ssl: remove SSL::SSLContext#tmp_ecdh_callback

The underlying API SSL_CTX_set_tmp_ecdh_callback() was removed by
LibreSSL >= 2.6.1 and OpenSSL >= 1.1.0, in other words, it is not
supported by any non-EOL versions of OpenSSL.

The wrapper was initially implemented in Ruby 2.3 and has been
deprecated since Ruby/OpenSSL 2.0 (bundled with Ruby 2.4) with explicit
warning with rb_warn().

Author: rhenium

ext/openssl/extconf.rb

@@ -160,7 +160,6 @@ def find_openssl_library
 have_func("X509_STORE_up_ref")
 have_func("SSL_SESSION_up_ref")
 have_func("EVP_PKEY_up_ref")
-have_func("SSL_CTX_set_tmp_ecdh_callback(NULL, NULL)", "openssl/ssl.h") # removed
 have_func("SSL_CTX_set_min_proto_version(NULL, 0)", "openssl/ssl.h")
 have_func("SSL_CTX_get_security_level")
 have_func("X509_get0_notBefore")

ext/openssl/ossl_ssl.c

@@ -32,14 +32,14 @@ VALUE cSSLSocket;
 static VALUE eSSLErrorWaitReadable;
 static VALUE eSSLErrorWaitWritable;
 
-static ID id_call, ID_callback_state, id_tmp_dh_callback, id_tmp_ecdh_callback,
+static ID id_call, ID_callback_state, id_tmp_dh_callback,
 	  id_npn_protocols_encoded;
 static VALUE sym_exception, sym_wait_readable, sym_wait_writable;
 
 static ID id_i_cert_store, id_i_ca_file, id_i_ca_path, id_i_verify_mode,
 	  id_i_verify_depth, id_i_verify_callback, id_i_client_ca,
 	  id_i_renegotiation_cb, id_i_cert, id_i_key, id_i_extra_chain_cert,
-	  id_i_client_cert_cb, id_i_tmp_ecdh_callback, id_i_timeout,
+	  id_i_client_cert_cb, id_i_timeout,
 	  id_i_session_id_context, id_i_session_get_cb, id_i_session_new_cb,
 	  id_i_session_remove_cb, id_i_npn_select_cb, id_i_npn_protocols,
 	  id_i_alpn_select_cb, id_i_alpn_protocols, id_i_servername_cb,
@@ -231,8 +231,7 @@ ossl_client_cert_cb(SSL *ssl, X509 **x509, EVP_PKEY **pkey)
     return 1;
 }
 
-#if !defined(OPENSSL_NO_DH) || \
-    !defined(OPENSSL_NO_EC) && defined(HAVE_SSL_CTX_SET_TMP_ECDH_CALLBACK)
+#if !defined(OPENSSL_NO_DH)
 struct tmp_dh_callback_args {
     VALUE ssl_obj;
     ID id;
@@ -289,35 +288,6 @@ ossl_tmp_dh_callback(SSL *ssl, int is_export, int keylength)
 }
 #endif /* OPENSSL_NO_DH */
 
-#if !defined(OPENSSL_NO_EC) && defined(HAVE_SSL_CTX_SET_TMP_ECDH_CALLBACK)
-static EC_KEY *
-ossl_tmp_ecdh_callback(SSL *ssl, int is_export, int keylength)
-{
-    VALUE rb_ssl;
-    EVP_PKEY *pkey;
-    struct tmp_dh_callback_args args;
-    int state;
-
-    rb_ssl = (VALUE)SSL_get_ex_data(ssl, ossl_ssl_ex_ptr_idx);
-    args.ssl_obj = rb_ssl;
-    args.id = id_tmp_ecdh_callback;
-    args.is_export = is_export;
-    args.keylength = keylength;
-    args.type = EVP_PKEY_EC;
-
-    pkey = (EVP_PKEY *)rb_protect((VALUE (*)(VALUE))ossl_call_tmp_dh_callback,
-				  (VALUE)&args, &state);
-    if (state) {
-	rb_ivar_set(rb_ssl, ID_callback_state, INT2NUM(state));
-	return NULL;
-    }
-    if (!pkey)
-	return NULL;
-
-    return EVP_PKEY_get0_EC_KEY(pkey);
-}
-#endif
-
 static VALUE
 call_verify_certificate_identity(VALUE ctx_v)
 {
@@ -797,26 +767,6 @@ ossl_sslctx_setup(VALUE self)
     SSL_CTX_set_tmp_dh_callback(ctx, ossl_tmp_dh_callback);
 #endif
 
