Make BN_num_bits() independent of bn->top.

Provide bn_bitsize(), which performs a constant time scan of a BN in order
to determine the bit size of the BN value. Use this for BN_num_bits() such
that it is no longer dependent on the bn->top value.

ok tb@

1 files changed, 5 insertions, 1 deletions

diff --git a/src/lib/libcrypto/bn/bn_internal.h b/src/lib/libcrypto/bn/bn_internal.h
index 5f86e21330..f5c69c5d77 100644
--- a/src/lib/libcrypto/bn/bn_internal.h
+++ b/src/lib/libcrypto/bn/bn_internal.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bn_internal.h,v 1.12 2023/06/12 16:17:24 jsing Exp $ */
+/*      $OpenBSD: bn_internal.h,v 1.13 2023/06/21 07:41:55 jsing Exp $ */
 /*
  * Copyright (c) 2023 Joel Sing <jsing@openbsd.org>
  *
@@ -22,6 +22,10 @@
 #ifndef HEADER_BN_INTERNAL_H
 #define HEADER_BN_INTERNAL_H
 
+int bn_word_clz(BN_ULONG w);
+
+int bn_bitsize(const BIGNUM *bn);
+
 #ifndef HAVE_BN_CT_NE_ZERO
 static inline int
 bn_ct_ne_zero(BN_ULONG w)