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From: James Morris <jmorris@namei.org>
To: Matthew Garrett <mjg59@google.com>
Cc: LSM List <linux-security-module@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	Linux API <linux-api@vger.kernel.org>,
	Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH V32 01/27] Add the ability to lock down access to the running kernel image
Date: Fri, 3 May 2019 07:07:15 +1000 (AEST)	[thread overview]
Message-ID: <alpine.LRH.2.21.1905030653480.32502@namei.org> (raw)
In-Reply-To: <CACdnJus-+VTy0uOWg982SgZr55Lp7Xot653dJb_tO5T=J6D8nw@mail.gmail.com>

On Mon, 29 Apr 2019, Matthew Garrett wrote:

> Hi James,
> 
> What's the best way forward with this? I'm still not entirely clear on
> how it can be implemented purely as an LSM, but if you have ideas on
> what sort of implementation you'd prefer I'm happy to work on that.

It can't be implemented purely as an LSM.

The concerns I have are:

  o Mixing of mechanism and policy (they are hardcoded together)
  o Too-coarse policy (all or nothing, which will lead many to choose   
    nothing)
  o Lack of integration with LSM
  o Completeness
  o Maintenance (including adding new lockdowns without breaking existing 
    userspace)
  
One possible direction is to (as previously mentioned) assign IDs to each 
callsite and be able to check this ID against a simple policy array 
(allow/deny).  The default policy choices could be reduced to 'all' or 
'none' during kconfig, and allow a custom policy to be loaded later if 
desired.

Within the policy check hook, we could add a new LSM hook, which would 
allow an LSM to restrictively override the lockdown policy with its own 
(so e.g. SELinux could utilize the context of the current process to 
determine if a lockdown feature should be enforced).

This doesn't really address the completeness / maintenance issue (i.e. "do 
we have everything covered and how do we ensure this on an ongoing 
basis?", and "what will this new lockdown feature break?"), although it 
should make it easier to add new lockdown callsites as they don't have to 
be enabled by the user.

Thoughts?

-- 
James Morris
<jmorris@namei.org>


  reply	other threads:[~2019-05-02 21:07 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-04  0:32 [PATCH V32 0/27] Lockdown patches for 5.2 Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-04-16  8:40   ` Andrew Donnellan
2019-04-16  8:40     ` Andrew Donnellan
2019-04-18  6:38     ` Daniel Axtens
2019-04-18  6:38       ` Daniel Axtens
2019-04-18 19:35     ` Matthew Garrett
2019-04-18 19:35       ` Matthew Garrett
2019-04-29  0:06       ` Daniel Axtens
2019-04-29  0:06         ` Daniel Axtens
2019-04-29  4:54         ` Daniel Axtens
2019-04-29  4:54           ` Daniel Axtens
2019-04-30  5:15           ` Andrew Donnellan
2019-04-30  5:15             ` Andrew Donnellan
2019-04-29 22:56   ` Matthew Garrett
2019-05-02 21:07     ` James Morris [this message]
2019-05-02 21:15       ` Matthew Garrett
2019-05-02 23:19         ` James Morris
2019-05-03  0:34           ` Andy Lutomirski
2019-04-04  0:32 ` [PATCH V32 02/27] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 03/27] Restrict /dev/{mem,kmem,port} when " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 04/27] kexec_load: Disable at runtime if " Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 05/27] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 06/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 07/27] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 08/27] hibernate: Disable when " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 09/27] uswsusp: " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 10/27] PCI: Lock down BAR access " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 11/27] x86: Lock down IO port " Matthew Garrett
2019-04-04  7:49   ` Thomas Gleixner
2019-04-04  0:32 ` [PATCH V32 12/27] x86/msr: Restrict MSR " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 13/27] ACPI: Limit access to custom_method " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 14/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 15/27] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-04-04  0:32   ` Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 16/27] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 17/27] Lock down TIOCSSERIAL Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 18/27] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 19/27] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-04-04  1:33   ` Steven Rostedt
2019-04-04  7:47   ` Thomas Gleixner
2019-04-04  0:32 ` [PATCH V32 20/27] Lock down /proc/kcore Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 21/27] Lock down tracing and perf kprobes when in confidentiality mode Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 22/27] bpf: Restrict bpf when kernel lockdown is " Matthew Garrett
2019-04-30 19:19   ` Jann Horn
2019-04-04  0:32 ` [PATCH V32 23/27] Lock down perf when " Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 24/27] kexec: Allow kexec_file() with appropriate IMA policy when locked down Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 25/27] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 26/27] debugfs: Restrict debugfs when the kernel is locked down Matthew Garrett
2019-04-04  0:32 ` [PATCH V32 27/27] tracefs: Restrict tracefs " Matthew Garrett
2019-04-04 13:39   ` Steven Rostedt
2019-04-04 20:09     ` Matthew Garrett

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