| /* |
| * TLS server tickets callbacks implementation |
| * |
| * Copyright (C) 2015, ARM Limited, All Rights Reserved |
| * |
| * This file is part of mbed TLS (https://tls.mbed.org) |
| * |
| * 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. |
| */ |
| |
| #if !defined(MBEDTLS_CONFIG_FILE) |
| #include "mbedtls/config.h" |
| #else |
| #include MBEDTLS_CONFIG_FILE |
| #endif |
| |
| #if defined(MBEDTLS_SSL_TICKET_C) |
| |
| #include "mbedtls/ssl_ticket.h" |
| |
| #if defined(MBEDTLS_PLATFORM_C) |
| #include "mbedtls/platform.h" |
| #else |
| #define mbedtls_malloc malloc |
| #define mbedtls_free free |
| #endif |
| |
| #include <string.h> |
| |
| /* 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; |
| } |
| |
| /* |
| * Initialze context |
| */ |
| void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx ) |
| { |
| memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) ); |
| } |
| |
| /* |
| * Setup context for actual use |
| */ |
| int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx, |
| int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, |
| uint32_t lifetime ) |
| { |
| int ret; |
| unsigned char buf[16]; |
| |
| ctx->f_rng = f_rng; |
| ctx->p_rng = p_rng; |
| |
| ctx->ticket_lifetime = lifetime; |
| |
| mbedtls_aes_init( &ctx->enc ); |
| mbedtls_aes_init( &ctx->dec ); |
| |
| if( ( ret = f_rng( p_rng, ctx->key_name, 16 ) != 0 ) || |
| ( ret = f_rng( p_rng, ctx->mac_key, 16 ) != 0 ) || |
| ( ret = f_rng( p_rng, buf, 16 ) != 0 ) ) |
| { |
| return( ret ); |
| } |
| |
| if( ( ret = mbedtls_aes_setkey_enc( &ctx->enc, buf, 128 ) ) != 0 || |
| ( ret = mbedtls_aes_setkey_dec( &ctx->dec, buf, 128 ) ) != 0 ) |
| { |
| mbedtls_ssl_ticket_free( ctx ); |
| return( ret ); |
| } |
| |
| mbedtls_zeroize( buf, sizeof( buf ) ); |
| |
| return( 0 ); |
| } |
| |
| /* |
| * Serialize a session in the following format: |
| * 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session) |
| * n . n+2 peer_cert length = m (0 if no certificate) |
| * n+3 . n+2+m peer cert ASN.1 |
| * |
| * Assumes ticket is NULL (always true on server side). |
| */ |
| static int ssl_save_session( const mbedtls_ssl_session *session, |
| unsigned char *buf, size_t buf_len, |
| size_t *olen ) |
| { |
| unsigned char *p = buf; |
| size_t left = buf_len; |
| #if defined(MBEDTLS_X509_CRT_PARSE_C) |
| size_t cert_len; |
| #endif /* MBEDTLS_X509_CRT_PARSE_C */ |
| |
| if( left < sizeof( mbedtls_ssl_session ) ) |
| return( -1 ); |
| |
| memcpy( p, session, sizeof( mbedtls_ssl_session ) ); |
| p += sizeof( mbedtls_ssl_session ); |
| left -= sizeof( mbedtls_ssl_session ); |
| |
| #if defined(MBEDTLS_X509_CRT_PARSE_C) |
| if( session->peer_cert == NULL ) |
| cert_len = 0; |
| else |
| cert_len = session->peer_cert->raw.len; |
| |
| if( left < 3 + cert_len ) |
| return( -1 ); |
| |
| *p++ = (unsigned char)( cert_len >> 16 & 0xFF ); |
| *p++ = (unsigned char)( cert_len >> 8 & 0xFF ); |
| *p++ = (unsigned char)( cert_len & 0xFF ); |
| |
| if( session->peer_cert != NULL ) |
| memcpy( p, session->peer_cert->raw.p, cert_len ); |
| |
| p += cert_len; |
| #endif /* MBEDTLS_X509_CRT_PARSE_C */ |
| |
| *olen = p - buf; |
| |
| return( 0 ); |
| } |
| |
| /* |
| * Unserialise session, see ssl_save_session() |
