feat: add basic support for certificate_authorities (aws#4506)

tests/unit/s2n_cert_authorities_test.c

@@ -0,0 +1,215 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+#include "tls/extensions/s2n_cert_authorities.h"
+
+#include "crypto/s2n_rsa_pss.h"
+#include "s2n_test.h"
+#include "testlib/s2n_testlib.h"
+#include "tls/s2n_tls.h"
+#include "utils/s2n_bitmap.h"
+
+int s2n_parse_client_hello(struct s2n_connection *conn);
+
+int main(int argc, char **argv)
+{
+    BEGIN_TEST();
+
+    DEFER_CLEANUP(struct s2n_cert_chain_and_key *cert_chain = NULL,
+            s2n_cert_chain_and_key_ptr_free);
+    EXPECT_SUCCESS(s2n_test_cert_chain_and_key_new(&cert_chain,
+            S2N_DEFAULT_ECDSA_TEST_CERT_CHAIN, S2N_DEFAULT_ECDSA_TEST_PRIVATE_KEY));
+
+    s2n_extension_type_id temp_id = s2n_unsupported_extension;
+    EXPECT_SUCCESS(s2n_extension_supported_iana_value_to_id(
+            s2n_cert_authorities_extension.iana_value, &temp_id));
+    const s2n_extension_type_id ca_ext_id = temp_id;
+
+    /* Test: s2n_certificate_authorities_extension.send */
+    {
+        /* Test: writes whatever CA data is available */
+        {
+            const uint8_t ca_data[] = "these are my CAs";
+
+            DEFER_CLEANUP(struct s2n_config *config = s2n_config_new_minimal(), s2n_config_ptr_free);
+            EXPECT_SUCCESS(s2n_alloc(&config->cert_authorities, sizeof(ca_data)));
+            EXPECT_MEMCPY_SUCCESS(config->cert_authorities.data, ca_data, sizeof(ca_data));
+
+            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
+                    s2n_connection_ptr_free);
+            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));
+            conn->actual_protocol_version = S2N_TLS13;
+
+            DEFER_CLEANUP(struct s2n_stuffer output = { 0 }, s2n_stuffer_free);
+            EXPECT_SUCCESS(s2n_stuffer_growable_alloc(&output, 0));
+
+            EXPECT_SUCCESS(s2n_cert_authorities_extension.send(conn, &output));
+
+            uint16_t size = 0;
+            EXPECT_SUCCESS(s2n_stuffer_read_uint16(&output, &size));
+            EXPECT_EQUAL(size, sizeof(ca_data));
+            EXPECT_EQUAL(size, s2n_stuffer_data_available(&output));
+
+            uint8_t *data = s2n_stuffer_raw_read(&output, size);
+            EXPECT_NOT_NULL(data);
+            EXPECT_BYTEARRAY_EQUAL(data, ca_data, sizeof(ca_data));
+        };
+    };
+
+    /* Test: s2n_certificate_authorities_extension.should_send */
+    {
+        /* Test: do not send for TLS1.2 */
+        {
+            DEFER_CLEANUP(struct s2n_config *config = s2n_config_new_minimal(), s2n_config_ptr_free);
+            EXPECT_SUCCESS(s2n_alloc(&config->cert_authorities, 10));
+
+            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
+                    s2n_connection_ptr_free);
+            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));
+
+            DEFER_CLEANUP(struct s2n_stuffer output = { 0 }, s2n_stuffer_free);
+            EXPECT_SUCCESS(s2n_stuffer_growable_alloc(&output, 0));
+
+            conn->actual_protocol_version = S2N_TLS12;
+            EXPECT_SUCCESS(s2n_extension_send(&s2n_cert_authorities_extension,
+                    conn, &output));
+            EXPECT_EQUAL(s2n_stuffer_data_available(&output), 0);
+
+            conn->actual_protocol_version = S2N_TLS13;
+            EXPECT_SUCCESS(s2n_extension_send(&s2n_cert_authorities_extension,
+                    conn, &output));
+            EXPECT_NOT_EQUAL(s2n_stuffer_data_available(&output), 0);
+        };
+
+        /* Test: do not send if no CA data set */
+        {
+            DEFER_CLEANUP(struct s2n_config *config = s2n_config_new_minimal(), s2n_config_ptr_free);
+
+            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
+                    s2n_connection_ptr_free);
+            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));
+
+            EXPECT_FALSE(s2n_cert_authorities_extension.should_send(conn));
+
+            EXPECT_SUCCESS(s2n_alloc(&config->cert_authorities, 10));
+            EXPECT_TRUE(s2n_cert_authorities_extension.should_send(conn));
+
+            EXPECT_SUCCESS(s2n_free(&config->cert_authorities));
+            EXPECT_FALSE(s2n_cert_authorities_extension.should_send(conn));
+        };
+    };
+
+    /* Test: ClientHello extension ignored
+     *
+     *= https://tools.ietf.org/rfc/rfc8446#section-4.2.4
+     *= type=test
+     *# The client MAY send the "certificate_authorities" extension in the
+     *# ClientHello message.
+     */
+    if (s2n_is_tls13_fully_supported()) {
+        DEFER_CLEANUP(struct s2n_config *config = s2n_config_new_minimal(), s2n_config_ptr_free);
