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Add negotiation of Extended Master Secret

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(But not the actual thing yet.)
This commit is contained in:
Manuel Pégourié-Gonnard 2014-10-20 18:40:56 +02:00
parent 178f9d6e19
commit 367381fddd
8 changed files with 264 additions and 0 deletions
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14
include/polarssl/config.h
View file

@ -811,6 +811,20 @@
*/
//#define POLARSSL_SSL_DEBUG_ALL
/** \def POLARSSL_SSL_EXTENDED_MASTER_SECRET
*
* Enable support for Extended Master Secret, aka Session Hash
* (draft-ietf-tls-session-hash-02).
*
* This was introduced as "the proper fix" to the Triple Handshake familiy of
* attacks, but it is recommended to always use it (even if you disable
* renegotiation), since it actually fixes a more fundamental issue in the
* original SSL/TLS design, and has implications beyond Triple Handshake.
*
* Comment this macro to disable support for Extended Master Secret.
*/
#define POLARSSL_SSL_EXTENDED_MASTER_SECRET
/**
* \def POLARSSL_SSL_FALLBACK_SCSV
*

26
include/polarssl/ssl.h
View file

@ -209,6 +209,9 @@
#define SSL_IS_NOT_FALLBACK 0
#define SSL_IS_FALLBACK 1
#define SSL_EXTENDED_MS_DISABLED 0
#define SSL_EXTENDED_MS_ENABLED 1
#define SSL_COMPRESS_NULL 0
#define SSL_COMPRESS_DEFLATE 1
@ -406,6 +409,8 @@
#define TLS_EXT_ALPN 16
#define TLS_EXT_EXTENDED_MASTER_SECRET 0x0017 /* 23 */
#define TLS_EXT_SESSION_TICKET 35
#define TLS_EXT_RENEGOTIATION_INFO 0xFF01
@ -657,6 +662,9 @@ struct _ssl_handshake_params
#if defined(POLARSSL_SSL_SESSION_TICKETS)
int new_session_ticket; /*!< use NewSessionTicket? */
#endif /* POLARSSL_SSL_SESSION_TICKETS */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
int extended_ms; /*!< use Extended Master Secret? */
#endif
};
#if defined(POLARSSL_SSL_SESSION_TICKETS)
@ -705,6 +713,9 @@ struct _ssl_context
#if defined(POLARSSL_SSL_FALLBACK_SCSV) && defined(POLARSSL_SSL_CLI_C)
char fallback; /*!< flag for fallback connections */
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
char extended_ms; /*!< flag for extended master secret */
#endif
/*
* Callbacks (RNG, debug, I/O, verification)
@ -1414,6 +1425,21 @@ void ssl_set_min_version( ssl_context *ssl, int major, int minor );
void ssl_set_fallback( ssl_context *ssl, char fallback );
#endif /* POLARSSL_SSL_FALLBACK_SCSV && POLARSSL_SSL_CLI_C */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
/**
* \brief Enable or disable Extended Master Secret negotiation.
* (Default: SSL_EXTENDED_MS_ENABLED)
*
* \note This should always be enabled, it is a security fix to the
* protocol, and should not cause any interoperability issue
* (used only if the peer supports it too).
*
* \param ssl SSL context
* \param ems SSL_EXTENDED_MS_ENABLED or SSL_EXTENDED_MS_DISABLED
*/
void ssl_set_extended_master_secret( ssl_context *ssl, char ems );
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_MAX_FRAGMENT_LENGTH)
/**
* \brief Set the maximum fragment length to emit and/or negotiate

