Table of Contents
Like most web applications, Guacamole can be placed behind a reverse proxy. For production deployments of Guacamole, this is highly recommended. It provides flexibility and, if your proxy is properly configured for SSL, encryption.
Proxying isolates privileged operations within native applications that can safely drop those privileges when no longer needed, using Java only for unprivileged tasks. On Linux and UNIX systems, a process must be running with root privileges to listen on any port under 1024, including the standard HTTP and HTTPS ports (80 and 443 respectively). If the servlet container instead listens on a higher port, such as the default port 8080, it can run as a reduced-privilege user, allowing the reverse proxy to bear the burden of root privileges. As a native application, the reverse proxy can make system calls to safely drop root privileges once the port is open; a Java application like Tomcat cannot do this.
Your servlet container is most likely already configured to listen for HTTP connections on port 8080 as this is the default. If this is the case, and you can already access Guacamole over port 8080 from a web browser, you need not make any further changes to its configuration.
If you have changed this, perhaps with the intent of proxying Guacamole over AJP, change it back. Using Guacamole over AJP is unsupported as it is known to cause problems, namely:
WebSocket will not work over AJP, forcing Guacamole to fallback to HTTP, possibly resulting in reduced performance.
Apache 2.4.3 and older does not support the HTTP PATCH method over AJP, preventing the Guacamole management interface from functioning properly.
The connector entry within conf/server.xml should look like
this:
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
URIEncoding="UTF-8"
redirectPort="8443" />Be sure to specify the URIEncoding="UTF-8" attribute as above to ensure
that connection names, user names, etc. are properly received by the web application. If
you will be creating connections that have Cyrillic, Chinese, Japanese, or other
non-Latin characters in their names or parameter values, this attribute is
required.
By default, when Tomcat is behind a reverse proxy, the remote IP address of the client that it sees is that of the proxy rather than the original client. In order to allow applications hosted within Tomcat, like Guacamole, to see the actual IP address of the client, you have to configure both the reverse proxy and Tomcat.
Because the remote IP address in Guacamole is used for auditing of user logins and
connections and could potentially be used for authentication, it is important that you
are either in direct control of the proxy server or you explicitly trust it. Passing
the remote IP address is done using the X-Forwarded-For header, and,
as with most HTTP headers, attackers can attempt to spoof this header in order to
manipulate the behavior of the web server, gain unauthorized access to the system,
or attempt to disguise the host or IP address they are coming from.
One final caveat: This may not work as expected if there are other upstream proxy servers between your reverse proxy and the clients access Guacamole. Other proxies or firewalls can mask the IP address of the client, and if the configuration of those is not within your control you may end up with multiple clients appearing to come from the same IP address or host. Make sure you take this into account when configuring the system and looking at the data provided.
Configuring Tomcat to pass through the remote IP address provided by the reverse
proxy in the X-Forwarded-For header requires the configuration of what
Tomcat calls a Valve. In this case, it is the
RemoteIpValve and is configured in the
conf/server.xml file, in the <Host> section:
<Valve className="org.apache.catalina.valves.RemoteIpValve"
internalProxies="127.0.0.1"
remoteIpHeader="x-forwarded-for"
remoteIpProxiesHeader="x-forwarded-by"
protocolHeader="x-forwarded-proto" />The internalProxies value should be set to the IP address
or addresses of any and all reverse proxy servers that will be accessing this Tomcat
instance directly. Often it is run on the same system that runs Tomcat, but in other
cases (for example, when running Docker), it may be on a different system/container and
may need to be set to the actual IP address of the reverse proxy system. Only proxy
servers listed in the internalProxies or
trustedProxies parameters will be allowed to manipulate the
remote IP address information. The other parameters in this configuration line allow
you to control which headers coming from the proxy server(s) are used for various
remote host information. They are as follows:
| Parameter name | Description |
|---|---|
remoteIpHeader |
The header that is queried to learn the client IP address
of the client that originated the request. The standard
value is |
remoteIpProxiesHeader |
The header that is queried to learn the IP address of the
proxy server that forwarded the request. The default value
is |
protocolHeader |
The header that is queried to determine the protocol
that the client used to connect to the service. The default
value is |
In addition to configuring Tomcat to properly handle these headers, you also may need to configure your reverse proxy appropriately to send the headers. You can find instructions for this in the section called “Nginx” - the Apache web server passes it through by default.
Nginx can be used as a reverse proxy, and supports WebSocket out-of-the-box since version 1.3. Both Apache and Nginx require some additional configuration for proxying of WebSocket to work properly.
Nginx does support WebSocket for proxying, but requires that the "Connection" and "Upgrade" HTTP headers are set explicitly due to the nature of the WebSocket protocol. From the Nginx documentation:
NGINX supports WebSocket by allowing a tunnel to be set up between a client and a back-end server. For NGINX to send the Upgrade request from the client to the back-end server, Upgrade and Connection headers must be set explicitly. ...
The proxy configuration belongs within a dedicated location block, declaring the backend hosting Guacamole
and explicitly specifying the "Connection" and "Upgrade" headers mentioned
earlier:
location /guacamole/ {
proxy_pass http://HOSTNAME:8080/guacamole/;
proxy_buffering off;
proxy_http_version 1.1;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $http_connection;
access_log off;
}Here, HOSTNAME is the hostname or IP address of the
machine hosting your servlet container, and 8080 is the
port that servlet container is configured to use. You will need to replace these
values with the correct values for your server.
Related to the RemoteIpValve configuration for tomcat, documented in
the section called “Setting up the Remote IP Valve”, the
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; line is
important if you want the X-Forwarded-For header to be passed through
to the web application server and available to applications running inside it.
