# Serving via nginx on Debian and Ubuntu

This document is an extension of [the platform-independent SCGI
instructions][scgii], which may suffice for your purposes if your needs
are simple.

Here, we add more detailed information on nginx itself, plus details
about running it on Debian type OSes. We focus on Debian 10 (Buster) and

Ubuntu 20.04 here, which are common Tier 1 OS offerings for [virtual

private servers][vps] at the time of writing.  This material may not work for older OSes. It is
known in particular to not work as given for Debian 9 and older!

We also cover adding TLS to the basic configuration, because several
details depend on the host OS and web stack details. Besides, TLS is
widely considered part of the baseline configuration these days.

[scgii]: ../any/scgi.md
[vps]:   https://en.wikipedia.org/wiki/Virtual_private_server

[dof2b]: https://www.digitalocean.com/community/tutorials/how-to-protect-an-nginx-server-with-fail2ban-on-ubuntu-14-04


## <a id="tls"></a> Adding TLS (HTTPS) Support

One of the [many ways](../../ssl.wiki) to provide TLS-encrypted HTTP access
(a.k.a. HTTPS) to Fossil is to run it behind a web proxy that supports
TLS. One such option is nginx on Debian, so we show the details of that
here.

You can extend this guide to other operating systems by following the
instructions found via [the front Certbot web page][cb] instead, telling
it what OS and web stack you’re using. Chances are good that they’ve got
a good guide for you already.


### <a id="leew"></a> Configuring Let’s Encrypt, the Easy Way

If your web serving needs are simple, [Certbot][cb] can configure nginx
for you and keep its certificates up to date. Simply follow Certbot’s
[nginx on Ubuntu 20.04 LTS guide][cbnu].

Unfortunately, the setup above was beyond Certbot’s ability to cope the
last time we tried it. The use of per-subdomain files in particular
confused Certbot, so we had to [arrange these details manually](#lehw),
else the Let’s Encrypt [ACME] exchange failed in the necessary domain
validation steps.

At this point, if your configuration needs are simple, needing only a
single Internet domain and a single Fossil repo, you might wish to try
to reduce the above configuration to a more typical single-file nginx
config, which Certbot might then cope with out of the box.



### <a id="lehw"></a> Configuring Let’s Encrypt, the Hard Way

The primary motivation for this section is that it documents the manual
Certbot configuration on my public Fossil-based site.  I’m addressing
the “me” years hence who needs to upgrade to Ubuntu 22.04 or 24.04 LTS
and has forgotten all of this stuff. 😉


#### Step 1: Shifting into Manual

The first thing we’ll do is install Certbot in the normal way, but we’ll
turn off all of the Certbot automation and won’t follow through with use
of the `--nginx` plugin:

      $ sudo snap install --classic certbot
      $ sudo systemctl disable certbot.timer

Next, edit `/etc/letsencrypt/renewal/example.com.conf` to disable the
nginx plugins. You’re looking for two lines setting the “install” and
“auth” plugins to “nginx”.  You can comment them out or remove them
entirely.


#### Step 2: Configuring nginx

This is a straightforward extension to the HTTP-only configuration
[above](#config):

      server {
          server_name .foo.net;

          include local/tls-common;

          charset utf-8;

          access_log /var/log/nginx/foo.net-https-access.log;
           error_log /var/log/nginx/foo.net-https-error.log;

          # Bypass Fossil for the static Doxygen docs
          location /doc/html {
              root /var/www/foo.net;

              location ~* \.(html|ico|css|js|gif|jpg|png)$ {
                  expires 7d;
                  add_header Vary Accept-Encoding;
                  access_log off;
              }
          }

          # Redirect everything else to the Fossil instance
          location / {
              include scgi_params;
              scgi_pass 127.0.0.1:12345;
              scgi_param HTTPS "on";
              scgi_param SCRIPT_NAME "";
          }
      }
      server {
          server_name .foo.net;
          root /var/www/foo.net;
          include local/http-certbot-only;
          access_log /var/log/nginx/foo.net-http-access.log;
           error_log /var/log/nginx/foo.net-http-error.log;
      }

One big difference between this and the HTTP-only case is
that we need two `server { }` blocks: one for HTTPS service, and
one for HTTP-only service.


##### HTTP over TLS (HTTPS) Service

The first `server { }` block includes this file, `local/tls-common`:

      listen 443 ssl;



      ssl_certificate     /etc/letsencrypt/live/example.com/fullchain.pem;
      ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

      ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;

      ssl_stapling on;
      ssl_stapling_verify on;

      ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
      ssl_ciphers "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-CBC-SHA:ECDHE-ECDSA-AES256-CBC-SHA:ECDHE-ECDSA-AES128-CBC-SHA256:ECDHE-ECDSA-AES256-CBC-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-CBC-SHA:ECDHE-RSA-AES256-CBC-SHA:ECDHE-RSA-AES128-CBC-SHA256:ECDHE-RSA-AES256-CBC-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-CBC-SHA:DHE-RSA-AES256-CBC-SHA:DHE-RSA-AES128-CBC-SHA256:DHE-RSA-AES256-CBC-SHA256";
      ssl_session_cache shared:le_nginx_SSL:1m;
      ssl_prefer_server_ciphers on;
      ssl_session_timeout 1440m;

These are the common TLS configuration parameters used by all domains
hosted by this server.

The first line tells nginx to accept TLS-encrypted HTTP connections on
the standard HTTPS port. It is the same as `listen 443; ssl on;` in
older versions of nginx.

Since all of those domains share a single TLS certificate, we reference
the same `example.com/*.pem` files written out by Certbot with the
`ssl_certificate*` lines.

The `ssl_dhparam` directive isn’t strictly required, but without it, the
server becomes vulnerable to the [Logjam attack][lja] because some of
the cryptography steps are precomputed, making the attacker’s job much
easier. The parameter file this directive references should be
generated automatically by the Let’s Encrypt package upon installation,
making those parameters unique to your server and thus unguessable. If
the file doesn’t exist on your system, you can create it manually, so:

      $ sudo openssl dhparam -out /etc/letsencrypt/dhparams.pem 2048

Beware, this can take a long time. On a shared Linux host I tried it on
running OpenSSL 1.1.0g, it took about 21 seconds, but on a fast, idle
iMac running LibreSSL 2.6.5, it took 8 minutes and 4 seconds!

The next section is also optional. It enables [OCSP stapling][ocsp], a
protocol that improves the speed and security of the TLS connection
negotiation.

The next section containing the `ssl_protocols` and `ssl_ciphers` lines
restricts the TLS implementation to only those protocols and ciphers
that are currently believed to be safe and secure.  This section is the
one most prone to bit-rot: as new attacks on TLS and its associated
technologies are discovered, this configuration is likely to need to
change. Even if we fully succeed in keeping this document up-to-date in
the face of the evolving security landscape, we’re recommending static
configurations for your server: it will thus be up to you to track
changes in this document and others to merge the changes into your local
static configuration.

Running a TLS certificate checker against your site occasionally is a
good idea. The most thorough service I’m aware of is the [Qualys SSL
Labs Test][qslt], which gives the site I’m basing this guide on an “A+”
rating at the time of this writing. The long `ssl_ciphers` line above is
based on [their advice][qslc]: the default nginx configuration tells
OpenSSL to use whatever ciphersuites it considers “high security,” but
some of those have come to be considered “weak” in the time between that
judgement and the time of this writing. By explicitly giving the list of
ciphersuites we want OpenSSL to use within nginx, we can remove those
that become considered weak in the future.

