design-challenge-error-404-brain-not-found

bl_build.py:

• Creates a seed for the key stream cipher
• Stores this seed with the rest of the code for the bootloader, as well as in the secret_build_output.txt file.
• The bootloader generates a main.bin file which has contents of flash memory

fw_protect.py:

• Reads in infile, outfile, version number, and release message

  python fw_protect --infile --outfile --version --message

Variables:

• infile (Specifies file to protect)
• outfile (Specifies file to write to)
• message (Uses as release message)
• version (Specifies firmware version number)

Protocol:

1. Combines release message and firmware while adding a nullbyte as a terminator
2. Generates key from stream cipher
3. Creates METADATA(version, size, and HMACS)
4. Creates an HMAC of the firmware and one of the Version and Size using two different keys and adds to METADATA
5. Breaks the firmware into frames with the first 16 bytes being IV, next 2 being size, at most 1kb of cipher text, and the tag as the last 16
6. Writes METADATA and framed firmware with release message to outdata

fw_update.py:

• Sends the data from the infile to the bootloader

  python fw_update --port --firmware [--debug]

Variables:

• port (Port to write to)
• firmware (Chooses file to install)
• [debug] (Turns on debug mode)

Protocol:

1. Handshake (update tool sends U, bootloader sends a U back)
2. Update tool sends over the metadata package (in frames if necessary)
3. Waits for "OK" byte before sending next frame
4. Send a black frame to indicate it is done sending frames

NOTE: If debug is turned on extra data is printed to screen

bootloader.c:

• Loads or boots firmware
• Rejects older versions or invalid firmware
• Generates key with stream cipher
• Prints to UART2

Protocol:

• Waits for byte to specify mode: "U" for update; "B" for boot
• 0x20 to UART0 resets device

Update mode:

1. Reads METADATA from update tool
2. Creates key with stream cipher
3. Verifies METADATA HMAC
4. If correct, writes METADATA to address 0xFC00
5. Reads each frame of firmware
6. Uses provided IV to decrypt data
7. Flashes to storage in pages starting at address 0x1000
8. Verifies firmware HMAC
9. If wrong, erases firmware
10. Sends "OK" to indicate end of update

Boot mode:

1. Prints release message
2. Boots firmware

Using the bootloader

1. Navigate to /firmware/firmware and run make
2. Navigate to /tools and run python bl_build.py to compile the bootloader
3. Run python bl_emulate.py to run the bootloader
4. Open a UART with miniterm /embsec/UARTX where X is the UART number

Using the firmware tools

1. Navigate to /tools and run the fw_protect.py tool to protect the firmware
2. Run the fw_update.py tool to attempt to update the booloader

NOTE: bl_emulate must be running before attempting to update the bootloader

Flow chart:

Behold our ASCII art!

