File: aes.c

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/*
 *  FIPS-197 compliant AES implementation
 *
 *  Copyright (C) 2011, Con Kolivas <kernel@kolivas.org>
 *  Copyright (C) 2006-2010, Brainspark B.V.
 *
 *  This file is part of PolarSSL (http://www.polarssl.org)
 *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
 *
 *  All rights reserved.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
/*
 *  The AES block cipher was designed by Vincent Rijmen and Joan Daemen.
 *
 *  http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf
 *  http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
 */

#include "aes.h"

#include <string.h>

/*
 * 32-bit integer manipulation macros (little endian)
 */
#ifndef GET_ULONG_LE
#define GET_ULONG_LE(n,b,i)                             \
{                                                       \
    (n) = ( (unsigned long) (b)[(i)    ]       )        \
        | ( (unsigned long) (b)[(i) + 1] <<  8 )        \
        | ( (unsigned long) (b)[(i) + 2] << 16 )        \
        | ( (unsigned long) (b)[(i) + 3] << 24 );       \
}
#endif

#ifndef PUT_ULONG_LE
#define PUT_ULONG_LE(n,b,i)                             \
{                                                       \
    (b)[(i)    ] = (unsigned char) ( (n)       );       \
    (b)[(i) + 1] = (unsigned char) ( (n) >>  8 );       \
    (b)[(i) + 2] = (unsigned char) ( (n) >> 16 );       \
    (b)[(i) + 3] = (unsigned char) ( (n) >> 24 );       \
}
#endif

/*
 * Forward S-box & tables
 */
static unsigned char FSb[256];
static unsigned long FT0[256];
static unsigned long FT1[256];
static unsigned long FT2[256];
static unsigned long FT3[256];

/*
 * Reverse S-box & tables
 */
static unsigned char RSb[256];
static unsigned long RT0[256];
static unsigned long RT1[256];
static unsigned long RT2[256];
static unsigned long RT3[256];

/*
 * Round constants
 */
static unsigned long RCON[10];

/*
 * Tables generation code
 */
#define ROTL8(x) ( ( x << 8 ) & 0xFFFFFFFF ) | ( x >> 24 )
#define XTIME(x) ( ( x << 1 ) ^ ( ( x & 0x80 ) ? 0x1B : 0x00 ) )
#define MUL(x,y) ( ( x && y ) ? pow[(log[x]+log[y]) % 255] : 0 )

static int aes_init_done = 0;

static void aes_gen_tables( void )
{
    int i, x, y, z;
    int pow[256];
    int log[256];

    /*
     * compute pow and log tables over GF(2^8)
     */
    for( i = 0, x = 1; i < 256; i++ )
    {
        pow[i] = x;
        log[x] = i;
        x = ( x ^ XTIME( x ) ) & 0xFF;
    }

    /*
     * calculate the round constants
     */
    for( i = 0, x = 1; i < 10; i++ )
    {
        RCON[i] = (unsigned long) x;
        x = XTIME( x ) & 0xFF;
    }

    /*
     * generate the forward and reverse S-boxes
     */
    FSb[0x00] = 0x63;
    RSb[0x63] = 0x00;

    for( i = 1; i < 256; i++ )
    {
        x = pow[255 - log[i]];

        y  = x; y = ( (y << 1) | (y >> 7) ) & 0xFF;
        x ^= y; y = ( (y << 1) | (y >> 7) ) & 0xFF;
        x ^= y; y = ( (y << 1) | (y >> 7) ) & 0xFF;
        x ^= y; y = ( (y << 1) | (y >> 7) ) & 0xFF;
        x ^= y ^ 0x63;

        FSb[i] = (unsigned char) x;
        RSb[x] = (unsigned char) i;
    }

    /*
     * generate the forward and reverse tables
     */
    for( i = 0; i < 256; i++ )
    {
        x = FSb[i];
        y = XTIME( x ) & 0xFF;
        z =  ( y ^ x ) & 0xFF;

        FT0[i] = ( (unsigned long) y       ) ^
                 ( (unsigned long) x <<  8 ) ^
                 ( (unsigned long) x << 16 ) ^
                 ( (unsigned long) z << 24 );

        FT1[i] = ROTL8( FT0[i] );
        FT2[i] = ROTL8( FT1[i] );
        FT3[i] = ROTL8( FT2[i] );

        x = RSb[i];

        RT0[i] = ( (unsigned long) MUL( 0x0E, x )       ) ^
                 ( (unsigned long) MUL( 0x09, x ) <<  8 ) ^
                 ( (unsigned long) MUL( 0x0D, x ) << 16 ) ^
                 ( (unsigned long) MUL( 0x0B, x ) << 24 );

