library/sha256.c

/*
 *  FIPS-180-2 compliant SHA-256 implementation
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
/*
 *  The SHA-256 Secure Hash Standard was published by NIST in 2002.
 *
 *  http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf
 */

#include "common.h"

#if defined(MBEDTLS_SHA256_C)

#include "mbedtls/sha256.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"

#include <string.h>

#if defined(MBEDTLS_SELF_TEST)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#include <stdlib.h>
#define mbedtls_printf printf
#define mbedtls_calloc    calloc
#define mbedtls_free       free
#endif /* MBEDTLS_PLATFORM_C */
#endif /* MBEDTLS_SELF_TEST */

#if defined(__aarch64__)
#  if defined(MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT) || \
      defined(MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY)
#    include <arm_neon.h>
#  endif
#  if defined(MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT) && defined(__linux__)
#    include <sys/auxv.h>
#  endif
#else
#  undef MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY
#  undef MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT
#endif

#if defined(MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT)
/*
 * Capability detection code comes early, so we can disable
 * MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT if no detection mechanism found
 */
#if defined(HWCAP_SHA2)
static int mbedtls_a64_crypto_sha256_check_support( void )
{
    return( ( getauxval( AT_HWCAP ) & HWCAP_SHA2 ) ? 1 : 0 );
}
#elif defined(__APPLE__)
static int mbedtls_a64_crypto_sha256_check_support( void )
{
    return( 1 );
}
#elif defined(__unix__) && defined(SIG_SETMASK)
/* Detection with SIGILL, setjmp() and longjmp() */
#include <signal.h>
#include <setjmp.h>

#ifndef asm
#define asm __asm__
#endif

static jmp_buf return_from_sigill;

/*
 * A64 SHA256 support detection via SIGILL
 */
static void sigill_handler( int signal )
{
    (void) signal;
    longjmp( return_from_sigill, 1 );
}

static int mbedtls_a64_crypto_sha256_check_support( void )
{
    struct sigaction old_action, new_action;

    sigset_t old_mask;
    if( sigprocmask( 0, NULL, &old_mask ) )
        return( 0 );

    sigemptyset( &new_action.sa_mask );
    new_action.sa_flags = 0;
    new_action.sa_handler = sigill_handler;

    sigaction( SIGILL, &new_action, &old_action );

    static int ret = 0;

    if( setjmp( return_from_sigill ) == 0 )        /* First return only */
    {
        /* If this traps, we will return a second time from setjmp() with 1 */
        asm( "sha256h q0, q0, v0.4s" : : : "v0" );
        ret = 1;
    }

    sigaction( SIGILL, &old_action, NULL );
    sigprocmask( SIG_SETMASK, &old_mask, NULL );

    return( ret );
}
#else
#warning "No mechanism to detect A64_CRYPTO found, using C code only"
#undef MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT
#endif  /* HWCAP_SHA2, __APPLE__, __unix__ && SIG_SETMASK */

#endif  /* MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT */

#define SHA256_VALIDATE_RET(cond)                           \
    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_SHA256_BAD_INPUT_DATA )
#define SHA256_VALIDATE(cond)  MBEDTLS_INTERNAL_VALIDATE( cond )

#if !defined(MBEDTLS_SHA256_ALT)

#define SHA256_BLOCK_SIZE 64

void mbedtls_sha256_init( mbedtls_sha256_context *ctx )
{
    SHA256_VALIDATE( ctx != NULL );

    memset( ctx, 0, sizeof( mbedtls_sha256_context ) );
}

void mbedtls_sha256_free( mbedtls_sha256_context *ctx )
{
    if( ctx == NULL )
        return;

    mbedtls_platform_zeroize( ctx, sizeof( mbedtls_sha256_context ) );
}

void mbedtls_sha256_clone( mbedtls_sha256_context *dst,
                           const mbedtls_sha256_context *src )
{
    SHA256_VALIDATE( dst != NULL );
    SHA256_VALIDATE( src != NULL );

    *dst = *src;
}

/*
 * SHA-256 context setup
 */
int mbedtls_sha256_starts( mbedtls_sha256_context *ctx, int is224 )
{
    SHA256_VALIDATE_RET( ctx != NULL );

