Add WebAuthn authentication flow

edb/lib/ext/auth.edgeql

@@ -76,6 +76,16 @@ CREATE EXTENSION PACKAGE auth VERSION '1.0' {
             create constraint exclusive;
         };
 
+        create trigger email_shares_user_handle after insert for each do (
+            std::assert(
+                (__new__.user_handle = (
+                    select detached ext::auth::WebAuthnFactor
+                    filter .email = __new__.email
+                    and not .id = __new__.id
+                ).user_handle) ?? true,
+                message := "user_handle must be the same for a given email"
+            )
+        );
         create constraint exclusive on ((.email, .credential_id));
     };
 

edb/server/protocol/auth_ext/webauthn.py

@@ -284,8 +284,17 @@ async def create_authentication_options_for_email(
             cached_globally=True,
         )
         result_json = json.loads(result.decode())
+        if len(result_json) == 0:
+            raise errors.WebAuthnAuthenticationFailed(
+                "No WebAuthn credentials found for the email."
+            )
+
         user_handles: set[str] = {x["user_handle"] for x in result_json}
-        assert len(user_handles) == 1
+        if len(user_handles) > 1:
+            raise errors.WebAuthnAuthenticationFailed(
+                "Multiple user handles found for the email."
+            )
+
         user_handle = base64.b64decode(result_json[0]["user_handle"])
 
         credential_ids = [

tests/test_http_ext_auth.py

@@ -34,6 +34,7 @@
 from typing import Any, Callable
 from jwcrypto import jwt, jwk
 
+from edgedb import QueryAssertionError
 from edb.testbase import http as tb
 from edb.common import assert_data_shape
 
@@ -3639,6 +3640,55 @@ async def test_http_auth_ext_webauthn_register_options_existing_user(self):
 
             self.assertEqual(user_id_decoded, existing_user_handle)
 
+    async def test_http_auth_ext_webauthn_emails_share_user_handle(self):
+        email = "[email protected]"
+
+        user_handle_one = uuid.uuid4().bytes
+        credential_id_one = uuid.uuid4().bytes
+        public_key_one = uuid.uuid4().bytes
+
+        user_handle_two = uuid.uuid4().bytes
+        credential_id_two = uuid.uuid4().bytes
+        public_key_two = uuid.uuid4().bytes
+
+        with self.assertRaisesRegex(
+            QueryAssertionError,
+            "user_handle must be the same for a given email",
+        ):
+            await self.con.execute(
+                """
+                with
+                    factor_one := (insert ext::auth::WebAuthnFactor {
+                        email := <str>$email,
+                        user_handle := <bytes>$user_handle_one,
+                        credential_id := <bytes>$credential_id_one,
+                        public_key := <bytes>$public_key_one,
+                        identity := (insert ext::auth::LocalIdentity {
+                            issuer := "local",
+                            subject := "",
+                        }),
+                    }),
+                    factor_two := (insert ext::auth::WebAuthnFactor {
+                        email := <str>$email,
+                        user_handle := <bytes>$user_handle_two,
+                        credential_id := <bytes>$credential_id_two,
+                        public_key := <bytes>$public_key_two,
+                        identity := (insert ext::auth::LocalIdentity {
+                            issuer := "local",
+                            subject := "",
+                        }),
+                    })
+                select true;
+                """,
+                email=email,
+                user_handle_one=user_handle_one,
+                credential_id_one=credential_id_one,
+                public_key_one=public_key_one,
+                user_handle_two=user_handle_two,
+                credential_id_two=credential_id_two,
+                public_key_two=public_key_two,
+            )
+
     async def test_http_auth_ext_webauthn_authenticate_options(self):
         with self.http_con() as http_con:
             email = "[email protected]"