31 aug 2018 kl. 19:47 skrev Chuck Campbell campbell@accelinc.com:

I am getting myself confused, and need someone who fully understands this process to help me out a bot.

I would like to obtain an ssl certificate, so I can run my own imap server on a machine in my office.

My domain is hosted by networksolutions, but I don't run my imap server there.

I am assuming I'll need to pay a CA to generate what I need, but I'm confused about what I need. I am running dovecot at teh moment, but my clients (iphone, windows laptops) say my ssl connection is not trusted. The phone just won't connect.

I tried emailing the dovecot.pem file to my phone and installing it, but it just says it is not trusted.

This leads me to obtaining a real CA issued certificate. I'm not sure what to do with it, once I get one, and then if I need to subsequently regenerate my dovecot.pem file??

Nope, you don't have to pay for a certificate at one of the traditional CAs, you can use Let's Encrypt to have free but fully valid certificates for your server.

See https://letsencrypt.org/ for more information. I can recommend https://github.com/xenolf/lego for use on your server, but there are many different LE clients out there.

If your phone does not already trust Let's Encrypt's CAs, you should be able to install their certificates to get it working. I suggest you start by getting a cert onto your server and take it from there though.

Regards, Leo

31 aug 2018 kl. 21:31 skrev Michael Schumacher michael.schumacher@pamas.de:

Leo,

...

...

I would like to obtain an ssl certificate, so I can run my own imap server on a machine in my office. I am assuming I'll need to pay a CA to generate what I need, but I'm confused about what I need. I am running dovecot at teh moment, but my clients (iphone, windows laptops) say my ssl connection is not trusted. The phone just won't connect.

...

Nope, you don't have to pay for a certificate at one of the traditional CAs, you can use Let's Encrypt to have free but fully valid certificates for your server.

...

See https://letsencrypt.org/ for more information. I can recommend https://github.com/xenolf/lego for use on your server, but there are many different LE clients out there.

certbot works only with ports 80 or 443? Can lego work with with IMAP ports like 143 or 993? The documentation is not very clear.

I haven't used certbot, only lego, but that's not a problem.

If you use leo you will have it manage the request for new and renewal of existing certificates. It does this using challenges over HTTP or DNS. I am guessing this is where your understanding that it only works with port 80 and 443 comes from - it uses either of those ports to communicate with Let's Encrypt's systems when using the HTTP challenge.

However, this is separate from your IMAP server. Which ports your IMAP server use has nothing to do with lego or the LE certificate stuff. As long as something, e.g. lego, successfully manages to get valid certs onto your server, your IMAP server should be able to use those certificates (that is, a private key file and a public key file). Your IMAP server can use those files and may then respond to requests for IMAP over SSL/TLS on e.g. port 993. Port 143 is for unencrypted IMAP, so in that case certificates are not relevant at all.

Consider trying leo out with the staging parameter enabled (see the documentation for it right there on the GitHub page), that way you can experiment with it and see what it produces and how it works. Then you can configure your IMAP server to use those certificate files.

Regards, Leo

31 aug 2018 kl. 21:38 skrev Ulf Volmer u.volmer@u-v.de:

On 31.08.2018 21:31, Michael Schumacher wrote:

...

certbot works only with ports 80 or 443? Can lego work with with IMAP ports like 143 or 993? The documentation is not very clear.

basically - independent of the client - letsencrypt will only support http/https or dns based challenges.

so - if you want to get certificates for an imap only server, you will have to setup an webserver for the challenge. or deal with your dns server.

Setting up a web server is not needed - all you need is lego (which by the way is one statically linked binary since it's written in Go).

If you use the HTTP challenge, lego will temporarily, only for the time needed to fulfill the challenge, listen for HTTP on the relevant port.

In summary, lego contains a web server for the HTTP challenge.

