1 files changed, 56 insertions, 0 deletions
diff --git a/packages/server/src/authentication/generateAuthenticationOptions.ts b/packages/server/src/authentication/generateAuthenticationOptions.ts
new file mode 100644
index 0000000..35bf13e
--- /dev/null
+++ b/packages/server/src/authentication/generateAuthenticationOptions.ts
@@ -0,0 +1,56 @@
+import type {
+  AuthenticationExtensionsClientInputs,
+  PublicKeyCredentialRequestOptionsJSON,
+  PublicKeyCredentialDescriptor,
+  UserVerificationRequirement,
+} from '@simplewebauthn/typescript-types';
+import base64url from 'base64url';
+
+import generateChallenge from '../helpers/generateChallenge';
+
+export type GenerateAssertionOptionsOpts = {
+  allowCredentials?: PublicKeyCredentialDescriptor[];
+  challenge?: string | Buffer;
+  timeout?: number;
+  userVerification?: UserVerificationRequirement;
+  extensions?: AuthenticationExtensionsClientInputs;
+  rpID?: string;
+};
+
+/**
+ * Prepare a value to pass into navigator.credentials.get(...) for authenticator "login"
+ *
+ * @param allowCredentials Authenticators previously registered by the user, if any. If undefined
+ * the client will ask the user which credential they want to use
+ * @param challenge Random value the authenticator needs to sign and pass back
+ * user for assertion
+ * @param timeout How long (in ms) the user can take to complete assertion
+ * @param userVerification Set to `'discouraged'` when asserting as part of a 2FA flow, otherwise
+ * set to `'preferred'` or `'required'` as desired.
+ * @param extensions Additional plugins the authenticator or browser should use during assertion
+ * @param rpID Valid domain name (after `https://`)
+ */
+export default function generateAssertionOptions(
+  options: GenerateAssertionOptionsOpts = {},
+): PublicKeyCredentialRequestOptionsJSON {
+  const {
+    allowCredentials,
+    challenge = generateChallenge(),
+    timeout = 60000,
+    userVerification,
+    extensions,
+    rpID,
+  } = options;
+
+  return {
+    challenge: base64url.encode(challenge),
+    allowCredentials: allowCredentials?.map(cred => ({
+      ...cred,
+      id: base64url.encode(cred.id as Buffer),
+    })),
+    timeout,
+    userVerification,
+    extensions,
+    rpId: rpID,
+  };
+}