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Implement initial negotiation of EtM

Browse source 
Not implemented yet:
- actually using EtM
- conditions on renegotiation
This commit is contained in:
Manuel Pégourié-Gonnard 2014-10-27 13:57:03 +01:00
parent b3c6a97b31
commit 699cafaea2
9 changed files with 308 additions and 2 deletions
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7
include/polarssl/check_config.h
View file

@ -257,6 +257,13 @@
#error "Illegal protocol selection"
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC) && \
!defined(POLARSSL_SSL_PROTO_TLS1) && \
!defined(POLARSSL_SSL_PROTO_TLS1_1) && \
!defined(POLARSSL_SSL_PROTO_TLS1_2)
#error "POLARSSL_SSL_ENCRYPT_THEN_MAC defined, but not all prerequsites"
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET) && \
!defined(POLARSSL_SSL_PROTO_TLS1) && \
!defined(POLARSSL_SSL_PROTO_TLS1_1) && \

18
include/polarssl/config.h
View file

@ -811,6 +811,24 @@
*/
//#define POLARSSL_SSL_DEBUG_ALL
/** \def POLARSSL_SSL_ENCRYPT_THEN_MAC
*
* Enable support for Encrypt-then-MAC, RFC 7366.
*
* This allows peers that both support it to use a more robust protection for
* ciphersuites using CBC, providing deep resistance against timing attacks
* on the padding or underlying cipher.
*
* This only affects CBC ciphersuites, and is useless if none is defined.
*
* Requires: POLARSSL_SSL_PROTO_TLS1 or
* POLARSSL_SSL_PROTO_TLS1_1 or
* POLARSSL_SSL_PROTO_TLS1_2
*
* Comment this macro to disable support for Encrypt-then-MAC
*/
#define POLARSSL_SSL_ENCRYPT_THEN_MAC
/** \def POLARSSL_SSL_EXTENDED_MASTER_SECRET
*
* Enable support for Extended Master Secret, aka Session Hash

26
include/polarssl/ssl.h
View file

@ -212,6 +212,9 @@
#define SSL_EXTENDED_MS_DISABLED 0
#define SSL_EXTENDED_MS_ENABLED 1
#define SSL_ETM_DISABLED 0
#define SSL_ETM_ENABLED 1
#define SSL_COMPRESS_NULL 0
#define SSL_COMPRESS_DEFLATE 1
@ -409,6 +412,7 @@
#define TLS_EXT_ALPN 16
#define TLS_EXT_ENCRYPT_THEN_MAC 22 /* 0x16 */
#define TLS_EXT_EXTENDED_MASTER_SECRET 0x0017 /* 23 */
#define TLS_EXT_SESSION_TICKET 35
@ -548,6 +552,10 @@ struct _ssl_session
#if defined(POLARSSL_SSL_TRUNCATED_HMAC)
int trunc_hmac; /*!< flag for truncated hmac activation */
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
int encrypt_then_mac; /*!< flag for EtM activation */
#endif
};
/*
@ -713,6 +721,9 @@ 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_ENCRYPT_THEN_MAC)
char encrypt_then_mac; /*!< flag for encrypt-then-mac */
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
char extended_ms; /*!< flag for extended master secret */
#endif
@ -1425,6 +1436,21 @@ 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_ENCRYPT_THEN_MAC)
/**
* \brief Enable or disable Encrypt-then-MAC
* (Default: SSL_ETM_ENABLED)
*
* \note This should always be enabled, it is a security
* improvement, and should not cause any interoperability
* issue (used only if the peer supports it too).
*
* \param ssl SSL context
* \param etm SSL_ETM_ENABLED or SSL_ETM_DISABLED
*/
void ssl_set_encrypt_then_mac( ssl_context *ssl, char etm );
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
/**
* \brief Enable or disable Extended Master Secret negotiation.

