From: Richard Levitte <levitte@openssl.org>
Date: Mon, 27 Oct 2025 19:47:44 +0000 (+0100)
Subject: Set the 'tmp' flag BN_FLG_FIXED_TOP in bn_mod_exp_mont_fixed_top()
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=54681f6e5b689299bada4363adc2edc46a1d67b4;p=thirdparty%2Fopenssl.git

Set the 'tmp' flag BN_FLG_FIXED_TOP in bn_mod_exp_mont_fixed_top()

If not set, bn_check_top() trips when BN_DEBUG is defined

Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28801)
---

diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 1dda2e017f1..ae6d9a21005 100644
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -766,6 +766,7 @@ int bn_mod_exp_mont_fixed_top(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
         for (i = 1; i < top; i++)
             tmp.d[i] = (~m->d[i]) & BN_MASK2;
         tmp.top = top;
+        tmp.flags |= BN_FLG_FIXED_TOP;
     } else
 #endif
     if (!bn_to_mont_fixed_top(&tmp, BN_value_one(), mont, ctx))