<a id=”hsts”></a>There are a few things you can do to get an even better
grade, such as to enable [HSTS][hsts]:

      add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;

This prevents a particular variety of [man in the middle attack][mitm]
where our HTTP-to-HTTPS permanent redirect is intercepted, allowing the
attacker to prevent the automatic upgrade of the connection to a secure
TLS-encrypted one.  I didn’t enable that in the configuration above
because it is something a site administrator should enable only after
the configuration is tested and stable, and then only after due
consideration. There are ways to lock your users out of your site by
jumping to HSTS hastily. When you’re ready, there are [guides you can
follow][nest] elsewhere online.


##### HTTP-Only Service

While we’d prefer not to offer HTTP service at all, we need to do so for
two reasons:

*   The temporary reason is that until we get Let’s Encrypt certificates
    minted and configured properly, we can’t use HTTPS yet at all.

*   The ongoing reason is that the Certbot [ACME][acme] HTTP-01
    challenge used by the Let’s Encrypt service only runs over HTTP. This is
    not only because it has to work before HTTPS is first configured,
    but also because it might need to work after a certificate is
    accidentally allowed to lapse to get that server back into a state
    where it can speak HTTPS safely again.

So, from the second `service { }` block, we include this file to set up
the minimal HTTP service we require, `local/http-certbot-only`:

      listen 80;
      listen [::]:80;

      # This is expressed as a rewrite rule instead of an "if" because
      # http://wiki.nginx.org/IfIsEvil
      #rewrite ^(/.well-known/acme-challenge/.*) $1 break;

      # Force everything else to HTTPS with a permanent redirect.
      #return 301 https://$host$request_uri;

As written above, this configuration does nothing other than to tell
nginx that it’s allowed to serve content via HTTP on port 80 as well.
We’ll uncomment the `rewrite` and `return` directives below, when we’re
ready to begin testing.

Notice that most of the nginx directives given [above](#config) moved up
into the TLS `server { }` block, because we eventually want this site to
be as close to HTTPS-only as we can get it.


#### Step 3: Dry Run

We want to first request a dry run, because Let’s Encrypt puts some
rather low limits on how often you’re allowed to request an actual
certificate.  You want to be sure everything’s working before you do
that.  You’ll run a command something like this:

      $ sudo certbot certonly --webroot --dry-run \
         --webroot-path /var/www/example.com \
             -d example.com -d www.example.com \
             -d example.net -d www.example.net \
         --webroot-path /var/www/foo.net \
             -d foo.net -d www.foo.net

There are two key options here.

First, we’re telling Certbot to use its `--webroot` plugin instead of
the automated `--nginx` plugin. With this plugin, Certbot writes the
[ACME][acme] HTTP-01 challenge files to the static web document root
directory behind each domain.  For this example, we’ve got two web
roots, one of which holds documents for two different second-level
domains (`example.com` and `example.net`) with `www` at the third level
being optional.  This is a common sort of configuration these days, but
you needn’t feel that you must slavishly imitate it. The other web root
is for an entirely different domain, also with `www` being optional.
Since all of these domains are served by a single nginx instance, we
need to give all of this in a single command, because we want to mint a
single certificate that authenticates all of these domains.

The second key option is `--dry-run`, which tells Certbot not to do
anything permanent.  We’re just seeing if everything works as expected,
at this point.


##### Troubleshooting the Dry Run

If that didn’t work, try creating a manual test:

      $ mkdir -p /var/www/example.com/.well-known/acme-challenge
      $ echo hi > /var/www/example.com/.well-known/acme-challenge/test

Then try to pull that file over HTTP — not HTTPS! — as
`http://example.com/.well-known/acme-challenge/test`. I’ve found that
using Firefox or Safari is better for this sort of thing than Chrome,
because Chrome is more aggressive about automatically forwarding URLs to
HTTPS even if you requested “`http`”.

