/* fips/rand/fips_drbg_ctr.c */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project.
 */
/* ====================================================================
 * Copyright (c) 2011 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
 *    licensing@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 <stdlib.h>
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/fips.h>
#include <openssl/fips_rand.h>
#include "fips_rand_lcl.h"

static void inc_128(DRBG_CTR_CTX * cctx)
{
    int i;
    unsigned char c;
    unsigned char *p = cctx->V + 15;
    for (i = 0; i < 16; i++) {
        c = *p;
        c++;
        *p = c;
        if (c)
            return;
        p--;
    }
}

static void ctr_XOR(DRBG_CTR_CTX * cctx, const unsigned char *in,
                    size_t inlen)
{
    size_t i, n;
    /* Any zero padding will have no effect on the result as we
     * are XORing. So just process however much input we have.
     */

    if (!in || !inlen)
        return;

    if (inlen < cctx->keylen)
        n = inlen;
    else
        n = cctx->keylen;

    for (i = 0; i < n; i++)
        cctx->K[i] ^= in[i];
    if (inlen <= cctx->keylen)
        return;

    n = inlen - cctx->keylen;
    /* Should never happen */
    if (n > 16)
        n = 16;
    for (i = 0; i < 16; i++)
        cctx->V[i] ^= in[i + cctx->keylen];
}

/* Process a complete block using BCC algorithm of SPP 800-90 10.4.3 */

static void ctr_BCC_block(DRBG_CTR_CTX * cctx, unsigned char *out,
                          const unsigned char *in)
{
    int i;
    for (i = 0; i < 16; i++)
        out[i] ^= in[i];
    AES_encrypt(out, out, &cctx->df_ks);
#if 0
    fprintf(stderr, "BCC in+out\n");
    BIO_dump_fp(stderr, in, 16);
    BIO_dump_fp(stderr, out, 16);
#endif
}

/* Handle several BCC operations for as much data as we need for K and X */
static void ctr_BCC_blocks(DRBG_CTR_CTX * cctx, const unsigned char *in)
{
    ctr_BCC_block(cctx, cctx->KX, in);
    ctr_BCC_block(cctx, cctx->KX + 16, in);
    if (cctx->keylen != 16)
        ctr_BCC_block(cctx, cctx->KX + 32, in);
}

/* Initialise BCC blocks: these have the value 0,1,2 in leftmost positions:
 * see 10.4.2 stage 7.
 */
static void ctr_BCC_init(DRBG_CTR_CTX * cctx)
{
    memset(cctx->KX, 0, 48);
    memset(cctx->bltmp, 0, 16);
    ctr_BCC_block(cctx, cctx->KX, cctx->bltmp);
    cctx->bltmp[3] = 1;
    ctr_BCC_block(cctx, cctx->KX + 16, cctx->bltmp);
    if (cctx->keylen != 16) {
        cctx->bltmp[3] = 2;
        ctr_BCC_block(cctx, cctx->KX + 32, cctx->bltmp);
    }
}

/* Process several blocks into BCC algorithm, some possibly partial */
static void ctr_BCC_update(DRBG_CTR_CTX * cctx,
                           const unsigned char *in, size_t inlen)
{
    if (!in || !inlen)
        return;
    /* If we have partial block handle it first */
    if (cctx->bltmp_pos) {
        size_t left = 16 - cctx->bltmp_pos;
        /* If we now have a complete block process it */
        if (inlen >= left) {
            memcpy(cctx->bltmp + cctx->bltmp_pos, in, left);
            ctr_BCC_blocks(cctx, cctx->bltmp);
            cctx->bltmp_pos = 0;
            inlen -= left;
            in += left;
        }
    }
    /* Process zero or more complete blocks */
    while (inlen >= 16) {
        ctr_BCC_blocks(cctx, in);
        in += 16;
        inlen -= 16;
    }
    /* Copy any remaining partial block to the temporary buffer */
    if (inlen > 0) {
        memcpy(cctx->bltmp + cctx->bltmp_pos, in, inlen);
        cctx->bltmp_pos += inlen;
    }
}

