commit b3f2273aed7c48a0121b96e7f27c269a6ea64cea
author Gilles Peskine <Gilles.Peskine@arm.com> Mon Dec 13 16:57:47 2021 +0100
committer Gilles Peskine <Gilles.Peskine@arm.com> Mon Dec 13 16:57:47 2021 +0100
tree fd1644229c19e89c86be2c310497066dc8c59dea
parent 7cab499af26fd0fe134a5e9a29a1e7205b9ccee7

mbedtls_cipher_check_tag: jump on error for more robustness to refactoring

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

library/cipher.c

diff --git a/library/cipher.c b/library/cipher.c
index 348cabf..4ea0221 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -987,7 +987,10 @@
 
         /* Check the tag in "constant-time" */
         if( mbedtls_constant_time_memcmp( tag, check_tag, tag_len ) != 0 )
+        {
             ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
+            goto exit;
+        }
     }
 #endif /* MBEDTLS_GCM_C */
 
@@ -1007,10 +1010,14 @@
 
         /* Check the tag in "constant-time" */
         if( mbedtls_constant_time_memcmp( tag, check_tag, tag_len ) != 0 )
+        {
             ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
+            goto exit;
+        }
     }
 #endif /* MBEDTLS_CHACHAPOLY_C */
 
+exit:
     mbedtls_platform_zeroize( check_tag, tag_len );
     return( ret );
 }