Allow compile-time configuration of DTLS badmac limit
Introduces MBEDTLS_SSL_CONF_BADMAC_LIMIT to fix the maximum
number of records with bad MAC tolerated in DTLS at compile-time.
Impact on code-size:
| | GCC | ARMC5 | ARMC6 |
| --- | --- | --- | --- |
| `libmbedtls.a` before | 23511 | 24049 | 27903 |
| `libmbedtls.a` after | 23487 | 24025 | 27885 |
| gain in Bytes | 24 | 24 | 18 |
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 1ff34dc..ee292c5 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -3450,8 +3450,9 @@
* \{
*/
-/* DTLS Anti replay */
+/* DTLS-specific settings */
//#define MBEDTLS_SSL_CONF_ANTI_REPLAY MBEDTLS_SSL_ANTI_REPLAY_ENABLED
+//#define MBEDTLS_SSL_CONF_BADMAC_LIMIT 0
/* ExtendedMasterSecret extension
* The following two options must be set/unset simultaneously. */
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index fbc6109..dd546b8 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1029,7 +1029,9 @@
#endif
#if defined(MBEDTLS_SSL_DTLS_BADMAC_LIMIT)
+#if !defined(MBEDTLS_SSL_CONF_BADMAC_LIMIT)
unsigned int badmac_limit; /*!< limit of records with a bad MAC */
+#endif /* !MBEDTLS_SSL_CONF_BADMAC_LIMIT */
#endif
#if defined(MBEDTLS_DHM_C) && defined(MBEDTLS_SSL_CLI_C)
@@ -2043,7 +2045,8 @@
void mbedtls_ssl_conf_dtls_anti_replay( mbedtls_ssl_config *conf, char mode );
#endif /* MBEDTLS_SSL_DTLS_ANTI_REPLAY && !MBEDTLS_SSL_CONF_ANTI_REPLAY */
-#if defined(MBEDTLS_SSL_DTLS_BADMAC_LIMIT)
+#if defined(MBEDTLS_SSL_DTLS_BADMAC_LIMIT) && \
+ !defined(MBEDTLS_SSL_CONF_BADMAC_LIMIT)
/**
* \brief Set a limit on the number of records with a bad MAC
* before terminating the connection.
@@ -2066,9 +2069,13 @@
* connection. On the other hand, a high limit or no limit
* might make us waste resources checking authentication on
* many bogus packets.
+ *
+ * \note On constrained systems, this option can also be
+ * fixed at compile-time by defining the constant
+ * MBEDTLS_SSL_CONF_BADMAC_LIMIT.
*/
void mbedtls_ssl_conf_dtls_badmac_limit( mbedtls_ssl_config *conf, unsigned limit );
-#endif /* MBEDTLS_SSL_DTLS_BADMAC_LIMIT */
+#endif /* MBEDTLS_SSL_DTLS_BADMAC_LIMIT && !MBEDTLS_SSL_CONF_BADMAC_LIMIT */
#if defined(MBEDTLS_SSL_PROTO_DTLS)
diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 092819e..49c6050 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1085,6 +1085,23 @@
* be fixed at compile time via one of MBEDTLS_SSL_SSL_CONF_XXX.
*/
+#if defined(MBEDTLS_SSL_DTLS_BADMAC_LIMIT)
+#if !defined(MBEDTLS_SSL_CONF_BADMAC_LIMIT)
+static inline unsigned int mbedtls_ssl_conf_get_badmac_limit(
+ mbedtls_ssl_config const *conf )
+{
+ return( conf->badmac_limit );
+}
+#else /* !MBEDTLS_SSL_CONF_BADMAC_LIMIT */
+static inline unsigned int mbedtls_ssl_conf_get_badmac_limit(
+ mbedtls_ssl_config const *conf )
+{
+ ((void) conf);
+ return( MBEDTLS_SSL_CONF_BADMAC_LIMIT );
+}
+#endif /* MBEDTLS_SSL_CONF_BADMAC_LIMIT */
+#endif /* MBEDTLS_SSL_DTLS_BADMAC_LIMIT */
+
#if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
#if !defined(MBEDTLS_SSL_CONF_ANTI_REPLAY)
static inline unsigned int mbedtls_ssl_conf_get_anti_replay(