/*
 * 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 <stdio.h>
#include <string.h>

#include "api/s2n.h"
#include "crypto/s2n_cipher.h"
#include "crypto/s2n_hmac.h"
#include "s2n_test.h"
#include "stuffer/s2n_stuffer.h"
#include "testlib/s2n_testlib.h"
#include "tls/s2n_cipher_suites.h"
#include "tls/s2n_prf.h"
#include "tls/s2n_record.h"
#include "utils/s2n_random.h"

#define ONE_BLOCK                   1024
#define ONE_HUNDRED_K               100000
#define RECORD_SIZE_HIGH_BYTE_ORDER 3
#define RECORD_SIZE_LOW_BYTE_ORDER  4
#define BYTE_SHIFT                  8
#define RECORD_SIZE(data)           ((data[RECORD_SIZE_HIGH_BYTE_ORDER] << BYTE_SHIFT) | data[RECORD_SIZE_LOW_BYTE_ORDER])

#define EXPECT_LESS_THAN_EQUAL(p1, p2) EXPECT_TRUE((p1) <= (p2))

static int destroy_server_keys(struct s2n_connection *server_conn)
{
    POSIX_GUARD(server_conn->initial->cipher_suite->record_alg->cipher->destroy_key(&server_conn->initial->server_key));
    POSIX_GUARD(server_conn->initial->cipher_suite->record_alg->cipher->destroy_key(&server_conn->initial->client_key));

    return S2N_SUCCESS;
}

static int setup_server_keys(struct s2n_connection *server_conn, struct s2n_blob *key)
{
    POSIX_GUARD(server_conn->initial->cipher_suite->record_alg->cipher->init(&server_conn->initial->server_key));
    POSIX_GUARD(server_conn->initial->cipher_suite->record_alg->cipher->init(&server_conn->initial->client_key));
    POSIX_GUARD(server_conn->initial->cipher_suite->record_alg->cipher->set_encryption_key(&server_conn->initial->server_key, key));
    POSIX_GUARD(server_conn->initial->cipher_suite->record_alg->cipher->set_decryption_key(&server_conn->initial->client_key, key));

    return S2N_SUCCESS;
}

int main(int argc, char **argv)
{
    BEGIN_TEST();
    EXPECT_SUCCESS(s2n_disable_tls13_in_test());

    uint8_t mac_key[] = "sample mac key";

    uint8_t random_data[S2N_LARGE_RECORD_LENGTH + 1];
    struct s2n_blob r = { 0 };
    EXPECT_SUCCESS(s2n_blob_init(&r, random_data, sizeof(random_data)));
    EXPECT_OK(s2n_get_public_random_data(&r));

    uint8_t aes128_key[] = "123456789012345";
    struct s2n_blob aes128 = { 0 };
    EXPECT_SUCCESS(s2n_blob_init(&aes128, aes128_key, sizeof(aes128_key)));

    /* Test record sizes with s2n_record_write */
    {
        DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
                s2n_connection_ptr_free);
        EXPECT_NOT_NULL(conn);

        /* Client and server are in sync */
        conn->server = conn->secure;
        conn->client = conn->secure;

        /* test the AES128 cipher with a SHA1 hash */
        conn->secure->cipher_suite->record_alg = &s2n_record_alg_aes128_sha;
        EXPECT_SUCCESS(conn->secure->cipher_suite->record_alg->cipher->init(&conn->secure->server_key));
        EXPECT_SUCCESS(conn->secure->cipher_suite->record_alg->cipher->init(&conn->secure->client_key));
        EXPECT_SUCCESS(conn->secure->cipher_suite->record_alg->cipher->set_encryption_key(&conn->secure->server_key, &aes128));
        EXPECT_SUCCESS(conn->secure->cipher_suite->record_alg->cipher->set_decryption_key(&conn->secure->client_key, &aes128));
        EXPECT_SUCCESS(s2n_hmac_init(&conn->secure->client_record_mac, S2N_HMAC_SHA1, mac_key, sizeof(mac_key)));
        EXPECT_SUCCESS(s2n_hmac_init(&conn->secure->server_record_mac, S2N_HMAC_SHA1, mac_key, sizeof(mac_key)));
        conn->actual_protocol_version = S2N_TLS11;

