Enforce NULL context for hardcoded RNG

configs/baremetal.h

@@ -106,7 +106,7 @@
 #define MBEDTLS_SSL_CONF_RECV mbedtls_net_recv
 #define MBEDTLS_SSL_CONF_SEND mbedtls_net_send
 #define MBEDTLS_SSL_CONF_RECV_TIMEOUT mbedtls_net_recv_timeout
-#define MBEDTLS_SSL_CONF_RNG mbedtls_hmac_drbg_random
+#define MBEDTLS_SSL_CONF_RNG rng_wrap
 #define MBEDTLS_SSL_CONF_MIN_MINOR_VER MBEDTLS_SSL_MINOR_VERSION_3
 #define MBEDTLS_SSL_CONF_MAX_MINOR_VER MBEDTLS_SSL_MINOR_VERSION_3
 #define MBEDTLS_SSL_CONF_MIN_MAJOR_VER MBEDTLS_SSL_MAJOR_VERSION_3

configs/baremetal_test.h

@@ -51,8 +51,6 @@
 
 /* ssl_client2 and ssl_server2 use CTR-DRBG so far. */
 #define MBEDTLS_CTR_DRBG_C
-#undef MBEDTLS_SSL_CONF_RNG
-#define MBEDTLS_SSL_CONF_RNG mbedtls_ctr_drbg_random
 
 /* The ticket implementation hardcodes AES-GCM */
 #define MBEDTLS_GCM_C

include/mbedtls/config.h

@@ -3668,9 +3668,10 @@
 /* The PRNG to use by the SSL module. If defined, this must
  * evaluate to the name on externally defined function with signature
  * int f_rng(void *, unsigned char *, size_t),
- * e.g. mbedtls_ctr_drbg_random or mbedtls_hmac_drbg_random.
+ * which ignores its first parameter (the stack will always
+ * pass NULL to this function).
  */
-//#define MBEDTLS_SSL_CONF_RNG mbedtls_ctr_drbg_random
+//#define MBEDTLS_SSL_CONF_RNG rng_wrap
 
 /* TLS version */
 //#define MBEDTLS_SSL_CONF_MIN_MINOR_VER MBEDTLS_SSL_MINOR_VERSION_3

include/mbedtls/ssl.h

@@ -1000,8 +1000,8 @@ struct mbedtls_ssl_config
 #if !defined(MBEDTLS_SSL_CONF_RNG)
     /** Callback for getting (pseudo-)random numbers                        */
     int  (*f_rng)(void *, unsigned char *, size_t);
-#endif /* !MBEDTLS_SSL_CONF_RNG */
     void *p_rng;                    /*!< context for the RNG function       */
+#endif /* !MBEDTLS_SSL_CONF_RNG */
 
 #if defined(MBEDTLS_SSL_SRV_C) && !defined(MBEDTLS_SSL_NO_SESSION_CACHE)
     /** Callback to retrieve a session from the cache                       */
@@ -1601,15 +1601,6 @@ void mbedtls_ssl_conf_verify( mbedtls_ssl_config *conf,
 void mbedtls_ssl_conf_rng( mbedtls_ssl_config *conf,
                   int (*f_rng)(void *, unsigned char *, size_t),
                   void *p_rng );
-#else /* !MBEDTLS_SSL_CONF_RNG */
-/**
- * \brief          Set the random number generator callback context.
- *
- * \param conf     SSL configuration
- * \param p_rng    RNG parameter
- */
-void mbedtls_ssl_conf_rng_ctx( mbedtls_ssl_config *conf,
-                               void *p_rng );
 #endif /* MBEDTLS_SSL_CONF_RNG */
 
 #if defined(MBEDTLS_DEBUG_C)

include/mbedtls/ssl_internal.h

@@ -1560,18 +1560,18 @@ static inline mbedtls_ssl_recv_timeout_t* mbedtls_ssl_get_recv_timeout(
 
 typedef int mbedtls_frng_t( void*, unsigned char*, size_t );
 
