diff --git a/ChangeLog b/ChangeLog
index 070e55eb2..dc008f8fb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,6 +22,8 @@ Features
from the default list (inactive by default).
* Add server-side enforcement of sent renegotiation requests
(ssl_set_renegotiation_enforced())
+ * Add SSL_CIPHERSUITES config.h flag to allow specifying a list of
+ ciphersuites to use and save some memory if the list is small.
Changes
* Add LINK_WITH_PTHREAD option in CMake for explicit linking that is
diff --git a/configs/config-ccm-psk-tls1_2.h b/configs/config-ccm-psk-tls1_2.h
index f425391d0..1da9f6a6b 100644
--- a/configs/config-ccm-psk-tls1_2.h
+++ b/configs/config-ccm-psk-tls1_2.h
@@ -3,7 +3,7 @@
* Distinguishing features:
* - no bignum, no PK, no X509
* - fully modern and secure (provided the pre-shared keys have high entropy)
- * - very low record overhead if using the CCM-8 suites
+ * - very low record overhead with CCM-8
* - optimized for low RAM usage
*
* See README.txt for usage instructions.
@@ -13,7 +13,7 @@
/* System support */
//#define POLARSSL_HAVE_IPV6 /* Optional */
-//#define POLARSSL_HAVE_TIME /* Optionnaly used in Hello messages */
+//#define POLARSSL_HAVE_TIME /* Optionally used in Hello messages */
/* Other POLARSSL_HAVE_XXX flags irrelevant for this configuration */
/* PolarSSL feature support */
@@ -36,6 +36,9 @@
/* Save RAM at the expense of ROM */
#define POLARSSL_AES_ROM_TABLES
+/* Save some RAM by adjusting to your exact needs */
+#define POLARSSL_PSK_MAX_LEN 16 /* 128-bits keys are generally enough */
+
/*
* You should adjust this to the exact number of sources you're using: default
* is the "platform_entropy_poll" source, but you may want to add other ones
@@ -43,9 +46,17 @@
*/
#define ENTROPY_MAX_SOURCES 2
+/*
+ * Use only CCM_8 ciphersuites, and
+ * save ROM and a few bytes of RAM by specifying our own ciphersuite list
+ */
+#define SSL_CIPHERSUITES \
+ TLS_PSK_WITH_AES_256_CCM_8, \
+ TLS_PSK_WITH_AES_128_CCM_8
+
/*
* Save RAM at the expense of interoperability: do this only if you control
- * both ends of the connection! (See coments in "polarssl/ssl.h".)
+ * both ends of the connection! (See comments in "polarssl/ssl.h".)
* The optimal size here depends on the typical size of records.
*/
#define SSL_MAX_CONTENT_LEN 512
diff --git a/configs/config-suite-b.h b/configs/config-suite-b.h
index d10cf6320..cd38f3334 100644
--- a/configs/config-suite-b.h
+++ b/configs/config-suite-b.h
@@ -77,6 +77,11 @@
*/
#define ENTROPY_MAX_SOURCES 2
+/* Save ROM and a few bytes of RAM by specifying our own ciphersuite list */
+#define SSL_CIPHERSUITES \
+ TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, \
+ TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
+
/*
* Save RAM at the expense of interoperability: do this only if you control
* both ends of the connection! (See coments in "polarssl/ssl.h".)
diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index bfd68c401..d43365ff5 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -2154,6 +2154,21 @@
/* SSL options */
//#define SSL_MAX_CONTENT_LEN 16384 /**< Size of the input / output buffer */
//#define SSL_DEFAULT_TICKET_LIFETIME 86400 /**< Lifetime of session tickets (if enabled) */
+//#define POLARSSL_PSK_MAX_LEN 32 /**< Max size of TLS pre-shared keys, in bytes (default 256 bits) */
+
+/**
+ * Complete list of ciphersuites to use, in order of preference.
+ *
+ * \warning No dependency checking is done on that field! This option can only
+ * be used to restrict the set of available ciphersuites. It is your
+ * responsibility to make sure the needed modules are active.
+ *
+ * Use this to save a few hundred bytes of ROM (default ordering of all
+ * available ciphersuites) and a few to a few hundred bytes of RAM.
+ *
+ * The value below is only an example, not the default.
