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jupyterhub/docs/source/security-basics.md
2017-07-18 17:57:56 -07:00

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# Security
**IMPORTANT: You should not run JupyterHub without SSL encryption on a public network.**
---
**Deprecation note:** Removed `--no-ssl` in version 0.7.
JupyterHub versions 0.5 and 0.6 require extra confirmation via `--no-ssl` to
allow running without SSL using the command `jupyterhub --no-ssl`. The
`--no-ssl` command line option is not needed anymore in version 0.7.
---
Security is the most important aspect of configuring Jupyter. There are four main aspects of the
security configuration:
1. SSL encryption (to enable HTTPS)
2. Cookie secret (a key for encrypting browser cookies)
3. Proxy authentication token (used for the Hub and other services to authenticate to the Proxy)
4. Periodic security audits
*Note* that the **Hub** hashes all secrets (e.g., auth tokens) before storing them in its
database. A loss of control over read-access to the database should have no security impact
on your deployment.
## SSL encryption
Since JupyterHub includes authentication and allows arbitrary code execution, you should not run
it without SSL (HTTPS). This will require you to obtain an official, trusted SSL certificate or
create a self-signed certificate. Once you have obtained and installed a key and certificate you
need to specify their locations in the configuration file as follows:
```python
c.JupyterHub.ssl_key = '/path/to/my.key'
c.JupyterHub.ssl_cert = '/path/to/my.cert'
```
It is also possible to use letsencrypt (https://letsencrypt.org/) to obtain
a free, trusted SSL certificate. If you run letsencrypt using the default
options, the needed configuration is (replace `mydomain.tld` by your fully
qualified domain name):
```python
c.JupyterHub.ssl_key = '/etc/letsencrypt/live/{mydomain.tld}/privkey.pem'
c.JupyterHub.ssl_cert = '/etc/letsencrypt/live/{mydomain.tld}/fullchain.pem'
```
If the fully qualified domain name (FQDN) is `example.com`, the following
would be the needed configuration:
```python
c.JupyterHub.ssl_key = '/etc/letsencrypt/live/example.com/privkey.pem'
c.JupyterHub.ssl_cert = '/etc/letsencrypt/live/example.com/fullchain.pem'
```
Some cert files also contain the key, in which case only the cert is needed. It is important that
these files be put in a secure location on your server, where they are not readable by regular
users.
Note on **chain certificates**: If you are using a chain certificate, see also
[chained certificate for SSL](troubleshooting.md#chained-certificates-for-ssl) in the JupyterHub troubleshooting FAQ).
Note: In certain cases, e.g. **behind SSL termination in nginx**, allowing no SSL
running on the hub may be desired.
## Cookie secret
The cookie secret is an encryption key, used to encrypt the browser cookies used for
authentication. If this value changes for the Hub, all single-user servers must also be restarted.
Normally, this value is stored in a file, the location of which can be specified in a config file
as follows:
```python
c.JupyterHub.cookie_secret_file = '/srv/jupyterhub/cookie_secret'
```
The content of this file should be 32 random bytes, encoded as hex.
An example would be to generate this file with:
```bash
openssl rand -hex 32 > /srv/jupyterhub/cookie_secret
```
In most deployments of JupyterHub, you should point this to a secure location on the file
system, such as `/srv/jupyterhub/cookie_secret`. If the cookie secret file doesn't exist when
the Hub starts, a new cookie secret is generated and stored in the file. The
file must not be readable by group or other or the server won't start.
The recommended permissions for the cookie secret file are 600 (owner-only rw).
If you would like to avoid the need for files, the value can be loaded in the Hub process from
the `JPY_COOKIE_SECRET` environment variable, which is a hex-encoded string. You
can set it this way:
```bash
export JPY_COOKIE_SECRET=`openssl rand -hex 32`
```
For security reasons, this environment variable should only be visible to the Hub.
If you set it dynamically as above, all users will be logged out each time the
Hub starts.
You can also set the cookie secret in the configuration file itself,`jupyterhub_config.py`,
as a binary string:
```python
c.JupyterHub.cookie_secret = bytes.fromhex('64 CHAR HEX STRING')
```
## Proxy authentication token
The Hub authenticates its requests to the Proxy using a secret token that
the Hub and Proxy agree upon. The value of this string should be a random
string (for example, generated by `openssl rand -hex 32`). You can pass
this value to the Hub and Proxy using either the `CONFIGPROXY_AUTH_TOKEN`
environment variable:
```bash
export CONFIGPROXY_AUTH_TOKEN=`openssl rand -hex 32`
```
This environment variable needs to be visible to the Hub and Proxy.
Or you can set the value in the configuration file, `jupyterhub_config.py`:
```python
c.JupyterHub.proxy_auth_token = '0bc02bede919e99a26de1e2a7a5aadfaf6228de836ec39a05a6c6942831d8fe5'
```
If you don't set the Proxy authentication token, the Hub will generate a random key itself, which
means that any time you restart the Hub you **must also restart the Proxy**. If the proxy is a
subprocess of the Hub, this should happen automatically (this is the default configuration).
Another time you must set the Proxy authentication token yourself is if
you want other services, such as [nbgrader](https://github.com/jupyter/nbgrader)
to also be able to connect to the Proxy.
## Security audits
We recommend that you do periodic reviews of your deployment's security. It's
good practice to keep JupyterHub, configurable-http-proxy, and nodejs
versions up to date.
A handy website for testing your deployment is
[Qualsys' SSL analyzer tool](https://www.ssllabs.com/ssltest/analyze.html).