cbc128.c

/*
 * Copyright 2008-2021 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the OpenSSL license (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#include <openssl/crypto.h>
#include "modes_local.h"
#include <string.h>

#if !defined(STRICT_ALIGNMENT) && !defined(PEDANTIC)
# define STRICT_ALIGNMENT 0
#endif

#if defined(__GNUC__) && !STRICT_ALIGNMENT
typedef size_t size_t_aX __attribute((__aligned__(1)));
#else
typedef size_t size_t_aX;
#endif

void CRYPTO_cbc128_encrypt(const unsigned char *in, unsigned char *out,
                           size_t len, const void *key,
                           unsigned char ivec[16], block128_f block)
{
    size_t n;
    const unsigned char *iv = ivec;

    if (len == 0)
        return;

#if !defined(OPENSSL_SMALL_FOOTPRINT)
    if (STRICT_ALIGNMENT &&
        ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
        while (len >= 16) {
            for (n = 0; n < 16; ++n)
                out[n] = in[n] ^ iv[n];
            (*block) (out, out, key);
            iv = out;
            len -= 16;
            in += 16;
            out += 16;
        }
    } else {
        while (len >= 16) {
            for (n = 0; n < 16; n += sizeof(size_t))
                *(size_t_aX *)(out + n) =
                    *(size_t_aX *)(in + n) ^ *(size_t_aX *)(iv + n);
            (*block) (out, out, key);
            iv = out;
            len -= 16;
            in += 16;
            out += 16;
        }
    }
#endif
    while (len) {
        for (n = 0; n < 16 && n < len; ++n)
            out[n] = in[n] ^ iv[n];
        for (; n < 16; ++n)
            out[n] = iv[n];
        (*block) (out, out, key);
        iv = out;
        if (len <= 16)
            break;
        len -= 16;
        in += 16;
        out += 16;
    }
    if (ivec != iv)
        memcpy(ivec, iv, 16);
}

void CRYPTO_cbc128_decrypt(const unsigned char *in, unsigned char *out,
                           size_t len, const void *key,
                           unsigned char ivec[16], block128_f block)
{
    size_t n;
    union {
        size_t t[16 / sizeof(size_t)];
        unsigned char c[16];
    } tmp;

    if (len == 0)
        return;

#if !defined(OPENSSL_SMALL_FOOTPRINT)
    if (in != out) {
        const unsigned char *iv = ivec;

        if (STRICT_ALIGNMENT &&
            ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
            while (len >= 16) {
                (*block) (in, out, key);
                for (n = 0; n < 16; ++n)
                    out[n] ^= iv[n];
                iv = in;
                len -= 16;
                in += 16;
                out += 16;
            }
        } else if (16 % sizeof(size_t) == 0) { /* always true */
            while (len >= 16) {
                size_t_aX *out_t = (size_t_aX *)out;
                size_t_aX *iv_t = (size_t_aX *)iv;

                (*block) (in, out, key);
                for (n = 0; n < 16 / sizeof(size_t); n++)
                    out_t[n] ^= iv_t[n];
                iv = in;
                len -= 16;
                in += 16;
                out += 16;
            }
        }
        if (ivec != iv)
            memcpy(ivec, iv, 16);
    } else {
        if (STRICT_ALIGNMENT &&
            ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
            unsigned char c;
            while (len >= 16) {
                (*block) (in, tmp.c, key);
                for (n = 0; n < 16; ++n) {
                    c = in[n];
                    out[n] = tmp.c[n] ^ ivec[n];
                    ivec[n] = c;
                }
                len -= 16;
                in += 16;
                out += 16;
            }
        } else if (16 % sizeof(size_t) == 0) { /* always true */
            while (len >= 16) {
                size_t c;
                size_t_aX *out_t = (size_t_aX *)out;
                size_t_aX *ivec_t = (size_t_aX *)ivec;
                const size_t_aX *in_t = (const size_t_aX *)in;

                (*block) (in, tmp.c, key);
                for (n = 0; n < 16 / sizeof(size_t); n++) {
                    c = in_t[n];
                    out_t[n] = tmp.t[n] ^ ivec_t[n];
                    ivec_t[n] = c;
                }
                len -= 16;
                in += 16;
                out += 16;
            }
        }
    }
#endif
    while (len) {
        unsigned char c;
        (*block) (in, tmp.c, key);
        for (n = 0; n < 16 && n < len; ++n) {
            c = in[n];
            out[n] = tmp.c[n] ^ ivec[n];
            ivec[n] = c;
        }
        if (len <= 16) {
            for (; n < 16; ++n)
                ivec[n] = in[n];
            break;
        }
        len -= 16;
        in += 16;
        out += 16;
    }
}