+        EXPECT_SUCCESS(s2n_config_set_unsafe_for_testing(config));
+        EXPECT_SUCCESS(s2n_config_add_cert_chain_and_key_to_store(config, cert_chain));
+        EXPECT_SUCCESS(s2n_config_set_cipher_preferences(config, "default_tls13"));
+        EXPECT_SUCCESS(s2n_alloc(&config->cert_authorities, 10));
+
+        DEFER_CLEANUP(struct s2n_connection *client = s2n_connection_new(S2N_CLIENT),
+                s2n_connection_ptr_free);
+        EXPECT_SUCCESS(s2n_connection_set_config(client, config));
+        EXPECT_SUCCESS(s2n_client_hello_send(client));
+        EXPECT_SUCCESS(s2n_parse_client_hello(client));
+        struct s2n_client_hello *client_hello = &client->client_hello;
+
+        DEFER_CLEANUP(struct s2n_connection *server = s2n_connection_new(S2N_SERVER),
+                s2n_connection_ptr_free);
+        EXPECT_SUCCESS(s2n_connection_set_config(server, config));
+        struct s2n_stuffer *input = &server->handshake.io;
+
+        /* Copy ClientHello, except extensions */
+        size_t size_without_extensions = client_hello->raw_message.size
+                - client_hello->extensions.raw.size
+                - sizeof(uint16_t) /* Extensions size */;
+        EXPECT_SUCCESS(s2n_stuffer_write_bytes(input,
+                client_hello->raw_message.data, size_without_extensions));
+
+        /* Save space for new extensions size */
+        struct s2n_stuffer_reservation extensions_size = { 0 };
+        EXPECT_SUCCESS(s2n_stuffer_reserve_uint16(input, &extensions_size));
+
+        /* Write the certificate_authorities extension.
+         * The client isn't allowed to write it, so use the server.
+         */
+        server->actual_protocol_version = S2N_TLS13;
+        EXPECT_SUCCESS(s2n_extension_send(&s2n_cert_authorities_extension,
+                server, input));
+
+        /* Write the rest of the extensions */
+        EXPECT_SUCCESS(s2n_stuffer_write(input, &client_hello->extensions.raw));
+
+        /* Update the extensions size */
+        EXPECT_SUCCESS(s2n_stuffer_write_vector_size(&extensions_size));
+
+        /* Server should be able to successfully receive the modified ClientHello */
+        EXPECT_SUCCESS(s2n_client_hello_recv(server));
+        EXPECT_TRUE(server->client_hello.parsed);
+        EXPECT_EQUAL(server->actual_protocol_version, S2N_TLS13);
+
+        s2n_parsed_extension *extension = &server->client_hello.extensions.parsed_extensions[ca_ext_id];
+        EXPECT_TRUE(extension->extension.size > 0);
+        EXPECT_FALSE(extension->processed);
+        EXPECT_EQUAL(extension->extension_type, s2n_cert_authorities_extension.iana_value);
+    };
+
+    /* Self-talk test: CertificateRequest extension parsed
+     *
+     *= https://tools.ietf.org/rfc/rfc8446#section-4.2.4
+     *= type=test
+     *# The server MAY send it in the CertificateRequest message.
+     **/
+    if (s2n_is_tls13_fully_supported()) {
+        DEFER_CLEANUP(struct s2n_config *config = s2n_config_new_minimal(), s2n_config_ptr_free);
+        EXPECT_SUCCESS(s2n_config_set_unsafe_for_testing(config));
+        EXPECT_SUCCESS(s2n_config_add_cert_chain_and_key_to_store(config, cert_chain));
+        EXPECT_SUCCESS(s2n_config_set_cipher_preferences(config, "default_tls13"));
+        EXPECT_SUCCESS(s2n_config_set_client_auth_type(config, S2N_CERT_AUTH_OPTIONAL));
+        EXPECT_SUCCESS(s2n_alloc(&config->cert_authorities, 10));
+
+        DEFER_CLEANUP(struct s2n_connection *client = s2n_connection_new(S2N_CLIENT),
+                s2n_connection_ptr_free);
+        EXPECT_SUCCESS(s2n_connection_set_config(client, config));
+
+        DEFER_CLEANUP(struct s2n_connection *server = s2n_connection_new(S2N_SERVER),
+                s2n_connection_ptr_free);
+        EXPECT_SUCCESS(s2n_connection_set_config(server, config));
+
+        DEFER_CLEANUP(struct s2n_test_io_pair io_pair = { 0 }, s2n_io_pair_close);
+        EXPECT_SUCCESS(s2n_io_pair_init_non_blocking(&io_pair));
+        EXPECT_SUCCESS(s2n_connections_set_io_pair(client, server, &io_pair));
+
+        EXPECT_SUCCESS(s2n_negotiate_test_server_and_client(server, client));
+        EXPECT_EQUAL(server->actual_protocol_version, S2N_TLS13);
+        EXPECT_TRUE(IS_CLIENT_AUTH_HANDSHAKE(server));
+
+        /* Server sent extension */
+        EXPECT_TRUE(S2N_CBIT_TEST(server->extension_requests_sent, ca_ext_id));
+        EXPECT_FALSE(S2N_CBIT_TEST(server->extension_requests_received, ca_ext_id));
+
+        /* Client received extension */
+        EXPECT_FALSE(S2N_CBIT_TEST(client->extension_requests_sent, ca_ext_id));
+        EXPECT_TRUE(S2N_CBIT_TEST(client->extension_requests_received, ca_ext_id));
+    };
+
+    END_TEST();
+}

