commit a8653208ec76d228e889082d5c5e6ce781cdcd8d
author David Benjamin <davidben@chromium.org> Sun Jun 28 01:26:10 2015 -0400
committer Adam Langley <agl@google.com> Wed Jul 01 19:45:43 2015 +0000
tree 042c5519983b5e7fd8141e0249423b243fcabcb1
parent d63307199a9bc39fe86ec46a131d60c694af41f3

Add CBB_zero to set a CBB to the zero state.

One tedious thing about using CBB is that you can't safely CBB_cleanup
until CBB_init is successful, which breaks the general 'goto err' style
of cleanup. This makes it possible:

  CBB_zero ~ EVP_MD_CTX_init
  CBB_init ~ EVP_DigestInit
  CBB_cleanup ~ EVP_MD_CTX_cleanup

Change-Id: I085ecc4405715368886dc4de02285a47e7fc4c52
Reviewed-on: https://boringssl-review.googlesource.com/5267
Reviewed-by: Adam Langley <agl@google.com>

ssl/s3_clnt.c

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 1d9b164..b5c35f0 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1963,19 +1963,16 @@
       uint8_t *new_pms;
       size_t new_pms_len;
 
-      if (!CBB_init(&cbb, 2 + psk_len + 2 + pms_len)) {
-        OPENSSL_PUT_ERROR(SSL, ssl3_send_client_key_exchange,
-                          ERR_R_MALLOC_FAILURE);
-        goto err;
-      }
-      if (!CBB_add_u16_length_prefixed(&cbb, &child) ||
+      CBB_zero(&cbb);
+      if (!CBB_init(&cbb, 2 + psk_len + 2 + pms_len) ||
+          !CBB_add_u16_length_prefixed(&cbb, &child) ||
           !CBB_add_bytes(&child, pms, pms_len) ||
           !CBB_add_u16_length_prefixed(&cbb, &child) ||
           !CBB_add_bytes(&child, psk, psk_len) ||
           !CBB_finish(&cbb, &new_pms, &new_pms_len)) {
         CBB_cleanup(&cbb);
         OPENSSL_PUT_ERROR(SSL, ssl3_send_client_key_exchange,
-                          ERR_R_INTERNAL_ERROR);
+                          ERR_R_MALLOC_FAILURE);
         goto err;
       }
       OPENSSL_cleanse(pms, pms_len);