linux-kernel - [PATCH 1/2] crypto: ecdh - zeroize crpytographic keys after use

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Date: Thu, 11 Apr 2024 23:51:56 +0000
From: Hailey Mothershead <hailmo@...zon.com>
To: <herbert@...dor.apana.org.au>
CC: <davem@...emloft.net>, <linux-crypto@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <hailmo@...zon.com>
Subject: [PATCH 1/2] crypto: ecdh - zeroize crpytographic keys after use

Fips 140-3 specifies that Sensitive Security Parameters (SSPs) must be
zeroized after use and that overwriting these variables with a new SSP
is not sufficient for zeroization. So explicitly zeroize the private key
before it is overwritten in ecdh_set_secret.

It also requires that variables used in the creation of SSPs
be zeroized once they are no longer in use. Zeroize the public key as it
is used in the creation of the shared secret.

Signed-off-by: Hailey Mothershead <hailmo@...zon.com>
---
 crypto/ecdh.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/crypto/ecdh.c b/crypto/ecdh.c
index 80afee3234fb..71599cadf0bc 100644
--- a/crypto/ecdh.c
+++ b/crypto/ecdh.c
@@ -33,6 +33,8 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 	    params.key_size > sizeof(u64) * ctx->ndigits)
 		return -EINVAL;
 
+	memset(ctx->private_key, 0, sizeof(ctx->private_key));
+
 	if (!params.key || !params.key_size)
 		return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
 				       ctx->private_key);
@@ -111,7 +113,7 @@ static int ecdh_compute_value(struct kpp_request *req)
 free_all:
 	kfree_sensitive(shared_secret);
 free_pubkey:
-	kfree(public_key);
+	kfree_sensitive(public_key);
 	return ret;
 }
 
-- 
2.40.1