inspired by a cloudflare diff, cleanse old memory when expanding a bignum.

however, instead of trying to audit all the places where a secret bignum
is used, apply the big hammer and clear all bignums when freed.
ok deraadt miod

1 files changed, 9 insertions, 17 deletions

diff --git a/lib/libssl/src/crypto/bn/bn_lib.c b/lib/libssl/src/crypto/bn/bn_lib.c
index 9787a31dbbf..a8022f66680 100644
--- a/lib/libssl/src/crypto/bn/bn_lib.c
+++ b/lib/libssl/src/crypto/bn/bn_lib.c
@@ -226,22 +226,11 @@ void BN_clear_free(BIGNUM *a)
 		free(a);
 	}
 
-void BN_free(BIGNUM *a)
-	{
-	if (a == NULL) return;
-	bn_check_top(a);
-	if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))
-		free(a->d);
-	if (a->flags & BN_FLG_MALLOCED)
-		free(a);
-	else
-		{
-#ifndef OPENSSL_NO_DEPRECATED
-		a->flags|=BN_FLG_FREE;
-#endif
-		a->d = NULL;
-		}
-	}
+void
+BN_free(BIGNUM *a)
+{
+	BN_clear_free(a);
+}
 
 void BN_init(BIGNUM *a)
 	{
@@ -400,7 +389,10 @@ BIGNUM *bn_expand2(BIGNUM *b, int words)
 		{
 		BN_ULONG *a = bn_expand_internal(b, words);
 		if(!a) return NULL;
-		if(b->d) free(b->d);
+		if(b->d) {
+			OPENSSL_cleanse(b->d, b->dmax * sizeof(b->d[0]));
+			free(b->d);
+		}
 		b->d=a;
 		b->dmax=words;
 		}