        RT1[i] = ROTL8( RT0[i] );
        RT2[i] = ROTL8( RT1[i] );
        RT3[i] = ROTL8( RT2[i] );
    }
}

/*
 * AES key schedule (encryption)
 */
int aes_setkey_enc( aes_context *ctx, const unsigned char *key, int keysize )
{
    int i;
    unsigned long *RK;

#if !defined(POLARSSL_AES_ROM_TABLES)
    if( aes_init_done == 0 )
    {
        aes_gen_tables();
        aes_init_done = 1;
    }
#endif

    switch( keysize )
    {
        case 128: ctx->nr = 10; break;
        case 192: ctx->nr = 12; break;
        case 256: ctx->nr = 14; break;
        default : return( POLARSSL_ERR_AES_INVALID_KEY_LENGTH );
    }

#if defined(PADLOCK_ALIGN16)
    ctx->rk = RK = PADLOCK_ALIGN16( ctx->buf );
#else
    ctx->rk = RK = ctx->buf;
#endif

    for( i = 0; i < (keysize >> 5); i++ )
    {
        GET_ULONG_LE( RK[i], key, i << 2 );
    }

    switch( ctx->nr )
    {
        case 10:

            for( i = 0; i < 10; i++, RK += 4 )
            {
                RK[4]  = RK[0] ^ RCON[i] ^
                ( (unsigned long) FSb[ ( RK[3] >>  8 ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( RK[3] >> 16 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( RK[3] >> 24 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( RK[3]       ) & 0xFF ] << 24 );

                RK[5]  = RK[1] ^ RK[4];
                RK[6]  = RK[2] ^ RK[5];
                RK[7]  = RK[3] ^ RK[6];
            }
            break;

        case 12:

            for( i = 0; i < 8; i++, RK += 6 )
            {
                RK[6]  = RK[0] ^ RCON[i] ^
                ( (unsigned long) FSb[ ( RK[5] >>  8 ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( RK[5] >> 16 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( RK[5] >> 24 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( RK[5]       ) & 0xFF ] << 24 );

                RK[7]  = RK[1] ^ RK[6];
                RK[8]  = RK[2] ^ RK[7];
                RK[9]  = RK[3] ^ RK[8];
                RK[10] = RK[4] ^ RK[9];
                RK[11] = RK[5] ^ RK[10];
            }
            break;

        case 14:

            for( i = 0; i < 7; i++, RK += 8 )
            {
                RK[8]  = RK[0] ^ RCON[i] ^
                ( (unsigned long) FSb[ ( RK[7] >>  8 ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( RK[7] >> 16 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( RK[7] >> 24 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( RK[7]       ) & 0xFF ] << 24 );

                RK[9]  = RK[1] ^ RK[8];
                RK[10] = RK[2] ^ RK[9];
                RK[11] = RK[3] ^ RK[10];

                RK[12] = RK[4] ^
                ( (unsigned long) FSb[ ( RK[11]       ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( RK[11] >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( RK[11] >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( RK[11] >> 24 ) & 0xFF ] << 24 );

                RK[13] = RK[5] ^ RK[12];
                RK[14] = RK[6] ^ RK[13];
                RK[15] = RK[7] ^ RK[14];
            }
            break;

        default:

            break;
    }

    return( 0 );
}

/*
 * AES key schedule (decryption)
 */
int aes_setkey_dec( aes_context *ctx, const unsigned char *key, int keysize )
{
    int i, j;
    aes_context cty;
    unsigned long *RK;
    unsigned long *SK;
    int ret;

    switch( keysize )
    {
        case 128: ctx->nr = 10; break;
        case 192: ctx->nr = 12; break;
        case 256: ctx->nr = 14; break;
        default : return( POLARSSL_ERR_AES_INVALID_KEY_LENGTH );
    }

#if defined(PADLOCK_ALIGN16)
    ctx->rk = RK = PADLOCK_ALIGN16( ctx->buf );
#else
    ctx->rk = RK = ctx->buf;
#endif

    ret = aes_setkey_enc( &cty, key, keysize );
    if( ret != 0 )
        return( ret );

    SK = cty.rk + cty.nr * 4;

    *RK++ = *SK++;
    *RK++ = *SK++;
    *RK++ = *SK++;
    *RK++ = *SK++;

    for( i = ctx->nr - 1, SK -= 8; i > 0; i--, SK -= 8 )
    {
        for( j = 0; j < 4; j++, SK++ )
        {
            *RK++ = RT0[ FSb[ ( *SK       ) & 0xFF ] ] ^
                    RT1[ FSb[ ( *SK >>  8 ) & 0xFF ] ] ^
                    RT2[ FSb[ ( *SK >> 16 ) & 0xFF ] ] ^
                    RT3[ FSb[ ( *SK >> 24 ) & 0xFF ] ];
        }
    }

