Re: Shadow passwords...

[Guy Maor <maor@ece.utexas.edu>]

"Larry 'Daffy' Daffner" <vizzie@airmail.net> writes:

> How do I support shadow and non-shadow with the same binary again? :)
> 
> Since I'll be compiling xscreensaver with locking support (thus
> requiring passwords, and needing to be shadow-aware), I need this
> information now, and I can't seem to find the man page for
> getspnam/getspent.

They work just like their pwent analogues.  Something like this will
return a filled in passwd struct whether shadow is in use or not.

int main() {
    uid_t shadowuid = geteuid();
    seteuid(getuid());

    /* lots of code */

    struct passwd *pw;
    struct shadow *spw;
    pw = getpwnam(myname);
    seteuid(shadowuid);
    if (spw = getspna(pw->pw_name))
        pw->pw_passwd = spw->sp_pwdp;
    seteuid(getuid());

   /* lots more code */
}

The program will have to be 2755 root.shadow.  Set the euid as I've
shown above as security advisories are embarassing.  I've neglected to
check the system call return values in the interest of brevity.  You
would do a seteuid(getuid()) and exit if any of them failed naturally.


Guy