linux-kernel - Re: [PATCH v8 2/8] powerpc/ima: add support to initialize ima policy rules

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Date:   Sat, 19 Oct 2019 20:16:57 -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>,
        Prakhar Srivastava <prsriva02@...il.com>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
Subject: Re: [PATCH v8 2/8] powerpc/ima: add support to initialize ima
 policy rules

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:

> index 000000000000..65d82ee74ea4
> --- /dev/null
> +++ b/arch/powerpc/kernel/ima_arch.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain
> + */
> +
> +#include <linux/ima.h>
> +#include <asm/secure_boot.h>
> +
> +bool arch_ima_get_secureboot(void)
> +{
> +	return is_ppc_secureboot_enabled();
> +}
> +
> +/*
> + * The "secure_rules" are enabled only on "secureboot" enabled systems.
> + * These rules verify the file signatures against known good values.
> + * The "appraise_type=imasig|modsig" option allows the known good signature
> + * to be stored as an xattr or as an appended signature.

Please add another sentence or two as a separate paragraph with an
explanation why the kernel module rule is conditional (eg. Only verify
the appended kernel module signatures once.)

> + */
> +static const char *const secure_rules[] = {
> +	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
> +#ifndef CONFIG_MODULE_SIG_FORCE
> +	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
> +#endif
> +	NULL
> +};
> +

Mimi