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From:   Stephan =?ISO-8859-1?Q?M=FCller?= <smueller@chronox.de>
To:     herbert@gondor.apana.org.au
Cc:     linux-crypto@vger.kernel.org,
        Marcelo Cerri <marcelo.cerri@canonical.com>,
        Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
        ard.biesheuvel@linaro.org, nhorman@redhat.com, simo@redhat.com
Subject: [PATCH v2 4/5] crypto: DH SP800-56A rev 3 local public key validation
Date:   Sun, 12 Jul 2020 18:40:57 +0200
Message-ID: <2833634.e9J7NaK4W3@positron.chronox.de>
In-Reply-To: <5722559.lOV4Wx5bFT@positron.chronox.de>
References: <2543601.mvXUDI8C0e@positron.chronox.de> <5722559.lOV4Wx5bFT@positron.chronox.de>
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Sender: linux-crypto-owner@vger.kernel.org
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After the generation of a local public key, SP800-56A rev 3 section
5.6.2.1.3 mandates a validation of that key with a full validation
compliant to section 5.6.2.3.1.

Only if the full validation passes, the key is allowed to be used.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 crypto/dh.c | 59 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 25 deletions(-)

diff --git a/crypto/dh.c b/crypto/dh.c
index f84fd50ec79b..cd4f32092e5c 100644
--- a/crypto/dh.c
+++ b/crypto/dh.c
@@ -180,32 +180,41 @@ static int dh_compute_value(struct kpp_request *req)
 	if (ret)
 		goto err_free_base;
 
-	/* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */
-	if (fips_enabled && req->src) {
-		MPI pone;
-
-		/* z <= 1 */
-		if (mpi_cmp_ui(val, 1) < 1) {
-			ret = -EBADMSG;
-			goto err_free_base;
-		}
-
-		/* z == p - 1 */
-		pone = mpi_alloc(0);
-
-		if (!pone) {
-			ret = -ENOMEM;
-			goto err_free_base;
+	if (fips_enabled) {
+		/* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */
+		if (req->src) {
+			MPI pone;
+
+			/* z <= 1 */
+			if (mpi_cmp_ui(val, 1) < 1) {
+				ret = -EBADMSG;
+				goto err_free_base;
+			}
+
+			/* z == p - 1 */
+			pone = mpi_alloc(0);
+
+			if (!pone) {
+				ret = -ENOMEM;
+				goto err_free_base;
+			}
+
+			ret = mpi_sub_ui(pone, ctx->p, 1);
+			if (!ret && !mpi_cmp(pone, val))
+				ret = -EBADMSG;
+
+			mpi_free(pone);
+
+			if (ret)
+				goto err_free_base;
+
+		/* SP800-56A rev 3 5.6.2.1.3 key check */
+		} else {
+			if (dh_is_pubkey_valid(ctx, val)) {
+				ret = -EAGAIN;
+				goto err_free_val;
+			}
 		}
-
-		ret = mpi_sub_ui(pone, ctx->p, 1);
-		if (!ret && !mpi_cmp(pone, val))
-			ret = -EBADMSG;
-
-		mpi_free(pone);
-
-		if (ret)
-			goto err_free_base;
 	}
 
 	ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
-- 
2.26.2