From dcb8eaa9ef5f6301ba59d0727dce04ed726d84b8 Mon Sep 17 00:00:00 2001
From: jsing <jsing@openbsd.org>
Date: Wed, 30 Nov 2022 03:08:39 +0000
Subject: [PATCH] Rewrite bn_correct_top().

bn_correct_top() is currently a macro and far more complex than it needs
to be - rewrite it as a function.

ok tb@
---
 lib/libcrypto/bn/bn_lib.c   |  9 ++++++++-
 lib/libcrypto/bn/bn_local.h | 15 ++-------------
 2 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/lib/libcrypto/bn/bn_lib.c b/lib/libcrypto/bn/bn_lib.c
index df43da5db66..851c337ef0a 100644
--- a/lib/libcrypto/bn/bn_lib.c
+++ b/lib/libcrypto/bn/bn_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_lib.c,v 1.65 2022/11/30 02:52:25 jsing Exp $ */
+/* $OpenBSD: bn_lib.c,v 1.66 2022/11/30 03:08:39 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -253,6 +253,13 @@ BN_num_bits(const BIGNUM *a)
 	return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
 }
 
+void
+bn_correct_top(BIGNUM *a)
+{
+	while (a->top > 0 && a->d[a->top - 1] == 0)
+		a->top--;
+}
+
 /* The caller MUST check that words > b->dmax before calling this */
 static BN_ULONG *
 bn_expand_internal(const BIGNUM *b, int words)
diff --git a/lib/libcrypto/bn/bn_local.h b/lib/libcrypto/bn/bn_local.h
index 7bddcb21b92..48d24c5a27c 100644
--- a/lib/libcrypto/bn/bn_local.h
+++ b/lib/libcrypto/bn/bn_local.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_local.h,v 1.2 2022/11/26 17:23:17 tb Exp $ */
+/* $OpenBSD: bn_local.h,v 1.3 2022/11/30 03:08:39 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -509,21 +509,10 @@ BN_ULONG bn_sub_part_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b,
     int cl, int dl);
 int bn_mul_mont(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp, const BN_ULONG *np, const BN_ULONG *n0, int num);
 
+void bn_correct_top(BIGNUM *a);
 int bn_expand(BIGNUM *a, int bits);
 int bn_wexpand(BIGNUM *a, int words);
 
-#define bn_correct_top(a) \
-        { \
-        BN_ULONG *ftl; \
-	int tmp_top = (a)->top; \
-	if (tmp_top > 0) \
-		{ \
-		for (ftl= &((a)->d[tmp_top-1]); tmp_top > 0; tmp_top--) \
-			if (*(ftl--)) break; \
-		(a)->top = tmp_top; \
-		} \
-	}
-
 BN_ULONG bn_mul_add_words(BN_ULONG *rp, const BN_ULONG *ap, int num, BN_ULONG w);
 BN_ULONG bn_mul_words(BN_ULONG *rp, const BN_ULONG *ap, int num, BN_ULONG w);
 void     bn_sqr_words(BN_ULONG *rp, const BN_ULONG *ap, int num);
-- 
2.20.1