Document api encryption (#1454)

components/api.rst

@@ -30,6 +30,38 @@ Configuration variables:
 
 - **port** (*Optional*, integer): The port to run the API Server on. Defaults to ``6053``.
 - **password** (*Optional*, string): The password to protect the API Server with. Defaults to no password.
+- **encryption** (*Optional*): Enable transport encryption of the API layer.
+
+  - **key** (**Required**, string): The pre-shared key for the encryption. This is a 32-byte base64 encoded string.
+    Below you can copy a key randomly generated in your browser:
+
+    .. raw:: html
+
+        <input type="text" id="api-key" onclick="this.focus();this.select()" style="width: 240px;" readonly="readonly">
+        <script>
+          // https://stackoverflow.com/a/62362724
+          function bytesArrToBase64(arr) {
+            const abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; // base64 alphabet
+            const bin = n => n.toString(2).padStart(8,0); // convert num to 8-bit binary string
+            const l = arr.length
+            let result = '';
+
+            for(let i=0; i<=(l-1)/3; i++) {
+              let c1 = i*3+1>=l; // case when "=" is on end
+              let c2 = i*3+2>=l; // case when "=" is on end
+              let chunk = bin(arr[3*i]) + bin(c1? 0:arr[3*i+1]) + bin(c2? 0:arr[3*i+2]);
+              let r = chunk.match(/.{1,6}/g).map((x,j)=> j==3&&c2 ? '=' :(j==2&&c1 ? '=':abc[+('0b'+x)]));
+              result += r.join('');
+            }
+
+            return result;
+          }
+
+          let array = new Uint8Array(32);
+          window.crypto.getRandomValues(array);
+          document.getElementById("api-key").value = bytesArrToBase64(array);
+        </script>
+
 - **services** (*Optional*, list): A list of user-defined services. See :ref:`api-services`.
 - **reboot_timeout** (*Optional*, :ref:`time <config-time>`): The amount of time to wait before rebooting when no
   client connects to the API. This is needed because sometimes the low level ESP functions report that