Clean up ndef_{prefix,suffix}_free()

These functions are rather similar, so there's no need for the code to
be wildly different. Add a missing NULL check to ndef_prefix_free() since
that will be needed in a subsequent commit.

ok jsing

1 files changed, 13 insertions, 8 deletions

diff --git a/src/lib/libcrypto/asn1/bio_ndef.c b/src/lib/libcrypto/asn1/bio_ndef.c
index 88b204e8aa..6266d68bbd 100644
--- a/src/lib/libcrypto/asn1/bio_ndef.c
+++ b/src/lib/libcrypto/asn1/bio_ndef.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bio_ndef.c,v 1.11 2021/12/25 13:17:48 jsing Exp $ */
+/* $OpenBSD: bio_ndef.c,v 1.12 2023/03/06 19:10:14 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project.
  */
@@ -178,29 +178,34 @@ ndef_prefix(BIO *b, unsigned char **pbuf, int *plen, void *parg)
 static int
 ndef_prefix_free(BIO *b, unsigned char **pbuf, int *plen, void *parg)
 {
-        NDEF_SUPPORT *ndef_aux;
+        NDEF_SUPPORT **pndef_aux = parg;
 
-        if (!parg)
+        if (pndef_aux == NULL || *pndef_aux == NULL)
                 return 0;
 
-        ndef_aux = *(NDEF_SUPPORT **)parg;
+        free((*pndef_aux)->derbuf);
+        (*pndef_aux)->derbuf = NULL;
 
-        free(ndef_aux->derbuf);
-
-        ndef_aux->derbuf = NULL;
         *pbuf = NULL;
         *plen = 0;
+
         return 1;
 }
 
 static int
 ndef_suffix_free(BIO *b, unsigned char **pbuf, int *plen, void *parg)
 {
-        NDEF_SUPPORT **pndef_aux = (NDEF_SUPPORT **)parg;
+        NDEF_SUPPORT **pndef_aux = parg;
+
+        /* Ensure ndef_prefix_free() won't fail, so we won't leak *pndef_aux. */
+        if (pndef_aux == NULL || *pndef_aux == NULL)
+                return 0;
         if (!ndef_prefix_free(b, pbuf, plen, parg))
                 return 0;
+
         free(*pndef_aux);
         *pndef_aux = NULL;
+
         return 1;
 }