/* * DTLS cookie callbacks implementation * * Copyright (C) 2006-2015, 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) */ /* * 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 <string.h> /* * 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 */