Deduplicate client registrations by hashing the metadata

Cargo.toml

@@ -148,6 +148,10 @@ version = "0.8.0"
 [workspace.dependencies.headers]
 version = "0.4.0"
 
+# Hex encoding and decoding
+[workspace.dependencies.hex]
+version = "0.4.3"
+
 # HTTP request/response
 [workspace.dependencies.http]
 version = "1.3.1"
@@ -184,6 +188,11 @@ version = "0.27.5"
 features = ["http1", "http2"]
 default-features = false
 
+# HashMap which preserves insertion order
+[workspace.dependencies.indexmap]
+version = "2.8.0"
+features = ["serde"]
+
 # Snapshot testing
 [workspace.dependencies.insta]
 version = "1.42.2"
@@ -278,6 +287,11 @@ version = "0.5.1"
 version = "0.8.22"
 features = ["url", "chrono", "preserve_order"]
 
+# SHA-2 cryptographic hash algorithm
+[workspace.dependencies.sha2]
+version = "0.10.8"
+features = ["oid"]
+
 # Query builder
 [workspace.dependencies.sea-query]
 version = "0.32.3"

crates/data-model/src/oauth2/client.rs

@@ -35,6 +35,9 @@ pub struct Client {
     /// Client identifier
     pub client_id: String,
 
+    /// Hash of the client metadata
+    pub metadata_digest: Option<String>,
+
     pub encrypted_client_secret: Option<String>,
 
     pub application_type: Option<ApplicationType>,
@@ -177,6 +180,7 @@ impl Client {
             Self {
                 id: Ulid::from_datetime_with_source(now.into(), rng),
                 client_id: "client1".to_owned(),
+                metadata_digest: None,
                 encrypted_client_secret: None,
                 application_type: Some(ApplicationType::Web),
                 redirect_uris: vec![
@@ -202,6 +206,7 @@ impl Client {
             Self {
                 id: Ulid::from_datetime_with_source(now.into(), rng),
                 client_id: "client2".to_owned(),
+                metadata_digest: None,
                 encrypted_client_secret: None,
                 application_type: Some(ApplicationType::Native),
                 redirect_uris: vec![Url::parse("https://client2.example.com/redirect").unwrap()],

crates/handlers/Cargo.toml

@@ -72,10 +72,12 @@ base64ct.workspace = true
 camino.workspace = true
 chrono.workspace = true
 elliptic-curve.workspace = true
+hex.workspace = true
 governor.workspace = true
-indexmap = "2.8.0"
+indexmap.workspace = true
 pkcs8.workspace = true
 psl = "2.1.96"
+sha2.workspace = true
 time = "0.3.41"
 url.workspace = true
 mime = "0.3.17"

crates/handlers/src/graphql/tests.rs

@@ -37,6 +37,7 @@ async fn create_test_client(state: &TestState) -> Client {
             vec![],
             None,
             None,
+            None,
             vec![],
             None,
             None,

crates/handlers/src/oauth2/registration.rs

@@ -22,6 +22,7 @@ use oauth2_types::{
 use psl::Psl;
 use rand::distributions::{Alphanumeric, DistString};
 use serde::Serialize;
+use sha2::Digest as _;
 use thiserror::Error;
 use tracing::info;
 use url::Url;
@@ -50,6 +51,7 @@ impl_from_error_for_route!(mas_storage::RepositoryError);
 impl_from_error_for_route!(mas_policy::LoadError);
 impl_from_error_for_route!(mas_policy::EvaluationError);
 impl_from_error_for_route!(mas_keystore::aead::Error);
+impl_from_error_for_route!(serde_json::Error);
 
 impl IntoResponse for RouteError {
     fn into_response(self) -> axum::response::Response {
@@ -204,7 +206,10 @@ pub(crate) async fn post(
     // Propagate any JSON extraction error
     let Json(body) = body?;
 
-    info!(?body, "Client registration");
+    // We need to serialize the body to compute the hash, and to log it
+    let body_json = serde_json::to_string(&body)?;
+
+    info!(body = body_json, "Client registration");
 
     let user_agent = user_agent.map(|ua| ua.to_string());
 
@@ -276,34 +281,59 @@ pub(crate) async fn post(
         _ => (None, None),
     };
 