64
library/ssl_cli.c
View file

@ -359,6 +359,32 @@ static void ssl_write_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
static void ssl_write_encrypt_then_mac_ext( ssl_context *ssl,
unsigned char *buf, size_t *olen )
{
unsigned char *p = buf;
if( ssl->encrypt_then_mac == SSL_ETM_DISABLED ||
ssl->max_minor_ver == SSL_MINOR_VERSION_0 )
{
*olen = 0;
return;
}
SSL_DEBUG_MSG( 3, ( "client hello, adding encrypt_then_mac "
"extension" ) );
*p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC ) & 0xFF );
*p++ = 0x00;
*p++ = 0x00;
*olen = 4;
}
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static void ssl_write_extended_ms_ext( ssl_context *ssl,
unsigned char *buf, size_t *olen )
@ -688,6 +714,11 @@ static int ssl_write_client_hello( ssl_context *ssl )
ext_len += olen;
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
ssl_write_encrypt_then_mac_ext( ssl, p + 2 + ext_len, &olen );
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;
@ -811,6 +842,26 @@ static int ssl_parse_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
static int ssl_parse_encrypt_then_mac_ext( ssl_context *ssl,
const unsigned char *buf,
size_t len )
{
if( ssl->encrypt_then_mac == SSL_ETM_DISABLED ||
ssl->minor_ver == SSL_MINOR_VERSION_0 ||
len != 0 )
{
return( POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO );
}
((void) buf);
ssl->session_negotiate->encrypt_then_mac = SSL_ETM_ENABLED;
return( 0 );
}
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static int ssl_parse_extended_ms_ext( ssl_context *ssl,
const unsigned char *buf,
@ -1203,6 +1254,19 @@ static int ssl_parse_server_hello( ssl_context *ssl )
break;
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
case TLS_EXT_ENCRYPT_THEN_MAC:
SSL_DEBUG_MSG( 3, ( "found encrypt_then_mac extension" ) );
if( ( ret = ssl_parse_encrypt_then_mac_ext( ssl,
ext + 4, ext_size ) ) != 0 )
{
return( ret );
}
break;
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
case TLS_EXT_EXTENDED_MASTER_SECRET:
SSL_DEBUG_MSG( 3, ( "found extended_master_secret extension" ) );

64
library/ssl_srv.c
View file

@ -635,6 +635,29 @@ static int ssl_parse_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
static int ssl_parse_encrypt_then_mac_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->encrypt_then_mac == SSL_ETM_ENABLED &&
ssl->minor_ver != SSL_MINOR_VERSION_0 )
{
ssl->session_negotiate->encrypt_then_mac = SSL_ETM_ENABLED;
}
return( 0 );
}
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static int ssl_parse_extended_ms_ext( ssl_context *ssl,
const unsigned char *buf,
@ -1523,6 +1546,16 @@ static int ssl_parse_client_hello( ssl_context *ssl )
break;
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
case TLS_EXT_ENCRYPT_THEN_MAC:
SSL_DEBUG_MSG( 3, ( "found encrypt then mac extension" ) );
ret = ssl_parse_encrypt_then_mac_ext( ssl, ext + 4, ext_size );
if( ret != 0 )
return( ret );
break;
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
case TLS_EXT_EXTENDED_MASTER_SECRET:
SSL_DEBUG_MSG( 3, ( "found extended master secret extension" ) );
@ -1682,6 +1715,32 @@ static void ssl_write_truncated_hmac_ext( ssl_context *ssl,
}
#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
static void ssl_write_encrypt_then_mac_ext( ssl_context *ssl,
unsigned char *buf,
size_t *olen )
{
unsigned char *p = buf;
if( ssl->session_negotiate->encrypt_then_mac == SSL_EXTENDED_MS_DISABLED ||
ssl->minor_ver == SSL_MINOR_VERSION_0 )
{
*olen = 0;
return;
}
SSL_DEBUG_MSG( 3, ( "server hello, adding encrypt then mac extension" ) );
*p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC ) & 0xFF );
*p++ = 0x00;
*p++ = 0x00;
*olen = 4;
}
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
static void ssl_write_extended_ms_ext( ssl_context *ssl,
unsigned char *buf,
@ -2012,6 +2071,11 @@ static int ssl_write_server_hello( ssl_context *ssl )
ext_len += olen;
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
ssl_write_encrypt_then_mac_ext( ssl, p + 2 + ext_len, &olen );
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;

