caddy.json

{
  "apps": {
    "http": {
      "servers": {
        "dummy_site": {
          "listen": [
            "127.0.0.1:8080"
          ],
          "protocols": [
            "h1",
            "h2",
            "h2c",
            "h3"
          ],
          "routes": [
            {
              "handle": [
                {
                  "handler": "static_response",
                  "headers": {
                    "Location": [
                      "${REDIRECT_DOMAIN}"
                    ]
                  },
                  "status_code": 302
                }
              ]
            }
          ]
        }
      }
    },
    "layer4": {
      "servers": {
        "signal_proxy": {
          "listen": [
            ":443"
          ],
          "routes": [
            {
              "handle": [
                {
                  "handler": "tls"
                }
              ]
            },
            {
              "match": [
                {
                  "tls": {
                    "sni": [
                      "chat.signal.org",
                      "ud-chat.signal.org",
                      "storage.signal.org",
                      "cdn.signal.org",
                      "cdn2.signal.org",
                      "cdn3.signal.org",
                      "cdsi.signal.org",
                      "contentproxy.signal.org",
                      "sfu.voip.signal.org",
                      "svr2.signal.org",
                      "updates.signal.org",
                      "updates2.signal.org",
                      "backend1.svr3.signal.org",
                      "backend2.svr3.signal.org",
                      "backend3.svr3.signal.org"
                    ]
                  }
                }
              ],
              "handle": [
                {
                  "handler": "proxy",
                  "upstreams": [
                    {
                      "dial": [
                        "{l4.tls.server_name}:443"
                      ]
                    }
                  ]
                }
              ]
            },
            {
              "handle": [
                {
                  "handler": "proxy",
                  "upstreams": [
                    {
                      "dial": [
                        "127.0.0.1:8080"
                      ]
                    }
                  ]
                }
              ]
            }
          ]
        }
      }
    },
    "tls": {
      "certificates": {
        "automate": [
          "${SIGNAL_PROXY_DOMAIN}"
        ]
      }
    }
  }
}