STANDARD(3)                  UNIX System V(local)                   STANDARD(3)


NAME
      standard, safe - standardize conditions in preparation for exec

SYNOPSIS
      standard()

      safe()

DESCRIPTION
      Standard alters a process's environment to make it relatively safe to do
      execvp, system, popen, etc.  It closes all descriptors except the
      standard ones and supplies a standard set of environment variables that
      ensure a standard interpretation of shell commands and a standard search
      path for programs.

      Safe is similar, but is intended for use in shell escapes and suchlike.
      It leaves the environment variables untouched but turns off setuid and
      setgid permissions.

      Use of either one permits a setuid/setgid program to run other programs
      without inadvertently bestowing special powers on nonstandard programs.
      Care must still be exercised as to what the standard descriptors refer
      to, and it is still possible for programs executed after use of standard
      (as opposed to safe) to give away special powers through their
      carelessness.

SEE ALSO
      environ(3), closeall(3)

HISTORY
      Local products.

BUGS
      Standard must necessarily supply standard values for some environment
      variables, but it is not clear whether it should pass other variables
      through or eliminate them.  The current implementation eliminates them,
      which is safer but sometimes inconvenient.

      One can construct elaborate scenarios in which a setuid program employing
      safe could be duped into executing a user-supplied program in a current
      directory the user ordinarily could not have reached.

      Possibly one or both should standardize the umask setting.











10/89                                                                    Page 1