SAML plugin creates RSA 1024 key/certificate

[Lorenz Ulrich]

The SAML plugin creates RSA keys with a length of 1024 bits which is considered insecure. Some services, such as the Swiss academic network SWITCH, maintaining a Shibboleth-based infrastructure, don't accept RSA 1024 keys anymore.

Ideally, this should be configurable, but I would suggest to raise default to 2048 bits:

auth/saml/lib.php, line 639

Replace

$privkey = openssl_pkey_new();

with

$privkey = openssl_pkey_new(['private_key_bits' => 2048]);

Affected version: 21.04.01