- (stevesk) add initial README.privsep

ChangeLog

@@ -1,4 +1,5 @@
 20020513
+ - (stevesk) add initial README.privsep
  - (stevesk) [configure.ac] nicer message: --with-privsep-user=user
  - (djm) Add --with-superuser-path=xxx configure option to specify what $PATH
    the superuser receives.
@@ -576,4 +577,4 @@
  - (stevesk) entropy.c: typo in debug message
  - (djm) ssh-keygen -i needs seeded RNG; report from markus@
 
-$Id: ChangeLog,v 1.2111 2002/05/13 03:51:40 stevesk Exp $
+$Id: ChangeLog,v 1.2112 2002/05/13 03:57:04 stevesk Exp $

README.privsep

@@ -0,0 +1,53 @@
+Privilege separation, or privsep, is an experimental feature in
+OpenSSH in which operations that require root privilege are performed
+by a separate privileged monitor process.  Its purpose is to prevent
+privilege escalation by containing corruption to an unprivileged
+process.  More information is available at:
+	http://www.citi.umich.edu/u/provos/ssh/privsep.html
+
+Privilege separation is not enabled by default, and may be enabled by
+specifying "UsePrivilegeSeparation yes" in sshd_config; see the
+UsePrivilegeSeparation option in sshd(8).
+
+When privsep is enabled, the pre-authentication sshd process will
+chroot(2) to "/var/empty" and change its privileges to the "sshd" user
+and its primary group.  You should do something like the following to
+prepare the privsep preauth environment:
+
+	# mkdir /var/empty
+	# chown root:sys /var/empty
+	# chmod 755 /var/empty
+	# groupadd sshd
+	# useradd -g sshd sshd
+
+/var/empty should not contain any files.
+
+configure supports the following options to change the default
+privsep user and chroot directory:
+
+  --with-privsep-path=xxx Path for privilege seperation chroot
+  --with-privsep-user=user Specify non-privileged user for privilege separation
+
+Privsep requires operating system support for file descriptor passing
+and mmap(MAP_ANON).
+
+PAM currently only works with privsep on Linux.  It does not function
+on Solaris or HP-UX.  PAMAuthenticationViaKbdInt does not function with
+privsep.
+
+Note that for a normal interactive login with a shell, enabling privsep
+will require 1 additional process per login session.
+
+Given the following process listing (from HP-UX):
+
+     UID   PID  PPID  C    STIME TTY       TIME COMMAND
+    root  1005     1  0 10:45:17 ?         0:08 /opt/openssh/sbin/sshd -u0
+    root  6917  1005  0 15:19:16 ?         0:00 sshd: stevesk [priv]
+ stevesk  6919  6917  0 15:19:17 ?         0:03 sshd: stevesk@2
+ stevesk  6921  6919  0 15:19:17 pts/2     0:00 -bash
+
+process 1005 is the sshd process listening for new connections.
+process 6917 is the privileged monitor process, 6919 is the user owned
+sshd process and 6921 is the shell process.
+
+$Id: README.privsep,v 1.1 2002/05/13 03:57:04 stevesk Exp $