drb: fix tests on Debian sid/unstable with OpenSSL 1.1.1a

OpenSSL complains abour our keys being small and weak :<
Make them big and strong with 2048-bit RSA keys and SHA256 digests

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66153 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/drb/ssl.rb

@@ -162,7 +162,7 @@ module DRb
           return
         end
 
-        rsa = OpenSSL::PKey::RSA.new(1024){|p, n|
+        rsa = OpenSSL::PKey::RSA.new(2048){|p, n|
           next unless self[:verbose]
           case p
           when 0; $stderr.putc "."  # BN_generate_prime
@@ -196,7 +196,7 @@ module DRb
         if comment = self[:SSLCertComment]
           cert.add_extension(ef.create_extension("nsComment", comment))
         end
-        cert.sign(rsa, OpenSSL::Digest::SHA1.new)
+        cert.sign(rsa, OpenSSL::Digest::SHA256.new)
 
         @cert = cert
         @pkey = rsa