Help with getting saved wireless networks passwords with libnm

[Flavio Collocola <flavius c 1999 gmail com>]

Hi all,

I'm trying to port my Windows program WiFi Password Recovery to Linux. 

WiFi Password Recovery is a simple tool which scans all wireless networks stored on the device and then returns their info (such as SSID, Auth algorithm, password...).

To keep portability I'm developing it in C++ using wxWidgets library. In particular on Linux I'm trying to use libnm to interface the program with NetworkManager. Before starting the port I decided to write a small C console program to learn libnm API and NetworkManager basis.

I'm trying to get the passwords of all wireless networks saved on Ubuntu using libnm but when i call the function nm_setting_wireless_security_get_psk it returns null. It doesn't work with debug dump functions of libnm too. I think I should do something with NMSecretAgentOld but I don't understand what exactly and how. I also did not find any example on the Internet. I slightly modified a C example about using libnm available on internet and this is my current test code:

/*
* The example shows how to list connections.  Contrast this example with
* list-connections-gdbus.c, which is a bit lower level and talks directly to NM
* using GDBus.
*
* Compile with:
*   gcc -Wall test.cpp -o test `pkg-config --libs --cflags libnm`
*/

#include <glib.h>
#include <stdio.h>
#include <stdlib.h>

#include <NetworkManager.h>
#include <nm-secret-agent-old.h>

/* Print details of connection */
static void
show_connection (NMConnection *connection)
{
   printf("--- CONNECTION ---\n");
   NMSettingWireless* s_con;
   NMSettingWirelessSecurity* wifiSec;
   const char* interfce;
   interfce = nm_connection_get_interface_name(connection);
   s_con = nm_connection_get_setting_wireless(connection);
   if (s_con) {
       GBytes* ssidBytes = nm_setting_wireless_get_ssid(s_con);
       const char* ssid = nm_utils_ssid_to_utf8((guint8 *)g_bytes_get_data(ssidBytes, NULL), g_bytes_get_size(ssidBytes));
       printf("SSID: %s\nInterface: %s\n", ssid, interfce);
       wifiSec = nm_connection_get_setting_wireless_security(connection);
       if(wifiSec){
           const char* auth = nm_setting_wireless_security_get_auth_alg(wifiSec);
           const char* encrypt = nm_setting_wireless_security_get_key_mgmt(wifiSec);
           const char* psk = nm_setting_wireless_security_get_psk(wifiSec); //THIS RETURNS NULL! BUT THE WPA-PSK PASSWORD IS SET!
           printf("Auth: %s\nEncryption: %s\nPassword: %s\n", auth, encrypt, psk);
           nm_connection_dump(connection); //Also in debug dump no password field
       }
   }
}

int
main (int argc, char *argv[])
{
   NMClient *client;
   GError *error = NULL;
   const GPtrArray *connections;
   int i;

#if !GLIB_CHECK_VERSION (2, 35, 0)
   /* Initialize GType system */
   g_type_init ();
#endif
   if (!(client = nm_client_new (NULL, &error))) {
       g_message ("Error: Could not connect to NetworkManager: %s.", error->message);
       g_error_free (error);
       return EXIT_FAILURE;
   }

   if (!nm_client_get_nm_running (client)) {
       g_message ("Error: Can't obtain connections: NetworkManager is not running.");
       return EXIT_FAILURE;
   }
   /* Now the connections can be listed. */
   connections = nm_client_get_connections (client);

   printf ("Connections:\n===================\n");

   for (i = 0; i < connections->len; i++)
       show_connection ((NMConnection*) connections->pdata[i]);

   g_object_unref (client);

   return EXIT_SUCCESS;
}

This is the interesting part of program output: Program output image
And this is the etc/NetworkManager/system_connections dump (where the psk field is set): Wireless Network file dump image

Thanks in advance and Best Regards,

Flavio