        /* Test that different modes allows for different fragment/payload sizes.
         * Record overheads (IV, HMAC, padding) do not count towards these size */
        const int small_payload = S2N_SMALL_FRAGMENT_LENGTH;
        const int large_payload = S2N_LARGE_FRAGMENT_LENGTH;
        const int medium_payload = S2N_DEFAULT_FRAGMENT_LENGTH;
        struct s2n_blob fragment = r;

        /* Check the default: medium records */
        fragment.size = medium_payload;
        EXPECT_SUCCESS(s2n_stuffer_wipe(&conn->out));
        EXPECT_OK(s2n_record_write(conn, TLS_APPLICATION_DATA, &fragment));

        /* Check explicitly small records */
        fragment.size = small_payload;
        EXPECT_SUCCESS(s2n_connection_prefer_low_latency(conn));
        EXPECT_SUCCESS(s2n_stuffer_wipe(&conn->out));
        EXPECT_OK(s2n_record_write(conn, TLS_APPLICATION_DATA, &fragment));

        /* Check explicitly large records */
        fragment.size = large_payload;
        EXPECT_SUCCESS(s2n_connection_prefer_throughput(conn));
        EXPECT_SUCCESS(s2n_stuffer_wipe(&conn->out));
        EXPECT_OK(s2n_record_write(conn, TLS_APPLICATION_DATA, &fragment));

        /* Clean up */
        conn->secure->cipher_suite->record_alg = &s2n_record_alg_null; /* restore mutated null cipher suite */
        EXPECT_SUCCESS(conn->secure->cipher_suite->record_alg->cipher->destroy_key(&conn->secure->server_key));
        EXPECT_SUCCESS(conn->secure->cipher_suite->record_alg->cipher->destroy_key(&conn->secure->client_key));
    };

    /* Test s2n_record_max_write_payload_size() have proper checks in place */
    {
        struct s2n_connection *server_conn;
        EXPECT_NOT_NULL(server_conn = s2n_connection_new(S2N_SERVER));

        /* we deal with the default null cipher suite for now, as it makes reasoning
         * about easier s2n_record_max_write_payload_size(), as it incur 0 overheads */
        uint16_t size;
        server_conn->max_outgoing_fragment_length = ONE_BLOCK;
        EXPECT_OK(s2n_record_max_write_payload_size(server_conn, &size));
        EXPECT_EQUAL(size, ONE_BLOCK);

        /* Trigger an overlarge payload by setting a maximum uint16_t value to max fragment length */
        server_conn->max_outgoing_fragment_length = UINT16_MAX;
        /* Check that we are bound by S2N_TLS_MAXIMUM_FRAGMENT_LENGTH */
        EXPECT_OK(s2n_record_max_write_payload_size(server_conn, &size));
        EXPECT_EQUAL(size, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH);

        /* trigger a payload that is under the limits */
        server_conn->max_outgoing_fragment_length = 0;
        EXPECT_ERROR_WITH_ERRNO(s2n_record_max_write_payload_size(server_conn, &size), S2N_ERR_FRAGMENT_LENGTH_TOO_SMALL);

        /* Test boundary cases */

        /* This is the theoretical maximum mfl allowed */
        server_conn->max_outgoing_fragment_length = S2N_TLS_MAXIMUM_FRAGMENT_LENGTH;
        EXPECT_OK(s2n_record_max_write_payload_size(server_conn, &size));
        EXPECT_EQUAL(size, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH);

        /* MFL over limit is not allowed, but size is reduced to S2N_TLS_MAXIMUM_FRAGMENT_LENGTH*/
        server_conn->max_outgoing_fragment_length++;
        EXPECT_OK(s2n_record_max_write_payload_size(server_conn, &size));
        EXPECT_EQUAL(size, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH);

        /* Test against different cipher suites */
        server_conn->actual_protocol_version = S2N_TLS13;
        server_conn->server->cipher_suite = &s2n_tls13_aes_128_gcm_sha256;
        server_conn->max_outgoing_fragment_length = ONE_BLOCK;
        EXPECT_OK(s2n_record_max_write_payload_size(server_conn, &size));
        EXPECT_EQUAL(size, ONE_BLOCK); /* Verify size matches exactly specified max fragment length */

