Determinare il firmware MCU dall'immagine binaria

Question

Problema difficile: provare a decodificare un controller CANBUS per il quale posso scaricare il firmware (per quanto ne so, immagine binaria, non ELF) ma non so quale MCU utilizzi. binwalk, r2non darmi niente di utile. I codici operativi Binwalk corrispondono a mipsel ma le firme delle funzioni sono spazzatura.

Cosa posso fare per determinare MCU dal firmware?

Answer 1

Sembra essere un codice macchina MIPS little-endian a 32 bit.

---

Innanzitutto, il file è stato convertito da .hex a binario tramite

$ objcopy --input-target=ihex --output-target=binary FORD_P5_STEER_RevA_v1.2.0.hex FORD_P5_STEER_RevA_v1.2.0.bin

Dopo aver esaminato un binwalkgrafico dell'entropia e un dump esadecimale, ho tagliato i primi 0x00021330byte, perché quasi tutto ciò che segue è solo 0x00 byte.

000212f0  5f 50 35 20 53 74 65 65  72 00 00 00 20 24 00 00  |_P5 Steer... $..|
00021300  00 04 08 10 14 18 00 00  08 00 e0 03 00 60 62 41  |.............`bA|
00021310  08 00 e0 03 20 60 62 41  08 00 e0 03 00 00 00 00  |.... `bA........|
00021320  08 00 e0 03 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00021330  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................| <--\
*                                                                                 |-- Huge gap
00071e40  01 00 00 00 02 00 00 00  00 00 00 00 46 4f 52 44  |............FORD| <--/
00071e50  20 50 35 20 53 74 65 65  72 69 6e 67 20 45 6d 75  | P5 Steering Emu|
00071e60  6c 61 74 6f 72 20 28 46  4f 52 44 5f 50 35 5f 53  |lator (FORD_P5_S|
00071e70  54 45 45 52 29 20 52 65  76 41 00 00 00 00 00 00  |TEER) RevA......|
00071e80  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
02bf9e80  00 9d 1f 3c 70 79 ff 37  08 00 e0 03 00 00 00 00  |...<py.7........|
02bf9e90  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
02bfce70  ff ff ff 3e d9 79 f9 ff  5b 0e 66 ff ff ff ff 7f  |...>.y..[.f.....|
02bfce80

Risultati ISAdetect :

{
  "prediction": {
    "wordsize": 32,
    "endianness": "little",
    "architecture": "mips"
  },
  "prediction_probability": 0.81
}

Per confermare, ho estratto il codice macchina dalla slice e l'ho confrontato con un riferimento:

Le distribuzioni del valore in byte corrispondono strettamente.

Answer 2

È davvero un codice litte-endian MIPS valido:

seg000:1D0121F0 A8 FF BD 27                 addiu   $sp, -0x58
seg000:1D0121F4 04 00 A1 AF                 sw      $at, 0x58+var_54($sp)
seg000:1D0121F8 08 00 A2 AF                 sw      $v0, 0x58+var_50($sp)
seg000:1D0121FC 0C 00 A3 AF                 sw      $v1, 0x58+var_4C($sp)
seg000:1D012200 10 00 A4 AF                 sw      $a0, 0x58+var_48($sp)
seg000:1D012204 14 00 A5 AF                 sw      $a1, 0x58+var_44($sp)
seg000:1D012208 18 00 A6 AF                 sw      $a2, 0x58+var_40($sp)
seg000:1D01220C 1C 00 A7 AF                 sw      $a3, 0x58+var_3C($sp)
seg000:1D012210 20 00 A8 AF                 sw      $t0, 0x58+var_38($sp)
seg000:1D012214 24 00 A9 AF                 sw      $t1, 0x58+var_34($sp)
seg000:1D012218 28 00 AA AF                 sw      $t2, 0x58+var_30($sp)
seg000:1D01221C 2C 00 AB AF                 sw      $t3, 0x58+var_2C($sp)
seg000:1D012220 30 00 AC AF                 sw      $t4, 0x58+var_28($sp)
seg000:1D012224 34 00 AD AF                 sw      $t5, 0x58+var_24($sp)
seg000:1D012228 38 00 AE AF                 sw      $t6, 0x58+var_20($sp)
seg000:1D01222C 3C 00 AF AF                 sw      $t7, 0x58+var_1C($sp)
seg000:1D012230 40 00 B8 AF                 sw      $t8, 0x58+var_18($sp)
seg000:1D012234 44 00 B9 AF                 sw      $t9, 0x58+var_14($sp)
seg000:1D012238 48 00 BF AF                 sw      $ra, 0x58+var_10($sp)
seg000:1D01223C 12 40 00 00                 mflo    $t0
seg000:1D012240 4C 00 A8 AF                 sw      $t0, 0x58+var_C($sp)
seg000:1D012244 10 40 00 00                 mfhi    $t0
seg000:1D012248 50 00 A8 AF                 sw      $t0, 0x58+var_8($sp)
seg000:1D01224C 01 9D 1A 3C+                li      $k0, 0x9D012CA4
seg000:1D01224C A4 2C 5A 27
seg000:1D012254 00 00 00 00                 nop
seg000:1D012258 00 68 04 40                 mfc0    $a0, Cause       # Cause of last exception
seg000:1D01225C 00 60 05 40                 mfc0    $a1, SR          # Status register
seg000:1D012260 09 F8 40 03                 jalr    $k0
seg000:1D012264 00 00 00 00                 nop

Sospetto che il dispositivo stia utilizzando qualcosa della serie PIC32 di Microchip .