[Spread-users] setuid/chroot doesn't work in Mac OS X

[Mike Laster]

The default implementation doesn't seem to properly setuid/chroot under 
OS X.

I found that this fix works:

*** spread.c    2002/08/07 15:56:43     1.1
--- spread.c    2002/09/26 21:57:36
***************
*** 167,173 ****
                     || (pwd = getpwnam(SP_USER)) == NULL
                     || chdir(SP_RUNTIME_DIR) < 0
                     || chroot(SP_RUNTIME_DIR) < 0
!                   || setgroups(0, 0) < 0
                     || setgid(grp->gr_gid) < 0
                     || setuid(pwd->pw_uid) < 0)
           {
--- 167,173 ----
                     || (pwd = getpwnam(SP_USER)) == NULL
                     || chdir(SP_RUNTIME_DIR) < 0
                     || chroot(SP_RUNTIME_DIR) < 0
!                   || setgroups(1, &grp->gr_gid) < 0
                     || setgid(grp->gr_gid) < 0
                     || setuid(pwd->pw_uid) < 0)
           {

Apparently the BSD flavor of setgroups doesn't like (0,0) parameters, 
it dies with an errno 22 (invalid argument)
but if I switch it to setgroups(1, &grp->gr_gid), it is happy.

This should be just as secure.  I have mine configured to run as 
nobody/nobody, so this setgroups() should set
the group membership to the 'nobody' group.  Are there any potential 
security holes in this patch that I'm not
seeing?