# Using acme_tiny.py with LetsEncrypt on a Ubuntu Apache 2.4 System

In this example, I use ca.rpki.net as the instance name.  Of course you will want to change that.

## Preparation

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.

To keep things tidy, I create three sub-directories

```
cd
mkdir work secrets challenges
chmod 750 work
# protect secrets
chmod 700 secrets
chmod 750 challenges
```

challenges has to be readable by the web server, but this hack can only be done by root

```
chown acme:www-data /home/acme/challenges
```

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.

```
curl https://raw.githubusercontent.com/diafygi/acme-tiny/master/acme_tiny.py > acme_tiny.py
chmod 700 acme_tiny.py
```

## LetsEncrypt Account Key

I use the same LetsEncrypt account key for all servers.  so I copy it

```
rsync <somewhere>:/home/acme/secrets/account.key /home/acme/secrets
chmod 600 /home/acme/secrets/account.key
```

If you do not already have a Let's Encrypt account key, generate one per the README.md.

```
openssl genrsa 4096 > /home/acme/secrets/account.key
chmod 600 /home/acme/secrets/account.key
```

If you generate an account key, keep it very safe and use it for all LetsEncrypt transactions from now on.

## Domain Private Key

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.

```
openssl genrsa 4096 > /home/acme/secrets/domain.key
chmod 600 /home/acme/secrets/domain.key
```

## Generate the Certificate Request

As described in the README.md, generate the certificate request.  It remains constant for the initial use and subsequent certificate refresh requests.

```
openssl req -new -sha256 -key /home/acme/secrets/domain.key -subj "/CN=ca.rpki.net" > /home/acme/work/domain.csr
```

If the web site virtualizes multiple domains, 

```
cat /etc/ssl/openssl.cnf |
awk '
  {print}
  END {
        print "[SAN]";
        print "subjectAltName=DNS:permatrac.sql1.ietf.org,DNS:etherpad.sql1.ietf.org,DNS:tickets.meeting.ietf.org";
  }' |
openssl req -new -sha256 -key secrets/domain.key -subj "/" \
        -reqexts SAN -config /dev/stdin -out work/domain.csr
```

## Configure Apache to Provide Proof of Ownership

Now is the worst part, configuring Apache 2.4.  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.

LetsEncrypt fetches the challenge over port 80 from a URL of [http:your.domain/.well-known/acme-challenge/].  So we need to configure the apache server to make the challenge data readable on port 80.  This takes me from 15 minutes ot an hour to sort out. If you can suggest how to make this simpler, please do.

I created an acme.conf 

```
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined

# remember to enable this
Listen 80

Alias /.well-known/acme-challenge "/home/acme/challenges"
DocumentRoot "/home/acme/challenges"
<Directory "/home/acme/challenges">
    AllowOverride None
    Require       all granted
    </Directory>

<VirtualHost *:80>
    ServerName archive.psg.com
    ServerAdmin randy@psg.com
    <LocationMatch      "^(?!/\.well-known/acme-challenge/).+|^/$">
        Redirect        permanent  /  https://archive.psg.com/
        </LocationMatch>
    </VirtualHost>
```

Repeat the VirtualHost for all domains for which you are getting certificates.

Don't forget to restart the Apache server

```
service apache2 restart
```

It is a good check to ensure that you can browse to the challenge directory [http:ca0.rpki.net/.well-known/acme-challenge].

Getting my browsers not to fall forward to https was very painful.  So I tested as follows:

```
echo gobbledygook > challenges/foo
chmod 644 challenges/foo
curl http://ca0.rg.net/.well-known/acme-challenge/foo
gobbledygook
```

## Getting the Certificate

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.

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:

```
DEFAULT_CA = "https://acme-staging.api.letsencrypt.org"
#DEFAULT_CA = "https://acme-v01.api.letsencrypt.org"
```

When it all works, then you can go for real.

```
#!/bin/sh -x

umask 0022
H=/home/acme
WK=$H/work
SEC=$H/secrets
CH=$H/challenges

python acme_tiny.py \
    --account-key \
    $SEC/account.key \
    --csr $WK/domain.csr \
    --acme-dir $CH \
    > $WK/signed.crt

curl https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem \
    > $WK/intermediate.pem

# note that you may have the certs stored elsewhere
sudo $H/CAT $SEC/domain.key      /etc/ssl/private/ssl-cert-snakeoil.key
sudo $H/CAT $WK/signed.crt       /etc/ssl/certs/ssl-cert-snakeoil.pem
sudo $H/CAT $WK/intermediate.pem /etc/apache2/ssl.crt/server-ca.crt
#
sudo /usr/sbin/service apache2 restart
```

Where `/home/acme/CAT` is

```
/bin/cat $1 > $2
```

And you will have needed to hack /etc/sudoers to have

```
acme ALL = (root) NOPASSWD: /home/acme/CAT
acme ALL = (root) NOPASSWD: /usr/sbin/service
```

## Renewal

You can run the same script as above for certificate renewal.