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|
#This file was created by <camille> Tue Jan 4 10:45:05 2000
#LyX 0.12 (C) 1995-1998 Matthias Ettrich and the LyX Team
\lyxformat 2.15
\textclass article
\language american
\inputencoding latin1
\fontscheme default
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\papersize Default
\paperpackage a4
\use_geometry 0
\use_amsmath 0
\paperorientation portrait
\secnumdepth 3
\tocdepth 3
\paragraph_separation skip
\defskip medskip
\quotes_language english
\quotes_times 2
\papercolumns 1
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\paperpagestyle default
\layout Title
\size huge
msec
\size default
\noun on
[Mandrake SECurity tools]
\layout Author
Camille Bégnis <camille@mandrakesoft.com>
\layout Date
22/12/1999
\layout Standard
\begin_inset LatexCommand \tableofcontents
\end_inset
\layout Section
Introducing msec
\layout Standard
While Linux is being used for a very wide range of applications, from basic
office work to high availability servers, came the need for different security
levels.
It is obvious that constraints inherent to highly secured servers do not
match the needs of a secretary.
In the other hand a big public server is more sensitive to malicious people
than my isolated Linux box.
\layout Standard
It is in that aim that were designed the msec package.
It is made of two parts:
\layout Enumerate
Scripts that modify the whole system to lead it to one of the six security
levels provided with msec.
These levels range from very poor security and ease of use, to paranoid
config, suitable for very sensitive applications, managed by experts.
\layout Enumerate
Cron jobs, that will periodically check the integrity of the system upon
security level configuration, and eventually detect and warn you of possible
intrusion of the system or security leak.
\layout Standard
Note that the user may also define his own security level, adjusting parameters
to his own needs.
\layout Section
Installation
\layout Standard
msec is a base rpm.
That means that if you previously installed Linux-Mandrake, msec is already
installed on your system.
\layout Standard
Installing the rpm will create a msec directory into /etc/security, containing
all is needed to secure your system.
\layout Standard
Then just login as root and type
\begin_inset Quotes erd
\end_inset
/etc/security/msec/init.sh x
\begin_inset Quotes erd
\end_inset
, x being the security level you want or
\begin_inset Quotes eld
\end_inset
custom
\begin_inset Quotes erd
\end_inset
to create your own security level.
The script will begin to remove all modifications made by a previous security
level change, and apply the features of the chosen security level to your
system.
If you choose
\begin_inset Quotes eld
\end_inset
custom
\begin_inset Quotes erd
\end_inset
, then you will be asked a series of questions for each security feature
msec proposes.
At the end, these features will be applied to your system.
\layout Standard
Note that whatever the level you chose, your configuration will be stored
into
\begin_inset Quotes eld
\end_inset
/etc/security/msec/security.conf
\begin_inset Quotes erd
\end_inset
.
\layout Subsection
Level 0
\layout Standard
This level is to be used with care.
It makes your system more easy to use, but very sensitive at the same time.
In particular, you shouldn't use this security level if you answer yes
to at least one of the following questions:
\layout Itemize
Is my computer connected to the Internet?
\layout Itemize
Is my computer connected to other computers by a network?
\layout Itemize
Does this computer will be used by someone else than me?
\layout Itemize
Is there some confidential stuff on my computer I don't want others have
access?
\layout Itemize
I don't know Linux enough and I could harm it by myself?
\layout Standard
As we see, this security level shouldn't be set by default because it may
result in big problems for your data.
\layout Subsection
Level 1
\layout Standard
The main security improvement compared with level 0 is that now, the access
to one user's stuff is granted via user-name and password.
So it may be used by various people, and it is less sensitive to bad maneuvers.
However it shouldn't be used for a connected computer whether by modem
or to a LAN (Local Area Network).
\layout Subsection
Level 2
\layout Standard
Few improvements for this security level, the main one is that there are
more security warnings and checks.
It is more secure for multi-users use.
\layout Subsection
Level 3
\layout Standard
This is the standard security recommended for a computer that will be used
to connect to the Internet as a client.
Most of security checks are periodically run, specifically one that check
for open ports on the system.
However, these open ports are kept opened and access to them is granted
to everyone.
So this security level is not really suited for a system permanently connected
to the Internet.
\layout Standard
From the user's point of view, the system is now a little bit more closed,
so it'll need some basic knowledges of the Linux system to achieve some
special operations.
The security here offered is comparable with the one of a standard RedHat
or previous Mandrake distribution.
\layout Subsection
Level 4
\layout Standard
With this security level, the use of this system as a server becomes possible.
The security is now high enough to use the system as a server which accept
connections from many clients.
Connections from the computer itself only will be granted.
Howether advanced services have been disabled, and the system administrator
will have to activate the desired ones by hand in config files.
He also will have to define from whom the access is granted.
