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

Luis R. Rodriguez
2018-06-01T18:21:34Z

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?

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
>
>

--
Do not panic