20
library/ssl_tls.c
View file

@ -1071,6 +1071,15 @@ static int ssl_encrypt_buf( ssl_context *ssl )
SSL_DEBUG_MSG( 2, ( "=> encrypt buf" ) );
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
if( ssl->session_out != NULL &&
ssl->session_out->encrypt_then_mac == SSL_ETM_ENABLED )
{
// WIP
SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
}
#endif
/*
* Add MAC before encrypt, except for AEAD modes
*/
@ -3474,6 +3483,10 @@ 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_ENCRYPT_THEN_MAC)
ssl->encrypt_then_mac = SSL_ETM_ENABLED;
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
ssl->extended_ms = SSL_EXTENDED_MS_ENABLED;
#endif
@ -4025,6 +4038,13 @@ void ssl_set_fallback( ssl_context *ssl, char fallback )
}
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
void ssl_set_encrypt_then_mac( ssl_context *ssl, char etm )
{
ssl->encrypt_then_mac = etm;
}
#endif
#if defined(POLARSSL_SSL_EXTENDED_MASTER_SECRET)
void ssl_set_extended_master_secret( ssl_context *ssl, char ems )
{

25
programs/ssl/ssl_client2.c
View file

@ -97,6 +97,7 @@ int main( int argc, char *argv[] )
#define DFL_ALPN_STRING NULL
#define DFL_FALLBACK -1
#define DFL_EXTENDED_MS -1
#define DFL_ETM -1
#define GET_REQUEST "GET %s HTTP/1.0\r\nExtra-header: "
#define GET_REQUEST_END "\r\n\r\n"
@ -136,6 +137,7 @@ struct options
const char *alpn_string; /* ALPN supported protocols */
int fallback; /* is this a fallback connection? */
char extended_ms; /* negotiate extended master secret? */
char etm; ; /* negotiate encrypt then mac? ? */
} opt;
static void my_debug( void *ctx, int level, const char *str )
@ -302,6 +304,13 @@ static int my_verify( void *data, x509_crt *crt, int depth, int *flags )
#define USAGE_EMS ""
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
#define USAGE_ETM \
" etm=0/1 default: (library default: on)\n"
#else
#define USAGE_ETM ""
#endif
#define USAGE \
"\n usage: ssl_client2 param=<>...\n" \
"\n acceptable parameters:\n" \
@ -333,6 +342,7 @@ static int my_verify( void *data, x509_crt *crt, int depth, int *flags )
USAGE_ALPN \
USAGE_FALLBACK \
USAGE_EMS \
USAGE_ETM \
"\n" \
" min_version=%%s default: \"\" (ssl3)\n" \
" max_version=%%s default: \"\" (tls1_2)\n" \
@ -435,6 +445,7 @@ int main( int argc, char *argv[] )
opt.alpn_string = DFL_ALPN_STRING;
opt.fallback = DFL_FALLBACK;
opt.extended_ms = DFL_EXTENDED_MS;
opt.etm = DFL_ETM;
for( i = 1; i < argc; i++ )
{
@ -559,6 +570,15 @@ int main( int argc, char *argv[] )
default: goto usage;
}
}
else if( strcmp( p, "etm" ) == 0 )
{
switch( atoi( q ) )
{
case 0: opt.etm = SSL_ETM_DISABLED; break;
case 1: opt.etm = SSL_ETM_ENABLED; break;
default: goto usage;
}
}
else if( strcmp( p, "min_version" ) == 0 )
{
if( strcmp( q, "ssl3" ) == 0 )
@ -927,6 +947,11 @@ int main( int argc, char *argv[] )
ssl_set_extended_master_secret( &ssl, opt.extended_ms );
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
if( opt.etm != DFL_ETM )
ssl_set_encrypt_then_mac( &ssl, opt.etm );
#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

