On Mon, Sep 26, 2022 at 4:01 AM Sughosh Ganu sughosh.ganu@linaro.org wrote:
On Mon, 26 Sept 2022 at 08:25, Jassi Brar jassisinghbrar@gmail.com wrote:
.....
+static __maybe_unused efi_status_t fwu_post_update_process(bool fw_accept_os) +{
int status;u32 update_index;efi_status_t ret;status = fwu_plat_get_update_index(&update_index);if (status < 0) {log_err("Failed to get the FWU update_index value\n");return EFI_DEVICE_ERROR;}/** All the capsules have been updated successfully,* update the FWU metadata.*/log_debug("Update Complete. Now updating active_index to %u\n",update_index);status = fwu_update_active_index(update_index);Do we want to check if all images in the bank are updated via capsules before switching the bank?
This function does get called only when the update status for every capsule is a success. Even if one of the capsules does not get updated, the active index will not get updated.
.... but we don't check if the capsule for each image in the bank is provided for update.
A developer will make sure all images are provided in one go, so that the switch is successful. But a malicious user may force some old vulnerable image back into use by updating all but that image.
That I believe is to be handled through a combination of implementing a rollback protection mechanism, along with capsule authentication. These are separate to the implementation of the multi bank updates that these patches are aiming for.
This sounds like : we don't worry about buffer-overflow vulnerabilities because the system will be secured and hardened by other mechanisms.
A/B update does not _require_ rollback-protection or capsure-authentication. A platform may rely on some other technology for tamper-proofing.
-j