CODEWITHSUNDEEP
javascriptnode.jstypescriptamazon-kmsnode-forge
SpikETidE
SpikETidE

Reputation: 6961

Extract public key from a DER encoded X.509 Cert using node-forge and Javascript

I have an asymmetric key created in AWS KMS. I am trying to obtain it's public key using Javascript. To do that, I use the GetPublicKey API that comes with the aws-sdk. In the API's response, the public key is returned as an Uint8Array which represents a

a DER-encoded X.509 public key, also known as SubjectPublicKeyInfo (SPKI), as defined in RFC 5280

I am trying to retrieve the public key string from this object, so that I can use that for further encryption.

My code looks like below

import * as forge from 'node-forge';
import { GetPublicKeyCommand, KMSClient  } from "@aws-sdk/client-kms";    
function getPublicKeyFromKMS() {
        const response = await kmsClient.send(new GetPublicKeyCommand(getKeyInput));
        const uIntArrayKey = response.PublicKey!;
        const bufferKey = Buffer.from(uIntArrayKey.buffer);
        const cert = forge.pki.certificateFromAsn1(forge.asn1.fromDer(new  forge.util.ByteStringBuffer(bufferKey), false ));
        console.log(cert.publicKey)
        return cert.publicKey;
    }

I use the node-forge module to get the certificate from the DER encoded response.

My issue is :
When I do forge.asn1.fromDer(new forge.util.ByteStringBuffer(bufferKey), false ) , I get the below error.

Error: Unparsed DER bytes remain after ASN.1 parsing. at Object.asn1.fromDer (/Users/####/node_modules/node-forge/lib/asn1.js:460:17)

byteCount: 8192, remaining: 8111

How do I make sure that I pass only the necessary bytes to the fromDer() function? Or How do I handle the remaining bytes to avoid this error?

Upvotes: 1

Views: 971

Answers (0)

Related Questions