LinuxQuestions.org - check Linux password from /etc/shadow

- Programming (https://www.linuxquestions.org/questions/programming-9/)

- - check Linux password from /etc/shadow (https://www.linuxquestions.org/questions/programming-9/check-linux-password-from-etc-shadow-680104/)

htabesh

10-30-2008 04:37 PM

check Linux password from /etc/shadow

Hi,
I want to write a C Program that get a password and user name, then compare it with encrypted password in /etc/shadow.
Please help me with SIMPLE CODES.

chrism01

10-30-2008 06:28 PM

Have a look here:
man crypt

bgeddy

10-30-2008 08:42 PM

There's some simple examples here

htabesh

10-31-2008 04:49 AM

I try below program:

Code:

#define _XOPEN_SOURCE

#include <stdio.h>

#include <time.h>

#include <unistd.h>

#include <crypt.h>



int main (void)

{

        char *passwd;

        passwd = crypt("123456", "$1$yfKCUYj6");



}

And then compile that:

Code:

gcc 1.c -o 1

The out put of compile is:

Code:

/tmp/cci2MSHh.o: In function `main':

1.c:(.text+0x21): undefined reference to `crypt'

collect2: ld returned 1 exit status

What is the problem? :(

keefaz

10-31-2008 08:20 AM

try add -lcrypt in the gcc command line

htabesh

10-31-2008 08:55 AM

OK, thanks.
Now how can I write a C Program that get a password and user name, then compare it with encrypted password in /etc/shadow for authentication?

nishamathew1980

11-02-2008 04:58 AM

@ bgeddy,
That was an interesting and informative article. Thanks for posting it here.

Linux Archive

htabesh

11-04-2008 08:12 AM

Finally I found the way. :)

Code:

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <crypt.h>

int main(int argc, char *agrv[])

{

        const char *const pass = "$1$Og9RbNrT$/gNprNaDgv.hNS01Ue2gi1";

            char *result;

        int ok;

        result = crypt(getpass("Password:"), pass);

        ok = strcmp (result, pass);

        if ( ok == 0 )

        {

                puts("Access granted"\n);

                return 0;

        }

        else 

        {

                puts ("Access denied\n");

                return 1;

        }

}

you can find and replace salt ("pass" in this program) in /etc/shadow for any user.
e.g.:
root:$1$Og9RbNrT$/gNprNaDgv.hNS01Ue2gi1:14159:0:99999:7:::

Keith Hedger

05-24-2013 12:44 PM

Thanks for this I've been trying a number of different example and this is the first that worked.
P.S. one minor typo "puts("Access granted"\n);" should be puts("Access granted\n");

All times are GMT -5. The time now is 04:30 AM.