Return-path: Received: from mail-ig0-f178.google.com ([209.85.213.178]:37261 "EHLO mail-ig0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755190AbbIBUyp (ORCPT ); Wed, 2 Sep 2015 16:54:45 -0400 Received: by igbni9 with SMTP id ni9so24255163igb.0 for ; Wed, 02 Sep 2015 13:54:44 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150902184604.GB8051@wotan.suse.de> References: <1440462367.2737.4.camel@linux.vnet.ibm.com> <1440464705.2737.36.camel@linux.vnet.ibm.com> <14540.1440599584@warthog.procyon.org.uk> <31228.1440671938@warthog.procyon.org.uk> <36ddb60c1d22756234392a2d065a02cb.squirrel@twosheds.infradead.org> <20150827212907.GF8051@wotan.suse.de> <20150902000915.GW8051@wotan.suse.de> <1441164905.17898.86.camel@linux.vnet.ibm.com> <20150902184604.GB8051@wotan.suse.de> Date: Wed, 2 Sep 2015 13:54:43 -0700 Message-ID: (sfid-20150902_225505_256777_A5F0119C) Subject: Re: Linux Firmware Signing From: Kees Cook To: "Luis R. Rodriguez" Cc: Mimi Zohar , David Woodhouse , David Howells , Andy Lutomirski , "Roberts, William C" , "linux-security-module@vger.kernel.org" , LKML , linux-wireless , "james.l.morris@oracle.com" , "serge@hallyn.com" , Vitaly Kuznetsov , Paul Moore , Eric Paris , SE Linux , Stephen Smalley , "Schaufler, Casey" , "Luis R. Rodriguez" , Dmitry Kasatkin , Greg Kroah-Hartman , Peter Jones , Takashi Iwai , Ming Lei , Joey Lee , =?UTF-8?B?Vm9qdMSbY2ggUGF2bMOtaw==?= , Kyle McMartin , Seth Forshee , Matthew Garrett , Johannes Berg , Jay Schulist , Daniel Borkmann , Alexei Starovoitov Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, Sep 2, 2015 at 11:46 AM, Luis R. Rodriguez wrote: > On Tue, Sep 01, 2015 at 11:35:05PM -0400, Mimi Zohar wrote: >> > OK great, I think that instead of passing the actual routine name we should >> > instead pass an enum type for to the LSM, that'd be easier to parse and we'd >> > then have each case well documented. Each LSM then could add its own >> > documetnation for this and can switch on it. If we went with a name we'd have >> > to to use something like __func__ and then parse that, its not clear if we need >> > to get that specific. >> >> Agreed. IMA already defines an enumeration. >> >> /* IMA policy related functions */ >> enum ima_hooks { FILE_CHECK = 1, MMAP_CHECK, BPRM_CHECK, MODULE_CHECK, >> FIRMWARE_CHECK, POLICY_CHECK, POST_SETATTR }; >> > > We want something that is not only useful for IMA but any other LSM, > and FILE_CHECK seems very broad, not sure what BPRM_CHECK is even upon > inspecting kernel code. Likewise for POST_SETATTR. POLICY_CHECK might > be broad, perhaps its best we define then a generic set of enums to > which IMA can map them to then and let it decide. This would ensure > that the kernel defines each use caes for file inspection carefully, > documents and defines them and if an LSM wants to bunch a set together > it can do so easily with a switch statement to map set of generic > file checks in kernel to a group it already handles. > > For instance at least in the short term we'd try to unify: > > security_kernel_fw_from_file() > security_kernel_module_from_file() > > to perhaps: > > security_kernel_from_file() > > As far, as far as I can tell, the only ones we'd be ready to start > grouping immediately or with small amount of work rather soon: > > /** > * > * enum security_filecheck - known kernel security file checks types > * > * @__SECURITY_FILECHECK_UNSPEC: attribute 0 reserved > * @SECURITY_FILECHECK_MODULE: the file being processed is a Linux kernel module > * @SECURITY_FILECHECK_SYSDATA: the file being processed is either a firmware > * file or a system data file read from /lib/firmware/* by firmware_class I'd prefer a distinct category for firmware, as it carries an implication that it is an executable blob of some sort (I know not all are, though). -Kees > * @SECURITY_FILECHECK_KEXEC_KERNEL: the file being processed is a kernel file > * used by kexec > * @SECURITY_FILECHECK_KEXEC_INITRAMFS: the file being processed is an initramfs > * used by kexec > > * The kernel reads files directly from the filesystem for a series of > * operations. The list of files the kernel reads from the filesystem are > * limited and each type of file consumed may have a different format and > * security vetting procedures. The kernel enables LSMs to vet for these files > * through a shared LSM hook prior to consumption. This list documents the > * different special kernel file types read by the kernel, it enables LSMs > * to vet for each differently if needed. > enum security_filecheck { > SECURITY_FILECHECK_UNSPEC, > SECURITY_FILECHECK_MODULE, > SECURITY_FILECHECK_SYSDATA, > SECURITY_FILECHECK_KEXEC_KERNEL, > SECURITY_FILECHECK_KEXEC_INITRAMFS, > }; > > Provided the MOK thing or alternative gets addressed we could also soon add > something for SELinux policy files but that needs to be discussed further > it seems. If MOK is used would SECURITY_FILECHECK_POLICY_MOK be OK? Again > this would likely need further discussion, its why I didn't list it above. > > Luis -- Kees Cook Chrome OS Security