static void ctr_BCC_final(DRBG_CTR_CTX * cctx)
{
    if (cctx->bltmp_pos) {
        memset(cctx->bltmp + cctx->bltmp_pos, 0, 16 - cctx->bltmp_pos);
        ctr_BCC_blocks(cctx, cctx->bltmp);
    }
}

static void ctr_df(DRBG_CTR_CTX * cctx,
                   const unsigned char *in1, size_t in1len,
                   const unsigned char *in2, size_t in2len,
                   const unsigned char *in3, size_t in3len)
{
    size_t inlen;
    unsigned char *p = cctx->bltmp;
    static unsigned char c80 = 0x80;

    ctr_BCC_init(cctx);
    if (!in1)
        in1len = 0;
    if (!in2)
        in2len = 0;
    if (!in3)
        in3len = 0;
    inlen = in1len + in2len + in3len;
    /* Initialise L||N in temporary block */
    *p++ = (inlen >> 24) & 0xff;
    *p++ = (inlen >> 16) & 0xff;
    *p++ = (inlen >> 8) & 0xff;
    *p++ = inlen & 0xff;
    /* NB keylen is at most 32 bytes */
    *p++ = 0;
    *p++ = 0;
    *p++ = 0;
    *p = (unsigned char)((cctx->keylen + 16) & 0xff);
    cctx->bltmp_pos = 8;
    ctr_BCC_update(cctx, in1, in1len);
    ctr_BCC_update(cctx, in2, in2len);
    ctr_BCC_update(cctx, in3, in3len);
    ctr_BCC_update(cctx, &c80, 1);
    ctr_BCC_final(cctx);
    /* Set up key K */
    AES_set_encrypt_key(cctx->KX, cctx->keylen * 8, &cctx->df_kxks);
    /* X follows key K */
    AES_encrypt(cctx->KX + cctx->keylen, cctx->KX, &cctx->df_kxks);
    AES_encrypt(cctx->KX, cctx->KX + 16, &cctx->df_kxks);
    if (cctx->keylen != 16)
        AES_encrypt(cctx->KX + 16, cctx->KX + 32, &cctx->df_kxks);
#if 0
    fprintf(stderr, "Output of ctr_df:\n");
    BIO_dump_fp(stderr, cctx->KX, cctx->keylen + 16);
#endif
}

/* NB the no-df  Update in SP800-90 specifies a constant input length
 * of seedlen, however other uses of this algorithm pad the input with
 * zeroes if necessary and have up to two parameters XORed together,
 * handle both cases in this function instead.
 */

static void ctr_Update(DRBG_CTX *dctx,
                       const unsigned char *in1, size_t in1len,
                       const unsigned char *in2, size_t in2len,
                       const unsigned char *nonce, size_t noncelen)
{
    DRBG_CTR_CTX *cctx = &dctx->d.ctr;
    /* ks is already setup for correct key */
    inc_128(cctx);
    AES_encrypt(cctx->V, cctx->K, &cctx->ks);
    /* If keylen longer than 128 bits need extra encrypt */
    if (cctx->keylen != 16) {
        inc_128(cctx);
        AES_encrypt(cctx->V, cctx->K + 16, &cctx->ks);
    }
    inc_128(cctx);
    AES_encrypt(cctx->V, cctx->V, &cctx->ks);
    /* If 192 bit key part of V is on end of K */
    if (cctx->keylen == 24) {
        memcpy(cctx->V + 8, cctx->V, 8);
        memcpy(cctx->V, cctx->K + 24, 8);
    }

    if (dctx->xflags & DRBG_FLAG_CTR_USE_DF) {
        /* If no input reuse existing derived value */
        if (in1 || nonce || in2)
            ctr_df(cctx, in1, in1len, nonce, noncelen, in2, in2len);
        /* If this a reuse input in1len != 0 */
        if (in1len)
            ctr_XOR(cctx, cctx->KX, dctx->seedlen);
    } else {
        ctr_XOR(cctx, in1, in1len);
        ctr_XOR(cctx, in2, in2len);
    }

