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diff --git a/crypto/openssh/README.privsep b/crypto/openssh/README.privsep new file mode 100644 index 0000000..6c798f3 --- /dev/null +++ b/crypto/openssh/README.privsep @@ -0,0 +1,60 @@ +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 enabled by default; see the +UsePrivilegeSeparation option in sshd_config(5). + +On systems which lack mmap or anonymous (MAP_ANON) memory mapping, +compression must be disabled in order for privilege separation to +function. + +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 + +If you are on UnixWare 7 or OpenUNIX 8 do this additional step. + # ln /usr/lib/.ns.so /usr/lib/ns.so.1 + +/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 + +Privsep requires operating system support for file descriptor passing +and mmap(MAP_ANON). + +PAM-enabled OpenSSH is known to function with privsep on Linux. +It does not function on HP-UX with a trusted system +configuration. 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 1.7 2002/06/21 14:48:02 djm Exp $ |
