scrypt.c

/*-
 * Copyright 2009 Colin Percival
 * 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 <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "pbkdf2.h"
#include "scrypt.h"

// Defines for Little-Endian architecture
#define le32enc(p,v) (*(uint32_t*)(p) = (v))
#define le32dec(p) (*(uint32_t*)(p))

static void blkcpy(void *, void *, size_t);
static void blkxor(void *, void *, size_t);
static void salsa20_8(uint32_t[16]);
static void blockmix_salsa8(uint32_t *, uint32_t *, uint32_t *, size_t);
static uint64_t integerify(void *, size_t);
static void smix(uint8_t *, size_t, uint64_t, uint32_t *, uint32_t *);

static void
blkcpy(void * dest, void * src, size_t len)
{
    size_t * D = dest;
    size_t * S = src;
    size_t L = len / sizeof(size_t);
    size_t i;

    for (i = 0; i < L; i++)
        D[i] = S[i];
}

static void
blkxor(void * dest, void * src, size_t len)
{
    size_t * D = dest;
    size_t * S = src;
    size_t L = len / sizeof(size_t);
    size_t i;

    for (i = 0; i < L; i++)
        D[i] ^= S[i];
}

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

    blkcpy(x, B, 64);
    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(uint32_t * Bin, uint32_t * Bout, uint32_t * X, size_t r)
{
    size_t i;

    /* 1: X <-- B_{2r - 1} */
    blkcpy(X, &Bin[(2 * r - 1) * 16], 64);

    /* 2: for i = 0 to 2r - 1 do */
    for (i = 0; i < 2 * r; i += 2) {
        /* 3: X <-- H(X \xor B_i) */
        blkxor(X, &Bin[i * 16], 64);
        salsa20_8(X);

        /* 4: Y_i <-- X */
        /* 6: B' <-- (Y_0, Y_2 ... Y_{2r-2}, Y_1, Y_3 ... Y_{2r-1}) */
        blkcpy(&Bout[i * 8], X, 64);

        /* 3: X <-- H(X \xor B_i) */
        blkxor(X, &Bin[i * 16 + 16], 64);
        salsa20_8(X);

        /* 4: Y_i <-- X */
        /* 6: B' <-- (Y_0, Y_2 ... Y_{2r-2}, Y_1, Y_3 ... Y_{2r-1}) */
        blkcpy(&Bout[i * 8 + r * 16], X, 64);
    }
}

/**
 * integerify(B, r):
 * Return the result of parsing B_{2r-1} as a little-endian integer.
 */
static uint64_t
integerify(void * B, size_t r)
{
    uint32_t * X = (void *)((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] = le32dec(&B[4 * k]);

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

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

        /* 3: V_i <-- X */
        blkcpy(&V[(i + 1) * (32 * r)], 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(X, &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(Y, &V[j * (32 * r)], 128 * r);
        blockmix_salsa8(Y, X, Z, r);
    }

    /* 10: B' <-- X */
    for (k = 0; k < 32 * r; k++)
        le32enc(&B[4 * k], X[k]);
}

/**
 * crypto_scrypt(passwd, passwdlen, salt, saltlen, buf, buflen, V0):
 * 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.
 * V0 must be able to hold 128*r*N bytes.
 */
void
crypto_scrypt(const uint8_t * passwd, size_t passwdlen,
    const uint8_t * salt, size_t saltlen,
    uint8_t * buf, size_t buflen, void *V0)
{
    const uint32_t N = 64, r = 8, p = 1;
    uint8_t B[128*r*p];
    uint32_t XY[64*r + 16];
    uint32_t * V = (uint32_t *)V0;
    uint32_t i;


    /* 1: (B_0 ... B_{p-1}) <-- PBKDF2(P, S, 1, p * MFLen) */
    pbkdf2_sha256(passwd, passwdlen, salt, saltlen, 1, B, p * 128 * r);

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

    /* 5: DK <-- PBKDF2(P, B, 1, dkLen) */
    pbkdf2_sha256(passwd, passwdlen, B, p * 128 * r, 1, buf, buflen);
}