
    refresh_token: Option<String>,
    expires_in: u64,
}

impl TokenResponse {
    fn ttl(&self) -> Duration {
        Duration::from_secs(self.expires_in)
    }
}

/// POST a form-encoded grant to the token endpoint and decode the response,
/// surfacing a non-2xx body as the error.
async fn post_token_form(
    http: &reqwest::Client,
    token_url: &str,
    form: &[(String, String)],
) -> Result<TokenResponse, Error> {
    let pairs: Vec<(&str, &str)> = form.iter().map(|(k, v)| (k.as_str(), v.as_str())).collect();
    let body = form_urlencode(&pairs);
    let response = http
        .post(token_url)
        .header("Content-Type", "application/x-www-form-urlencoded")
        .header("Accept", "application/json")
        .body(body)
        .send()
        .await?;
    let status = response.status();
    let bytes = response.bytes().await?;
    if !status.is_success() {
        let detail = String::from_utf8_lossy(&bytes);
        return Err(Error::new(format!(
            "gantryruntime: token endpoint returned {}: {}",
            status.as_u16(),
            detail.trim()
        )));
    }
    let json: serde_json::Value = serde_json::from_slice(&bytes)?;
    let access_token = json
        .get("access_token")
        .and_then(|v| v.as_str())
        .map(|s| s.to_string())
        .filter(|s| !s.is_empty())
        .ok_or_else(|| Error::new("gantryruntime: token endpoint returned no access_token"))?;
    Ok(TokenResponse {
        access_token,
        refresh_token: json
            .get("refresh_token")
            .and_then(|v| v.as_str())
            .filter(|s| !s.is_empty())
            .map(|s| s.to_string()),
        expires_in: json.get("expires_in").and_then(|v| v.as_u64()).unwrap_or(0),
    })
}

/// The dedicated auth HTTP client (a shorter timeout than the API client).
fn auth_http_client() -> reqwest::Client {
    reqwest::Client::builder()
        .timeout(Duration::from_secs(30))
        .build()
        .unwrap_or_default()
}

fn default_token_url() -> String {
    DEFAULT_TOKEN_URL.to_string()
}

/// Encode key/value pairs as `application/x-www-form-urlencoded`.
fn form_urlencode(pairs: &[(&str, &str)]) -> String {
    let mut out = String::new();
    for (name, value) in pairs {
        if !out.is_empty() {
            out.push('&');
        }
        percent_encode_into(&mut out, name);
        out.push('=');
        percent_encode_into(&mut out, value);
    }
    out
}

/// Percent-encode into `out` per the `application/x-www-form-urlencoded`
/// unreserved set (spaces become `+`).
fn percent_encode_into(out: &mut String, value: &str) {
    for byte in value.bytes() {
        match byte {
            b'A'..=b'Z' | b'a'..=b'z' | b'0'..=b'9' | b'-' | b'_' | b'.' | b'~' => {
                out.push(byte as char)
            }
            b' ' => out.push('+'),
            _ => out.push_str(&format!("%{byte:02X}")),
        }
    }
}