Parsing X509 Certificate Bundles in nodeJS - node.js

Question

I am trying to parse a x509 certificate bundle which is a pem file consisting of multiple certificates in the following format:
-----BEGIN CERTIFICATE-----
xxxx
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
xxxx
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
xxxx
-----END CERTIFICATE-----
I am able to read and parse a single certificate pem file using jsrsasign X509 library like so:
import r from "jsrsasign";
const cert = new r.X509();
cert.readCertPEM(input);
issuer = cert.getIssuerString();
I need to parse the certificate bundles in a similar fashion. How can I do it ? I am using Nodejs.
I tried using Regular Expressions to extract individual certificates as strings and pass it to cert.readCertPEM(input) in a loop. But I was not able to figure out the proper RE to do so.
If using RE is the way to go, then can I please know how I can do it.
Thanks.

Answer 1

Youcould match the begin certificate part, then capture in a group matching all lines that do not start with ----- using a negative lookahead (?!-----) and after that match the end certificate part.
^-----BEGIN CERTIFICATE-----\r?\n((?:(?!-----).*\r?\n)*)-----END CERTIFICATE-----
Regex demo
const regex = /^-----BEGIN CERTIFICATE-----\r?\n((?:(?!-----).*\r?\n)*)-----END CERTIFICATE-----/gm;
const str = `-----BEGIN CERTIFICATE-----
xxxx
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
xxxx
xxxx
xxxx
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
xxxx
-----END CERTIFICATE-----`;
let m;
while ((m = regex.exec(str)) !== null) {
// This is necessary to avoid infinite loops with zero-width matches
if (m.index === regex.lastIndex) {
regex.lastIndex++;
}
console.log(m[1]);
}