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, 5 insertions, 5 deletions

diff --git a/src/regress/lib/libcrypto/bn/bn_isqrt.c b/src/regress/lib/libcrypto/bn/bn_isqrt.c
index 2663bb74e9..d8a2d2755f 100644
--- a/src/regress/lib/libcrypto/bn/bn_isqrt.c
+++ b/src/regress/lib/libcrypto/bn/bn_isqrt.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bn_isqrt.c,v 1.3 2023/03/08 06:28:08 tb Exp $ */
+/*      $OpenBSD: bn_isqrt.c,v 1.4 2023/08/03 18:53:56 tb Exp $ */
 /*
  * Copyright (c) 2022 Theo Buehler <tb@openbsd.org>
  *
@@ -194,8 +194,8 @@ isqrt_test(void)
         if (!BN_set_bit(upper, UPPER_BITS))
                 errx(1, "BN_set_bit(upper, %d)", UPPER_BITS);
 
-        if (!bn_rand_interval(n, lower, upper))
-                errx(1, "bn_rand_interval n");
+        if (!bn_rand_in_range(n, lower, upper))
+                errx(1, "bn_rand_in_range n");
 
         /* n_sqr = n^2 */
         if (!BN_sqr(n_sqr, n, ctx))
@@ -246,8 +246,8 @@ isqrt_test(void)
          */
 
         for (i = 0; i < N_TESTS; i++) {
-                if (!bn_rand_interval(testcase, n_sqr, upper))
-                        errx(1, "bn_rand_interval testcase");
+                if (!bn_rand_in_range(testcase, n_sqr, upper))
+                        errx(1, "bn_rand_in_range testcase");
 
                 if (!bn_isqrt(isqrt, &is_perfect_square, testcase, ctx))
                         errx(1, "bn_isqrt testcase");