library/poly1305.c

/**
 * \file poly1305.c
 *
 * \brief Poly1305 authentication algorithm.
 *
 *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
 *  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.
 *
 *  This file is part of mbed TLS (https://tls.mbed.org)
 */
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_POLY1305_C)

#if !defined(MBEDTLS_POLY1305_ALT)

#include "mbedtls/poly1305.h"

#include <string.h>

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

#define POLY1305_BLOCK_SIZE_BYTES ( 16U )

#define BYTES_TO_U32_LE( data, offset )                   \
    ( (uint32_t)data[offset] |                            \
      (uint32_t)( (uint32_t)data[(offset) + 1] << 8 )  |  \
      (uint32_t)( (uint32_t)data[(offset) + 2] << 16 ) |  \
      (uint32_t)( (uint32_t)data[(offset) + 3] << 24 )    \
    )

/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize( void *v, size_t n ) {
    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}

/**
 * \brief                   Process blocks with Poly1305.
 *
 * \param ctx               The Poly1305 context.
 * \param nblocks           Number of blocks to process. Note that this function
 *                          only processes full blocks.
 * \param input             Buffer containing the input block(s).
 * \param needs_padding     Set to 0 if the padding bit has already been applied
 *                          to the input data before calling this function.
 *                          Otherwise, set this parameter to 1.
 */
static void mbedtls_poly1305_process( mbedtls_poly1305_context *ctx,
                                      size_t nblocks,
                                      const unsigned char *input,
                                      uint32_t needs_padding )
{
    uint64_t d0, d1, d2, d3;
    uint32_t acc0, acc1, acc2, acc3, acc4;
    uint32_t r0, r1, r2, r3;
    uint32_t rs1, rs2, rs3;
    size_t offset  = 0U;
    size_t i;

    r0 = ctx->r[0];
    r1 = ctx->r[1];
    r2 = ctx->r[2];
    r3 = ctx->r[3];

    rs1 = r1 + ( r1 >> 2U );
    rs2 = r2 + ( r2 >> 2U );
    rs3 = r3 + ( r3 >> 2U );

    acc0 = ctx->acc[0];
    acc1 = ctx->acc[1];
    acc2 = ctx->acc[2];
    acc3 = ctx->acc[3];
    acc4 = ctx->acc[4];

    /* Process full blocks */
    for ( i = 0U; i < nblocks; i++ )
    {
        /* Compute: acc += block */
        /* Note that the input block is treated as a 128-bit little-endian integer */
        d0   = (uint64_t)acc0 + BYTES_TO_U32_LE( input, offset + 0  );
        d1   = (uint64_t)acc1 + BYTES_TO_U32_LE( input, offset + 4  ) + ( d0 >> 32U );
        d2   = (uint64_t)acc2 + BYTES_TO_U32_LE( input, offset + 8  ) + ( d1 >> 32U );
        d3   = (uint64_t)acc3 + BYTES_TO_U32_LE( input, offset + 12 ) + ( d2 >> 32U );
        acc0 = (uint32_t)d0;
        acc1 = (uint32_t)d1;
        acc2 = (uint32_t)d2;
        acc3 = (uint32_t)d3;
        acc4 += (uint32_t)( d3 >> 32U ) + needs_padding;

        /* Compute: acc *= r */
        d0 = ( (uint64_t)acc0 * r0  ) +
             ( (uint64_t)acc1 * rs3 ) +
             ( (uint64_t)acc2 * rs2 ) +
             ( (uint64_t)acc3 * rs1 );
        d1 = ( (uint64_t)acc0 * r1  ) +
             ( (uint64_t)acc1 * r0  ) +
             ( (uint64_t)acc2 * rs3 ) +
             ( (uint64_t)acc3 * rs2 ) +
             ( (uint64_t)acc4 * rs1 );
        d2 = ( (uint64_t)acc0 * r2  ) +
             ( (uint64_t)acc1 * r1  ) +
             ( (uint64_t)acc2 * r0  ) +
             ( (uint64_t)acc3 * rs3 ) +
             ( (uint64_t)acc4 * rs2 );
        d3 = ( (uint64_t)acc0 * r3  ) +
             ( (uint64_t)acc1 * r2  ) +
             ( (uint64_t)acc2 * r1  ) +
             ( (uint64_t)acc3 * r0  ) +
             ( (uint64_t)acc4 * rs3 );
        acc4 *= r0;

