xref: /openbsd-src/share/man/man8/security.8 (revision b9f606a97458e9c423b5d67f252053cab05afc9b)

.\" $OpenBSD: security.8,v 1.27 2024/12/24 17:08:50 krw Exp $
.\"
.\" David Leonard, 2001. Public Domain.
.\"
.Dd $Mdocdate: December 24 2024 $
.Dt SECURITY 8
.Os
.Sh NAME
.Nm security
.Nd periodic system security check
.Sh DESCRIPTION
.Nm
is a command script that examines the system for some signs of security
weaknesses.
It is only a security aid and does not offer complete protection.
.Nm
is run by
.Xr daily 8 ,
which mails any output to root on a daily basis.
.Pp
The
.Nm
script carries out the following list of simple checks:
.Bl -bullet
.It
Check the
.Xr master.passwd 5
and
.Xr group 5
files for
syntax, empty passwords, partially closed accounts,
suspicious UIDs, suspicious GIDs, and duplicate entries.
.It
Check root's home directory and login environment for
insecure permissions, suspicious paths, and umask commands in the
dotfiles.
.It
Check for suspicious commands in
.Pa /etc/mail/aliases .
.It
Check for insecurities in
.Pa /etc/hosts.lpd .
.It
Check user
.Pa .rhosts
and
.Pa .shosts
files for open access.
.It
Check user home directory permissions.
.It
Check many user dotfile permissions.
.It
Check user mailbox permissions.
.It
Check NFS
.Xr exports 5
file for global export entries.
.It
Check for changes in setuid/setgid files and devices.
.It
Check disk ownership and permissions.
.It
Check for changes in the device file list.
.It
Check for permission changes in special files and system binaries listed in
.Pa /etc/mtree/special .
.Nm
also provides hooks for administrators to create their own lists.
These lists should be kept in
.Pa /etc/mtree/
and filenames must have the suffix
.Dq .secure .
The following example shows how to create such a list,
to protect the programs in
.Pa /bin :
.Bd -literal -offset 4n
# mtree -cx -p /bin -K sha256digest,type > /etc/mtree/bin.secure
# chown root:wheel /etc/mtree/bin.secure
# chmod 600 /etc/mtree/bin.secure
.Ed
.Pp
.Sy Note:
These checks do not provide complete protection against
Trojan horse binaries, as
the miscreant can modify the tree specification to match the replaced binary.
For details on really protecting yourself against modified binaries, see
.Xr mtree 8 .
.It
Check for changes in files listed in
.Pa /etc/changelist .
Files being created or deleted,
as well as content change in the files themselves,
are reported.
See
.Xr changelist 5
for further details.
.It
Check for changes to the disklabels and partition tables of mounted disks.
.It
Report on the installation or removal of any system
.Xr package 5 .
.It
Check
.Xr hostname.if 5
file permissions.
.El
.Pp
The intent of the
.Nm
script is to point out some obvious holes to the system administrator.
.Sh ENVIRONMENT
The following variables can be set in
.Pa /etc/daily.local :
.Pp
.Bl -tag -width "SUIDSKIP" -compact
.It Ev SUIDSKIP
A whitespace-separated list of absolute paths to be skipped
in setuid/setgid file checks and in device special file checks.
Avoid trailing slashes.
.El
.Sh FILES
.Bl -tag -width /dev/changelist -compact
.It Pa /etc/changelist
.It Pa /etc/daily
.It Pa /etc/mtree
.It Pa /usr/libexec/security
.It Pa /var/backups
.El
.Sh SEE ALSO
.Xr changelist 5 ,
.Xr daily 8 ,
.Xr mtree 8
.Sh HISTORY
A
.Nm
shell script appeared in
.Bx 4.3 Reno ,
but most functionality only came with
.Bx 4.4 .
.Sh AUTHORS
.An -nosplit
The present manual was written by
.An David Leonard
for
.Ox 2.9 .
.An Andrew Fresh Aq Mt afresh1@openbsd.org
and
.An Ingo Schwarze Aq Mt schwarze@openbsd.org
rewrote
.Nm
from scratch in
.Xr perl 1
for
.Ox 5.0 .
.Sh BUGS
The name of this script may provide a false sense of
.Nm security .
.\" Well, I thought it was amusing.
.Pp
There are perhaps an infinite number of ways the system can be compromised
without this script noticing.