/*-
 * Copyright 2009 Colin Percival
 * Copyright 2013 Alexander Peslyak
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS 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 AUTHOR OR 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.
 *
 * This file was originally written by Colin Percival as part of the Tarsnap
 * online backup system.
 */

#include <errno.h>
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "../pbkdf2-sha256.h"
#include "../crypto_scrypt.h"
#include "../../../sodium/common.h"

static inline void
blkcpy_64(escrypt_block_t *dest, const escrypt_block_t *src)
{
    int i;

#if (ARCH_BITS==32)
    for (i = 0; i < 16; ++i)
        dest->w[i] = src->w[i];
#else
    for (i = 0; i < 8; ++i)
        dest->d[i] = src->d[i];
#endif
}

static inline void
blkxor_64(escrypt_block_t *dest, const escrypt_block_t *src)
{
    int i;

#if (ARCH_BITS==32)
    for (i = 0; i < 16; ++i)
        dest->w[i] ^= src->w[i];
#else
    for (i = 0; i < 8; ++i)
        dest->d[i] ^= src->d[i];
#endif
}

static inline void
blkcpy(escrypt_block_t *dest, const escrypt_block_t *src, size_t len)
{
    size_t i, L;
#if (ARCH_BITS==32)
    L = (len>>2);
    for (i = 0; i < L; ++i)
        dest->w[i] = src->w[i];
#else
    L = (len>>3);
    for (i = 0; i < L; ++i)
        dest->d[i] = src->d[i];
#endif
}

static inline void
blkxor(escrypt_block_t *dest, const escrypt_block_t *src, size_t len)
{
    size_t i, L;
#if (ARCH_BITS==32)
    L = (len>>2);
    for (i = 0; i < L; ++i)
        dest->w[i] ^= src->w[i];
#else
    L = (len>>3);
    for (i = 0; i < L; ++i)
        dest->d[i] ^= src->d[i];
#endif
}

/**
 * salsa20_8(B):
 * Apply the salsa20/8 core to the provided block.
 */
static void
salsa20_8(uint32_t B[16])
{
    escrypt_block_t X;
    uint32_t *x = X.w;
    size_t i;

    blkcpy_64(&X, (escrypt_block_t*)B);
    for (i = 0; i < 8; i += 2) {
#define R(a,b) (((a) << (b)) | ((a) >> (32 - (b))))
        /* Operate on columns. */
        x[ 4] ^= R(x[ 0]+x[12], 7);  x[ 8] ^= R(x[ 4]+x[ 0], 9);
        x[12] ^= R(x[ 8]+x[ 4],13);  x[ 0] ^= R(x[12]+x[ 8],18);

        x[ 9] ^= R(x[ 5]+x[ 1], 7);  x[13] ^= R(x[ 9]+x[ 5], 9);
        x[ 1] ^= R(x[13]+x[ 9],13);  x[ 5] ^= R(x[ 1]+x[13],18);

        x[14] ^= R(x[10]+x[ 6], 7);  x[ 2] ^= R(x[14]+x[10], 9);
        x[ 6] ^= R(x[ 2]+x[14],13);  x[10] ^= R(x[ 6]+x[ 2],18);

        x[ 3] ^= R(x[15]+x[11], 7);  x[ 7] ^= R(x[ 3]+x[15], 9);
        x[11] ^= R(x[ 7]+x[ 3],13);  x[15] ^= R(x[11]+x[ 7],18);

        /* Operate on rows. */
        x[ 1] ^= R(x[ 0]+x[ 3], 7);  x[ 2] ^= R(x[ 1]+x[ 0], 9);
        x[ 3] ^= R(x[ 2]+x[ 1],13);  x[ 0] ^= R(x[ 3]+x[ 2],18);

        x[ 6] ^= R(x[ 5]+x[ 4], 7);  x[ 7] ^= R(x[ 6]+x[ 5], 9);
        x[ 4] ^= R(x[ 7]+x[ 6],13);  x[ 5] ^= R(x[ 4]+x[ 7],18);

        x[11] ^= R(x[10]+x[ 9], 7);  x[ 8] ^= R(x[11]+x[10], 9);
        x[ 9] ^= R(x[ 8]+x[11],13);  x[10] ^= R(x[ 9]+x[ 8],18);

        x[12] ^= R(x[15]+x[14], 7);  x[13] ^= R(x[12]+x[15], 9);
        x[14] ^= R(x[13]+x[12],13);  x[15] ^= R(x[14]+x[13],18);
#undef R
    }
    for (i = 0; i < 16; i++)
        B[i] += x[i];
}

