Merge pull request #237 from Nibba2018/save-wifi-c

Write Saved WiFi networks and their passwords in a text file in C

Author: tejan-singh

Diff for: C/Wifi-Passwords/README.md

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+# Saved Wifi Passwords
+A cross platform C program which queries and writes all saved WiFi networks and their passwords in a text file.
+
+## Executing the Program:
+* Compile the program: `gcc gen-wifi.c`.
+* On windows, do `a.exe`.
+* On Linux, do `./a.out`.
+
+**Sample use case:**
+Let's say you want to share the your wifi password to your friend but you dont remember it clearly then you can use this script to find the saved password.
+
+**Contents of `wifi_password.txt`:**
+```txt
+<SSID 1>:<password>
+<SSID 2>:<password>
+.
+.
+.
+```

Diff for: C/Wifi-Passwords/gen-wifi.c

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+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+
+// Add a global variable to skip the first line of shell output in windows.
+int first_skip = 1;
+
+// Function to format shell output.
+char* formatLog(char *buffer)
+{
+    // Check which OS the script is currently running on.
+    #ifdef __linux__
+
+        // Tokenize the script using `:` as a delimiter.
+        char *token_1 = strtok(buffer, ":");
+        char *token_2 = strtok(NULL, ":");
+
+        // Extract the password tokenizing through `=`.
+        char *ssid_part = strrchr(token_1, '/');
+        char *psk = strrchr(token_2, '=');
+
+        // Extract the ssid.
+        char *ssid = strtok(ssid_part+1, ".");
+
+        // Some formatting to make it more readable.
+        psk += 1;
+        strcat(ssid, ":");
+        strcat(ssid, psk);
+
+        return ssid;
+
+    #elif _WIN32
+
+        #include<ctype.h>
+
+        // Skip the first line of shell output.
+        if(first_skip == 1)
+        {   first_skip = 0;
+            return "";
+        }
+
+        // Extract ssid by tokenizing through `:`.
+        char *ssid = strtok(buffer, ":");
+        ssid = strtok(NULL, ": ");
+
+        // Trim trailing whitespaces.
+        char *end;
+        end = ssid + strlen(ssid) - 1;
+        while(end > ssid && isspace((unsigned char)*end)) end--;
+        end[1] = '\0';
+
+        // Create a file pointer to access a different shell.
+        FILE *shell_ptr;
+
+        // Format the shell command to extract the password.
+        char psk_command[1024];
+        sprintf(psk_command, "netsh wlan show profile %s key=clear | findstr \"Key Content\"", ssid);
+        shell_ptr = popen(psk_command, "r");
+
+        // Create a buffer to read the data.
+        char psk_temp[1024];
+        fgets(psk_temp, sizeof(psk_temp), shell_ptr);
+
+        // Extract the password.
+        char *psk = strtok(psk_temp, ":");
+        psk = strtok(NULL, ": ");
+
+        // Ignore passwords which are null.
+        if((psk != NULL) && (psk[0] == '\0') && (strcmp(psk, "1") != 0))
+        {
+            end = psk + strlen(psk) - 1;
+            while(end > psk && isspace((unsigned char)*end)) end--;
+            end[1] = '\0';
+        }
+
+        // Set open networks as [Open Network]
+        if(strlen(psk) == 2)
+            psk = "[Open Network]";
+
+        // Close unused shell pointer.
+        pclose(shell_ptr);
+
+        // Format output for better readability.
+        strcat(ssid, ":");
+        strcat(ssid, psk);
+        return ssid;
+
+    #endif
+}
+
+int main()
+{
+    /*
+    Create file pointers for:
+    - Reading information from shell.
+    - Writing to a Text File.
+
+    Also create a buffer to read the shell output, line by line.
+    */
+    FILE *shell_op, *fptr;
+    char buffer[3096];
+
+    // Check which OS the program is currently being run on.
+    #ifdef _WIN32
+
+        char *command = "netsh wlan show profile | findstr \":\"";
+
+    #elif __linux__
+
+        char *command = "sudo grep -r '^psk=' /etc/NetworkManager/system-connections/";
+
+    #endif
+
+    // Open a text file for writing.
+    fptr = fopen("wifi_password.txt", "w");
+
+    // Check if file was created or not.
+    if(fptr == NULL)
+    {
+        puts("Error creating file...");
+        exit(1);
+    }
+
+    // Spawn a shell process to communitcate with OS.
+    shell_op = popen(command, "r");
+    if(shell_op == NULL)
+    {
+        puts("Failed to communicate with shell.");
+        exit(1);
+    }
+
+    // Read shell output line by line.
+    while (fgets(buffer, sizeof(buffer), shell_op) != NULL)
+    {
+        // Format shell output for better readability.
+        char *formattedLog = formatLog(buffer);
+
+        // Write the formated information to the file.
+        fprintf(fptr, "%s", formattedLog);
+    }
+
+
+    // Close all file pointers and free up memory space.
+    pclose(shell_op);
+    fclose(fptr);
+
+    // Time Complexity = O(n); n = No. of saved wifi networks.
+    // Space Complexity = O(1);
+
+    return 0;
+}

Diff for: C/Wifi-Passwords/wifi_password.txt

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+<SSID>:<password>