on ocaml and set-user-id programs

[Stefano Zacchiroli <zack@bononia.it>]

I've wrote an ocaml program that needs to be executed set-user-id root.

I managed to have it being executed with effective user id 0 only
compiling in native code or in custom bytecode. Both executing it as a
script using "ocamlrun ocaml" and compiling it to non-custom bytecode
make the program having effective user id of the user executing it.
(Example session at the end of this mail)

This behaviour is annoying and makes impossible to run ocaml set-user-id
programs where the native code compiler isn't available. Am I missing
something or is this a shortcoming of the current ocaml interpreter?

Thanks in advance,
Cheers.

          Attempt using ocamlrun ocaml (FAILED)
  
  $ cat a.ml
  #!/usr/bin/ocamlrun /usr/bin/ocaml
  #use "topfind";;
  #require "unix";;
  Printf.printf "UID = %d\nEUID = %d\n" (Unix.getuid ()) (Unix.geteuid ())
  $ su
  Password:
  # chown root a.ml
  # chmod 4755 a.ml
  # ls -l a.ml
  -rwsr-xr-x  1 root zack 143 2005-03-27 11:50 a.ml*
  # exit
  $ ./a.ml
  UID = 3148
  EUID = 3148
  $
  
          Attempt using non-custom bytecode (FAILED)
  
  $ cat b.ml
  Printf.printf "UID = %d\nEUID = %d\n" (Unix.getuid ()) (Unix.geteuid ())
  $ ocamlfind ocamlc -package unix -linkpkg -o b b.ml
  $ head -1 b
  #!/usr/bin/ocamlrun
  $ su
  Password:
  # chown root b
  # chmod 4755 b
  # ls -l b
  -rwsr-xr-x  1 root zack 70145 2005-03-27 11:52 b*
  # exit
  $ ./b
  UID = 3148
  EUID = 3148
  
          Attempt using custom bytecode (OK)
  
  $ ocamlfind ocamlc -custom -package unix -linkpkg -o b b.ml
  $ su
  Password:
  # chown root b
  # chmod 4755 b
  # exit
  $ ./b
  UID = 3148
  EUID = 0
  
          Attempt using native code (OK)
  
  $ ocamlfind opt -package unix -linkpkg -o b b.ml
  $ su
  Password:
  # chown root b
  # chmod 4755 b
  # exit
  $ ./b
  UID = 3148
  EUID = 0

-- 
Stefano Zacchiroli -*- Computer Science PhD student @ Uny Bologna, Italy
zack@{cs.unibo.it,debian.org,bononia.it} -%- http://www.bononia.it/zack/
If there's any real truth it's that the entire multidimensional infinity
of the Universe is almost certainly being run by a bunch of maniacs. -!-