o Introduce kern.suser_permitted, a sysctl that disables the suser_xxx()

  returning anything but EPERM.
o suser is enabled by default; once disabled, cannot be reenabled
o To be used in alternative security models where uid0 does not connote
  additional privileges
o Should be noted that uid0 still has some additional powers as it
  owns many important files and executables, so suffers from the same
  fundamental security flaws as securelevels.  This is fixed with
  MAC integrity protection code (in progress)
o Not safe for consumption unless you are *really* sure you don't want
  things like shutdown to work, et al :-)

Obtained from:	TrustedBSD Project

1 files changed, 24 insertions, 0 deletions

diff --git a/sys/kern/kern_mib.c b/sys/kern/kern_mib.c
index 35c70fb..bc480c3 100644
--- a/sys/kern/kern_mib.c
+++ b/sys/kern/kern_mib.c
@@ -182,6 +182,30 @@ sysctl_kern_securelvl SYSCTL_HANDLER_ARGS
 SYSCTL_PROC(_kern, KERN_SECURELVL, securelevel, CTLTYPE_INT|CTLFLAG_RW,
     0, 0, sysctl_kern_securelvl, "I", "Current secure level");
 
+int suser_permitted = 1;
+ 
+static int
+sysctl_kern_suser_permitted SYSCTL_HANDLER_ARGS
+{
+	int error, flag;
+
+	flag = suser_permitted;
+
+	error = sysctl_handle_int(oidp, &flag, 0, req);
+	if (error || !req->newptr)
+		return (error);
+	if (flag != 0 && flag != 1)
+		return(EPERM);
+	if (!suser_permitted)
+		return(EPERM);
+	suser_permitted = flag;
+	return (0);
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, suser_permitted,
+    CTLTYPE_INT|CTLFLAG_RW, 0, 0, sysctl_kern_suser_permitted, "I",
+    "processes with uid 0 have privilege");
+
 char domainname[MAXHOSTNAMELEN];
 SYSCTL_STRING(_kern, KERN_NISDOMAINNAME, domainname, CTLFLAG_RW,
     &domainname, sizeof(domainname), "Name of the current YP/NIS domain");