        /* Compute: acc %= (2^130 - 5) (partial remainder) */
        d1 += ( d0 >> 32 );
        d2 += ( d1 >> 32 );
        d3 += ( d2 >> 32 );
        acc0 = (uint32_t)d0;
        acc1 = (uint32_t)d1;
        acc2 = (uint32_t)d2;
        acc3 = (uint32_t)d3;
        acc4 = (uint32_t)( d3 >> 32 ) + acc4;

        d0 = (uint64_t)acc0 + ( acc4 >> 2 ) + ( acc4 & 0xFFFFFFFCU );
        acc4 &= 3U;
        acc0 = (uint32_t)d0;
        d0 = (uint64_t)acc1 + ( d0 >> 32U );
        acc1 = (uint32_t)d0;
        d0 = (uint64_t)acc2 + ( d0 >> 32U );
        acc2 = (uint32_t)d0;
        d0 = (uint64_t)acc3 + ( d0 >> 32U );
        acc3 = (uint32_t)d0;
        d0 = (uint64_t)acc4 + ( d0 >> 32U );
        acc4 = (uint32_t)d0;

        offset    += POLY1305_BLOCK_SIZE_BYTES;
    }

    ctx->acc[0] = acc0;
    ctx->acc[1] = acc1;
    ctx->acc[2] = acc2;
    ctx->acc[3] = acc3;
    ctx->acc[4] = acc4;
}

/**
 * \brief                   Compute the Poly1305 MAC
 *
 * \param ctx               The Poly1305 context.
 * \param mac               The buffer to where the MAC is written. Must be
 *                          big enough to contain the 16-byte MAC.
 */
static void mbedtls_poly1305_compute_mac( const mbedtls_poly1305_context *ctx,
                                          unsigned char mac[16] )
{
    uint64_t d;
    uint32_t g0, g1, g2, g3, g4;
    uint32_t acc0, acc1, acc2, acc3, acc4;
    uint32_t mask;
    uint32_t mask_inv;

    acc0 = ctx->acc[0];
    acc1 = ctx->acc[1];
    acc2 = ctx->acc[2];
    acc3 = ctx->acc[3];
    acc4 = ctx->acc[4];

    /* Before adding 's' we need to ensure that the accumulator is mod 2^130 - 5.
     * We do this by calculating acc - (2^130 - 5), then checking if
     * the 131st bit is set. If it is, then reduce: acc -= (2^130 - 5)
     */

    /* Calculate acc + -(2^130 - 5) */
    d  = ( (uint64_t)acc0 + 5U );
    g0 = (uint32_t)d;
    d  = ( (uint64_t)acc1 + ( d >> 32 ) );
    g1 = (uint32_t)d;
    d  = ( (uint64_t)acc2 + ( d >> 32 ) );
    g2 = (uint32_t)d;
    d  = ( (uint64_t)acc3 + ( d >> 32 ) );
    g3 = (uint32_t)d;
    g4 = acc4 + (uint32_t)( d >> 32U );

    /* mask == 0xFFFFFFFF if 131st bit is set, otherwise mask == 0 */
    mask = (uint32_t)0U - ( g4 >> 2U );
    mask_inv = ~mask;

