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maik
2021-09-24 20:04:45 +02:00
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content/writeups/google-ctf/2021/beginners-quest/4.md
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@@ -28,16 +28,6 @@ You’re taking a stroll in the lab, when Dr. Klostermann is calling your name:
[attachment.zip](/files/writeups/google-ctf/2021/beginners-quest/4/attachment.zip)
## Recon
When opening the attachment, we can find two files: `chal.c` and `pico.uf2`.
Before this challenge I had never heard of a `uf2` file, but from googling "pico.uf2", I found that it is probably a firmware file for the Paspberry Pi Pico.
While I would have loved to play around with that, I didn't have one at hand. So we'll have to do with the `chal.c` file (which is probably the file running in the firmware).
### `chal.c`
{{< code language="c" title="chal.c" isCollapsed="true" >}}
```c
@@ -205,6 +195,16 @@ int main(void)
{{< /code >}}
## Recon
When opening the attachment, we can find two files: `chal.c` and `pico.uf2`.
Before this challenge I had never heard of a `uf2` file, but from googling "pico.uf2", I found that it is probably a firmware file for the Paspberry Pi Pico.
While I would have loved to play around with that, I didn't have one at hand. So we'll have to do with the `chal.c` file (which is probably the file running in the firmware).
### `chal.c`
In this code, we see a lot of calls to the functions `gpio_set_mask()` and `gpio_clr_mask()`. When looking up what these to, we find [this documentation](https://raspberrypi.github.io/pico-sdk-doxygen/group__hardware__gpio.html):
{{< figure src="/img/writeups/google-ctf/2021/beginners-quest/4/doc-functions.png" title="Functions documentation" >}}