| */ |
| static int ssl_load_session( mbedtls_ssl_session *session, |
| const unsigned char *buf, size_t len ) |
| { |
| const unsigned char *p = buf; |
| const unsigned char * const end = buf + len; |
| #if defined(MBEDTLS_X509_CRT_PARSE_C) |
| size_t cert_len; |
| #endif /* MBEDTLS_X509_CRT_PARSE_C */ |
| |
| if( p + sizeof( mbedtls_ssl_session ) > end ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| memcpy( session, p, sizeof( mbedtls_ssl_session ) ); |
| p += sizeof( mbedtls_ssl_session ); |
| |
| #if defined(MBEDTLS_X509_CRT_PARSE_C) |
| if( p + 3 > end ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2]; |
| p += 3; |
| |
| if( cert_len == 0 ) |
| { |
| session->peer_cert = NULL; |
| } |
| else |
| { |
| int ret; |
| |
| if( p + cert_len > end ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| session->peer_cert = mbedtls_malloc( sizeof( mbedtls_x509_crt ) ); |
| |
| if( session->peer_cert == NULL ) |
| return( MBEDTLS_ERR_SSL_MALLOC_FAILED ); |
| |
| mbedtls_x509_crt_init( session->peer_cert ); |
| |
| if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert, |
| p, cert_len ) ) != 0 ) |
| { |
| mbedtls_x509_crt_free( session->peer_cert ); |
| mbedtls_free( session->peer_cert ); |
| session->peer_cert = NULL; |
| return( ret ); |
| } |
| |
| p += cert_len; |
| } |
| #endif /* MBEDTLS_X509_CRT_PARSE_C */ |
| |
| if( p != end ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| return( 0 ); |
| } |
| |
| /* |
| * Create session ticket, secured as recommended in RFC 5077 section 4: |
| * |
| * struct { |
| * opaque key_name[16]; |
| * opaque iv[16]; |
| * opaque encrypted_state<0..2^16-1>; |
| * opaque mac[32]; |
| * } ticket; |
| * |
| * (the internal state structure differs, however). |
| */ |
| int mbedtls_ssl_ticket_write( void *p_ticket, |
| const mbedtls_ssl_session *session, |
| unsigned char *start, |
| const unsigned char *end, |
| size_t *tlen, |
| uint32_t *ticket_lifetime ) |
| { |
| int ret; |
| mbedtls_ssl_ticket_context *ctx = p_ticket; |
| unsigned char *p = start; |
| unsigned char *state; |
| unsigned char iv[16]; |
| size_t clear_len, enc_len, pad_len, i; |
| |
| *tlen = 0; |
| |
| if( ctx == NULL ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| *ticket_lifetime = ctx->ticket_lifetime; |
| |
| /* We need at least 16 bytes for key_name, 16 for IV, 2 for len |
| * 16 for padding, 32 for MAC, in addition to session itself, |
| * that will be checked when writing it. */ |
| if( end - start < 16 + 16 + 2 + 16 + 32 ) |
| return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); |
| |
| /* Write key name */ |
| memcpy( p, ctx->key_name, 16 ); |
| p += 16; |
| |
| /* Generate and write IV (with a copy for aes_crypt) */ |
| if( ( ret = ctx->f_rng( ctx->p_rng, p, 16 ) ) != 0 ) |
| return( ret ); |
| memcpy( iv, p, 16 ); |
| p += 16; |
| |
| /* Dump session state */ |
| state = p + 2; |
| if( ssl_save_session( session, state, end - state, &clear_len ) != 0 ) |
| return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL ); |
| |
| /* Apply PKCS padding */ |
| pad_len = 16 - clear_len % 16; |
| enc_len = clear_len + pad_len; |
| for( i = clear_len; i < enc_len; i++ ) |
| state[i] = (unsigned char) pad_len; |
| |
| /* Encrypt */ |