62
library/ssl_cli.c
View file

@ -359,6 +359,31 @@ static void ssl_write_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static void ssl_write_extended_ms_ext( ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
if( ssl->extended_ms == SSL_EXTENDED_MS_DISABLED )
{
*olen = 0;
return;
}
SSL_DEBUG_MSG( 3, ( "client hello, adding extended_master_secret "
"extension" ) );
*p++ = (unsigned char)( ( TLS_EXT_EXTENDED_MASTER_SECRET >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( TLS_EXT_EXTENDED_MASTER_SECRET ) & 0xFF );
*p++ = 0x00;
*p++ = 0x00;
*olen = 4;
}
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_SESSION_TICKETS)
static void ssl_write_session_ticket_ext( ssl_context *ssl,
unsigned char *buf, size_t *olen )
@ -662,6 +687,11 @@ static int ssl_write_client_hello( ssl_context *ssl )
ext_len += olen;
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
ssl_write_extended_ms_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;
#endif
#if defined(POLARSSL_SSL_SESSION_TICKETS)
ssl_write_session_ticket_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;
@ -780,6 +810,25 @@ static int ssl_parse_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static int ssl_parse_extended_ms_ext( ssl_context *ssl,
const unsigned char *buf,
size_t len )
{
if( ssl->extended_ms == SSL_EXTENDED_MS_DISABLED ||
len != 0 )
{
return( POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO );
}
((void) buf);
ssl->handshake->extended_ms = SSL_EXTENDED_MS_ENABLED;
return( 0 );
}
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_SESSION_TICKETS)
static int ssl_parse_session_ticket_ext( ssl_context *ssl,
const unsigned char *buf,
@ -1152,6 +1201,19 @@ static int ssl_parse_server_hello( ssl_context *ssl )
break;
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
case TLS_EXT_EXTENDED_MASTER_SECRET:
SSL_DEBUG_MSG( 3, ( "found extended_master_secret extension" ) );
if( ( ret = ssl_parse_extended_ms_ext( ssl,
ext + 4, ext_size ) ) != 0 )
{
return( ret );
}
break;
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_SESSION_TICKETS)
case TLS_EXT_SESSION_TICKET:
SSL_DEBUG_MSG( 3, ( "found session_ticket extension" ) );

61
library/ssl_srv.c
View file

@ -635,6 +635,26 @@ static int ssl_parse_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static int ssl_parse_extended_ms_ext( ssl_context *ssl,
const unsigned char *buf,
size_t len )
{
if( len != 0 )
{
SSL_DEBUG_MSG( 1, ( "bad client hello message" ) );
return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
}
((void) buf);
if( ssl->extended_ms == SSL_EXTENDED_MS_ENABLED )
ssl->handshake->extended_ms = SSL_EXTENDED_MS_ENABLED;
return( 0 );
}
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_SESSION_TICKETS)
static int ssl_parse_session_ticket_ext( ssl_context *ssl,
unsigned char *buf,
@ -1500,6 +1520,16 @@ static int ssl_parse_client_hello( ssl_context *ssl )
break;
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
case TLS_EXT_EXTENDED_MASTER_SECRET:
SSL_DEBUG_MSG( 3, ( "found extended master secret extension" ) );
ret = ssl_parse_extended_ms_ext( ssl, ext + 4, ext_size );
if( ret != 0 )
return( ret );
break;
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_SESSION_TICKETS)
case TLS_EXT_SESSION_TICKET:
SSL_DEBUG_MSG( 3, ( "found session ticket extension" ) );
@ -1649,6 +1679,32 @@ static void ssl_write_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static void ssl_write_extended_ms_ext( ssl_context *ssl,
unsigned char *buf,
size_t *olen )
{
unsigned char *p = buf;
if( ssl->handshake->extended_ms == SSL_EXTENDED_MS_DISABLED )
{
*olen = 0;
return;
}
SSL_DEBUG_MSG( 3, ( "server hello, adding extended master secret "
"extension" ) );
*p++ = (unsigned char)( ( TLS_EXT_EXTENDED_MASTER_SECRET >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( TLS_EXT_EXTENDED_MASTER_SECRET ) & 0xFF );
*p++ = 0x00;
*p++ = 0x00;
*olen = 4;
}
#endif /* POLARSSL_SSL_EXTENDED_MASTER_SECRET */
#if defined(POLARSSL_SSL_SESSION_TICKETS)
static void ssl_write_session_ticket_ext( ssl_context *ssl,
unsigned char *buf,
@ -1952,6 +2008,11 @@ static int ssl_write_server_hello( ssl_context *ssl )
ext_len += olen;
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
ssl_write_extended_ms_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;
#endif
#if defined(POLARSSL_SSL_SESSION_TICKETS)
ssl_write_session_ticket_ext( ssl, p + 2 + ext_len, &olen );
ext_len += olen;

