From 9e7e4ab6617fef1d1681fc2d3e02554264ccc954 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 13:13:18 +0200 Subject: Adding upstream version 1:8.4p1. Signed-off-by: Daniel Baumann --- README.privsep | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 README.privsep (limited to 'README.privsep') diff --git a/README.privsep b/README.privsep new file mode 100644 index 0000000..d658c46 --- /dev/null +++ b/README.privsep @@ -0,0 +1,51 @@ +Privilege separation, or privsep, is method in OpenSSH by 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 now mandatory. During the pre-authentication +phase sshd will chroot(2) to "/var/empty" and change its privileges to the +"sshd" user and its primary group. sshd is a pseudo-account that should +not be used by other daemons, and must be locked and should contain a +"nologin" or invalid shell. + +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 -c 'sshd privsep' -d /var/empty -s /bin/false 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 separation chroot + --with-privsep-user=user Specify non-privileged user for privilege separation + +PAM-enabled OpenSSH is known to function with privsep on AIX, FreeBSD, +HP-UX (including Trusted Mode), Linux, NetBSD and Solaris. + +On Cygwin, Tru64 Unix and OpenServer only the pre-authentication part +of privsep is supported. Post-authentication privsep is disabled +automatically (so you won't see the additional process mentioned below). + +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. -- cgit v1.2.3