rustango 0.61.13

//! HMAC-SHA256 signed session cookies for the operator console.
//!
//! Stateless — the cookie carries the principal (`operator_id` + `exp`)
//! and a signature. Server validates the signature on every request;
//! no server-side session table for v1. Trade-offs:
//!
//! * **Idle and absolute expiry** — `exp` is the idle deadline, slid by
//!   each request; `iat` + [`SESSION_TTL_SECS`] is the hard cap.
//! * **No revocation list** — a cookie is valid until `exp`, unless the
//!   operator is deactivated, changes password or logs out. Logout stamps
//!   `sessions_revoked_at`, which ends the operator's sessions on every device.
//! * **Secret rotation invalidates all cookies** — a server restart
//!   with auto-generated secret signs everyone out. With
//!   `RUSTANGO_SESSION_SECRET` set in env, sessions survive restarts.
//!
//! Cookie format:
//!
//! ```text
//! Cookie: rustango_op_session=<base64(payload)>.<base64(hmac_sha256)>
//! payload  = JSON {"oid": <i64>, "exp": <unix_seconds>, "iat": .., "pwf": ..}
//! signature = HMAC-SHA256(secret, payload_base64) [first 32 bytes]
//! ```

use base64::Engine;
use serde::{Deserialize, Serialize};
use subtle::ConstantTimeEq;

// v0.45 (#253) — `SessionSecret` + `sign` were promoted to the
// crate-root `crate::session` module so the bare `admin` module can
// reuse the same HMAC primitives without compiling in `tenancy`.
// The re-exports below keep every pre-existing `crate::tenancy::session::SessionSecret`
// caller working.
pub use crate::session::{PasswordFingerprint, SessionSecret, SessionSecretError};
// `sign` re-exported at crate-internal visibility so existing
// callers (`tenant_console`, `impersonation_handoff`) keep working
// after the v0.45 move to `crate::session`.
pub(crate) use crate::session::{session_survives, sign};

/// Default cookie name. Visible in browser devtools — namespaced so
/// it doesn't collide with tenant cookies.
pub const COOKIE_NAME: &str = "rustango_op_session";

/// Longest a console session lasts from sign-in, however active.
pub const SESSION_TTL_SECS: i64 = 12 * 60 * 60;

/// A console session unused this long ends; each request slides `exp`.
pub const SESSION_IDLE_SECS: i64 = 30 * 60;

/// How stale `exp` must be before a request re-issues the cookie.
const RENEW_AFTER_SECS: i64 = 60;

/// The tenant session key as the server loads it: the env var, or off the
/// prod tier the dev key file. Never a random key, so a CLI and the server agree.
pub(crate) fn tenant_secret_from_env() -> Result<SessionSecret, super::TenancyError> {
    use crate::session::{is_prod_tier, tier_from_env};
    if is_prod_tier(&tier_from_env()) {
        SessionSecret::require_from_env()
            .map_err(|e| super::TenancyError::Validation(e.to_string()))
    } else {
        Ok(SessionSecret::from_env_or_disk(std::path::Path::new(
            crate::session::TENANT_SESSION_KEY_PATH,
        )))
    }
}

/// The keys a tenancy server signs with: one per console, each from the env
/// var or, off prod, its dev key file. The CLI reads the same tenant file.
pub(crate) struct ServerKeys {
    pub(crate) tenant: SessionSecret,
    pub(crate) operator: SessionSecret,
}

impl ServerKeys {
    /// Panics on the prod tier without a valid `RUSTANGO_SESSION_SECRET`.
    pub(crate) fn load() -> Self {
        let tier = crate::session::tier_from_env();
        Self::from_files(|p| crate::session::load_session_secret_for_tier(&tier, p))
    }