\layout Standard
Security checks will warn system administrator of possible security holes
or intrusions on the system.
\layout Subsection
Level 5
\layout Standard
We take level 4 features, but now the system is entirely closed.
Security features are at their maximum.
The system administrator has to activate ports, and grant connections to
give other computers access to services offered by this machine.
\layout Section
Security levels features
\layout Standard
Follows the description of the different security features each level brings
to the system.
These features are of various types:
\layout Itemize
file permissions,
\layout Itemize
warnings dispatching,
\layout Itemize
periodicall security checks:
\layout Quotation
- on files: suid root, writeable, unowned;
\layout Quotation
- listening ports: active, promiscuous;
\layout Quotation
- passwords files.
\layout Itemize
X display connections,
\layout Itemize
listening port check,
\layout Itemize
services available,
\layout Itemize
boot password,
\layout Itemize
authorized clients.
\layout Standard
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0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 2 0 1 0 0 0 "" ""
0 2 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
0 8 0 1 0 0 0 "" ""
\series bold
\emph on
Feature
\backslash
Security level
\newline
0
\newline
1
\newline
2
\newline
3
\newline
4
\newline
5
\series default
\emph toggle
\newline
Global security check
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
*
\newline
umask users
\newline
002
\newline
002
\newline
022
\newline
022
\newline
077
\newline
077
\newline
umask root
\newline
002
\newline
002
\newline
022
\newline
022
\newline
022
\newline
077
\newline
shell without password
\newline
*
\newline
\newline
\newline
\newline
\newline
\newline
authorized to connect to X display
\newline
all
\newline
local
\newline
local
\newline
none
\newline
none
\newline
none
\newline
User in audio group
\newline
*
\newline
*
\newline
*
\newline
\newline
\newline
\newline
.
in $PATH
\newline
*
\newline
*
\newline
\newline
\newline
\newline
\newline
Warning in /var/log/security.log
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Warning directly on tty
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Warning in syslog
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Warning sent by mail to root
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Suid root file check
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Suid root file md5sum check
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Writeable file check
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
*
\newline
Permissions check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Suid group file check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Unowned file check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Promiscuous check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Listening port check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Passwd file integrity check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Shadow file integrity check
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
System security check every midnight
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
All system events additionally logged to /dev/tty12
\newline
\newline
\newline
\newline
*
\newline
*
\newline
*
\newline
Only root can shutdown
\newline
\newline
\newline
\newline
\newline
*
\newline
*
\newline
Services not known disabled
\newline
\newline
\newline
\newline
\newline
*
\newline
*
\newline
Boot password
\newline
\newline
\newline
\newline
\newline
*
\newline
*
\newline
Grant connection to
\newline
all
\newline
all
\newline
all
\newline
all
\newline
local
\newline
none
\layout Standard
Note that six out of the ten periodical checks can detect changes on the
system.
They store into files located in
\begin_inset Quotes eld
\end_inset
/var/log/security/
\begin_inset Quotes erd
\end_inset
the configuration of the system during the last check (one day ago), and
warn you of any changes occurred meanwhile.
These checks are:
\layout Itemize
Suid root file check
\layout Itemize
Suid root file md5sum check
\layout Itemize
Writeable file check
\layout Itemize
Suid group file check
\layout Itemize
Unowned file check
\layout Itemize
Listening port check
\layout Subsection
Global security check
\layout Itemize
NFS filesystems globally exported.
This is regarded as insecure, as there is no restriction for who may mount
these filesystems
\layout Itemize
NFS mounts with missing nosuid.
These filesystems are exported without the
\begin_inset Quotes eld
\end_inset
nosuid
\begin_inset Quotes erd
\end_inset
option.
\layout Itemize
Host trusting files contains
\begin_inset Quotes eld
\end_inset
+
\begin_inset Quotes erd
\end_inset
sign.
That means that one of the files
\begin_inset Quotes eld
\end_inset
/etc/hosts.equiv /etc/shosts.equiv /etc/hosts.lpd
\begin_inset Quotes erd
\end_inset
is containing hosts which are allowed to connect without proper authentication.
\layout Itemize
Executables found in the aliases file.
It issues a warning naming the executables run through files "/etc/aliases
\begin_inset Quotes erd
\end_inset
and
\begin_inset Quotes eld
\end_inset
/etc/postfix/aliases".
\layout Subsection
umask users
\layout Standard
Simply sets the umask for normal users to the value corresponding to the
security level.
\layout Subsection
umask root
\layout Standard
The same but for the root.
\layout Subsection
shell without password
\layout Standard
Access to the consoles is granted without asking for a password.
\layout Subsection
authorized to connect to X display
\layout Itemize
all : Everybody from everywhere can open an X window on your screen.
\layout Itemize
local : Only people connected at localhost may open an X window on your
screen.
