From e680fe5b2098d1406fab3bb3994254f026651090 Mon Sep 17 00:00:00 2001
From: tb <>
Date: Thu, 3 Aug 2023 18:53:56 +0000
Subject: Make the bn_rand_interval() API a bit more ergonomic

Provide bn_rand_in_range() which is a slightly tweaked version of what was
previously called bn_rand_range().

The way bn_rand_range() is called in libcrypto, the lower bound is always
expressible as a word. In fact, most of the time it is 1, the DH code uses
a 2, the MR tests in BPSW use 3 and an exceptinally high number appears in
the Tonelli-Shanks implementation where we use 32. Converting these lower
bounds to BIGNUMs on the call site is annoying so let bn_rand_interval()
do that internally and route that through bn_rand_in_range(). This way we
can avoid using BN_sub_word().

Adjust the bn_isqrt() test to use bn_rand_in_range() since that's the
only caller that uses actual BIGNUMs as lower bounds.

ok jsing
---
 src/lib/libcrypto/dsa/dsa_ossl.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'src/lib/libcrypto/dsa/dsa_ossl.c')

diff --git a/src/lib/libcrypto/dsa/dsa_ossl.c b/src/lib/libcrypto/dsa/dsa_ossl.c
index 36b2a63462..b92d0b8cee 100644
--- a/src/lib/libcrypto/dsa/dsa_ossl.c
+++ b/src/lib/libcrypto/dsa/dsa_ossl.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: dsa_ossl.c,v 1.52 2023/07/08 14:28:15 beck Exp $ */
+/* $OpenBSD: dsa_ossl.c,v 1.53 2023/08/03 18:53:55 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -172,7 +172,7 @@ dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 	 *
 	 * Where b is a random value in the range [1, q).
 	 */
-	if (!bn_rand_interval(b, BN_value_one(), dsa->q))
+	if (!bn_rand_interval(b, 1, dsa->q))
 		goto err;
 	if (BN_mod_inverse_ct(binv, b, dsa->q, ctx) == NULL)
 		goto err;
@@ -261,7 +261,7 @@ dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
 	    !BN_set_bit(m, q_bits))
 		goto err;
 
-	if (!bn_rand_interval(k, BN_value_one(), dsa->q))
+	if (!bn_rand_interval(k, 1, dsa->q))
 		goto err;
 
 	BN_set_flags(k, BN_FLG_CONSTTIME);
-- 
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