    AES_set_encrypt_key(cctx->K, dctx->strength, &cctx->ks);
#if 0
    fprintf(stderr, "K+V after update is:\n");
    BIO_dump_fp(stderr, cctx->K, cctx->keylen);
    BIO_dump_fp(stderr, cctx->V, 16);
#endif
}

static int drbg_ctr_instantiate(DRBG_CTX *dctx,
                                const unsigned char *ent, size_t entlen,
                                const unsigned char *nonce, size_t noncelen,
                                const unsigned char *pers, size_t perslen)
{
    DRBG_CTR_CTX *cctx = &dctx->d.ctr;
    memset(cctx->K, 0, sizeof(cctx->K));
    memset(cctx->V, 0, sizeof(cctx->V));
    AES_set_encrypt_key(cctx->K, dctx->strength, &cctx->ks);
    ctr_Update(dctx, ent, entlen, pers, perslen, nonce, noncelen);
    return 1;
}

static int drbg_ctr_reseed(DRBG_CTX *dctx,
                           const unsigned char *ent, size_t entlen,
                           const unsigned char *adin, size_t adinlen)
{
    ctr_Update(dctx, ent, entlen, adin, adinlen, NULL, 0);
    return 1;
}

static int drbg_ctr_generate(DRBG_CTX *dctx,
                             unsigned char *out, size_t outlen,
                             const unsigned char *adin, size_t adinlen)
{
    DRBG_CTR_CTX *cctx = &dctx->d.ctr;
    if (adin && adinlen) {
        ctr_Update(dctx, adin, adinlen, NULL, 0, NULL, 0);
        /* This means we reuse derived value */
        if (dctx->xflags & DRBG_FLAG_CTR_USE_DF) {
            adin = NULL;
            adinlen = 1;
        }
    } else
        adinlen = 0;

    for (;;) {
        inc_128(cctx);
        if (outlen < 16) {
            /* Use K as temp space as it will be updated */
            AES_encrypt(cctx->V, cctx->K, &cctx->ks);
            memcpy(out, cctx->K, outlen);
            break;
        }
        AES_encrypt(cctx->V, out, &cctx->ks);
        out += 16;
        outlen -= 16;
        if (outlen == 0)
            break;
    }

    ctr_Update(dctx, adin, adinlen, NULL, 0, NULL, 0);

    return 1;

}

static int drbg_ctr_uninstantiate(DRBG_CTX *dctx)
{
    memset(&dctx->d.ctr, 0, sizeof(DRBG_CTR_CTX));
    return 1;
}

int fips_drbg_ctr_init(DRBG_CTX *dctx)
{
    DRBG_CTR_CTX *cctx = &dctx->d.ctr;

    size_t keylen;

    switch (dctx->type) {
    case NID_aes_128_ctr:
        keylen = 16;
        break;

    case NID_aes_192_ctr:
        keylen = 24;
        break;

    case NID_aes_256_ctr:
        keylen = 32;
        break;

    default:
        return -2;
    }

    dctx->instantiate = drbg_ctr_instantiate;
    dctx->reseed = drbg_ctr_reseed;
    dctx->generate = drbg_ctr_generate;
    dctx->uninstantiate = drbg_ctr_uninstantiate;

    cctx->keylen = keylen;
    dctx->strength = keylen * 8;
    dctx->blocklength = 16;
    dctx->seedlen = keylen + 16;

    if (dctx->xflags & DRBG_FLAG_CTR_USE_DF) {
        /* df initialisation */
        static unsigned char df_key[32] = {
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
            0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
            0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
            0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
        };
        /* Set key schedule for df_key */
        AES_set_encrypt_key(df_key, dctx->strength, &cctx->df_ks);

        dctx->min_entropy = cctx->keylen;
        dctx->max_entropy = DRBG_MAX_LENGTH;
        dctx->min_nonce = dctx->min_entropy / 2;
        dctx->max_nonce = DRBG_MAX_LENGTH;
        dctx->max_pers = DRBG_MAX_LENGTH;
        dctx->max_adin = DRBG_MAX_LENGTH;
    } else {
        dctx->min_entropy = dctx->seedlen;
        dctx->max_entropy = dctx->seedlen;
        /* Nonce not used */
        dctx->min_nonce = 0;
        dctx->max_nonce = 0;
        dctx->max_pers = dctx->seedlen;
        dctx->max_adin = dctx->seedlen;
    }

    dctx->max_request = 1 << 16;
    dctx->reseed_interval = 1 << 24;

    return 1;
}