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Adapt ClientHello writing to case of single hardcoded ciphersuite

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This commit modifies the ClientHello writing routine ssl_write_client_hello
in ssl_cli.c to switch between
(a) listing all runtime configured ciphersuites
    (in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is not defined)
(b) listing just the single hardcoded ciphersuite
    (in case MBEDTLS_SSL_SINGLE_CIPHERSUITE is defined)

The approach taken is to introduce a pair of helper macros

  MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE( ssl, ver, info )
  MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE

which when delimiting a block of code lead to that block of
code being run once for each ciphersuite that's enabled in the
context `ssl` and version `ver`, referenced through the (fresh)
`info` variable. Internally, this is implemented either through
a plain `for` loop traversing the runtime configured ciphersuite
list (if MBEDTLS_SSL_SINGLE_CIPHERSUITE is disabled) or by just
hardcoding `info` to the single enabled ciphersuite (if
MBEDTLS_SSL_SINGLE_CIPHERSUITE is enabled).

These helper macros will prove useful whereever previous code
traversed the runtime configured ciphersuite list, but adaptations
of those occasions outside ClientHello writing are left for later
commits.
This commit is contained in:
Hanno Becker 2019-06-26 11:47:15 +01:00
parent 5cce936e62
commit 1499027d02
2 changed files with 95 additions and 35 deletions
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37
include/mbedtls/ssl_internal.h
View file

@ -1430,4 +1430,41 @@ static inline unsigned int mbedtls_ssl_conf_get_ems_enforced(
}
#endif /* MBEDTLS_SSL_EXTENDED_MASTER_SECRET */
/*
* Macros for the traversal of the list of all enabled ciphersuites.
* This is implemented as a plain loop in case we have a runtime
* configurable list of ciphersuites, and as a simple variable
* instantiation in case a single ciphersuite is enabled at
* compile-time.
*/
#if !defined(MBEDTLS_SSL_SINGLE_CIPHERSUITE)
#define MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE( ssl, ver, info ) \
{ \
int const *__id_ptr; \
for( __id_ptr=(ssl)->conf->ciphersuite_list[ (ver) ]; \
*__id_ptr != 0; __id_ptr++ ) \
{ \
const int __id = *__id_ptr; \
mbedtls_ssl_ciphersuite_handle_t info; \
info = mbedtls_ssl_ciphersuite_from_id( __id ); \
if( info == MBEDTLS_SSL_CIPHERSUITE_INVALID_HANDLE ) \
continue;
#define MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE \
} \
}
#else /* !MBEDTLS_SSL_SINGLE_CIPHERSUITE */
#define MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE( ssl, ver, info ) \
{ \
const mbedtls_ssl_ciphersuite_handle_t info = \
MBEDTLS_SSL_CIPHERSUITE_UNIQUE_VALID_HANDLE;
#define MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE \
}
#endif /* MBEDTLS_SSL_SINGLE_CIPHERSUITE */
#endif /* ssl_internal.h */

