stack_auth/

lib.rs

#![doc(html_favicon_url = "https://cipherstash.com/favicon.ico")]
#![doc = include_str!("../README.md")]
// Security lints
#![deny(unsafe_code)]
#![warn(clippy::unwrap_used)]
#![warn(clippy::expect_used)]
#![warn(clippy::panic)]
// Prevent mem::forget from bypassing ZeroizeOnDrop
#![warn(clippy::mem_forget)]
// Prevent accidental data leaks via output
#![warn(clippy::print_stdout)]
#![warn(clippy::print_stderr)]
#![warn(clippy::dbg_macro)]
// Code quality
#![warn(unreachable_pub)]
#![warn(unused_results)]
#![warn(clippy::todo)]
#![warn(clippy::unimplemented)]
// Relax in tests
#![cfg_attr(test, allow(clippy::unwrap_used))]
#![cfg_attr(test, allow(clippy::expect_used))]
#![cfg_attr(test, allow(clippy::panic))]
#![cfg_attr(test, allow(unused_results))]

use std::convert::Infallible;
use std::future::Future;
#[cfg(all(not(any(test, feature = "test-utils")), not(target_arch = "wasm32")))]
use std::time::Duration;

use vitaminc::protected::OpaqueDebug;
use zeroize::ZeroizeOnDrop;

mod access_key;
mod access_key_refresher;
mod access_key_strategy;
mod auth_strategy_fn;
mod auto_refresh;
mod auto_strategy;
mod oauth_refresher;
mod oauth_strategy;
mod refresher;
mod service_token;
mod token;
mod token_store;

// Filesystem-backed device identity and the interactive device-code flow are
// native-only — both pull `stack-profile` (which uses `dirs` + `gethostname`)
// and the device-code flow launches a browser via `open::that`. Wasm consumers
// use `OAuthStrategy::with_token` or `AccessKeyStrategy`.
#[cfg(not(target_arch = "wasm32"))]
mod device_client;
#[cfg(not(target_arch = "wasm32"))]
mod device_code;

#[cfg(any(test, feature = "test-utils"))]
mod static_token_strategy;

pub use access_key::{AccessKey, InvalidAccessKey};
pub use access_key_strategy::{AccessKeyStrategy, AccessKeyStrategyBuilder};
pub use auth_strategy_fn::AuthStrategyFn;
pub use auto_strategy::{AutoStrategy, AutoStrategyBuilder};
pub use oauth_strategy::{OAuthStrategy, OAuthStrategyBuilder};
pub use service_token::ServiceToken;
#[cfg(any(test, feature = "test-utils"))]
pub use static_token_strategy::StaticTokenStrategy;
pub use token::Token;
pub use token_store::{InMemoryTokenStore, NoStore, TokenStore, TokenStoreFn};

#[cfg(not(target_arch = "wasm32"))]
pub use device_client::{bind_client_device, DeviceClientError};
#[cfg(not(target_arch = "wasm32"))]
pub use device_code::{DeviceCodeStrategy, DeviceCodeStrategyBuilder, PendingDeviceCode};

// Re-exports from stack-profile for backward compatibility.
#[cfg(not(target_arch = "wasm32"))]
pub use stack_profile::DeviceIdentity;

/// Token *acquisition* — strategies that produce a [`ServiceToken`].
///
/// Use [`AuthStrategy`] as the consumer-facing trait (e.g. when wiring
/// strategies into `cipherstash-client`). [`AuthStrategyFn`] is the
/// closure-shaped impl for callers that source tokens externally
/// (FFI, custom IPC).
///
/// For the *persistence layer* — pluggable storage that slots into an
/// existing strategy — see [`crate::store`].
///
/// All items in this module are also re-exported at the crate root.
pub mod auth {
    pub use crate::{
        AccessKey, AccessKeyStrategy, AccessKeyStrategyBuilder, AuthError, AuthStrategy,
        AuthStrategyBounds, AuthStrategyFn, AutoStrategy, AutoStrategyBuilder, InvalidAccessKey,
        OAuthStrategy, OAuthStrategyBuilder, SecretToken, ServiceToken,
    };

