add a default certificate for the fast server

lib/postal/config.rb

@@ -103,14 +103,14 @@ module Postal
     config.smtp&.from_address || "postal@example.com"
   end
 
-  def self.smtp_private_key
-    @smtp_private_key ||= OpenSSL::PKey::RSA.new(File.read(smtp_private_key_path))
-  end
-
   def self.smtp_private_key_path
     config.smtp_server.tls_private_key_path || config_root.join('smtp.key')
   end
 
+  def self.smtp_private_key
+    @smtp_private_key ||= OpenSSL::PKey::RSA.new(File.read(smtp_private_key_path))
+  end
+
   def self.smtp_certificate_path
     config.smtp_server.tls_certificate_path || config_root.join('smtp.cert')
   end
@@ -128,6 +128,31 @@ module Postal
     end
   end
 
+  def self.fast_server_default_private_key_path
+    config.fast_server.default_private_key_path || config_root.join('fast_server.key')
+  end
+
+  def self.fast_server_default_private_key
+    @fast_server_default_private_key ||= OpenSSL::PKey::RSA.new(File.read(fast_server_default_private_key_path))
+  end
+
+  def self.fast_server_default_certificate_path
+    config.fast_server.default_tls_certificate_path || config_root.join('fast_server.cert')
+  end
+
+  def self.fast_server_default_certificate_data
+    @fast_server_default_certificate_data ||= File.read(fast_server_default_certificate_path)
+  end
+
+  def self.fast_server_default_certificates
+    @fast_server_default_certificates ||= begin
+      certs = self.fast_server_default_certificate_data.scan(/-----BEGIN CERTIFICATE-----.+?-----END CERTIFICATE-----/m)
+      certs.map do |c|
+        OpenSSL::X509::Certificate.new(c)
+      end.freeze
+    end
+  end
+
   def self.lets_encrypt_private_key_path
     @lets_encrypt_private_key_path ||= Postal.config_root.join('lets_encrypt.pem')
   end

lib/postal/fast_server/client.rb

@@ -140,9 +140,9 @@ module Postal
           end
 
           if ssl_context.cert.nil?
-            ssl_context.cert = Postal.smtp_certificates[0]
-            ssl_context.extra_chain_cert = Postal.smtp_certificates[1..-1]
-            ssl_context.key  = Postal.smtp_private_key
+            ssl_context.cert = Postal.fast_server_default_certificates[0]
+            ssl_context.extra_chain_cert = Postal.fast_server_default_certificates[1..-1]
+            ssl_context.key  = Postal.fast_server_default_private_key
           end
 
           ssl_context.ssl_version = "SSLv23"