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.
+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
+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, during the pre-authentication phase sshd will
Privsep requires operating system support for file descriptor passing.
Compression will be disabled on systems without a working 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.
+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, OpenServer, and Unicos 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.