*****,,**, *****************,***,*,***/**..,*********/,**,,,*,,,,*,,*,,*,.******
*,,*,***,, ***************,*****#/(&(((/*..*********,*****,*,*,******,**,.******
,*,*,*,*,, /************,**,,/%%#%#%%&&%%(%%****(/********,,,*****,,****,,******
,,*,,,,,,*******,,**..,,,,*%%&&%&&%&@&&&&&&@&&@@&&@%/*,,**************/*.,******
**,,,,*,,*********,*.,//#((&&&&@&&&&&@&%&%&&&@&&@%@&%%**,******,,,,,,,,,*,,,*,**
**,,,,************** .***(&&@@@@@@&&@#&@&@&@&&&&&&@@@@@%/%*************,********
,*,,,,,*******,***** ,*/%&%&%&&@@%&%@%#(((###&&&&@@&@&&&%((*********************
**,,.,,.. ......        (%&%%&&&&(***,,,,..,,,,**/#%&&&&&%/*******,,,,,,,*******
********* ,************/(&&%/*,,.. .............,,,*/#%@&%*****/**///*** .**,,,.
*/******* *****/*/*****(&%(/,,....   ........,...,,**/#&%#/*****//**//// ,******
********. *************%&%(*,....    ............,,,**/%&/***/*/**/*//// */*****
          ......,,,,***&&%/*,..... ...............,,,*/%%/*****///*///// //*****
**,,,,*,********,*** **%&*,#&%&%&&&&%(/*,,,*/#%&&&&%%#/(&((///*/**,,,,,. ..     
******,************* **#&%/**/((/((#((/@&&%%/((((///**(#%%&////***********//////
***,,*,*,*********** */*/(,,,*****/((//&,,,&/((/***/(/*/&#//////**/******///////
,,**,*****///*****// /.**.&...,,,,,,,*&,.,,/(*,/**,,,,,*#****//********/*///////
********(./*/*****/***,#,...  ,/((#/,*...,**//%&((//(%#*/.                     .
///////*/ /*////////*/..,,.....,*/,,,,,..,,****//,,.,,,**/*/////////////.*//////
///////// /////(////////,,,,,,/**,,,,,***********(/,,***////////(///((//,*//(///
***///*/*.///*//////////*,*,,**,,,.,,,,,,,,*,,,,,******/*******/////////.*////(/
///(/(/(((/(((((//*.*////*,,,.*,,/@.  . .   ..@#,,,,**.  ......,,,,*****.,/*////
////*////////////(/.//(((((,,,,,..,,,**//**////,,,,,*/////////////**/////*///***
/////////////////(*./(((((/*/*,,,,,..,,,***,,,,,*,**////////////***///*///////*/
/////////////////(,.(/((((**,*/*,,.,,.,,,,,,,,*,*/.*/////////////*///*//////////
        ....  .. .....,,,@*,,,**/*,,.,,.,,,,,***/(.,//(/(//////////////////////*
////////,,/**//////(***,#,*,,,,*************//**/%//////*///////////////.////(/(
////////,,//////,//,,*****,,,,,,,,,,,***********/(/////*////////////////.///////
////////,,//***(**/*,,****/,,,,,,,,,..,,,,,****/(/*///////(/////////////.///////
//(///*/*/**////*,,*/*,,*,,***,,,,,,,,..,******(/*//(*////((/*//(/*/////.///////
/**//****/*,/(//**,,****,******/*//*,,*****/////**/(/*//////(/(//((/*///(,......
/////***/*//(//(//*,,,,*//**,,/****///**///////**/((**(///*///(/**/(/*/((//*////
((//***///*/(/(///*/**,*,*//**********///*/*//*/////*//*****//////////*(*/////*/
(##(#(((////*****/////(((///////////((((((((////(%%%%%%%%%%##(#((/*/(#%%%%#%%%%%
((###(((//*//***//////(((((/((((#(//(/**(##%%%%%##%%%%%%%#%%%((/////(%%&%%%%%&&%
###(((((((((//((//////(/(##(((/,,.,,,..,,,,,,,,/#%##%%####(((/****///(#%%%%&&%%%
////((#%%#((((((#%%%%(/(/(#,,.,......,,. .. ..,,,,,*%%#((#%%%#((/(#((##%%%%%%&%%
@@&&%/*,*//////**/****/*,,,..,,,,,,,,,,**,,,,,,,,,,**#%&&&&&&&&&&&%##%%%%%%&&&%%
@@%///*//////((///*,///,/%&&&&@@@@@@@@@&&%*,***,,,,,,**&@@@@@@@@@@@@@@@@@@@@@@@@
&@%&%%%%&%%#####(((((&&@@@@@@&&&&&&&&&@&@&@@@&%,,/***/&/(@@@@@@@@@@@@@@@@@@@@@@@
@@@@@&&&/*,,***,,*&&@@@@@&&&&&&&&&&&&&&@@&&&&&&&&&%*,,/*//@@&%%##########%%%%&@@
&@@&%/**////////&&@@@@@&&&&&&&%%%%%%&%%%%%%&&&&&&%%%%%%(&*##((/////(%%%%#(/((##&
@@@%%&&#(#%&&%%#%@@@@@%%%&&&&&&%%#########%%%%###(/*,,*(%#///(#&&#(##(((/////(((
#(*,,*//(%&&%#/****(&%(#(((####%####%%#(##%%%&%(/*,....*%%#((((#%#((####///(%%%%
/(((/(((///(##((///&&&*,*/(#@@&&&%#((/*/#%@&%%%//(/,...,(&%#((///(//(#(###%%#%%&
/(((#%####%&&&&%%(**,&#,*,,*/(%#(//*,,,,,,,****,,......,(#*.,,(((%%%##%&&&&@&&@@
(/*/(((/*//*,*****,.,#%,,..,,,,,,**,,,,....,,..........,(/,..**%%%%##((#%%@@@@@@
((((**/(//**//,,*,/(,,%,.....,,,*,****,,...,,,,........,///,.,/%%&&%#(//(//(##%&
,*,,***//#(/(((###(/,*(*,.,,,,*,*/#%#(/((/,,,*,,.......*,,.,..%%%##((((///(#(/(#
*****//((((###/((*,,,,/*,,,,,*,***/((##(/**,,*,*......,/,...*(%%%%#####(((###(((
//,.,***((###((/*/((/*,*/,,,*/((*/(((((((//////*,.....,/****(%#####(((((((###(#%
(%#%(//((((##(((((((*((#(,,,*/(%*,******,,,,*/((,,,,,*/////((((((///**/****/**/(
/%@@&%%&&&&&%%((###(*/,,*(**((/(*,**/(*(/**,*/((/**///((%###(/(((((###%&%#(//***
****(&@@@@@&&&%%%%%%%&%#####(/(#(//(((/(////*/((//(#((#(*******/////((#%###%%(//
/,,,,*/#&@@@@@@@@@@@&#(/*(&#%###((/////****(((((((%###/*/**//*/(#((/((###(####((
((#%%#((%@@@@@@@@&%#/*,,,,*#&&&%(%(/(#(#(#(((%%%#%&#(*,..###%&&&&&&%&%&@@@@@@#&&
,,,,**(%@@@@@@@@@%//////(##%(#%&&&#%&&&&#%&%&&&&%(/*,,..../***,,****,**,,*/#//*,
****,...,(@@@@@(,*//***///((/,**/#%&&&@@&&&%(/***,,,,,....#((#(#%(##*,,*****//**
//**,*,..,#&@#*////*////(#%#(,,,****///((/***,,,,,,......######%(%#(##&#((((((((
/****/,../##//(//////(%&%%%%#,,,,,,****/***,,,,,,,.....%###%%#%&(######%&((####(
/////**((((###(//#%%%#%&%%%%%%,,,,*,****//***,,,,,,*%%%%%%##%#%&#(######&#(#%#(#
////**#%#((#%%%%%%%%%%%&&%%&&&&&&%(******//***#%%%%%%%%###%%%#%&%(#####%&##%(#%#
&@@@@@####%%%%%#%&%##%%%%%%%%%%%%&&&&&&&&&%%&%%%%%#%%#####%%##%%&((#(##%&%##(#%%
(%%#(######%%###%%####%########%&%%#%%%#%##%%#%%%##########%##%%%#((###%%%###%%%
####(#######%##%%%#############################################%%#((##%%%%###%%%