Is it possible to convert rsa public key to x509 public key?

Question

I have following public key:

-----BEGIN RSA PUBLIC KEY-----
... key ...
-----END RSA PUBLIC KEY-----

PHP can't work with that public key. I found that it should be in x509 format to be usable in php. Is it possible to convert this key to x509 format? As i understand result should look like:

-----BEGIN PUBLIC KEY-----
... changed? key ...
-----END PUBLIC KEY-----

UPD: Exactly it was necessary to generate x509 certificate, not just public key.

Answer 1

phpseclib, a pure PHP RSA library, can work with RSA keys of that format just fine.

That said, with regard to openssl, you are right - RSA public keys need to be encapsulated in X.509 certs to work with most openssl_* functions.

From the phpseclib interoperability documentation:

// openssl_get_publickey() only creates public key resources from X.509
// certificates hence our creating one
$dn = array();  // use defaults
$res_privkey = openssl_pkey_get_private($privkey);
$res_csr = openssl_csr_new($dn, $res_privkey);
$res_cert = openssl_csr_sign($res_csr, null, $res_privkey, 365);
openssl_x509_export($res_cert, $str_cert);
$res_pubkey = openssl_get_publickey($str_cert);

That said the result shouldn't look like what you posted but rather like this:

-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----