There has been a notice of a breach (see: CVE-2007-4752) as to
some binary content upstream of CentOS. I do not address that
matter here beyond stating that the CentOS team have responded
to the matter, and will continue this review process:
updated 22 Aug 2008 CentOS acknowledge CVE-2007-4752 and are
reviewing our build and signing processes and hosts for signs
of tampering subsequent to retrieval of SRPMs
It can be hard for a person to get a capsule writeup on signed
content, and how to verify that it is indeed authentic. I
have placed clearsigned content addressing this process at my
personal domain webserver:
http://www.herrold.com/import-key-howto.txt.asc
and as an attachment to this email. I have verified that the
copy at my site verifies. this email. Hopefully this attched
writeup will transit the CentOS mailing list manager intact.
I also include it inline below, but this may mangle the
signature.
-- Russ herrold
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
A few minutes on using detached and clearsigned content.
In light of today's CVE-2007-4752 by the CentOS project's upstream:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4752
I issue this brief piece on using GnuPG
1. View a proposed key to use, at the MIT keyserver
from: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x650D5882
2. Copy and create a local instance
[herrold at centos-5 redhat]$ vi rht-key
[herrold at centos-5 redhat]$ gpg --import rht-key
gpg: key 650D5882: duplicated user ID detected - merged
gpg: key 650D5882: public key "Red Hat, Inc. (Security Response Team)
<secalert at redhat.com>" imported
gpg: Total number processed: 1
gpg: imported: 1
gpg: 3 marginal(s) needed, 1 complete(s) needed, classic trust model
gpg: depth: 0 valid: 2 signed: 5 trust: 0-, 0q, 0n, 0m, 0f, 2u
gpg: depth: 1 valid: 5 signed: 2 trust: 0-, 0q, 0n, 1m, 4f, 0u
gpg: next trustdb check due at 2009-03-14
3. Compute a local fingerprint of the candidate
[herrold at centos-5 redhat]$ gpg --fingerprint 650D5882
pub 1024D/650D5882 2001-11-21
Key fingerprint = 9273 2337 E5AD 3417 5265 64AB 5E54 8083 650D 5882
uid Red Hat, Inc. (Security Response Team)
<secalert at redhat.com>
sub 2048g/7EAB9AFD 2001-11-21
[herrold at centos-5 redhat]$
4. Compare and validate the fingerprint of the candidate against the RHT
statement of the same fingerprint:
http://www.redhat.com/security/team/key/
5. You do NOT need to accept a key permanently to check signed content
purportedly with it; consider the Red Hat notice at:
http://www.redhat.com/security/data/openssh-blacklist.html
6. We can retrieve the checking script
wget https://www.redhat.com/security/data/openssh-blacklist-1.0.sh
and the (presumptively) signed checksum of that file
wget https://www.redhat.com/security/data/openssh-blacklist-1.0.sh.asc
This is called a detached signature
7. And then we can validate ('--verify') that the signature and the file
were
signed by a person in possession of the private key.
Hopefully that private key is itself protected, as behind one way firewalls,
and with a 'pass phrase' which matches a known public (which we
retrieved
and added earlier). This procedural security process is followed by me [one
way firewalls, and pass phrases, and other CentOS team members], along with
other measures.
[herrold at centos-5 redhat]$ gpg --verify openssh-blacklist-1.0.sh.asc \
openssh-blacklist-1.0.sh
gpg: Signature made Fri 22 Aug 2008 05:02:29 AM EDT using DSA key ID
650D5882
gpg: Good signature from "Red Hat, Inc. (Security Response Team)
<secalert at redhat.com>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the
owner.
Primary key fingerprint: 9273 2337 E5AD 3417 5265 64AB 5E54 8083 650D 5882
[herrold at centos-5 redhat]$
8. As we have not indicated to gpg that we permanently trust this key, gpg
adds the WARNING -- this is expected and correct under this outline. The
validation checks out.
9. This file can be clearsigned -- the process we will follow is this:
[herrold at centos-5 .gnupg]$ gpg --clearsign import-key-howto.txt
You need a passphrase to unlock the secret key for
user: "R P Herrold <herrold at owlriver.com>"
1024-bit DSA key, ID 9B649644, created 2003-02-09
File `import-key-howto.txt.asc' exists. Overwrite? (y/N) y
[herrold at centos-5 .gnupg]$
10. That is, import-key-howto.txt is clearsigned, and a new file,
import-key-howto.txt.asc, is produced. As I did it twice, to add this text,
the warning about Overwriting a file appeared.
11. This is a non-detached (clearsigned, file, and might also be tested by
retrieving the indicated key contents, and doing a '--verify'
12. As I have previously certified my own key, I can do it more simply
locally:
[herrold at centos-5 .gnupg]$ gpg --verify import-key-howto.txt.asc
gpg: Signature made Fri 22 Aug 2008 12:37:39 PM EDT using DSA key ID
9B649644
gpg: Good signature from "R P Herrold <herrold at owlriver.com>"
[herrold at centos-5 .gnupg]$
Note that the TIME of the signing will vary, as I have to resign the file
after adding this content.
13. Previously (prior to 22 Aug 2008), I have included my PGP details in
every piece of email I send. Starting today, as to email originate; I will
add another line with my GPG details as well. I will send this document to
the main centos mailing list.
Date: Thu, 21 Aug 2008 17:43:28 -0400 (EDT)
From: R P Herrold <herrold at owlriver.com>
To: trading-shim general mailing list <ts-general at trading-shim.org>
Subject: segmentation faults
In-Reply-To: <1219351509.12150.18.camel at gb07>
Message-ID: <alpine.LRH.1.999.0808211742100.2443 at arj.bjyevire.pbz>
References: <200808202117.m7KLH4rf011059 at pippin.first.lan>
<20080820224216.GA11712 at localhost>
<alpine.LRH.1.10.0808202147340.28881 at arj.bjyevire.pbz>
<1219351509.12150.18.camel at gb07>
User-Agent: Alpine 1.999 (LRH 1145 2008-08-19)
X-M: Go Blue
X-OpenPGP-Key-ID: 0x7BFB98B9
MIME-Version: 1.0
In pine (alpine), one does this with Customized X-headers:
Customized Headers = X-M: Go Blue
X-GnuPG-GPG-Key-ID: ox9B649644
X-OpenPGP-Key-ID: 0x7BFB98B9
This piece intentionally does not address CentOS response; a preliminary
statement on this has been posted in the /topic of the IRC channel #centos
on irc.freenode.org, and I have done a blog losting which is up at:
http://planet.centos.org/
- -- Russ herrold
herrold at owlriver.com
herrold at centos.org
security at centos.org
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