Hardware Backdooring is practical
Jonathan Brossard (Toucan System) Florentin Demetrescu (Cassidian)
Hardware Backdooring is practical
Jonathan Brossard (Toucan System) Florentin Demetrescu (Cassidian)
DISCLAIMER
We are not « terrorists ». We won't release our PoC backdoor.
The x86 architecture is plagued by legacy. Governments know. The rest of the industry : not so much.
There is a need to discuss the problems in order to find solutions...
This is belived to be order of magnitudes better over existing backdoors/malware
Agenda
Motivation : state level backdooring ?
Coreboot & x86 architecture
Flashing Coreboot on a motherboard
State of the art in rootkitting, romkitting
Introducing Rakshasa
Evil remote carnal pwnage (of death)
Why cryptography (Truecrypt/Bitlocker/TPM) won't save us...
Could a state (eg : China) backdoor
all new computers on earth ?
A bit of x86 architecture
Demo : flashing Coreboot on a
motherboard
State of the art, previous work
Previous work
Early 80s : Brain virus, targets the MBR
80s, 90s : thousands of such viruses
2007, John Heasman (NGS Software) Blackhat US: backdoor EFI bootloader
2009, Anibal Saco and Alfredo Ortega (Core security), CanSecWest : patch/flash a
2009, Kleissner, Blackhat US : Stoned bootkit. Bootkit Windows, Truecrypt. Load arbitrary unsigned kernel module.
2010, Kumar and Kumar (HITB Malaysia) : vbootkit bootkitting of Windows 7.
Piotr Bania, Konboot : bootkit any Windows (32/64b)
DEMO : Silently Bootkitting windows
2008
Introducing Rakshasa
Goals : create the perfect backdoor
Persistant
Stealth (virtually undetectable)
Portable (OS independant)
Remote access, remote updates
State level quality : plausible deniability, non attribution
Cross network perimeters (firewalls...)
Redundancy
Rakshasa : design
Core components :
Coreboot SeaBios iPXE payloads
Built on top of free software : portability, non attribution, cheap dev (~4 weeks of work), really hard to detect (without false positives).
Payload : Reverse Engineered/Refactored konboot payload (2 days of work).
Rakshasa
Flash the BIOS (Coreboot + PCI roms such as iPXE)
Flash the network card or any other PCI device (redundancy)
Boot a payload over the network (bootkit)
Boot a payload over wifi/wimax (breach the network perimeter, bypasses network detection, I(P|D)S )
Remotely reflash the BIOS/network card if necessary
Rakshasa : embedded features
Remove NX bit (from BIOS or PCI) =>executable heap/stack.
Remove CPU updates (microcodes)
Remove
=> Permantent lowering of the security level on any OS. Welcome back to the security level of 1999.
=> Persistant, even if HD is remove/restored.
Optionally : Disable ASLR (bootkitting) by patching the seed in kernel land on the fly on Windows.
Rakshasa : remote payload
Bootkit future Oses
Update/remove/reflash firmwares (PCI, BIOS)
Currently capable of Bootkitting any version of Windows (32b/64b)
Use a minimal linux initrd in case we want to mount/modify the filesystem (/etc/shadow on any UNIX like, add new account with ADMIN privileges on Windows, enable remote desktop
– possibly enable dual remote desktop on Windows XP Pro by patching 2 dlls...)
Rakshasa : stealthness
We don't touch the disk. 0 evidence on the filesystem.
We can remotely boot from an alternate payload or even OS : fake Truecrypt/Bitlocker prompt !
Optionally boot from a WIFI/WMAX stack : 0 network evidence on the LAN.
Fake BIOS menus if necessary. We use an embedded CMOS image. We can use the real CMOS nvram to store encryption keys/backdoor states between reboots.
Rakshasa : why using
Coreboot/SeaBios/iPXE is the good
approach
Portability : benefit from all the gory reverse engineering work already done !
Awesome modularity : embbed existing payloads (as floppy or cdrom images) and PCI roms directly in the main Coreboot rom !
Eg : bruteforce bootloaders (Brossard, H2HC 2010), bootkits without modification.
Network stack : ip/udp/tcp, dns, http(s), tftp,
ftp... make your own (tcp over dns? Over ntp ?)
PCI rom from scratch (asm)
section .text
;Bios expension ROM header
db 0x55 |
; Signature |
db 0xaa |
; Signature |
db 17 |
; number of sectors |
DEMO : Evil remote carnal pwnage
(of death)
I can write blogs too... Muhahahaha...
Rakshasa
Flash the BIOS (Coreboot + PCI roms such as iPXE)
Flash the network card or any other PCI device (redundancy)
Boot a payload over the network (bootkit)
Boot a payload over wifi/wimax (breach the network perimeter, bypasses network detection, I(P|D)S )
Remotely reflash the BIOS/network card if necessary
How to properly build a botnet ?
HTTPS + assymetric cryptography (client side certificates, signed updates)
Fastflux and/or precomputed IP addresses
If Microsoft can do secure remote updates, so can a malware !
Avoid DNS take overs by law enforcement agencies by directing the C&C rotatively on innocent web sites (are you gonna shut down Google.com?), use assymetric crypto to push updates.
Why crypto won't save you...
Why crypto won't save you...
We can fake the bootking/password prompt by booting a remote OS (Truecrypt/Bitlocker)
Once we know the password, the BIOS backdoor can emulate keyboard typing in 16b real mode by programming the keyboard/motherboard PIC microcontrolers (Brossard, Defcon 2008)
If necessary, patch back original BIOS/firmwares remotely.
How about Avs ??
Putting an AV on a server to protect against unknown threats is purely cosmetic.
You may as well put lipstick on your servers...
Example : 3 years old bootkit
Example : 3 years old bootkit (+
simple packer)
Realistic attack scenarii
Realistic attack scenarii
Physical access :
Anybody in the supply chain can backdoor your hardware. Period.
Flash from a bootable USB stick (< 3mins).
Remote root compromise : If (OS == Linux) {
flash_bios;
} else { Pivot_over_the_MBR ;
}
Realistic attack scenarii
Purchase
BONUS : Backdooring the
datacenter
Remediation
Remediation (leads)
Flash any firmware uppon reception of new hardware with open source software
Perform checksums of all firmwares by physically extracting them (FPGA..) : costly !
Verify the integrity of all firmwares from time to time
Update forensics best practices :
1)Include firmwares in SoW
2)Throw away your computer in case of intrusion
Even then... not entirely satisfying : the backdoor can flash the original firmwares back remotely.
Side note on remote flashing
BIOS flashing isn't a problem : the flasher (Linux based) is universal.
PCI roms flashing is (a bit of) a problem : vendor dependant...
Detecting network card
manufacturer from the remote C&C
IPXE allows scripting. Eg : sending the MAC address as an URL parameter.
From the MAC, get the OUI number serverside.
From the OUI number, deduce manufacturer
Send the proper flashing tool as an embedded OS to the backdoor...
Questions ?