16
library/ssl_tls.c
View file

@ -470,6 +470,11 @@ int ssl_derive_keys( ssl_context *ssl )
SSL_DEBUG_BUF( 3, "premaster secret", handshake->premaster,
handshake->pmslen );
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
if( ssl->handshake->extended_ms == SSL_EXTENDED_MS_ENABLED )
SSL_DEBUG_MSG( 3, ( "using extended master secret" ) );
// XXX to be continued, WIP
#endif
handshake->tls_prf( handshake->premaster, handshake->pmslen,
"master secret",
handshake->randbytes, 64, session->master, 48 );
@ -3437,6 +3442,10 @@ int ssl_init( ssl_context *ssl )
memset( ssl-> in_ctr, 0, SSL_BUFFER_LEN );
memset( ssl->out_ctr, 0, SSL_BUFFER_LEN );
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
ssl->extended_ms = SSL_EXTENDED_MS_ENABLED;
#endif
#if defined(POLARSSL_SSL_SESSION_TICKETS)
ssl->ticket_lifetime = SSL_DEFAULT_TICKET_LIFETIME;
#endif
@ -3984,6 +3993,13 @@ void ssl_set_fallback( ssl_context *ssl, char fallback )
}
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
void ssl_set_extended_master_secret( ssl_context *ssl, char ems )
{
ssl->extended_ms = ems;
}
#endif
#if defined(POLARSSL_SSL_MAX_FRAGMENT_LENGTH)
int ssl_set_max_frag_len( ssl_context *ssl, unsigned char mfl_code )
{

25
programs/ssl/ssl_client2.c
View file

@ -96,6 +96,7 @@ int main( int argc, char *argv[] )
#define DFL_TICKETS SSL_SESSION_TICKETS_ENABLED
#define DFL_ALPN_STRING NULL
#define DFL_FALLBACK -1
#define DFL_EXTENDED_MS -1
#define GET_REQUEST "GET %s HTTP/1.0\r\nExtra-header: "
#define GET_REQUEST_END "\r\n\r\n"
@ -134,6 +135,7 @@ struct options
int tickets; /* enable / disable session tickets */
const char *alpn_string; /* ALPN supported protocols */
int fallback; /* is this a fallback connection? */
char extended_ms; /* negotiate extended master secret? */
} opt;
static void my_debug( void *ctx, int level, const char *str )
@ -293,6 +295,13 @@ static int my_verify( void *data, x509_crt *crt, int depth, int *flags )
#define USAGE_FALLBACK ""
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
#define USAGE_EMS \
" extended_ms=0/1 default: (library default: on)\n"
#else
#define USAGE_EMS ""
#endif
#define USAGE \
"\n usage: ssl_client2 param=<>...\n" \
"\n acceptable parameters:\n" \
@ -323,6 +332,7 @@ static int my_verify( void *data, x509_crt *crt, int depth, int *flags )
USAGE_TRUNC_HMAC \
USAGE_ALPN \
USAGE_FALLBACK \
USAGE_EMS \
"\n" \
" min_version=%%s default: \"\" (ssl3)\n" \
" max_version=%%s default: \"\" (tls1_2)\n" \
@ -424,6 +434,7 @@ int main( int argc, char *argv[] )
opt.tickets = DFL_TICKETS;
opt.alpn_string = DFL_ALPN_STRING;
opt.fallback = DFL_FALLBACK;
opt.extended_ms = DFL_EXTENDED_MS;
for( i = 1; i < argc; i++ )
{
@ -539,6 +550,15 @@ int main( int argc, char *argv[] )
default: goto usage;
}
}
else if( strcmp( p, "extended_ms" ) == 0 )
{
switch( atoi( q ) )
{
case 0: opt.extended_ms = SSL_EXTENDED_MS_DISABLED; break;
case 1: opt.extended_ms = SSL_EXTENDED_MS_ENABLED; break;
default: goto usage;
}
}
else if( strcmp( p, "min_version" ) == 0 )
{
if( strcmp( q, "ssl3" ) == 0 )
@ -902,6 +922,11 @@ int main( int argc, char *argv[] )
}
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
if( opt.extended_ms != DFL_EXTENDED_MS )
ssl_set_extended_master_secret( &ssl, opt.extended_ms );
#endif
#if defined(POLARSSL_SSL_ALPN)
if( opt.alpn_string != NULL )
if( ( ret = ssl_set_alpn_protocols( &ssl, alpn_list ) ) != 0 )