@ -117,6 +117,7 @@ int main( int argc, char *argv[] )
#define DFL_ALPN_STRING NULL
#define DFL_DHM_FILE NULL
#define DFL_EXTENDED_MS -1
#define DFL_ETM -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" \
@ -178,6 +179,7 @@ struct options
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? */
char etm; /* allow negotiation of encrypt-then-MAC? */
} opt;
static void my_debug( void *ctx, int level, const char *str )
@ -308,6 +310,13 @@ static int my_send( void *ctx, const unsigned char *buf, size_t len )
#define USAGE_EMS ""
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
#define USAGE_ETM \
" etm=0/1 default: (library default: on)\n"
#else
#define USAGE_ETM ""
#endif
#define USAGE \
"\n usage: ssl_server2 param=<>...\n" \
"\n acceptable parameters:\n" \
@ -334,6 +343,7 @@ static int my_send( void *ctx, const unsigned char *buf, size_t len )
USAGE_MAX_FRAG_LEN \
USAGE_ALPN \
USAGE_EMS \
USAGE_ETM \
"\n" \
" min_version=%%s default: \"ssl3\"\n" \
" max_version=%%s default: \"tls1_2\"\n" \
@ -724,6 +734,7 @@ int main( int argc, char *argv[] )
opt.alpn_string = DFL_ALPN_STRING;
opt.dhm_file = DFL_DHM_FILE;
opt.extended_ms = DFL_EXTENDED_MS;
opt.etm = DFL_ETM;
for( i = 1; i < argc; i++ )
{
@ -900,6 +911,15 @@ int main( int argc, char *argv[] )
default: goto usage;
}
}
else if( strcmp( p, "etm" ) == 0 )
{
switch( atoi( q ) )
{
case 0: opt.etm = SSL_ETM_DISABLED; break;
case 1: opt.etm = SSL_ETM_ENABLED; break;
default: goto usage;
}
}
else if( strcmp( p, "tickets" ) == 0 )
{
opt.tickets = atoi( q );
@ -1282,6 +1302,11 @@ int main( int argc, char *argv[] )
ssl_set_extended_master_secret( &ssl, opt.extended_ms );
#endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
if( opt.etm != DFL_ETM )
ssl_set_encrypt_then_mac( &ssl, opt.etm );
#endif
#if defined(POLARSSL_SSL_ALPN)
if( opt.alpn_string != NULL )
if( ( ret = ssl_set_alpn_protocols( &ssl, alpn_list ) ) != 0 )

61
tests/ssl-opt.sh
View file

@ -247,14 +247,14 @@ run_test() {
if is_polar "$SRV_CMD"; then
if grep "Performing the SSL/TLS handshake" $SRV_OUT >/dev/null; then :;
else
fail "server failed to start"
fail "server or client failed to reach handshake stage"
return
fi
fi
if is_polar "$CLI_CMD"; then
if grep "Performing the SSL/TLS handshake" $CLI_OUT >/dev/null; then :;
else
fail "client failed to start"
fail "server or client failed to reach handshake stage"
return
fi
fi
@ -440,6 +440,63 @@ run_test "Truncated HMAC: actual test" \
0 \
-s "dumping 'computed mac' (10 bytes)"
# Tests for Encrypt-then-MAC extension
run_test "Encrypt then MAC: default" \
"$P_SRV debug_level=3" \
"$P_CLI debug_level=3" \
0 \
-c "client hello, adding encrypt_then_mac extension" \
-s "found encrypt then mac extension" \
-s "server hello, adding encrypt then mac extension" \
-c "found encrypt_then_mac extension" \
-c "using encrypt then mac" \
-s "using encrypt then mac"
run_test "Encrypt then MAC: client enabled, server disabled" \
"$P_SRV debug_level=3 etm=0" \
"$P_CLI debug_level=3 etm=1" \
0 \
-c "client hello, adding encrypt_then_mac extension" \
-s "found encrypt then mac extension" \
-S "server hello, adding encrypt then mac extension" \
-C "found encrypt_then_mac extension" \
-C "using encrypt then mac" \
-S "using encrypt then mac"
run_test "Encrypt then MAC: client disabled, server enabled" \
"$P_SRV debug_level=3 etm=1" \
"$P_CLI debug_level=3 etm=0" \
0 \
-C "client hello, adding encrypt_then_mac extension" \
-S "found encrypt then mac extension" \
-S "server hello, adding encrypt then mac extension" \
-C "found encrypt_then_mac extension" \
-C "using encrypt then mac" \
-S "using encrypt then mac"
run_test "Encrypt then MAC: client SSLv3, server enabled" \
"$P_SRV debug_level=3" \
"$P_CLI debug_level=3 force_version=ssl3" \
0 \
-C "client hello, adding encrypt_then_mac extension" \
-S "found encrypt then mac extension" \
-S "server hello, adding encrypt then mac extension" \
-C "found encrypt_then_mac extension" \
-C "using encrypt then mac" \
-S "using encrypt then mac"
run_test "Encrypt then MAC: client enabled, server SSLv3" \
"$P_SRV debug_level=3 force_version=ssl3" \
"$P_CLI debug_level=3" \
0 \
-c "client hello, adding encrypt_then_mac extension" \
-s "found encrypt then mac extension" \
-S "server hello, adding encrypt then mac extension" \
-C "found encrypt_then_mac extension" \
-C "using encrypt then mac" \
-S "using encrypt then mac"
# Tests for Extended Master Secret extension
run_test "Extended Master Secret: default" \