BSD tty security, part 3: How to Fix It

[Paul Falstad]

wes at harem.clydeunix.com (Wes Peters) wrote:
>I think write should reject any input not from a terminal:

>    if (!isatty(fileno(stdin))) {
>        fprintf(stderr, "write: input must be a terminal!\n");

>I know this will take care of 'cat longfile | write sucker', but does it
>also take care of a 'here is' document (i.e. shell << document)?

Yes, but it doesn't take care of this:

   cat longfile | pty write sucker

--
              Paul Falstad  pfalstad at phoenix.princeton.edu
         And on the roads, too, vicious gangs of KEEP LEFT signs!
     If Princeton knew my opinions, they'd have expelled me long ago.