25
programs/ssl/ssl_server2.c
View file

@ -116,6 +116,7 @@ int main( int argc, char *argv[] )
#define DFL_SNI NULL
#define DFL_ALPN_STRING NULL
#define DFL_DHM_FILE NULL
#define DFL_EXTENDED_MS -1
#define LONG_RESPONSE "<p>01-blah-blah-blah-blah-blah-blah-blah-blah-blah\r\n" \
"02-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah-blah\r\n" \
@ -176,6 +177,7 @@ struct options
char *sni; /* string describing sni information */
const char *alpn_string; /* ALPN supported protocols */
const char *dhm_file; /* the file with the DH parameters */
char extended_ms; /* allow negotiation of extended MS? */
} opt;
static void my_debug( void *ctx, int level, const char *str )
@ -299,6 +301,13 @@ static int my_send( void *ctx, const unsigned char *buf, size_t len )
#define USAGE_ALPN ""
#endif /* POLARSSL_SSL_ALPN */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
#define USAGE_EMS \
" extended_ms=0/1 default: (library default: on)\n"
#else
#define USAGE_EMS ""
#endif
#define USAGE \
"\n usage: ssl_server2 param=<>...\n" \
"\n acceptable parameters:\n" \
@ -324,6 +333,7 @@ static int my_send( void *ctx, const unsigned char *buf, size_t len )
USAGE_CACHE \
USAGE_MAX_FRAG_LEN \
USAGE_ALPN \
USAGE_EMS \
"\n" \
" min_version=%%s default: \"ssl3\"\n" \
" max_version=%%s default: \"tls1_2\"\n" \
@ -713,6 +723,7 @@ int main( int argc, char *argv[] )
opt.sni = DFL_SNI;
opt.alpn_string = DFL_ALPN_STRING;
opt.dhm_file = DFL_DHM_FILE;
opt.extended_ms = DFL_EXTENDED_MS;
for( i = 1; i < argc; i++ )
{
@ -880,6 +891,15 @@ int main( int argc, char *argv[] )
{
opt.alpn_string = q;
}
else if( strcmp( p, "extended_ms" ) == 0 )
{
switch( atoi( q ) )
{
case 0: opt.extended_ms = SSL_EXTENDED_MS_DISABLED; break;
case 1: opt.extended_ms = SSL_EXTENDED_MS_ENABLED; break;
default: goto usage;
}
}
else if( strcmp( p, "tickets" ) == 0 )
{
opt.tickets = atoi( q );
@ -1257,6 +1277,11 @@ int main( int argc, char *argv[] )
};
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
if( opt.extended_ms != DFL_EXTENDED_MS )
ssl_set_extended_master_secret( &ssl, opt.extended_ms );
#endif
#if defined(POLARSSL_SSL_ALPN)
if( opt.alpn_string != NULL )
if( ( ret = ssl_set_alpn_protocols( &ssl, alpn_list ) ) != 0 )

35
tests/ssl-opt.sh
View file

@ -440,6 +440,41 @@ run_test "Truncated HMAC: actual test" \
0 \
-s "dumping 'computed mac' (10 bytes)"
# Tests for Extended Master Secret extension
run_test "Extended Master Secret: default" \
"$P_SRV debug_level=3" \
"$P_CLI debug_level=3" \
0 \
-c "client hello, adding extended_master_secret extension" \
-s "found extended master secret extension" \
-s "server hello, adding extended master secret extension" \
-c "found extended_master_secret extension" \
-c "using extended master secret" \
-s "using extended master secret"
run_test "Extended Master Secret: client enabled, server disabled" \
"$P_SRV debug_level=3 extended_ms=0" \
"$P_CLI debug_level=3 extended_ms=1" \
0 \
-c "client hello, adding extended_master_secret extension" \
-s "found extended master secret extension" \
-S "server hello, adding extended master secret extension" \
-C "found extended_master_secret extension" \
-C "using extended master secret" \
-S "using extended master secret"
run_test "Extended Master Secret: client disabled, server enabled" \
"$P_SRV debug_level=3 extended_ms=1" \
"$P_CLI debug_level=3 extended_ms=0" \
0 \
-C "client hello, adding extended_master_secret extension" \
-S "found extended master secret extension" \
-S "server hello, adding extended master secret extension" \
-C "found extended_master_secret extension" \
-C "using extended master secret" \
-S "using extended master secret"
# Tests for FALLBACK_SCSV
run_test "Fallback SCSV: default" \