#if defined(MBEDTLS_SHA224_C)
    SHA256_VALIDATE_RET( is224 == 0 || is224 == 1 );
#else
    SHA256_VALIDATE_RET( is224 == 0 );
#endif

    ctx->total[0] = 0;
    ctx->total[1] = 0;

    if( is224 == 0 )
    {
        /* SHA-256 */
        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;
    }
    else
    {
#if defined(MBEDTLS_SHA224_C)
        /* SHA-224 */
        ctx->state[0] = 0xC1059ED8;
        ctx->state[1] = 0x367CD507;
        ctx->state[2] = 0x3070DD17;
        ctx->state[3] = 0xF70E5939;
        ctx->state[4] = 0xFFC00B31;
        ctx->state[5] = 0x68581511;
        ctx->state[6] = 0x64F98FA7;
        ctx->state[7] = 0xBEFA4FA4;
#endif
    }

    ctx->is224 = is224;

    return( 0 );
}

#if !defined(MBEDTLS_SHA256_PROCESS_ALT)
static const uint32_t K[] =
{
    0x428A2F98, 0x71374491, 0xB5C0FBCF, 0xE9B5DBA5,
    0x3956C25B, 0x59F111F1, 0x923F82A4, 0xAB1C5ED5,
    0xD807AA98, 0x12835B01, 0x243185BE, 0x550C7DC3,
    0x72BE5D74, 0x80DEB1FE, 0x9BDC06A7, 0xC19BF174,
    0xE49B69C1, 0xEFBE4786, 0x0FC19DC6, 0x240CA1CC,
    0x2DE92C6F, 0x4A7484AA, 0x5CB0A9DC, 0x76F988DA,
    0x983E5152, 0xA831C66D, 0xB00327C8, 0xBF597FC7,
    0xC6E00BF3, 0xD5A79147, 0x06CA6351, 0x14292967,
    0x27B70A85, 0x2E1B2138, 0x4D2C6DFC, 0x53380D13,
    0x650A7354, 0x766A0ABB, 0x81C2C92E, 0x92722C85,
    0xA2BFE8A1, 0xA81A664B, 0xC24B8B70, 0xC76C51A3,
    0xD192E819, 0xD6990624, 0xF40E3585, 0x106AA070,
    0x19A4C116, 0x1E376C08, 0x2748774C, 0x34B0BCB5,
    0x391C0CB3, 0x4ED8AA4A, 0x5B9CCA4F, 0x682E6FF3,
    0x748F82EE, 0x78A5636F, 0x84C87814, 0x8CC70208,
    0x90BEFFFA, 0xA4506CEB, 0xBEF9A3F7, 0xC67178F2,
};

#endif

#if defined(MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT) || \
    defined(MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY)

#if defined(MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY)
#  define mbedtls_internal_sha256_process_many_a64_crypto mbedtls_internal_sha256_process_many
#  define mbedtls_internal_sha256_process_a64_crypto      mbedtls_internal_sha256_process
#endif

static size_t mbedtls_internal_sha256_process_many_a64_crypto(
                  mbedtls_sha256_context *ctx, const uint8_t *msg, size_t len )
{
    uint32x4_t abcd = vld1q_u32( &ctx->state[0] );
    uint32x4_t efgh = vld1q_u32( &ctx->state[4] );

    size_t processed = 0;

    for( ;
         len >= SHA256_BLOCK_SIZE;
         processed += SHA256_BLOCK_SIZE,
               msg += SHA256_BLOCK_SIZE,
               len -= SHA256_BLOCK_SIZE )
    {
        uint32x4_t tmp, abcd_prev;

        uint32x4_t abcd_orig = abcd;
        uint32x4_t efgh_orig = efgh;

        uint32x4_t sched0 = vld1q_u32( (const uint32_t *)( msg + 16 * 0 ) );
        uint32x4_t sched1 = vld1q_u32( (const uint32_t *)( msg + 16 * 1 ) );
        uint32x4_t sched2 = vld1q_u32( (const uint32_t *)( msg + 16 * 2 ) );
        uint32x4_t sched3 = vld1q_u32( (const uint32_t *)( msg + 16 * 3 ) );

#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__  /* Will be true if not defined */
                                               /* Untested on BE */
        sched0 = vreinterpretq_u32_u8( vrev32q_u8( vreinterpretq_u8_u32( sched0 ) ) );
        sched1 = vreinterpretq_u32_u8( vrev32q_u8( vreinterpretq_u8_u32( sched1 ) ) );
        sched2 = vreinterpretq_u32_u8( vrev32q_u8( vreinterpretq_u8_u32( sched2 ) ) );
        sched3 = vreinterpretq_u32_u8( vrev32q_u8( vreinterpretq_u8_u32( sched3 ) ) );
#endif

