test: validate PQC TLS cryptography in showcase integration tests

shared/Gemfile

@@ -17,3 +17,4 @@ gem "minitest-autotest", "~> 1.0"
 gem "minitest-focus", "~> 1.0"
 gem "ostruct", "0.6.3"
 gem "rake", ">= 12.0"
+gem 'fiddle'

shared/test/showcase/pqc_test.rb

@@ -0,0 +1,44 @@
+require "test_helper"
+require "fiddle"
+require "openssl"
+
+module PQProbe
+  LIBSSL = Fiddle.dlopen("libssl.so.3")
+  GET_GROUP_NAME = Fiddle::Function.new(
+    LIBSSL["SSL_get0_group_name"],
+    [Fiddle::TYPE_VOIDP], Fiddle::TYPE_VOIDP
+  )
+  DATA_OFFSET = 32
+
+  def self.group_of(ssl_socket)
+    value_addr = Fiddle.dlwrap(ssl_socket)
+    ssl_ptr = Fiddle::Pointer.new(value_addr)[DATA_OFFSET, 8].unpack1("Q")
+    return "(no SSL*)" if ssl_ptr.zero?
+    name = GET_GROUP_NAME.call(ssl_ptr)
+    name.null? ? "(none)" : name.to_s
+  end
+
+  def connect_nonblock(*, **)
+    super.tap do |ret|
+      next if ret.is_a?(Symbol)
+      @negotiated_group = PQProbe.group_of(self)
+    end
+  end
+
+  def connect
+    super.tap { @negotiated_group = PQProbe.group_of(self) }
+  end
+
+  def negotiated_group
+    @negotiated_group
+  end
+end
+OpenSSL::SSL::SSLSocket.prepend PQProbe
+
+class PqcRestTest < ShowcaseTest
+  def test_rest_pqc_negotiation
+    client = new_echo_rest_client
+    response = client.echo content: "PQC check"
+    assert_equal "PQC check", response.content
+  end
+end

shared/test/showcase/test_helper.rb

@@ -19,6 +19,25 @@
 require "fileutils"
 require "open3"
 require "tmpdir"
+require "openssl"
+
+def generate_local_tls_certs(tmp_dir)
+  key = OpenSSL::PKey::RSA.new(2048)
+  cert = OpenSSL::X509::Certificate.new
+  cert.version = 2
+  cert.serial = 1
+  cert.subject = OpenSSL::X509::Name.parse("/CN=localhost")
+  cert.issuer = cert.subject
+  cert.public_key = key.public_key
+  cert.not_before = Time.now
+  cert.not_after = cert.not_before + 3600
+  cert.sign(key, OpenSSL::Digest::SHA256.new)
+  cert_path = File.join(tmp_dir, 'cert.pem')
+  key_path = File.join(tmp_dir, 'key.pem')
+  File.write(cert_path, cert.to_pem)
+  File.write(key_path, key.to_pem)
+end
+
 
 # @private
 GAPIC_SHOWCASE_VERSION = '0.42.0'
@@ -68,32 +87,32 @@ def tar_file_name
 class ShowcaseTest < Minitest::Test
   def new_echo_client
     Google::Showcase::V1beta1::Echo::Client.new do |config|
-      config.credentials = :this_channel_is_insecure
+      config.credentials = GRPC::Core::ChannelCredentials.new
     end
   end
 
   def new_echo_rest_client
     Google::Showcase::V1beta1::Echo::Rest::Client.new do |config|
-      config.endpoint = "http://localhost:7469"
+      config.endpoint = "https://localhost:7469"
       config.credentials = :this_channel_is_insecure
     end
   end
 
   def new_identity_client
     Google::Showcase::V1beta1::Identity::Client.new do |config|
-      config.credentials = :this_channel_is_insecure
+      config.credentials = GRPC::Core::ChannelCredentials.new
     end
   end
 
   def new_echo_operations_client
     Google::Showcase::V1beta1::Echo::Operations.new do |config|
-      config.credentials = :this_channel_is_insecure
+      config.credentials = GRPC::Core::ChannelCredentials.new
     end
   end
 
   def new_compliance_rest_client
     Google::Showcase::V1beta1::Compliance::Rest::Client.new do |config|
-      config.endpoint = "http://localhost:7469"
+      config.endpoint = "https://localhost:7469"
       config.credentials = :this_channel_is_insecure
     end
   end
@@ -106,7 +125,11 @@ def new_compliance_rest_client
       url = "https://github.com/googleapis/gapic-showcase/releases/download/v#{GAPIC_SHOWCASE_VERSION}/#{tar_file_name}"
       _, status = Open3.capture2 "curl -sSL #{url} | tar -zx --directory #{tmp_dir}/"
       raise "failed to start showcase" unless status.exitstatus.zero?
-      server_id = Process.spawn("#{tmp_dir}/gapic-showcase run", :out => [log_file, "w"])
+      generate_local_tls_certs(tmp_dir)
+ENV["GRPC_DEFAULT_SSL_ROOTS_FILE_PATH"] = "#{tmp_dir}/cert.pem"
+ENV["SSL_CERT_FILE"] = "#{tmp_dir}/cert.pem"
+server_id = Process.spawn("#{tmp_dir}/gapic-showcase run --tls-cert=#{tmp_dir}/cert.pem --tls-key=#{tmp_dir}/key.pem", :out => [log_file, "w"])
+
       puts "Started showcase server v#{GAPIC_SHOWCASE_VERSION} (pid: #{server_id}) > #{log_file}." if ENV["VERBOSE"]
     else
       puts "Existing showcase server is available. Continuing..." if ENV["VERBOSE"]