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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 14:40:04 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 14:40:04 +0000 |
commit | 25505898530a333011f4fd5cbc841ad6b26c089c (patch) | |
tree | 333a33fdd60930bcccc3f177ed9467d535e9bac6 /README.privsep | |
parent | Initial commit. (diff) | |
download | openssh-upstream.tar.xz openssh-upstream.zip |
Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'README.privsep')
-rw-r--r-- | README.privsep | 51 |
1 files changed, 51 insertions, 0 deletions
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. |