On 26/11/10 23:47, Philip Prindeville wrote:
> I recently rebuilt a failing mail server (sendmail and cyrus-imapd),
> replacing the hardware and building the replacement machine offline (leaving
> the current server in place while I did so).
>
> This would seem normal enough to do, but had some unintended pitfalls that
> really should be more addressable.
>
> Because the new machine was built offline while the old machine was still
> in-place, all of the packages that generate certificates--and there are a
> fair number of them:
>
> sendmail
> cyrus-imapd
> openssl
> openssh
> httpd/mod_ssl
>
> did so incorrectly. That is, they ended up using localhost.localdomain as
> the identity of the machine... and once I had the machine in place, I brought
> it up to find that various clients were now complaining about invalid certs.
>
> So I had to dig through what had happened, why, and what needed to be done
> (or redone) to fix this.
>
> Here are some observations and their accompanying conclusions.
>
> * A lot of packages generate their certs silently as part of the %post
> scripting
>
> This is certainly true of mod_ssl and cyrus-imapd.
>
> * A lot of packages also provide default answers to the certificate fields:
>
> Running:
>
> # rpm -q --scripts mod_ssl
>
> will get you:
>
> ...
> at<< EOF | /usr/bin/openssl req -new -key
> /etc/pki/tls/private/localhost.key \
> -x509 -days 365 -set_serial $RANDOM \
> -out /etc/pki/tls/certs/localhost.crt 2>/dev/null
> --
> SomeState
> SomeCity
> SomeOrganization
> SomeOrganizationalUnit
> ${FQDN}
> r...@${fqdn}
> EOF
> ...
>
>
> or
>
> # rpm -q --scripts cyrus-imapd
> ...
> /bin/cat<< EOF | make cyrus-imapd.pem
> --
> SomeState
> SomeCity
> SomeOrganization
> SomeOrganizationalUnit
> localhost.localdomain
> [email protected]
> EOF
> ...
>
> etc. It seems to be fairly common.
>
> Openssl provides the script /etc/pki/tls/certs/make-dummy-cert, which
> contains the function answers():
>
>
> answers() {
> echo --
> echo SomeState
> echo SomeCity
> echo SomeOrganization
> echo SomeOrganizationalUnit
> echo localhost.localdomain
> echo [email protected]
> }
>
> which is used to pipe form data to "openssl req" when generating a new
> certificate request.
>
>
> This seems to be duplicated in several places, and indeed some of the
> information could easily be captured statically at install time, and other
> data gleaned from the running system (such as the last two fields).
>
> * The certificate fields should be consistent
>
> The easiest way to do this is to have a standard file containing the first 5
> fields above (C, ST, L, O, OU). This file could be populated by
> Anaconda/Kickstart during installation.
>
> It's presence would then be a requirement for other packages that dynamically
> create certs at install time.
>
> * A permanent or 'real' identity should be an RPM requirement
>
> Packages should have the ability to have the system configured as its
> ultimate identity before being installed.
>
> This could be accomplished by an RPM pseudo-requirement that some package
> generates (via Provides:) as part of its installation.
>
> This could be the same package that provides the certificate "seed"
> information, but would also check to make sure that hostname, the domain,
> etc. were proper values.
>
> * If a machine gets relocated, it should be able to re-seed its certificates
>
> This last one is perhaps the most obscure change.
>
> If I build a machine "offline", test it with a temporary identity, and decide
> its "ready for prime-time", I should be able to reboot it with its new
> identity, and manually re-run the RPM scripts (or some idempotent portion of
> them) that regenerates all of the identity-derived information... typically
> this would be based on hostname, domain, IP address, and the certificate seed
> information (C, ST, L, O, and OU).
>
> We'd need a %post subsection that could be run idempotently to generate new
> certificates, for instance.
>
> In the examples of the above packages (openssl, mod_ssl, cyrus-imapd, etc)
> new .crt, .key, or .pem files would be generated... the serial number
> incremented (where necessary), and the service restarted.
>
> * This affects a lot more than just the packages that generate certs and keys
>
> This also would affect rpm (and possibly yum as well), in addition to the
> Anaconda/Kickstart.
>
> It might even be necessary to have a new package that runs early at boot time
> that checks packages (services) for "refreshed" certificates, and disables
> (chkconfig service off) any services that have out-of-date certificates/keys.
>
>
> So how far into left field am I on this, anyway?
>
> Thanks,
>
> -Philip
>
>
I don't agree. If you are replacing a production machine, you take the
keys from the old machine and use them. If you don't want to do that,
you buy new, probably stronger, certificates that are also valid. I
think your case only covers self-signed certificates.
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