1 files changed, 29 insertions, 0 deletions
diff --git a/packages/server/src/assertion/generateAssertionCredentials.ts b/packages/server/src/assertion/generateAssertionCredentials.ts
new file mode 100644
index 0000000..71f9e44
--- /dev/null
+++ b/packages/server/src/assertion/generateAssertionCredentials.ts
@@ -0,0 +1,29 @@
+import base64url from 'base64url';
+
+import { AssertionCredentials } from '@libTypes';
+
+/**
+ * Prepare credentials for user registration via navigator.credentials.get(...)
+ *
+ * @param challenge Random string the authenticator needs to sign and pass back
+ * @param base64CredentialIDs Array of base64-encoded authenticator IDs registered by the user for
+ * assertion
+ * @param timeout How long (in ms) the user can take to complete attestation
+ */
+export default function generateAssertionCredentials(
+  challenge: string,
+  base64CredentialIDs: string[],
+  timeout: number = 60000,
+): AssertionCredentials {
+  return {
+    publicKey: {
+      challenge: Uint8Array.from(challenge, c => c.charCodeAt(0)),
+      allowCredentials: base64CredentialIDs.map(id => ({
+        id: base64url.toBuffer(id),
+        type: 'public-key',
+        transports: ['usb', 'ble', 'nfc'],
+      })),
+      timeout,
+    },
+  };
+}