Re: [PATCH v4 5/8] ima: based on policy require signed firmware (sysfs fallback)

Mimi Zohar
2018-06-01T22:40:18Z

On Fri, 2018-06-01 at 20:21 +0200, Luis R. Rodriguez wrote:
> On Tue, May 29, 2018 at 02:01:57PM -0400, Mimi Zohar wrote:
> > Luis, is the security_kernel_post_read_file LSM hook in
> > firmware_loading_store() still needed after this patch? Should it be
> > calling security_kernel_load_data() instead?
>
> That's up to Kees to decide as he added that hook, and knows
> what LSMs may be doing with it. From my perspective it is confusing
> to have that hook there so I think it could be removed now.
>
> Kees?

Commit 6593d92 ("firmware_class: perform new LSM checks") references
two methods of loading firmware -  filesystem-found firmware and
demand-loaded blobs.  I assume this call in firmware_loading_store()
is the demand-loaded blobs.  Does that method still exist?  Is it
still being used?

>
> Luis
>
> >
> > ---
> >
> > With an IMA policy requiring signed firmware, this patch prevents
> > the sysfs fallback method of loading firmware.
> >
> > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> > Cc: Luis R. Rodriguez <mcgrof@suse.com>
> > Cc: David Howells <dhowells@redhat.com>
> > Cc: Matthew Garrett <mjg59@google.com>
> > ---
> > security/integrity/ima/ima_main.c | 10 +++++++++-
> > 1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> > index a565d46084c2..4a87f78098c8 100644
> > --- a/security/integrity/ima/ima_main.c
> > +++ b/security/integrity/ima/ima_main.c
> > @@ -475,8 +475,10 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> >
> > if (!file && read_id == READING_FIRMWARE) {
> > if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
> > - (ima_appraise & IMA_APPRAISE_ENFORCE))
> > + (ima_appraise & IMA_APPRAISE_ENFORCE)) {
> > + pr_err("Prevent firmware loading_store.\n");
> > return -EACCES; /* INTEGRITY_UNKNOWN */
> > + }
> > return 0;
> > }
> >
> > @@ -520,6 +522,12 @@ int ima_load_data(enum kernel_load_data_id id)
> > pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
> > return -EACCES; /* INTEGRITY_UNKNOWN */
> > }
> > + break;
> > + case LOADING_FIRMWARE:
> > + if (ima_appraise & IMA_APPRAISE_FIRMWARE) {
> > + pr_err("Prevent firmware sysfs fallback loading.\n");
> > + return -EACCES; /* INTEGRITY_UNKNOWN */
> > + }
> > default:
> > break;
> > }
> > --
> > 2.7.5
> >
> >
>