/**
 * blockmix_salsa8(Bin, Bout, X, r):
 * Compute Bout = BlockMix_{salsa20/8, r}(Bin).  The input Bin must be 128r
 * bytes in length; the output Bout must also be the same size.  The
 * temporary space X must be 64 bytes.
 */
static void
blockmix_salsa8(const uint32_t * Bin, uint32_t * Bout, uint32_t * X, size_t r)
{
    size_t i;

    /* 1: X <-- B_{2r - 1} */
    blkcpy_64((escrypt_block_t*)X, (escrypt_block_t*)&Bin[(2 * r - 1) * 16]);

    /* 2: for i = 0 to 2r - 1 do */
    for (i = 0; i < 2 * r; i += 2) {
        /* 3: X <-- H(X \xor B_i) */
        blkxor_64((escrypt_block_t*)X, (escrypt_block_t*)&Bin[i * 16]);
        salsa20_8(X);

        /* 4: Y_i <-- X */
        /* 6: B' <-- (Y_0, Y_2 ... Y_{2r-2}, Y_1, Y_3 ... Y_{2r-1}) */
        blkcpy_64((escrypt_block_t*)&Bout[i * 8], (escrypt_block_t*)X);

        /* 3: X <-- H(X \xor B_i) */
        blkxor_64((escrypt_block_t*)X, (escrypt_block_t*)&Bin[i * 16 + 16]);
        salsa20_8(X);

        /* 4: Y_i <-- X */
        /* 6: B' <-- (Y_0, Y_2 ... Y_{2r-2}, Y_1, Y_3 ... Y_{2r-1}) */
        blkcpy_64((escrypt_block_t*)&Bout[i * 8 + r * 16], (escrypt_block_t*)X);
    }
}

/**
 * integerify(B, r):
 * Return the result of parsing B_{2r-1} as a little-endian integer.
 */
static inline uint64_t
integerify(const void * B, size_t r)
{
    const uint32_t * X = (const uint32_t *)((uintptr_t)(B) + (2 * r - 1) * 64);

    return (((uint64_t)(X[1]) << 32) + X[0]);
}

/**
 * smix(B, r, N, V, XY):
 * Compute B = SMix_r(B, N).  The input B must be 128r bytes in length;
 * the temporary storage V must be 128rN bytes in length; the temporary
 * storage XY must be 256r + 64 bytes in length.  The value N must be a
 * power of 2 greater than 1.  The arrays B, V, and XY must be aligned to a
 * multiple of 64 bytes.
 */
static void
smix(uint8_t * B, size_t r, uint64_t N, uint32_t * V, uint32_t * XY)
{
    uint32_t * X = XY;
    uint32_t * Y = &XY[32 * r];
    uint32_t * Z = &XY[64 * r];
    uint64_t i;
    uint64_t j;
    size_t k;

    /* 1: X <-- B */
    for (k = 0; k < 32 * r; k++)
        X[k] = LOAD32_LE(&B[4 * k]);

    /* 2: for i = 0 to N - 1 do */
    for (i = 0; i < N; i += 2) {
        /* 3: V_i <-- X */
        blkcpy((escrypt_block_t*)&V[i * (32 * r)], (escrypt_block_t*)X, 128 * r);

        /* 4: X <-- H(X) */
        blockmix_salsa8(X, Y, Z, r);

        /* 3: V_i <-- X */
        blkcpy((escrypt_block_t*)&V[(i + 1) * (32 * r)], (escrypt_block_t*)Y, 128 * r);

        /* 4: X <-- H(X) */
        blockmix_salsa8(Y, X, Z, r);
    }

    /* 6: for i = 0 to N - 1 do */
    for (i = 0; i < N; i += 2) {
        /* 7: j <-- Integerify(X) mod N */
        j = integerify(X, r) & (N - 1);

