From 22e9d4df59dc9b4792b5eb914b97092ddfae8096 Mon Sep 17 00:00:00 2001
From: tb <>
Date: Mon, 5 Nov 2018 23:52:47 +0000
Subject: Introduce bn_rand_interval() that allows specifying an interval [a,
 b) from which a a BIGNUM is chosen uniformly at random.

ok beck jsing
---
 src/lib/libcrypto/bn/bn_lcl.h  |  3 ++-
 src/lib/libcrypto/bn/bn_rand.c | 29 ++++++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

(limited to 'src/lib')

diff --git a/src/lib/libcrypto/bn/bn_lcl.h b/src/lib/libcrypto/bn/bn_lcl.h
index b8319dd700..d0f36822dc 100644
--- a/src/lib/libcrypto/bn/bn_lcl.h
+++ b/src/lib/libcrypto/bn/bn_lcl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_lcl.h,v 1.29 2018/07/23 18:14:32 tb Exp $ */
+/* $OpenBSD: bn_lcl.h,v 1.30 2018/11/05 23:52:47 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -583,6 +583,7 @@ BN_ULONG bn_add_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp, int
 BN_ULONG bn_sub_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp, int num);
 
 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom);
+int bn_rand_interval(BIGNUM *rnd, const BIGNUM *lower_inc, const BIGNUM *upper_exc);
 
 /* Explicitly const time / non-const time versions for internal use */
 int BN_mod_exp_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
diff --git a/src/lib/libcrypto/bn/bn_rand.c b/src/lib/libcrypto/bn/bn_rand.c
index 8625757140..63b8af8b95 100644
--- a/src/lib/libcrypto/bn/bn_rand.c
+++ b/src/lib/libcrypto/bn/bn_rand.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_rand.c,v 1.20 2017/05/02 03:59:44 deraadt Exp $ */
+/* $OpenBSD: bn_rand.c,v 1.21 2018/11/05 23:52:47 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -279,6 +279,33 @@ BN_rand_range(BIGNUM *r, const BIGNUM *range)
 	return bn_rand_range(0, r, range);
 }
 
+int
+bn_rand_interval(BIGNUM *rnd, const BIGNUM *lower_inc, const BIGNUM *upper_exc)
+{
+	BIGNUM *len = NULL;
+	int ret = 0;
+
+	if (BN_cmp(lower_inc, upper_exc) <= 0)
+		goto err;
+
+	if ((len = BN_new()) == NULL)
+		goto err;
+
+	if (!BN_sub(len, upper_exc, lower_inc))
+		goto err;
+
+	if (!bn_rand_range(0, rnd, len))
+		goto err;
+
+	if (!BN_add(rnd, rnd, lower_inc))
+		goto err;
+
+	ret = 1;
+ err:
+	BN_free(len);
+	return ret;
+}
+
 int
 BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
 {
-- 
cgit v1.2.3-55-g6feb