mirror of https://github.com/zulip/zulip.git
215 lines
8.7 KiB
Markdown
215 lines
8.7 KiB
Markdown
# Installing SSL Certificates
|
|
|
|
To keep your communications secure, Zulip runs over HTTPS only.
|
|
You'll need an SSL/TLS certificate.
|
|
|
|
Fortunately, since about 2017, new options can make getting and
|
|
maintaining a genuine, trusted-by-browsers certificate no longer the
|
|
chore (nor expense) that it used to be.
|
|
|
|
## Manual install
|
|
|
|
If you already have an SSL certificate, just install (or symlink) its
|
|
files into place at the following paths:
|
|
* `/etc/ssl/private/zulip.key` for the private key
|
|
* `/etc/ssl/certs/zulip.combined-chain.crt` for the certificate.
|
|
|
|
Your certificate file should contain not only your own certificate but
|
|
its **full chain, including any intermediate certificates** used by
|
|
your certificate authority (CA). See the [nginx
|
|
documentation][nginx-chains] for details on what this means. If
|
|
you're missing part of the chain, your server may work with some
|
|
browsers, but not others and not the Zulip mobile and desktop apps.
|
|
The desktop apps support [configuring a custom CA][desktop-certs] to
|
|
allow validation of certificates generated by an internal CA.
|
|
|
|
[nginx-chains]: https://nginx.org/en/docs/http/configuring_https_servers.html#chains
|
|
|
|
### Testing
|
|
|
|
Just trying in a browser is not an adequate test, because some
|
|
browsers ignore errors that others don't.
|
|
|
|
Two good tests include:
|
|
|
|
* If your server is accessible from the public Internet, use the [SSL
|
|
Labs tester][ssllabs-tester]. Be sure to check for "Chain issues";
|
|
if any, your certificate file is missing intermediate certificates.
|
|
|
|
* Alternatively, run a command like `curl -SsI https://zulip.example.com`
|
|
(using your server's URL) from a machine that can reach your server.
|
|
Make sure that on the same machine, `curl -SsI
|
|
https://incomplete-chain.badssl.com` gives an error; `curl` on some
|
|
machines, including Macs, will accept incomplete chains.
|
|
|
|
[ssllabs-tester]: https://www.ssllabs.com/ssltest/analyze.html
|
|
|
|
## Certbot (recommended)
|
|
|
|
[Let's Encrypt](https://letsencrypt.org/) is a free, completely
|
|
automated CA launched in 2016 to help make HTTPS routine for the
|
|
entire Web. Zulip offers a simple automation for
|
|
[Certbot](https://certbot.eff.org/), a Let's Encrypt client, to get
|
|
SSL certificates from Let's Encrypt and renew them automatically.
|
|
|
|
We recommend most Zulip servers use Certbot. You'll want something
|
|
else if:
|
|
* you have an existing workflow for managing SSL certificates
|
|
that you prefer;
|
|
* you need wildcard certificates (support from Let's Encrypt planned
|
|
for [early 2018][letsencrypt-wildcard]); or
|
|
* your Zulip server is not on the public Internet. (In this case you
|
|
can [still use Certbot][certbot-manual-mode], but it's less
|
|
convenient; and you'll want to ignore Zulip's automation.)
|
|
|
|
[letsencrypt-wildcard]: https://letsencrypt.org/2017/07/06/wildcard-certificates-coming-jan-2018.html
|
|
[certbot-manual-mode]: https://certbot.eff.org/docs/using.html#manual
|
|
|
|
### At initial Zulip install
|
|
|
|
To enable the Certbot automation when first installing Zulip, just
|
|
pass the `--certbot` flag when [running the install script][doc-install-script].
|
|
|
|
The `--hostname` and `--email` options are required when using
|
|
`--certbot`. You'll need the hostname to be a real DNS name, and the
|
|
Zulip server machine to be reachable by that name from the public
|
|
Internet.
|
|
|
|
If you need to configure a multiple domain certificate, you can generate
|
|
one as described in the section below after installing Zulip.
|
|
|
|
[doc-install-script]: ../production/install.html#step-2-install-zulip
|
|
|
|
### After Zulip is already installed
|
|
|
|
To enable the Certbot automation on an already-installed Zulip
|
|
server, run the following commands:
|
|
```
|
|
sudo -s # If not already root
|
|
/home/zulip/deployments/current/scripts/setup/setup-certbot --email=EMAIL HOSTNAME [HOSTNAME2...]
|
|
```
|
|
where HOSTNAME is the domain name users see in their browser when
|
|
using the server (e.g., `zulip.example.com`), and EMAIL is a contact
|
|
address for the server admins. Additional hostnames can also be
|
|
specified to issue a certificate for multiple domains.
|
|
|
|
### How it works
|
|
|
|
When the Certbot automation in Zulip is first enabled, by either
|
|
method, it creates an account for the server at the Let's Encrypt CA;
|
|
requests a certificate for the given hostname; proves to the CA that
|
|
the server controls the website at that hostname; and is then given a
|
|
certificate. (For details, refer to
|
|
[Let's Encrypt](https://letsencrypt.org/how-it-works/).)