        /* Rounds 0 to 3 */
        tmp = vaddq_u32( sched0, vld1q_u32( &K[0] ) );
        abcd_prev = abcd;
        abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
        efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

        /* Rounds 4 to 7 */
        tmp = vaddq_u32( sched1, vld1q_u32( &K[4] ) );
        abcd_prev = abcd;
        abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
        efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

        /* Rounds 8 to 11 */
        tmp = vaddq_u32( sched2, vld1q_u32( &K[8] ) );
        abcd_prev = abcd;
        abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
        efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

        /* Rounds 12 to 15 */
        tmp = vaddq_u32( sched3, vld1q_u32( &K[12] ) );
        abcd_prev = abcd;
        abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
        efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

        for( int t = 16; t < 64; t += 16 )
        {
            /* Rounds t to t + 3 */
            sched0 = vsha256su1q_u32( vsha256su0q_u32( sched0, sched1 ), sched2, sched3 );
            tmp = vaddq_u32( sched0, vld1q_u32( &K[t] ) );
            abcd_prev = abcd;
            abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
            efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

            /* Rounds t + 4 to t + 7 */
            sched1 = vsha256su1q_u32( vsha256su0q_u32( sched1, sched2 ), sched3, sched0 );
            tmp = vaddq_u32( sched1, vld1q_u32( &K[t + 4] ) );
            abcd_prev = abcd;
            abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
            efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

            /* Rounds t + 8 to t + 11 */
            sched2 = vsha256su1q_u32( vsha256su0q_u32( sched2, sched3 ), sched0, sched1 );
            tmp = vaddq_u32( sched2, vld1q_u32( &K[t + 8] ) );
            abcd_prev = abcd;
            abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
            efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );

            /* Rounds t + 12 to t + 15 */
            sched3 = vsha256su1q_u32( vsha256su0q_u32( sched3, sched0 ), sched1, sched2 );
            tmp = vaddq_u32( sched3, vld1q_u32( &K[t + 12] ) );
            abcd_prev = abcd;
            abcd = vsha256hq_u32( abcd_prev, efgh, tmp );
            efgh = vsha256h2q_u32( efgh, abcd_prev, tmp );
        }

        abcd = vaddq_u32( abcd, abcd_orig );
        efgh = vaddq_u32( efgh, efgh_orig );
    }

    vst1q_u32( &ctx->state[0], abcd );
    vst1q_u32( &ctx->state[4], efgh );

    return( processed );
}

int mbedtls_internal_sha256_process_a64_crypto( mbedtls_sha256_context *ctx,
        const unsigned char data[SHA256_BLOCK_SIZE] )
{
    return( ( mbedtls_internal_sha256_process_many_a64_crypto( ctx, data,
                SHA256_BLOCK_SIZE ) == SHA256_BLOCK_SIZE ) ? 0 : -1 );
}

#endif /* MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT || MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY */


#if !defined(MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT)
#define mbedtls_internal_sha256_process_many_c mbedtls_internal_sha256_process_many
#define mbedtls_internal_sha256_process_c      mbedtls_internal_sha256_process
#endif


#if !defined(MBEDTLS_SHA256_PROCESS_ALT) && \
    !defined(MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY)

#define  SHR(x,n) (((x) & 0xFFFFFFFF) >> (n))
#define ROTR(x,n) (SHR(x,n) | ((x) << (32 - (n))))

#define S0(x) (ROTR(x, 7) ^ ROTR(x,18) ^  SHR(x, 3))
#define S1(x) (ROTR(x,17) ^ ROTR(x,19) ^  SHR(x,10))

#define S2(x) (ROTR(x, 2) ^ ROTR(x,13) ^ ROTR(x,22))
#define S3(x) (ROTR(x, 6) ^ ROTR(x,11) ^ ROTR(x,25))

#define F0(x,y,z) (((x) & (y)) | ((z) & ((x) | (y))))
#define F1(x,y,z) ((z) ^ ((x) & ((y) ^ (z))))

