Add output parameter to mbedtls_gcm_finish
Alternative implementations of GCM may delay the output of partial
blocks from mbedtls_gcm_update(). Add an output parameter to
mbedtls_gcm_finish() to allow such implementations to pass the final
partial block back to the caller. With the software implementation,
this final output is always empty.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/gcm-update.txt b/ChangeLog.d/gcm-update.txt
index 4511fec..d384551 100644
--- a/ChangeLog.d/gcm-update.txt
+++ b/ChangeLog.d/gcm-update.txt
@@ -1,3 +1,13 @@
+API changes
+ * The interface of the GCM module has changed to remove restrictions on
+ how the input to multipart operations is broken down. mbedtls_gcm_finish()
+ now takes an extra output parameter for the last partial output block.
+ The software implementation always produces the full output at each
+ call to mbedtls_gcm_update(), but alternative implementations activated
+ by MBEDTLS_GCM_ALT may delay partial blocks to the next call to
+ mbedtls_gcm_update() or mbedtls_gcm_finish().
+ These changes are backward compatible for users of the cipher API.
+
Features
* The multi-part GCM interface (mbedtls_gcm_update() or
mbedtls_cipher_update()) no longer requires the size of partial inputs to