website: document proxy security settings

website/source/docs/agent/options.html.md

@@ -703,7 +703,13 @@ Consul will not enable TLS for the HTTP API unless the `https` port has been ass
         duration value such as `720h`. Only applies in the case where the private key or root certificate are
         left blank. Defaults to `2160h` (90 days).
 
-    * <a name="connect_proxy_defaults"></a><a href="#connect_proxy_defaults">`proxy_defaults`</a> TODO
+    * <a name="connect_proxy"></a><a href="#connect_proxy">`proxy`</a> This object allows setting options for the Connect proxies. The following sub-keys are available:
+
+        * <a name="connect_proxy_allow_managed_registration"></a><a href="#connect_proxy_allow_managed_registration">`allow_managed_api_registration`</a> Allows managed proxies to be configured with services that are registered via the Agent HTTP API. Enabling this would allow anyone with permission to register a service to define a command to execute for the proxy. By default, this is false to protect against arbitrary process execution.
+
+        * <a name="connect_proxy_allow_managed_root"></a><a href="#connect_proxy_allow_managed_root">`allow_managed_root`</a> Allows Consul to start managed proxies if Consul is running as root (EUID of the process is zero). We recommend running Consul as a non-root user. By default, this is false to protect inadvertently running external processes as root.
+
+    * <a name="connect_proxy_defaults"></a><a href="#connect_proxy_defaults">`proxy_defaults`</a> This object configures the default proxy settings for [service definitions with managed proxies](/docs/agent/services.html). It accepts the fields `exec_mode`, `daemon_command`, and `config`. These are used as default values for the respective fields in the service definition.
 
 * <a name="datacenter"></a><a href="#datacenter">`datacenter`</a> Equivalent to the
   [`-datacenter` command-line flag](#_datacenter).

website/source/docs/agent/services.html.md

@@ -17,7 +17,15 @@ or added at runtime over the HTTP interface.
 
 ## Service Definition
 
-A service definition is a script that looks like:
+To configure a service, either provide the service definition as a `-config-file` option to
+the agent or place it inside the `-config-dir` of the agent. The file
+must end in the `.json` or `.hcl` extension to be loaded by Consul. Check
+definitions can be updated by sending a `SIGHUP` to the agent.
+Alternatively, the service can be registered dynamically using the [HTTP
+API](/api/index.html).
+
+A service definition is a configuration that looks like the following. This
+example shows all possible fields, but note that only a few are required.
 
 ```javascript
 {
@@ -35,7 +43,14 @@ A service definition is a script that looks like:
         "args": ["/usr/local/bin/check_redis.py"],
         "interval": "10s"
       }
-    ]
+    ],
+    "connect": {
+      "native": false,
+      "proxy": {
+        "command": [],
+        "config": {}
+      }
+    }
   }
 }
 ```
@@ -117,12 +132,14 @@ For Consul 0.9.3 and earlier you need to use `enableTagOverride`. Consul 1.0
 supports both `enable_tag_override` and `enableTagOverride` but the latter is
 deprecated and has been removed as of Consul 1.1.
 
-To configure a service, either provide it as a `-config-file` option to
-the agent or place it inside the `-config-dir` of the agent. The file
-must end in the `.json` or `.hcl` extension to be loaded by Consul. Check
-definitions can be updated by sending a `SIGHUP` to the agent.
-Alternatively, the service can be registered dynamically using the [HTTP
-API](/api/index.html).
+The `connect` field can be specified to configure [Connect](/docs/connect/index.html)
+for a service. This field is available in Consul 1.2 and later. The `native`
+value can be set to true to advertise the service as
+[Connect-native](/docs/connect/native.html). If the `proxy` field is set
+(even to an empty object), then this will enable a
+[managed proxy](/docs/connect/proxies.html) for the service. The fields within
+`proxy` are used to configure the proxy and are specified in the
+[proxy docs](/docs/connect/proxies.html).
 
 ## Multiple Service Definitions
 

website/source/docs/connect/proxies.html.md

@@ -47,6 +47,13 @@ integrating with advanced proxies in the near future to support more complex
 configurations and higher performance. The configuration below is all for
 the built-in proxy.
 
+-> **Security note:** 1.) Managed proxies can only be configured
+via agent configuration files. They _cannot_ be registered via the HTTP API.
+And 2.) Managed proxies are not started at all if Consul is running as root.
+Both of these default configurations help prevent arbitrary process
+execution or privilege escalation. This behavior can be configured
+[per-agent](/docs/agent/options.html#connect_proxy).
+
 ### Minimal Configuration
 
 Managed proxies are configured within a