Add proper allocation of restart context
We'll need to store MPIs and other things that allocate memory in this
context, so we need a place to free it. We can't rely on doing it before
returning from ecp_mul() as we might return MBEDTLS_ERR_ECP_IN_PROGRESS (thus
preserving the context) and never be called again (for example, TLS handshake
aborted for another reason). So, ecp_group_free() looks like a good place to
do this, if the restart context is part of struct ecp_group.
This means it's not possible to use the same ecp_group structure in different
threads concurrently, but:
- that's already the case (and documented) for other reasons
- this feature is precisely intended for environments that lack threading
An alternative option would be for the caller to have to allocate/free the
restart context and pass it explicitly, but this means creating new functions
that take a context argument, and putting a burden on the user.
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 7bcc69c..d44e658 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -112,6 +112,16 @@
}
mbedtls_ecp_point;
+#if defined(MBEDTLS_ECP_EARLY_RETURN)
+/**
+ * \brief ECP context for resuming operations after returning
+ * \c MBEDTLS_ERR_ECP_IN_PROGRESS
+ *
+ * \note Opaque struct
+ */
+typedef struct mbedtls_ecp_restart mbedtls_ecp_restart_ctx;
+#endif
+
/**
* \brief ECP group structure
*
@@ -153,6 +163,9 @@
void *t_data; /*!< unused */
mbedtls_ecp_point *T; /*!< pre-computed points for ecp_mul_comb() */
size_t T_size; /*!< number for pre-computed points */
+#if defined(MBEDTLS_ECP_EARLY_RETURN)
+ mbedtls_ecp_restart_ctx *rs; /*!< context for resuming operation */
+#endif
}
mbedtls_ecp_group;