[haskeline] #123: poor interaction with programs that fork or exec

[haskeline]

#123: poor interaction with programs that fork or exec
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Reporter:  MtnViewMark  |       Owner:     
    Type:  defect       |      Status:  new
Priority:  major        |   Milestone:     
 Version:               |    Keywords:     
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 Haskeline under either `defaultBehavior` or `preferTerm` opens `/dev/tty`.
 If the program then either forks or execs, this file is left open in the
 new process (for fork), or for the replacing executable (for exec).

 Management of open files is a common issue for programs that fork and/or
 exec. For those files that the program doesn't want to survive past the
 fork/exec, the usual method is to a) close such files in the child right
 after forking, and b) set the `FD_CLOEXEC` flag on the file descriptors so
 they are closed on exec (see '''System.Posix.IO''')

 Haskeline doesn't give programs enough leverage to do either of these for
 the `/dev/tty` file that it opens (and perhaps the history file as well,
 if that is left open). In forks that aren't expected to interact with the
 user, `/dev/tty` is left open. This may leave a connection to a particular
 terminal open well after the terminal is released by by the original
 process. In execs the situation can lead to a security breach: The program
 may have arranged for stdin/stdout/stderr to refer to a new terminal or
 other files before execing. Haskeline's surviving open of `/dev/tty` gives
 the exec'd program access to the original terminal.

 I can see two approaches to fixing this:
  * Offer a way to create a terminal based `Behavior` but on a supplied
 terminal `Handle` or `Fd`.
  * Expose a way  access the terminal `Handle`s Haskeline is using.

 In either case, it is almost certainly wrong for such files to survive an
 exec, and so Haskeline should ensure that all opened files have had
 {{{
     setCloseOnExec :: Fd -> IO ()
     setCloseOnExec fd = setFdOption fd CloseOnExec True
 }}}
 called on their underlying file descriptors.

-- 
Ticket URL: <http://trac.haskell.org/haskeline/ticket/123>
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