tests/unit/s2n_server_cert_request_test.c

@@ -60,7 +60,7 @@ int main(int argc, char **argv)
         EXPECT_NOT_NULL(server_conn = s2n_connection_new(S2N_SERVER));
         EXPECT_SUCCESS(s2n_connection_set_config(server_conn, server_config));
 
-        s2n_cert_req_send(server_conn);
+        EXPECT_SUCCESS(s2n_cert_req_send(server_conn));
         struct s2n_stuffer *in = &server_conn->handshake.io;
         uint8_t cert_types_len = 0;
 
@@ -88,7 +88,7 @@ int main(int argc, char **argv)
         EXPECT_SUCCESS(s2n_connection_set_config(server_conn, server_config));
         EXPECT_SUCCESS(s2n_config_enable_cert_req_dss_legacy_compat(server_config));
 
-        s2n_cert_req_send(server_conn);
+        EXPECT_SUCCESS(s2n_cert_req_send(server_conn));
         struct s2n_stuffer *in = &server_conn->handshake.io;
         uint8_t cert_types_len = 0;
 
@@ -105,6 +105,78 @@ int main(int argc, char **argv)
         EXPECT_SUCCESS(s2n_connection_free(server_conn));
     };
 
+    /* Test: certificate_authorities supported */
+    {
+        /* Test: no cert_authorities sent by default */
+        {
+            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
+                    s2n_connection_ptr_free);
+            EXPECT_NOT_NULL(conn);
+            conn->actual_protocol_version = S2N_TLS12;
+
+            DEFER_CLEANUP(struct s2n_config *config = s2n_config_new(),
+                    s2n_config_ptr_free);
+            EXPECT_NOT_NULL(config);
+            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));
+
+            EXPECT_SUCCESS(s2n_cert_req_send(conn));
+            struct s2n_stuffer *output = &conn->handshake.io;
+
+            uint8_t cert_types_len = 0;
+            EXPECT_SUCCESS(s2n_stuffer_read_uint8(output, &cert_types_len));
+            EXPECT_TRUE(cert_types_len > 0);
+            EXPECT_SUCCESS(s2n_stuffer_skip_read(output, cert_types_len));
+
+            uint16_t sig_algs_len = 0;
+            EXPECT_SUCCESS(s2n_stuffer_read_uint16(output, &sig_algs_len));
+            EXPECT_TRUE(sig_algs_len > 0);
+            EXPECT_SUCCESS(s2n_stuffer_skip_read(output, sig_algs_len));
+
+            uint16_t cert_authorities_len = 0;
+            EXPECT_SUCCESS(s2n_stuffer_read_uint16(output, &cert_authorities_len));
+            EXPECT_EQUAL(cert_authorities_len, 0);
+
+            EXPECT_EQUAL(s2n_stuffer_data_available(output), 0);
+        };
+
+        /* Test: cert_authorities sent if configured */
+        {
+            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
+                    s2n_connection_ptr_free);
+            EXPECT_NOT_NULL(conn);
+
+            DEFER_CLEANUP(struct s2n_config *config = s2n_config_new(),
+                    s2n_config_ptr_free);
+            EXPECT_NOT_NULL(config);
+            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));
+
+            /* If we use TLS1.1 instead of TLS1.2, we don't need to worry about
+             * skipping the signature algorithms.
+             */
+            conn->actual_protocol_version = S2N_TLS11;
+
+            const uint8_t ca_data[] = "these are my CAs";
