> > 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.
Mimi
> 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
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