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vboot: use recovery button as dev mode switch confirmation

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We don't allow ENTER from a USB keyboard as the confirmation
in the switch from normal to developer mode.

For devices that have a physical recovery button, we require
a recovery button press instead.  For other devices, we
require that ENTER be pressed on the internal keyboard.

This prevents an "evil keyboard" attack in which a USB keyboard
(or other USB device pretending to be a keyboard) sends a
control-D/ENTER sequence shortly after every boot (followed
by more evil keys).  In that situation, when users power-on in
recovery mode, they will be forced to dev mode even if it
was not their intention.  Further attacks are easy at
that point.

TESTING.  On a panther device:

1. powered on with recovery button pressed -> booted in recovery mode
2. pressed control-D on external USB keyboard -> got to ToDev? screen
3. pressed ENTER -> system beeped
4. pressed recovery button -> system rebooted in DEV mode

... all as expected

Also:

1. powered on with recovery button pressed and HELD recovery button
2. pressed control-D -> system beeped

BUG=chrome-os-partner:21729
TEST=manual (see commit message)
BRANCH=none
CQ-DEPEND=CL:182420,CL:182946,CL:182357

Change-Id: Ib986d00d4567c2d447f8bbff0e5ccfec94596aa7
Reviewed-on: https://chromium-review.googlesource.com/182241
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Tested-by: Luigi Semenzato <semenzato@chromium.org>
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>
This commit is contained in:
Luigi Semenzato
2014-01-10 16:26:08 -08:00
committed by chrome-internal-fetch
parent 46e00e6380
commit a53a0b040f
7 changed files with 178 additions and 10 deletions
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2
firmware/lib/vboot_api_init.c
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@@ -76,6 +76,8 @@ VbError_t VbInit(VbCommonParams *cparams, VbInitParams *iparams)
shared->flags |= VBSD_EC_SOFTWARE_SYNC;
if (iparams->flags & VB_INIT_FLAG_EC_SLOW_UPDATE)
shared->flags |= VBSD_EC_SLOW_UPDATE;
if (iparams->flags & VB_INIT_FLAG_VIRTUAL_REC_SWITCH)
shared->flags |= VBSD_BOOT_REC_SWITCH_VIRTUAL;
is_s3_resume = (iparams->flags & VB_INIT_FLAG_S3_RESUME ? 1 : 0);