-    let client = repo
-        .oauth2_client()
-        .add(
-            &mut rng,
-            &clock,
-            metadata.redirect_uris().to_vec(),
-            encrypted_client_secret,
-            metadata.application_type.clone(),
-            //&metadata.response_types(),
-            metadata.grant_types().to_vec(),
-            metadata
-                .client_name
-                .clone()
-                .map(Localized::to_non_localized),
-            metadata.logo_uri.clone().map(Localized::to_non_localized),
-            metadata.client_uri.clone().map(Localized::to_non_localized),
-            metadata.policy_uri.clone().map(Localized::to_non_localized),
-            metadata.tos_uri.clone().map(Localized::to_non_localized),
-            metadata.jwks_uri.clone(),
-            metadata.jwks.clone(),
-            // XXX: those might not be right, should be function calls
-            metadata.id_token_signed_response_alg.clone(),
-            metadata.userinfo_signed_response_alg.clone(),
-            metadata.token_endpoint_auth_method.clone(),
-            metadata.token_endpoint_auth_signing_alg.clone(),
-            metadata.initiate_login_uri.clone(),
-        )
-        .await?;
+    // If the client doesn't have a secret, we may be able to deduplicate it. To
+    // do so, we hash the client metadata, and look for it in the database
+    let (digest_hash, existing_client) = if client_secret.is_none() {
+        // XXX: One interesting caveat is that we hash *before* saving to the database.
+        // It means it takes into account fields that we don't care about *yet*.
+        //
+        // This means that if later we start supporting a particular field, we
+        // will still serve the 'old' client_id, without updating the client in the
+        // database
+        let hash = sha2::Sha256::digest(body_json);
+        let hash = hex::encode(hash);
+        let client = repo.oauth2_client().find_by_metadata_digest(&hash).await?;
+        (Some(hash), client)
+    } else {
+        (None, None)
+    };
+
+    let client = if let Some(client) = existing_client {
+        tracing::info!(%client.id, "Reusing existing client");
+        client
+    } else {
+        let client = repo
+            .oauth2_client()
+            .add(
+                &mut rng,
+                &clock,
+                metadata.redirect_uris().to_vec(),
+                digest_hash,
+                encrypted_client_secret,
+                metadata.application_type.clone(),
+                //&metadata.response_types(),
+                metadata.grant_types().to_vec(),
+                metadata
+                    .client_name
+                    .clone()
+                    .map(Localized::to_non_localized),
+                metadata.logo_uri.clone().map(Localized::to_non_localized),
+                metadata.client_uri.clone().map(Localized::to_non_localized),
+                metadata.policy_uri.clone().map(Localized::to_non_localized),
+                metadata.tos_uri.clone().map(Localized::to_non_localized),
+                metadata.jwks_uri.clone(),
+                metadata.jwks.clone(),
+                // XXX: those might not be right, should be function calls
+                metadata.id_token_signed_response_alg.clone(),
+                metadata.userinfo_signed_response_alg.clone(),
+                metadata.token_endpoint_auth_method.clone(),
+                metadata.token_endpoint_auth_signing_alg.clone(),
+                metadata.initiate_login_uri.clone(),
+            )
+            .await?;
+        tracing::info!(%client.id, "Registered new client");
+        client
+    };
 
     let response = ClientRegistrationResponse {
         client_id: client.client_id.clone(),
@@ -490,4 +520,51 @@ mod tests {
         let response: ClientRegistrationResponse = response.json();
         assert!(response.client_secret.is_some());
     }
+    #[sqlx::test(migrator = "mas_storage_pg::MIGRATOR")]
+    async fn test_registration_dedupe(pool: PgPool) {
+        setup();
+        let state = TestState::from_pool(pool).await.unwrap();
+
+        // Post a client registration twice, we should get the same client ID
+        let request =
+            Request::post(mas_router::OAuth2RegistrationEndpoint::PATH).json(serde_json::json!({
+                "client_uri": "https://example.com/",
+                "redirect_uris": ["https://example.com/"],
+                "response_types": ["code"],
+                "grant_types": ["authorization_code"],
+                "token_endpoint_auth_method": "none",
+            }));
+
+        let response = state.request(request.clone()).await;
+        response.assert_status(StatusCode::CREATED);
+        let response: ClientRegistrationResponse = response.json();
+        let client_id = response.client_id;
+
+        let response = state.request(request).await;
+        response.assert_status(StatusCode::CREATED);
+        let response: ClientRegistrationResponse = response.json();
+        assert_eq!(response.client_id, client_id);
+
+        // Doing that with a client that has a client_secret should not deduplicate
+        let request =
+            Request::post(mas_router::OAuth2RegistrationEndpoint::PATH).json(serde_json::json!({
+                "client_uri": "https://example.com/",
+                "redirect_uris": ["https://example.com/"],
+                "response_types": ["code"],
+                "grant_types": ["authorization_code"],
+                "token_endpoint_auth_method": "client_secret_basic",
+            }));
+
+        let response = state.request(request.clone()).await;
+        response.assert_status(StatusCode::CREATED);
+        let response: ClientRegistrationResponse = response.json();
+        // Sanity check that the client_id is different
+        assert_ne!(response.client_id, client_id);
+        let client_id = response.client_id;
+
+        let response = state.request(request).await;
+        response.assert_status(StatusCode::CREATED);
+        let response: ClientRegistrationResponse = response.json();
+        assert_ne!(response.client_id, client_id);
+    }
 }

crates/jose/Cargo.toml

@@ -29,7 +29,7 @@ sec1 = "0.7.3"
 serde.workspace = true
 serde_json.workspace = true
 serde_with = "3.12.0"
-sha2 = { version = "0.10.8", features = ["oid"] }
+sha2.workspace = true
 signature = "2.2.0"
 thiserror.workspace = true
 url.workspace = true

crates/oauth2-types/Cargo.toml

@@ -19,11 +19,13 @@ language-tags = { version = "0.3.2", features = ["serde"] }
 url.workspace = true
 serde_with = { version = "3.12.0", features = ["chrono"] }
 chrono.workspace = true
-sha2 = "0.10.8"
+sha2.workspace = true
 thiserror.workspace = true
+indexmap.workspace = true
 
 mas-iana.workspace = true
 mas-jose.workspace = true
 
 [dev-dependencies]
 assert_matches = "1.5.0"
+insta.workspace = true