From 5fbc5b5a3cf1e766f957c454d297913ae39118af Mon Sep 17 00:00:00 2001
From: Conrad Meyer <cem@FreeBSD.org>
Date: Wed, 21 Mar 2018 16:12:07 +0000
Subject: [PATCH] cryptosoft(4): Zero plain hash contexts, too

An OCF-naive user program could use these primitives to implement HMAC, for
example.  This would make the freed context sensitive data.

Probably other bzeros in this file should be explicit_bzeros as well.
Future work.

Reviewed by:	jhb, markj
Differential Revision:	https://reviews.freebsd.org/D14662 (minor part of a larger work)
---
 sys/opencrypto/cryptosoft.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sys/opencrypto/cryptosoft.c b/sys/opencrypto/cryptosoft.c
index 45897990a865..1b359c8322c6 100644
--- a/sys/opencrypto/cryptosoft.c
+++ b/sys/opencrypto/cryptosoft.c
@@ -1053,8 +1053,10 @@ swcr_freesession_locked(device_t dev, u_int64_t tid)
 		case CRYPTO_SHA1:
 			axf = swd->sw_axf;
 
-			if (swd->sw_ictx)
+			if (swd->sw_ictx) {
+				explicit_bzero(swd->sw_ictx, axf->ctxsize);
 				free(swd->sw_ictx, M_CRYPTO_DATA);
+			}
 			break;
 
 		case CRYPTO_DEFLATE_COMP: