auth: logging in by key

POST /auth/challenge and /auth/login/key: a node-signed challenge,
valid five minutes and taken once, signed with one of the user's SSH
keys (ssh-keygen -Y sign -n continuum-login), for a token.

Auth plan M7 (key login, M2b).

2 files changed, 101 insertions, 7 deletions

diff --git a/src/api/login.rs b/src/api/login.rs
index 72a4d9d..75d6982 100644
--- a/src/api/login.rs
+++ b/src/api/login.rs
@@ -5,6 +5,9 @@
 //!   a token, signed by this node, valid for `--token-lifetime`, refreshable until
 //!   `--session-lifetime` after the login. Optionally less than the user may do
 //!   (`{"limit": [{"path": [...], "rights": [...]}, …]}`).
+//! * `POST /auth/challenge` and `POST /auth/login/key`, without a password: a challenge
+//!   to sign with one of the user's keys, then the same token for it, signed
+//!   (`access::challenge`).
 //! * `POST /auth/refresh`, with a token: a new one for the same login, signed by this
 //!   node, optionally narrower still (`limit`, within the token's).
 //! * `POST /auth/logout`: every token of the user, of every login, no longer taken
@@ -32,7 +35,8 @@ use super::auth::{AuthenticatedUser, Via};
 use super::users::CapRequest;
 use super::{ApiError, error_response};
 use crate::access::token::{self, Claims};
-use crate::access::{Capability, registry};
+use crate::access::{Capability, challenge, registry};
+use crate::locks::MutexExt;
 use crate::state::AppState;
 
 /// The token a request came with, as taken (a request extension, set by `bearer`).
@@ -173,13 +177,27 @@ pub(crate) async fn login(
             ));
         }
     }
+    let claims = new_login(&state, swarm, now, &user.0, via.0, limit);
+    info!(user = %user.0, login = via.0, session = %claims.session, "Logged in");
+    answer(&state, &claims)
+}
+
+/// The claims of a new login of `user`, by `login`, now: a session of its own.
+fn new_login(
+    state: &AppState,
+    swarm: String,
+    now: u64,
+    user: &str,
+    login: &str,
+    limit: Option<Vec<Capability>>,
+) -> Claims {
     let session_exp = now.saturating_add(state.session_lifetime.as_millis() as u64);
-    let claims = Claims {
+    Claims {
         v: 1,
         swarm,
         issuer: state.local_id().to_owned(),
-        user: user.0.clone(),
-        login: via.0.to_owned(),
+        user: user.to_owned(),
+        login: login.to_owned(),
         iat: now,
         exp: now
             .saturating_add(state.token_lifetime.as_millis() as u64)
@@ -187,8 +205,80 @@ pub(crate) async fn login(
         session: token::new_session(),
         session_exp,
         limit,
-    };
-    info!(user = %user.0, login = via.0, session = %claims.session, "Logged in");
+    }
+}
+
+/// `POST /auth/challenge`: one to sign for a login by key, valid for five minutes.
+pub(crate) async fn challenge(State(state): State<AppState>) -> Result<Response, ApiError> {
+    let (_, now) = issuing(&state).await?;
+    let key = state
+        .node_key
+        .as_ref()
+        .ok_or(ApiError(StatusCode::SERVICE_UNAVAILABLE, None))?;
+    let (challenge, exp) = challenge::issue(key, now);
+    Ok(Json(json!({
+        "challenge": challenge,
+        "namespace": challenge::NAMESPACE,
+        "expiresAt": exp,
+    }))
+    .into_response())
+}
+
+/// A login by key's request.
+#[derive(Debug, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub(crate) struct KeyLogin {
+    user: String,
+    /// As `POST /auth/challenge` gave it.
+    challenge: String,
+    /// The user's signature of it, armored, as `ssh-keygen -Y sign -n continuum-login`
+    /// writes it.
+    signature: String,
+    #[serde(default)]
+    limit: Option<Vec<CapRequest>>,
+}
+
+/// `POST /auth/login/key`: a token, as `POST /auth/login` gives one, for a challenge
+/// signed by one of the user's keys (`401` if not, saying why); `409` in a swarm without
+/// a registry, which holds no keys.
+pub(crate) async fn login_key(
+    State(state): State<AppState>,
+    Json(request): Json<KeyLogin>,
+) -> Result<Response, ApiError> {
+    let limit = LimitRequest {
+        limit: request.limit,
+    }
+    .limit()?;
+    let (swarm, now) = issuing(&state).await?;
+    let key = state
+        .node_key
+        .as_ref()
+        .ok_or(ApiError(StatusCode::SERVICE_UNAVAILABLE, None))?;
+    {
+        let replica = state.doc.read().await;
+        if !registry::exists(&replica.doc) {
+            return Err(ApiError(
+                StatusCode::CONFLICT,
+                Some("no user registry, which holds the users' keys".to_owned()),
+            ));
+        }
+        let mut used = state.challenges.lock_or_recover();
+        challenge::take(
+            &replica.doc,
+            key,
+            &request.challenge,
+            &request.signature,
+            &request.user,
+            now,
+            &mut used,
+        )
+        .map_err(|why| {
+            debug!(user = %request.user, reason = %why, "Refused a login by key");
+            ApiError(StatusCode::UNAUTHORIZED, Some(why))
+        })?;
+    }
+    let claims = new_login(&state, swarm, now, &request.user, "key", limit);
+    info!(user = %request.user, login = "key", session = %claims.session, "Logged in");
     answer(&state, &claims)
 }
 
diff --git a/src/api/mod.rs b/src/api/mod.rs
index a12e219..2a523a4 100644
--- a/src/api/mod.rs
+++ b/src/api/mod.rs
@@ -40,7 +40,8 @@ use crate::document::store::StoreError;
 use crate::state::AppState;
 
 /// Builds the complete HTTP router. Everything except the API description (`/swagger-ui`,
-/// `/openapi.yaml`), `/health` and `/ready` is authenticated.
+/// `/openapi.yaml`), `/health`, `/ready` and logging in by key (`/auth/challenge`,
+/// `/auth/login/key`, which prove the user themselves) is authenticated.
 pub(crate) fn router(state: AppState, auth_state: AuthState, debug_api: bool) -> Router {
     let mut api: Router<AppState> = Router::new()
         .route("/store", get(store::get_store_root))
@@ -117,6 +118,9 @@ pub(crate) fn router(state: AppState, auth_state: AuthState, debug_api: bool) ->
         SwaggerUi::new("/swagger-ui").config(utoipa_swagger_ui::Config::from("../openapi.yaml")),
     )
     .route("/openapi.yaml", get(openapi_spec))
+    // Logging in by key: a challenge, and the token for it signed, without a password.
+    .route("/auth/challenge", axum::routing::post(login::challenge))
+    .route("/auth/login/key", axum::routing::post(login::login_key))
     .route("/health", get(health::node_health))
     .route("/ready", get(health::ready))
     // Outermost, so authentication failures get the error body too.