Fix a bug where framefmt serialize returns a wrong ciphertext size

source/framefmt.c

@@ -241,10 +241,9 @@ int aws_cryptosdk_serialize_frame(
     // lets us avoid having to pass in a redundant argument, avoids needing to
     // take a branch in serde_framed, and does not impact the serialized
     // output.
-    state.max_frame_size = plaintext_size;
-    state.plaintext_size = plaintext_size;
-    // Currently all supported algorithms have plaintext = ciphertext size
-    state.ciphertext_size = plaintext_size;
+    state.max_frame_size  = plaintext_size;
+    state.plaintext_size  = plaintext_size;
+    state.ciphertext_size = 0;
 
     state.alg_props = alg_props;
     state.u.buffer  = *ciphertext_buf;

tests/CMakeLists.txt

@@ -88,6 +88,7 @@ aws_add_test(header ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite head
 aws_add_test(materials ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite materials)
 aws_add_test(enc_ctx ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite enc_ctx)
 aws_add_test(encrypt ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite encrypt)
+aws_add_test(framefmt ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite framefmt)
 aws_add_test(hkdf ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite hkdf)
 aws_add_test(raw_aes_keyring ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite raw_aes_keyring)
 aws_add_test(raw_rsa_keyring ${VALGRIND} ${CMAKE_CURRENT_BINARY_DIR}/unit-test-suite raw_rsa_keyring)

tests/unit/runner.c

@@ -30,6 +30,7 @@ struct test_case *test_groups[] = { header_test_cases,
                                     materials_test_cases,
                                     enc_ctx_test_cases,
                                     encrypt_test_cases,
+                                    framefmt_test_cases,
                                     hkdf_test_cases,
                                     raw_aes_keyring_decrypt_test_cases,
                                     raw_aes_keyring_encrypt_test_cases,

tests/unit/t_framefmt.c

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2019 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 <aws/cryptosdk/default_cmm.h>
+#include <aws/cryptosdk/private/cipher.h>
+#include <aws/cryptosdk/private/framefmt.h>
+#include <aws/cryptosdk/session.h>
+#include <stdlib.h>
+#include "counting_keyring.h"
+#include "testing.h"
+#include "testutil.h"
+#include "zero_keyring.h"
+
+int test_serialize_return_ciphertext_size() {
+    // Arguments to the function
+    size_t ciphertext_buf_capacity = 10000;
+    size_t plaintext_size          = 100;
+    enum aws_cryptosdk_alg_id id   = ALG_AES128_GCM_IV12_TAG16_HKDF_SHA256_ECDSA_P256;
+
+    struct aws_allocator *alloc = aws_default_allocator();
+
+    // Alocate the frame
+    struct aws_cryptosdk_frame out_frame;
+    out_frame.type            = FRAME_TYPE_SINGLE;
+    out_frame.sequence_number = 1;
+
+    // Allocate the byte buffer
+    struct aws_byte_buf ciphertext_buf;
+    TEST_ASSERT_SUCCESS(aws_byte_buf_init(&ciphertext_buf, alloc, ciphertext_buf_capacity));
+
+    // Increase the length of the ciphertext buffer to simulate already having data in it
+    ciphertext_buf.len += 1000;
+
+    // Allocate and initialize the alg_properties
+    const struct aws_cryptosdk_alg_properties *alg_props = aws_cryptosdk_alg_props(id);
+    size_t ciphertext_size;
+
+    size_t old_ciphertext_buf_len = ciphertext_buf.len;
+
+    TEST_ASSERT_SUCCESS(
+        aws_cryptosdk_serialize_frame(&out_frame, &ciphertext_size, plaintext_size, &ciphertext_buf, alg_props));
+    // Assert that the returned size is correct
+    TEST_ASSERT(old_ciphertext_buf_len + ciphertext_size == ciphertext_buf.len);
+
+    aws_byte_buf_clean_up(&ciphertext_buf);
+
+    return 0;
+}
+
+struct test_case framefmt_test_cases[] = {
+    { "framefmt", "test_serialize_return_ciphertext_size", test_serialize_return_ciphertext_size }, { NULL }
+};

tests/unit/testing.h

@@ -26,6 +26,7 @@ extern struct test_case cipher_test_cases[];
 extern struct test_case materials_test_cases[];
 extern struct test_case enc_ctx_test_cases[];
 extern struct test_case encrypt_test_cases[];
+extern struct test_case framefmt_test_cases[];
 extern struct test_case hkdf_test_cases[];
 extern struct test_case raw_aes_keyring_provider_info_test_cases[];
 extern struct test_case raw_aes_keyring_decrypt_test_cases[];