Change 14236 by jhi@alpha on 2002/01/13 17:08:18
Anton Berezin did more reading and the uid setting story
gets more complex.
Affected files ...
.... //depot/perl/pod/perltodo.pod#47 edit
.... //depot/perl/utils/perldoc.PL#63 edit
Differences ...
==== //depot/perl/pod/perltodo.pod#47 (text) ====
Index: perl/pod/perltodo.pod
--- perl/pod/perltodo.pod.~1~ Sun Jan 13 10:15:05 2002
+++ perl/pod/perltodo.pod Sun Jan 13 10:15:05 2002
@@ -186,6 +186,22 @@
All the code we ship with Perl needs to be sensible about temporary file
handling, locking, input validation, and so on.
+=head2 Sort out the uid-setting mess
+
+Currently there are several problems with the setting of uids ($<, $>
+for the real and effective uids). Firstly, what exactly setuid() call
+gets invoked in which platform is simply a big mess that needs to be
+untangled. Secondly, the effects are apparently not standard across
+platforms, (if you first set $< and then $>, or vice versa, being
+uid==euid== zero, or just euid==zero, or as a normal user, what are
+the results?). The test suite not (usually) being run as root means
+that these things do not get much testing. Thirdly, there's quite
+often a third uid called saved uid, and Perl has no knowledge of that
+feature in any way. (If one has the saved uid of zero, one can get
+back any real and effective uids.) As an example, to change also the
+saved uid, one needs to set the real and effective uids B<twice>-- in
+most systems, that is: in HP-UX that doesn't seem to work.
+
=head2 Custom opcodes
Have a way to introduce user-defined opcodes without the subroutine call
==== //depot/perl/utils/perldoc.PL#63 (text) ====
Index: perl/utils/perldoc.PL
--- perl/utils/perldoc.PL.~1~ Sun Jan 13 10:15:05 2002
+++ perl/utils/perldoc.PL Sun Jan 13 10:15:05 2002
@@ -169,13 +169,27 @@
my $id = eval { getpwnam("nobody") };
$id = eval { getpwnam("nouser") } unless defined $id;
$id = -2 unless defined $id;
+ #
+ # According to Stevens' APUE and various
+ # (BSD, Solaris, HP-UX) man pages setting
+ # the real uid first and effective uid second
+ # is the way to go if one wants to drop privileges,
+ # because if one changes into an effective uid of
+ # non-zero, one cannot change the real uid any more.
+ #
+ # Actually, it gets even messier. There is
+ # a third uid, called the saved uid, and as
+ # long as that is zero, one can get back to
+ # uid of zero. Setting the real-effective *twice*
+ # helps in *most* systems (FreeBSD and Solaris)
+ # but apparently in HP-UX even this doesn't help:
+ # the saved uid stays zero (apparently the only way
+ # in HP-UX to change saved uid is to call setuid()
+ # when the effective uid is zero).
+ #
eval {
- # According to Stevens' APUE and various
- # (BSD, Solaris, HP-UX) man pages setting
- # the real uid first and effective uid second
- # is the way to go if one wants to drop privileges,
- # because if one changes into an effective uid of
- # non-zero, one cannot change the real uid any more.
+ $< = $id; # real uid
+ $> = $id; # effective uid
$< = $id; # real uid
$> = $id; # effective uid
};
End of Patch.
