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import cbor from 'cbor';
import { COSEKEYS, COSEPublicKey } from '@webauthntine/typescript-types';
/**
* Takes COSE-encoded public key and converts it to PKCS key
*
* @param cosePublicKey COSE-encoded public key
* @return RAW PKCS encoded public key
*/
export default function convertCOSEtoPKCS(cosePublicKey: Buffer) {
/*
+------+-------+-------+---------+----------------------------------+
| name | key | label | type | description |
| | type | | | |
+------+-------+-------+---------+----------------------------------+
| crv | 2 | -1 | int / | EC Curve identifier - Taken from |
| | | | tstr | the COSE Curves registry |
| | | | | |
| x | 2 | -2 | bstr | X Coordinate |
| | | | | |
| y | 2 | -3 | bstr / | Y Coordinate |
| | | | bool | |
| | | | | |
| d | 2 | -4 | bstr | Private key |
+------+-------+-------+---------+----------------------------------+
*/
const struct: COSEPublicKey = cbor.decodeFirstSync(cosePublicKey);
const tag = Buffer.from([0x04]);
const x = struct.get(COSEKEYS.x);
const y = struct.get(COSEKEYS.y);
if (!x) {
throw new Error('COSE public key was missing x');
}
if (!y) {
throw new Error('COSE public key was missing y');
}
return Buffer.concat([tag, (x as Buffer), (y as Buffer)]);
}
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