commit c280520999caa75ae40bb0391a5ec7b5a10cd5de
author Dave Rodgman <dave.rodgman@arm.com> Mon Sep 11 18:25:16 2023 +0100
committer Dave Rodgman <dave.rodgman@arm.com> Wed Sep 20 15:14:28 2023 +0100
tree ed4bda7dfd90e1130411e2c1c60fe2f77aaebc53
parent f4cf4a6e259bf5e925a566874a4f53a4a7c3b96d

Eliminate duplicate ct memcmp

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

library/gcm.c

diff --git a/library/gcm.c b/library/gcm.c
index 0c958c7..71e7b2e 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -35,6 +35,7 @@
 #include "mbedtls/platform.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"
+#include "mbedtls/constant_time.h"
 
 #include <string.h>
 
@@ -478,7 +479,6 @@
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     unsigned char check_tag[16];
-    size_t i;
     int diff;
 
     GCM_VALIDATE_RET(ctx != NULL);
@@ -495,9 +495,7 @@
     }
 
     /* Check tag in "constant-time" */
-    for (diff = 0, i = 0; i < tag_len; i++) {
-        diff |= tag[i] ^ check_tag[i];
-    }
+    diff = mbedtls_ct_memcmp(tag, check_tag, tag_len);
 
     if (diff != 0) {
         mbedtls_platform_zeroize(output, length);