    *RK++ = *SK++;
    *RK++ = *SK++;
    *RK++ = *SK++;
    *RK++ = *SK++;

    memset( &cty, 0, sizeof( aes_context ) );

    return( 0 );
}

#define AES_FROUND(X0,X1,X2,X3,Y0,Y1,Y2,Y3)     \
{                                               \
    X0 = *RK++ ^ FT0[ ( Y0       ) & 0xFF ] ^   \
                 FT1[ ( Y1 >>  8 ) & 0xFF ] ^   \
                 FT2[ ( Y2 >> 16 ) & 0xFF ] ^   \
                 FT3[ ( Y3 >> 24 ) & 0xFF ];    \
                                                \
    X1 = *RK++ ^ FT0[ ( Y1       ) & 0xFF ] ^   \
                 FT1[ ( Y2 >>  8 ) & 0xFF ] ^   \
                 FT2[ ( Y3 >> 16 ) & 0xFF ] ^   \
                 FT3[ ( Y0 >> 24 ) & 0xFF ];    \
                                                \
    X2 = *RK++ ^ FT0[ ( Y2       ) & 0xFF ] ^   \
                 FT1[ ( Y3 >>  8 ) & 0xFF ] ^   \
                 FT2[ ( Y0 >> 16 ) & 0xFF ] ^   \
                 FT3[ ( Y1 >> 24 ) & 0xFF ];    \
                                                \
    X3 = *RK++ ^ FT0[ ( Y3       ) & 0xFF ] ^   \
                 FT1[ ( Y0 >>  8 ) & 0xFF ] ^   \
                 FT2[ ( Y1 >> 16 ) & 0xFF ] ^   \
                 FT3[ ( Y2 >> 24 ) & 0xFF ];    \
}

#define AES_RROUND(X0,X1,X2,X3,Y0,Y1,Y2,Y3)     \
{                                               \
    X0 = *RK++ ^ RT0[ ( Y0       ) & 0xFF ] ^   \
                 RT1[ ( Y3 >>  8 ) & 0xFF ] ^   \
                 RT2[ ( Y2 >> 16 ) & 0xFF ] ^   \
                 RT3[ ( Y1 >> 24 ) & 0xFF ];    \
                                                \
    X1 = *RK++ ^ RT0[ ( Y1       ) & 0xFF ] ^   \
                 RT1[ ( Y0 >>  8 ) & 0xFF ] ^   \
                 RT2[ ( Y3 >> 16 ) & 0xFF ] ^   \
                 RT3[ ( Y2 >> 24 ) & 0xFF ];    \
                                                \
    X2 = *RK++ ^ RT0[ ( Y2       ) & 0xFF ] ^   \
                 RT1[ ( Y1 >>  8 ) & 0xFF ] ^   \
                 RT2[ ( Y0 >> 16 ) & 0xFF ] ^   \
                 RT3[ ( Y3 >> 24 ) & 0xFF ];    \
                                                \
    X3 = *RK++ ^ RT0[ ( Y3       ) & 0xFF ] ^   \
                 RT1[ ( Y2 >>  8 ) & 0xFF ] ^   \
                 RT2[ ( Y1 >> 16 ) & 0xFF ] ^   \
                 RT3[ ( Y0 >> 24 ) & 0xFF ];    \
}

/*
 * AES-ECB block encryption/decryption
 */
int aes_crypt_ecb( aes_context *ctx,
                    int mode,
                    const unsigned char input[16],
                    unsigned char output[16] )
{
    int i;
    unsigned long *RK, X0, X1, X2, X3, Y0, Y1, Y2, Y3;

#if defined(POLARSSL_PADLOCK_C) && defined(POLARSSL_HAVE_X86)
    if( padlock_supports( PADLOCK_ACE ) )
    {
        if( padlock_xcryptecb( ctx, mode, input, output ) == 0 )
            return( 0 );

        // If padlock data misaligned, we just fall back to
        // unaccelerated mode
        //
    }
#endif

    RK = ctx->rk;

    GET_ULONG_LE( X0, input,  0 ); X0 ^= *RK++;
    GET_ULONG_LE( X1, input,  4 ); X1 ^= *RK++;
    GET_ULONG_LE( X2, input,  8 ); X2 ^= *RK++;
    GET_ULONG_LE( X3, input, 12 ); X3 ^= *RK++;

    if( mode == AES_DECRYPT )
    {
        for( i = (ctx->nr >> 1) - 1; i > 0; i-- )
        {
            AES_RROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 );
            AES_RROUND( X0, X1, X2, X3, Y0, Y1, Y2, Y3 );
        }

