nk.nb0 windows ce 7 reverse engineering

[FernandoAl]

I would like to try to reverse a firmware of an old car radio that has an arm cpu and windows ce 7. I have extracted all the files from the firmware including an nk.nb0 image but if I try to open it directly with qemu, the image is not loaded.
Is there a way to try to open this nb0 image or recreate the same environment on which to run the files to be examined?
Thanks

[chants]

DeepSeek response looks accurate and useful:

Reversing a Windows CE 7 firmware for an ARM-based car radio is an interesting challenge! The `nk.nb0` file is a raw memory image of the OS, and running it directly in QEMU requires proper configuration. Here's how you can approach this:

---

### **1. Convert `nk.nb0` to a Loadable Format**
The `.nb0` file is a raw binary dump of the OS image. You may need to convert it to a format QEMU can boot (like a `.bin` or `.img` file). Sometimes, `nk.nb0` can be directly loaded, but you might need offsets.

- Try loading it in QEMU with the correct memory offset:
```bash
qemu-system-arm -M versatilepb -kernel nk.nb0 -m 256 -nographic
```
(Adjust `-M` for the correct machine type; `versatilepb` is common for ARM.)

- If that fails, try extracting components using **DumpKernel** (WinCE tool) or manually parsing the file structure.

---

### **2. Use a Windows CE 7 BSP (Board Support Package)**
Since it's a car radio, it likely uses a custom BSP. However, you can try a generic **CE 7 emulator**:
- Download the **Windows Embedded Compact 7** evaluation kit (if available).
- Use **Platform Builder** to generate a compatible QEMU image.
- Replace parts of the image with your extracted files.

---

### **3. Extract & Analyze Files**
Since you already extracted files:
- Look for **`NK.BIN`** (compressed version of `nk.nb0`). If present, use **`viewbin`** (from CE tools) to inspect it:
```bash
viewbin nk.bin
```
- Check for **`XIP` (Execute-In-Place) regions** where the kernel runs.
- Use **IDA Pro/Ghidra** to disassemble `nk.nb0` (set CPU to ARM).

---

### **4. Emulate with QEMU & CE 7 BSP**
If you can't boot `nk.nb0` directly:
1. **Find the correct QEMU machine type** (e.g., `realview`, `vexpress-a9`).
2. **Load the CE 7 kernel first**, then your filesystem:
```bash
qemu-system-arm -M realview-eb -kernel ce7_kernel.bin -initrd nk.nb0 -m 256
```
3. If the radio uses **U-Boot**, chain-load it first.

---

### **5. Reverse Engineer the Hardware**
- Identify the **exact ARM CPU** (e.g., ARM926EJ-S, Cortex-A8).
- Check if the vendor left a **serial/UART debug port** on the PCB.
- Dump the **NAND/NOR flash** directly if possible (with a programmer).

---

### **Tools to Help**
- **`cemainfo`** – Inspects `nk.bin/nb0`.
- **`bin2nb0`** – Converts between formats.
- **`IDA Pro`** + **ARM plugin** – Static analysis.
- **`Ghidra`** – Free alternative for ARM disassembly.
- **`QEMU`** + **`GDB`** – Debug execution.

---

### **Final Notes**
- WinCE 7 is **not open-source**, so full emulation is hard.
- If the radio uses **secure boot**, you may need to bypass checks.
- Try **virtualizing** instead of emulating (e.g., **UniSoft VirtuCE**).

Would you happen to know the exact ARM CPU model or have any boot logs from the radio? That could help narrow down the QEMU setup. Let me know how it goes!