    #[cfg(not(target_arch = "wasm32"))]
    pub use crate::{
        bind_client_device, DeviceClientError, DeviceCodeStrategy, DeviceCodeStrategyBuilder,
        DeviceIdentity, PendingDeviceCode,
    };

    #[cfg(any(test, feature = "test-utils"))]
    pub use crate::StaticTokenStrategy;
}

/// Token *persistence* — pluggable backends for the service-token cache.
///
/// Use [`TokenStore`] as the trait, [`TokenStoreFn`] for closure-shaped
/// impls (cookies, KV blobs, Redis), and [`InMemoryTokenStore`] / [`NoStore`]
/// for ready-made implementations.
///
/// A `TokenStore` plugs into a concrete strategy via that strategy's
/// builder (e.g.
/// [`AccessKeyStrategyBuilder::with_token_store`](crate::AccessKeyStrategyBuilder::with_token_store))
/// — it does *not* replace the strategy. For full token acquisition (custom
/// fetcher, FFI-hosted strategy), see [`crate::auth`].
///
/// All items in this module are also re-exported at the crate root.
pub mod store {
    pub use crate::{InMemoryTokenStore, NoStore, Token, TokenStore, TokenStoreFn};
}

/// A strategy for obtaining access tokens.
///
/// Implementations handle all details of authentication, token caching, and
/// refresh. Callers just call [`get_token`](AuthStrategy::get_token) whenever
/// they need a valid token.
///
/// The trait is designed to be implemented for `&T`, so that callers can use
/// shared references (e.g. `&OAuthStrategy`) without consuming the strategy.
///
/// # Token refresh
///
/// All strategies that cache tokens ([`AccessKeyStrategy`], [`OAuthStrategy`],
/// [`AutoStrategy`]) share the same internal refresh engine. Understanding the
/// refresh model helps predict how [`get_token`](AuthStrategy::get_token)
/// behaves under concurrent access.
///
/// ## Expiry vs usability
///
/// A token has two time thresholds:
///
/// - **Expired** — the token is within **90 seconds** of its `expires_at`
///   timestamp. This triggers a preemptive refresh attempt.
/// - **Usable** — the token has **not yet reached** its `expires_at` timestamp.
///   A token can be "expired" (in the preemptive sense) but still "usable"
///   (the server will still accept it).
///
/// ## Concurrent refresh strategies
///
/// The gap between "expired" and "unusable" enables two refresh modes:
///
/// 1. **Expiring but still usable** — The first caller triggers a background
///    refresh. Concurrent callers receive the current (still-valid) token
///    immediately without blocking.
/// 2. **Fully expired** — The first caller blocks while refreshing. Concurrent
///    callers wait until the refresh completes, then all receive the new token.
///
/// Only one refresh runs at a time, regardless of how many callers request a
/// token concurrently.
///
/// ## Flow diagram
///
/// ```mermaid
/// flowchart TD
///     Start["get_token()"] --> Lock["Acquire lock"]
///     Lock --> Cached{Token cached?}
///     Cached -- No --> InitAuth["Authenticate
///     (lock held)"]
///     InitAuth -- OK --> ReturnNew["Return new token"]
///     InitAuth -- NotFound --> ErrNotFound["NotAuthenticated"]
///     InitAuth -- Err --> ErrAuth["Return error"]
///     Cached -- Yes --> CheckRefresh{Expired?}
///
///     CheckRefresh -- "No (fresh)" --> ReturnOk["Return cached token"]
///
///     CheckRefresh -- "Yes (needs refresh)" --> InProgress{Refresh in progress?}
///     InProgress -- Yes --> WaitOrReturn["Return token if usable,
///     else wait for refresh"]
///     WaitOrReturn -- OK --> ReturnOk
///     WaitOrReturn -- "refresh failed" --> ErrExpired["TokenExpired"]
///
///     InProgress -- No --> HasCred{Refresh credential?}
///     HasCred -- None --> CheckUsable["Return token if usable,
///     else TokenExpired"]
///
///     HasCred -- Yes --> Usable{Still usable?}
///
///     Usable -- "Yes (preemptive)" --> NonBlocking["Refresh in background
///     (lock released)"]
///     NonBlocking --> ReturnOld["Return current token"]
///
///     Usable -- "No (fully expired)" --> Blocking["Refresh
///     (lock held)"]
///     Blocking -- OK --> ReturnNew2["Return new token"]
///     Blocking -- Err --> ErrExpired["TokenExpired"]
/// ```
#[cfg_attr(doc, aquamarine::aquamarine)]
#[cfg(not(target_arch = "wasm32"))]
pub trait AuthStrategy: Send {
    /// Retrieve a valid access token, refreshing or re-authenticating as needed.
    fn get_token(self) -> impl Future<Output = Result<ServiceToken, AuthError>> + Send;
}