\layout Itemize
none : Nobody can do that.
\layout Subsection
User in audio group
\layout Standard
Each user is a member of the
\begin_inset Quotes eld
\end_inset
audio
\begin_inset Quotes erd
\end_inset
group.
That means that every user connected to the system is given access to sound
card.
\layout Subsection
.
in $PATH
\layout Standard
the
\begin_inset Quotes eld
\end_inset
.
\begin_inset Quotes erd
\end_inset
entry is added to $PATH environment variable, allowing execution of programs
within the current working directory.
\layout Subsection
Warning in /var/log/security.log
\layout Standard
Each warning issued by msec is logged into
\begin_inset Quotes eld
\end_inset
/var/log/security.log
\begin_inset Quotes erd
\end_inset
.
\layout Subsection
Warning directly on tty
\layout Standard
Each warning issued by msec is directly printed on current console.
\layout Subsection
Warning in syslog
\layout Standard
Warnings of msec are directed to syslog service.
\layout Subsection
Warning sent by mail to root
\layout Standard
Warnings issued by msec are also sent by mail to root.
\layout Subsection
Suid root file check
\layout Standard
Check for new or removed suid root files on the system.
If such files are encountered a list of these files is issued as a warning.
\layout Subsection
Suid root file md5sum check
\layout Standard
Checks the md5sum signature of each suid root file that is on the system.
If the signature has changed, it means that a modification has been made
to this program, probably a backdoor.
A warning is then issued.
\layout Subsection
Writeable file check
\layout Standard
Check wether files are world writable on the system.
If so, issues a warning containing the list of these naughty files.
\layout Subsection
Permissions check
\layout Standard
This one checks permissions for some special files such as .netrc or user's
config files.
It also checks permissions of users home dir.
If their permissions are too loose or owners unusual, it issues a warning.
\layout Subsection
Suid group file check
\layout Standard
Check for new or removed suid group files on the system.
If such files are encountered, a list of these files is issued as a warning.
\layout Subsection
Unowned file check
\layout Standard
This check searches for files owned by users/groups(or more accurately by
uids/gids) not known into /etc/password, If such files are found, the owner
is automatically changed to user/group
\begin_inset Quotes eld
\end_inset
nobody
\begin_inset Quotes erd
\end_inset
.
\layout Subsection
Promiscuous check
\layout Standard
This test checks every ethernet card to determine wether they are in promiscuous
mode.
This mode allows the card to intercept every packet received by the card,
even those that are not directed to it.
It may mean that a sniffer is running on your machine.
\layout Standard
Note that this check is setted up to be run every minute.
\layout Subsection
Listening port check
\layout Standard
Issues a warning with all listening ports.
\layout Subsection
Passwd file integrity check
\layout Standard
Verify that each user has a password ( no blank password) and if it is shadowed.
\layout Subsection
Shadow file integrity check
\layout Standard
Verify that each user into the shadow file has a password ( no blank password).
\layout Subsection
System security check every midnight
\layout Standard
All previous checks will be performed everyday at midnight.
This relies on the addition of cron scripts in crontab file.
\layout Subsection
All system events additionally logged to /dev/tty12
\layout Standard
*All* system messages directed to syslog are copied to tty12 console.
\layout Subsection
Only root can shutdown
\layout Standard
You must be root (or referenced into /etc/shutdown.allow) and logged into
a console to be able to shutdown or reboot the machine.
\layout Subsection
Services not known disabled
\layout Standard
All services not contained into
\begin_inset Quotes eld
\end_inset
/etc/security/msec/init-sh/server.4
\begin_inset Quotes erd
\end_inset
for level 4 or
\begin_inset Quotes eld
\end_inset
server.5
\begin_inset Quotes erd
\end_inset
for level 5 will be disabled.
They are not removed, but simply not started when loading a runlevel.
If you need some of them, just add them again with the
\begin_inset Quotes eld
\end_inset
chkconfig
\begin_inset Quotes erd
\end_inset
utility (you might also need to restart them with init scripts in /etc/rc.d/init.
d/ ).
\layout Subsection
Boot password
\layout Standard
Allows you to setup a password for Lilo.
Prevents (unexperienced) people from rebooting the machine, but in the
other hand, the machine won't be able to reboot by itself.
\layout Subsection
Grant connection to
\layout Itemize
all : All computers are allowed to connect to open ports.
\layout Itemize
local : Only the localhost is allowed to connect to open ports.
\layout Itemize
none : No computers are allowed to connect to open ports.
\layout Section
ToDo
\layout Standard
- Automatic tty locking ( unlock by passwd ) after X time of inactivity.
\layout Standard
- In high security level, only user having access to group "sugrp" can use
the su command.
\layout Section
Author
\layout Standard
Vandoorselaere Yoann <yoann@mandrakesoft.com>
\the_end
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