In extremis, you can do the test manually:

      $ curl -i http://example.com/.well-known/acme-challenge/test
      HTTP/1.1 200 OK
      Server: nginx/1.14.0 (Ubuntu)
      Date: Sat, 19 Jan 2019 19:43:58 GMT
      Content-Type: application/octet-stream
      Content-Length: 3
      Last-Modified: Sat, 19 Jan 2019 18:21:54 GMT
      Connection: keep-alive
      ETag: "5c436ac2-4"
      Accept-Ranges: bytes

      hi

The key bits you’re looking for here are the “200 OK” response code at
the start and the “hi” line at the end. (Or whatever you wrote in to the
test file.)

If you get a 301 redirect to an `https://` URI, you either haven’t
uncommented the `rewrite` line for HTTP-only service for this directory,
or there’s some other problem with the “redirect to HTTPS” config.

If you get a 404 or other error response, you need to look into your web
server logs to find out what’s going wrong.

If you’re still running into trouble, the log file written by Certbot
can be helpful.  It tells you where it’s writing the ACME files early in
each run.



#### Step 4: Getting Your First Certificate

Once the dry run is working, you can drop the `--dry-run` option and
re-run the long command above.  (The one with all the `--webroot*`
flags.) This should now succeed, and it will save all of those flag
values to your Let’s Encrypt configuration file, so you don’t need to
keep giving them.



#### Step 5: Test It

Edit the `local/http-certbot-only` file and uncomment the `redirect` and
`return` directives, then restart your nginx server and make sure it now
forces everything to HTTPS like it should:

      $ sudo systemctl restart nginx

Test ideas:

*   Visit both Fossil and non-Fossil URLs

*   Log into the repo, log out, and log back in

*   Clone via `http`: ensure that it redirects to `https`, and that
    subsequent `fossil sync` commands go directly to `https` due to the
    301 permanent redirect.

This forced redirect is why we don’t need the Fossil Admin &rarr; Access
"Redirect to HTTPS on the Login page" setting to be enabled.  Not only
is it unnecessary with this HTTPS redirect at the front-end proxy level,
it would actually [cause an infinite redirect loop if
enabled](./ssl.wiki#rloop).



#### Step 6: Switch to HTTPS Sync

Fossil remembers permanent HTTP-to-HTTPS redirects on sync since version
2.9, so all you need to do to switch your syncs to HTTPS is:

      $ fossil sync -R /path/to/repo.fossil
    

#### Step 7: Renewing Automatically

Now that the configuration is solid, you can renew the LE cert with the
`certbot` command from above without the `--dry-run` flag plus a restart
of nginx:

      sudo certbot certonly --webroot \
         --webroot-path /var/www/example.com \
             -d example.com -d www.example.com \
             -d example.net -d www.example.net \
         --webroot-path /var/www/foo.net \
             -d foo.net -d www.foo.net
      sudo systemctl restart nginx

I put those commands in a script in the `PATH`, then arrange to call that
periodically.  Let’s Encrypt doesn’t let you renew the certificate very
often unless forced, and when forced there’s a maximum renewal counter.
Nevertheless, some people recommend running this daily and just letting
it fail until the server lets you renew.  Others arrange to run it no
more often than it’s known to work without complaint.  Suit yourself.


[acme]: https://en.wikipedia.org/wiki/Automated_Certificate_Management_Environment
[cb]:   https://certbot.eff.org/
[cbnu]: https://certbot.eff.org/lets-encrypt/ubuntufocal-nginx
[hsts]: https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security
[lja]:  https://en.wikipedia.org/wiki/Logjam_(computer_security)
[mitm]: https://en.wikipedia.org/wiki/Man-in-the-middle_attack
[nest]: https://www.nginx.com/blog/http-strict-transport-security-hsts-and-nginx/
[ocsp]: https://en.wikipedia.org/wiki/OCSP_stapling
[qslc]: https://github.com/ssllabs/research/wiki/SSL-and-TLS-Deployment-Best-Practices
[qslt]: https://www.ssllabs.com/ssltest/



*[Return to the top-level Fossil server article.](../)*