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Tue, 1 Oct 2019 01:04:58 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1F9F3C605A; Tue, 1 Oct 2019 01:04:53 +0000 (GMT) Received: from morokweng.localdomain (unknown [9.85.220.184]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTPS; Tue, 1 Oct 2019 01:04:52 +0000 (GMT) References: <1569594360-7141-1-git-send-email-nayna@linux.ibm.com> <1569594360-7141-4-git-send-email-nayna@linux.ibm.com> User-agent: mu4e 1.2.0; emacs 26.2 From: Thiago Jung Bauermann To: Nayna Jain Subject: Re: [PATCH v6 3/9] powerpc: add support to initialize ima policy rules In-reply-to: <1569594360-7141-4-git-send-email-nayna@linux.ibm.com> Date: Mon, 30 Sep 2019 22:04:48 -0300 Message-ID: <877e5pwa1b.fsf@morokweng.localdomain> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-09-30_14:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1910010009 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , devicetree@vger.kernel.org, linux-efi@vger.kernel.org, Ard Biesheuvel , Eric Ricther , linux-kernel@vger.kernel.org, Mimi Zohar , 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 Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hello, Nayna Jain writes: > PowerNV systems uses kernel based bootloader, thus its secure boot > implementation uses kernel IMA security subsystem to verify the kernel > before kexec. Since the verification policy might differ based on the > secure boot mode of the system, the policies are defined at runtime. > > This patch implements the arch-specific support to define the IMA policy > rules based on the runtime secure boot mode of the system. > > This patch provides arch-specific IMA policies if PPC_SECURE_BOOT > config is enabled. > > Signed-off-by: Nayna Jain > --- > arch/powerpc/Kconfig | 2 ++ > arch/powerpc/kernel/Makefile | 2 +- > arch/powerpc/kernel/ima_arch.c | 33 +++++++++++++++++++++++++++++++++ > include/linux/ima.h | 3 ++- > 4 files changed, 38 insertions(+), 2 deletions(-) > create mode 100644 arch/powerpc/kernel/ima_arch.c > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 2c54beb29f1a..54eda07c74e5 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -916,6 +916,8 @@ config PPC_SECURE_BOOT > prompt "Enable secure boot support" > bool > depends on PPC_POWERNV > + depends on IMA > + depends on IMA_ARCH_POLICY > help > Systems with firmware secure boot enabled needs to define security > policies to extend secure boot to the OS. This config allows user > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile > index 875b0785a20e..7156ac1fc956 100644 > --- a/arch/powerpc/kernel/Makefile > +++ b/arch/powerpc/kernel/Makefile > @@ -157,7 +157,7 @@ endif > obj-$(CONFIG_EPAPR_PARAVIRT) += epapr_paravirt.o epapr_hcalls.o > obj-$(CONFIG_KVM_GUEST) += kvm.o kvm_emul.o > > -obj-$(CONFIG_PPC_SECURE_BOOT) += secure_boot.o > +obj-$(CONFIG_PPC_SECURE_BOOT) += secure_boot.o ima_arch.o > > # Disable GCOV, KCOV & sanitizers in odd or sensitive code > GCOV_PROFILE_prom_init.o := n > 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. -- Thiago Jung Bauermann IBM Linux Technology Center