/// Wasm32 variant of [`AuthStrategy`] — drops the `Send` bounds because
/// reqwest's fetch-backed futures aren't `Send` and edge runtimes are
/// single-threaded.
#[cfg(target_arch = "wasm32")]
pub trait AuthStrategy {
    /// Retrieve a valid access token, refreshing or re-authenticating as needed.
    fn get_token(self) -> impl Future<Output = Result<ServiceToken, AuthError>>;
}

/// Marker trait alias for the bounds an owned `AuthStrategy`-providing
/// credential type `C` must satisfy when held inside a long-lived client
/// (e.g. `cipherstash_client::ZeroKMS<C>` shared across requests).
///
/// - On native targets `C` must be `Send + Sync + 'static` so the client
///   can be carried across tokio task / `reqwest` worker boundaries.
/// - On `wasm32` the runtime is single-threaded and the typical credential
///   backing (a JS callable held by a `JsValue`) cannot cross threads
///   even in principle, so the `Send + Sync` requirement is dropped and
///   only `'static` remains.
///
/// Implemented via a blanket impl — any type satisfying the per-target
/// bounds automatically implements `AuthStrategyBounds`. Callers don't
/// implement it directly.
///
/// Mirrors the `cfg`-split already in place on [`AuthStrategy`] itself,
/// one layer up. Wasm consumers (e.g. `@cipherstash/protect-ffi` on
/// `wasm32-unknown-unknown`) can hold a `!Send + !Sync` credential type
/// without declaring `unsafe impl Send` / `Sync`.
#[cfg(not(target_arch = "wasm32"))]
pub trait AuthStrategyBounds: Send + Sync + 'static {}
#[cfg(not(target_arch = "wasm32"))]
impl<T: Send + Sync + 'static> AuthStrategyBounds for T {}

#[cfg(target_arch = "wasm32")]
pub trait AuthStrategyBounds: 'static {}
#[cfg(target_arch = "wasm32")]
impl<T: 'static> AuthStrategyBounds for T {}

/// A sensitive token string that is zeroized on drop and hidden from debug output.
///
/// `SecretToken` wraps a `String` and enforces two invariants:
///
/// - **Zeroized on drop**: the backing memory is overwritten with zeros when
///   the token goes out of scope, preventing it from lingering in memory.
/// - **Opaque debug**: the [`Debug`] implementation prints `"***"` instead of
///   the actual value, so tokens won't leak into logs or error messages.
///
/// Use [`SecretToken::new`] to wrap a string value (e.g. an access key
/// loaded from configuration or an environment variable).
#[derive(Clone, OpaqueDebug, ZeroizeOnDrop, serde::Deserialize, serde::Serialize)]
#[serde(transparent)]
pub struct SecretToken(String);

impl SecretToken {
    /// Create a new `SecretToken` from a string value.
    pub fn new(value: impl Into<String>) -> Self {
        Self(value.into())
    }

    /// Expose the inner token string for FFI boundaries.
    pub fn as_str(&self) -> &str {
        &self.0
    }
}

