linux-kernel - [PATCH v3] crypto: caam: blob_gen.c: warn if key is insecure

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Message-Id: <20221121141929.2E36427E9@mail.steuer-voss.de>
Date:   Mon, 21 Nov 2022 15:12:41 +0100
From:   Nikolaus Voss <nikolaus.voss@...g-streit.com>
To:     "Horia Geanta" <horia.geanta@....com>,
        Pankaj Gupta <pankaj.gupta@....com>,
        Gaurav Jain <gaurav.jain@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>,
        David Gstir <david@...ma-star.at>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Nikolaus Voss <nv@...n.de>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3] crypto: caam: blob_gen.c: warn if key is insecure

If CAAM is not in "trusted" or "secure" state, a fixed non-volatile key
is used instead of the unique device key. This is the default mode of
operation without secure boot (HAB). In this scenario, CAAM encrypted
blobs should be used only for testing but not in a production
environment, so issue a warning.

Signed-off-by: Nikolaus Voss <nikolaus.voss@...g-streit.com>

---
CHANGES
=======
v2: make warning more verbose, correct register, style fixes
v3: fix sparse warning "dereference of noderef expression"
    by using ioread32() to dereference iomem pointer

 drivers/crypto/caam/blob_gen.c | 9 +++++++++
 drivers/crypto/caam/regs.h     | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/drivers/crypto/caam/blob_gen.c b/drivers/crypto/caam/blob_gen.c
index 6345c7269eb03..1f65df4898478 100644
--- a/drivers/crypto/caam/blob_gen.c
+++ b/drivers/crypto/caam/blob_gen.c
@@ -6,6 +6,7 @@
 
 #define pr_fmt(fmt) "caam blob_gen: " fmt
 
+#include <linux/bitfield.h>
 #include <linux/device.h>
 #include <soc/fsl/caam-blob.h>
 
@@ -61,12 +62,14 @@ static void caam_blob_job_done(struct device *dev, u32 *desc, u32 err, void *con
 int caam_process_blob(struct caam_blob_priv *priv,
 		      struct caam_blob_info *info, bool encap)
 {
+	const struct caam_drv_private *ctrlpriv;
 	struct caam_blob_job_result testres;
 	struct device *jrdev = &priv->jrdev;
 	dma_addr_t dma_in, dma_out;
 	int op = OP_PCLID_BLOB;
 	size_t output_len;
 	u32 *desc;
+	u32 moo;
 	int ret;
 
 	if (info->key_mod_len > CAAM_BLOB_KEYMOD_LENGTH)
@@ -100,6 +103,12 @@ int caam_process_blob(struct caam_blob_priv *priv,
 		goto out_unmap_in;
 	}
 
+	ctrlpriv = dev_get_drvdata(jrdev->parent);
+	moo = FIELD_GET(CSTA_MOO, ioread32(&ctrlpriv->ctrl->perfmon.status));
+	if (moo != CSTA_MOO_SECURE && moo != CSTA_MOO_TRUSTED)
+		dev_warn(jrdev,
+			 "using insecure test key, enable HAB to use unique device key!\n");
+
 	/*
 	 * A data blob is encrypted using a blob key (BK); a random number.
 	 * The BK is used as an AES-CCM key. The initial block (B0) and the
diff --git a/drivers/crypto/caam/regs.h b/drivers/crypto/caam/regs.h
index 66d6dad841bb2..66928f8a0c4b1 100644
--- a/drivers/crypto/caam/regs.h
+++ b/drivers/crypto/caam/regs.h
@@ -426,6 +426,9 @@ struct caam_perfmon {
 	u32 rsvd2;
 #define CSTA_PLEND		BIT(10)
 #define CSTA_ALT_PLEND		BIT(18)
+#define CSTA_MOO		GENMASK(9, 8)
+#define CSTA_MOO_SECURE	1
+#define CSTA_MOO_TRUSTED	2
 	u32 status;		/* CSTA - CAAM Status */
 	u64 rsvd3;
 
-- 
2.34.1