        EXPECT_SUCCESS(s2n_connection_free(server_conn));
    };

    /* Test s2n_record_max_write_payload_size with custom send buffer size */
    {
        DEFER_CLEANUP(struct s2n_config *config = s2n_config_new(), s2n_config_ptr_free);
        EXPECT_NOT_NULL(config);

        /* Min buffer size */
        {
            const uint32_t buffer_size = S2N_TLS_MAX_RECORD_LEN_FOR(S2N_MIN_SEND_BUFFER_FRAGMENT_SIZE);
            EXPECT_SUCCESS(s2n_config_set_send_buffer_size(config, buffer_size));

            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER), s2n_connection_ptr_free);
            EXPECT_NOT_NULL(conn);
            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));

            uint16_t size = 0;
            EXPECT_OK(s2n_record_max_write_payload_size(conn, &size));
            EXPECT_EQUAL(size, S2N_MIN_SEND_BUFFER_FRAGMENT_SIZE);
        };

        /* Small buffer size */
        {
            const uint32_t frag_len = 1000;
            const uint32_t buffer_size = S2N_TLS_MAX_RECORD_LEN_FOR(frag_len);
            EXPECT_SUCCESS(s2n_config_set_send_buffer_size(config, buffer_size));

            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER), s2n_connection_ptr_free);
            EXPECT_NOT_NULL(conn);
            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));

            uint16_t size = 0;
            EXPECT_OK(s2n_record_max_write_payload_size(conn, &size));
            EXPECT_EQUAL(size, frag_len);
        };

        /* Buffer exactly fits one record */
        {
            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER), s2n_connection_ptr_free);
            EXPECT_NOT_NULL(conn);

            const uint32_t frag_len = conn->max_outgoing_fragment_length;
            const uint32_t buffer_size = S2N_TLS_MAX_RECORD_LEN_FOR(frag_len);
            EXPECT_SUCCESS(s2n_config_set_send_buffer_size(config, buffer_size));
            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));

            uint16_t size = 0;
            EXPECT_OK(s2n_record_max_write_payload_size(conn, &size));
            EXPECT_EQUAL(size, frag_len);
        };

        /* Buffer larger than one record */
        {
            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER), s2n_connection_ptr_free);
            EXPECT_NOT_NULL(conn);

            const uint32_t frag_len = conn->max_outgoing_fragment_length + 10;
            const uint32_t buffer_size = S2N_TLS_MAX_RECORD_LEN_FOR(frag_len);
            EXPECT_SUCCESS(s2n_config_set_send_buffer_size(config, buffer_size));
            EXPECT_SUCCESS(s2n_connection_set_config(conn, config));

            uint16_t size = 0;
            EXPECT_OK(s2n_record_max_write_payload_size(conn, &size));
            EXPECT_EQUAL(size, conn->max_outgoing_fragment_length);
        };
    };

    /* Test s2n_record_min_write_payload_size() */
    {
        struct s2n_connection *server_conn;
        EXPECT_NOT_NULL(server_conn = s2n_connection_new(S2N_SERVER));

        uint16_t size = 0;
        const int RECORD_SIZE_LESS_OVERHEADS = 1415;

        EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
        EXPECT_EQUAL(RECORD_SIZE_LESS_OVERHEADS, size);

        const int MIN_SIZE = RECORD_SIZE_LESS_OVERHEADS + S2N_TLS_RECORD_HEADER_LENGTH;

        /* CBC */
        {
            EXPECT_SUCCESS(s2n_connection_wipe(server_conn));
            EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));
            server_conn->actual_protocol_version = S2N_TLS11;
            server_conn->initial->cipher_suite->record_alg = &s2n_record_alg_3des_sha;
            uint8_t des3_key[] = "12345678901234567890123";
            struct s2n_blob des3 = { 0 };
            EXPECT_SUCCESS(s2n_blob_init(&des3, des3_key, sizeof(des3_key)));
            server_conn->server = server_conn->secure;
            EXPECT_SUCCESS(server_conn->secure->cipher_suite->record_alg->cipher->init(&server_conn->secure->server_key));
            EXPECT_SUCCESS(server_conn->secure->cipher_suite->record_alg->cipher->init(&server_conn->secure->client_key));
            EXPECT_SUCCESS(server_conn->secure->cipher_suite->record_alg->cipher->set_encryption_key(&server_conn->secure->server_key, &des3));
            EXPECT_SUCCESS(server_conn->secure->cipher_suite->record_alg->cipher->set_decryption_key(&server_conn->secure->client_key, &des3));
            EXPECT_SUCCESS(s2n_hmac_init(&server_conn->secure->server_record_mac, S2N_HMAC_SHA1, mac_key, sizeof(mac_key)));

            EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
            r.size = size;
            const int after_overheads = RECORD_SIZE_LESS_OVERHEADS - RECORD_SIZE_LESS_OVERHEADS % 8; /* rounded down to cbc block size (8) */
            const uint16_t PADDING_LENGTH_BYTE = 1;
            const uint16_t RECORD_IV_SIZE = 8;
            const uint16_t HMAC_DIGEST = 20;
            EXPECT_EQUAL(size, after_overheads - HMAC_DIGEST - RECORD_IV_SIZE - PADDING_LENGTH_BYTE);

            EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &r));
            const uint16_t wire_size = s2n_stuffer_data_available(&server_conn->out);
            EXPECT_LESS_THAN_EQUAL(wire_size, MIN_SIZE);
            EXPECT_EQUAL(RECORD_SIZE(server_conn->out.blob.data), wire_size - S2N_TLS_RECORD_HEADER_LENGTH);
        };

        /* AEAD */
        {
            EXPECT_SUCCESS(s2n_connection_wipe(server_conn));
            EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

            server_conn->initial->cipher_suite->record_alg = &s2n_record_alg_aes128_gcm;
            EXPECT_SUCCESS(setup_server_keys(server_conn, &aes128));

            EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
            r.size = size;
            const uint16_t IV = 8;
            const uint16_t TAG = 16;
            EXPECT_EQUAL(size, RECORD_SIZE_LESS_OVERHEADS - IV - TAG);

            EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &r));
            const uint16_t wire_size = s2n_stuffer_data_available(&server_conn->out);
            EXPECT_LESS_THAN_EQUAL(wire_size, MIN_SIZE);
            EXPECT_EQUAL(RECORD_SIZE(server_conn->out.blob.data), wire_size - S2N_TLS_RECORD_HEADER_LENGTH);
        };

        /* TLS1.3 AEAD */
        {
            EXPECT_SUCCESS(destroy_server_keys(server_conn));
            EXPECT_SUCCESS(s2n_connection_wipe(server_conn));
            EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

            server_conn->actual_protocol_version = S2N_TLS13;
            server_conn->initial->cipher_suite->record_alg = &s2n_tls13_record_alg_aes128_gcm;
            EXPECT_SUCCESS(setup_server_keys(server_conn, &aes128));

            EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
            r.size = size;
            const uint16_t IV = 0;
            const uint16_t TAG = 16;
            EXPECT_EQUAL(size, RECORD_SIZE_LESS_OVERHEADS - IV - TAG - S2N_TLS_CONTENT_TYPE_LENGTH);

            EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &r));
            const uint16_t wire_size = s2n_stuffer_data_available(&server_conn->out);
            EXPECT_LESS_THAN_EQUAL(wire_size, MIN_SIZE);
            EXPECT_EQUAL(RECORD_SIZE(server_conn->out.blob.data), wire_size - S2N_TLS_RECORD_HEADER_LENGTH);
        };

        /* chacha20 */
        if (s2n_chacha20_poly1305.is_available()) {
            EXPECT_SUCCESS(destroy_server_keys(server_conn));
            EXPECT_SUCCESS(s2n_connection_wipe(server_conn));

            server_conn->initial->cipher_suite->record_alg = &s2n_record_alg_chacha20_poly1305;
            uint8_t chacha20_poly1305_key_data[] = "1234567890123456789012345678901";
            struct s2n_blob chacha20_poly1305_key = { 0 };
            EXPECT_SUCCESS(s2n_blob_init(&chacha20_poly1305_key, chacha20_poly1305_key_data, sizeof(chacha20_poly1305_key_data)));

            EXPECT_SUCCESS(setup_server_keys(server_conn, &chacha20_poly1305_key));
            EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

            EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
            EXPECT_EQUAL(size, RECORD_SIZE_LESS_OVERHEADS - S2N_TLS_CHACHA20_POLY1305_EXPLICIT_IV_LEN - S2N_TLS_GCM_TAG_LEN);
            r.size = size;

            EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &r));
            const uint16_t wire_size = s2n_stuffer_data_available(&server_conn->out);
            EXPECT_LESS_THAN_EQUAL(wire_size, MIN_SIZE);
            EXPECT_EQUAL(RECORD_SIZE(server_conn->out.blob.data), wire_size - S2N_TLS_RECORD_HEADER_LENGTH);
        }

        /* TLS1.3 chacha20 */
        if (s2n_chacha20_poly1305.is_available()) {
            EXPECT_SUCCESS(destroy_server_keys(server_conn));
            EXPECT_SUCCESS(s2n_connection_wipe(server_conn));

            server_conn->actual_protocol_version = S2N_TLS13;
            server_conn->initial->cipher_suite->record_alg = &s2n_tls13_record_alg_chacha20_poly1305;
            uint8_t chacha20_poly1305_key_data[] = "1234567890123456789012345678901";
            struct s2n_blob chacha20_poly1305_key = { 0 };
            EXPECT_SUCCESS(s2n_blob_init(&chacha20_poly1305_key, chacha20_poly1305_key_data, sizeof(chacha20_poly1305_key_data)));

            EXPECT_SUCCESS(setup_server_keys(server_conn, &chacha20_poly1305_key));
            EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

            EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
            EXPECT_EQUAL(size, RECORD_SIZE_LESS_OVERHEADS - S2N_TLS_CHACHA20_POLY1305_EXPLICIT_IV_LEN - S2N_TLS_GCM_TAG_LEN - S2N_TLS_CONTENT_TYPE_LENGTH);
            r.size = size;

            EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &r));
            const uint16_t wire_size = s2n_stuffer_data_available(&server_conn->out);
            EXPECT_LESS_THAN_EQUAL(wire_size, MIN_SIZE);
            EXPECT_EQUAL(RECORD_SIZE(server_conn->out.blob.data), wire_size - S2N_TLS_RECORD_HEADER_LENGTH);
        }

        /* composite */
        if (s2n_aes128_sha.is_available() && s2n_aes128_sha256.is_available()) {
            EXPECT_SUCCESS(destroy_server_keys(server_conn));
            EXPECT_SUCCESS(s2n_connection_wipe(server_conn));
            EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

            server_conn->initial->cipher_suite->record_alg = &s2n_record_alg_aes128_sha_composite;
            server_conn->actual_protocol_version = S2N_TLS11;
            uint8_t mac_key_sha[20] = "server key shaserve";
            EXPECT_SUCCESS(server_conn->initial->cipher_suite->record_alg->cipher->set_encryption_key(&server_conn->initial->server_key, &aes128));
            EXPECT_SUCCESS(server_conn->initial->cipher_suite->record_alg->cipher->set_decryption_key(&server_conn->initial->client_key, &aes128));
            EXPECT_SUCCESS(server_conn->initial->cipher_suite->record_alg->cipher->io.comp.set_mac_write_key(&server_conn->initial->server_key, mac_key_sha, sizeof(mac_key_sha)));
            EXPECT_SUCCESS(server_conn->initial->cipher_suite->record_alg->cipher->io.comp.set_mac_write_key(&server_conn->initial->client_key, mac_key_sha, sizeof(mac_key_sha)));

            EXPECT_OK(s2n_record_min_write_payload_size(server_conn, &size));
            const uint16_t COMPOSITE_BLOCK_SIZE = 16;
            const uint16_t COMPOSITE_DIGEST_LENGTH = 20;
            const uint16_t COMPOSITE_PADDING_LENGTH = 1;
            const uint16_t size_aligned_to_block = RECORD_SIZE_LESS_OVERHEADS - RECORD_SIZE_LESS_OVERHEADS % COMPOSITE_BLOCK_SIZE - COMPOSITE_DIGEST_LENGTH - COMPOSITE_PADDING_LENGTH;
            const uint16_t explicit_iv_len = 16;
            const uint16_t size_after_overheads = size_aligned_to_block - explicit_iv_len;
            EXPECT_EQUAL(size, size_after_overheads);
            r.size = size;

            EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &r));
            const uint16_t wire_size = s2n_stuffer_data_available(&server_conn->out);
            EXPECT_LESS_THAN_EQUAL(wire_size, MIN_SIZE);
            EXPECT_EQUAL(RECORD_SIZE(server_conn->out.blob.data), wire_size - S2N_TLS_RECORD_HEADER_LENGTH);
        }

        r.size = sizeof(random_data);
        EXPECT_SUCCESS(s2n_connection_free(server_conn));
    };

    /* Test large fragment/record sending for TLS 1.3 */
    {
        struct s2n_connection *server_conn;
        EXPECT_NOT_NULL(server_conn = s2n_connection_new(S2N_SERVER));
        struct s2n_cipher_suite *cipher_suite = &s2n_tls13_aes_128_gcm_sha256;
        server_conn->actual_protocol_version = S2N_TLS13;
        server_conn->server->cipher_suite = cipher_suite;

        struct s2n_session_key *session_key = &server_conn->server->server_key;
        uint8_t *implicit_iv = server_conn->server->server_implicit_iv;

        /* init record algorithm */
        EXPECT_SUCCESS(cipher_suite->record_alg->cipher->init(session_key));
        S2N_BLOB_FROM_HEX(key, "0123456789abcdef0123456789abcdef");
        EXPECT_SUCCESS(cipher_suite->record_alg->cipher->set_encryption_key(session_key, &key));
        EXPECT_SUCCESS(cipher_suite->record_alg->cipher->set_decryption_key(session_key, &key));

        S2N_BLOB_FROM_HEX(iv, "0123456789abcdef01234567");

        /* copy iv bytes from input data */
        for (size_t i = 0; i < iv.size; i++) {
            implicit_iv[i] = iv.data[i];
        }

        /* Configure to use s2n maximum fragment / record settings */
        EXPECT_SUCCESS(s2n_connection_prefer_throughput(server_conn));

        /* Testing with a small blob */
        s2n_stack_blob(small_blob, ONE_BLOCK, ONE_BLOCK);
        struct iovec small_io_vec = { 0 };
        small_io_vec.iov_base = small_blob.data;
        small_io_vec.iov_len = small_blob.size;

        int bytes_taken;

        const uint16_t TLS13_RECORD_OVERHEAD = 22;
        EXPECT_SUCCESS(bytes_taken = s2n_record_writev(server_conn, TLS_APPLICATION_DATA, &small_io_vec, 1, 0, small_blob.size));
        EXPECT_EQUAL(bytes_taken, ONE_BLOCK);                                                           /* we wrote the full blob size */
        EXPECT_EQUAL(s2n_stuffer_data_available(&server_conn->out), ONE_BLOCK + TLS13_RECORD_OVERHEAD); /* bytes on the wire */

        /* Check we get a friendly error if we use s2n_record_write again */
        EXPECT_ERROR_WITH_ERRNO(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &small_blob), S2N_ERR_RECORD_STUFFER_NEEDS_DRAINING);
        EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));
        EXPECT_OK(s2n_record_write(server_conn, TLS_APPLICATION_DATA, &small_blob));
        EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

        /* Testing a big 100k blob to be written */
        s2n_stack_blob(big_blob, ONE_HUNDRED_K, ONE_HUNDRED_K);
        struct iovec big_io_vec = { 0 };
        big_io_vec.iov_base = big_blob.data;
        big_io_vec.iov_len = big_blob.size;

        /* Test that s2n_record_writev() doesn't error on writing large payloads.
         * Also asserts the bytes written on the wire.
         */
        EXPECT_SUCCESS(bytes_taken = s2n_record_writev(server_conn, TLS_APPLICATION_DATA, &big_io_vec, 1, 0, big_blob.size));

        /* We verify that s2n_record_writev() is able to send the maximum fragment length as specified by TLS RFCs */
        const uint16_t TLS_MAX_FRAG_LEN = 16384;
        EXPECT_EQUAL(bytes_taken, TLS_MAX_FRAG_LEN);                                                           /* plaintext bytes taken */
        EXPECT_EQUAL(s2n_stuffer_data_available(&server_conn->out), TLS_MAX_FRAG_LEN + TLS13_RECORD_OVERHEAD); /* bytes sent on the wire */

