jsrsasign doesnt support creating RSA object from public in the ASN.1 form, one needs to extract modulus and exponent manually (typescript)

rsafrompub.ts

function getRsaFromPubKey(pubKeyB64: string): RSAKey {
    const pubKeyDecoded = b64tohex(pubKeyB64);

    // jsrsasign cannot build key out of PEM or ASN.1 string, so we have to extract modulus and exponent
    // you can get some idea what happens from the link below (keep in mind that in JS every char is 2 bytes)
    // https://crypto.stackexchange.com/questions/18031/how-to-find-modulus-from-a-rsa-public-key/18034#18034
    const modulus = pubKeyDecoded.substr(50, 128);
    const exp = pubKeyDecoded.substr(182, pubKeyDecoded.length);

    return KEYUTIL.getKey({n: modulus, e: exp});
}