Prevent double free in int_TS_RESP_verify_token

If TS_compute_imprint fails after md_alg was allocated, there will be a
double free in its caller. Obvious fix is to null out the output
parameter md_alg just like it's already done for imprint and imprint_len.

From Pauli Dale, OpenSSL 1.1.1, a3dea76f742896b7d75a0c0529c0af1e628bd853

ok inoguchi jsing

1 files changed, 2 insertions, 1 deletions

diff --git a/src/lib/libcrypto/ts/ts_rsp_verify.c b/src/lib/libcrypto/ts/ts_rsp_verify.c
index 36ead0671a..27515adf68 100644
--- a/src/lib/libcrypto/ts/ts_rsp_verify.c
+++ b/src/lib/libcrypto/ts/ts_rsp_verify.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ts_rsp_verify.c,v 1.18 2017/01/29 17:49:23 beck Exp $ */
+/* $OpenBSD: ts_rsp_verify.c,v 1.19 2021/05/01 13:13:45 tb Exp $ */
 /* Written by Zoltan Glozik (zglozik@stones.com) for the OpenSSL
  * project 2002.
  */
@@ -639,6 +639,7 @@ TS_compute_imprint(BIO *data, TS_TST_INFO *tst_info, X509_ALGOR **md_alg,
 
 err:
         X509_ALGOR_free(*md_alg);
+        *md_alg = NULL;
         free(*imprint);
         *imprint = NULL;
         *imprint_len = 0;