-static inline void* mbedtls_ssl_conf_get_prng( mbedtls_ssl_config const *conf )
-{
-    return( conf->p_rng );
-}
 #if !defined(MBEDTLS_SSL_CONF_RNG)
 static inline mbedtls_frng_t* mbedtls_ssl_conf_get_frng(
     mbedtls_ssl_config const *conf )
 {
     return( conf->f_rng );
 }
-#else /* !MBEDTLS_SSL_CONF_RNG */
 
+static inline void* mbedtls_ssl_conf_get_prng( mbedtls_ssl_config const *conf )
+{
+    return( conf->p_rng );
+}
+#else /* !MBEDTLS_SSL_CONF_RNG */
 #define mbedtls_ssl_conf_rng_func MBEDTLS_SSL_CONF_RNG
 extern int mbedtls_ssl_conf_rng_func( void*, unsigned char*, size_t );
 
@@ -1581,6 +1581,12 @@ static inline mbedtls_frng_t* mbedtls_ssl_conf_get_frng(
     ((void) conf);
     return ((mbedtls_frng_t*) mbedtls_ssl_conf_rng_func);
 }
+
+static inline void* mbedtls_ssl_conf_get_prng( mbedtls_ssl_config const *conf )
+{
+    ((void) conf);
+    return( NULL );
+}
 #endif /* MBEDTLS_SSL_CONF_RNG */
 
 static inline int mbedtls_ssl_conf_get_max_major_ver(

library/ssl_tls.c

@@ -8510,12 +8510,6 @@ void mbedtls_ssl_conf_rng( mbedtls_ssl_config *conf,
     conf->f_rng      = f_rng;
     conf->p_rng      = p_rng;
 }
-#else
-void mbedtls_ssl_conf_rng_ctx( mbedtls_ssl_config *conf,
-                               void *p_rng )
-{
-    conf->p_rng      = p_rng;
-}
 #endif
 
 #if defined(MBEDTLS_DEBUG_C)

programs/ssl/dtls_client.c

@@ -95,6 +95,20 @@ static void my_debug( void *ctx, int level,
 }
 #endif /* MBEDTLS_DEBUG_C */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( int argc, char *argv[] )
 {
     int ret, len;
@@ -192,7 +206,13 @@ int main( int argc, char *argv[] )
      * Production code should set a proper ca chain and use REQUIRED. */
     mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
     mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );
+
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

programs/ssl/dtls_server.c

@@ -104,6 +104,20 @@ static void my_debug( void *ctx, int level,
 }
 #endif /* MBEDTLS_DEBUG_C */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( void )
 {
     int ret, len;
@@ -224,7 +238,12 @@ int main( void )
         goto exit;
     }
 
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

programs/ssl/mini_client.c

@@ -166,6 +166,19 @@ enum exit_codes
     ssl_write_failed,
 };
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
 
 int main( void )
 {
@@ -212,7 +225,7 @@ int main( void )
 #if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
 #else
-    mbedtls_ssl_conf_rng_ctx( &conf, &ctr_drbg );
+    rng_ctx_global = &ctr_drbg;
 #endif
 
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)

programs/ssl/ssl_client1.c

@@ -85,6 +85,20 @@ static void my_debug( void *ctx, int level,
 }
 #endif /* MBEDTLS_DEBUG_C */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( void )
 {
     int ret = 1, len;
@@ -179,7 +193,13 @@ int main( void )
      * but makes interop easier in this simplified example */
     mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
     mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );
+
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

programs/ssl/ssl_client2.c

@@ -889,6 +889,20 @@ int report_cid_usage( mbedtls_ssl_context *ssl,
 }
 #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( int argc, char *argv[] )
 {
     int ret = 0, len, tail_len, i, written, frags, retry_left;
@@ -1942,7 +1956,7 @@ int main( int argc, char *argv[] )
 #if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
 #else
-    mbedtls_ssl_conf_rng_ctx( &conf, &ctr_drbg );
+    rng_ctx_global = &ctr_drbg;
 #endif
 
