bin/80687: [patch] Missing NULL termination after strncpy() in login(1)

[Bruce Evans]

The following reply was made to PR bin/80687; it has been noted by GNATS.

From: Bruce Evans <bde at zeta.org.au>
To: Przemyslaw Frasunek <venglin at freebsd.lublin.pl>
Cc: FreeBSD-gnats-submit at FreeBSD.org, freebsd-bugs at FreeBSD.org
Subject: Re: bin/80687: [patch] Missing NULL termination after strncpy() in
 login(1)
Date: Sat, 7 May 2005 04:18:34 +1000 (EST)

 On Fri, 6 May 2005, Przemyslaw Frasunek wrote:
 
 >> Description:
 > 	Similar to bin/80661
 >> How-To-Repeat:
 > 	N/A
 >> Fix:
 > --- usr.bin/login/login.c.old   Fri May  6 11:20:19 2005
 > +++ usr.bin/login/login.c       Fri May  6 11:20:36 2005
 > @@ -512,10 +512,10 @@
 >        /* Nothing else left to fail -- really log in. */
 >        memset((void *)&utmp, 0, sizeof(utmp));
 >        (void)time(&utmp.ut_time);
 > -       (void)strncpy(utmp.ut_name, username, sizeof(utmp.ut_name));
 > +       (void)strlcpy(utmp.ut_name, username, sizeof(utmp.ut_name));
 >        if (hostname)
 > -               (void)strncpy(utmp.ut_host, hostname, sizeof(utmp.ut_host));
 > -       (void)strncpy(utmp.ut_line, tty, sizeof(utmp.ut_line));
 > +               (void)strlcpy(utmp.ut_host, hostname, sizeof(utmp.ut_host));
 > +       (void)strlcpy(utmp.ut_line, tty, sizeof(utmp.ut_line));
 >        login(&utmp);
 >
 >        dolastlog(quietlog);
 
 The utmp names are apparently not strings, so teminating them just breaks
 recording of some names that work now.  Everything (?) uses strn*() to
 access these names, so non-strings in them work.  I logged in as a user
 with a 16-char username and least the following programs displayed it
 correctly:
 
      w
      who
      last
      ps
 
 The bug seems to be just that the non-stringness of the names is not
 documented.
 
 Bruce