Letsencrypt.org has one other thing you should know about, not a biggie, the certificate is only good for 90 days at a time. Then you need to renew. But they though about that too, you can automate the renewal, so that each time the certificate expires and new one is generated and installed. It is supported by all of the major browsers, by supported, they are a part of the group that funds letsencrypt.org

john

On 8/31/2018 3:38 PM, Ulf Volmer wrote:

On 31.08.2018 21:31, Michael Schumacher wrote:

...

certbot works only with ports 80 or 443? Can lego work with with IMAP ports like 143 or 993? The documentation is not very clear.

basically - independent of the client - letsencrypt will only support http/https or dns based challenges.

so - if you want to get certificates for an imap only server, you will have to setup an webserver for the challenge. or deal with your dns server.

best regards Ulf _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

On Fri, Aug 31, 2018 at 05:30:53PM -0400, Robert Moskowitz wrote:

Letsencrypt is a very important development, but it has (IMHO) a shaking foundation.  I would not build a production system around it.  But then I have lived in aspects of PKI since '95...

I presume you meant "shaky foundation"? If so, would you care to elaborate?

John

1 sep 2018 kl. 00:42 skrev Robert Moskowitz rgm@htt-consult.com:

On 08/31/2018 05:54 PM, John R. Dennison wrote:

...

On Fri, Aug 31, 2018 at 05:30:53PM -0400, Robert Moskowitz wrote:

...

Letsencrypt is a very important development, but it has (IMHO) a shaking foundation. I would not build a production system around it. But then I have lived in aspects of PKI since '95...

I presume you meant "shaky foundation"?

Yes. I am not in California (or similar earthquake place!) Good old stable Michigan (we do get mild ones once in a while. :)

...

If so, would you care to elaborate

It is designed for getting web servers quickly into TLS and then to a more stable provider. "Make the web safe for all". If your content is short information, your contacts will never notice that you go to a new cert quarterly. Long-term users might also never see this, but I can see web services where a new cert every 90 days will cause a pain point.

And for other services like IMAP, SMTP, LDAP (maybe not LDAP) constant changing certs even with a long lived root may get old for your customers.

Plan on this to 'get into the pool', but not to live with it for more than a year.

Unfortunately, there has never been an effective business model for small customers.

We are kind of close with DMARC, but I think it misses the mark. Putting your domain root cert into your DNSSEC signed domain should be all that is needed to establish a rooted trust.

I have to speak with some IETF colleagues on this (particularly in DNSSEC and DMARC)....

I'm not sure I still see the point you're trying to make. What actual practical and concrete problems are you suggesting may arise in the situations you touch on above?

As far as I know, if you have a properly set up LE certificate for a service, and renew it regularly, clients will not have a problem with this. They trust the root CA, and when you renew/replace the certificate, they will happily trust the new one, over and over again.

Considering all relevant root trust stores now contain LE's CA, it's here to stay from what I can tell, not to mention it's working well so far.

On 31.08.2018 21:31, Michael Schumacher wrote:

certbot works only with ports 80 or 443? Can lego work with with IMAP ports like 143 or 993? The documentation is not very clear.

in case of other then Webserver you use ACME-DNS just for a simple ACME client that is capable for ACME-DNS use acme.sh https//acme.sh/

Your IMAP server can use those files and may then respond to requests for IMAP over SSL/TLS on e.g. port 993. Port 143 is for unencrypted IMAP, so in that case certificates are not relevant at all.

Well, apart from STARTTLS ...

P.

Am 01.09.2018 um 02:06 schrieb Warren Young warren@etr-usa.com:

I’ve been running some of my domains on Let’s Encrypt for years now, and have never had a single user complain to me that my certs are changing too often.

Out of curiosity - do you change also the private key every time?

-- LF

Am 01.09.2018 um 18:00 schrieb Leon Fauster via CentOS centos@centos.org:

Out of curiosity - do you change also the private key every time?

I’m pretty sure LE creates a new private key, too. From a cursory glance at lego’s certificate directory on a server with a couple of dozens of LE certificates at least.

