/* ====================================================================

 * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in

 *    the documentation and/or other materials provided with the

 *    distribution.

 *

 * 3. All advertising materials mentioning features or use of this

 *    software must display the following acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@openssl.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR

 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 * ====================================================================

 *

 */

#include <openssl/crypto.h>

#include "modes_lcl.h"

#include <string.h>

#ifndef MODES_DEBUG

# ifndef NDEBUG

#  define NDEBUG

# endif

#endif

#include <assert.h>

/*

 * NOTE: the IV/counter CTR mode is big-endian.  The code itself is

 * endian-neutral.

 */

/* increment counter (128-bit int) by 1 */

static void ctr128_inc(unsigned char *counter)

{

    u32 n = 16, c = 1;

    do {

        --n;

        c += counter[n];

        counter[n] = (u8)c;

        c >>= 8;

    } while (n);

}

#if !defined(OPENSSL_SMALL_FOOTPRINT)

static void ctr128_inc_aligned(unsigned char *counter)

{

    size_t *data, c, d, n;

    const union {

        long one;

        char little;

    } is_endian = {

        1

    };

    if (is_endian.little || ((size_t)counter % sizeof(size_t)) != 0) {

        ctr128_inc(counter);

        return;

    }

    data = (size_t *)counter;

    c = 1;

    n = 16 / sizeof(size_t);

    do {

        --n;

        d = data[n] += c;

        /* did addition carry? */

        c = ((d - c) & ~d) >> (sizeof(size_t) * 8 - 1);

    } while (n);

}

#endif

/*

 * The input encrypted as though 128bit counter mode is being used.  The

 * extra state information to record how much of the 128bit block we have

 * used is contained in *num, and the encrypted counter is kept in

 * ecount_buf.  Both *num and ecount_buf must be initialised with zeros

 * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes

 * that the counter is in the x lower bits of the IV (ivec), and that the

 * application has full control over overflow and the rest of the IV.  This

 * implementation takes NO responsability for checking that the counter

 * doesn't overflow into the rest of the IV when incremented.

 */

void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,

                           size_t len, const void *key,

                           unsigned char ivec[16],

                           unsigned char ecount_buf[16], unsigned int *num,

                           block128_f block)

{

    unsigned int n;

    size_t l = 0;

    assert(in && out && key && ecount_buf && num);

    assert(*num < 16);

    n = *num;

#if !defined(OPENSSL_SMALL_FOOTPRINT)

    if (16 % sizeof(size_t) == 0) { /* always true actually */

        do {

            while (n && len) {

                *(out++) = *(in++) ^ ecount_buf[n];

                --len;

                n = (n + 1) % 16;

            }

# if defined(STRICT_ALIGNMENT)

            if (((size_t)in | (size_t)out | (size_t)ecount_buf)

                % sizeof(size_t) != 0)

                break;

# endif

            while (len >= 16) {

                (*block) (ivec, ecount_buf, key);

                ctr128_inc_aligned(ivec);

                for (n = 0; n < 16; n += sizeof(size_t))

                    *(size_t *)(out + n) =

                        *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);

                len -= 16;

                out += 16;

                in += 16;

                n = 0;

            }

            if (len) {

                (*block) (ivec, ecount_buf, key);

                ctr128_inc_aligned(ivec);

                while (len--) {

                    out[n] = in[n] ^ ecount_buf[n];

                    ++n;

                }

            }

            *num = n;

            return;

        } while (0);

    }

    /* the rest would be commonly eliminated by x86* compiler */

#endif

    while (l < len) {

        if (n == 0) {

            (*block) (ivec, ecount_buf, key);

            ctr128_inc(ivec);

        }

        out[l] = in[l] ^ ecount_buf[n];

        ++l;

        n = (n + 1) % 16;

    }

    *num = n;

}

/* increment upper 96 bits of 128-bit counter by 1 */

static void ctr96_inc(unsigned char *counter)

{

    u32 n = 12, c = 1;

    do {

        --n;

        c += counter[n];

        counter[n] = (u8)c;

        c >>= 8;

    } while (n);

}

void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,

                                 size_t len, const void *key,

                                 unsigned char ivec[16],

                                 unsigned char ecount_buf[16],

                                 unsigned int *num, ctr128_f func)

{

    unsigned int n, ctr32;

    assert(in && out && key && ecount_buf && num);

    assert(*num < 16);

    n = *num;

    while (n && len) {

        *(out++) = *(in++) ^ ecount_buf[n];

        --len;

        n = (n + 1) % 16;

    }

    ctr32 = GETU32(ivec + 12);

    while (len >= 16) {

        size_t blocks = len / 16;

        /*

         * 1<<28 is just a not-so-small yet not-so-large number...

         * Below condition is practically never met, but it has to

         * be checked for code correctness.

         */

        if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))

            blocks = (1U << 28);

        /*

         * As (*func) operates on 32-bit counter, caller

         * has to handle overflow. 'if' below detects the

         * overflow, which is then handled by limiting the

         * amount of blocks to the exact overflow point...

         */

        ctr32 += (u32)blocks;

        if (ctr32 < blocks) {

            blocks -= ctr32;

            ctr32 = 0;

        }

        (*func) (in, out, blocks, key, ivec);

        /* (*ctr) does not update ivec, caller does: */

        PUTU32(ivec + 12, ctr32);

        /* ... overflow was detected, propogate carry. */

        if (ctr32 == 0)

            ctr96_inc(ivec);

        blocks *= 16;

        len -= blocks;

        out += blocks;

        in += blocks;

    }

    if (len) {

        memset(ecount_buf, 0, 16);

        (*func) (ecount_buf, ecount_buf, 1, key, ivec);

        ++ctr32;

        PUTU32(ivec + 12, ctr32);

        if (ctr32 == 0)

            ctr96_inc(ivec);

        while (len--) {

            out[n] = in[n] ^ ecount_buf[n];

            ++n;

        }

    }

    *num = n;

}