+ */
+//#define SSL_CIPHERSUITES TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
/* Debug options */
//#define POLARSSL_DEBUG_DFL_MODE POLARSSL_DEBUG_LOG_FULL /**< Default log: Full or Raw */
diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index b90b232a5..730dc3937 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -34,6 +34,7 @@
#endif
#include "net.h"
#include "bignum.h"
+#include "ecp.h"
#include "ssl_ciphersuites.h"
@@ -252,7 +253,9 @@
* Note: the RFC defines the default size of SSL / TLS messages. If you
* change the value here, other clients / servers may not be able to
* communicate with you anymore. Only change this value if you control
- * both sides of the connection and have it reduced at both sides!
+ * both sides of the connection and have it reduced at both sides, or
+ * if you're using the Max Fragment Length extension and you know all your
+ * peers are using it too!
*/
#if !defined(SSL_MAX_CONTENT_LEN)
#define SSL_MAX_CONTENT_LEN 16384 /**< Size of the input / output buffer */
@@ -261,8 +264,8 @@
/* \} name SECTION: Module settings */
/*
- * Allow an extra 301 bytes for the record header and encryption overhead:
- * counter (8) + header (5) + IV(16) + MAC (48) + padding (256)
+ * Allow extra bytes for record, authentication and encryption overhead:
+ * counter (8) + header (5) + IV(16) + MAC (16-48) + padding (0-256)
* and allow for a maximum of 1024 of compression expansion if
* enabled.
*/
@@ -272,8 +275,36 @@
#define SSL_COMPRESSION_ADD 0
#endif
-#define SSL_BUFFER_LEN (SSL_MAX_CONTENT_LEN + SSL_COMPRESSION_ADD + 333)
+#if defined(POLARSSL_RC4_C) || defined(POLARSSL_CIPHER_MODE_CBC)
+/* Ciphersuites using HMAC */
+#if defined(POLARSSL_SHA512_C)
+#define SSL_MAC_ADD 48 /* SHA-384 used for HMAC */
+#elif defined(POLARSSL_SHA256_C)
+#define SSL_MAC_ADD 32 /* SHA-256 used for HMAC */
+#else
+#define SSL_MAC_ADD 20 /* SHA-1 used for HMAC */
+#endif
+#else
+/* AEAD ciphersuites: GCM and CCM use a 128 bits tag */
+#define SSL_MAC_ADD 16
+#endif
+#if defined(POLARSSL_CIPHER_MODE_CBC)
+#define SSL_PADDING_ADD 256
+#else
+#define SSL_PADDING_ADD 0
+#endif
+
+#define SSL_BUFFER_LEN ( SSL_MAX_CONTENT_LEN \
+ + SSL_COMPRESSION_ADD \
+ + 29 /* counter + header + IV */ \
+ + SSL_MAC_ADD \
+ + SSL_PADDING_ADD \
+ )
+
+/*
+ * Signaling ciphersuite values (SCSV)
+ */
#define SSL_EMPTY_RENEGOTIATION_INFO 0xFF /**< renegotiation info ext */
/*
@@ -382,12 +413,43 @@
/*
* Size defines
*/
-#if !defined(POLARSSL_MPI_MAX_SIZE)
-#define POLARSSL_PREMASTER_SIZE 512
-#else
-#define POLARSSL_PREMASTER_SIZE POLARSSL_MPI_MAX_SIZE
+#if !defined(POLARSSL_PSK_MAX_LEN)
+#define POLARSSL_PSK_MAX_LEN 32 /* 256 bits */
#endif
+/* Dummy type used only for its size */
+union _ssl_premaster_secret
+{
+#if defined(POLARSSL_KEY_EXCHANGE_RSA_ENABLED)
+ unsigned char _pms_rsa[48]; /* RFC 5246 8.1.1 */
+#endif
+#if defined(POLARSSL_KEY_EXCHANGE_DHE_RSA_ENABLED)
+ unsigned char _pms_dhm[POLARSSL_MPI_MAX_SIZE]; /* RFC 5246 8.1.2 */
+#endif
+#if defined(POLARSSL_KEY_EXCHANGE_ECDHE_RSA_ENABLED) || \
+ defined(POLARSSL_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED) || \
+ defined(POLARSSL_KEY_EXCHANGE_ECDH_RSA_ENABLED) || \
