Tool for authentication of Usenet control messages.
Original source: https://ftp.isc.org/pub/pgpcontrol/ and https://git.eyrie.org/?p=usenet/pgpcontrol.git
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<TITLE>Authentication of Usenet Group Changes</TITLE>
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<H1>Authentication of Usenet Group Changes</H1>
This document addresses a method for the authentication of the special
types of Usenet articles that are used to maintain the namespace of
Usenet groups. A basic familiarity with what the Usenet control
message types "newgroup", "rmgroup" and "checkgroups" do is assumed;
this is not a tutorial in namespace administration.
<P>
Usenet articles are notoriously easy to forge, and control messages
are no exception. Since administrators often want to have their news
systems automatically honor requests from some particular people to
add or remove newsgroups, it is risky to trust the From: and Sender:
headers to identify the real sender of a message, as has historically
been done. Thus a system using Philip Zimmerman's
<A HREF="#Getting PGP">Pretty Good Privacy</A>®
(PGP® ) was developed to provide a more secure means
of authenticating the sender of a control message.
<P>
Unlike traditional PGP authentication of messages, which just
verifies that the contents of the body of a message are unchanged from
when it was digitally "signed", this system also needed to sign a few
headers of the control message to verify the action to be taken and
to guard against certain other pitfalls. Another goal was to make the
signature as unobtrusive as possible and require minimal changes to
existing software in order to work.
<P>
<H2>How to Verify Control Messages</H2>
Listed below are the steps you need to take to enable PGP
authentication of control messages on your system.
<P>
Here is the short and simple version for someone who feels confident
hacking around the news system and doesn't like to read a lot:
<P>
<OL>
<LI>Get and configure the software:
<UL>
<LI>
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/pgpverify">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/pgpverify</A>
<LI>
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/server-patches/">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/server-patches/</A>
</UL>
<LI>Add
<A HREF="#Keys">maintainers' PGP public keys</A>
to the news system key ring.
<LI>Enable verification through the news system authorization system.
<DL>
<DT>INN:
<DD>Use the action <B>verify-<I>pgp_userid</I></B> (possibly appended
<B>=<I>logfile</I></B>) in <I>control.ctl</I>.
<DT>Other systems:
<DD>Sorry, not implemented yet.
</DL>
<LI>Test <I>pgpverify</I>.
If you have the news.announce.newgroups key in your key ring, run
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/sample.control">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/sample.control</A>
through <I>pgpverify</I> on stdin. It should spit out the
string "news.announce.newgroups" on stdout.
</OL>
Here is a more verbose version of the instructions:
<P>
<OL>
<LI>
Get the software.
<P>
There are two pieces of code that will need to be added to a news
server to make use of this authentication system: a stand-alone
script that verifies an article is what it says it is, and a
patch to hook it into the news server's processing of control messages.
<P>
The stand-alone program,
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/pgpverify">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/pgpverify</A>,
is a
<A HREF="#Getting Perl">Perl</A>
script that should work with Perl version 4 and up. (I have not tested
it with earlier versions.) It does not contain any code making it
dependent on any particular news server software.
<P>
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/server-patches/">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/server-patches/</A>
has patches (currently "a patch" is more correct) for hooking the
system into existing news server software. Choose the one for your system
from the list below.
<P>
<UL>
<LI>
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/server-patches/inn1.4sec/pgpcontrol.pch">
INN version 1.4sec</A>
</UL>
<P>
I regret that I do not have the time to develop more patches, but I
will gladly add patches for other systems to this page as they are
made available to me. I am particularly interested in getting patches
for C News version CR.E and INN version unoff4.
<P>
<LI>
Install it in your news system.
<P>
First you must ensure that the absolute paths to <I>perl</I> and to
<I>pgp</I> are correct in the first few lines of the <I>pgpverify</I>
program. No other configuration of options or pathnames should be
needed.
<P>
Next, the following steps assume, solely for the sake of making it
easy for me to write a simple recipe, that you have copied
<I>pgpverify</I> and the patch for your system to your news server as
<I>/tmp/pgpverify</I> and <I>/tmp/pgpcontrol.pch</I> respectively. I
have tried to format this so that you should be able to cut and paste
any of the lines in italics directly to your shell.
<P>
<UL>
<LI>If you are running INN:
<P>
<PRE>
cd to the executable program directory that has <I>ctlinnd</I>
<I>mv /tmp/pgpverify pgpverify</I>
cd to the root of your INN source tree
<I>cd site</I>
<I>patch < /tmp/pgpcontrol.pch</I>
<I>make install</I>
</PRE>
<P>
<LI>If you are running some other system:
<P>
You're out of luck until someone writes a patch and instructions for
your system and makes it available to me for redistribution.