+            EXPECT_SUCCESS(s2n_alloc(&config->cert_authorities, sizeof(ca_data)));
+            EXPECT_MEMCPY_SUCCESS(config->cert_authorities.data, ca_data, sizeof(ca_data));
+
+            EXPECT_SUCCESS(s2n_cert_req_send(conn));
+            struct s2n_stuffer *output = &conn->handshake.io;
+
+            uint8_t cert_types_len = 0;
+            EXPECT_SUCCESS(s2n_stuffer_read_uint8(output, &cert_types_len));
+            EXPECT_SUCCESS(s2n_stuffer_skip_read(output, cert_types_len));
+
+            uint16_t cert_authorities_len = 0;
+            EXPECT_SUCCESS(s2n_stuffer_read_uint16(output, &cert_authorities_len));
+            EXPECT_EQUAL(cert_authorities_len, sizeof(ca_data));
+
+            uint8_t *cert_authorities_data = s2n_stuffer_raw_read(output, cert_authorities_len);
+            EXPECT_NOT_NULL(cert_authorities_data);
+            EXPECT_BYTEARRAY_EQUAL(cert_authorities_data, ca_data, sizeof(ca_data));
+
+            EXPECT_EQUAL(s2n_stuffer_data_available(output), 0);
+        };
+    };
+
     END_TEST();
-    return 0;
 }

tls/extensions/s2n_cert_authorities.c

@@ -0,0 +1,54 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+#include "tls/extensions/s2n_cert_authorities.h"
+
+#include "utils/s2n_safety.h"
+
+int s2n_cert_authorities_send(struct s2n_connection *conn, struct s2n_stuffer *out)
+{
+    POSIX_ENSURE_REF(conn);
+    POSIX_ENSURE_REF(conn->config);
+    POSIX_ENSURE_EQ(conn->mode, S2N_SERVER);
+    struct s2n_blob *cert_authorities = &conn->config->cert_authorities;
+    POSIX_GUARD(s2n_stuffer_write_uint16(out, cert_authorities->size));
+    POSIX_GUARD(s2n_stuffer_write(out, cert_authorities));
+    return S2N_SUCCESS;
+}
+
+static bool s2n_cert_authorities_should_send(struct s2n_connection *conn)
+{
+    return conn && conn->config && conn->config->cert_authorities.size > 0;
+}
+
+const s2n_extension_type s2n_cert_authorities_extension = {
+    .iana_value = TLS_EXTENSION_CERT_AUTHORITIES,
+    .minimum_version = S2N_TLS13,
+    .is_response = false,
+    .send = s2n_cert_authorities_send,
+    .should_send = s2n_cert_authorities_should_send,
+    /* s2n-tls supports sending the extension, but does not support parsing it.
+     * If received, the extension is ignored.
+     *
+     *= https://tools.ietf.org/rfc/rfc8446#section-4.2.4
+     *= type=exception
+     *= reason=Extension ignored when received - No customer use case
+     *# The "certificate_authorities" extension is used to indicate the
+     *# certificate authorities (CAs) which an endpoint supports and which
+     *# SHOULD be used by the receiving endpoint to guide certificate
+     *# selection.
+     */
+    .recv = s2n_extension_recv_noop,
+    .if_missing = s2n_extension_noop_if_missing,
+};

tls/extensions/s2n_cert_authorities.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+#pragma once
+
+#include "stuffer/s2n_stuffer.h"
+#include "tls/extensions/s2n_extension_type.h"
+#include "tls/s2n_connection.h"
+
+extern const s2n_extension_type s2n_cert_authorities_extension;
+
+int s2n_cert_authorities_send(struct s2n_connection *conn, struct s2n_stuffer *out);