sha256.c

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/*-
 * Copyright 2005,2007,2009 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.
 */

#include <sys/types.h>

#include <stdint.h>
#include <string.h>

#include "sysendian.h"

#include "sha256.h"

/*
 * Encode a length len/4 vector of (uint32_t) into a length len vector of
 * (unsigned char) in big-endian form.  Assumes len is a multiple of 4.
 */
static void
be32enc_vect(unsigned char *dst, const uint32_t *src, size_t len)
{
        size_t i;

        for (i = 0; i < len / 4; i++)
                be32enc(dst + i * 4, src[i]);
}

/*
 * Decode a big-endian length len vector of (unsigned char) into a length
 * len/4 vector of (uint32_t).  Assumes len is a multiple of 4.
 */
static void
be32dec_vect(uint32_t *dst, const unsigned char *src, size_t len)
{
        size_t i;

        for (i = 0; i < len / 4; i++)
                dst[i] = be32dec(src + i * 4);
}

/* Elementary functions used by SHA256 */
#define Ch(x, y, z)     ((x & (y ^ z)) ^ z)
#define Maj(x, y, z)    ((x & (y | z)) | (y & z))
#define SHR(x, n)       (x >> n)
#define ROTR(x, n)      ((x >> n) | (x << (32 - n)))
#define S0(x)           (ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
#define S1(x)           (ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))
#define s0(x)           (ROTR(x, 7) ^ ROTR(x, 18) ^ SHR(x, 3))
#define s1(x)           (ROTR(x, 17) ^ ROTR(x, 19) ^ SHR(x, 10))

/* SHA256 round function */
#define RND(a, b, c, d, e, f, g, h, k)                  \
        t0 = h + S1(e) + Ch(e, f, g) + k;               \
        t1 = S0(a) + Maj(a, b, c);                      \
        d += t0;                                        \
        h  = t0 + t1;

/* Adjusted round function for rotating state */
#define RNDr(S, W, i, k)                        \
        RND(S[(64 - i) % 8], S[(65 - i) % 8],   \
            S[(66 - i) % 8], S[(67 - i) % 8],   \
            S[(68 - i) % 8], S[(69 - i) % 8],   \
            S[(70 - i) % 8], S[(71 - i) % 8],   \
            W[i] + k)

/*
 * SHA256 block compression function.  The 256-bit state is transformed via
 * the 512-bit input block to produce a new state.
 */
static void
SHA256_Transform(uint32_t * state, const unsigned char block[64])
{
        uint32_t W[64];
        uint32_t S[8];
        uint32_t t0, t1;
        int i;

        /* 1. Prepare message schedule W. */
        be32dec_vect(W, block, 64);
        for (i = 16; i < 64; i++)
                W[i] = s1(W[i - 2]) + W[i - 7] + s0(W[i - 15]) + W[i - 16];

        /* 2. Initialize working variables. */
        memcpy(S, state, 32);

        /* 3. Mix. */
        RNDr(S, W, 0, 0x428a2f98);
        RNDr(S, W, 1, 0x71374491);
        RNDr(S, W, 2, 0xb5c0fbcf);
        RNDr(S, W, 3, 0xe9b5dba5);
        RNDr(S, W, 4, 0x3956c25b);
        RNDr(S, W, 5, 0x59f111f1);
        RNDr(S, W, 6, 0x923f82a4);
        RNDr(S, W, 7, 0xab1c5ed5);
        RNDr(S, W, 8, 0xd807aa98);
        RNDr(S, W, 9, 0x12835b01);
        RNDr(S, W, 10, 0x243185be);
        RNDr(S, W, 11, 0x550c7dc3);
        RNDr(S, W, 12, 0x72be5d74);
        RNDr(S, W, 13, 0x80deb1fe);
        RNDr(S, W, 14, 0x9bdc06a7);
        RNDr(S, W, 15, 0xc19bf174);
        RNDr(S, W, 16, 0xe49b69c1);
        RNDr(S, W, 17, 0xefbe4786);
        RNDr(S, W, 18, 0x0fc19dc6);
        RNDr(S, W, 19, 0x240ca1cc);
        RNDr(S, W, 20, 0x2de92c6f);
        RNDr(S, W, 21, 0x4a7484aa);
        RNDr(S, W, 22, 0x5cb0a9dc);
        RNDr(S, W, 23, 0x76f988da);
        RNDr(S, W, 24, 0x983e5152);
        RNDr(S, W, 25, 0xa831c66d);
        RNDr(S, W, 26, 0xb00327c8);
        RNDr(S, W, 27, 0xbf597fc7);
        RNDr(S, W, 28, 0xc6e00bf3);
        RNDr(S, W, 29, 0xd5a79147);
        RNDr(S, W, 30, 0x06ca6351);
        RNDr(S, W, 31, 0x14292967);
        RNDr(S, W, 32, 0x27b70a85);
        RNDr(S, W, 33, 0x2e1b2138);
        RNDr(S, W, 34, 0x4d2c6dfc);
        RNDr(S, W, 35, 0x53380d13);
        RNDr(S, W, 36, 0x650a7354);
        RNDr(S, W, 37, 0x766a0abb);
        RNDr(S, W, 38, 0x81c2c92e);
        RNDr(S, W, 39, 0x92722c85);
        RNDr(S, W, 40, 0xa2bfe8a1);
        RNDr(S, W, 41, 0xa81a664b);
        RNDr(S, W, 42, 0xc24b8b70);
        RNDr(S, W, 43, 0xc76c51a3);
        RNDr(S, W, 44, 0xd192e819);
        RNDr(S, W, 45, 0xd6990624);
        RNDr(S, W, 46, 0xf40e3585);
        RNDr(S, W, 47, 0x106aa070);
        RNDr(S, W, 48, 0x19a4c116);
        RNDr(S, W, 49, 0x1e376c08);
        RNDr(S, W, 50, 0x2748774c);
        RNDr(S, W, 51, 0x34b0bcb5);
        RNDr(S, W, 52, 0x391c0cb3);
        RNDr(S, W, 53, 0x4ed8aa4a);
        RNDr(S, W, 54, 0x5b9cca4f);
        RNDr(S, W, 55, 0x682e6ff3);
        RNDr(S, W, 56, 0x748f82ee);
        RNDr(S, W, 57, 0x78a5636f);
        RNDr(S, W, 58, 0x84c87814);
        RNDr(S, W, 59, 0x8cc70208);
        RNDr(S, W, 60, 0x90befffa);
        RNDr(S, W, 61, 0xa4506ceb);
        RNDr(S, W, 62, 0xbef9a3f7);
        RNDr(S, W, 63, 0xc67178f2);