<P>
</UL>
<P>
<LI>
Enable verification for the hierarchies that interest you.
<P>
To verify messages, you must have a
<A HREF="#Keys">PGP public key for each signer</A>
that you wish to trust. It should be entered in a key ring that is
accessible to the user-id that runs the news system by running <I>pgp
-ka</I> on a file containing the key to add. For example, at a
site that runs the news server software as <I>news</I>, the following
command run by the <I>news</I> user-id should add the key bounded by
BEGIN and END "PGP PUBLIC KEY BLOCK" lines in the file <I>/tmp/key</I>
to the default key ring that would be used for authentication:
<PRE>
<I>pgp -ka /tmp/key</I>
</PRE>
<P>
As a general policy rule, control message signers will not use their
control message keys to introduce other keys, so when PGP asks you a
question similar to, "Would you trust this user to act as an
introducer and certify other people's public keys to you?" answer that
you would not.
<P>
After you have added the appropriate key to your key ring, you need to
tell the news software to validate the control messages received.
As implemented, the system will perform the requested action if the
message can be authenticated and it will mail the message to the news
system administrator if it cannot. Clearly there are other possible
actions that could be implemented, but I wanted to keep the patches
minimal. Future releases of the server software will probably have
increased flexibility.
<P>
<UL>
<LI>If you are running INN:
<P>
Automatic processing of control messages is handled by
<I>control.ctl</I>, which you edit in the same <I>site</I>
subdirectory where you patched <I>parsecontrol</I>.
<I>control.ctl</I> has several lines at the beginning of it that
describe the format of the file, and there is an even longer
<I>control.ctl(5)</I> manual page. To enable PGP verification in
addition to the normal authorization done by <I>control.ctl</I>, use
the action <B>verify-<I>pgp_userid</I></B> in the fourth field.
<P>For example, if you trust tale@uunet.uu.net to manage
groups in the "Big 8" hierarchies, you could have lines line these:
<P>
<PRE>
newgroup:tale@uunet.uu.net:\
comp.*|humanities.*|misc.*|news.*|rec.*|sci.*|soc.*|talk.*:\
verify-news.announce.newgroups
rmgroup:tale@uunet.uu.net:\
comp.*|humanities.*|misc.*|news.*|rec.*|sci.*|soc.*|talk.*:\
verify-news.announce.newgroups
checkgroups:tale@uunet.uu.net:\
comp.*|humanities.*|misc.*|news.*|rec.*|sci.*|soc.*|talk.*:\
verify-news.announce.newgroups
</PRE>
<P>
Additionally, if you like the logging feature available with the
action <B>doit=<I>logfile</I></B>, you can get the same logging
by using <B>verify-<I>pgp_userid</I>=<I>logfile</I></B>.
<P>
<LI> If you are running some other system:
<P>
You're out of luck until someone writes a patch and instructions for
your system and makes it available to me for redistribution.
<P>
</UL>
<P>
<LI>
Test the system.
<P>
Get
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/sample.control">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/sample.control</A>
and save it to a file on your system; <I>/tmp/sample.control</I> will
be used for this example. You'll use it to make sure things will work
as expected.
<P>
To verify the control message, you will need the
<A HREF="#news.announce.newgroups">key for news.announce.newgroups</A>
and authorization in your news system for tale@uunet.uu.net to
automatically perform "newgroup". Go ahead and enable it for the test
even if you don't want to really allow this, because it is easy enough
to rescind after the test by editing the control message authorization
file and removing the key with <I>pgp -kr news.announce.newgroups</I>.
<P>
You can check that the <I>pgpverify</I> part of the system will work
properly simply by feeding it the sample control message on stdin:
<PRE>
pgpverify < /tmp/sample.control
</PRE>
<P>
If if could run pgp and find the correct key in the default key ring,
the string <B>news.announce.newgroups</B> should be printed. The exit
status of the script, found in most shells with the command <I>echo
$?</I> as the next command after <I>pgpverify</I>, should be 0 (zero).
<P>
If it doesn't work and you've tried and tried to figure out why,
<A HREF="mailto:tale@uunet.uu.net (David C Lawrence)">email me</A>
a complete description of the problem you are having and how you have
tried to remedy it. At a bare minimum, your mail should include a
copy of the message you are trying to verify, a typescript of the
attempted execution, and the output of <I>pgp -kc</I> and
<I>pgp -kvc news.announce.newgroups</I>.