#define R(t)                                                        \
    (                                                               \
        local.W[t] = S1(local.W[(t) -  2]) + local.W[(t) -  7] +    \
                     S0(local.W[(t) - 15]) + local.W[(t) - 16]      \
    )

#define P(a,b,c,d,e,f,g,h,x,K)                                      \
    do                                                              \
    {                                                               \
        local.temp1 = (h) + S3(e) + F1((e),(f),(g)) + (K) + (x);    \
        local.temp2 = S2(a) + F0((a),(b),(c));                      \
        (d) += local.temp1; (h) = local.temp1 + local.temp2;        \
    } while( 0 )

int mbedtls_internal_sha256_process_c( mbedtls_sha256_context *ctx,
                                const unsigned char data[SHA256_BLOCK_SIZE] )
{
    struct
    {
        uint32_t temp1, temp2, W[64];
        uint32_t A[8];
    } local;

    unsigned int i;

    SHA256_VALIDATE_RET( ctx != NULL );
    SHA256_VALIDATE_RET( (const unsigned char *)data != NULL );

    for( i = 0; i < 8; i++ )
        local.A[i] = ctx->state[i];

#if defined(MBEDTLS_SHA256_SMALLER)
    for( i = 0; i < 64; i++ )
    {
        if( i < 16 )
            local.W[i] = MBEDTLS_GET_UINT32_BE( data, 4 * i );
        else
            R( i );

        P( local.A[0], local.A[1], local.A[2], local.A[3], local.A[4],
           local.A[5], local.A[6], local.A[7], local.W[i], K[i] );

        local.temp1 = local.A[7]; local.A[7] = local.A[6];
        local.A[6] = local.A[5]; local.A[5] = local.A[4];
        local.A[4] = local.A[3]; local.A[3] = local.A[2];
        local.A[2] = local.A[1]; local.A[1] = local.A[0];
        local.A[0] = local.temp1;
    }
#else /* MBEDTLS_SHA256_SMALLER */
    for( i = 0; i < 16; i++ )
        local.W[i] = MBEDTLS_GET_UINT32_BE( data, 4 * i );

    for( i = 0; i < 16; i += 8 )
    {
        P( local.A[0], local.A[1], local.A[2], local.A[3], local.A[4],
           local.A[5], local.A[6], local.A[7], local.W[i+0], K[i+0] );
        P( local.A[7], local.A[0], local.A[1], local.A[2], local.A[3],
           local.A[4], local.A[5], local.A[6], local.W[i+1], K[i+1] );
        P( local.A[6], local.A[7], local.A[0], local.A[1], local.A[2],
           local.A[3], local.A[4], local.A[5], local.W[i+2], K[i+2] );
        P( local.A[5], local.A[6], local.A[7], local.A[0], local.A[1],
           local.A[2], local.A[3], local.A[4], local.W[i+3], K[i+3] );
        P( local.A[4], local.A[5], local.A[6], local.A[7], local.A[0],
           local.A[1], local.A[2], local.A[3], local.W[i+4], K[i+4] );
        P( local.A[3], local.A[4], local.A[5], local.A[6], local.A[7],
           local.A[0], local.A[1], local.A[2], local.W[i+5], K[i+5] );
        P( local.A[2], local.A[3], local.A[4], local.A[5], local.A[6],
           local.A[7], local.A[0], local.A[1], local.W[i+6], K[i+6] );
        P( local.A[1], local.A[2], local.A[3], local.A[4], local.A[5],
           local.A[6], local.A[7], local.A[0], local.W[i+7], K[i+7] );
    }

    for( i = 16; i < 64; i += 8 )
    {
        P( local.A[0], local.A[1], local.A[2], local.A[3], local.A[4],
           local.A[5], local.A[6], local.A[7], R(i+0), K[i+0] );
        P( local.A[7], local.A[0], local.A[1], local.A[2], local.A[3],
           local.A[4], local.A[5], local.A[6], R(i+1), K[i+1] );
        P( local.A[6], local.A[7], local.A[0], local.A[1], local.A[2],
           local.A[3], local.A[4], local.A[5], R(i+2), K[i+2] );
        P( local.A[5], local.A[6], local.A[7], local.A[0], local.A[1],
           local.A[2], local.A[3], local.A[4], R(i+3), K[i+3] );
        P( local.A[4], local.A[5], local.A[6], local.A[7], local.A[0],
           local.A[1], local.A[2], local.A[3], R(i+4), K[i+4] );
        P( local.A[3], local.A[4], local.A[5], local.A[6], local.A[7],
           local.A[0], local.A[1], local.A[2], R(i+5), K[i+5] );
        P( local.A[2], local.A[3], local.A[4], local.A[5], local.A[6],
           local.A[7], local.A[0], local.A[1], R(i+6), K[i+6] );
        P( local.A[1], local.A[2], local.A[3], local.A[4], local.A[5],
           local.A[6], local.A[7], local.A[0], R(i+7), K[i+7] );
    }
#endif /* MBEDTLS_SHA256_SMALLER */