        AES_RROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 );

        X0 = *RK++ ^ \
                ( (unsigned long) RSb[ ( Y0       ) & 0xFF ]       ) ^
                ( (unsigned long) RSb[ ( Y3 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) RSb[ ( Y2 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) RSb[ ( Y1 >> 24 ) & 0xFF ] << 24 );

        X1 = *RK++ ^ \
                ( (unsigned long) RSb[ ( Y1       ) & 0xFF ]       ) ^
                ( (unsigned long) RSb[ ( Y0 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) RSb[ ( Y3 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) RSb[ ( Y2 >> 24 ) & 0xFF ] << 24 );

        X2 = *RK++ ^ \
                ( (unsigned long) RSb[ ( Y2       ) & 0xFF ]       ) ^
                ( (unsigned long) RSb[ ( Y1 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) RSb[ ( Y0 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) RSb[ ( Y3 >> 24 ) & 0xFF ] << 24 );

        X3 = *RK++ ^ \
                ( (unsigned long) RSb[ ( Y3       ) & 0xFF ]       ) ^
                ( (unsigned long) RSb[ ( Y2 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) RSb[ ( Y1 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) RSb[ ( Y0 >> 24 ) & 0xFF ] << 24 );
    }
    else /* AES_ENCRYPT */
    {
        for( i = (ctx->nr >> 1) - 1; i > 0; i-- )
        {
            AES_FROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 );
            AES_FROUND( X0, X1, X2, X3, Y0, Y1, Y2, Y3 );
        }

        AES_FROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 );

        X0 = *RK++ ^ \
                ( (unsigned long) FSb[ ( Y0       ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( Y1 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( Y2 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( Y3 >> 24 ) & 0xFF ] << 24 );

        X1 = *RK++ ^ \
                ( (unsigned long) FSb[ ( Y1       ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( Y2 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( Y3 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( Y0 >> 24 ) & 0xFF ] << 24 );

        X2 = *RK++ ^ \
                ( (unsigned long) FSb[ ( Y2       ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( Y3 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( Y0 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( Y1 >> 24 ) & 0xFF ] << 24 );

        X3 = *RK++ ^ \
                ( (unsigned long) FSb[ ( Y3       ) & 0xFF ]       ) ^
                ( (unsigned long) FSb[ ( Y0 >>  8 ) & 0xFF ] <<  8 ) ^
                ( (unsigned long) FSb[ ( Y1 >> 16 ) & 0xFF ] << 16 ) ^
                ( (unsigned long) FSb[ ( Y2 >> 24 ) & 0xFF ] << 24 );
    }

    PUT_ULONG_LE( X0, output,  0 );
    PUT_ULONG_LE( X1, output,  4 );
    PUT_ULONG_LE( X2, output,  8 );
    PUT_ULONG_LE( X3, output, 12 );

    return( 0 );
}

/*
 * AES-CBC buffer encryption/decryption
 */
int aes_crypt_cbc( aes_context *ctx,
                    int mode,
                    long long int length,
                    unsigned char iv[16],
                    const unsigned char *input,
                    unsigned char *output )
{
    int i;
    unsigned char temp[16];

    if( length % 16 )
        return( POLARSSL_ERR_AES_INVALID_INPUT_LENGTH );

#if defined(POLARSSL_PADLOCK_C) && defined(POLARSSL_HAVE_X86)
    if( padlock_supports( PADLOCK_ACE ) )
    {
        if( padlock_xcryptcbc( ctx, mode, length, iv, input, output ) == 0 )
            return( 0 );

        // If padlock data misaligned, we just fall back to
        // unaccelerated mode
        //
    }
#endif

    if( mode == AES_DECRYPT )
    {
        while( length > 0 )
        {
            memcpy( temp, input, 16 );
            aes_crypt_ecb( ctx, mode, input, output );

            for( i = 0; i < 16; i++ )
                output[i] = (unsigned char)( output[i] ^ iv[i] );

            memcpy( iv, temp, 16 );

            input  += 16;
            output += 16;
            length -= 16;
        }
    }
    else
    {
        while( length > 0 )
        {
            for( i = 0; i < 16; i++ )
                output[i] = (unsigned char)( input[i] ^ iv[i] );

            aes_crypt_ecb( ctx, mode, output, output );
            memcpy( iv, output, 16 );

            input  += 16;
            output += 16;
            length -= 16;
        }
    }

    return( 0 );
}