Full Code of chrivers/samsung-firmware-magic for AI

Repository: chrivers/samsung-firmware-magic
Branch: master
Commit: df6463b95b9e
Files: 2
Total size: 5.7 KB

Directory structure:
gitextract_psm9xlw7/

├── README.md
└── samsung-magic.py

================================================
FILE CONTENTS
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================================================
FILE: README.md
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Samsung Firmware Magic
======================

Samsung distributes firmware updates for their SSDs for either "Windows" or
"Mac". Ironically, both of these are bootable Linux `.iso` files, containing the
actual firmware and update program.

The `.iso` files can be unpacked, but ultimately we end up with an obfuscated
binary blob, even for the meta information.

For the upstream file downloads, see

    https://www.samsung.com/semiconductor/minisite/ssd/download/tools/

Out of curiosity, I decided to create a decryption tool for this obfuscated
format, which is found in this repository.

Unpacking iso image to firmware blob
------------------------------------

First, we download a firmware iso:

    `wget http://downloadcenter.samsung.com/content/FM/201711/20171102105105735/Samsung_SSD_850_PRO_EXM04B6Q_Win.iso`

Next, we unpack the relevant file from the iso, the `initrd`:

    `7z x Samsung_SSD_850_PRO_EXM04B6Q_Win.iso initrd`

This file is a gzip-compressed cpio archive, so use 7z to strip gzip:

    `7z x initrd`

This produces `initrd~`, containing the uncompressed contents. From here we
extract the directory of interest, `root/fumagician`:

    `7z -ofw x 'initrd~' root/fumagician`

This creates `fw/root/fumagician` in the current directory:

```
$ cd fw/root/fumagician
$ ls -l
total 5408
-rw-rw-r-- 1 user user    2124 1971-03-22 19:52 DSRD.enc
-rw-rw-r-- 1 user user 4752867 1971-03-22 19:52 EXM04B6Q.enc
-rw-rw-r-- 1 user user  772516 2016-10-14 10:42 fumagician
-rw-rw-r-- 1 user user     290 2016-10-14 10:42 fumagician.sh
```

The files `DSRD.enc` (xml list of firmwares) and `EXM04B6Q.enc` (firmwares)
are the obfuscated files, that we can now decrypt.

Decrypting firmware blob
------------------------

The included `decode.py` script will unpack these `.enc` files, like so:

```shell
## show xml on stdout:
$ ./samsung-magic.py < fw/root/fumagician/DSRD.enc

## decrypt firmware to file:
$ ./samsung-magic.py < fw/root/fumagician/EXM04B6Q.enc > EXM04B6Q.bin
```

Seemingly, the folks at Samsung are huge fans of nesting things, because the
decrypted `EXM04B6Q.bin` file is actually a zip file, containing encrypted
firmware files:

```shell
$ unzip -l EXM04B6Q.bin
Archive:  EXM04B6Q.bin
  Length      Date    Time    Name
---------  ---------- -----   ----
  1048576  2017-02-19 10:41   EXM04B6Q_10170217.enc
  1048576  2017-02-19 10:41   EXM04B6Q_20170203.enc
  1048576  2017-02-19 10:41   EXM04B6Q_30170203.enc
  1048576  2017-02-19 10:41   EXM04B6Q_40170902.enc
  1048576  2017-02-19 10:41   EXM04B6Q_50170208.enc
  1048576  2017-02-19 10:41   EXM04B6Q_60170208.enc
---------                     -------
  6291456                     6 files
```

Luckily, the encryption is exactly the same, so `samsung-magic.py` can decrypt
these as well:

```
$ unzip EXM04B6Q.bin
$ ./samsung-magic.py < EXM04B6Q_10170217.enc > EXM04B6Q_10170217.bin
```

Now, at last, we have the raw firmware.

Enjoy!


================================================
FILE: samsung-magic.py
================================================
#!/usr/bin/env python3

from sys import stdin, stdout
from struct import pack
from Crypto.Cipher import AES

## this is the shuffle map that samsung uses
shuffle = bytes([
           0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
           0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x30, 0x31, 0x32, 0x33,
           0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D,
           0x3E, 0x3F, 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
           0x58, 0x59, 0x5A, 0x5B, 0x5C, 0x5D, 0x5E, 0x5F, 0x70, 0x71,
           0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B,
           0x7C, 0x7D, 0x7E, 0x7F, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95,
           0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, 0x9E, 0x9F,
           0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9,
           0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF, 0xD0, 0xD1, 0xD2, 0xD3,
           0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD,
           0xDE, 0xDF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7,
           0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF, 0xE0, 0xE1,
           0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB,
           0xEC, 0xED, 0xEE, 0xEF, 0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5,
           0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF,
           0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9,
           0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0x80, 0x81, 0x82, 0x83,
           0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D,
           0x8E, 0x8F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
           0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x40, 0x41,
           0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B,
           0x4C, 0x4D, 0x4E, 0x4F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25,
           0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
           0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
           0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F
])

## generate reverse map
lookup = bytes(shuffle.find(i) for i in range(256))

## utility functions
def xor(s1, s2):
    return bytes(a ^ b for a,b in zip(s1, s2))

def unshuffle(s):
    return bytes(lookup[c] for c in s)

## crypto constants
iv0 = bytes.fromhex("8ce82eefbea0da3c44699ed7")
key = bytes.fromhex("56e47a38c5598974bc46903dba290349")
ctr = 0
aes = AES.new(key, AES.MODE_ECB)

while True:
    ## read next aes block
    blk = stdin.buffer.read(16)
    if len(blk) == 0:
        break

    ## samsung arbitrarily resets the counter every 32 blocks
    ctr = (ctr % 32) + 1

    iv = iv0 + pack(">I", ctr)

    ## we are using ECB mode to simulate the 32-block CTR mode
    ## use .encrypt() instead of .decrypt() for this reason
    xblk = aes.encrypt(iv)

    ## decrypt and unshufflee to get our result
    res = unshuffle(xor(xblk, blk))

    stdout.buffer.write(res)