    for( i = 0; i < 8; i++ )
        ctx->state[i] += local.A[i];

    /* Zeroise buffers and variables to clear sensitive data from memory. */
    mbedtls_platform_zeroize( &local, sizeof( local ) );

    return( 0 );
}

#endif /* !MBEDTLS_SHA256_PROCESS_ALT && !MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY */


#if !defined(MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY)

static size_t mbedtls_internal_sha256_process_many_c(
                  mbedtls_sha256_context *ctx, const uint8_t *data, size_t len )
{
    size_t processed = 0;

    while( len >= SHA256_BLOCK_SIZE )
    {
        if( mbedtls_internal_sha256_process_c( ctx, data ) != 0 )
            return( 0 );

        data += SHA256_BLOCK_SIZE;
        len  -= SHA256_BLOCK_SIZE;

        processed += SHA256_BLOCK_SIZE;
    }

    return( processed );
}

#endif /* !MBEDTLS_SHA256_USE_A64_CRYPTO_ONLY */


#if defined(MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT)

static int mbedtls_a64_crypto_sha256_has_support( void )
{
    static int done = 0;
    static int supported = 0;

    if( !done )
    {
        supported = mbedtls_a64_crypto_sha256_check_support();
        done = 1;
    }

    return( supported );
}

static size_t mbedtls_internal_sha256_process_many( mbedtls_sha256_context *ctx,
                  const uint8_t *msg, size_t len )
{
    if( mbedtls_a64_crypto_sha256_has_support() )
        return( mbedtls_internal_sha256_process_many_a64_crypto( ctx, msg, len ) );
    else
        return( mbedtls_internal_sha256_process_many_c( ctx, msg, len ) );
}

int mbedtls_internal_sha256_process( mbedtls_sha256_context *ctx,
        const unsigned char data[SHA256_BLOCK_SIZE] )
{
    if( mbedtls_a64_crypto_sha256_has_support() )
        return( mbedtls_internal_sha256_process_a64_crypto( ctx, data ) );
    else
        return( mbedtls_internal_sha256_process_c( ctx, data ) );
}

#endif /* MBEDTLS_SHA256_USE_A64_CRYPTO_IF_PRESENT */


/*
 * SHA-256 process buffer
 */
int mbedtls_sha256_update( mbedtls_sha256_context *ctx,
                               const unsigned char *input,
                               size_t ilen )
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t fill;
    uint32_t left;

    SHA256_VALIDATE_RET( ctx != NULL );
    SHA256_VALIDATE_RET( ilen == 0 || input != NULL );

    if( ilen == 0 )
        return( 0 );

    left = ctx->total[0] & 0x3F;
    fill = SHA256_BLOCK_SIZE - left;

    ctx->total[0] += (uint32_t) ilen;
    ctx->total[0] &= 0xFFFFFFFF;

    if( ctx->total[0] < (uint32_t) ilen )
        ctx->total[1]++;

    if( left && ilen >= fill )
    {
        memcpy( (void *) (ctx->buffer + left), input, fill );

        if( ( ret = mbedtls_internal_sha256_process( ctx, ctx->buffer ) ) != 0 )
            return( ret );

        input += fill;
        ilen  -= fill;
        left = 0;
    }

    while( ilen >= SHA256_BLOCK_SIZE )
    {
        size_t processed =
                    mbedtls_internal_sha256_process_many( ctx, input, ilen );
        if( processed < SHA256_BLOCK_SIZE )
            return( MBEDTLS_ERR_ERROR_GENERIC_ERROR );

        input += processed;
        ilen  -= processed;
    }

    if( ilen > 0 )
        memcpy( (void *) (ctx->buffer + left), input, ilen );

    return( 0 );
}

/*
 * SHA-256 final digest
 */
int mbedtls_sha256_finish( mbedtls_sha256_context *ctx,
                               unsigned char *output )
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    uint32_t used;
    uint32_t high, low;