    /// Each key from its dev file path, through `load`.
    fn from_files(load: impl Fn(&std::path::Path) -> SessionSecret) -> Self {
        use crate::session::{OPERATOR_SESSION_KEY_PATH, TENANT_SESSION_KEY_PATH};
        Self {
            tenant: load(std::path::Path::new(TENANT_SESSION_KEY_PATH)),
            operator: load(std::path::Path::new(OPERATOR_SESSION_KEY_PATH)),
        }
    }

    /// Off prod, under `root`, with the env value passed in.
    #[cfg(test)]
    fn dev_at(env: Option<&str>, root: &std::path::Path) -> Self {
        Self::from_files(|p| SessionSecret::from_raw_or_disk(env, &root.join(p)))
    }
}

/// Where [`existing_tenant_secret`] found the key.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum KeySource {
    Env,
    /// The dev key file: only a server reading the same file shares it.
    DevFile,
}

/// What a CLI does when the dev key file is missing.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum DevKeyFile {
    /// Refuse: API keys minted now must verify on a server already running.
    LoadOnly,
    /// Write it as a server's first boot does, so a fresh dev project works.
    LoadOrCreate,
}

/// The tenant session key the server loads: the env var, or off prod the dev
/// key file. Never a key only this process holds.
pub(crate) fn existing_tenant_secret(
    dev_key: DevKeyFile,
) -> Result<(SessionSecret, KeySource), super::TenancyError> {
    use crate::session::{is_prod_tier, tier_from_env};
    existing_tenant_secret_at(
        std::env::var("RUSTANGO_SESSION_SECRET").ok().as_deref(),
        is_prod_tier(&tier_from_env()),
        std::path::Path::new(crate::session::TENANT_SESSION_KEY_PATH),
        dev_key,
    )
}

fn existing_tenant_secret_at(
    env: Option<&str>,
    prod: bool,
    dev_file: &std::path::Path,
    dev_key: DevKeyFile,
) -> Result<(SessionSecret, KeySource), super::TenancyError> {
    let invalid =
        |e: crate::session::SessionSecretError| super::TenancyError::Validation(e.to_string());
    if prod {
        return env
            .ok_or(crate::session::SessionSecretError::Missing)
            .and_then(SessionSecret::from_b64)
            .map(|s| (s, KeySource::Env))
            .map_err(invalid);
    }
    // Off prod the server falls back to the dev file on a bad env value; match it.
    if let Some(raw) = env {
        match SessionSecret::from_b64(raw) {
            Ok(s) => return Ok((s, KeySource::Env)),
            Err(e) => crate::session::warn_unusable_secret(&e.to_string()),
        }
    }
    let missing = |fix: String| {
        super::TenancyError::Validation(format!(
            "no tenant session key: set RUSTANGO_SESSION_SECRET, or {fix}"
        ))
    };
    match dev_key {
        DevKeyFile::LoadOnly => match std::fs::read(dev_file) {
            Ok(bytes) if bytes.len() >= 32 => {
                Ok((SessionSecret::from_bytes(bytes), KeySource::DevFile))
            }
            _ => Err(missing(format!(
                "start the server once so it writes {}",
                dev_file.display()
            ))),
        },
        // A failed write is an error: a random fallback is a key no server holds.
        DevKeyFile::LoadOrCreate => crate::session::load_or_create_key_file(
            dev_file,
            "session secret",
            "RUSTANGO_SESSION_SECRET",
        )
        .map(|bytes| (SessionSecret::from_bytes(bytes), KeySource::DevFile))
        .map_err(|e| {
            missing(format!(
                "fix the dev key file: cannot read or write {} ({e})",
                dev_file.display()
            ))
        }),
    }
}

#[derive(Debug, thiserror::Error)]
pub enum SessionError {
    #[error("session cookie is malformed")]
    Malformed,
    #[error("session signature mismatch")]
    BadSignature,
    #[error("session expired")]
    Expired,
    /// Cookie's tenant slug doesn't match the resolved tenant — used
    /// by the tenant console to defend against cross-tenant cookie
    /// replay (cookie issued for `acme` should not authenticate at
    /// `globex`'s subdomain).
    #[error("session is bound to a different tenant")]
    WrongTenant,
}

