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/*

 *  DTLS cookie callbacks implementation

 *

 *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved

 *  SPDX-License-Identifier: GPL-2.0

 *

 *  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.

 *

 *  This file is part of mbed TLS (https://tls.mbed.org)

 */

/*

 * These session callbacks use a simple chained list

 * to store and retrieve the session information.

 */

#if !defined(MBEDTLS_CONFIG_FILE)

#include "mbedtls/config.h"

#else

#include MBEDTLS_CONFIG_FILE

#endif

#if defined(MBEDTLS_SSL_COOKIE_C)

#if defined(MBEDTLS_PLATFORM_C)

#include "mbedtls/platform.h"

#else

#define mbedtls_calloc    calloc

#define mbedtls_free      free

#endif

#include "mbedtls/ssl_cookie.h"

#include "mbedtls/ssl_internal.h"

#include "mbedtls/platform_util.h"

#include 

/*

 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is

 * available. Try SHA-256 first, 512 wastes resources since we need to stay

 * with max 32 bytes of cookie for DTLS 1.0

 */

#if defined(MBEDTLS_SHA256_C)

#define COOKIE_MD           MBEDTLS_MD_SHA224

#define COOKIE_MD_OUTLEN    32

#define COOKIE_HMAC_LEN     28

#elif defined(MBEDTLS_SHA512_C)

#define COOKIE_MD           MBEDTLS_MD_SHA384

#define COOKIE_MD_OUTLEN    48

#define COOKIE_HMAC_LEN     28

#elif defined(MBEDTLS_SHA1_C)

#define COOKIE_MD           MBEDTLS_MD_SHA1

#define COOKIE_MD_OUTLEN    20

#define COOKIE_HMAC_LEN     20

#else

#error "DTLS hello verify needs SHA-1 or SHA-2"

#endif

/*

 * Cookies are formed of a 4-bytes timestamp (or serial number) and

 * an HMAC of timestemp and client ID.

 */

#define COOKIE_LEN      ( 4 + COOKIE_HMAC_LEN )

void mbedtls_ssl_cookie_init( mbedtls_ssl_cookie_ctx *ctx )

{

    mbedtls_md_init( &ctx->hmac_ctx );

#if !defined(MBEDTLS_HAVE_TIME)

    ctx->serial = 0;

#endif

    ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;

#if defined(MBEDTLS_THREADING_C)

    mbedtls_mutex_init( &ctx->mutex );

#endif

}

void mbedtls_ssl_cookie_set_timeout( mbedtls_ssl_cookie_ctx *ctx, unsigned long delay )

{

    ctx->timeout = delay;

}

void mbedtls_ssl_cookie_free( mbedtls_ssl_cookie_ctx *ctx )

{

    mbedtls_md_free( &ctx->hmac_ctx );

#if defined(MBEDTLS_THREADING_C)

    mbedtls_mutex_free( &ctx->mutex );

#endif

    mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_cookie_ctx ) );

}

int mbedtls_ssl_cookie_setup( mbedtls_ssl_cookie_ctx *ctx,

                      int (*f_rng)(void *, unsigned char *, size_t),

                      void *p_rng )

{

    int ret;

    unsigned char key[COOKIE_MD_OUTLEN];

    if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )

        return( ret );

    ret = mbedtls_md_setup( &ctx->hmac_ctx, mbedtls_md_info_from_type( COOKIE_MD ), 1 );

    if( ret != 0 )

        return( ret );

    ret = mbedtls_md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );

    if( ret != 0 )

        return( ret );

    mbedtls_platform_zeroize( key, sizeof( key ) );

    return( 0 );

}

/*

 * Generate the HMAC part of a cookie

 */

static int ssl_cookie_hmac( mbedtls_md_context_t *hmac_ctx,

                            const unsigned char time[4],

                            unsigned char **p, unsigned char *end,

                            const unsigned char *cli_id, size_t cli_id_len )

{

    unsigned char hmac_out[COOKIE_MD_OUTLEN];

    if( (size_t)( end - *p ) < COOKIE_HMAC_LEN )

        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );

    if( mbedtls_md_hmac_reset(  hmac_ctx ) != 0 ||

        mbedtls_md_hmac_update( hmac_ctx, time, 4 ) != 0 ||

        mbedtls_md_hmac_update( hmac_ctx, cli_id, cli_id_len ) != 0 ||

        mbedtls_md_hmac_finish( hmac_ctx, hmac_out ) != 0 )

    {

        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );

    }

    memcpy( *p, hmac_out, COOKIE_HMAC_LEN );

    *p += COOKIE_HMAC_LEN;

    return( 0 );

}

/*

 * Generate cookie for DTLS ClientHello verification

 */

int mbedtls_ssl_cookie_write( void *p_ctx,

                      unsigned char **p, unsigned char *end,

                      const unsigned char *cli_id, size_t cli_id_len )

{

    int ret;

    mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;

    unsigned long t;

    if( ctx == NULL || cli_id == NULL )

        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

    if( (size_t)( end - *p ) < COOKIE_LEN )

        return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );

#if defined(MBEDTLS_HAVE_TIME)

    t = (unsigned long) mbedtls_time( NULL );

#else

    t = ctx->serial++;

#endif

    (*p)[0] = (unsigned char)( t >> 24 );

    (*p)[1] = (unsigned char)( t >> 16 );

    (*p)[2] = (unsigned char)( t >>  8 );

    (*p)[3] = (unsigned char)( t       );

    *p += 4;

#if defined(MBEDTLS_THREADING_C)

    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )

        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );

#endif

    ret = ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4,

                           p, end, cli_id, cli_id_len );

#if defined(MBEDTLS_THREADING_C)

    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )

        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +

                MBEDTLS_ERR_THREADING_MUTEX_ERROR );

#endif

    return( ret );

}

/*

 * Check a cookie

 */

int mbedtls_ssl_cookie_check( void *p_ctx,

                      const unsigned char *cookie, size_t cookie_len,

                      const unsigned char *cli_id, size_t cli_id_len )

{

    unsigned char ref_hmac[COOKIE_HMAC_LEN];

    int ret = 0;

    unsigned char *p = ref_hmac;

    mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;

    unsigned long cur_time, cookie_time;

    if( ctx == NULL || cli_id == NULL )

        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

    if( cookie_len != COOKIE_LEN )

        return( -1 );

#if defined(MBEDTLS_THREADING_C)

    if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )

        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret );

#endif

    if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie,

                         &p, p + sizeof( ref_hmac ),

                         cli_id, cli_id_len ) != 0 )

        ret = -1;

#if defined(MBEDTLS_THREADING_C)

    if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )

        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR +

                MBEDTLS_ERR_THREADING_MUTEX_ERROR );

#endif

    if( ret != 0 )

        return( ret );

    if( mbedtls_ssl_safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 )

        return( -1 );

#if defined(MBEDTLS_HAVE_TIME)

    cur_time = (unsigned long) mbedtls_time( NULL );

#else

    cur_time = ctx->serial;

#endif

    cookie_time = ( (unsigned long) cookie[0] << 24 ) |

                  ( (unsigned long) cookie[1] << 16 ) |

                  ( (unsigned long) cookie[2] <<  8 ) |

                  ( (unsigned long) cookie[3]       );

    if( ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout )

        return( -1 );

    return( 0 );

}

#endif /* MBEDTLS_SSL_COOKIE_C */