    SHA256_VALIDATE_RET( ctx != NULL );
    SHA256_VALIDATE_RET( (unsigned char *)output != NULL );

    /*
     * Add padding: 0x80 then 0x00 until 8 bytes remain for the length
     */
    used = ctx->total[0] & 0x3F;

    ctx->buffer[used++] = 0x80;

    if( used <= 56 )
    {
        /* Enough room for padding + length in current block */
        memset( ctx->buffer + used, 0, 56 - used );
    }
    else
    {
        /* We'll need an extra block */
        memset( ctx->buffer + used, 0, SHA256_BLOCK_SIZE - used );

        if( ( ret = mbedtls_internal_sha256_process( ctx, ctx->buffer ) ) != 0 )
            return( ret );

        memset( ctx->buffer, 0, 56 );
    }

    /*
     * Add message length
     */
    high = ( ctx->total[0] >> 29 )
         | ( ctx->total[1] <<  3 );
    low  = ( ctx->total[0] <<  3 );

    MBEDTLS_PUT_UINT32_BE( high, ctx->buffer, 56 );
    MBEDTLS_PUT_UINT32_BE( low,  ctx->buffer, 60 );

    if( ( ret = mbedtls_internal_sha256_process( ctx, ctx->buffer ) ) != 0 )
        return( ret );

    /*
     * Output final state
     */
    MBEDTLS_PUT_UINT32_BE( ctx->state[0], output,  0 );
    MBEDTLS_PUT_UINT32_BE( ctx->state[1], output,  4 );
    MBEDTLS_PUT_UINT32_BE( ctx->state[2], output,  8 );
    MBEDTLS_PUT_UINT32_BE( ctx->state[3], output, 12 );
    MBEDTLS_PUT_UINT32_BE( ctx->state[4], output, 16 );
    MBEDTLS_PUT_UINT32_BE( ctx->state[5], output, 20 );
    MBEDTLS_PUT_UINT32_BE( ctx->state[6], output, 24 );

#if defined(MBEDTLS_SHA224_C)
    if( ctx->is224 == 0 )
#endif
        MBEDTLS_PUT_UINT32_BE( ctx->state[7], output, 28 );

    return( 0 );
}

#endif /* !MBEDTLS_SHA256_ALT */

/*
 * output = SHA-256( input buffer )
 */
int mbedtls_sha256( const unsigned char *input,
                        size_t ilen,
                        unsigned char *output,
                        int is224 )
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    mbedtls_sha256_context ctx;

#if defined(MBEDTLS_SHA224_C)
    SHA256_VALIDATE_RET( is224 == 0 || is224 == 1 );
#else
    SHA256_VALIDATE_RET( is224 == 0 );
#endif

    SHA256_VALIDATE_RET( ilen == 0 || input != NULL );
    SHA256_VALIDATE_RET( (unsigned char *)output != NULL );

    mbedtls_sha256_init( &ctx );

    if( ( ret = mbedtls_sha256_starts( &ctx, is224 ) ) != 0 )
        goto exit;

    if( ( ret = mbedtls_sha256_update( &ctx, input, ilen ) ) != 0 )
        goto exit;

    if( ( ret = mbedtls_sha256_finish( &ctx, output ) ) != 0 )
        goto exit;

exit:
    mbedtls_sha256_free( &ctx );

    return( ret );
}

#if defined(MBEDTLS_SELF_TEST)
/*
 * FIPS-180-2 test vectors
 */
static const unsigned char sha256_test_buf[3][57] =
{
    { "abc" },
    { "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq" },
    { "" }
};

static const size_t sha256_test_buflen[3] =
{
    3, 56, 1000
};