| if( ( ret = mbedtls_aes_crypt_cbc( &ctx->enc, MBEDTLS_AES_ENCRYPT, |
| enc_len, iv, state, state ) ) != 0 ) |
| { |
| return( ret ); |
| } |
| |
| /* Write length */ |
| *p++ = (unsigned char)( ( enc_len >> 8 ) & 0xFF ); |
| *p++ = (unsigned char)( ( enc_len ) & 0xFF ); |
| p = state + enc_len; |
| |
| /* Compute and write MAC( key_name + iv + enc_state_len + enc_state ) */ |
| if( ( ret = mbedtls_md_hmac( mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), |
| ctx->mac_key, 16, |
| start, p - start, p ) ) != 0 ) |
| { |
| return( ret ); |
| } |
| p += 32; |
| |
| *tlen = p - start; |
| |
| return( 0 ); |
| } |
| |
| /* |
| * Load session ticket (see mbedtls_ssl_ticket_write for structure) |
| */ |
| int mbedtls_ssl_ticket_parse( void *p_ticket, |
| mbedtls_ssl_session *session, |
| unsigned char *buf, |
| size_t len ) |
| { |
| int ret; |
| mbedtls_ssl_ticket_context *ctx = p_ticket; |
| unsigned char *key_name = buf; |
| unsigned char *iv = buf + 16; |
| unsigned char *enc_len_p = iv + 16; |
| unsigned char *ticket = enc_len_p + 2; |
| unsigned char *mac; |
| unsigned char computed_mac[32]; |
| size_t enc_len, clear_len, i; |
| unsigned char pad_len, diff; |
| |
| if( len < 34 || ctx == NULL ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1]; |
| mac = ticket + enc_len; |
| |
| if( len != enc_len + 66 ) |
| return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA ); |
| |
| /* Check name, in constant time though it's not a big secret */ |
| diff = 0; |
| for( i = 0; i < 16; i++ ) |
| diff |= key_name[i] ^ ctx->key_name[i]; |
| /* don't return yet, check the MAC anyway */ |
| |
| /* Check mac, with constant-time buffer comparison */ |
| if( ( ret = mbedtls_md_hmac( mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), |
| ctx->mac_key, 16, |
| buf, len - 32, computed_mac ) ) != 0 ) |
| { |
| return( ret ); |
| } |
| |
| for( i = 0; i < 32; i++ ) |
| diff |= mac[i] ^ computed_mac[i]; |
| |
| /* Now return if ticket is not authentic, since we want to avoid |
| * decrypting arbitrary attacker-chosen data */ |
| if( diff != 0 ) |
| return( MBEDTLS_ERR_SSL_INVALID_MAC ); |
| |
| /* Decrypt */ |
| if( ( ret = mbedtls_aes_crypt_cbc( &ctx->dec, MBEDTLS_AES_DECRYPT, |
| enc_len, iv, ticket, ticket ) ) != 0 ) |
| { |
| return( ret ); |
| } |
| |
| /* Check PKCS padding */ |
| pad_len = ticket[enc_len - 1]; |
| |
| ret = 0; |
| for( i = 2; i < pad_len; i++ ) |
| if( ticket[enc_len - i] != pad_len ) |
| ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA; |
| if( ret != 0 ) |
| return( ret ); |
| |
| clear_len = enc_len - pad_len; |
| |
| /* Actually load session */ |
| if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 ) |
| return( ret ); |
| |
| #if defined(MBEDTLS_HAVE_TIME) |
| /* Check if still valid */ |
| if( ( time( NULL) - session->start ) > ctx->ticket_lifetime ) |
| return( MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED ); |
| #endif |
| |
| return( 0 ); |
| } |
| |
| /* |
| * Free context |
| */ |
| void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx ) |
| { |
| mbedtls_aes_free( &ctx->enc ); |
| mbedtls_aes_free( &ctx->dec ); |
| |
| mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) ); |
| } |
| |
| #endif /* MBEDTLS_SSL_TICKET_C */ |