From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 84371724 for ; Sun, 31 Jul 2016 16:19:49 +0000 (UTC) Received: from mail-ua0-f171.google.com (mail-ua0-f171.google.com [209.85.217.171]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id C908E217 for ; Sun, 31 Jul 2016 16:19:48 +0000 (UTC) Received: by mail-ua0-f171.google.com with SMTP id 35so91927281uap.1 for ; Sun, 31 Jul 2016 09:19:48 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1469979098.23563.300.camel@linux.vnet.ibm.com> References: <20160716005213.GL30372@sirena.org.uk> <1469544138.120686.327.camel@infradead.org> <14209.1469636040@warthog.procyon.org.uk> <1469636881.27356.70.camel@HansenPartnership.com> <1469637367.27356.73.camel@HansenPartnership.com> <1469648220.23563.15.camel@linux.vnet.ibm.com> <20160728165728.GR4541@io.lakedaemon.net> <1469830256.23563.200.camel@linux.vnet.ibm.com> <20160730163626.GP3296@wotan.suse.de> <1469934481.23563.274.camel@linux.vnet.ibm.com> <1469979098.23563.300.camel@linux.vnet.ibm.com> From: Andy Lutomirski Date: Sun, 31 Jul 2016 09:19:28 -0700 Message-ID: To: Mimi Zohar Content-Type: text/plain; charset=UTF-8 Cc: James Bottomley , Mark Brown , "ksummit-discuss@lists.linuxfoundation.org" , Jason Cooper Subject: Re: [Ksummit-discuss] Last minute nominations: mcgrof and toshi List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sun, Jul 31, 2016 at 8:31 AM, Mimi Zohar wrote: > On Sa, 2016-07-30 at 20:09 -0700, Andy Lutomirski wrote: >> On Jul 30, 2016 8:08 PM, "Mimi Zohar" wrote: >> > >> > On Sa, 2016-07-30 at 18:36 +0200, Luis R. Rodriguez wrote: >> > > On Fri, Jul 29, 2016 at 03:25:09PM -0700, Andy Lutomirski wrote: >> > > > On Fri, Jul 29, 2016 at 3:10 PM, Mimi Zohar >> wrote: >> > > > > On Do, 2016-07-28 at 16:57 +0000, Jason Cooper wrote: >> > > > >> Hi Andy, >> > > > >> >> > > > >> On Wed, Jul 27, 2016 at 01:09:37PM -0700, Andy Lutomirski wrote: >> > > > >> ... >> > > > >> > I would like someone to explain why using the keyring mechanism >> for >> > > > >> > this in the first place is a good idea. >> > > > >> > >> > > > >> > As far as I can tell, the design goals of "keys trusted by the >> kernel >> > > > >> > for modules, firmware, etc" are: >> > > > >> > >> > > > >> > - Keys are added at build time or, according to potentially >> > > > >> > system-specific rules, at boot time. >> > > > >> > >> > > > >> > - Keys should specify what they're trusted *for*. >> > > > >> >> > > > >> Well, I'd argue that keys should specify what they are *intended* >> for by >> > > > >> the keyholder. A useful security system could further restrict >> the key >> > > > >> as needed. >> > > > > >> > > > > We've already started. Currently the kernel_read_file() and family >> of >> > > > > functions provide the LSM hooks needed for verifying file >> signatures of >> > > > > files read by the kernel. The kernel_read_file_id enumeration is >> used >> > > > > to differentiate between callers. Based on this enumeration, the >> > > > > *intended* for could be defined. It would make sense to extend the >> IMA >> > > > > policy language to support *intended* for. >> > > > > >> > > > >> > > > Having kernel_read_file know the purpose is a big step in the right >> > > > direction, although, as I think I and others have pointed out, just an >> > > > enum is insufficient -- for firmware, at least, the *name* is >> > > > relevant. >> > >> > > The name is passed for firmware, the wrapper >> kernel_read_file_from_path() >> > > is used. So if we wanted an LSM extension on name I think we can do that >> > > on kernel_read_file_from_path() ? >> > >> > It shouldn't make a difference whether kernel_read_file() is called >> > directly, or the kernel_read_file_by_path/fd() are called. The pathname >> > is accessible from the "file" argument. >> > >>l >> What happens if a symlink is involved? > > For callers of kernel_read_file_by_path(), like firmware, we could pass > the pathname, but for the other callers of kernel_read_file/_by_fd() we > could use d_absolute_path(). That seems pointlessly fragile to me, and this issue has been known for longer than the code in question has even existed. How about: struct kernel_trusted_file_description { enum kernel_read_file_id type; const char *specific_purpose; /* may be NULL for KEXEC_IMAGE, etc. */ }; int kernel_read_file(struct file *, void **, loff_t *, const struct trusted_file_description *); rather than trying to guess. Also, are there any plans to move module signature verification into .kernel_post_read_file? --Andy