Ensure application data records are not kept when fully processed
This commit fixes the following case: If a client is both expecting a
SERVER_HELLO and has an application data record that's partially
processed in flight (that's the situation the client gets into after
receiving a ServerHelloRequest followed by ApplicationData), a
subsequent call to mbedtls_ssl_read will set keep_current_message = 1
when seeing the unexpected application data, but not reset it to 0
after the application data has been processed. This commit fixes this.
It also documents and suggests how the problem might be solved in a
more structural way on the long run.
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 911664e..661ae70 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -6790,6 +6790,41 @@
}
}
+ /*
+ * TODO
+ *
+ * The logic should be streamlined here:
+ *
+ * Instead of
+ *
+ * - Manually checking whether ssl->in_offt is NULL
+ * - Fetching a new record if yes
+ * - Setting ssl->in_offt if one finds an application record
+ * - Resetting keep_current_message after handling the application data
+ *
+ * one should
+ *
+ * - Adapt read_record to set ssl->in_offt automatically
+ * when a new application data record is processed.
+ * - Always call mbedtls_ssl_read_record here.
+ *
+ * This way, the logic of ssl_read would be much clearer:
+ *
+ * (1) Always call record layer and see what kind of record is on
+ * and have it ready for consumption (in particular, in_offt
+ * properly set for application data records).
+ * (2) If it's application data (either freshly fetched
+ * or something already being partially processed),
+ * serve the read request from it.
+ * (3) If it's something different from application data,
+ * handle it accordingly, e.g. potentially start a
+ * renegotiation.
+ *
+ * This will also remove the need to manually reset
+ * ssl->keep_current_message = 0 below.
+ *
+ */
+
if( ssl->in_offt == NULL )
{
/* Start timer if not already running */
@@ -6996,6 +7031,7 @@
{
/* all bytes consumed */
ssl->in_offt = NULL;
+ ssl->keep_current_message = 0;
}
else
{