Re: Building on Mac OS X (was Re: a quick mailutils question)

[Sergey Poznyakoff]

> Well, it strikes me the whole function can be replaced with:
[...]

No, it cannot. The function is run from the daemon, the file
descriptor 0 is associated with the input socket, thus isatty(0) will
always return 0, and the proposed replacement function will always
return NOT_HERE. The purpose of find_user is to find the tty which
has less idle time, i.e. the tty where the user is currently
working. So it has to scan the utmp database.

>   This is
> also much shorter. ;-)

But completely non-functional :^)

> Also, note that you have a potential buffer overflow in this function
> as it exists.  It may not be terribly useful, but if someone were able
> to, say, create a symlink to /dev/tty0 called something like
> 
> this_is_my_really_long_file_name_for_slash_dev_slash_tty0_in_my_home_directory
> 
> and then manage to open that as the controlling tty, your function
> would (maybe) overflow the char *tty.  I don't know if this is
> possible

Hardly. On input to this function tty is guaranteed to have
MAX_TTY_SIZE, which is the size of the automatic  ftty. While
operating on ftty its length is controlled, so at the point
of doing strcpy(tty, ftty), ftty will contain at most MAX_TTY_SIZE-1
bytes. The only dubious point is

   sprintf (ftty, "%s/", PATH_TTY_PFX);


(if the length of PATH_TTY_PFX happens to be > MAX_TTY_SIZE-2. But
that's impossible).


Regards,
Sergey