93
library/ssl_cli.c
View file

@ -831,8 +831,6 @@ static int ssl_write_client_hello( mbedtls_ssl_context *ssl )
unsigned char *buf;
unsigned char *p, *q;
unsigned char offer_compress;
const int *ciphersuites;
mbedtls_ssl_ciphersuite_handle_t ciphersuite_info;
#if defined(MBEDTLS_ECDH_C) || defined(MBEDTLS_ECDSA_C) || \
defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
int uses_ec = 0;
@ -972,21 +970,27 @@ static int ssl_write_client_hello( mbedtls_ssl_context *ssl )
/*
* Ciphersuite list
*/
ciphersuites = ssl->conf->ciphersuite_list[ssl->minor_ver];
/* Skip writing ciphersuite length for now */
n = 0;
q = p;
p += 2;
for( i = 0; ciphersuites[i] != 0; i++ )
MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE( ssl,
ssl->minor_ver,
ciphersuite_info )
{
ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( ciphersuites[i] );
if( ssl_validate_ciphersuite( ciphersuite_info, ssl,
ssl->conf->min_minor_ver,
ssl->conf->max_minor_ver ) != 0 )
continue;
{
/* Logically, we want to continue the ciphersuite iteration
* here, but We can't just use `continue` because
* MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE()
* doesn't unfold to a loop in case only a single
* ciphersuite is enabled. */
goto next_suite;
}
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, add ciphersuite: %04x",
mbedtls_ssl_suite_get_id( ciphersuite_info ) ) );
@ -1001,7 +1005,13 @@ static int ssl_write_client_hello( mbedtls_ssl_context *ssl )
mbedtls_ssl_suite_get_id( ciphersuite_info ) >> 8 );
*p++ = (unsigned char)(
mbedtls_ssl_suite_get_id( ciphersuite_info ) );
next_suite:
/* Need something here to avoid
* 'label at end of compound statement' error. */
((void) 0);
}
MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, got %d ciphersuites (excluding SCSVs)", n ) );
@ -1626,7 +1636,9 @@ static int ssl_parse_server_hello( mbedtls_ssl_context *ssl )
int extended_ms_seen = 0;
#endif
int handshake_failure = 0;
mbedtls_ssl_ciphersuite_handle_t suite_info;
/* The ciphersuite chosen by the server. */
mbedtls_ssl_ciphersuite_handle_t server_suite_info;
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse server hello" ) );
@ -1802,17 +1814,18 @@ static int ssl_parse_server_hello( mbedtls_ssl_context *ssl )
/*
* Initialize update checksum functions
*/
ssl->handshake->ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( i );
if( ssl->handshake->ciphersuite_info ==
MBEDTLS_SSL_CIPHERSUITE_INVALID_HANDLE )
server_suite_info = mbedtls_ssl_ciphersuite_from_id( i );
#if !defined(MBEDTLS_SSL_SINGLE_CIPHERSUITE)
ssl->handshake->ciphersuite_info = server_suite_info;
#endif
if( server_suite_info == MBEDTLS_SSL_CIPHERSUITE_INVALID_HANDLE )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "ciphersuite info for %04x not found", i ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_INTERNAL_ERROR );
return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
}
mbedtls_ssl_optimize_checksum( ssl, ssl->handshake->ciphersuite_info );
mbedtls_ssl_optimize_checksum( ssl, server_suite_info );
MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, session id len.: %d", n ) );
MBEDTLS_SSL_DEBUG_BUF( 3, "server hello, session id", buf + 35, n );
@ -1875,38 +1888,48 @@ static int ssl_parse_server_hello( mbedtls_ssl_context *ssl )
/*
* Perform cipher suite validation in same way as in ssl_write_client_hello.
*/
i = 0;
while( 1 )
MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE( ssl,
ssl->minor_ver,
ciphersuite_info )
{
if( ssl->conf->ciphersuite_list[ssl->minor_ver][i] == 0 )
if( ssl_validate_ciphersuite( ciphersuite_info, ssl,
ssl->conf->min_minor_ver,
ssl->conf->max_minor_ver ) != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad server hello message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
/* Logically, we want to continue the ciphersuite iteration
* here, but We can't just use `continue` because
* MBEDTLS_SSL_BEGIN_FOR_EACH_CIPHERSUITE()
* doesn't unfold to a loop in case only a single
* ciphersuite is enabled. */
goto next_suite;
}
if( ssl->conf->ciphersuite_list[ssl->minor_ver][i++] ==
ssl->session_negotiate->ciphersuite )
{
break;
}
}
if( ciphersuite_info != server_suite_info )
goto next_suite;
suite_info = mbedtls_ssl_ciphersuite_from_id( ssl->session_negotiate->ciphersuite );
if( ssl_validate_ciphersuite( suite_info, ssl, ssl->minor_ver, ssl->minor_ver ) != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad server hello message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
goto server_picked_valid_suite;
next_suite:
/* Need something here to avoid
* 'label at end of compound statement' error. */
((void) 0);
}
MBEDTLS_SSL_END_FOR_EACH_CIPHERSUITE
/* If we reach this code-path, the server's chosen ciphersuite
* wasn't among those advertised by us. */
MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad server hello message" ) );
mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER );
return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
server_picked_valid_suite:
MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, chosen ciphersuite: %s",
mbedtls_ssl_suite_get_name( suite_info ) ) );
mbedtls_ssl_suite_get_name( server_suite_info ) ) );
#if defined(MBEDTLS_SSL__ECP_RESTARTABLE)
if( mbedtls_ssl_suite_get_key_exchange( suite_info ) ==
if( mbedtls_ssl_suite_get_key_exchange( server_suite_info ) ==
MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA &&
ssl->minor_ver == MBEDTLS_SSL_MINOR_VERSION_3 )
{