    /* If 131st bit is set then acc=g, otherwise, acc is unmodified */
    acc0 = ( acc0 & mask_inv ) | ( g0 & mask );
    acc1 = ( acc1 & mask_inv ) | ( g1 & mask );
    acc2 = ( acc2 & mask_inv ) | ( g2 & mask );
    acc3 = ( acc3 & mask_inv ) | ( g3 & mask );

    /* Add 's' */
    d = (uint64_t)acc0 + ctx->s[0];
    acc0 = (uint32_t)d;
    d = (uint64_t)acc1 + ctx->s[1] + ( d >> 32U );
    acc1 = (uint32_t)d;
    d = (uint64_t)acc2 + ctx->s[2] + ( d >> 32U );
    acc2 = (uint32_t)d;
    acc3 += ctx->s[3] + (uint32_t)( d >> 32U );

    /* Compute MAC (128 least significant bits of the accumulator) */
    mac[0]  = (uint8_t)acc0;
    mac[1]  = (uint8_t)( acc0 >> 8  );
    mac[2]  = (uint8_t)( acc0 >> 16 );
    mac[3]  = (uint8_t)( acc0 >> 24 );
    mac[4]  = (uint8_t)acc1;
    mac[5]  = (uint8_t)( acc1 >> 8  );
    mac[6]  = (uint8_t)( acc1 >> 16 );
    mac[7]  = (uint8_t)( acc1 >> 24 );
    mac[8]  = (uint8_t)acc2;
    mac[9]  = (uint8_t)( acc2 >> 8  );
    mac[10] = (uint8_t)( acc2 >> 16 );
    mac[11] = (uint8_t)( acc2 >> 24 );
    mac[12] = (uint8_t)acc3;
    mac[13] = (uint8_t)( acc3 >> 8  );
    mac[14] = (uint8_t)( acc3 >> 16 );
    mac[15] = (uint8_t)( acc3 >> 24 );
}

void mbedtls_poly1305_init( mbedtls_poly1305_context *ctx )
{
    if ( ctx != NULL )
    {
        mbedtls_zeroize( ctx, sizeof(mbedtls_poly1305_context) );
    }
}

void mbedtls_poly1305_free( mbedtls_poly1305_context *ctx )
{
    if ( ctx != NULL )
    {
        mbedtls_zeroize( ctx, sizeof(mbedtls_poly1305_context) );
    }
}

int mbedtls_poly1305_setkey( mbedtls_poly1305_context *ctx,
                             const unsigned char key[32] )
{
    if ( ctx == NULL )
    {
        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
    }

    /* r &= 0x0ffffffc0ffffffc0ffffffc0fffffff */
    ctx->r[0] = BYTES_TO_U32_LE( key, 0 )  & 0x0FFFFFFFU;
    ctx->r[1] = BYTES_TO_U32_LE( key, 4 )  & 0x0FFFFFFCU;
    ctx->r[2] = BYTES_TO_U32_LE( key, 8 )  & 0x0FFFFFFCU;
    ctx->r[3] = BYTES_TO_U32_LE( key, 12 ) & 0x0FFFFFFCU;

    ctx->s[0] = BYTES_TO_U32_LE( key, 16 );
    ctx->s[1] = BYTES_TO_U32_LE( key, 20 );
    ctx->s[2] = BYTES_TO_U32_LE( key, 24 );
    ctx->s[3] = BYTES_TO_U32_LE( key, 28 );

    /* Initial accumulator state */
    ctx->acc[0] = 0U;
    ctx->acc[1] = 0U;
    ctx->acc[2] = 0U;
    ctx->acc[3] = 0U;

    return 0;
}

int mbedtls_poly1305_update( mbedtls_poly1305_context *ctx,
                             size_t ilen,
                             const unsigned char* input )
{
    size_t offset    = 0U;
    size_t remaining = ilen;
    size_t queue_free_len;
    size_t nblocks;

    if ( ctx == NULL )
    {
        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
    }
    else if ( ( ilen > 0U ) && ( input == NULL ) )
    {
        /* input pointer is allowed to be NULL only if ilen == 0 */
        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
    }

