From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:30936 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726872AbgGJS4Q (ORCPT ); Fri, 10 Jul 2020 14:56:16 -0400 Message-ID: <1594407288.14405.36.camel@linux.ibm.com> Subject: Re: [PATCH v5] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime From: Mimi Zohar Date: Fri, 10 Jul 2020 14:54:48 -0400 In-Reply-To: <20200710183420.GB10547@glitch> References: <20200709164647.45153-1-bmeneg@redhat.com> <1594401804.14405.8.camel@linux.ibm.com> <20200710180338.GA10547@glitch> <20200710183420.GB10547@glitch> Content-Type: text/plain; charset="utf-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Bruno Meneguele Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-integrity@vger.kernel.org, erichte@linux.ibm.com, nayna@linux.ibm.com, stable@vger.kernel.org On Fri, 2020-07-10 at 15:34 -0300, Bruno Meneguele wrote: > On Fri, Jul 10, 2020 at 03:03:38PM -0300, Bruno Meneguele wrote: > > On Fri, Jul 10, 2020 at 01:23:24PM -0400, Mimi Zohar wrote: > > > On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote: > > > > APPRAISE_BOOTPARAM has been marked as dependent on !ARCH_POLICY in compile > > > > time, enforcing the appraisal whenever the kernel had the arch policy option > > > > enabled. > > > > > > > However it breaks systems where the option is set but the system didn't > > > > boot in a "secure boot" platform. In this scenario, anytime an appraisal > > > > policy (i.e. ima_policy=appraisal_tcb) is used it will be forced, without > > > > giving the user the opportunity to label the filesystem, before enforcing > > > > integrity. > > > > > > > > Considering the ARCH_POLICY is only effective when secure boot is actually > > > > enabled this patch remove the compile time dependency and move it to a > > > > runtime decision, based on the secure boot state of that platform. > > > > > > Perhaps we could simplify this patch description a bit? > > > > > > The IMA_APPRAISE_BOOTPARAM config allows enabling different > > > "ima_appraise=" modes - log, fix, enforce - at run time, but not when > > > IMA architecture specific policies are enabled.  This prevents > > > properly labeling the filesystem on systems where secure boot is > > > supported, but not enabled on the platform.  Only when secure boot is > > > enabled, should these IMA appraise modes be disabled. > > > > > > This patch removes the compile time dependency and makes it a runtime > > > decision, based on the secure boot state of that platform. > > > > > > > Sounds good to me. > > > > > > > > > > > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > > > > index a9649b04b9f1..884de471b38a 100644 > > > > --- a/security/integrity/ima/ima_appraise.c > > > > +++ b/security/integrity/ima/ima_appraise.c > > > > @@ -19,6 +19,11 @@ > > > > static int __init default_appraise_setup(c > > > > > > > har *str) > > > > { > > > > #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM > > > > + if (arch_ima_get_secureboot()) { > > > > + pr_info("appraise boot param ignored: secure boot enabled"); > > > > > > Instead of a generic statement, is it possible to include the actual > > > option being denied?  Perhaps something like: "Secure boot enabled, > > > ignoring %s boot command line option" > > > > > > Mimi > > > > > > > Yes, sure. > > > > Btw, would it make sense to first make sure we have a valid "str" > option and not something random to print? > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > index a9649b04b9f1..1f1175531d3e 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -25,6 +25,16 @@ static int __init default_appraise_setup(char *str) > ima_appraise = IMA_APPRAISE_LOG; > else if (strncmp(str, "fix", 3) == 0) > ima_appraise = IMA_APPRAISE_FIX; > + else > + pr_info("invalid \"%s\" appraise option"); > + > + if (arch_ima_get_secureboot()) { > + if (!is_ima_appraise_enabled()) { > + pr_info("Secure boot enabled: ignoring ima_appraise=%s boot parameter option", > + str); > + ima_appraise = IMA_APPRAISE_ENFORCE; > + } > + } Providing feedback is probably a good idea.  However, the "arch_ima_get_secureboot" test can't come after setting "ima_appraise." Mimi > #endif > return 1; > } > > > The "else" there I think would make sense as well, at least to give the > user some feedback about a possible mispelling of him (as a separate > patch). > > And "if(!is_ima_appraise_enabled())" would avoid to print anything about > "ignoring the option" to the user in case he explicitly set "enforce", > which we know there isn't any real effect but is allowed and shown in > kernel-parameters.txt. > > > Thanks! > > > > > > + return 1; > > > > + } > > > > + > > > > if (strncmp(str, "off", 3) == 0) > > > > ima_appraise = 0; > > > > else if (strncmp(str, "log", 3) == 0) > > > > > > > -- > > bmeneg > > PGP Key: http://bmeneg.com/pubkey.txt > > >