Hide password input on terminal

user_853321 0
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I want to mask my password while writing it with *. I use Linux GCC for this code. I know one solution is to use getch() function like this

#include <conio.h>   
int main()
{
    char c,password[10];
    int i;
    while( (c=getch())!= '\n');{
        password[i] = c;
        printf("*");
        i++;
    }
    return 1;
}

but the problem is that GCC does not include conio.h file so, getch() is useless for me. Does anyone have a solution?

masking gcc terminal linux c
16 Answers

Just pass for it the char* that you want to set password in and its size and the function will do its job

void set_Password(char *get_in, int sz){
    for (int i = 0; i < sz;) {
        char ch = getch();
        if (ch == 13) {
            get_in[i] = '\0';
            break;
        }
        else if(ch != 8){
            get_in[i++] = ch;
            putch('*');
        }
        else if(i > 0)
            cout << "\b \b",get_in[i--] = '\0';
    }
    cout << "\n";
}

This is an example, run it on your compiler

user_169987720

man getpass

This function is obsolete. Do not use it. If you want to read input without terminal echoing enabled, see the description of the ECHO flag in termios(3)

# include <termios.h>
# include <unistd.h>   /* needed for STDIN_FILENO which is an int file descriptor */

struct termios tp, save;

tcgetattr( STDIN_FILENO, &tp);              /* get existing terminal properties */
save = tp;                                  /* save existing terminal properties */

tp.c_lflag &= ~ECHO;                        /* only cause terminal echo off */

tcsetattr( STDIN_FILENO, TCSAFLUSH, &tp );  /* set terminal settings */

/*
   now input by user in terminal will not be displayed
   and cursor will not move
*/

tcsetattr( STDIN_FILENO, TCSANOW, &save);   /* restore original terminal settings */

If you notice, most current linux distro's do not mask a password with asterisks. Doing so divulges the length of the password which is no way beneficial. It is easier and better to simply make the cursor not move when a password is typed in. If for whatever reason you require a * to be printed for every character that's typed then you would have to grab every keypress before Enter is hit and that's always been problematic.

user_56937850 
printf("\nENTER PASSWORD: ");
while (1)
{
    ch=getch();
    if(ch==13)    //ON ENTER PRESS
        break;

    else if(ch==8)    //ON BACKSPACE PRESS REMOVES CHARACTER
    {
        if(i>0)
        {
            i--;
            password[i]='\0';
            printf("\b \b");
        }
    }
    else if (ch==32 || ch==9)    //ON PRESSING TAB OR SPACE KEY
        continue;
    else
    {
        password[i]=ch;
        i++;
        printf("*");
    }         
}
password[i]='\0';
user_128385100

Here is my idea, adapted from that of the C++ official site.

#include <termios.h>
#include <unistd.h>
#include <stdio.h>
#include <iostream>
#include <string>
using namespace std;
string getpass(const char *prompt, bool showchar = false, char echochar = '*')
{
    struct termios oi, ni;
    tcgetattr(STDIN_FILENO, &oi);
    ni = oi;
    ni.c_lflag &= ~(ICANON | ECHO);
    const char DELETE = 127;
    const char RETURN = 10;
    string password;
    unsigned char ch = 0;
    cout << prompt;
    tcsetattr(STDIN_FILENO, TCSANOW, &ni);
    while (getchar() != RETURN) {
        if (ch == DELETE) {
            if(password.length != 0){
                if (showchar) cout << "\b \b";
                password.resize(password.length() - 1);
            }
        }else {
            password += getchar();
            if (showchar) cout << echochar;
        }
    }
    tcsetattr(STDIN_FILENO,TCSANOW,&oi)
    cout << endl;
    return password;
}

It will read one character at once and add it to the string and supports showing another character.

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