Bug 74950 - Errors/typos in security guide
Errors/typos in security guide
Product: Red Hat Public Beta
Classification: Retired
Component: rhl-sg (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: John Ha
Tammy Fox
Depends On:
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Reported: 2002-10-02 21:44 EDT by Miloslav Trmac
Modified: 2014-08-04 18:14 EDT (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2003-03-17 17:35:35 EST
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RHEL 7.3 requirements from Atomic Host:
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Description Miloslav Trmac 2002-10-02 21:44:59 EDT
Manual ID: rhl-sg(EN)-8.0-HTML-RHI (2002-08-30T11:29-0400)

3. Security Updates/Using the Errata Website:
Reccomending /tmp/updates for security updates isn't that great, because /tmp
is regularly pruned by tmpwatch (and might delete the rpms, possibly before
they are installed). For a permament storage it's a no-go.

5. Server Security/Securing NIS:
Section title "Assign Static Ports and Use" (rest missing)

5. Server Security/Securing Apache HTTP Server/Restrict Permissions for
Executable Directories
chown <directory_name> should be chown root <directory_name>

5. Server Security/Securing FTP/Anonymous Upload:
733 is rwx-wx-wx (correct), the example below is rwxr--r-- (which is 744 and
doesn't allow uploads at all)

5. Server Security/Securing Sendmail/Limiting Denial of Service Attack
confMIN_FREE_BLOCKS: blacks instead of blocks

5. Server Security/Securing Sendmail/Mail-only Users
shell /sbin/nologin is more explicit and obvious than /bin/false, and gives a
reasonable error message on login attempts

7. Firewalls/Netfilter iptables
Most examples are bogus, INPUT/OUTPUT is not local net/outside world, but
to/from this particular computer, packets local net<->outside world go only
through FORWARD (iptables is not ipchains)
--sport is SOURCE-port, so the examples allow connections FROM port xxx, not TO
port xxx
Setting ip_forward belongs in /etc/sysctl.conf
Maybe it should be emphasized that order of rules is important, just reading
the chapter and adding rules in that order would be bad (DROP after ACCEPT)

10. Intrusion Detection/Host-based IDS/RPM as an IDS
rpm -Fv /bin/ls check whole package containing /bin/ls, not only /bin/ls

Overall, the guide is a bit unbalanced. Chapter 5 is simply great, the rest of
Section II is good too (except for the iptables examples), but the rest seems
to be targeted at a different audience (managers?).
Comment 1 Johnray Fuller 2002-10-14 17:57:04 EDT
Thanks for pointing all of this out!

I will review these issues and issue the appropriate Errata ASAP.

Comment 2 Johnray Fuller 2002-11-04 16:46:36 EST
I have corrected:

5> Server Security/Securing NIS

5> Server Security/Securing Apache HTTP Server/Restrict Permissions for
Executable Directories

5> Server Security/Securing FTP/Anonymous Upload

5> Server Security/Securing Sendmail/Mail-only Users
shell /sbin/nologin 

-> I ignored my own advise from the earlier chapter when I said /bin false... 


I did not correct:

5> Server Security/Securing Sendmail/Limiting Denial of Service Attack
confMIN_FREE_BLOCKS: blacks instead of blocks

I can find no evidence to support the use of the term "blacks" here. From all
that I have been able to dig up, this directive relates to blocks left on the
spool drive, not black lists. Please let me know if I am missing something.

The Issues in chapters 7 and 10 will be addressed by John.

I will look into the issue for Chapter 3 and tell you the results here.

Thank you for all your help!

Comment 3 John Ha 2002-11-04 17:17:32 EST
I have reviewed the firewall chapter with our technical lead, and we agree that
the examples in this chapter are valid for machines which act as a
firewall/gateway between the Internet and a local network. INPUT and OUTPUT
chains in IPTables are for restricting or allowing connections inside and
outside the LAN. FORWARD jumps are used, for example, when administrators want
to send all incoming port 80 requests to one machine within the LAN that could
be running httpd on port 8080.

Your observation about running rpm -Vf on individual files is valid and should
have been written more clearly. Thank you for your suggestion.
Comment 4 Johnray Fuller 2002-11-04 17:50:18 EST
For the observations you make regarding recommending /tmp/updates in Chapter 3
Security Updates, I do not see the problem with creating a directory in /tmp/
because you should not need the security updates once you have installed them.

The fact that tmpwatch gets rid of the updates to save disk space if you forget
to delete them is, in my view, an advantage.

If there is something I am missing, let me know here.

I do appreciate you taking the time to send in this detailed bug. It whas helped

Comment 5 Johnray Fuller 2002-11-04 20:53:28 EST
I have posted errata and corrected the source in regards to these errors.

Feel free to post to this bug about any of the issues raised here.

Thanks again for your help.

Comment 6 Miloslav Trmac 2002-11-05 03:07:50 EST
at least in one case I have been misunderstood:

5. Server Security/Securing Sendmail/Limiting Denial of Service Attack
confMIN_FREE_BLOCKS: &#8212; The minimum number of free blacks which must be ...

As for the firewall chapter, the trouble is that
packets from *both* the LAN and the "outside" go through INPUT, but *only*
if directed at the computer in question.
Packets to *both* the LAN and the "outside" to through OUTPUT.
(It is quite logical, the kernel can't guess which is LAN and which is
"outside), but *only* if originated at the computer in question.
Packets which are forwarded between interfaces go *only* through FORWARD.
Yet the chapter contains things like:

The OUTPUT chain specifies any packets that originate from inside a LAN and
travels outside (for example, to a remote website)

The LAN (which uses a private class C IP range) rejects telnet
access from the outside
iptables -A INPUT -p tcp --sport telnet -j REJECT
(this means: Reject all packets to this computer (regardless of origin),
 which are *from* port telnet. In effect, this disables connections *from*
 the computer in question to any telnet service (because the "answers"
 will be rejected.)

The whole chapter seems to be based on these wrong assumptions.
Comment 7 Johnray Fuller 2002-11-06 12:16:55 EST
Although it may appear like I was trying to make a political statement through
the sendmail security section, it was actually a typo :-/

I have fixed it now, however.

Thanks for clarifying that for me.

Comment 8 Miloslav Trmac 2003-02-07 15:45:12 EST
Chapter 7 is basically unchanged in 8.0.93 doc set.
See the Reference guide explanation of INPUT/OUTPUT/FORWARD in filter
table, of just (man iptables).
Comment 9 Johnray Fuller 2003-02-07 17:38:07 EST
Hello Miloslav,

You are correct. That chapter as well as the Server chapter have not yet changed
for the new release.

They are due to be finished soon, but I do not think they will make it into a
beta release.

Comment 10 John Ha 2003-03-17 17:35:35 EST
The firewall chapter has been revamped with some clarification/explanation of
chain rules and implementation. Some rulesets have been changed based on this
bug report and further analysis. The revamped chapter will appear in the
upcoming version of the Security Guide. Thank you for your detailed report and
further comments on this chapter.

It appears that this covers all points for this bug report. Thank you again for
your detailed analysis and response. 

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