    if ( ( remaining > 0U ) && ( ctx->queue_len > 0U ) )
    {
        queue_free_len = ( POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );

        if ( ilen < queue_free_len )
        {
            /* Not enough data to complete the block.
             * Store this data with the other leftovers.
             */
            memcpy( &ctx->queue[ctx->queue_len],
                    input,
                    ilen );

            ctx->queue_len += ilen;

            remaining = 0U;
        }
        else
        {
            /* Enough data to produce a complete block */
            memcpy( &ctx->queue[ctx->queue_len],
                    input,
                    queue_free_len );

            ctx->queue_len = 0U;

            mbedtls_poly1305_process( ctx,
                                      1U,
                                      ctx->queue,
                                      1U ); /* add padding bit */

            offset    += queue_free_len;
            remaining -= queue_free_len;
        }
    }

    if ( remaining >= POLY1305_BLOCK_SIZE_BYTES )
    {
        nblocks = remaining / POLY1305_BLOCK_SIZE_BYTES;

        mbedtls_poly1305_process( ctx, nblocks, &input[offset], 1U );

        offset += nblocks * POLY1305_BLOCK_SIZE_BYTES;
        remaining %= POLY1305_BLOCK_SIZE_BYTES;
    }

    if ( remaining > 0U )
    {
        /* Store partial block */
        ctx->queue_len = remaining;
        memcpy( ctx->queue, &input[offset], remaining );
    }

    return( 0 );
}

int mbedtls_poly1305_finish( mbedtls_poly1305_context *ctx,
                             unsigned char mac[16] )
{
    if ( ( ctx == NULL ) || ( mac == NULL ) )
    {
        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
    }

    /* Process any leftover data */
    if ( ctx->queue_len > 0U )
    {
        /* Add padding bit */
        ctx->queue[ctx->queue_len] = 1U;
        ctx->queue_len++;

        /* Pad with zeroes */
        memset( &ctx->queue[ctx->queue_len],
                0,
                POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );

        mbedtls_poly1305_process( ctx,
                                  1U,           /* Process 1 block */
                                  ctx->queue,
                                  0U );         /* Don't add padding bit (it was just added above) */
    }

    mbedtls_poly1305_compute_mac( ctx, mac );

    return( 0 );
}

#endif /* MBEDTLS_POLY1305_ALT */

int mbedtls_poly1305_mac( const unsigned char key[32],
                           size_t ilen,
                           const unsigned char *input,
                           unsigned char mac[16] )
{
    mbedtls_poly1305_context ctx;
    int result;

    mbedtls_poly1305_init( &ctx );

    result = mbedtls_poly1305_setkey( &ctx, key );
    if ( result != 0 )
        goto cleanup;

    result = mbedtls_poly1305_update( &ctx, ilen, input );
    if ( result != 0 )
        goto cleanup;

    result = mbedtls_poly1305_finish( &ctx, mac );

cleanup:
    mbedtls_poly1305_free( &ctx );
    return( 0 );
}

#if defined(MBEDTLS_SELF_TEST)

static const unsigned char test_keys[2][32] =
{
    {
        0x85, 0xd6, 0xbe, 0x78, 0x57, 0x55, 0x6d, 0x33,
        0x7f, 0x44, 0x52, 0xfe, 0x42, 0xd5, 0x06, 0xa8,
        0x01, 0x03, 0x80, 0x8a, 0xfb, 0x0d, 0xb2, 0xfd,
        0x4a, 0xbf, 0xf6, 0xaf, 0x41, 0x49, 0xf5, 0x1b
    },
    {
        0x1c, 0x92, 0x40, 0xa5, 0xeb, 0x55, 0xd3, 0x8a,
        0xf3, 0x33, 0x88, 0x86, 0x04, 0xf6, 0xb5, 0xf0,
        0x47, 0x39, 0x17, 0xc1, 0x40, 0x2b, 0x80, 0x09,
        0x9d, 0xca, 0x5c, 0xbc, 0x20, 0x70, 0x75, 0xc0
    }
};

