From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nayna Subject: Re: [PATCH v6 3/9] powerpc: add support to initialize ima policy rules Date: Tue, 8 Oct 2019 09:12:09 -0400 Message-ID: <2d4a1890-5fb0-3bef-cd78-8cb75ca73076@linux.vnet.ibm.com> References: <1569594360-7141-1-git-send-email-nayna@linux.ibm.com> <1569594360-7141-4-git-send-email-nayna@linux.ibm.com> <877e5pwa1b.fsf@morokweng.localdomain> <84f057d0-6a0b-d486-0eb6-f1590f32e377@linux.vnet.ibm.com> <1570052950.4421.70.camel@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <1570052950.4421.70.camel@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Mimi Zohar , Thiago Jung Bauermann , Nayna Jain Cc: Mark Rutland , devicetree@vger.kernel.org, linux-efi@vger.kernel.org, Ard Biesheuvel , Eric Ricther , linux-kernel@vger.kernel.org, Claudio Carvalho , Matthew Garret , linuxppc-dev@ozlabs.org, Greg Kroah-Hartman , Rob Herring , Paul Mackerras , Jeremy Kerr , Elaine Palmer , Oliver O'Halloran , linux-integrity@vger.kernel.org, George Wilson List-Id: devicetree@vger.kernel.org On 10/02/2019 05:49 PM, Mimi Zohar wrote: > On Tue, 2019-10-01 at 12:07 -0400, Nayna wrote: >> On 09/30/2019 09:04 PM, Thiago Jung Bauermann wrote: >>> Hello, >> Hi, >> >>>> diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c >>>> new file mode 100644 >>>> index 000000000000..39401b67f19e >>>> --- /dev/null >>>> +++ b/arch/powerpc/kernel/ima_arch.c >>>> @@ -0,0 +1,33 @@ >>>> +// SPDX-License-Identifier: GPL-2.0 >>>> +/* >>>> + * Copyright (C) 2019 IBM Corporation >>>> + * Author: Nayna Jain >>>> + */ >>>> + >>>> +#include >>>> +#include >>>> + >>>> +bool arch_ima_get_secureboot(void) >>>> +{ >>>> + return is_powerpc_os_secureboot_enabled(); >>>> +} >>>> + >>>> +/* Defines IMA appraise rules for secureboot */ >>>> +static const char *const arch_rules[] = { >>>> + "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig", >>>> +#if !IS_ENABLED(CONFIG_MODULE_SIG) >>>> + "appraise func=MODULE_CHECK appraise_type=imasig|modsig", >>>> +#endif >>>> + NULL >>>> +}; >>>> + >>>> +/* >>>> + * Returns the relevant IMA arch policies based on the system secureboot state. >>>> + */ >>>> +const char *const *arch_get_ima_policy(void) >>>> +{ >>>> + if (is_powerpc_os_secureboot_enabled()) >>>> + return arch_rules; >>>> + >>>> + return NULL; >>>> +} >>> If CONFIG_MODULE_SIG is enabled but module signatures aren't enforced, >>> then IMA won't enforce module signature either. x86's >>> arch_get_ima_policy() calls set_module_sig_enforced(). Doesn't the >>> powerpc version need to do that as well? >>> >>> On the flip side, if module signatures are enforced by the module >>> subsystem then IMA will verify the signature a second time since there's >>> no sharing of signature verification results between the module >>> subsystem and IMA (this was observed by Mimi). >>> >>> IMHO this is a minor issue, since module loading isn't a hot path and >>> the duplicate work shouldn't impact anything. But it could be avoided by >>> having a NULL entry in arch_rules, which arch_get_ima_policy() would >>> dynamically update with the "appraise func=MODULE_CHECK" rule if >>> is_module_sig_enforced() is true. >> Thanks Thiago for reviewing.  I am wondering that this will give two >> meanings for NULL. Can we do something like below, there are possibly >> two options ? >> >> 1. Set IMA_APPRAISED in the iint->flags if is_module_sig_enforced(). >> >> OR >> >> 2. Let ima_get_action() check for is_module_sig_enforced() when policy >> is appraise and func is MODULE_CHECK. > I'm a bit hesitant about mixing the module subsystem signature > verification method with the IMA measure "template=ima-modsig" rules. >  Does it actually work? > > We can at least limit verifying the same appended signature twice to > when "module.sig_enforce" is specified on the boot command line, by > changing "!IS_ENABLED(CONFIG_MODULE_SIG)" to test > "CONFIG_MODULE_SIG_FORCE". Yes this seems to be a better idea. I have implemented this in the v7 version of the ima_arch version. Thanks & Regards,      - Nayna