commit 95e4bbcf6cd91158b4eb17eed364f5bc20ab9f0a
author Hanno Becker <hanno.becker@arm.com> Thu May 09 11:38:24 2019 +0100
committer Hanno Becker <hanno.becker@arm.com> Mon Jun 03 14:47:36 2019 +0100
tree dd0d13061f2c3427ee0c980bdb995303287fb49b
parent af05ac067b6689566f69c87493283622a5dafd6b

Fix additional data calculation if CID is disabled

In contrast to other aspects of the Connection ID extension,
the CID-based additional data for MAC computations differs from
the non-CID case even if the CID length is 0, because it
includes the CID length.

library/ssl_tls.c

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index c111e94..d139489 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2069,16 +2069,21 @@
     memcpy( add_data + 9, rec->ver, sizeof( rec->ver ) );
 
 #if defined(MBEDTLS_SSL_CID)
-    memcpy( add_data + 11, rec->cid, rec->cid_len );
-    add_data[11 + rec->cid_len + 0] = rec->cid_len;
-    add_data[11 + rec->cid_len + 1] = ( rec->data_len >> 8 ) & 0xFF;
-    add_data[11 + rec->cid_len + 2] = ( rec->data_len >> 0 ) & 0xFF;
-    *add_data_len = 13 + 1 + rec->cid_len;
-#else /* MBEDTLS_SSL_CID */
-    add_data[11 + 0] = ( rec->data_len >> 8 ) & 0xFF;
-    add_data[11 + 1] = ( rec->data_len >> 0 ) & 0xFF;
-    *add_data_len = 13;
+    if( rec->cid_len != 0 )
+    {
+        memcpy( add_data + 11, rec->cid, rec->cid_len );
+        add_data[11 + rec->cid_len + 0] = rec->cid_len;
+        add_data[11 + rec->cid_len + 1] = ( rec->data_len >> 8 ) & 0xFF;
+        add_data[11 + rec->cid_len + 2] = ( rec->data_len >> 0 ) & 0xFF;
+        *add_data_len = 13 + 1 + rec->cid_len;
+    }
+    else
 #endif /* MBEDTLS_SSL_CID */
+    {
+        add_data[11 + 0] = ( rec->data_len >> 8 ) & 0xFF;
+        add_data[11 + 1] = ( rec->data_len >> 0 ) & 0xFF;
+        *add_data_len = 13;
+    }
 }
 
 int mbedtls_ssl_encrypt_buf( mbedtls_ssl_context *ssl,