library/ssl_ticket.c - security/mbedtls - Rivoreo Source Code Repositories

 /*
  *  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;
 }

 /*
  * 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( mbedtls_ssl_context *ssl, size_t *tlen )
 {
     int ret;
     unsigned char * const start = ssl->out_msg + 10;
     unsigned char *p = start;
     unsigned char *state;
     unsigned char iv[16];
     size_t clear_len, enc_len, pad_len, i;

     *tlen = 0;

     if( ssl->conf->ticket_keys == NULL )
         return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

     /* Write key name */
     memcpy( p, ssl->conf->ticket_keys->key_name, 16 );
     p += 16;

     /* Generate and write IV (with a copy for aes_crypt) */
     if( ( ret = ssl->conf->f_rng( ssl->conf->p_rng, p, 16 ) ) != 0 )
         return( ret );
     memcpy( iv, p, 16 );
     p += 16;

     /*
      * Dump session state
      *
      * After the session state itself, we still need room for 16 bytes of
      * padding and 32 bytes of MAC, so there's only so much room left
      */
     state = p + 2;
     if( ssl_save_session( ssl->session_negotiate, state,
                           MBEDTLS_SSL_MAX_CONTENT_LEN - ( state - ssl->out_msg ) - 48,
                           &clear_len ) != 0 )
     {
         return( MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE );
     }

     /* 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( &ssl->conf->ticket_keys->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 ),
                          ssl->conf->ticket_keys->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( mbedtls_ssl_context *ssl,
                              unsigned char *buf,
                              size_t len )
 {
     int ret;
     mbedtls_ssl_session session;
     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 || ssl->conf->ticket_keys == 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] ^ ssl->conf->ticket_keys->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 ),
                          ssl->conf->ticket_keys->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( &ssl->conf->ticket_keys->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 )
     {
         mbedtls_ssl_session_free( &session );
         return( ret );
     }

 #if defined(MBEDTLS_HAVE_TIME)
     /* Check if still valid */
     if( (int) ( time( NULL) - session.start ) > ssl->conf->ticket_lifetime )
     {
         mbedtls_ssl_session_free( &session );
         return( MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED );
     }
 #endif

     /*
      * Keep the session ID sent by the client, since we MUST send it back to
      * inform him we're accepting the ticket  (RFC 5077 section 3.4)
      */
     session.length = ssl->session_negotiate->length;
     memcpy( &session.id, ssl->session_negotiate->id, session.length );

     mbedtls_ssl_session_free( ssl->session_negotiate );
     memcpy( ssl->session_negotiate, &session, sizeof( mbedtls_ssl_session ) );

     /* Zeroize instead of free as we copied the content */
     mbedtls_zeroize( &session, sizeof( mbedtls_ssl_session ) );

     return( 0 );
 }

 #endif /* MBEDTLS_SSL_TICKET_C */
	/*
	* 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;
	}

	/*
	* 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( mbedtls_ssl_context ssl, size_t tlen )
	{
	int ret;
	unsigned char * const start = ssl->out_msg + 10;
	unsigned char *p = start;
	unsigned char *state;
	unsigned char iv[16];
	size_t clear_len, enc_len, pad_len, i;

	*tlen = 0;

	if( ssl->conf->ticket_keys == NULL )
	return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );

	/* Write key name */
	memcpy( p, ssl->conf->ticket_keys->key_name, 16 );
	p += 16;

	/* Generate and write IV (with a copy for aes_crypt) */
	if( ( ret = ssl->conf->f_rng( ssl->conf->p_rng, p, 16 ) ) != 0 )
	return( ret );
	memcpy( iv, p, 16 );
	p += 16;

	/*
	* Dump session state
	*
	* After the session state itself, we still need room for 16 bytes of
	* padding and 32 bytes of MAC, so there's only so much room left
	*/
	state = p + 2;
	if( ssl_save_session( ssl->session_negotiate, state,
	MBEDTLS_SSL_MAX_CONTENT_LEN - ( state - ssl->out_msg ) - 48,
	&clear_len ) != 0 )
	{
	return( MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE );
	}

	/* 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( &ssl->conf->ticket_keys->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 ),
	ssl->conf->ticket_keys->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( mbedtls_ssl_context *ssl,
	unsigned char *buf,
	size_t len )
	{
	int ret;
	mbedtls_ssl_session session;
	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 \|\| ssl->conf->ticket_keys == 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] ^ ssl->conf->ticket_keys->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 ),
	ssl->conf->ticket_keys->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( &ssl->conf->ticket_keys->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 )
	{
	mbedtls_ssl_session_free( &session );
	return( ret );
	}

	#if defined(MBEDTLS_HAVE_TIME)
	/* Check if still valid */
	if( (int) ( time( NULL) - session.start ) > ssl->conf->ticket_lifetime )
	{
	mbedtls_ssl_session_free( &session );
	return( MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED );
	}
	#endif

	/*
	* Keep the session ID sent by the client, since we MUST send it back to
	* inform him we're accepting the ticket (RFC 5077 section 3.4)
	*/
	session.length = ssl->session_negotiate->length;
	memcpy( &session.id, ssl->session_negotiate->id, session.length );

	mbedtls_ssl_session_free( ssl->session_negotiate );
	memcpy( ssl->session_negotiate, &session, sizeof( mbedtls_ssl_session ) );

	/* Zeroize instead of free as we copied the content */
	mbedtls_zeroize( &session, sizeof( mbedtls_ssl_session ) );

	return( 0 );
	}

	#endif /* MBEDTLS_SSL_TICKET_C */