<P>
When <I>pgpverify</I> passes its test, use the appropriate procedure
below for you news server to verify the authorization system.
<P>
<UL>
<LI>If you are running INN:
<P>
First, cd to the directory where <I>parsecontrol</I> is installed.
Then execute the following four lines, in order, as the user who owns
the news system:
<PRE>
/bin/sh
PROG=newgroup
set -- tale@uunet.uu.net "" /tmp/sample.control
(. ./parsecontrol "$@"; echo $ACTION)
</PRE>
<P>
If the message verified correctly, the <I>echo</I> command should
output <B>doit</B>; otherwise, verification failed and the output
should be <B>mail</B>.
<P>
Edit <I>/tmp/sample.control</I> and change all occurences of
<B>newusers</B> to <B>newgroups</B>. Then repeat the
<I>parsecontrol</I> and <I>echo</I> lines. This time verification
should fail.
<P>
<LI>If you are running some other system:
<P>
You're out of luck until someone writes a patch and instructions for
your system and makes it available to me for redistribution.
</UL>
<H2>Frequently Asked Questions</H2>
<OL>
<H3><LI>How come this presumably valid messages doesn't check out with
pgpverify?</H3>
<UL>
<LI>You don't have the correct key for the user that signed it in your
key ring.
<LI>You cut-and-pasted the message in your window system, which
converted the tab characters in the original message into spaces in
the message you are trying to decode. Having this handled completely
correctly by the signing/verifying code is harder than you might first
think.
<LI>You are running <I>pgpverify</I> on a saved
copy of the article that includes an extraneous trailing newline, such
as might be inserted by saving the message from a mail handler or news
reader, that was not present in the original message.
</UL>
</OL>
<HR><HR>
<H2><A NAME="Keys">List of PGP Public Keys for Newsgroup Administration</A></H2>
This is a list of keys known to be used for maintaining various parts
of the newsgroup namespace. They are listed alphabetically by the
hierarchies they are used for, along with the email address they are
sent by (for use in <I>control.ctl</I>) and the group that people
should follow if they are interested in tracking announcements about
the hierarchy. The "Check also" references point to locations that
should have identical public key blocks; it is best if you confirm the
block listed here by checking against the others.
<P>
The existence of key here only means that I, David Lawrence, trust the
person who uses it to be a responsible maintainer of that particular
hierarchy of groups. You are solely responsible for deciding whether
you will use the keys here at your own site.
<P>
<A NAME="news.announce.newgroups"><HR></A>
<H3>comp, humanities, misc, news, rec, sci, soc, talk</H3>
Control message sender:
<A HREF="mailto:newgroups-request@uunet.uu.net">tale@uunet.uu.net</A><BR>
Administrative group:
<A HREF="news:news.announce.newgroups">news.announce.newgroups</A><BR>
Check also:
<UL>
<LI><A HREF="ftp://ftp.uu.net/usenet/news.announce.newgroups/PGP.PUBLICKEY">
ftp://ftp.uu.net/usenet/news.announce.newgroups/PGP.PUBLICKEY</A>
<LI><A HREF="http://swissnet.ai.mit.edu:11371/pks/lookup?op=get&search=0xB88DA9C1">
pgp-public-keys-beta@pgp.ai.mit.edu</A> ("Subject: GET 0xB88DA9C1", empty body)
</UL>
<PRE>
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: 2.7
mQCNAjFsLmQAAAEEAKPbDQI6oDtYJYPvYxt7I4PMxThaq51Z/5kqfW7C3dMn6vPL
d+UsXHfRzMaQXkLBR4nIaQj5OHVtbKCjVTVIMtgfgsPeh9GRSONW870S5HUTQcB7
eDhQqvvst1ZEowhTf/CX01chaxOfWq3ZPB09VVohQTmvRJn2BMJdOtO4janBAAUR
tBduZXdzLmFubm91bmNlLm5ld2dyb3Vwc4kAlQIFEDF33BHCXTrTuI2pwQEBiJQD
/1uiv20adyB2a3tzBYESEEhKtugAVHGRJQJE4Ar5PrcnovF3aNpLFumslIaAzCwP
XlCANMjFHg140IB6SgJ8W8XH15u+1cMOmqTbk0wtmVgeLOLaSMgNWt65FV4AUn7e
RZdhK8j/JKxE0a+6gKu4S0PiUDrvnCEWUPjlXiqsbnjR
