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

1 files changed, 2 insertions, 2 deletions

diff --git a/src/lib/libcrypto/ec/ecp_smpl.c b/src/lib/libcrypto/ec/ecp_smpl.c
index de1f9a3472..018aedfd4e 100644
--- a/src/lib/libcrypto/ec/ecp_smpl.c
+++ b/src/lib/libcrypto/ec/ecp_smpl.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ecp_smpl.c,v 1.55 2023/07/26 17:15:25 tb Exp $ */
+/* $OpenBSD: ecp_smpl.c,v 1.56 2023/08/03 18:53:56 tb Exp $ */
 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
  * for the OpenSSL project.
  * Includes code written by Bodo Moeller for the OpenSSL project.
@@ -1227,7 +1227,7 @@ ec_GFp_simple_blind_coordinates(const EC_GROUP *group, EC_POINT *p, BN_CTX *ctx)
                 goto err;
 
         /* Generate lambda in [1, group->field). */
-        if (!bn_rand_interval(lambda, BN_value_one(), &group->field))
+        if (!bn_rand_interval(lambda, 1, &group->field))
                 goto err;
 
         if (group->meth->field_encode != NULL &&