198 lines
No EOL
5.7 KiB
Markdown
198 lines
No EOL
5.7 KiB
Markdown
# LetsEncrypt on a Ubuntu System without Apache or nginx
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In this example, I use etherpad.noc.ietf.org as the instance name. Of course you will want to change that.
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## Preparation
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As strongly advised in the [acme_tiny README.md](https://github.com/diafygi/acme-tiny/blob/master/README.md), create a separate user acme, in which to do all this.
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To keep things tidy, I create three sub-directories
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```
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cd
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mkdir work secrets challenges
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chmod 750 work
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# protect secrets
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chmod 700 secrets
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chmod 750 challenges
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```
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And challenges needs a self-referential sub-directory
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```
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mkdir /home/acme/challenges/.well-known
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ln -s /home/acme/challenges /home/acme/challenges/.well-known/acme-challenge
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chown -R acme:www-data challenges
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chmow og+rx challenges
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...
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I do not have git on small machines, so just grab the code with fetch. Being lazy, I just fetch the source into /home/acme.
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```
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curl https://raw.githubusercontent.com/diafygi/acme-tiny/master/acme_tiny.py > acme_tiny.py
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chmod 700 acme_tiny.py
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```
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## LetsEncrypt Account Key
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I use the same LetsEncrypt account key for all servers. so I copy it
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```
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rsync <somewhere>:/home/acme/secrets/account.key /home/acme/secrets
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chmod 600 /home/acme/secrets/account.key
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```
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If you do not already have a Let's Encrypt account key, generate one per the README.md.
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```
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openssl genrsa 4096 > /home/acme/secrets/account.key
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chmod 600 /home/acme/secrets/account.key
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```
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If you generate an account key, keep it very safe and use it for all LetsEncrypt transactions from now on.
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## Domain Private Key
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The domain private key will be the server's TLS private key, and should be protected. Generate it as described in the README.md. It remains constant for the initial use and subsequent certificate refresh requests.
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```
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openssl genrsa 4096 > /home/acme/secrets/domain.key
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chmod 600 /home/acme/secrets/domain.key
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```
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## Generate the Certificate Request
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As described in the README.md, generate the certificate request. It remains constant for the initial use and subsequent certificate refresh requests.
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```
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openssl req -new -sha256 -key /home/acme/secrets/domain.key -subj "/CN=etherpad.noc.ietf.org" > /home/acme/work/domain.csr
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```
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If the web site virtualizes multiple domains,
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```
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cat /etc/ssl/openssl.cnf |
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awk '
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{print}
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END {
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print "[SAN]";
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print "subjectAltName=DNS:permatrac.sql1.ietf.org,DNS:etherpad.sql1.ietf.org,DNS:tickets.meeting.ietf.org";
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}' |
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openssl req -new -sha256 -key secrets/domain.key -subj "/" \
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-reqexts SAN -config /dev/stdin -out work/domain.csr
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```
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## Installl and Configure micro-http to Provide Proof of Ownership
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LetsEncrypt will send a challenge nonce that we have to store where they can subsequently GET it from the web server for the domain being registered. acme_tiny.py uses what it calls a challenge directory. It must be writable by the acme_tiny.py script and readable by the web server; hence the perms and ownership used above.
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LetsEncrypt fetches the challenge over port 80 from a URL of [http:your.domain/.well-known/acme-challenge/]. So we need to configure a web server to make the challenge data readable on port 80. We do not want to run full apache or ngix, so we use micro-httpd.
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```
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apt install xinetd micro-httpd
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```
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I suggest hacking `/etc/services` to use micro-httpd
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```
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#http 80/tcp www # WorldWideWeb HTTP
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#http 80/udp # HyperText Transfer Protocol
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micro_httpd 80/tcp # WorldWideWeb HTTP
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```
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Since you will use micro-http very rarely, run it out of inetd, well xinetd
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```
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cat > /etc/xinetd.d/micro_http << EOF
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service micro_httpd
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{
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disable = no
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protocol = tcp
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port = 80
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socket_type = stream
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wait = no
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user = nobody
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server = /usr/sbin/micro-httpd
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server_args = /home/acme/challenges
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}
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EOF
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service restart xinetd
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```
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It is a good check to ensure that you can browse to the challenge directory [http:etherpad.noc.ietf.org/.well-known/acme-challenge].
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Getting my browsers not to fall forward to https was very painful. So I tested as follows:
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```
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echo gobbledygook > challenges/foo
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chmod 644 challenges/foo
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```
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Then, from a remote system, this should work
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```
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curl http://etherpad.noc.ietf.org/.well-known/acme-challenge/foo
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gobbledygook
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```
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## Getting the Certificate
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I lost a number hours because I have a conservative umask. So I made a handy script to get the certificate and, while we're at it, the certificate chain from LetsEncrypt.
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Before you go for real, I strongly suggest you test using the staging server so as not to encounter LetsEncrypt's rate limiting. To do this, hack the acme_tiny.py as follows:
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```
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DEFAULT_CA = "https://acme-staging.api.letsencrypt.org"
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#DEFAULT_CA = "https://acme-v01.api.letsencrypt.org"
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```
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When it all works, then you can go for real.
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```
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#!/bin/sh -x
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umask 0022
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H=/home/acme
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WK=$H/work
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SEC=$H/secrets
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CH=$H/challenges
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python acme_tiny.py \
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--account-key \
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$SEC/account.key \
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--csr $WK/domain.csr \
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--acme-dir $CH \
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> $WK/signed.crt || exit
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curl https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem \
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> $WK/intermediate.pem
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# note that you may have the certs stored elsewhere
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sudo $H/CAT $SEC/domain.key /etc/ssl/private/ssl-cert-snakeoil.key
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sudo $H/CAT $WK/signed.crt /etc/ssl/certs/ssl-cert-snakeoil.pem
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```
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Where `/home/acme/CAT` is
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```
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/bin/cat $1 > $2
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```
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And you will have needed to hack /etc/sudoers to have
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```
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acme ALL = (root) NOPASSWD: /home/acme/CAT
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acme ALL = (root) NOPASSWD: /usr/sbin/service
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```
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## Renewal
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You can run the same script as above for certificate renewal. Put
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```
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36 0 1 */2 * /home/acme/LE
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```
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in acme's crontab.
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2022.01.09 |