/// Principal payload carried inside the cookie. Compact field names
/// to keep the cookie short (browsers truncate aggressively).
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub struct SessionPayload {
    /// Operator id (from `rustango_operators.id`).
    pub oid: i64,
    /// Expiry as Unix seconds.
    pub exp: i64,
    /// Issued-at as Unix seconds. A session issued before
    /// `rustango_operators.password_changed_at` is rejected. `0` for
    /// cookies minted on pre-0.28.4 servers.
    #[serde(default)]
    pub iat: i64,
    /// Fingerprint of the operator's `password_hash` at login. Any
    /// password change makes it stop matching (#1338).
    #[serde(default)]
    pub pwf: PasswordFingerprint,
}

impl SessionPayload {
    /// `pwf` is the [`PasswordFingerprint`] of the operator's current hash.
    #[must_use]
    pub fn new(operator_id: i64, ttl_secs: i64, pwf: PasswordFingerprint) -> Self {
        let now = chrono::Utc::now().timestamp();
        Self {
            oid: operator_id,
            exp: now + ttl_secs,
            iat: now,
            pwf,
        }
    }

    /// Past the idle deadline `exp`, or [`SESSION_TTL_SECS`] after sign-in.
    fn is_expired(&self) -> bool {
        let now = chrono::Utc::now().timestamp();
        now >= self.exp || now >= self.iat.saturating_add(SESSION_TTL_SECS)
    }

    /// This session with its idle deadline moved to now + [`SESSION_IDLE_SECS`],
    /// capped at the absolute lifetime. `None` while `exp` is still fresh.
    #[must_use]
    pub fn renewed(&self) -> Option<Self> {
        let now = chrono::Utc::now().timestamp();
        let exp = (now + SESSION_IDLE_SECS).min(self.iat.saturating_add(SESSION_TTL_SECS));
        // An older cookie's far `exp` is pulled in, too.
        (exp < self.exp || exp - self.exp >= RENEW_AFTER_SECS).then(|| Self {
            exp,
            ..self.clone()
        })
    }
}

/// Serialize and sign a payload into a cookie value.
#[must_use]
pub fn encode(secret: &SessionSecret, payload: &SessionPayload) -> String {
    let json = serde_json::to_vec(payload).expect("payload serializes");
    let payload_b64 = base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(json);
    let sig = sign(secret, payload_b64.as_bytes());
    let sig_b64 = base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(sig);
    format!("{payload_b64}.{sig_b64}")
}

/// Verify and deserialize a cookie value.
///
/// # Errors
/// Returns [`SessionError::Malformed`] for missing/bad-base64 parts,
/// [`SessionError::BadSignature`] when HMAC doesn't match (covers
/// secret rotation + tampering), [`SessionError::Expired`] when the
/// payload's `exp` is in the past.
pub fn decode(secret: &SessionSecret, value: &str) -> Result<SessionPayload, SessionError> {
    let (payload_b64, sig_b64) = value.split_once('.').ok_or(SessionError::Malformed)?;
    let expected = sign(secret, payload_b64.as_bytes());
    let provided = base64::engine::general_purpose::URL_SAFE_NO_PAD
        .decode(sig_b64)
        .map_err(|_| SessionError::Malformed)?;
    if expected.ct_eq(&provided[..]).unwrap_u8() == 0 {
        return Err(SessionError::BadSignature);
    }
    let payload_bytes = base64::engine::general_purpose::URL_SAFE_NO_PAD
        .decode(payload_b64)
        .map_err(|_| SessionError::Malformed)?;
    let payload: SessionPayload =
        serde_json::from_slice(&payload_bytes).map_err(|_| SessionError::Malformed)?;
    if payload.is_expired() {
        return Err(SessionError::Expired);
    }
    Ok(payload)
}

// `sign` moved to `crate::session` in v0.45 (#253) — `use` above.