=E8K8
-----END PGP PUBLIC KEY BLOCK-----
</PRE>
<P>
<A NAME="fr.announce.newgroups"><HR></A>
<H3>fr</H3>
Control message sender:
<!-- <A HREF="mailto:newgroups-request@uunet.uu.net">tale@uunet.uu.net</A> -->
<BR>
Administrative group:
<A HREF="news:fr.announce.newgroups">fr.announce.newgroups</A><BR>
Check also:
<UL>
<LI><A HREF="http://swissnet.ai.mit.edu:11371/pks/lookup?op=get&search=0x382B64FD">
pgp-public-keys-beta@pgp.ai.mit.edu</A> ("Subject: GET 0x382B64FD", empty body)
</UL>
<PRE>
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: 2.6.2i
mQCNAzF41OMAAAEEAOnjgblNPQ+Xhnxw3K/EMz1vm2sfi2Ci/XG8HsWg2yc+hQla
fMGQbQciSDFsBK0Kmy7gNvC9c7qAsQfeqpvQqJ+3hJiUvbQIi6bj2ZOSqE58Vh80
7Y+Fx71R/AKGZ88dGbysUg1r5770aw6JP1wn6Ve29PRTdS7yasmXGhU4K2T9AAUT
tBVmci5hbm5vdW5jZS5uZXdncm91cHOJAJUDBRAxf8MhyZcaFTgrZP0BAZ0ZA/0S
nxzmcN/yI858v+80ZpWaMkO/OtdF49gCfv/yv8xrRQfdGkjLFIl+Gry/H9236MZD
rTSjb5R2PaicExO3b0tcRAAGOXyrRwc1squDdSvldko2ewQE9giZ4T1+fJRou1yO
hbwPmaOBOt2EropUpvRPfKNeu/vjdKv1GEREkhIZTQ==
=o/05
-----END PGP PUBLIC KEY BLOCK-----
</PRE>
<P>
<HR>
<H3>humanities</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR>
<H3>misc</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR>
<H3>news</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR>
<H3>rec</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR>
<H3>sci</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR>
<H3>soc</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR>
<H3>talk</H3>
See the <A HREF="#news.announce.newgroups">comp</A> hierarchy entry.
<HR><HR>
<H2><A NAME="Signing">Signing Control Messages</A></H2>
If you are responsible for sending control messages about authorized
changes to a newsgroup hierarchy, then
<A HREF="ftp://ftp.uu.net/networking/news/misc/pgpcontrol/signcontrol">
ftp://ftp.uu.net/networking/news/misc/pgpcontrol/signcontrol</A> will
sign your control messages so that <I>pgpverify</I> can authenticate
them. It is a Perl script that requires Perl version 5 or higher to
work. It has several configuration parameters that should be reviewed
before use.
<P>
When establishing a PGP key and control message sender, please use
tokens that are not tied to a particular individual. This makes it
easier to transfer the administrative responsibility when it finally
comes time. (The all-too-common "tale@uunet.uu.net" sender is still
used for control messages because of its legacy in the installed
server base; I would prefer to use newgroups-request@uunet.uu.net.)
Please also do not sign other keys with the key that is used for
control messages.
<P>
If you will be using this script to sign control messages, please
<A HREF="mailto:tale@uunet.uu.net (David C Lawrence)">let me know</A>
the hierarchy that you are responsible for maintaining and the
information that you would like to appear in the
<A HREF="#Keys">List of PGP Public Keys for Newsgroup Administration</A>.
<HR><HR>
<H2><A NAME="Getting PGP">How to Get PGP</A></H2>
Information about obtaining PGP can be found in the
<A HREF="http://www.cis.ohio-state.edu/hypertext/faq/usenet/pgp-faq/where-is-PGP/faq.html">
Where to get the latest PGP FAQ</A>
article, posted regularly in the
<A HREF="news:alt.security.pgp">alt.security.pgp</A>
newsgroup.
<H2><A NAME="Getting Perl">How to Get Perl</A></H2>
Information about obtaining Perl can be found in the
<A HREF="http://www.cis.ohio-state.edu/hypertext/faq/usenet/perl-faq/part1/faq.html">
comp.lang.perl.* FAQ 1/5 - Availability</A>
article, posted regularly in the
<A HREF="news:comp.lang.perl.misc">comp.lang.perl.misc</A>
newsgroup.
<HR>
Last modified: 25 April 1996
<ADDRESS>
David C Lawrence<BR>
<A HREF="mailto:tale@uunet.uu.net (David C Lawrence)">
tale@uunet.uu.net</A>
</ADDRESS>