ox
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JavaScript
import { p256 } from '@noble/curves/p256';
import * as Hex from '../Hex.js';
import * as PublicKey from '../PublicKey.js';
import { CredentialCreationFailedError } from '../WebAuthnP256.js';
/**
* Parses an ASN.1 signature into a r and s value.
*
* @internal
*/
export function parseAsn1Signature(bytes) {
const r_start = bytes[4] === 0 ? 5 : 4;
const r_end = r_start + 32;
const s_start = bytes[r_end + 2] === 0 ? r_end + 3 : r_end + 2;
const r = BigInt(Hex.fromBytes(bytes.slice(r_start, r_end)));
const s = BigInt(Hex.fromBytes(bytes.slice(s_start)));
return {
r,
s: s > p256.CURVE.n / 2n ? p256.CURVE.n - s : s,
};
}
/**
* Parses a public key into x and y coordinates from the public key
* defined on the credential.
*
* @internal
*/
export async function parseCredentialPublicKey(response) {
try {
const publicKeyBuffer = response.getPublicKey();
if (!publicKeyBuffer)
throw new CredentialCreationFailedError();
// Converting `publicKeyBuffer` throws when credential is created by 1Password Firefox Add-on
const publicKeyBytes = new Uint8Array(publicKeyBuffer);
const cryptoKey = await crypto.subtle.importKey('spki', new Uint8Array(publicKeyBytes), {
name: 'ECDSA',
namedCurve: 'P-256',
hash: 'SHA-256',
}, true, ['verify']);
const publicKey = new Uint8Array(await crypto.subtle.exportKey('raw', cryptoKey));
return PublicKey.from(publicKey);
}
catch (error) {
// Fallback for 1Password Firefox Add-on restricts access to certain credential properties
// so we need to use `attestationObject` to extract the public key.
// https://github.com/passwordless-id/webauthn/issues/50#issuecomment-2072902094
if (error.message !== 'Permission denied to access object')
throw error;
const data = new Uint8Array(response.attestationObject);
const coordinateLength = 0x20;
const cborPrefix = 0x58;
const findStart = (key) => {
const coordinate = new Uint8Array([key, cborPrefix, coordinateLength]);
for (let i = 0; i < data.length - coordinate.length; i++)
if (coordinate.every((byte, j) => data[i + j] === byte))
return i + coordinate.length;
throw new CredentialCreationFailedError();
};
const xStart = findStart(0x21);
const yStart = findStart(0x22);
return PublicKey.from(new Uint8Array([
0x04,
...data.slice(xStart, xStart + coordinateLength),
...data.slice(yStart, yStart + coordinateLength),
]));
}
}
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