Add guard to out_left to avoid negative values
return error when f_send return a value greater than out_left
diff --git a/ChangeLog b/ChangeLog
index 708ecad..d82600c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -23,6 +23,8 @@
Contributed by Mathieu Briand.
* Fix typo in a comment ctr_drbg.c. Contributed by Paul Sokolovsky.
* Remove support for the library reference configuration for picocoin.
+ * Add guard to validate that out_left can not be negative. Raised by
+ samoconnor in #1245.
= mbed TLS 2.7.0 branch released 2018-02-03