        /* 4. Mix local working variables into global state */
        for (i = 0; i < 8; i++)
                state[i] += S[i];

        /* Clean the stack. */
        memset(W, 0, 256);
        memset(S, 0, 32);
        t0 = t1 = 0;
}

static unsigned char PAD[64] = {
        0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* Add padding and terminating bit-count. */
static void
SHA256_Pad(SHA256_CTX * ctx)
{
        unsigned char len[8];
        uint32_t r, plen;

        /*
         * Convert length to a vector of bytes -- we do this now rather
         * than later because the length will change after we pad.
         */
        be32enc_vect(len, ctx->count, 8);

        /* Add 1--64 bytes so that the resulting length is 56 mod 64 */
        r = (ctx->count[1] >> 3) & 0x3f;
        plen = (r < 56) ? (56 - r) : (120 - r);
        libscrypt_SHA256_Update(ctx, PAD, (size_t)plen);

        /* Add the terminating bit-count */
        libscrypt_SHA256_Update(ctx, len, 8);
}

/* SHA-256 initialization.  Begins a SHA-256 operation. */
void
libscrypt_SHA256_Init(SHA256_CTX * ctx)
{

        /* Zero bits processed so far */
        ctx->count[0] = ctx->count[1] = 0;

        /* Magic initialization constants */
        ctx->state[0] = 0x6A09E667;
        ctx->state[1] = 0xBB67AE85;
        ctx->state[2] = 0x3C6EF372;
        ctx->state[3] = 0xA54FF53A;
        ctx->state[4] = 0x510E527F;
        ctx->state[5] = 0x9B05688C;
        ctx->state[6] = 0x1F83D9AB;
        ctx->state[7] = 0x5BE0CD19;
}

/* Add bytes into the hash */
void
libscrypt_SHA256_Update(SHA256_CTX * ctx, const void *in, size_t len)
{
        uint32_t bitlen[2];
        uint32_t r;
        const unsigned char *src = in;

        /* Number of bytes left in the buffer from previous updates */
        r = (ctx->count[1] >> 3) & 0x3f;

        /* Convert the length into a number of bits */
        bitlen[1] = ((uint32_t)len) << 3;
        bitlen[0] = (uint32_t)(len >> 29);

        /* Update number of bits */
        if ((ctx->count[1] += bitlen[1]) < bitlen[1])
                ctx->count[0]++;
        ctx->count[0] += bitlen[0];

        /* Handle the case where we don't need to perform any transforms */
        if (len < 64 - r) {
                memcpy(&ctx->buf[r], src, len);
                return;
        }

        /* Finish the current block */
        memcpy(&ctx->buf[r], src, 64 - r);
        SHA256_Transform(ctx->state, ctx->buf);
        src += 64 - r;
        len -= 64 - r;

        /* Perform complete blocks */
        while (len >= 64) {
                SHA256_Transform(ctx->state, src);
                src += 64;
                len -= 64;
        }