+ defined(POLARSSL_KEY_EXCHANGE_ECDH_ECDSA_ENABLED)
+ unsigned char _pms_ecdh[POLARSSL_ECP_MAX_BYTES]; /* RFC 4492 5.10 */
+#endif
+#if defined(POLARSSL_KEY_EXCHANGE_PSK_ENABLED)
+ unsigned char _pms_psk[4 + 2 * POLARSSL_PSK_MAX_LEN]; /* RFC 4279 2 */
+#endif
+#if defined(POLARSSL_KEY_EXCHANGE_DHE_PSK_ENABLED)
+ unsigned char _pms_dhe_psk[4 + POLARSSL_MPI_MAX_SIZE
+ + POLARSSL_PSK_MAX_LEN]; /* RFC 4279 3 */
+#endif
+#if defined(POLARSSL_KEY_EXCHANGE_RSA_PSK_ENABLED)
+ unsigned char _pms_rsa_psk[52 + POLARSSL_PSK_MAX_LEN]; /* RFC 4279 4 */
+#endif
+#if defined(POLARSSL_KEY_EXCHANGE_DHE_PSK_ENABLED)
+ unsigned char _pms_ecdhe_psk[4 + POLARSSL_ECP_MAX_BYTES
+ + POLARSSL_PSK_MAX_LEN]; /* RFC 5489 2 */
+#endif
+};
+
+#define POLARSSL_PREMASTER_SIZE sizeof( union _ssl_premaster_secret )
+
#ifdef __cplusplus
extern "C" {
#endif
diff --git a/include/polarssl/ssl_ciphersuites.h b/include/polarssl/ssl_ciphersuites.h
index 5ecd5febd..c4f1ffe64 100644
--- a/include/polarssl/ssl_ciphersuites.h
+++ b/include/polarssl/ssl_ciphersuites.h
@@ -233,6 +233,7 @@ extern "C" {
#define TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 0xC0AE /**< TLS 1.2 */
#define TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8 0xC0AF /**< TLS 1.2 */
+/* Reminder: update _ssl_premaster_secret when adding a new key exchange */
typedef enum {
POLARSSL_KEY_EXCHANGE_NONE = 0,
POLARSSL_KEY_EXCHANGE_RSA,
diff --git a/library/ssl_ciphersuites.c b/library/ssl_ciphersuites.c
index 608e26d2f..df838e260 100644
--- a/library/ssl_ciphersuites.c
+++ b/library/ssl_ciphersuites.c
@@ -57,6 +57,9 @@
*/
static const int ciphersuite_preference[] =
{
+#if defined(SSL_CIPHERSUITES)
+ SSL_CIPHERSUITES,
+#else
/* All AES-256 ephemeral suites */
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
@@ -257,13 +260,10 @@ static const int ciphersuite_preference[] =
TLS_PSK_WITH_NULL_SHA256,
TLS_PSK_WITH_NULL_SHA,
+#endif
0
};
-#define MAX_CIPHERSUITES 176
-static int supported_ciphersuites[MAX_CIPHERSUITES];
-static int supported_init = 0;
-
static const ssl_ciphersuite_t ciphersuite_definitions[] =
{
#if defined(POLARSSL_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED)
@@ -1679,6 +1679,17 @@ static const ssl_ciphersuite_t ciphersuite_definitions[] =
{ 0, "", 0, 0, 0, 0, 0, 0, 0, 0 }
};
+#if defined(SSL_CIPHERSUITES)
+const int *ssl_list_ciphersuites( void )
+{
+ return( ciphersuite_preference );
+}
+#else
+#define MAX_CIPHERSUITES sizeof( ciphersuite_definitions ) / \
+ sizeof( ciphersuite_definitions[0] )
+static int supported_ciphersuites[MAX_CIPHERSUITES];
+static int supported_init = 0;
+
const int *ssl_list_ciphersuites( void )
{
/*
@@ -1687,21 +1698,21 @@ const int *ssl_list_ciphersuites( void )
*/
if( supported_init == 0 )
{
- const int *p = ciphersuite_preference;
- int *q = supported_ciphersuites;
- size_t i;
- size_t max = sizeof(supported_ciphersuites) / sizeof(int);
+ const int *p;
+ int *q;
- for( i = 0; i < max - 1 && p[i] != 0; i++ )
+ for( p = ciphersuite_preference, q = supported_ciphersuites;
+ *p != 0 && q < supported_ciphersuites + MAX_CIPHERSUITES - 1;
+ p++ )
{
#if defined(POLARSSL_REMOVE_ARC4_CIPHERSUITES)
const ssl_ciphersuite_t *cs_info;
