checkPassword.cpp

#include <iostream>

using namespace std;

string exec(const char* cmd); 	// Used for executing terminal commands in c++
string getPassword(); 	        // Prompts the user for their system password and checks to see if it is the correct password
						                    // If the password is correct, it returns it in a string


int main(int argc, char *argv[]) {  // Example implementation of getPassword()
	string password  = getPassword();
	cout << endl << "User password = " << password;
}

string exec(const char* cmd) {
	char buffer[128];
	string result = "";
	shared_ptr<FILE> pipe(popen(cmd, "r"), pclose);
	if (!pipe) throw runtime_error("popen() failed!");
	while (!feof(pipe.get())) {
		if (fgets(buffer, 128, pipe.get()) != NULL)
			result += buffer;
	}
	return result;
}

string getPassword() {
	string status = "default";
	string password = "";
	while (status == "default" || (int) status[0] == 0) {
		password = exec("read -s -p \"Password: \" password && echo $password");
		password.erase(remove(password.begin(), password.end(), '\n'), password.end());
		string command = "if [[ $(echo " + password + " | sudo -k -S echo valid) = \"valid\" ]] &>/dev/null; then echo \"Correct password\"; fi";
		status = exec(command.c_str());
		status.erase(remove(status.begin(), status.end(), '\n'), status.end());
		
		if (status != "Correct password") {
			cout << "\nSorry, try again." << endl << flush;
		}
	}
	return password;
}