|
|
|
|
Then it records a flag in `/etc/zulip/zulip.conf` saying Certbot is in
|
|
use and should be auto-renewed. A cron job checks that flag, then
|
|
checks if any certificates are due for renewal, and if they are (so
|
|
approximately once every 60 days), repeats the process of request,
|
|
prove, get a fresh certificate.
|
|
|
|
|
|
## Self-signed certificate
|
|
|
|
If you aren't able to use Certbot, you can generate a self-signed SSL
|
|
certificate. This can be convenient for testing, but isn't
|
|
recommended for production, as it is insecure. The Zulip desktop and
|
|
mobile apps will not connect to a server if they cannot validate its
|
|
SSL certificate. The desktop apps support [configuring a custom
|
|
certificate authority][desktop-certs] to allow validation of an
|
|
internal certificate.
|
|
|
|
To generate a self-signed certificate when first installing Zulip,
|
|
just pass the `--self-signed-cert` flag when
|
|
[running the install script][doc-install-script].
|
|
|
|
To generate a self-signed certificate for an already-installed Zulip
|
|
server, run the following commands:
|
|
```
|
|
sudo -s # If not already root
|
|
/home/zulip/deployments/current/scripts/setup/generate-self-signed-cert HOSTNAME
|
|
```
|
|
where HOSTNAME is the domain name (or IP address) to use on the
|
|
generated certificate.
|
|
|
|
After replacing the certificates, you need to reload `nginx` by
|
|
running the following as `root`:
|
|
```
|
|
service nginx reload
|
|
```
|
|
|
|
[desktop-certs]: https://zulip.com/help/custom-certificates
|
|
|
|
|
|
## Troubleshooting
|
|
|
|
### The Android app can't connect to the server
|
|
|
|
This is most often caused by an incomplete certificate chain. See
|
|
discussion in the [Manual install](#manual-install) section above.
|
|
|
|
|
|
### The iOS app can't connect to the server
|
|
|
|
This can be caused by a server set up to support only TLS 1.1 or
|
|
older (including TLS 1.0, SSL 3, or SSL 2.)
|
|
|
|
TLS 1.2 has been a standard for over 10 years, and all modern web
|
|
server software supports it. Starting in early 2020, all major
|
|
browsers [will *require* TLS 1.2 or later][tls12-required-news], and
|
|
will refuse to connect over TLS 1.1 or older. And on iOS, Apple [has
|
|
since iOS 9][apple-ats] required TLS 1.2 for all connections made by
|
|
apps, unless the app specifically opts into lower security.
|
|
|
|
[tls12-required-news]: https://www.thesslstore.com/blog/apple-microsoft-google-disable-tls-1-0-tls-1-1/
|
|
[apple-ats]: https://developer.apple.com/library/archive/releasenotes/General/WhatsNewIniOS/Articles/iOS9.html
|
|
|
|
If your server is reachable from the public Internet, a convenient way
|
|
to check what TLS versions it supports is the [SSL Labs
|
|
tester][ssllabs-tester].
|
|
|
|
To resolve this issue, update your server to support TLS 1.2,
|
|
and preferably also TLS 1.3. For nginx, see [the `ssl_protocols`
|
|
directive][nginx-doc-protocols] in your configuration.
|
|
|
|
[nginx-doc-protocols]: https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_protocols
|
|
|
|
|
|
### The Android app connects to the server on some devices but not others
|
|
|
|
An issue on Android 7.0 ([report][android7.0-tls-issue],
|
|
[description][android7.0-tls-issue-so]) in the system TLS/SSL stack,
|
|
which the Zulip app relies on, makes it finicky about the server's TLS
|
|
configuration.
|
|
|
|
[android7.0-tls-issue]: https://issuetracker.google.com/issues/37122132#comment13
|
|
[android7.0-tls-issue-so]: https://stackoverflow.com/a/42047877
|
|
|
|
The issue is that Android 7.0 supports only the curve `secp256r1` when
|
|
doing elliptic-curve cryptography for TLS, and not other curves like
|
|
`secp384r1` or `secp512r1`. If your server's TLS/SSL configuration
|
|
offers only other curves, then Android 7.0 clients will be unable to
|
|
connect.
|
|
|
|
By default `nginx` (and therefore a Zulip server) offers the
|
|
`secp256r1` curve among others, and so everything works. You can
|
|
control the offered curves with `ssl_ecdh_curve` in the `nginx`
|
|
configuration on your server. See [nginx docs][nginx-doc-curve] for
|
|
details.
|
|
|
|
[nginx-doc-curve]: https://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_ecdh_curve
|
|
|
|
Two signs for diagnosing this issue in contrast to some other root
|
|
cause:
|
|
|
|
* This issue affects only Android 7.0; it's fixed in Android 7.1.1 and
|
|
later.
|
|
|
|
* If your server is reachable from the public Internet, use the [SSL
|
|
Labs tester][ssllabs-tester]. Under "Cipher Suites" you may see
|
|
lines beginning with `TLS_ECDHE`, for cipher suites which use
|
|
elliptic-curve cryptography. These lines will have further text
|
|
like `ECDH secp256r1` or `ECDH secp384r1`, which identifies specific
|
|
elliptic curves your server offers to use. This issue applies if
|
|
your server does not offer `secp256r1`.
|