 #if defined(MBEDTLS_DEBUG_C)

programs/ssl/ssl_fork_server.c

@@ -102,6 +102,20 @@ static void my_debug( void *ctx, int level,
 }
 #endif /* MBEDTLS_DEBUG_C */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( void )
 {
     int ret = 1, len, cnt = 0, pid;
@@ -196,7 +210,12 @@ int main( void )
         goto exit;
     }
 
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

programs/ssl/ssl_mail_client.c

@@ -361,6 +361,20 @@ static int write_and_get_response( mbedtls_net_context *sock_fd, unsigned char *
     while( 1 );
 }
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( int argc, char *argv[] )
 {
     int ret = 1, len;
@@ -620,7 +634,12 @@ int main( int argc, char *argv[] )
      * but makes interop easier in this simplified example */
     mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
 
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

programs/ssl/ssl_pthread_server.c

@@ -325,6 +325,20 @@ static int thread_create( mbedtls_net_context *client_fd )
     return( 0 );
 }
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( void )
 {
     int ret;
@@ -439,7 +453,12 @@ int main( void )
         goto exit;
     }
 
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_mutexed_debug, stdout );
 #endif

programs/ssl/ssl_server.c

@@ -97,6 +97,20 @@ static void my_debug( void *ctx, int level,
 }
 #endif /* MBEDTLS_DEBUG_C */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( void )
 {
     int ret, len;
@@ -212,7 +226,12 @@ int main( void )
         goto exit;
     }
 
+#if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

programs/ssl/ssl_server2.c

@@ -1505,6 +1505,20 @@ int report_cid_usage( mbedtls_ssl_context *ssl,
 }
 #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( int argc, char *argv[] )
 {
     int ret = 0, len, written, frags, exchanges_left;
@@ -2754,7 +2768,7 @@ int main( int argc, char *argv[] )
 #if !defined(MBEDTLS_SSL_CONF_RNG)
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
 #else
-    mbedtls_ssl_conf_rng_ctx( &conf, &ctr_drbg );
+    rng_ctx_global = &ctr_drbg;
 #endif
 
 #if defined(MBEDTLS_DEBUG_C)

programs/x509/cert_app.c

@@ -149,6 +149,20 @@ static int my_verify( void *data, mbedtls_x509_crt *crt, int depth, uint32_t *fl
     return( 0 );
 }
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len );
+
+mbedtls_ctr_drbg_context *rng_ctx_global = NULL;
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    /* We expect the NULL parameter here. */
+    if( ctx != NULL )
+        return( -1 );
+
+    return( mbedtls_ctr_drbg_random( rng_ctx_global, dst, len ) );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 int main( int argc, char *argv[] )
 {
     int ret = 1;
@@ -424,7 +438,12 @@ int main( int argc, char *argv[] )
         else
             mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_NONE );
 
-        mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#if !defined(MBEDTLS_SSL_CONF_RNG)
+    mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
+#else
+    rng_ctx_global = &ctr_drbg;
+#endif
+
 #if defined(MBEDTLS_DEBUG_C)
         mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );
 #endif

tests/suites/helpers.function

@@ -356,6 +356,18 @@ void mbedtls_param_failed( const char *failure_condition,
 }
 #endif
 
+#if defined(MBEDTLS_SSL_CONF_RNG)
+int rng_wrap( void *ctx, unsigned char *dst, size_t len )
+{
+    ((void) ctx);
+    ((void) dst);
+    ((void) len);
+    /* We don't expect test suites to use SSL functionality
+     * that would trigger the hardcoded RNG. */
+    return( -1 );
+}
+#endif /* MBEDTLS_SSL_CONF_RNG */
+
 #if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
 static int redirect_output( FILE** out_stream, const char* path )
 {