After all, changing the private key is what this is all about (showing that you’re still in charge).

Am 01.09.2018 um 20:27 schrieb Valeri Galtsev:

I just checked on my box and confirm that yes, with every renewal of certificate new key is created. I should realize that fact even before looking, as it is asymmetric encryption pair, thus the new pair cert+key is generated (and the cert [request] gets signed).

Valeri

You are commenting on a specific ACME helper tool to create LE certificates? On my side the key stays the same. And as long as it is not compromised there is no need to change it.

Alexander

On Sep 1, 2018, at 12:10 PM, Rainer Duffner rainer@ultra-secure.de wrote:

...

Am 01.09.2018 um 12:51 schrieb Pete Biggs pete@biggs.org.uk:

That was until LetsEncrypt comes along - it has the backing of some big names and *IS* an effective business model for small and private customers.

What *is* the business model of Let’s Encrypt?

They’re a nonprofit, run off of sponsorships and donations:

https://letsencrypt.org/about/ https://letsencrypt.org/donate/ https://letsencrypt.org/docs/faq/ https://letsencrypt.org/sponsors/ https://letsencrypt.org/become-a-sponsor/

Are they going to issue „Pro“ certificates at some point that cost money?

That would be incompatible with their 501(c)(3) status.

Running a CA is not expensive per se

Indeed.

Let’s Encrypt was inevitable: the compute costs of generating certs, running the back-end service, and holding the data were tiny in the 1990s and are even tinier now.

Tiny times massive equals large, so at scale there are non-trivial costs, but the old standard of ~$100/yr was rapacious for what we’d now call a domain validation (DV) or light organization validation (OV) cert.

In the beginning, the certificates had a certain level of trust with them that came both from the high prices (deterring drive-by crooks) and the fact that some sort of vetting was made to ensure that nobody could have issued a certificate for a domain they didn’t really control.

I had certs in the early days, and even back then, a standard web site cert didn’t involve a whole lot of checking.

That’s lead to the DV vs OV vs EV distinction:

https://www.ssl.com/article/dv-ov-and-ev-certificates/

If a DV-only cert is sufficient for your purposes, then Let’s Encrypt probably does all you need.

The only reason to buy a cert these days is if you want OV or EV, and if it were me, I’d skip OV and go to EV in order to get the extra assurances that the green styling in the browser asserts. For some applications, it’s worth the money.

DV-only covers a whole lot of use cases, though, including the one that started this thread.

These days, a certificate just shows that the communication is encrypted.

You may be right that there is little practical difference to a random end user between DV and OV, but I believe there is real value in EV.

There’s even talk about deprecating the special handling browsers have for EV-certificates from future versions of Mozilla.

Why?

I’m aware that it’s possible to generate a fraudulent EV cert, but to deprecate the distinction between EV and DV is to impugn the value of the CA system entirely. There’s plenty of problems in the system, which is one reason why we have the CAB Forum: untrustworthy CAs get run out of business.

That leaves transparent TLS proxy middleboxes and such, but that’s just another “Who do you trust?” argument.

I use something like this script to renew my SMTP and IMAP certificates (/etc/cron.weekly/certbot-renew):

#!/bin/sh

hostcert=/etc/letsencrypt/live/mail.example.com certlink="$(readlink "${hostcert}/cert.pem")"

test -x /usr/bin/certbot || exit 72

certbot certonly --quiet --standalone --keep-until-expiring \     -d mail.example.com \     -d imap.example.com \     --email postmaster@example.com \     --agree-tos --expand

# Exit if the cert hasn't been updated test "${certlink}" = "$(readlink "${hostcert}/cert.pem")" && exit

cat ${hostcert}/fullchain.pem ${hostcert}/privkey.pem > /usr/lib/courier/share/esmtpd.pem cat ${hostcert}/fullchain.pem ${hostcert}/privkey.pem > /usr/lib/courier/share/imapd.pem systemctl restart courier