linux-kernel - Re: [PATCH v3 4/4] powerpc: load firmware trusted keys/hashes into kernel keyring

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Date:   Tue, 03 Sep 2019 18:54:51 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Nayna Jain <nayna@...ux.ibm.com>, linuxppc-dev@...abs.org,
        linux-efi@...r.kernel.org, linux-integrity@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Jeremy Kerr <jk@...abs.org>,
        Matthew Garret <matthew.garret@...ula.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        George Wilson <gcwilson@...ux.ibm.com>,
        Elaine Palmer <erpalmer@...ibm.com>,
        Eric Ricther <erichte@...ux.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>
Subject: Re: [PATCH v3 4/4] powerpc: load firmware trusted keys/hashes into
 kernel keyring

On Mon, 2019-08-26 at 09:23 -0400, Nayna Jain wrote:
> The keys used to verify the Host OS kernel are managed by firmware as
> secure variables. This patch loads the verification keys into the .platform
> keyring and revocation hashes into .blacklist keyring. This enables
> verification and loading of the kernels signed by the boot time keys which
> are trusted by firmware.
> 
> Signed-off-by: Nayna Jain <nayna@...ux.ibm.com>

Feel free to add my tag after addressing the formatting issues.

Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>

> diff --git a/security/integrity/platform_certs/load_powerpc.c b/security/integrity/platform_certs/load_powerpc.c
> new file mode 100644
> index 000000000000..359d5063d4da
> --- /dev/null
> +++ b/security/integrity/platform_certs/load_powerpc.c
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain <nayna@...ux.ibm.com>
> + *
> + *      - loads keys and hashes stored and controlled by the firmware.
> + */
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/cred.h>
> +#include <linux/err.h>
> +#include <linux/slab.h>
> +#include <asm/secboot.h>
> +#include <asm/secvar.h>
> +#include "keyring_handler.h"
> +
> +/*
> + * Get a certificate list blob from the named secure variable.
> + */
> +static __init void *get_cert_list(u8 *key, unsigned long keylen, uint64_t *size)
> +{
> +	int rc;
> +	void *db;
> +
> +	rc = secvar_ops->get(key, keylen, NULL, size);
> +	if (rc) {
> +		pr_err("Couldn't get size: %d\n", rc);
> +		return NULL;
> +	}
> +
> +	db = kmalloc(*size, GFP_KERNEL);
> +	if (!db)
> +		return NULL;
> +
> +	rc = secvar_ops->get(key, keylen, db, size);
> +	if (rc) {
> +		kfree(db);
> +		pr_err("Error reading db var: %d\n", rc);
> +		return NULL;
> +	}
> +
> +	return db;
> +}
> +
> +/*
> + * Load the certs contained in the keys databases into the platform trusted
> + * keyring and the blacklisted X.509 cert SHA256 hashes into the blacklist
> + * keyring.
> + */
> +static int __init load_powerpc_certs(void)
> +{
> +	void *db = NULL, *dbx = NULL;
> +	uint64_t dbsize = 0, dbxsize = 0;
> +	int rc = 0;
> +
> +	if (!secvar_ops)
> +		return -ENODEV;
> +
> +	/* Get db, and dbx.  They might not exist, so it isn't
> +	 * an error if we can't get them.
> +	 */
> +	db = get_cert_list("db", 3, &dbsize);
> +	if (!db) {
> +		pr_err("Couldn't get db list from firmware\n");
> +	} else {
> +		rc = parse_efi_signature_list("powerpc:db",
> +				db, dbsize, get_handler_for_db);
> +		if (rc)
> +			pr_err("Couldn't parse db signatures: %d\n",
> +					rc);

There's no need to split this line.

> +		kfree(db);
> +	}
> +
> +	dbx = get_cert_list("dbx", 3,  &dbxsize);
> +	if (!dbx) {
> +		pr_info("Couldn't get dbx list from firmware\n");
> +	} else {
> +		rc = parse_efi_signature_list("powerpc:dbx",
> +				dbx, dbxsize,
> +				get_handler_for_dbx);

Formatting of this line is off.

> +		if (rc)
> +			pr_err("Couldn't parse dbx signatures: %d\n", rc);
> +		kfree(dbx);
> +	}
> +
> +	return rc;
> +}
> +late_initcall(load_powerpc_certs);