Changelog entry for the mbedtls_mpi_read_xxx changes
mbedtls_mpi_read_binary{,_le} (in https://github.com/ARMmbed/mbedtls/pull/4276)
and mbedtls_mpi_read_string (in https://github.com/ARMmbed/mbedtls/pull/4644)
changed their behavior on an empty input from constructing an MPI object with
one limb to not allocating a limb. In principle, this change should be
transparent to applications, however it caused a bug in the library and it does
affect the value when writing back out, so list the change in the changelog.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/mpi_read_zero.txt b/ChangeLog.d/mpi_read_zero.txt
new file mode 100644
index 0000000..0c25159
--- /dev/null
+++ b/ChangeLog.d/mpi_read_zero.txt
@@ -0,0 +1,9 @@
+Changes
+ * mbedtls_mpi_read_binary(), mbedtls_mpi_read_binary_le() and
+ mbedtls_mpi_read_string() now construct an mbedtls_mpi object with 0 limbs
+ when their input has length 0. Note that this is an implementation detail
+ and can change at any time, so this change should be transparent, but it
+ may result in mbedtls_mpi_write_binary() or mbedtls_mpi_write_string()
+ now writing an empty string where it previously wrote one or more
+ zero digits when operating from values constructed with an mpi_read
+ function and some mpi operations.