NK_list_devices() hangs with plugged in Nitrokey FIDO2 device

[daringer]

Bug report: The NK_list_devices() C-API call, while a Nitrokey FIDO2 device is plugged in, will never return and load one cpu.

How to reproduce:

• make sure you have a Nitrokey FIDO2 and a Nitrokey Pro (2) / Storage (2) plugged in
• libnitrokey and its headers must be installed
• create a file (and save it as nk.cc) with the following content:

#include <libnitrokey/NK_C_API.h>
#include <iostream>

using namespace std;

int main() {
	struct NK_device_info* x = NK_list_devices();
	cout << x->model << endl;
	cout << x->path << endl;
	cout << x->serial_number << endl;
}

• compile it using: g++ nk.cc -o nk -lnitrokey -I/usr/include
• run it: ./nk

Observed behavior: The executable will hang inside the NK_list_devices() call

Expected behavior: The executable should return immediately, while ignoring any other devices

Environment:

• Arch Linux (Kernel 5.9.12-arch1-1, AMD64)
• libnitrokey version 3.6 (package release 1)
• Nitrokey FIDO2 & Nitrokey Pro 2

[robin-nitrokey]

I have the same issue with libnitrokey 3.6 on Debian with kernel 5.10.0-0.bpo.4-amd64.