feat(agent): complete and improve the enrollment flow for Devolutions Agent (#1773)

Author: irvingoujAtDevolution

crates/agent-tunnel/src/enrollment_store.rs

@@ -7,13 +7,11 @@
 extern crate tracing;
 
 pub mod cert;
-pub mod enrollment_store;
 pub mod listener;
 pub mod registry;
 pub mod routing;
 pub mod stream;
 
-pub use enrollment_store::EnrollmentTokenStore;
 pub use listener::{AgentTunnelHandle, AgentTunnelListener};
 pub use registry::AgentRegistry;
 pub use stream::TunnelStream;

crates/agent-tunnel/src/lib.rs

@@ -16,7 +16,6 @@ use tokio::sync::RwLock;
 use uuid::Uuid;
 
 use super::cert::CaManager;
-use super::enrollment_store::EnrollmentTokenStore;
 use super::registry::{AgentPeer, AgentRegistry};
 use super::stream::TunnelStream;
 
@@ -33,7 +32,6 @@ pub struct AgentTunnelHandle {
     /// Map of agent_id → live Quinn connection, used for opening new streams.
     agent_connections: Arc<RwLock<HashMap<Uuid, quinn::Connection>>>,
     ca_manager: Arc<CaManager>,
-    enrollment_token_store: Arc<EnrollmentTokenStore>,
 }
 
 impl AgentTunnelHandle {
@@ -45,10 +43,6 @@ impl AgentTunnelHandle {
         &self.ca_manager
     }
 
-    pub fn enrollment_token_store(&self) -> &EnrollmentTokenStore {
-        &self.enrollment_token_store
-    }
-
     /// Open a proxy stream through a connected agent.
     // TODO: Emit TrafficEvent for connections routed through the agent tunnel.
     pub async fn connect_via_agent(
@@ -153,13 +147,11 @@ impl AgentTunnelListener {
 
         let registry = Arc::new(AgentRegistry::new());
         let agent_connections: Arc<RwLock<HashMap<Uuid, quinn::Connection>>> = Arc::new(RwLock::new(HashMap::new()));
-        let enrollment_token_store = Arc::new(EnrollmentTokenStore::new());
 
         let handle = AgentTunnelHandle {
             registry: Arc::clone(&registry),
             agent_connections: Arc::clone(&agent_connections),
-            ca_manager: Arc::clone(&ca_manager),
-            enrollment_token_store,
+            ca_manager,
         };
 
         let listener = Self {

crates/agent-tunnel/src/listener.rs

@@ -1,6 +1,7 @@
 use axum::extract::{Path, State};
 use axum::http::HeaderMap;
 use axum::{Json, Router};
+use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
 use crate::DgwState;
@@ -11,7 +12,7 @@ use crate::http::HttpError;
 ///
 /// Returns `true` if the token is a well-formed JWT whose signature verifies
 /// against `provisioner_key`, whose `exp` has not passed, and whose `scope`
-/// is `TunnelEnroll` (or `Wildcard`). Returns `false` for any failure.
+/// is `AgentEnroll` (or `Wildcard`). Returns `false` for any failure.
 ///
 /// The enrollment JWT carries extra claims (`jet_gw_url`, `jet_agent_name`)
 /// that the *agent* reads locally from its own copy of the token — the Gateway
@@ -39,25 +40,10 @@ fn validate_enrollment_jwt(token: &str, provisioner_key: &picky::key::PublicKey)
 
     matches!(
         validated.state.claims.scope,
-        AccessScope::TunnelEnroll | AccessScope::Wildcard
+        AccessScope::AgentEnroll | AccessScope::Wildcard
     )
 }
 
-/// Timing-safe byte comparison for secret values.
-///
-/// Both inputs are first hashed with SHA-256 to produce fixed 32-byte digests;
-/// the digest comparison then runs in constant time (fixed-length XOR fold).
-/// Hashing normalizes length so a leaked hash duration cannot reveal the
-/// secret's length; and the constant-time fold prevents leaking which byte
-/// differed. The function is *not* constant-time over input length, which is
-/// why it is named after its intent (timing-safe) rather than its mechanism.
-fn timing_safe_eq(a: &[u8], b: &[u8]) -> bool {
-    use sha2::{Digest, Sha256};
-    let da = Sha256::digest(a);
-    let db = Sha256::digest(b);
-    da.iter().zip(db.iter()).fold(0u8, |acc, (x, y)| acc | (x ^ y)) == 0
-}
-
 #[derive(Deserialize)]
 pub struct EnrollRequest {
     /// Agent-generated UUID (the agent owns its identity).
@@ -96,8 +82,8 @@ pub fn make_router<S>(state: DgwState) -> Router<S> {
 