/// Errors that can occur during an authentication flow.
#[derive(Debug, thiserror::Error, miette::Diagnostic)]
#[non_exhaustive]
pub enum AuthError {
    /// The HTTP request to the auth server failed (network error, timeout, etc.).
    #[error("HTTP request failed: {0}")]
    Request(#[from] reqwest::Error),
    /// The user denied the authorization request.
    #[error("Authorization was denied")]
    AccessDenied,
    /// The grant type was rejected by the server.
    #[error("Invalid grant")]
    InvalidGrant,
    /// The client ID is not recognized.
    #[error("Invalid client")]
    InvalidClient,
    /// A URL could not be parsed.
    #[error("Invalid URL: {0}")]
    InvalidUrl(#[from] url::ParseError),
    /// The requested region is not supported.
    #[error("Unsupported region: {0}")]
    Region(#[from] cts_common::RegionError),
    /// The workspace CRN could not be parsed.
    #[error("Invalid workspace CRN: {0}")]
    InvalidCrn(cts_common::InvalidCrn),
    /// The token issued by the auth server is for a different workspace than
    /// the one configured on the strategy. Surfaces when the access key was
    /// minted for a different workspace, or when the wrong CRN was passed.
    #[error("Workspace mismatch: token issued for {token_workspace}, but strategy is configured for {expected_workspace}")]
    WorkspaceMismatch {
        /// The workspace the strategy was configured for (from the CRN).
        expected_workspace: cts_common::WorkspaceId,
        /// The workspace the auth server's token actually carries.
        token_workspace: cts_common::WorkspaceId,
    },
    /// An access key was provided but the workspace CRN is missing.
    ///
    /// Set the `CS_WORKSPACE_CRN` environment variable or call
    /// [`AutoStrategyBuilder::with_workspace_crn`](crate::AutoStrategyBuilder::with_workspace_crn).
    #[error("Workspace CRN is required when using an access key — set CS_WORKSPACE_CRN or call AutoStrategyBuilder::with_workspace_crn")]
    MissingWorkspaceCrn,
    /// No credentials are available (e.g. not logged in, no access key configured).
    #[error("Not authenticated")]
    NotAuthenticated,
    /// A token (access token or device code) has expired.
    #[error("Token expired")]
    TokenExpired,
    /// The access key string is malformed (e.g. missing `CSAK` prefix or `.` separator).
    #[error("Invalid access key: {0}")]
    InvalidAccessKey(#[from] access_key::InvalidAccessKey),
    /// The JWT could not be decoded or its claims are malformed.
    #[error("Invalid token: {0}")]
    InvalidToken(String),
    /// An unexpected error was returned by the auth server.
    #[error("Server error: {0}")]
    Server(String),
    /// A token store operation failed.
    #[cfg(not(target_arch = "wasm32"))]
    #[error("Token store error: {0}")]
    Store(#[from] stack_profile::ProfileError),
}

impl AuthError {
    /// Stable machine-readable identifier for surfacing across FFI boundaries
    /// (e.g. JS `Error.code`, Node-API error codes). Named `error_code` rather
    /// than `code` to avoid colliding with `miette::Diagnostic::code`, which
    /// is inherited via `#[derive(Diagnostic)]`.
    pub fn error_code(&self) -> &'static str {
        match self {
            Self::Request(_) => "REQUEST_ERROR",
            Self::AccessDenied => "ACCESS_DENIED",
            Self::TokenExpired => "EXPIRED_TOKEN",
            Self::InvalidGrant => "INVALID_GRANT",
            Self::InvalidClient => "INVALID_CLIENT",
            Self::InvalidUrl(_) => "INVALID_URL",
            Self::Region(_) => "INVALID_REGION",
            Self::InvalidToken(_) => "INVALID_TOKEN",
            Self::Server(_) => "SERVER_ERROR",
            Self::NotAuthenticated => "NOT_AUTHENTICATED",
            Self::MissingWorkspaceCrn => "MISSING_WORKSPACE_CRN",
            Self::InvalidAccessKey(_) => "INVALID_ACCESS_KEY",
            Self::InvalidCrn(_) => "INVALID_CRN",
            Self::WorkspaceMismatch { .. } => "WORKSPACE_MISMATCH",
            #[cfg(not(target_arch = "wasm32"))]
            Self::Store(_) => "STORE_ERROR",
        }
    }
}

impl From<Infallible> for AuthError {
    fn from(never: Infallible) -> Self {
        match never {}
    }
}

