/* * DTLS cookie callbacks implementation * * Copyright (C) 2014, Brainspark B.V. * * This file is part of PolarSSL (http://www.polarssl.org) * Lead Maintainer: Paul Bakker * * 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. */ /* * These session callbacks use a simple chained list * to store and retrieve the session information. */ #if !defined(POLARSSL_CONFIG_FILE) #include "polarssl/config.h" #else #include POLARSSL_CONFIG_FILE #endif #if defined(POLARSSL_SSL_COOKIE_C) #include "polarssl/ssl_cookie.h" #if defined(POLARSSL_PLATFORM_C) #include "polarssl/platform.h" #else #define polarssl_malloc malloc #define polarssl_free free #endif /* Implementation that should never be optimized out by the compiler */ static void polarssl_zeroize( void *v, size_t n ) { volatile unsigned char *p = v; while( n-- ) *p++ = 0; } /* * 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(POLARSSL_SHA256_C) #define COOKIE_MD POLARSSL_MD_SHA224 #define COOKIE_MD_OUTLEN 32 #define COOKIE_HMAC_LEN 28 #elif defined(POLARSSL_SHA512_C) #define COOKIE_MD POLARSSL_MD_SHA384 #define COOKIE_MD_OUTLEN 48 #define COOKIE_HMAC_LEN 28 #elif defined(POLARSSL_SHA1_C) #define COOKIE_MD POLARSSL_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 ) #define COOKIE_TIMEOUT 60 void ssl_cookie_init( ssl_cookie_ctx *ctx ) { md_init( &ctx->hmac_ctx ); #if !defined(POLARSSL_HAVE_TIME) ctx->serial = 0; #endif } void ssl_cookie_free( ssl_cookie_ctx *ctx ) { md_free( &ctx->hmac_ctx ); } int ssl_cookie_setup( 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 = md_init_ctx( &ctx->hmac_ctx, md_info_from_type( COOKIE_MD ) ); if( ret != 0 ) return( ret ); ret = md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) ); if( ret != 0 ) return( ret ); polarssl_zeroize( key, sizeof( key ) ); return( 0 ); } /* * Generate the HMAC part of a cookie */ static int ssl_cookie_hmac( 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 ) { int ret; unsigned char hmac_out[COOKIE_MD_OUTLEN]; if( (size_t)( end - *p ) < COOKIE_HMAC_LEN ) return( POLARSSL_ERR_SSL_BAD_INPUT_DATA ); if( ( ret = md_hmac_reset( hmac_ctx ) ) != 0 || ( ret = md_hmac_update( hmac_ctx, time, 4 ) ) != 0 || ( ret = md_hmac_update( hmac_ctx, cli_id, cli_id_len ) ) != 0 || ( ret = md_hmac_finish( hmac_ctx, hmac_out ) ) != 0 ) { return( POLARSSL_ERR_SSL_INTERNAL_ERROR ); } memcpy( *p, hmac_out, COOKIE_HMAC_LEN ); *p += COOKIE_HMAC_LEN; return( 0 ); } /* * Generate cookie for DTLS ClientHello verification */ int ssl_cookie_write( void *p_ctx, unsigned char **p, unsigned char *end, const unsigned char *cli_id, size_t cli_id_len ) { ssl_cookie_ctx *ctx = (ssl_cookie_ctx *) p_ctx; unsigned long t; if( ctx == NULL || cli_id == NULL ) return( POLARSSL_ERR_SSL_BAD_INPUT_DATA ); if( (size_t)( end - *p ) < COOKIE_LEN ) return( POLARSSL_ERR_SSL_BAD_INPUT_DATA ); #if defined(POLARSSL_HAVE_TIME) t = (unsigned long) 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; return( ssl_cookie_hmac( &ctx->hmac_ctx, *p - 4, p, end, cli_id, cli_id_len ) ); } /* * Check a cookie */ int 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]; unsigned char *p = ref_hmac; ssl_cookie_ctx *ctx = (ssl_cookie_ctx *) p_ctx; unsigned long cur_time, cookie_time; if( ctx == NULL || cli_id == NULL ) return( POLARSSL_ERR_SSL_BAD_INPUT_DATA ); if( cookie_len != COOKIE_LEN ) return( -1 ); if( ssl_cookie_hmac( &ctx->hmac_ctx, cookie, &p, p + sizeof( ref_hmac ), cli_id, cli_id_len ) != 0 ) return( -1 ); if( safer_memcmp( cookie + 4, ref_hmac, sizeof( ref_hmac ) ) != 0 ) return( -1 ); #if defined(POLARSSL_HAVE_TIME) cur_time = (unsigned long) 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( cur_time - cookie_time > COOKIE_TIMEOUT ) return( -1 ); return( 0 ); } #endif /* POLARSSL_SSL_COOKIE_C */