Validate that a private key and the public key of a certificate match

Today the code does the validation too late, when connecting (client side) or when receiving a connection (server side). Especially on the server side, you want to know upfront that your configuration is wrong, instead of waiting for the first client attempting to connect

I think the cleanest way would be to provide an accessor to the public key from the private key:

/* If the key is a private key, return the associated public key */
QSslCertificate QSslKey::privateKey() const

/* Existing API: return the public key of the certificate */
QSslKey QSslCertificate::publicKey() const

Sample interation would be through the == operator:

QSslKey private(…)
QSslCertificate cert(…)
if (private.publicKey() != cert.publicKey()) {
// wrong key pair…
}