        /* Copy left over data into buffer */
        memcpy(ctx->buf, src, len);
}

/*
 * SHA-256 finalization.  Pads the input data, exports the hash value,
 * and clears the context state.
 */
void
libscrypt_SHA256_Final(unsigned char digest[32], SHA256_CTX * ctx)
{

        /* Add padding */
        SHA256_Pad(ctx);

        /* Write the hash */
        be32enc_vect(digest, ctx->state, 32);

        /* Clear the context state */
        memset((void *)ctx, 0, sizeof(*ctx));
}

/* Initialize an HMAC-SHA256 operation with the given key. */
void
libscrypt_HMAC_SHA256_Init(HMAC_SHA256_CTX * ctx, const void * _K, size_t Klen)
{
        unsigned char pad[64];
        unsigned char khash[32];
        const unsigned char * K = _K;
        size_t i;

        /* If Klen > 64, the key is really SHA256(K). */
        if (Klen > 64) {
                libscrypt_SHA256_Init(&ctx->ictx);
                libscrypt_SHA256_Update(&ctx->ictx, K, Klen);
                libscrypt_SHA256_Final(khash, &ctx->ictx);
                K = khash;
                Klen = 32;
        }

        /* Inner SHA256 operation is SHA256(K xor [block of 0x36] || data). */
        libscrypt_SHA256_Init(&ctx->ictx);
        memset(pad, 0x36, 64);
        for (i = 0; i < Klen; i++)
                pad[i] ^= K[i];
        libscrypt_SHA256_Update(&ctx->ictx, pad, 64);

        /* Outer SHA256 operation is SHA256(K xor [block of 0x5c] || hash). */
        libscrypt_SHA256_Init(&ctx->octx);
        memset(pad, 0x5c, 64);
        for (i = 0; i < Klen; i++)
                pad[i] ^= K[i];
        libscrypt_SHA256_Update(&ctx->octx, pad, 64);

        /* Clean the stack. */
        memset(khash, 0, 32);
}

/* Add bytes to the HMAC-SHA256 operation. */
void
libscrypt_HMAC_SHA256_Update(HMAC_SHA256_CTX * ctx, const void *in, size_t len)
{

        /* Feed data to the inner SHA256 operation. */
        libscrypt_SHA256_Update(&ctx->ictx, in, len);
}

/* Finish an HMAC-SHA256 operation. */
void
libscrypt_HMAC_SHA256_Final(unsigned char digest[32], HMAC_SHA256_CTX * ctx)
{
        unsigned char ihash[32];

        /* Finish the inner SHA256 operation. */
        libscrypt_SHA256_Final(ihash, &ctx->ictx);

        /* Feed the inner hash to the outer SHA256 operation. */
        libscrypt_SHA256_Update(&ctx->octx, ihash, 32);

        /* Finish the outer SHA256 operation. */
        libscrypt_SHA256_Final(digest, &ctx->octx);

        /* Clean the stack. */
        memset(ihash, 0, 32);
}

void
libscrypt_PBKDF2_SHA256(const uint8_t * passwd, size_t passwdlen, const uint8_t * salt,
    size_t saltlen, uint64_t c, uint8_t * buf, size_t dkLen)
{
        HMAC_SHA256_CTX PShctx, hctx;
        size_t i;
        uint8_t ivec[4];
        uint8_t U[32];
        uint8_t T[32];
        uint64_t j;
        int k;
        size_t clen;

        /* Compute HMAC state after processing P and S. */
        libscrypt_HMAC_SHA256_Init(&PShctx, passwd, passwdlen);
        libscrypt_HMAC_SHA256_Update(&PShctx, salt, saltlen);

        /* Iterate through the blocks. */
        for (i = 0; i * 32 < dkLen; i++) {
                /* Generate INT(i + 1). */
                be32enc(ivec, (uint32_t)(i + 1));

                /* Compute U_1 = PRF(P, S || INT(i)). */
                memcpy(&hctx, &PShctx, sizeof(HMAC_SHA256_CTX));
                libscrypt_HMAC_SHA256_Update(&hctx, ivec, 4);
                libscrypt_HMAC_SHA256_Final(U, &hctx);

                /* T_i = U_1 ... */
                memcpy(T, U, 32);

                for (j = 2; j <= c; j++) {
                        /* Compute U_j. */
                        libscrypt_HMAC_SHA256_Init(&hctx, passwd, passwdlen);
                        libscrypt_HMAC_SHA256_Update(&hctx, U, 32);
                        libscrypt_HMAC_SHA256_Final(U, &hctx);

                        /* ... xor U_j ... */
                        for (k = 0; k < 32; k++)
                                T[k] ^= U[k];
                }

                /* Copy as many bytes as necessary into buf. */
                clen = dkLen - i * 32;
                if (clen > 32)
                        clen = 32;
                memcpy(&buf[i * 32], T, clen);
        }

        /* Clean PShctx, since we never called _Final on it. */
        memset(&PShctx, 0, sizeof(HMAC_SHA256_CTX));
}