Add chrome OS power wash + dev mode

content/post/2020-01-11.md

+---
+title: "Starting Point"
+author: ""
+type: ""
+date: 2020-01-11T12:51:46-05:00
+subtitle: ""
+image: ""
+tags: [chromeos]
+---
+
+As mentioned in my [new year's plan](../2020-01-04#motivation) a motivation for
+my current project is having an End-of-life (EOL) Chromebook and wanting to
+bring it up to date.
+
+
+## The Hardware
+
+**Acer C720**, as pulled from the helpful [Developer Information for Chrome OS Devices][dd]
+
+<!--more-->
+
+[dd]:https://sites.google.com/a/chromium.org/dev/chromium-os/developer-information-for-chrome-os-devices
+
+Field                 | Data
+----------------------|-------------------------------
+Release               | September 12, 2013
+OEM                   | Acer
+Model                 | Acer C720/C70P/C740 Chromebook
+Code name             | Peppy & Pepto
+Board name(s)         | peppy
+Base board            | slippy
+User ABI              | x86_64
+Kernel                | 3.8
+Kernel ABI            | x86_64
+Platform              | Haswell
+Form Factor           | Chromebook
+First Release         | R30
+EOL/AUE               | R76
+USB Gadget            | No
+Closed Case Debugging | No
+
+
+Prior to power washing the device it showed:
+
+- Version: `76.0.3809.136 (Official Build) (64-bit)`
+- Platform: `12239.92.0 (Official Build)`
+- Channel: `stable-channel peppy`
+- Firmware: `Google_Peppy.4389.117.0`
+- Build Date: `Tuesday, August 27, 2019`
+- Kernel: `Linux localhost 3.8.11 #1 SMP Tue Aug 27 16:53:30 PDT 2019 x86_64 Intel(R) Celeron(R) 2955U @ 1.40GHz GenuineIntel GNU/Linux`
+
+![About Chrome OS](../../img/c720_about_chromeOS.png)
+![Detailed Build Information](../../img/c720_detailed_build_info.png)
+
+
+### Firmware Aside
+
+Interestingly while power washing I was provided an option to "Update firmware for added security":
+
+![Reset Chrome Device](../../img/reset_chrome_device.jpg)
+![Update Chromebook Security](../../img/update_chromebook_security.jpg)
+
+Even more interesting was this did not result in a higher firmware version.
+After the power wash and logging in as a guest it still reports
+`Google_Peppy.4389.117.0`. To cap it all off a second power wash did not prompt
+for a firmware update???
+
+While looking for more information on this I found the [Trusted Platform Module
+firmware vulnerability: technical documentation][ff] (fortunately my machine was
+properly patched. Helpfully though this referenced `chrome://system` as a place
+to get detailed firmware information. It has a ton of great information.
+
+[ff]:https://www.chromium.org/chromium-os/tpm_firmware_update
+
+For example the `ec_info`:
+
+```
+vendor               | ti
+name                 | Unknown-10de
+fw_version           | peppy_v1.5.133-9078375
+```
+
+This refers to the [embedded controller][ec], which how cool is it that all this
+information is publicly available.
+
+[ec]:https://chromium.googlesource.com/chromiumos/platform/ec/+/master/README.md
+
+Similarly the `tpm_version`:
+
+```
+tpm_family 312e3200
+spec_level 0000000200000003
+vendor 49465800
+tpm_model ffffffff
+firmware_version 0000000000000422
+vendor_specific 042203f20274706d3338ffffff
+version_fingerprint 487001745 1d070e91
+```
+
+Note version `0000000000000422 - 4.34` is fixed. Yay.
+
+As a final note the `dmesg` output had a few interesting lines. The first of
+which is perhaps the aforementioned firmware update (though oddly it seem to get
+applied every boot)?
+
+```
+[   12.150597] hda-intel 0000:00:1b.0: Applying patch firmware 'peppy_alsa.fw'
+```
+
+The other of which, is probably an interesting rabbit hole:
+
+```
+[    0.097482] chromeos: tpm attack callbacks: -19
+```
+
+Some quick references are probably [Issue 473051: Unexpected error is seen while
+recovering on peppy and falco][ii] and the linked [commit][com]. As well as the
+remark
+
+> CHROMIUM: ignore errors when registering tpm attack callbacks.
+> 
+> This feature is only used on some platforms and only for
+> logging purposes, so it is safe to let it not work.
+
+
+[ii]:https://bugs.chromium.org/p/chromium/issues/detail?id=473051
+[com]:https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/262451/
+
+
+Enough on the firmware rabbit hole, but one final tidbit I found interesting is
+that even to get to guest mode seemed to required network connectivity and
+accepting some Terms of Service. A quick search did not immediately reveal a way
+around this. If would be interesting to log this connection and see what, if
+any, traffic is actually sent.
+
+## On to Developer Mode
+
+
+Consulting the [Debug Button Shortcuts][dbs] has all kinds of interesting key
+combinations. The specific one we want is Recovery Mode (`Esc + Refresh and
+press Power`) then Developer Mode (`Ctrl + D`).
+
+[dbs]:https://chromium.googlesource.com/chromiumos/docs/+/master/debug_buttons.md
+
+It really is that easy.
+
+## Meta
+
+I have power washed chromebooks and worked in developer mode a number of times
+previously, but this all goes to show that you can always dig deeper and learn
+more, even doing tasks that seem straight forward.
+
+
+## Next
+
+I've actually gone ahead and build a chromiumos image, but I'm going to leave
+describing that (and testing it to another session).