Important
Do not forget to specify "proxy_buffering
off".
Most proxies, including Nginx, will buffer all data sent over the connection, waiting until the connection is closed before sending that data to the client. As Guacamole's HTTP tunnel relies on streaming data to the client over an open connection, excessive buffering will effectively block Guacamole connections, rendering Guacamole useless.
If the option "proxy_buffering off" is not specified,
Guacamole may not work.
If you wish to serve Guacamole through Nginx under a path other than
/guacamole/, the configuration will need to be altered slightly to
take cookies into account. Although Guacamole does not rely on receipt of cookies in
general, cookies are required for the proper operation of the HTTP tunnel. If the
HTTP tunnel is used, and cookies cannot be set, users may be unexpectedly denied
access to their connections.
Regardless of the location specified for the proxy, cookies set by Guacamole will
be set using its own absolute path within the backend (/guacamole/). If
this path differs from that used by Nginx, the path in the cookie needs to be
modified using proxy_cookie_path:
location /new-path/{ proxy_pass http://HOSTNAME:8080/guacamole/; proxy_buffering off; proxy_http_version 1.1; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection $http_connection; proxy_cookie_path /guacamole/ /new-path/; access_log off; }
Apache supports reverse proxy configurations through mod_proxy. Apache 2.4.5 and later also support proxying of WebSocket through a sub-module called mod_proxy_wstunnel. Both of these modules will need to be enabled for proxying of Guacamole to work properly.
Lacking mod_proxy_wstunnel, it is still possible to proxy Guacamole, but Guacamole will be unable to use WebSocket. It will instead fallback to using the HTTP tunnel, resulting in reduced performance.
Configuring Apache to proxy HTTP requests requires using the
ProxyPass and ProxyPassReverse
directives, which are provided by the mod_proxy module. These
directives describe how HTTP traffic should be routed to the web server behind the
proxy:
<Location /guacamole/>
Order allow,deny
Allow from all
ProxyPass http://HOSTNAME:8080/guacamole/ flushpackets=on
ProxyPassReverse http://HOSTNAME:8080/guacamole/
</Location>Here, HOSTNAME is the hostname or IP address of the
machine hosting your servlet container, and 8080 is the
port that servlet container is configured to use. You will need to replace these
values with the correct values for your server.
Important
Do not forget the flushpackets=on
option.
Most proxies, including mod_proxy, will buffer all data sent over the connection, waiting until the connection is closed before sending that data to the client. As Guacamole's HTTP tunnel relies on streaming data to the client over an open connection, excessive buffering will effectively block Guacamole connections, rendering Guacamole useless.
If the option flushpackets=on is not specified,
Guacamole may not work.
Apache will not automatically proxy WebSocket connections, but you can proxy them
separately with Apache 2.4.5 and later using mod_proxy_wstunnel.
After enabling mod_proxy_wstunnel a secondary
Location section can be added which explicitly proxies the
Guacamole WebSocket tunnel, located at
/guacamole/websocket-tunnel:
<Location /guacamole/websocket-tunnel>
Order allow,deny
Allow from all
ProxyPass ws://HOSTNAME:8080/guacamole/websocket-tunnel
ProxyPassReverse ws://HOSTNAME:8080/guacamole/websocket-tunnel
</Location>Lacking this, Guacamole will still work by using normal HTTP, but network latency will be more pronounced with respect to user input, and performance may be lower.
Important
The Location section for /guacamole/websocket-tunnel
must be placed after the Location section for the rest of
Guacamole.
Apache evaluates all Location sections, giving priority to the last section
that matches. If the /guacamole/websocket-tunnel section comes first,
the section for /guacamole/ will match instead, and WebSocket will
not be proxied correctly.
If you wish to serve Guacamole through Apache under a path other than
/guacamole/, the configuration required for Apache will be slightly
different than the examples above due to cookies.
Guacamole does not rely on receipt of cookies for tracking whether a user is logged in, but cookies are required for the proper operation of the HTTP tunnel. If the HTTP tunnel is used, and cookies cannot be set, users will be unexpectedly denied access to connections they legitimately should have access to.
Cookies are set using the absolute path of the web application
(/guacamole/). If this path differs from that used by Apache, the
path in the cookie needs to be modified using the
ProxyPassReverseCookiePath directive:
<Location /new-path/> Order allow,deny Allow from all ProxyPass http://HOSTNAME:8080/guacamole/ flushpackets=on ProxyPassReverse http://HOSTNAME:8080/guacamole/ ProxyPassReverseCookiePath /guacamole/ /new-path/</Location> <Location /new-path/websocket-tunnel> Order allow,deny Allow from all ProxyPass ws://HOSTNAME:8080/guacamole/websocket-tunnel ProxyPassReverse ws://HOSTNAME:8080/guacamole/websocket-tunnel </Location>
This directive is not needed for the WebSocket section, as it is not applicable. Cookies are only used by Guacamole within the HTTP tunnel.
If WebSocket is unavailable, Guacamole will fallback to using an HTTP-based tunnel. The Guacamole HTTP tunnel works by transferring a continuous stream of data over multiple short-lived streams, each associated with a separate HTTP request. By default, Apache will log each of these requests, resulting in a rather bloated access log.
There is little value in a log file filled with identical tunnel requests, so it is recommended to explicitly disable logging of those requests. Apache does provide a means of matching URL patterns and setting environment variables based on whether the URL matches. Logging can then be restricted to requests which lack this environment variable:
SetEnvIf Request_URI "^/guacamole/tunnel" dontlog CustomLog/var/log/apache2/guac.logcommon env=!dontlog
Note that if you are serving Guacamole under a path different from
/guacamole/, you will need to change the value of
Request_URI above accordingly.