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

    fn fp() -> PasswordFingerprint {
        PasswordFingerprint::default()
    }

    /// Off prod a fresh project gets the dev key file the server would write,
    /// and keeps it; on prod nothing is written.
    #[test]
    fn off_prod_the_dev_key_file_is_created_once() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("var").join("tenant.key");
        assert!(existing_tenant_secret_at(None, true, &path, DevKeyFile::LoadOrCreate).is_err());
        assert!(!path.exists(), "prod wrote a key file");
        let (first, source) =
            existing_tenant_secret_at(None, false, &path, DevKeyFile::LoadOrCreate).unwrap();
        assert_eq!(source, KeySource::DevFile);
        assert_eq!(std::fs::read(&path).unwrap(), first.key());
        // The env value is passed in: the caller's own secret must not decide this.
        let server = SessionSecret::from_raw_or_disk(None, &path);
        assert_eq!(
            server.key(),
            first.key(),
            "the server must load the same key"
        );
        let (again, _) =
            existing_tenant_secret_at(None, false, &path, DevKeyFile::LoadOrCreate).unwrap();
        assert_eq!(again.key(), first.key());
    }

    /// A set-password link the CLI signs with the tenant key verifies under
    /// the key a tenancy server (run-server or `server::Builder`) loads.
    #[test]
    fn a_cli_link_verifies_under_the_servers_tenant_key() {
        let root = tempfile::tempdir().unwrap();
        let file = root.path().join(crate::session::TENANT_SESSION_KEY_PATH);
        let (cli, _) =
            existing_tenant_secret_at(None, false, &file, DevKeyFile::LoadOrCreate).unwrap();
        let server = ServerKeys::dev_at(None, root.path());
        let scope = crate::auth_flows::LinkScope::from(&crate::testkit::org());
        let link = crate::auth_flows::PasswordReset::issue(
            &scope,
            "/change-password",
            42,
            &super::super::first_admin::link_key(&cli),
            std::time::Duration::from_secs(60),
        );
        let key = super::super::first_admin::link_key(&server.tenant);
        assert_eq!(
            crate::auth_flows::PasswordReset::verify(&scope, &link, &key),
            Ok(42)
        );
        assert_ne!(
            server.operator.key(),
            server.tenant.key(),
            "one key per console"
        );
    }

    /// Off prod an unusable env secret falls back to the dev file, as the server does.
    #[test]
    fn an_unusable_env_secret_uses_the_servers_dev_file() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("tenant.key");
        std::fs::write(&path, [7u8; 32]).unwrap();
        let (_, source) =
            existing_tenant_secret_at(Some("not-base64!"), false, &path, DevKeyFile::LoadOnly)
                .unwrap();
        assert_eq!(source, KeySource::DevFile);
        assert!(
            existing_tenant_secret_at(Some("not-base64!"), true, &path, DevKeyFile::LoadOnly)
                .is_err()
        );
        let good = "A".repeat(44);
        let (_, source) =
            existing_tenant_secret_at(Some(&good), false, &path, DevKeyFile::LoadOnly).unwrap();
        assert_eq!(source, KeySource::Env);
    }

    #[test]
    fn round_trip_valid_payload() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let payload = SessionPayload::new(42, 3600, PasswordFingerprint::of(&secret, "$h"));
        let cookie = encode(&secret, &payload);
        let back = decode(&secret, &cookie).unwrap();
        assert_eq!(back, payload);
    }

    #[test]
    fn rejects_tampered_payload() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let payload = SessionPayload::new(42, 3600, fp());
        let cookie = encode(&secret, &payload);
        // Replace payload but keep signature → BadSignature.
        let (_, sig) = cookie.split_once('.').unwrap();
        let evil_payload = base64::engine::general_purpose::URL_SAFE_NO_PAD
            .encode(br#"{"oid":999,"exp":9999999999}"#);
        let tampered = format!("{evil_payload}.{sig}");
        let err = decode(&secret, &tampered).unwrap_err();
        assert!(matches!(err, SessionError::BadSignature));
    }

