Week 10

Please sit on the right half of the room

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Firmware

What is firmware?

Broad term for low-level software that has direct access to a device's hardware.

  • Common examples include
    • BIOS/UEFI: Initializes hardware and loads the operating system
    • IOT: Printer's, cameras, routers, switches
    • Phone Components: GPS, sensors, or battery
    • Appliances: Washing machines, refrigerators, microwaves

Firmware Types

There's a large diversity of firmware architecture since it's often customized to the hardware. Three broad categories include:

  • Bare Metal: A single program built to run without an operating system (think arduino program)
  • Real-time Operating System (RTOS): A lightweight operating system with memory management, scheduling
  • Linux-based: Either a stripped-down linux distribution or the linux kernel embedded in a custom operating system

 

Since firmware is often developed for microprocessors, they often use the MIPS or ARM instruction sets.

Obtaining Firmware

https://support.linksys.com/kb/article/81-en/

Image may include

  • Operating system
  • File system
  • User applications

Firmware Extraction

Firmware is often distributed as binary blobs (img files) and it's up to us to extract useful files from them.

00000000: AA BB CC DD EE FF 00 11 22 33 44 55 66 77 88 99  ........"3DUfw..
00000010: 00 11 22 33 44 55 66 77 88 99 AA BB CC DD EE FF  .."3DUfw........
00000020: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00001000: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00001010: FF EE DD CC BB AA 99 88 77 66 55 44 33 22 11 00  ........wfUD3"..
00001020: 89 50 4E 47 0D 0A 1A 0A 00 00 00 0D 49 48 44 52  .PNG......IHDR
00002000: 00 00 02 80 00 00 01 E0 08 06 00 00 00 75 71 3C  ..............uq<
00002010: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00002020: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00003000: 4C 00 00 00 04 67 41 4D 41 00 00 B1 8F 0B FC 61  L....gAMA......a
00003010: FF D8 FF E0 00 10 4A 46 49 46 00 01 02 01 00 60  ......JFIF.....`
00003020: 00 60 00 00 FF DB 00 43 00 08 06 06 07 06 05 08  .`.....C........
00004000: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00004010: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00004020: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00005000: 50 4B 03 04 14 00 06 00 08 00 00 00 21 00 B3 AC  PK..........!...
00005010: 8D 4E 00 00 00 00 00 00 00 00 00 00 08 00 1C 00  .N..............
00005020: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00006000: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00006010: 74 65 73 74 2E 74 78 74 55 54 09 00 03 E8 3D 75  test.txtUT....=u
00006020: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00007000: 7F 45 4C 46 02 01 01 00 00 00 00 00 00 00 00 00  .ELF............
00007010: 02 00 3E 00 01 00 00 00 78 00 40 00 00 00 00 00  ..>.....x.@.....
00007020: 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  @...............
00008000: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00008010: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................
00008020: 07 07 07 09 09 08 0A 0C 14 0D 0C 0B 0B 0C 19 12  ................


dd if=<firmware> of=<outfile> bs=<block size> skip=<start> count=<size>
dd if=file.bin of=out.png bs=1 skip=4128 count=8176
dd if=file.bin of=out.jpg bs=1 skip=12304 count=4112
dd if=file.bin of=out.zip bs=1 skip=20480 count=8192

Firmware Extraction

There exist tools that attempt to automate this process

Binwalk

Unblob

Questions?

Lab 1

Firmware Extraction

Firmware Analysis

Linux Firmware Triage

When enumerating linux-based firmware, there's a variety of artifacts to look for.

  • System Architecture: x86, ARM, MIPS
  • Authentication: ssh keys, shadow file, etc.
  • Versions: busybox, linux kernel version
  • User Applications: web server, ftp server
    • Are there any known vulnerabilities for the user applications or OS version?

Emulation

It can also be helpful to run different files included on the file system. If the firmware architecture is different from your host machine, you must emulate the binaries you run. QEMU is the industry standard open-source emulator.

There are two main flavors of emulation:

  • User Mode: Emulate individual processes
  • Full System: Emulates the entire operating system with virtual hardware

Lab 2

Firmware Analysis

HW

Firmware Analysis

Week 10

By Chase Kanipe

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Week 10

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