From: Matt Caswell <matt@openssl.org>
Date: Mon, 30 Apr 2018 14:05:45 +0000 (+0100)
Subject: Clarify BN_mod_exp docs
X-Git-Tag: OpenSSL_1_1_1-pre7~124
X-Git-Url: https://git.openssl.org/?p=openssl.git;a=commitdiff_plain;h=3a070e255f412dcc8cb4b6d7ebcdd2c4ab0927b1

Clarify BN_mod_exp docs

Specifically this is not supported with an even modulus and
BN_FLG_CONSTTIME.

Fixes #5082

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6137)
---

diff --git a/doc/man3/BN_add.pod b/doc/man3/BN_add.pod
index 98f2970a97..88a0117970 100644
--- a/doc/man3/BN_add.pod
+++ b/doc/man3/BN_add.pod
@@ -92,7 +92,9 @@ BN_exp() raises I<a> to the I<p>-th power and places the result in I<r>
 BN_mul().
 
 BN_mod_exp() computes I<a> to the I<p>-th power modulo I<m> (C<r=a^p %
-m>). This function uses less time and space than BN_exp().
+m>). This function uses less time and space than BN_exp(). Do not call this
+function when B<m> is even and any of the parameters have the
+B<BN_FLG_CONSTTIME> flag set.
 
 BN_gcd() computes the greatest common divisor of I<a> and I<b> and
 places the result in I<r>. I<r> may be the same B<BIGNUM> as I<a> or