static const unsigned char test_data[2][127] =
{
    {
        0x43, 0x72, 0x79, 0x70, 0x74, 0x6f, 0x67, 0x72,
        0x61, 0x70, 0x68, 0x69, 0x63, 0x20, 0x46, 0x6f,
        0x72, 0x75, 0x6d, 0x20, 0x52, 0x65, 0x73, 0x65,
        0x61, 0x72, 0x63, 0x68, 0x20, 0x47, 0x72, 0x6f,
        0x75, 0x70
    },
    {
        0x27, 0x54, 0x77, 0x61, 0x73, 0x20, 0x62, 0x72,
        0x69, 0x6c, 0x6c, 0x69, 0x67, 0x2c, 0x20, 0x61,
        0x6e, 0x64, 0x20, 0x74, 0x68, 0x65, 0x20, 0x73,
        0x6c, 0x69, 0x74, 0x68, 0x79, 0x20, 0x74, 0x6f,
        0x76, 0x65, 0x73, 0x0a, 0x44, 0x69, 0x64, 0x20,
        0x67, 0x79, 0x72, 0x65, 0x20, 0x61, 0x6e, 0x64,
        0x20, 0x67, 0x69, 0x6d, 0x62, 0x6c, 0x65, 0x20,
        0x69, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x77,
        0x61, 0x62, 0x65, 0x3a, 0x0a, 0x41, 0x6c, 0x6c,
        0x20, 0x6d, 0x69, 0x6d, 0x73, 0x79, 0x20, 0x77,
        0x65, 0x72, 0x65, 0x20, 0x74, 0x68, 0x65, 0x20,
        0x62, 0x6f, 0x72, 0x6f, 0x67, 0x6f, 0x76, 0x65,
        0x73, 0x2c, 0x0a, 0x41, 0x6e, 0x64, 0x20, 0x74,
        0x68, 0x65, 0x20, 0x6d, 0x6f, 0x6d, 0x65, 0x20,
        0x72, 0x61, 0x74, 0x68, 0x73, 0x20, 0x6f, 0x75,
        0x74, 0x67, 0x72, 0x61, 0x62, 0x65, 0x2e
    }
};

static const size_t test_data_len[2] =
{
    34U,
    127U
};

static const unsigned char test_mac[2][16] =
{
    {
        0xa8, 0x06, 0x1d, 0xc1, 0x30, 0x51, 0x36, 0xc6,
        0xc2, 0x2b, 0x8b, 0xaf, 0x0c, 0x01, 0x27, 0xa9
    },
    {
        0x45, 0x41, 0x66, 0x9a, 0x7e, 0xaa, 0xee, 0x61,
        0xe7, 0x08, 0xdc, 0x7c, 0xbc, 0xc5, 0xeb, 0x62
    }
};

int mbedtls_poly1305_self_test( int verbose )
{
    uint8_t mac[16];
    size_t i;
    int result;

    for ( i = 0U; i < 2U; i++ )
    {
        result = mbedtls_poly1305_mac( test_keys[i],
                                        test_data_len[i],
                                        test_data[i],
                                        mac );
        if ( result != 0 )
        {
            if ( verbose != 0 )
            {
                mbedtls_printf( "Poly1305 test %zi error code: %i\n", i, result );
            }

            return( -1 );
        }

        if ( memcmp( mac, test_mac[i], 16U ) != 0 )
        {
            if ( verbose != 0 )
            {
                mbedtls_printf( "Poly1305 test %zi failed\n", i );
            }

            return( -1 );
        }
    }

    return( 0 );
}

#endif /* MBEDTLS_SELF_TEST */

#endif /* MBEDTLS_POLY1305_C */