# **Disclaimer**
**All information is provided for educational purposes only. Follow these instructions at your own risk. Neither the authors nor their employer are responsible for any direct or consequential damage or loss arising from any person or organization acting or failing to act on the basis of information contained in this page.**
# Description
At the beginning of 2020, we discovered the Red Unlock technique that allows extracting [Intel Atom Microcode](https://en.wikipedia.org/wiki/Intel_Microcode). We were able to research the internal structure of the microcode and then x86 instruction implementation. Also, we recovered a format of microcode updates, algorithm and the encryption key used to protect the microcode (see [RC4](https://en.wikipedia.org/wiki/RC4)).
# FAQ
1. Can I make a custom microcode update?
No, you can't. Only decryption is supported, because microcode has an RSA signature for integrity protection.
2. What kind CPUs are supported?
A microcode update decryption key depends from CPU generation. We've extracted keys for Intel Gemini Lake (Goldmont Plus microarchitecture) and Intel Apolo Lake (Goldmont microarchitecture) generation. See [List of Supported CPUs](#list-of-supported-cpus)
3. How you had extracted the keys?
Using vulnerabilities in Intel TXE we had activated undocumented debugging mode called red unlock and extracted dumps of microcode directly from the CPU. We found the keys and algorithm inside.
4. Where can I find more information about it?
See our talks [Chip Red Pill: How We Achived to Execute Arbitrary Microcode Inside Intel Atom CPUs](https://www.youtube.com/watch?v=V1nJeV0Uq0M&ab_channel=OffensiveCon) from OffensiveCon22.
# Python
All our scripts are written on Python. We recommend using Python 3. The scripts require pycryptodome packet. To install pycryptodome, run the following command:
```
pip3 install pycryptodome
```
# Decrypting Microcode Update
Run the script **dec_uUpd_Atom_apl.py** for Apolo Lake CPUs:
```
C:\microcode>py -3 dec_uUpd_Atom_apl.py cpu506C9_plat03_ver00000040_2020-02-27_PRD_2FC3D618_.bin
Hash matched at length 0x3E00 (15872)
Data entropy: 6.898306
```
Run the script **dec_uUpd_xu_Atom_glp.py** for Gemini Lake CPUs:
```
C:\microcode>py -3 dec_uUpd_xu_Atom_glp.py cpu706A8_plat01_ver00000018_2020-06-09_PRD_1D9A5DFE.bin
Patch hash matched: enc size: 0x3480
Patch data entropy: 6.438890
XuCode hash matched: size: 0xed40
XuCode data entropy: 7.752765
```
# Unpacking decrypted XuCode (for Goldmont Plus only)
Run the script **XuUnp.py** for Goldmont Plus CPUs:
```
C:\microcode>py -3 XuUnp.py cpu706A8_plat01_ver00000018_2020-06-09_PRD_1D9A5DFE.bin.xu.dec
Processing cpu706A8_plat01_ver00000018_2020-06-09_PRD_1D9A5DFE.bin.xu.dec
. ELF at 0x28
. Parking: 0xD58+944
. XuRT: 0x16EC+D404
. Decompressing 54276 -> 101448, be patient...
+ Unpacked OK
```
# About XuCode
XuCode is the software part of SGX technology, there are ELF-files integrated in microcode update.
See: [XuCode: An Innovative Technology for Implementing Complex Instruction Flows](https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/secure-coding/xucode-implementing-complex-instruction-flows.html)
# List of Supported CPUs
The microcode update can be decrypted for following CPUs:
| Processor Model | Microarchitecture | SGX / XuCode support |
| ------ | ------ | ------ |
| Pentium J4205 | Goldmont, Apollo Lake | - |
| Celeron J3455 | Goldmont, Apollo Lake | - |
| Celeron J3355 | Goldmont, Apollo Lake | - |
| Pentium N4200 | Goldmont, Apollo Lake | - |
| Celeron N3450 | Goldmont, Apollo Lake | - |
| Celeron N3350 | Goldmont, Apollo Lake | - |
| Atom x7 E3940 | Goldmont, Apollo Lake | - |
| Atom x5 E3930 | Goldmont, Apollo Lake | - |
| Atom x7 A3960 | Goldmont, Apollo Lake | - |
| Atom x7 A3950 | Goldmont, Apollo Lake | - |
| Atom x5 A3940 | Goldmont, Apollo Lake | - |
| Atom x5 A3930 | Goldmont, Apollo Lake | - |
| Atom C3958 | Goldmont, Denverton | - |
| Atom C3955 | Goldmont, Denverton | - |
| Atom C3858 | Goldmont, Denverton | - |
| Atom C3850 | Goldmont, Denverton | - |
| Atom C3830 | Goldmont, Denverton | - |
| Atom C3808 | Goldmont, Denverton | - |
| Atom C3758 | Goldmont, Denverton | - |
| Atom C3750 | Goldmont, Denverton | - |
| Atom C3708 | Goldmont, Denverton | - |
| Atom C3558 | Goldmont, Denverton | - |
| Atom C3538 | Goldmont, Denverton | - |
| Atom C3508 | Goldmont, Denverton | - |
| Atom C3338 | Goldmont, Denverton | - |
| Atom C3308 | Goldmont, Denverton | - |
| Pentium Silver J5005 | Goldmont Plus, Gemini Lake | + |
| Celeron J4105 | Goldmont Plus, Gemini Lake | + |
| Celeron J4005 | Goldmont Plus, Gemini Lake | + |
| Pentium Silver N5000 | Goldmont Plus, Gemini Lake | + |
| Celeron N4100 | Goldmont Plus, Gemini Lake | + |
| Celeron N4000 | Goldmont Plus, Gemini Lake | + |
| Pentium Silver N5030 | Goldmont Plus, Gemini Lake Refresh | + |
| Celeron N4120 | Goldmont Plus, Gemini Lake Refresh | + |
| Celeron N4020 | Goldmont Plus, Gemini Lake Refresh | + |
# Research Team
Mark Ermolov ([@\_markel___][1])
Maxim Goryachy ([@h0t_max][2])
Dmitry Sklyarov ([@_Dmit][3])
[1]: https://twitter.com/_markel___
[2]: https://twitter.com/h0t_max
[3]: https://twitter.com/_Dmit