        /* These are invariant regardless of s2n implementation */
        EXPECT_TRUE(bytes_taken <= S2N_TLS_MAXIMUM_FRAGMENT_LENGTH);         /* Plaintext max size - 2^14 = 16384 */
        EXPECT_TRUE(bytes_taken <= (S2N_TLS_MAXIMUM_FRAGMENT_LENGTH + 255)); /* Max record size for TLS 1.3 - 2^14 + 255 = 16639 */
        EXPECT_TRUE(s2n_stuffer_data_available(&server_conn->out) <= S2N_TLS_MAXIMUM_RECORD_LENGTH);
        EXPECT_TRUE(s2n_stuffer_data_available(&server_conn->out) <= S2N_TLS13_MAXIMUM_RECORD_LENGTH);

        EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

        /* Now escape the sandbox and attempt to get record_write to use a larger plaintext bytes */
        /* However, the max fragment length should still be bounded based on the protocol specification */
        const uint16_t MAX_FORCED_OUTGOING_FRAGMENT_LENGTH = 16400;

        server_conn->max_outgoing_fragment_length = MAX_FORCED_OUTGOING_FRAGMENT_LENGTH; /* Trigger fragment length bounding */
        EXPECT_SUCCESS(bytes_taken = s2n_record_writev(server_conn, TLS_APPLICATION_DATA, &big_io_vec, 1, 0, big_blob.size));
        EXPECT_EQUAL(bytes_taken, TLS_MAX_FRAG_LEN);
        EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

        /* Force a generous 100k resize on the outgoing record stuffer */
        EXPECT_SUCCESS(s2n_stuffer_resize(&server_conn->out, ONE_HUNDRED_K));
        server_conn->max_outgoing_fragment_length = MAX_FORCED_OUTGOING_FRAGMENT_LENGTH;
        EXPECT_SUCCESS(bytes_taken = s2n_record_writev(server_conn, TLS_APPLICATION_DATA, &big_io_vec, 1, 0, big_blob.size));
        EXPECT_EQUAL(bytes_taken, TLS_MAX_FRAG_LEN);

        EXPECT_SUCCESS(s2n_stuffer_wipe(&server_conn->out));

        EXPECT_SUCCESS(s2n_connection_free(server_conn));
    };

    /* s2n_record_max_write_size */
    {
        uint16_t result = 0;
        DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
                s2n_connection_ptr_free);
        EXPECT_NOT_NULL(conn);

        EXPECT_ERROR_WITH_ERRNO(s2n_record_max_write_size(NULL, 1, &result), S2N_ERR_NULL);
        EXPECT_ERROR_WITH_ERRNO(s2n_record_max_write_size(conn, 1, NULL), S2N_ERR_NULL);

        conn->actual_protocol_version = 0;
        conn->handshake.handshake_type = INITIAL;
        EXPECT_OK(s2n_record_max_write_size(conn, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH, &result));
        EXPECT_EQUAL(result, S2N_TLS_MAXIMUM_RECORD_LENGTH);

        conn->handshake.handshake_type = NEGOTIATED;
        EXPECT_OK(s2n_record_max_write_size(conn, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH, &result));
        EXPECT_EQUAL(result, S2N_TLS_MAXIMUM_RECORD_LENGTH);

        conn->actual_protocol_version = S2N_TLS12;
        EXPECT_OK(s2n_record_max_write_size(conn, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH, &result));
        EXPECT_EQUAL(result, S2N_TLS12_MAXIMUM_RECORD_LENGTH);

        conn->actual_protocol_version = S2N_TLS13;
        EXPECT_OK(s2n_record_max_write_size(conn, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH, &result));
        EXPECT_EQUAL(result, S2N_TLS13_MAXIMUM_RECORD_LENGTH);

        uint16_t diff = 10;
        conn->actual_protocol_version = S2N_TLS13;
        EXPECT_OK(s2n_record_max_write_size(conn, S2N_TLS_MAXIMUM_FRAGMENT_LENGTH - diff, &result));
        EXPECT_EQUAL(result, S2N_TLS13_MAXIMUM_RECORD_LENGTH - diff);
    };

    END_TEST();
}