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import {
PublicKeyCredentialRequestOptionsJSON,
AssertionCredential,
AssertionCredentialJSON,
} from '@simplewebauthn/typescript-types';
import bufferToBase64URLString from '../helpers/bufferToBase64URLString';
import base64URLStringToBuffer from '../helpers/base64URLStringToBuffer';
import bufferToUTF8String from '../helpers/bufferToUTF8String';
import supportsWebauthn from '../helpers/supportsWebauthn';
import toPublicKeyCredentialDescriptor from '../helpers/toPublicKeyCredentialDescriptor';
/**
* Begin authenticator "login" via WebAuthn assertion
*
* @param requestOptionsJSON Output from @simplewebauthn/server's generateAssertionOptions(...)
*/
export default async function startAssertion(
requestOptionsJSON: PublicKeyCredentialRequestOptionsJSON,
): Promise<AssertionCredentialJSON> {
if (!supportsWebauthn()) {
throw new Error('WebAuthn is not supported in this browser');
}
// We need to avoid passing empty array to avoid blocking retrieval
// of public key
let allowCredentials;
if (requestOptionsJSON.allowCredentials?.length !== 0) {
allowCredentials = requestOptionsJSON.allowCredentials?.map(toPublicKeyCredentialDescriptor);
}
// We need to convert some values to Uint8Arrays before passing the credentials to the navigator
const publicKey: PublicKeyCredentialRequestOptions = {
...requestOptionsJSON,
challenge: base64URLStringToBuffer(requestOptionsJSON.challenge),
allowCredentials,
};
// Wait for the user to complete assertion
const credential = (await navigator.credentials.get({ publicKey })) as AssertionCredential;
if (!credential) {
throw new Error('Assertion was not completed');
}
const { id, rawId, response, type } = credential;
let userHandle = undefined;
if (response.userHandle) {
userHandle = bufferToUTF8String(response.userHandle);
}
// Convert values to base64 to make it easier to send back to the server
return {
id,
rawId: bufferToBase64URLString(rawId),
response: {
authenticatorData: bufferToBase64URLString(response.authenticatorData),
clientDataJSON: bufferToBase64URLString(response.clientDataJSON),
signature: bufferToBase64URLString(response.signature),
userHandle,
},
type,
clientExtensionResults: credential.getClientExtensionResults(),
};
}
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