1 files changed, 59 insertions, 0 deletions
diff --git a/packages/browser/src/helpers/identifyAuthenticationError.ts b/packages/browser/src/helpers/identifyAuthenticationError.ts
new file mode 100644
index 0000000..7f9bd82
--- /dev/null
+++ b/packages/browser/src/helpers/identifyAuthenticationError.ts
@@ -0,0 +1,59 @@
+import { isValidDomain } from './isValidDomain';
+import { WebAuthnError } from './structs';
+
+/**
+ * Attempt to intuit _why_ an error was raised after calling `navigator.credentials.get()`
+ */
+export function identifyAuthenticationError({
+  error,
+  options,
+}: {
+  error: Error;
+  options: CredentialRequestOptions;
+}): WebAuthnError | Error {
+  const { publicKey } = options;
+
+  if (!publicKey) {
+    throw Error('options was missing required publicKey property');
+  }
+
+  if (error.name === 'AbortError') {
+    if (options.signal === new AbortController().signal) {
+      // https://www.w3.org/TR/webauthn-2/#sctn-createCredential (Step 16)
+      return new WebAuthnError('Authentication ceremony was sent an abort signal (AbortError)');
+    }
+  } else if (error.name === 'NotAllowedError') {
+    if (publicKey.allowCredentials?.length) {
+      // https://www.w3.org/TR/webauthn-2/#sctn-discover-from-external-source (Step 17)
+      // https://www.w3.org/TR/webauthn-2/#sctn-op-get-assertion (Step 6)
+      return new WebAuthnError(
+        'No available authenticator recognized any of the allowed credentials (NotAllowedError)',
+      );
+    }
+
+    // https://www.w3.org/TR/webauthn-2/#sctn-discover-from-external-source (Step 18)
+    // https://www.w3.org/TR/webauthn-2/#sctn-op-get-assertion (Step 7)
+    return new WebAuthnError(
+      'User clicked cancel, or the authentication ceremony timed out (NotAllowedError)',
+    );
+  } else if (error.name === 'SecurityError') {
+    const effectiveDomain = window.location.hostname;
+    if (!isValidDomain(effectiveDomain)) {
+      // https://www.w3.org/TR/webauthn-2/#sctn-discover-from-external-source (Step 5)
+      return new WebAuthnError(`${window.location.hostname} is an invalid domain (SecurityError)`);
+    } else if (publicKey.rpId !== effectiveDomain) {
+      // https://www.w3.org/TR/webauthn-2/#sctn-discover-from-external-source (Step 6)
+      return new WebAuthnError(
+        `The RP ID "${publicKey.rpId}" is invalid for this domain (SecurityError)`,
+      );
+    }
+  } else if (error.name === 'UnknownError') {
+    // https://www.w3.org/TR/webauthn-2/#sctn-op-get-assertion (Step 1)
+    // https://www.w3.org/TR/webauthn-2/#sctn-op-get-assertion (Step 12)
+    return new WebAuthnError(
+      'The authenticator was unable to process the specified options, or could not create a new assertion signature (UnknownError)',
+    );
+  }
+
+  return error;
+}