 /// Enroll a new agent.
 ///
-/// Requires a Bearer token matching the configured enrollment secret
-/// or a valid one-time enrollment token from the store.
+/// Requires a Bearer token: a JWT signed by the configured provisioner key
+/// (e.g. DVLS, Hub, or any PEM service) with `AgentEnroll` or `Wildcard` scope.
 ///
 /// The agent generates its own key pair and sends a CSR. The gateway signs it
 /// and returns the certificate. The private key never leaves the agent.
@@ -108,13 +94,15 @@ async fn enroll_agent(
         ..
     }): State<DgwState>,
     headers: HeaderMap,
-    Json(req): Json<EnrollRequest>,
+    Json(EnrollRequest {
+        agent_id,
+        agent_name,
+        csr_pem,
+        agent_hostname,
+    }): Json<EnrollRequest>,
 ) -> Result<Json<EnrollResponse>, HttpError> {
     // Validate agent name: 1-255 printable ASCII characters.
-    if req.agent_name.is_empty()
-        || 255 < req.agent_name.len()
-        || req.agent_name.bytes().any(|b| !(0x20..=0x7E).contains(&b))
-    {
+    if agent_name.is_empty() || 255 < agent_name.len() || agent_name.bytes().any(|b| !(0x20..=0x7E).contains(&b)) {
         return Err(HttpError::bad_request().msg("agent name must be 1-255 printable ASCII characters"));
     }
 
@@ -134,30 +122,10 @@ async fn enroll_agent(
         .as_ref()
         .ok_or_else(|| HttpError::not_found().msg("agent enrollment is not configured"))?;
 
-    // Token validation order:
-    // 1. JWT signed by the configured provisioner key (scope == TunnelEnroll)
-    // 2. One-time enrollment token from the in-memory store
-    // 3. Static enrollment secret from configuration (constant-time comparison)
-    let jwt_valid = validate_enrollment_jwt(provided_token, &conf.provisioner_public_key);
-
-    if !jwt_valid {
-        let token_valid = handle.enrollment_token_store().redeem(provided_token).await;
-
-        if !token_valid {
-            let enrollment_secret = conf
-                .agent_tunnel
-                .enrollment_secret
-                .as_deref()
-                .ok_or_else(|| HttpError::not_found().msg("agent enrollment is not configured"))?;
-
-            if !timing_safe_eq(provided_token.as_bytes(), enrollment_secret.as_bytes()) {
-                return Err(HttpError::forbidden().msg("invalid enrollment token"));
-            }
-        }
+    if !validate_enrollment_jwt(provided_token, &conf.provisioner_public_key) {
+        return Err(HttpError::forbidden().msg("invalid enrollment token"));
     }
 
-    let agent_id = req.agent_id;
-
     // Reject duplicate agent IDs to prevent identity shadowing.
     if handle.registry().get(&agent_id).await.is_some() {
         return Err(
@@ -167,7 +135,7 @@ async fn enroll_agent(
 
     let signed = handle
         .ca_manager()
-        .sign_agent_csr(agent_id, &req.agent_name, &req.csr_pem, req.agent_hostname.as_deref())
+        .sign_agent_csr(agent_id, &agent_name, &csr_pem, agent_hostname.as_deref())
         .map_err(HttpError::bad_request().with_msg("invalid CSR").err())?;
 
     let quic_endpoint = format!("{}:{}", conf.hostname, conf.agent_tunnel.listen_port);
@@ -179,7 +147,7 @@ async fn enroll_agent(
 
     info!(
         %agent_id,
-        agent_name = %req.agent_name,
+        agent_name = %agent_name,
         "Agent enrolled successfully",
     );
 
@@ -282,7 +250,7 @@ mod tests {
         let (priv_key, pub_key) = keypair();
         let token = sign(
             json!({
-                "scope": "gateway.tunnel.enroll",
+                "scope": "gateway.agent.enroll",
                 "nbf": now_ts() - 60,
                 "exp": now_ts() + 3600,
                 "jti": Uuid::new_v4(),
@@ -334,7 +302,7 @@ mod tests {
         let (priv_key, pub_key) = keypair();
         let token = sign(
             json!({
-                "scope": "gateway.tunnel.enroll",
+                "scope": "gateway.agent.enroll",
                 "nbf": now_ts() - 7200,
                 "exp": now_ts() - 3600,
                 "jti": Uuid::new_v4(),
@@ -352,7 +320,7 @@ mod tests {
         let (_, gateway_pub) = keypair();
         let token = sign(
             json!({
-                "scope": "gateway.tunnel.enroll",
+                "scope": "gateway.agent.enroll",
                 "nbf": now_ts() - 60,
                 "exp": now_ts() + 3600,
                 "jti": Uuid::new_v4(),
@@ -369,7 +337,7 @@ mod tests {
         let (priv_key, pub_key) = keypair();
         let token = sign(
             json!({
-                "scope": "gateway.tunnel.enroll",
+                "scope": "gateway.agent.enroll",
                 "nbf": now_ts() - 60,
                 "exp": now_ts() + 3600,
                 "jti": Uuid::new_v4(),

devolutions-gateway/src/api/tunnel.rs

@@ -1941,10 +1941,6 @@ pub mod dto {
         /// UDP port for the QUIC listener (default: 4433)
         #[serde(default = "AgentTunnelConf::default_listen_port")]
         pub listen_port: u16,
-        /// Shared secret for agent enrollment.
-        /// If set, agents can enroll by providing this secret as a Bearer token.
-        #[serde(default, skip_serializing_if = "Option::is_none")]
-        pub enrollment_secret: Option<String>,
     }
 
     impl AgentTunnelConf {
@@ -1958,7 +1954,6 @@ pub mod dto {
             Self {
                 enabled: false,
                 listen_port: Self::default_listen_port(),
-                enrollment_secret: None,
             }
         }
     }