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SubjectRe: [PATCH] crypto: caam: blob_gen.c: warn if key is insecure
On Fri, 4 Nov 2022, Ahmad Fatoum wrote:

> Hello Nikolaus,
>
> On 19.10.22 14:44, Nikolaus Voss wrote:
>> 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.
>
> Thanks for your patch.
>
>> Signed-off-by: Nikolaus Voss <nikolaus.voss@haag-streit.com>
>> ---
>> drivers/crypto/caam/blob_gen.c | 8 ++++++++
>> drivers/crypto/caam/regs.h | 3 +++
>> 2 files changed, 11 insertions(+)
>>
>> diff --git a/drivers/crypto/caam/blob_gen.c b/drivers/crypto/caam/blob_gen.c
>> index 6345c7269eb0..f3e741393f65 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>
>>
>> @@ -62,11 +63,13 @@ int caam_process_blob(struct caam_blob_priv *priv,
>> struct caam_blob_info *info, bool encap)
>
> I agree with Herbert that this may not be the best place. I think
> a single warning during caam_blob_gen_init() would suffice.
>
>> {
>> struct caam_blob_job_result testres;
>> + const struct caam_drv_private *ctrlpriv;
>> 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 +103,11 @@ int caam_process_blob(struct caam_blob_priv *priv,
>> goto out_unmap_in;
>> }
>>
>> + ctrlpriv = dev_get_drvdata(jrdev->parent);
>> + moo = FIELD_GET(CSTA_MOO, ctrlpriv->ctrl->perfmon.status);
>> + if (moo != CSTA_MOO_SECURE && moo != CSTA_MOO_TRUSTED)
>> + dev_warn(jrdev, "using insecure test key!\n");
>
> I'd make the warning a bit more verbose, e.g.
>
> "device not configured for trusted/secure mode: using insecure test key!"

I agree.

>
>> +
>> /*
>> * 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 66d6dad841bb..b7de5fb5e056 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 3
>
> I just checked the i.MX6 and LS1046 security reference manuals and both
> have Trusted as 2 (10b). 3 is fail. Does you SoC differ? Either way, please
> note what SoC you were testing on in the commit message.

You're right, I will correct that.

Niko

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