Thread: Password field with: **********

hi

I want to create a login for a simple C aplication, and I'm wondering if it's possible to hide the password caracters by replacing them with ******* ?

humm...
OK!
tnx quzah, that's what i'm going to do :-)

hey Adak!
tnx for the reply...

i'm going to try that. i'll keep you posted

I have my reservations about that suggestion. The value of the key pressed should be echoed to stdout before the call to getchar returns in the first place.

Originally Posted by citizen

I have my reservations about that suggestion. The value of the key pressed should be echoed to stdout before the call to getchar returns in the first place.

My apologies - you're quite right, Citizen. I forgot I programmed that "replacement of char with a star" program, in another language.

The C version program I coded was using Borland/Turbo C, and used conio.h.

Thanks for the post, Citizen.

Adak

What you're thinking of is probably not safe and too difficult when working compiler/OS specific alternatives exist. I'd sooner secretly write black characters on black background before considering that.

Yeah, sorry to have lead you astray with that earlier post, Indio.

Code:

/* Password.c by Adak */

#include <stdio.h>
#include <conio.h>  	/* for getch() */ 

#define MaxChars 20

char c;
char Usrname[MaxChars] = { '\0' };
char Passwrd[MaxChars] = { '\0' };

int main()  {
   int i = 0;
   printf("\n\n Enter Username: ");
   fgets(Usrname, MaxChars, stdin);

   printf("\n Enter Password:");
   putchar(' ');
   while((c = getch()) != 13) {   /* '\n' doesn't work here */
      putchar('*');
      if (i < MaxChars - 1)
        Passwrd[i++] = c;
   }  
   Passwrd[i] = '\0';

   /* display it */
   printf("\n\n       Username: %s", Usrname);
   printf("\n       Password: %s", Passwrd);
   printf("\n\n\t\t     Program Complete, Please Press Enter "); 
   fseek(stdin, 0, SEEK_END);
   c = getchar();
   return(0);
}

The fseek() code is just to move the pointer in the keyboard buffer down to the end. Otherwise I have to do silly stuff like:

Code:

getchar();
getchar();

or
getchar();
while((c = getchar()) != '\n');

And if the password was shorter than the allocated memory, it worked one way, and when the password that was keyboarded in was longer than the number of char's in the password array, it worked another (not due to a buffer overrun, just more keys stored in the keyboard buffer).

So I got tired of that crap.

The fseek() above handles both instances, as I want them - just the same, and just one getchar() needed.

Above program runs OK in a console window of Windows2000. Haven't tried it on an XP box.

Adak

hey Adak, no problem.

your most recent code works in windows vista x64

but there's a little problem...if i want to use the backspace to erase the password, it puts more caracters to the field.

i don't know if this is a vista x64 issue or just a minor code issue. Can you try using the backspace to see if it's from my OS or the code?

You'll have to hardcode any kind of rubout (backspace, delete) that you want, because the input isn't line buffered and the terminal can't take care of it for you. In general this means that you have to find the key pressed, print it to stdout to move the cursor, print spaces, and move the cursor back.

Code:

if( c == '\b' ) {
   printf( "\b\b \b\b" );
   /* manage your buffers: you wouldn't want to keep old data there */
   pwd[ --pwdcount ] = '\0';
}

Something like that... depends on what you really have in terms of storage or code.
Google the ASCII character set, implement what you need.