lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 08 Nov 2017 21:17:37 -0500
From:   Mimi Zohar <>
To:     "AKASHI, Takahiro" <>,
        "Luis R. Rodriguez" <>
Cc:     Greg Kroah-Hartman <>,
        Linus Torvalds <>,
        Jan Blunck <>,
        Julia Lawall <>,
        David Howells <>,
        Marcus Meissner <>, Gary Lin <>,,,
        linux-efi <>,, Matthew Garrett <>
Subject: Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel

> > IMHO that should just fail then, ie, a "locked down" kernel should not want to
> > *pass* a firmware signature if such thing could not be done.
> > 
> > Its no different than trying to verify a signed module on a "locked down" for
> > which it has no signature.
> > 
> > But perhaps I'm not understanding the issue well, let me know.
> My point is quite simple:
> my_deviceA_init() {
>         err = request_firmware(&fw, "deviceA"); <--- (a)
>         if (err)
>                 goto err_request;
>         err = verify_firmware(fw);  <--- (b)
>         if (err)
>                 goto err_verify;
>         load_fw_to_deviceA(fw);     <--- (c)
>         ...
> }
> As legacy device drivers does not have (b), there is no chance to
> prevent loading a firmware at (c) for locked-down kernel.
> If you allow me to bring in yet another function, say
> request_firmware_signable(), which should be used in place of (a)
> for all verification-aware drivers, that would be fine.

I really don't understand why you need a new function.  The
request_firmware() eventually calls kernel_read_file_from_path(),
which already calls the pre and post LSM hooks.

IMA-appraisal is already on these hooks verifying the requested
firmware's signature.  For systems with "lockdown" enabled, but
without IMA-appraisal enabled, define a small, builtin LSM that sits
on these LSM hooks and denies the unsigned firmware requests.


> In this case, all the invocation of request_firmware() in legacy code
> could be forced to fail in locked-down kernel.
> But I think that "signable" should be allowed to be combined with other
> features of request_firmware variants like _(no)wait or _direct.
> -Takahiro AKASHI

Powered by blists - more mailing lists