        /* 8: X <-- H(X \xor V_j) */
        blkxor((escrypt_block_t*)X, (escrypt_block_t*)&V[j * (32 * r)], 128 * r);
        blockmix_salsa8(X, Y, Z, r);

        /* 7: j <-- Integerify(X) mod N */
        j = integerify(Y, r) & (N - 1);

        /* 8: X <-- H(X \xor V_j) */
        blkxor((escrypt_block_t*)Y, (escrypt_block_t*)&V[j * (32 * r)], 128 * r);
        blockmix_salsa8(Y, X, Z, r);
    }
    /* 10: B' <-- X */
    for (k = 0; k < 32 * r; k++)
        STORE32_LE(&B[4 * k], X[k]);
}

/**
 * escrypt_kdf(local, passwd, passwdlen, salt, saltlen,
 *     N, r, p, buf, buflen):
 * Compute scrypt(passwd[0 .. passwdlen - 1], salt[0 .. saltlen - 1], N, r,
 * p, buflen) and write the result into buf.  The parameters r, p, and buflen
 * must satisfy r * p < 2^30 and buflen <= (2^32 - 1) * 32.  The parameter N
 * must be a power of 2 greater than 1.
 *
 * Return 0 on success; or -1 on error.
 */
int
escrypt_kdf_nosse(escrypt_local_t * local,
    const uint8_t * passwd, size_t passwdlen,
    const uint8_t * salt, size_t saltlen,
    uint64_t N, uint32_t _r, uint32_t _p,
    uint8_t * buf, size_t buflen)
{
    size_t B_size, V_size, XY_size, need;
    uint8_t * B;
    uint32_t * V, * XY;
    size_t r = _r, p = _p;
    uint32_t i;

    /* Sanity-check parameters. */
#if SIZE_MAX > UINT32_MAX
    if (buflen > (((uint64_t)(1) << 32) - 1) * 32) {
        errno = EFBIG;
        return -1;
    }
#endif
    if ((uint64_t)(r) * (uint64_t)(p) >= ((uint64_t) 1 << 30)) {
        errno = EFBIG;
        return -1;
    }
    if (N > UINT32_MAX) {
        errno = EFBIG;
        return -1;
    }
    if (((N & (N - 1)) != 0) || (N < 2)) {
        errno = EINVAL;
        return -1;
    }
    if (r == 0 || p == 0) {
        errno = EINVAL;
        return -1;
    }
    if ((r > SIZE_MAX / 128 / p) ||
#if SIZE_MAX / 256 <= UINT32_MAX
        (r > SIZE_MAX / 256) ||
#endif
        (N > SIZE_MAX / 128 / r)) {
        errno = ENOMEM;
        return -1;
    }

    /* Allocate memory. */
    B_size = (size_t)128 * r * p;
    V_size = (size_t)128 * r * N;
    need = B_size + V_size;
    if (need < V_size) {
        errno = ENOMEM;
        return -1;
    }
    XY_size = (size_t)256 * r + 64;
    need += XY_size;
    if (need < XY_size) {
        errno = ENOMEM;
        return -1;
    }
    if (local->size < need) {
        if (free_region(local))
            return -1;
        if (!alloc_region(local, need))
            return -1;
    }
    B = (uint8_t *)local->aligned;
    V = (uint32_t *)((uint8_t *)B + B_size);
    XY = (uint32_t *)((uint8_t *)V + V_size);

    /* 1: (B_0 ... B_{p-1}) <-- PBKDF2(P, S, 1, p * MFLen) */
    PBKDF2_SHA256(passwd, passwdlen, salt, saltlen, 1, B, B_size);

    /* 2: for i = 0 to p - 1 do */
    for (i = 0; i < p; i++) {
        /* 3: B_i <-- MF(B_i, N) */
        smix(&B[(size_t)128 * i * r], r, N, V, XY);
    }

    /* 5: DK <-- PBKDF2(P, B, 1, dkLen) */
    PBKDF2_SHA256(passwd, passwdlen, B, B_size, 1, buf, buflen);

    /* Success! */
    return 0;
}