ssl: add SSLContext#tmp_dh=

ext/openssl/extconf.rb

@@ -170,6 +170,9 @@ def find_openssl_library
 # added in 1.1.1
 have_func("EVP_PKEY_check")
 
+# added in 3.0.0
+have_func("SSL_set0_tmp_dh_pkey")
+
 Logging::message "=== Checking done. ===\n"
 
 create_header

ext/openssl/ossl_ssl.c

@@ -987,6 +987,52 @@ ossl_sslctx_set_ciphers(VALUE self, VALUE v)
     return v;
 }
 
+#ifndef OPENSSL_NO_DH
+/*
+ * call-seq:
+ *    ctx.tmp_dh = pkey
+ *
+ * Sets DH parameters used for ephemeral DH key exchange. This is relevant for
+ * servers only.
+ *
+ * +pkey+ is an instance of OpenSSL::PKey::DH. Note that key components
+ * contained in the key object, if any, are ignored. The server will always
+ * generate a new key pair for each handshake.
+ *
+ * Added in version 3.0. See also the man page SSL_set0_tmp_dh_pkey(3).
+ *
+ * Example:
+ *   ctx = OpenSSL::SSL::SSLContext.new
+ *   ctx.tmp_dh = OpenSSL::DH.generate(2048)
+ *   svr = OpenSSL::SSL::SSLServer.new(tcp_svr, ctx)
+ *   Thread.new { svr.accept }
+ */
+static VALUE
+ossl_sslctx_set_tmp_dh(VALUE self, VALUE arg)
+{
+    SSL_CTX *ctx;
+    EVP_PKEY *pkey;
+
+    rb_check_frozen(self);
+    GetSSLCTX(self, ctx);
+    pkey = GetPKeyPtr(arg);
+
+    if (EVP_PKEY_base_id(pkey) != EVP_PKEY_DH)
+        rb_raise(eSSLError, "invalid pkey type %s (expected DH)",
+                 OBJ_nid2sn(EVP_PKEY_base_id(pkey)));
+#ifdef HAVE_SSL_SET0_TMP_DH_PKEY
+    if (!SSL_CTX_set0_tmp_dh_pkey(ctx, pkey))
+        ossl_raise(eSSLError, "SSL_CTX_set0_tmp_dh_pkey");
+    EVP_PKEY_up_ref(pkey);
+#else
+    if (!SSL_CTX_set_tmp_dh(ctx, EVP_PKEY_get0_DH(pkey)))
+        ossl_raise(eSSLError, "SSL_CTX_set_tmp_dh");
+#endif
+
+    return arg;
+}
+#endif
+
 #if !defined(OPENSSL_NO_EC)
 /*
  * call-seq:
@@ -2670,6 +2716,9 @@ Init_ossl_ssl(void)
 			     ossl_sslctx_set_minmax_proto_version, 2);
     rb_define_method(cSSLContext, "ciphers",     ossl_sslctx_get_ciphers, 0);
     rb_define_method(cSSLContext, "ciphers=",    ossl_sslctx_set_ciphers, 1);
+#ifndef OPENSSL_NO_DH
+    rb_define_method(cSSLContext, "tmp_dh=", ossl_sslctx_set_tmp_dh, 1);
+#endif
     rb_define_method(cSSLContext, "ecdh_curves=", ossl_sslctx_set_ecdh_curves, 1);
     rb_define_method(cSSLContext, "security_level", ossl_sslctx_get_security_level, 0);
     rb_define_method(cSSLContext, "security_level=", ossl_sslctx_set_security_level, 1);

lib/openssl/ssl.rb

@@ -91,15 +91,17 @@ class SSLContext
       DEFAULT_CERT_STORE.set_default_paths
       DEFAULT_CERT_STORE.flags = OpenSSL::X509::V_FLAG_CRL_CHECK_ALL
 
-      # A callback invoked when DH parameters are required.
+      # A callback invoked when DH parameters are required for ephemeral DH key
+      # exchange.
       #
-      # The callback is invoked with the Session for the key exchange, an
+      # The callback is invoked with the SSLSocket, a
       # flag indicating the use of an export cipher and the keylength
       # required.
       #
       # The callback must return an OpenSSL::PKey::DH instance of the correct
       # key length.
-
+      #
+      # <b>Deprecated in version 3.0.</b> Use #tmp_dh= instead.
       attr_accessor :tmp_dh_callback
 
       # A callback invoked at connect time to distinguish between multiple
@@ -432,10 +434,6 @@ def tmp_dh_callback
         @context.tmp_dh_callback || OpenSSL::SSL::SSLContext::DEFAULT_TMP_DH_CALLBACK
       end
 
-      def tmp_ecdh_callback
-        @context.tmp_ecdh_callback
-      end
-
       def session_new_cb
         @context.session_new_cb
       end

test/openssl/test_ssl.rb

@@ -1583,13 +1583,11 @@ def test_fallback_scsv
     end
   end
 
-  def test_dh_callback
-    pend "TLS 1.2 is not supported" unless tls12_supported?
-
+  def test_tmp_dh_callback
     dh = Fixtures.pkey("dh-1")
     called = false
     ctx_proc = -> ctx {
-      ctx.ssl_version = :TLSv1_2
+      ctx.max_version = :TLS1_2
       ctx.ciphers = "DH:!NULL"
       ctx.tmp_dh_callback = ->(*args) {
         called = true
@@ -1605,10 +1603,8 @@ def test_dh_callback
   end
 
   def test_connect_works_when_setting_dh_callback_to_nil
-    pend "TLS 1.2 is not supported" unless tls12_supported?
-
     ctx_proc = -> ctx {
-      ctx.ssl_version = :TLSv1_2
+      ctx.max_version = :TLS1_2
       ctx.ciphers = "DH:!NULL" # use DH
       ctx.tmp_dh_callback = nil
     }
@@ -1621,6 +1617,20 @@ def test_connect_works_when_setting_dh_callback_to_nil
     end
   end
 
+  def test_tmp_dh
+    dh = Fixtures.pkey("dh-1")
+    ctx_proc = -> ctx {
+      ctx.max_version = :TLS1_2
+      ctx.ciphers = "DH:!NULL" # use DH
+      ctx.tmp_dh = dh
+    }
+    start_server(ctx_proc: ctx_proc) do |port|
+      server_connect(port) { |ssl|
+        assert_equal dh.to_der, ssl.tmp_key.to_der
+      }
+    end
+  end
+
   def test_ecdh_curves_tls12
     pend "EC is disabled" unless defined?(OpenSSL::PKey::EC)