diff --git a/enforcement-case-studies.tex b/enforcement-case-studies.tex index dee945ef49b06ac98a71ceea0bb7760c8d475205..c7eab0a13ee638cbe41485398ca4c0b8a8967f54 100644 --- a/enforcement-case-studies.tex +++ b/enforcement-case-studies.tex @@ -585,59 +585,60 @@ compilation). %FIXME: dg: can you get me a screen shot for the Kernel Log above, and paste %in the output of running busybox ? -\section{U-Boot Installation} - -The U-Boot installation process is substantially more complicated than the -firmware update. The investigator purchased the optional a serial cable -along with the TPE-NWIFIROUTER, in order to complete the U-Boot installation -per the instructions in'' -boot\verb0_0reflash''. - -However, we were -only able to read data from the serial port; we were unable to interrupt the -boot process or access the U-Boot console to complete the U-Boot re-flash. Here -are the steps we tried: - -* We found the serial cable included was a USB serial adapter that had a male - USB type A connector on one end and 4 female jumper wires at the other end. - These female jumper wires were red, black, white, and green. -* The instructions did not specify how to connect these wires, but we were able - to determine this in part using the "v8.4" image (close to our "v8.2" router) - at \url{http://wiki.openwrt.org/toh/tp-link/tl-wr841nd#serial.console} . Aside from - power and ground (red and black), we did have to guess which of the wires was - RX and TX. By experimentation we found that green was RX and white was TX. - When we tried the other way, we received no data to our serial console at boot - time. -* We did have to use the included jumper pin gender changer with the USB serial - adapter, which we put through the holes on the router's mainboard and then - connected to the USB serial adapter. The fit was fairly loose so it would be - nice if future router versions included a tighter gender changer or (ideally) - had the jumper pins soldered onto the board to begin with (so no gender - changer would be required). -* We used 115200 8N1 as our serial console settings (with no hardware or - software flow control). This was tested with both the minicom and screen - commands. We found that if we connected all 4 wires on the USB serial adapter - that the router would start without additional power and our console would - receive the startup messages. We could replicate the same behavior by - omitting the power cable from the USB serial adapter (red wire) and connecting - the main power adapter to the router instead. -* While we did see the U-Boot and kernel boot logs in our serial console, we - were unable to interrupt the boot process as u-boot\verb0_0reflash indicated we - should. We suspect this is a misconfiguration of our serial console, but it's - unclear exactly how it is misconfigured, as we were able to receive data fine - (we just couldn't send data to the router). -* As a result, we were unable to complete the U-Boot installation test. We did - appreciate that installation instructions were included, though these - instructions should be updated to include more specifics about connecting the - serial cable. Since ThinkPenguin does have the option to ship a serial - adapter with the router, it would be helpful if instructions specific to that - adapter were included, as the wiring configuration one should use was unclear. -* Additionally, instructions for removing the router's case should be included. - We found that the two screws that needed removal to open the case were hidden - underneath rubber feet on the case. Indicating which feet need removal to - unscrew the case would be helpful. The instructions should also note that the - case needs to be carefully separated once the screws are removed; it - effectively snaps apart, but care must be taken to avoid breaking the plastic - fasteners that keep the case together after the screws are removed. + +%% \section{U-Boot Installation} + +%% The U-Boot installation process is substantially more complicated than the +%% firmware update. The investigator purchased the optional a serial cable +%% along with the TPE-NWIFIROUTER, in order to complete the U-Boot installation +%% per the instructions in'' -boot\verb0_0reflash''. + +%% However, we were +%% only able to read data from the serial port; we were unable to interrupt the +%% boot process or access the U-Boot console to complete the U-Boot re-flash. Here +%% are the steps we tried: + +%% * We found the serial cable included was a USB serial adapter that had a male +%% USB type A connector on one end and 4 female jumper wires at the other end. +%% These female jumper wires were red, black, white, and green. +%% * The instructions did not specify how to connect these wires, but we were able +%% to determine this in part using the "v8.4" image (close to our "v8.2" router) +%% at \url{http://wiki.openwrt.org/toh/tp-link/tl-wr841nd#serial.console} . Aside from +%% power and ground (red and black), we did have to guess which of the wires was +%% RX and TX. By experimentation we found that green was RX and white was TX. +%% When we tried the other way, we received no data to our serial console at boot +%% time. +%% * We did have to use the included jumper pin gender changer with the USB serial +%% adapter, which we put through the holes on the router's mainboard and then +%% connected to the USB serial adapter. The fit was fairly loose so it would be +%% nice if future router versions included a tighter gender changer or (ideally) +%% had the jumper pins soldered onto the board to begin with (so no gender +%% changer would be required). +%% * We used 115200 8N1 as our serial console settings (with no hardware or +%% software flow control). This was tested with both the minicom and screen +%% commands. We found that if we connected all 4 wires on the USB serial adapter +%% that the router would start without additional power and our console would +%% receive the startup messages. We could replicate the same behavior by +%% omitting the power cable from the USB serial adapter (red wire) and connecting +%% the main power adapter to the router instead. +%% * While we did see the U-Boot and kernel boot logs in our serial console, we +%% were unable to interrupt the boot process as u-boot\verb0_0reflash indicated we +%% should. We suspect this is a misconfiguration of our serial console, but it's +%% unclear exactly how it is misconfigured, as we were able to receive data fine +%% (we just couldn't send data to the router). +%% * As a result, we were unable to complete the U-Boot installation test. We did +%% appreciate that installation instructions were included, though these +%% instructions should be updated to include more specifics about connecting the +%% serial cable. Since ThinkPenguin does have the option to ship a serial +%% adapter with the router, it would be helpful if instructions specific to that +%% adapter were included, as the wiring configuration one should use was unclear. +%% * Additionally, instructions for removing the router's case should be included. +%% We found that the two screws that needed removal to open the case were hidden +%% underneath rubber feet on the case. Indicating which feet need removal to +%% unscrew the case would be helpful. The instructions should also note that the +%% case needs to be carefully separated once the screws are removed; it +%% effectively snaps apart, but care must be taken to avoid breaking the plastic +%% fasteners that keep the case together after the screws are removed. \section{Firmware Comparison}