/// Read the `CS_CTS_HOST` environment variable and parse it as a URL.
///
/// Returns `Ok(None)` if the variable is not set or empty.
/// Returns `Ok(Some(url))` if the variable is set and valid.
/// Returns `Err(_)` if the variable is set but not a valid URL.
pub(crate) fn cts_base_url_from_env() -> Result<Option<url::Url>, AuthError> {
    match std::env::var("CS_CTS_HOST") {
        Ok(val) if !val.is_empty() => Ok(Some(val.parse()?)),
        _ => Ok(None),
    }
}

/// Ensure a URL has a trailing slash so that `Url::join` with relative paths
/// appends to the path rather than replacing the last segment.
pub(crate) fn ensure_trailing_slash(mut url: url::Url) -> url::Url {
    if !url.path().ends_with('/') {
        url.set_path(&format!("{}/", url.path()));
    }
    url
}

/// Decode a JWT payload by splitting on `.`, base64-decoding the middle
/// segment, and deserializing the JSON. Used on wasm32 to avoid `jsonwebtoken`
/// (which pulls `ring`). Signatures are not verified — same posture as the
/// native path, which calls `insecure_disable_signature_validation()`.
#[cfg(target_arch = "wasm32")]
pub(crate) fn decode_jwt_payload_wasm<C>(token: &str) -> Result<C, AuthError>
where
    C: serde::de::DeserializeOwned,
{
    use base64::Engine;
    let segments: Vec<&str> = token.split('.').collect();
    if segments.len() != 3 {
        return Err(AuthError::InvalidToken(
            "JWT must have three segments".to_string(),
        ));
    }
    let payload = base64::engine::general_purpose::URL_SAFE_NO_PAD
        .decode(segments[1])
        .map_err(|e| AuthError::InvalidToken(format!("base64 decode failed: {e}")))?;
    serde_json::from_slice(&payload)
        .map_err(|e| AuthError::InvalidToken(format!("failed to decode JWT claims: {e}")))
}

/// Create a [`reqwest::Client`] with standard timeouts.
///
/// In test builds, timeouts are omitted so that `tokio::test(start_paused = true)`
/// does not auto-advance time past the connect timeout before the mock server
/// can respond. On wasm32, reqwest's fetch backend doesn't expose
/// `connect_timeout`/`pool_*` — the host runtime owns those concerns.
#[cfg(any(test, feature = "test-utils"))]
pub(crate) fn http_client() -> reqwest::Client {
    reqwest::Client::builder()
        .build()
        .unwrap_or_else(|_| reqwest::Client::new())
}

#[cfg(all(not(any(test, feature = "test-utils")), not(target_arch = "wasm32")))]
pub(crate) fn http_client() -> reqwest::Client {
    reqwest::Client::builder()
        .connect_timeout(Duration::from_secs(10))
        .timeout(Duration::from_secs(30))
        .pool_idle_timeout(Duration::from_secs(5))
        .pool_max_idle_per_host(10)
        .build()
        .unwrap_or_else(|_| reqwest::Client::new())
}

#[cfg(all(not(any(test, feature = "test-utils")), target_arch = "wasm32"))]
pub(crate) fn http_client() -> reqwest::Client {
    // Wasm32 reqwest uses the host's `fetch`; timeouts and pooling are owned
    // by the runtime, so `ClientBuilder` doesn't expose them here.
    reqwest::Client::builder()
        .build()
        .unwrap_or_else(|_| reqwest::Client::new())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn auth_error_code_known_variants() {
        assert_eq!(AuthError::AccessDenied.error_code(), "ACCESS_DENIED");
        assert_eq!(AuthError::TokenExpired.error_code(), "EXPIRED_TOKEN");
        assert_eq!(AuthError::InvalidGrant.error_code(), "INVALID_GRANT");
        assert_eq!(AuthError::InvalidClient.error_code(), "INVALID_CLIENT");
        assert_eq!(
            AuthError::NotAuthenticated.error_code(),
            "NOT_AUTHENTICATED"
        );
        assert_eq!(
            AuthError::MissingWorkspaceCrn.error_code(),
            "MISSING_WORKSPACE_CRN"
        );
        assert_eq!(AuthError::Server("x".into()).error_code(), "SERVER_ERROR");
        assert_eq!(
            AuthError::InvalidToken("malformed".into()).error_code(),
            "INVALID_TOKEN"
        );
    }
}