-#if !defined(OPENSSL_NO_EC)
-    /* We added SSLContext#tmp_ecdh_callback= in Ruby 2.3.0,
-     * but SSL_CTX_set_tmp_ecdh_callback() was removed in OpenSSL 1.1.0. */
-    if (RTEST(rb_attr_get(self, id_i_tmp_ecdh_callback))) {
-# if defined(HAVE_SSL_CTX_SET_TMP_ECDH_CALLBACK)
-	rb_warn("#tmp_ecdh_callback= is deprecated; use #ecdh_curves= instead");
-	SSL_CTX_set_tmp_ecdh_callback(ctx, ossl_tmp_ecdh_callback);
-#  if defined(HAVE_SSL_CTX_SET_ECDH_AUTO)
-	/* tmp_ecdh_callback and ecdh_auto conflict; OpenSSL ignores
-	 * tmp_ecdh_callback. So disable ecdh_auto. */
-	if (!SSL_CTX_set_ecdh_auto(ctx, 0))
-	    ossl_raise(eSSLError, "SSL_CTX_set_ecdh_auto");
-#  endif
-# else
-	ossl_raise(eSSLError, "OpenSSL does not support tmp_ecdh_callback; "
-		   "use #ecdh_curves= instead");
-# endif
-    }
-#endif /* OPENSSL_NO_EC */
-
 #ifdef HAVE_SSL_CTX_SET_POST_HANDSHAKE_AUTH
     SSL_CTX_set_post_handshake_auth(ctx, 1);
 #endif
@@ -2632,20 +2582,6 @@ Init_ossl_ssl(void)
      */
     rb_attr(cSSLContext, rb_intern("client_cert_cb"), 1, 1, Qfalse);
 
-#if !defined(OPENSSL_NO_EC) && defined(HAVE_SSL_CTX_SET_TMP_ECDH_CALLBACK)
-    /*
-     * A callback invoked when ECDH parameters are required.
-     *
-     * The callback is invoked with the Session for the key exchange, an
-     * flag indicating the use of an export cipher and the keylength
-     * required.
-     *
-     * The callback is deprecated. This does not work with recent versions of
-     * OpenSSL. Use OpenSSL::SSL::SSLContext#ecdh_curves= instead.
-     */
-    rb_attr(cSSLContext, rb_intern("tmp_ecdh_callback"), 1, 1, Qfalse);
-#endif
-
     /*
      * Sets the context in which a session can be reused.  This allows
      * sessions for multiple applications to be distinguished, for example, by
@@ -2997,7 +2933,6 @@ Init_ossl_ssl(void)
     sym_wait_writable = ID2SYM(rb_intern("wait_writable"));
 
     id_tmp_dh_callback = rb_intern("tmp_dh_callback");
-    id_tmp_ecdh_callback = rb_intern("tmp_ecdh_callback");
     id_npn_protocols_encoded = rb_intern("npn_protocols_encoded");
 
 #define DefIVarID(name) do \
@@ -3015,7 +2950,6 @@ Init_ossl_ssl(void)
     DefIVarID(key);
     DefIVarID(extra_chain_cert);
     DefIVarID(client_cert_cb);
-    DefIVarID(tmp_ecdh_callback);
     DefIVarID(timeout);
     DefIVarID(session_id_context);
     DefIVarID(session_get_cb);

test/openssl/test_ssl.rb

@@ -1603,30 +1603,6 @@ def test_connect_works_when_setting_dh_callback_to_nil
     end
   end
 
-  def test_tmp_ecdh_callback
-    pend "EC is disabled" unless defined?(OpenSSL::PKey::EC)
-    pend "tmp_ecdh_callback is not supported" unless \
-      OpenSSL::SSL::SSLContext.method_defined?(:tmp_ecdh_callback)
-    pend "LibreSSL 2.6 has broken SSL_CTX_set_tmp_ecdh_callback()" \
-      if libressl?(2, 6, 1)
-
-    EnvUtil.suppress_warning do # tmp_ecdh_callback is deprecated (2016-05)
-      called = false
-      ctx_proc = -> ctx {
-        ctx.ciphers = "DEFAULT:!kRSA:!kEDH"
-        ctx.tmp_ecdh_callback = -> (*args) {
-          called = true
-          OpenSSL::PKey::EC.new "prime256v1"
-        }
-      }
-      start_server(ctx_proc: ctx_proc) do |port|
-        server_connect(port) { |s|
-          assert called, "tmp_ecdh_callback should be called"
-        }
-      end
-    end
-  end
-
   def test_ecdh_curves
     pend "EC is disabled" unless defined?(OpenSSL::PKey::EC)