Using an outbound proxy 

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In some scenarios, you may wish to use Mattermost behind a proxy. This can be used to do things such as monitoring outbound traffic from Mattermost or controlling which websites can appear in link previews and other embedded content. If you only want to use a proxy for images, the image proxy is also an option.

Configuration 

Mattermost’s use of a proxy is configured using the HTTP_PROXY, HTTPS_PROXY and NO_PROXY environment variables.

HTTP_PROXY and HTTPS_PROXY 

The HTTP_PROXY and HTTPS_PROXY environment variables store the address of the proxy server for HTTP and HTTPS requests, respectively. This value should include the protocol and port of the proxy, such as http://192.168.4.5:3128.

If you wish to have Mattermost authenticate with your proxy, it supports HTTP basic authentication by specifying the address of the proxy such as http://mattermost:password@192.168.4.5:3128.

Note that when proxying through a proxy that uses the HTTPS protocol, you’ll need to configure your Mattermost server with the root certificate of the proxy. Otherwise, Mattermost will refuse any response from the proxy as it will detect that its connection has been intercepted.

NO_PROXY 

The NO_PROXY environment variable can be set to prevent certain requests from going through the proxy, such as to an SSO provider (e.g. GitLab or SAML) or intranet sites that should be accessible in link previews. It can be configured as a set of comma-separated IP addresses (e.g. 1.2.3.4), IP address ranges specified in CIDR notation (e.g. 1.2.3.4/8), or domain names. An IP address or domain name can also include a port number.

When a domain name is specified, the domain and all of its subdomains are matched, however a domain name with a leading . only matches the subdomains. For example, example.com matches both example.com and sub.example.com while .example.com only matches the latter.

Sample configuration 

To set these environment variables while running the Mattermost server via systemd, modify the mattermost.service like this:

Note

Be sure to replace 127.0.0.1:3128 with the correct values for your proxy servers.

[Unit]
Description=Mattermost
After=network.target
After=postgresql.service
BindsTo=postgresql.service

[Service]
Type=notify
ExecStart=/opt/mattermost/bin/mattermost
TimeoutStartSec=3600
KillMode=mixed
Restart=always
RestartSec=10
WorkingDirectory=/opt/mattermost
User=mattermost
Group=mattermost
LimitNOFILE=49152
Environment=HTTP_PROXY=http://mattermost:password@127.0.0.1:3128
Environment=HTTPS_PROXY=https://mattermost:password@127.0.0.1:3128
Environment=NO_PROXY=1.2.3.4:567,.internal.example.com,login.example.com

[Install]
WantedBy=postgresql.service

For GitLab Mattermost follow the details at https://docs.gitlab.com/ee/integration/mattermost/ instead.