s2n_stream_cipher_rc4.c

/*
 * 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 <openssl/rc4.h>

#include "crypto/s2n_cipher.h"
#include "crypto/s2n_fips.h"
#include "crypto/s2n_openssl.h"
#include "utils/s2n_blob.h"
#include "utils/s2n_safety.h"

static const EVP_CIPHER *s2n_evp_rc4()
{
#ifdef S2N_LIBCRYPTO_SUPPORTS_EVP_RC4
    return EVP_rc4();
#else
    return NULL;
#endif
}

static bool s2n_stream_cipher_rc4_available(void)
{
    if (s2n_is_in_fips_mode()) {
        return false;
    }
    /* RC4 MIGHT be available in Openssl-3.0, depending on whether or not the
     * "legacy" provider is loaded. However, for simplicity, assume that RC4
     * is unavailable.
     */
    if (S2N_OPENSSL_VERSION_AT_LEAST(3, 0, 0)) {
        return false;
    }
    return (s2n_evp_rc4() ? true : false);
}

static int s2n_stream_cipher_rc4_encrypt(struct s2n_session_key *key, struct s2n_blob *in, struct s2n_blob *out)
{
    POSIX_ENSURE_GTE(out->size, in->size);

    /* len is set by EVP_EncryptUpdate and checked post operation */
    int len = 0;
    POSIX_GUARD_OSSL(EVP_EncryptUpdate(key->evp_cipher_ctx, out->data, &len, in->data, in->size), S2N_ERR_ENCRYPT);

    POSIX_ENSURE((int64_t) len == (int64_t) in->size, S2N_ERR_DECRYPT);

    return 0;
}

static int s2n_stream_cipher_rc4_decrypt(struct s2n_session_key *key, struct s2n_blob *in, struct s2n_blob *out)
{
    POSIX_ENSURE_GTE(out->size, in->size);

    /* len is set by EVP_DecryptUpdate and checked post operation */
    int len = 0;
    POSIX_GUARD_OSSL(EVP_DecryptUpdate(key->evp_cipher_ctx, out->data, &len, in->data, in->size), S2N_ERR_DECRYPT);

    POSIX_ENSURE((int64_t) len == (int64_t) in->size, S2N_ERR_DECRYPT);

    return 0;
}

static S2N_RESULT s2n_stream_cipher_rc4_set_encryption_key(struct s2n_session_key *key, struct s2n_blob *in)
{
    RESULT_ENSURE_EQ(in->size, 16);
    RESULT_GUARD_OSSL(EVP_EncryptInit_ex(key->evp_cipher_ctx, s2n_evp_rc4(), NULL, in->data, NULL), S2N_ERR_KEY_INIT);

    return S2N_RESULT_OK;
}

static S2N_RESULT s2n_stream_cipher_rc4_set_decryption_key(struct s2n_session_key *key, struct s2n_blob *in)
{
    RESULT_ENSURE_EQ(in->size, 16);
    RESULT_GUARD_OSSL(EVP_DecryptInit_ex(key->evp_cipher_ctx, s2n_evp_rc4(), NULL, in->data, NULL), S2N_ERR_KEY_INIT);

    return S2N_RESULT_OK;
}

static S2N_RESULT s2n_stream_cipher_rc4_init(struct s2n_session_key *key)
{
    RESULT_EVP_CTX_INIT(key->evp_cipher_ctx);

    return S2N_RESULT_OK;
}

static S2N_RESULT s2n_stream_cipher_rc4_destroy_key(struct s2n_session_key *key)
{
    EVP_CIPHER_CTX_cleanup(key->evp_cipher_ctx);

    return S2N_RESULT_OK;
}

const struct s2n_cipher s2n_rc4 = {
    .type = S2N_STREAM,
    .key_material_size = 16,
    .io.stream = {
            .decrypt = s2n_stream_cipher_rc4_decrypt,
            .encrypt = s2n_stream_cipher_rc4_encrypt },
    .is_available = s2n_stream_cipher_rc4_available,
    .init = s2n_stream_cipher_rc4_init,
    .set_decryption_key = s2n_stream_cipher_rc4_set_decryption_key,
    .set_encryption_key = s2n_stream_cipher_rc4_set_encryption_key,
    .destroy_key = s2n_stream_cipher_rc4_destroy_key,
};