meta-agl - meta-agl layer (core AGL)

Age	Commit message (Expand)	Author	Files	Lines
2018-05-31	3rd part of the layer/profile rework [1/2]	Jan-Simon Möller	1	-0/+10

# How to write an application on top of AGL FRAMEWORK ## Programming Languages for Applications ### Writing an HTML5 application Developers of HTML5 applications (client side) can easily create applications for AGL framework using their preferred HTML5 framework. Developers may also take advantage of powerful server side bindings to improve application behavior. Server side bindings return an application/json mine-type and can be accessed though either HTTP or Websockets. In a near future, JSON-RPC protocol should be added to complete the current x-afb-json1 protocol. Two examples of HTML5 applications are given: - [afb-client](https://gerrit.automotivelinux.org/gerrit/gitweb?p=src/app-framework-demo.git;a=tree;f=afb-client) a simple "hello world" application template - [afm-client](https://gerrit.automotivelinux.org/gerrit/gitweb?p=src/app-framework-demo.git;a=tree;f=afm-client) a simple "Home screen" application template ### Writing a Qt application Writing Qt applications is also supported. Qt offers standard API to send request through HTTP or WebSockets. It is also possible to write QML applications. A sample QML application [token-websock] is available: - [token-websock](https://gerrit.automotivelinux.org/gerrit/gitweb?p=src/app-framework-binder.git;a=blob;f=test/token-websock.qml) A simple "hello world" application in QML ### Writing a "C" application C applications can use afb-daemon binder through a websocket connection. The library **libafbwsc** is provided for C clients that need to connect with an afb-daemon binder. The program **afb-client-demo** is the C example that uses the **libafbwsc** library. Source code is available here [src/afb-client-demo.c](https://gerrit.automotivelinux.org/gerrit/gitweb?p=src/app-framework-binder.git;a=blob;f=src/afb-client-demo.c). Current implementation relies on libsystemd and file descriptors. This model may be reviewed in the future to support secure sockets and get rid of libsystemd dependency. ### Handling sessions within applications Applications should understand sessions and token management when interacting with afb-daemon binder. Applications communicate with their private binder (afb-daemon) using a network connection or any other potential connection channel. While the current version does not yet implement Unix socket, this feature might be added in the near future. Developers need to be warn that HTTP protocol is a none connected protocol and that using HTTP socket connection to authenticate clients is not supported. For this reason, the binder should authenticate the application by using a shared secret. The secret is named "token" and the identification of client is named "session.” The examples **token-websock.qml** and **afb-client** are demonstrating how authentication and sessions are managed. ### Handling sessions Bindings and other binder features need to keep track of client instances. This is especially important for bindings running as services as they may typically have to keep each client's data separated. For HTML5 applications, the web runtime handles the cookie of the session that the binder afb-daemon automatically sets. Session identifier can be set using the parameter **uuid** or **x-afb-uuid** in URI requests. Within current version of the framework session UUID is supported by both HTTP requests and websocket negotiation. ### Exchanging tokens At application start, AGL framework communicates a shared secret to both binder and client application. This initial secret is called the "**initial token**". For each of its client application, the binder manages a current active token for session management. This authentication token can be use to restrict the access to some binding's methods. The token must be included in URI request on HTTP or during websockets connection using parameter **token** or **x-afb-token**. To ensure security, tokens must be refreshed periodically. ### Example of session management In following examples, we suppose that **afb-daemon** is launched with something equivalent to: ```bash afb-daemon --port=1234 --token=123456 [...] ``` making the expectation that **AuthLogin** binding is requested as default. #### Using curl First, connects with the initial token, 123456: ```bash $ curl http://localhost:1234/api/auth/connect?token=123456 { "jtype": "afb-reply", "request": { "status": "success", "token": "0aef6841-2ddd-436d-b961-ae78da3b5c5f", "uuid": "850c4594-1be1-4e9b-9fcc-38cc3e6ff015" }, "response": {"token": "A New Token and Session Context Was Created"} } ``` It returns an answer containing session UUID, 850c4594-1be1-4e9b-9fcc-38cc3e6ff015, and a refreshed token, 850c4594-1be1-4e9b-9fcc-38cc3e6ff015. Check if session and token is valid: ```bash $ curl http://localhost:1234/api/auth/check?token=0aef6841-2ddd-436d-b961-ae78da3b5c5f\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015 { "jtype": "afb-reply", "request": {"status":"success"}, "response": {"isvalid":true} } ``` Refresh the token: ```bash $ curl http://localhost:1234/api/auth/refresh?token=0aef6841-2ddd-436d-b961-ae78da3b5c5f\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015 { "jtype": "afb-reply", "request": { "status":"success", "token":"b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9" }, "response": {"token":"Token was refreshed"} } ``` Close the session: ```bash $ curl http://localhost:1234/api/auth/logout?token=b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015 { "jtype": "afb-reply", "request": {"status": "success"}, "response": {"info":"Token and all resources are released"} } ``` Checking on closed session for uuid should be refused: ```bash $ curl http://localhost:1234/api/auth/check?token=b8ec3ec3-6ffe-448c-9a6c-efda69ad7bd9\&uuid=850c4594-1be1-4e9b-9fcc-38cc3e6ff015 { "jtype": "afb-reply", "request": { "status": "failed", "info": "invalid token's identity" } } ``` #### Using afb-client-demo - The program is packaged within AGL in the rpm **libafbwsc-dev** Here is an example of exchange using **afb-client-demo**: ```bash $ afb-client-demo ws://localhost:1234/api?token=123456 auth connect ON-REPLY 1:auth/connect: {"jtype":"afb-reply","request":{"status":"success", "token":"63f71a29-8b52-4f9b-829f-b3028ba46b68","uuid":"5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1"}, "response":{"token":"A New Token and Session Context Was Created"}} auth check ON-REPLY 2:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}} auth refresh ON-REPLY 4:auth/refresh: {"jtype":"afb-reply","request":{"status":"success", "token":"8b8ba8f4-1b0c-48fa-962d-4a00a8c9157e"},"response":{"token":"Token was refreshed"}} auth check ON-REPLY 5:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}} auth refresh ON-REPLY 6:auth/refresh: {"jtype":"afb-reply","request":{"status":"success", "token":"e83b36f8-d945-463d-b983-5d8ed73ba529"},"response":{"token":"Token was refreshed"}} ``` After closing connection, reconnect as here after: ```bash $ afb-client-demo ws://localhost:1234/api?token=e83b36f8-d945-463d-b983-5d8ed73ba529\&uuid=5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1 auth check ON-REPLY 1:auth/check: {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}} ``` Same connection check using **curl**: ```bash $ curl http://localhost:1234/api/auth/check?token=e83b36f8-d945-463d-b983-5d8ed73ba529\&uuid=5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1 {"jtype":"afb-reply","request":{"status":"success"},"response":{"isvalid":true}} ``` ### Format of replies Replies use javascript object returned as serialized JSON. This object contains at least 2 mandatory fields of name **jtype** and **request** and one optional field of name **response**. #### Template of replies This is a template of replies: ```json { "jtype": "afb-reply", "request": { "status": "success", "info": "informationnal text", "token": "e83b36f8-d945-463d-b983-5d8ed73ba52", "uuid": "5fcc3f3d-4b84-4fc7-ba66-2d8bd34ae7d1", "reqid": "application-generated-id-23456" }, "response": ....any response object.... } ``` #### Field jtype of replies The field **jtype** must have a value of type string equal to **"afb-reply"**. #### Field request of replies The field **request** must have a value of type object. This request object has at least one field named **status** and four optional fields named **info**, **token**, **uuid**, **reqid**. ##### Subfield request.status **status** must have a value of type string. This string is equal to **"success"** only in case of success. ##### Subfield request.info **info** is of type string and represent optional information added to the reply. ##### Subfield request.token **token** is of type string. It is sent either at session creation or when the token is refreshed. ##### Subfield request.uuid **uuid** is of type string. It is sent at session creation. ##### Subfield request.reqid **reqid** is of type string. It is sent in response to HTTP requests that added a parameter of name **reqid** or **x-afb-reqid** at request time. Value returns in the reply has the exact same value as the one received in the request. #### Field response of replies This field response optionally contains an object returned when request succeeded. ### Format of events Events are javascript object serialized as JSON. This object contains at least 2 mandatory fields of name **jtype** and **event** and one optional field of name **data**. #### Template of event Here is a template of event: ```json { "jtype": "afb-event", "event": "sample_api_name/sample_event_name", "data": ...any event data... } ``` #### Field jtype of event The field **jtype** must have a value of type string equal to **"afb-event"**. #### Field event of event The field **event** carries the event's name. The name of the event is made of two parts separated by a slash: the name of the name of the API that generated the event and the name of event within the API. #### Field data of event This field data if present holds the data carried by the event.