- if( ( cs_info = ssl_ciphersuite_from_id( p[i] ) ) != NULL &&
+ if( ( cs_info = ssl_ciphersuite_from_id( *p ) ) != NULL &&
cs_info->cipher != POLARSSL_CIPHER_ARC4_128 )
#else
- if( ssl_ciphersuite_from_id( p[i] ) != NULL )
+ if( ssl_ciphersuite_from_id( *p ) != NULL )
#endif
- *(q++) = p[i];
+ *(q++) = *p;
}
*q = 0;
@@ -1710,6 +1721,7 @@ const int *ssl_list_ciphersuites( void )
return( supported_ciphersuites );
};
+#endif /* SSL_CIPHERSUITES */
const ssl_ciphersuite_t *ssl_ciphersuite_from_string(
const char *ciphersuite_name )
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 7c8f3064b..8040f9092 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3747,12 +3747,7 @@ int ssl_set_psk( ssl_context *ssl, const unsigned char *psk, size_t psk_len,
if( psk == NULL || psk_identity == NULL )
return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
- /*
- * The length will be check later anyway, but in case it is obviously
- * too large, better abort now. The PMS is as follows:
- * other_len (2 bytes) + other + psk_len (2 bytes) + psk
- */
- if( psk_len + 4 > POLARSSL_PREMASTER_SIZE )
+ if( psk_len > POLARSSL_PSK_MAX_LEN )
return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
if( ssl->psk != NULL )
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 3af54f904..4682ee5bc 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -325,7 +325,7 @@ int main( int argc, char *argv[] )
int ret = 0, len, server_fd, i, written, frags;
unsigned char buf[SSL_MAX_CONTENT_LEN + 1];
#if defined(POLARSSL_KEY_EXCHANGE__SOME__PSK_ENABLED)
- unsigned char psk[256];
+ unsigned char psk[POLARSSL_PSK_MAX_LEN];
size_t psk_len = 0;
#endif
#if defined(POLARSSL_SSL_ALPN)
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 9cb742b3f..c470363b4 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -127,8 +127,6 @@ int main( int argc, char *argv[] )
"PolarSSL Test Server
\r\n" \
"Successful connection using: %s
\r\n" // LONG_RESPONSE
-#define MAX_PSK_LEN 256
-
/*
* Size of the basic I/O buffer. Able to hold our default response.
*
@@ -462,7 +460,7 @@ int unhexify( unsigned char *output, const char *input, size_t *olen )
size_t j;
*olen = strlen( input );
- if( *olen % 2 != 0 || *olen / 2 > MAX_PSK_LEN )
+ if( *olen % 2 != 0 || *olen / 2 > POLARSSL_PSK_MAX_LEN )
return( -1 );
*olen /= 2;
@@ -486,7 +484,7 @@ struct _psk_entry
{
const char *name;
size_t key_len;
- unsigned char key[MAX_PSK_LEN];
+ unsigned char key[POLARSSL_PSK_MAX_LEN];
psk_entry *next;
};
@@ -575,7 +573,7 @@ int main( int argc, char *argv[] )
int version_suites[4][2];
unsigned char buf[IO_BUF_LEN];
#if defined(POLARSSL_KEY_EXCHANGE__SOME__PSK_ENABLED)
- unsigned char psk[MAX_PSK_LEN];
+ unsigned char psk[POLARSSL_PSK_MAX_LEN];
size_t psk_len = 0;
psk_entry *psk_info = NULL;
#endif
diff --git a/tests/scripts/test-ref-configs.pl b/tests/scripts/test-ref-configs.pl
index 9b09e3464..6546b05af 100755
--- a/tests/scripts/test-ref-configs.pl
+++ b/tests/scripts/test-ref-configs.pl
@@ -20,7 +20,7 @@ my %configs = (
'config-picocoin.h'
=> 0,
'config-ccm-psk-tls1_2.h'
- => '-m tls1_2 -f \'TLS-PSK.*AES.*CCM\'',
+ => '-m tls1_2 -f \'^TLS-PSK-WITH-AES-...-CCM-8\'',
);
# If no config-name is provided, use all known configs.