OVMS3-idf/examples/protocols/esp_local_ctrl

ESP Local Control using HTTPS server

This example creates a esp_local_ctrl service over HTTPS transport, for securely controlling the device over local network. In this case the device name is resolved through mDNS, which in this example is my_esp_ctrl_device.local.

See the esp_local_ctrl component documentation for details.

Before using the example, run idf.py menuconfig (or idf.py menuconfig if using CMake build system) to configure Wi-Fi or Ethernet. See "Establishing Wi-Fi or Ethernet Connection" section in examples/protocols/README.md for more details.

Client Side Implementation

A python test script scripts/esp_local_ctrl.py has been provided for as a client side application for controlling the device over the same Wi-Fi network. The script relies on a pre-generated main/certs/rootCA.pem to verify the server certificate. The server side private key and certificate can also be found under main/certs, namely prvtkey.pem and cacert.pem.

After configuring the Wi-Fi, flashing and booting the device, run:

python scripts/esp_local_ctrl.py

Sample output:

python2 scripts/esp_local_ctrl.py

==== Acquiring properties information ====

==== Acquired properties information ====

==== Available Properties ====
S.N. Name             Type       Flags            Value
[ 1] timestamp (us)   TIME(us)   Read-Only        168561481
[ 2] property1        INT32                       123456
[ 3] property2        BOOLEAN    Read-Only        True
[ 4] property3        STRING

Select properties to set (0 to re-read, 'q' to quit) : 0

==== Available Properties ====
S.N. Name             Type       Flags            Value
[ 1] timestamp (us)   TIME(us)   Read-Only        22380117
[ 2] property1        INT32                       123456
[ 3] property2        BOOLEAN    Read-Only        False
[ 4] property3        STRING

Select properties to set (0 to re-read, 'q' to quit) : 2,4
Enter value to set for property (property1) : -5555
Enter value to set for property (property3) : hello world!

==== Available Properties ====
S.N. Name             Type       Flags            Value
[ 1] timestamp (us)   TIME(us)   Read-Only        55110859
[ 2] property1        INT32                       -5555
[ 3] property2        BOOLEAN    Read-Only        False
[ 4] property3        STRING                      hello world!

Select properties to set (0 to re-read, 'q' to quit) : q
Quitting...

The script also allows to connect over BLE, and provide a custom service name. To display the list of supported parameters, run:

python scripts/esp_local_ctrl.py --help

Certificates

You can generate a new server certificate using the OpenSSL command line tool.

For the purpose of this example, lets generate a rootCA, which we will use to sign the server certificates and which the client will use to verify the server certificate during SSL handshake. You will need to set a password for encrypting the generated rootkey.pem.

openssl req -new -x509 -subj "/CN=root" -days 3650 -sha256 -out rootCA.pem -keyout rootkey.pem

Now generate a certificate signing request for the server, along with its private key prvtkey.pem.

openssl req -newkey rsa:2048 -nodes -keyout prvtkey.pem -days 3650 -out server.csr -subj "/CN=my_esp_ctrl_device.local"

Now use the previously generated rootCA to process the server's certificate signing request, and generate a signed certificate cacert.pem. The password set for encrypting rootkey.pem earlier, has to be entered during this step.

openssl x509 -req -in server.csr -CA rootCA.pem -CAkey rootkey.pem -CAcreateserial -out cacert.pem -days 500 -sha256

Now that we have rootCA.pem, cacert.pem and prvtkey.pem, copy these into main/certs. Note that only the server related files (cacert.pem and prvtkey.pem) are embedded into the firmware.

Expiry time and metadata fields can be adjusted in the invocation.

Please see the openssl man pages (man openssl-req) for more details.

It is strongly recommended to not reuse the example certificate in your application; it is included only for demonstration.