# Matter OTA

## Generate CHIP OTA image

User can generate the Matter OTA image by simply enabling
`CONFIG_CHIP_OTA_IMAGE_BUILD` config option. OTA image is generated in `build`
directory with name `<project name>-ota.bin`. This image then can be used with
OTA Provider Application.

Please make sure that version number is set to correct value. Use
`CONFIG_DEVICE_SOFTWARE_VERSION` and `CONFIG_DEVICE_SOFTWARE_VERSION_NUMBER`
config options for setting software version.

Matter OTA image can also be generated using
[ota_image_tool.py](https://github.com/project-chip/connectedhomeip/blob/master/src/app/ota_image_tool.py)
script.

## Enabling OTA Requestor

-   Please make sure `CONFIG_ENABLE_OTA_REQUESTOR` config option is enabled for
    enabling OTA requestor feature.
-   Currently all-clusters-app, lighting-app, and ota-requestor-app supports OTA
    requestor functionality.
-   Build and flash any supported app, and commission it.

## Setup OTA Provider app

Setup any of the OTA Provider, commission it and install the appropriate access
control list.

-   [Linux OTA Provider](../../../examples/ota-provider-app/linux)
-   [ESP32 OTA Provider](../../../examples/ota-provider-app/esp32)

## Query for an OTA Image

### Using Console

After commissioning is successful, read the default-otaproviders list of
requestor using the command below.

```
./out/debug/chip-tool otasoftwareupdaterequestor read default-otaproviders <REQUESTOR NODE ID> 0
```

If the list does not have your provider, write into default-otaproviders list of
requestor using the command below.

```
./out/debug/chip-tool otasoftwareupdaterequestor write default-otaproviders '[{"fabricIndex": 1, "providerNodeID": <PROVIDER_NODE_ID_1>, "endpoint": 0}, {"fabricIndex": 1, "providerNodeID": <PROVIDER_NODE_ID_2>, "endpoint": 0}]' <REQUESTOR_NODE_ID> 0
```

Press Enter in requestor device console and type below query.

```
>matter ota query
```

Once the transfer is complete, OTA requestor sends ApplyUpdateRequest command to
OTA provider for applying the image. Device will restart on successful
application of OTA image.

### Using chip-tool

After commissioning is successful, announce OTA provider's presence using
chip-tool. On receiving this command OTA requestor will query for OTA image.

```
./out/debug/chip-tool otasoftwareupdaterequestor announce-otaprovider <PROVIDER NODE ID> 0 0 0 <REQUESTOR NODE ID> 0
```

## Encrypted OTA

ESP32 supports transferring encrypted OTA images. Currently, an application
image can be encrypted/decrypted using an RSA-3072 key pair.

### Firmware Changes

-   Enable configuration options for OTA requestor and Encrypted OTA:

    ```
    CONFIG_ENABLE_OTA_REQUESTOR=y
    CONFIG_ENABLE_ENCRYPTED_OTA=y
    ```

-   Applications need to provide the key pair to the OTA image processor using
    the `InitEncryptedOTA()` API to decrypt the received OTA image.

-   For testing purposes, in `examples/lighting-app/esp32`, there is a logic of
    embedding the private key in the firmware. To quickly test, please generate
    the key pair and rename it as `esp_image_encryption_public_key.pem` and copy
    it to directory `examples/lighting-app/esp32`.

Please follow the steps below to generate an application image for OTA upgrades:

1. Generate a new RSA-3072 key pair or use an existing one.

    - To generate a key pair, use the following command:

        ```
        openssl genrsa -out esp_image_encryption_key.pem 3072
        ```

    - Extract the public key from the key pair:
        ```
        openssl rsa -in esp_image_encryption_key.pem -pubout -out esp_image_encryption_public_key.pem
        ```

2. Encrypt the application binary using the
   [esp_enc_img_gen.py](https://github.com/espressif/idf-extra-components/blob/master/esp_encrypted_img/tools/esp_enc_img_gen.py)
   script.

    - Use the following command to encrypt the OTA image with the public key:

        ```
        python3 esp_enc_img_gen.py encrypt lighting-app.bin esp_image_encryption_public_key.pem lighting-app-encrypted.bin
        ```

    - Append the Matter OTA header:
        ```
        src/app/ota_image_tool.py create --vendor-id 0xFFF1 --product-id 0x8000 --version 2 --version-str "v2.0" -da sha256 lighting-app-encrypted.bin lighting-app-encrypted-ota.bin
        ```

3. Use the `lighting-app-encrypted-ota.bin` file with the OTA Provider app.

## Delta OTA

Delta OTA Updates is a feature that enables Over-the-Air (OTA) firmware update
with compressed delta binaries. Patch files have smaller size than the original
firmware file, which reduces the time and network usage to download the file
from the server. Also, no additional storage partition is required for the
"patch".

### Firmware Changes

-   Enable configuration options for OTA requestor and Delta OTA:

    ```
    CONFIG_ENABLE_OTA_REQUESTOR=y
    CONFIG_ENABLE_DELTA_OTA=y
    ```

Please follow the steps below to generate an application image for OTA upgrades:

1. Delta binary needs to be generated using binary delta encoding in Python
   3.6+. You can install `detools` using the following command.

    ```
    pip install detools>=0.49.0
    ```

2. Generate delta binary.

    ```
    python managed_components/espressif__esp_delta_ota/examples/https_delta_ota/tools/esp_delta_ota_patch_gen.py --chip <chip> --base_binary <base-binary> --new_binary <new-binary> --patch_file_name <patch-file-name.bin>
    ```

3. Append the Matter OTA header:
   `src/app/ota_image_tool.py create --vendor-id 0xFFF1 --product-id 0x8000 --version 2 --version-str "v2.0" -da sha256 <patch-file-name.bin> lighting-app-delta-ota.bin`

4. Use the `lighting-app-delta-ota.bin` file with the OTA Provider app.

## Encrypted Delta OTA

To use encrypted delta OTA, follow the below steps.

### Firmware Changes

-   Enable configuration options for OTA requestor, Delta OTA and Encrypted OTA:

    ```
    CONFIG_ENABLE_OTA_REQUESTOR=y
    CONFIG_ENABLE_DELTA_OTA=y
    CONFIG_ENABLE_ENCRYPTED_OTA=y
    ```

1. Follow the step of `Generate a new RSA-3072 key pair or use an existing one`
   of
   [Encrypted OTA](https://github.com/project-chip/connectedhomeip/blob/master/docs/guides/esp32/ota.md#encrypted-ota)
   to build your binary.

2. Create delta binary as shown in `Generate delta binary` of
   [Delta OTA](https://github.com/project-chip/connectedhomeip/blob/master/docs/guides/esp32/ota.md#delta-ota)

3. Encrypt the application binary.

4. Append the Matter OTA header.