Both Red Hat and Debian-like systems configure the minimum TLS version
to be 1.2 by default, but allow users to change this via configs.
On Red Hat and derivatives this happens via crypto-policies[1], which in
writes settings in /etc/crypto-policies/back-ends/opensslcnf.config.
Most notably, it sets TLS.MinProtocol there. For Debian there's
MinProtocol in /etc/ssl/openssl.cnf. Both default to TLSv1.2, which is
considered a secure default.
In constrast, the SSLContext has a hard coded OpenSSL::SSL::TLS1_VERSION
for min_version. TLS 1.0 and 1.1 are considered insecure. By always
setting this in the default parameters, the system wide default can't be
respected, even if a developer wants to.
This takes the approach that's also done for ciphers: it's only set for
OpenSSL < 1.1.0.
[1]: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/security_hardening/using-the-system-wide-cryptographic-policies_security-hardeningae215a47ae
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