Drop support for OpenSSL < 1.1.1

[ysbaddaden]

As outlined by @straight-shoota in #15419:

It appears that for older versions libssl, every SSL client socket may mutate the context for hostname validation 😮

See last line in this excerpt:

crystal/src/openssl/ssl/socket.cr

Lines 8 to 29 in 0da1746

	LibSSL.ssl_ctrl(
	@ssl,
	LibSSL::SSLCtrl::SET_TLSEXT_HOSTNAME,
	LibSSL::TLSExt::NAMETYPE_host_name,
	hostname.to_unsafe.as(Pointer(Void))
	)
	{% if LibSSL.has_method?(:ssl_get0_param) %}
	param = LibSSL.ssl_get0_param(@ssl)
	if ::Socket::IPAddress.valid?(hostname)
	unless LibCrypto.x509_verify_param_set1_ip_asc(param, hostname) == 1
	raise OpenSSL::Error.new("X509_VERIFY_PARAM_set1_ip_asc")
	end
	else
	unless LibCrypto.x509_verify_param_set1_host(param, hostname, 0) == 1
	raise OpenSSL::Error.new("X509_VERIFY_PARAM_set1_host")
	end
	end
	{% else %}
	context.set_cert_verify_callback(hostname)
	{% end %}

That would suggest that SSL context reuse isn't even concurrency safe when used to connect to different hostnames... When ssl_get0_param is missing which was introduced in OpenSSL 1.0.2. That's been EOL for a long time but we still support it.

Indeed, we must consider dropping support for OpenSSL < 1.1.1.

1.0.2 reached EOL in 2019. Even Ubuntu 18.04 (EOL in 2023) had OpenSSL 1.1.1. Despite being EOL 1.1.1 is still supported by the Ubuntu security team until 2025 (when 20.04 will reach EOL). We can look at other operating systems and distributions but most should use 3.0.0 or newer, and at worst 1.1.1 (with backported patches).

[straight-shoota]

Technically, there is still premium support for 1.0.2: https://openssl-library.org/policies/releasestrat/index.html

Versions 1.1.1 and 1.0.2 are no longer supported. Extended support for 1.1.1 and 1.0.2 to gain access to security fixes for those versions is available.

But yeah that doesn't mean we must keep it. If somebody want's to pay for Crystal premium support for outdated SSL libraries, I suppse we could reconsider though 😏💸

[ysbaddaden]

The 1.0.2 integration ain't thread-safe either since we don't define the locking_function and threadid_func callbacks. See https://docs.openssl.org/1.0.2/man3/threads/

In 1.1.1 the library is "thread-safe" by default.

[straight-shoota]

I suppose we should also drop support for similar LibreSSL versions. Probably <= 3.3 (released 2020) or something like that?

[straight-shoota]

Also related:

• libssl bindings fall back to ancient library version #14254