    #[test]
    fn rejects_wrong_secret() {
        let s1 = SessionSecret::from_bytes(b"first-test-secret-thirty-2-bytes".to_vec());
        let s2 = SessionSecret::from_bytes(b"second-test-secret-thirty2-bytes".to_vec());
        let cookie = encode(&s1, &SessionPayload::new(1, 3600, fp()));
        let err = decode(&s2, &cookie).unwrap_err();
        assert!(matches!(err, SessionError::BadSignature));
    }

    #[test]
    fn rejects_expired() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let payload = SessionPayload::new(1, -10, fp());
        let cookie = encode(&secret, &payload);
        let err = decode(&secret, &cookie).unwrap_err();
        assert!(matches!(err, SessionError::Expired));
    }

    /// Renewal slides `exp` to the idle window, never past the cap.
    #[test]
    fn renewal_slides_exp_up_to_the_cap() {
        let now = chrono::Utc::now().timestamp();
        let renewed = SessionPayload::new(1, 30, fp()).renewed().expect("stale");
        assert!(renewed.exp >= now + SESSION_IDLE_SECS);
        assert!(renewed.renewed().is_none(), "fresh needs no new cookie");

        let mut near_cap = SessionPayload::new(1, 30, fp());
        near_cap.iat = now - SESSION_TTL_SECS + 10;
        assert!(near_cap.renewed().unwrap().exp <= now + 10);

        // An older week-long cookie is cut to the idle limit.
        let old = SessionPayload::new(1, 7 * 24 * 3600, fp());
        let cut = old.renewed().expect("a far exp is pulled in");
        assert!(cut.exp <= chrono::Utc::now().timestamp() + SESSION_IDLE_SECS);
    }

    /// A session older than the absolute cap is refused, whatever its `exp`.
    #[test]
    fn rejects_a_session_past_the_absolute_cap() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let mut payload = SessionPayload::new(1, 3600, fp());
        payload.iat -= SESSION_TTL_SECS;
        let err = decode(&secret, &encode(&secret, &payload)).unwrap_err();
        assert!(matches!(err, SessionError::Expired));
    }

    #[test]
    fn rejects_malformed_no_dot() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let err = decode(&secret, "not-a-cookie").unwrap_err();
        assert!(matches!(err, SessionError::Malformed));
    }

    /// A new hash ends the session even when `iat` equals the change second.
    #[test]
    fn a_new_password_hash_ends_a_same_second_session() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let now = chrono::Utc::now();
        let pwf = PasswordFingerprint::of(&secret, "$old");
        assert!(session_survives(
            &secret,
            &pwf,
            now.timestamp(),
            "$old",
            Some(now),
            None
        ));
        assert!(!session_survives(
            &secret,
            &pwf,
            now.timestamp(),
            "$new",
            Some(now),
            None
        ));
        // A cookie from before this field decodes empty and never matches.
        assert!(!session_survives(
            &secret,
            &fp(),
            now.timestamp(),
            "$old",
            None,
            None
        ));
    }

    /// With the hash unchanged, a `password_changed_at` bump after `iat` still ends it.
    #[test]
    fn a_later_password_changed_at_ends_a_session_with_the_same_hash() {
        let secret = SessionSecret::from_bytes(b"a-test-secret-thirty-two-bytes-x".to_vec());
        let pwf = PasswordFingerprint::of(&secret, "$h");
        let iat = 1_700_000_000;
        let at = |secs| chrono::DateTime::from_timestamp(secs, 0);
        assert!(session_survives(&secret, &pwf, iat, "$h", None, None));
        assert!(session_survives(&secret, &pwf, iat, "$h", at(iat), None));
        assert!(!session_survives(
            &secret,
            &pwf,
            iat,
            "$h",
            at(iat + 1),
            None
        ));
    }
}