static const unsigned char sha256_test_sum[6][32] =
{
    /*
     * SHA-224 test vectors
     */
    { 0x23, 0x09, 0x7D, 0x22, 0x34, 0x05, 0xD8, 0x22,
      0x86, 0x42, 0xA4, 0x77, 0xBD, 0xA2, 0x55, 0xB3,
      0x2A, 0xAD, 0xBC, 0xE4, 0xBD, 0xA0, 0xB3, 0xF7,
      0xE3, 0x6C, 0x9D, 0xA7 },
    { 0x75, 0x38, 0x8B, 0x16, 0x51, 0x27, 0x76, 0xCC,
      0x5D, 0xBA, 0x5D, 0xA1, 0xFD, 0x89, 0x01, 0x50,
      0xB0, 0xC6, 0x45, 0x5C, 0xB4, 0xF5, 0x8B, 0x19,
      0x52, 0x52, 0x25, 0x25 },
    { 0x20, 0x79, 0x46, 0x55, 0x98, 0x0C, 0x91, 0xD8,
      0xBB, 0xB4, 0xC1, 0xEA, 0x97, 0x61, 0x8A, 0x4B,
      0xF0, 0x3F, 0x42, 0x58, 0x19, 0x48, 0xB2, 0xEE,
      0x4E, 0xE7, 0xAD, 0x67 },

    /*
     * SHA-256 test vectors
     */
    { 0xBA, 0x78, 0x16, 0xBF, 0x8F, 0x01, 0xCF, 0xEA,
      0x41, 0x41, 0x40, 0xDE, 0x5D, 0xAE, 0x22, 0x23,
      0xB0, 0x03, 0x61, 0xA3, 0x96, 0x17, 0x7A, 0x9C,
      0xB4, 0x10, 0xFF, 0x61, 0xF2, 0x00, 0x15, 0xAD },
    { 0x24, 0x8D, 0x6A, 0x61, 0xD2, 0x06, 0x38, 0xB8,
      0xE5, 0xC0, 0x26, 0x93, 0x0C, 0x3E, 0x60, 0x39,
      0xA3, 0x3C, 0xE4, 0x59, 0x64, 0xFF, 0x21, 0x67,
      0xF6, 0xEC, 0xED, 0xD4, 0x19, 0xDB, 0x06, 0xC1 },
    { 0xCD, 0xC7, 0x6E, 0x5C, 0x99, 0x14, 0xFB, 0x92,
      0x81, 0xA1, 0xC7, 0xE2, 0x84, 0xD7, 0x3E, 0x67,
      0xF1, 0x80, 0x9A, 0x48, 0xA4, 0x97, 0x20, 0x0E,
      0x04, 0x6D, 0x39, 0xCC, 0xC7, 0x11, 0x2C, 0xD0 }
};

/*
 * Checkup routine
 */
int mbedtls_sha256_self_test( int verbose )
{
    int i, j, k, buflen, ret = 0;
    unsigned char *buf;
    unsigned char sha256sum[32];
    mbedtls_sha256_context ctx;

    buf = mbedtls_calloc( 1024, sizeof(unsigned char) );
    if( NULL == buf )
    {
        if( verbose != 0 )
            mbedtls_printf( "Buffer allocation failed\n" );

        return( 1 );
    }

    mbedtls_sha256_init( &ctx );

    for( i = 0; i < 6; i++ )
    {
        j = i % 3;
        k = i < 3;

        if( verbose != 0 )
            mbedtls_printf( "  SHA-%d test #%d: ", 256 - k * 32, j + 1 );

        if( ( ret = mbedtls_sha256_starts( &ctx, k ) ) != 0 )
            goto fail;

        if( j == 2 )
        {
            memset( buf, 'a', buflen = 1000 );

            for( j = 0; j < 1000; j++ )
            {
                ret = mbedtls_sha256_update( &ctx, buf, buflen );
                if( ret != 0 )
                    goto fail;
            }

        }
        else
        {
            ret = mbedtls_sha256_update( &ctx, sha256_test_buf[j],
                                             sha256_test_buflen[j] );
            if( ret != 0 )
                 goto fail;
        }

        if( ( ret = mbedtls_sha256_finish( &ctx, sha256sum ) ) != 0 )
            goto fail;


        if( memcmp( sha256sum, sha256_test_sum[i], 32 - k * 4 ) != 0 )
        {
            ret = 1;
            goto fail;
        }

        if( verbose != 0 )
            mbedtls_printf( "passed\n" );
    }

    if( verbose != 0 )
        mbedtls_printf( "\n" );

    goto exit;

fail:
    if( verbose != 0 )
        mbedtls_printf( "failed\n" );

exit:
    mbedtls_sha256_free( &ctx );
    mbedtls_free( buf );

    return( ret );
}

#endif /* MBEDTLS_SELF_TEST */

#endif /* MBEDTLS_SHA256_C */