Fix indentation and add goto cleanup; stmt

library/md.c

diff --git a/library/md.c b/library/md.c
index 625b34c..cec4243 100644
--- a/library/md.c
+++ b/library/md.c
@@ -436,7 +436,8 @@
         goto cleanup;
     if( ( ret = mbedtls_md_hmac_update( &ctx, input, ilen ) ) != 0 )
         goto cleanup;
-    ret = mbedtls_md_hmac_finish( &ctx, output );
+    if( ( ret = mbedtls_md_hmac_finish( &ctx, output ) ) != 0 )
+        goto cleanup;
 
 cleanup:
     mbedtls_md_free( &ctx );