Serving private data (PVT)

While developing the interfaces for HMI service, integrators face the issue of the private data protection: the UI is loaded with the JavaScript application that runs in the browser and requires authentication to access the HMI service methods. However, the application may contain components which an unauthorized user should not see: plans of the building, security cam footages, even the list of the managed items may be confidential.

One way to solve this problem is to use a front-end server for such content. However, front-end is not always necessary and, in many cases, the content structure requires access rights to certain files/folders only.

Therefore, it may involve duplicating user base and make difficult to integrate the additional authentication methods.

In the most cases, it would be sufficient to delineate access to such content with the help of the service’s PVT feature: the access rights to the certain files and folders are regulated with pvt parameter of ACLs.

The PVT feature is available at http(s)://<IP/DOMAIN>:[SVC_PORT]/pvt.

The private content must be placed in pvt folder of EVA ICS root directory.

ACL pvt parameter supports wildcards as well e.g.:

    - map.jpg
    - c1/#
    - +/content.js

will give the key access to map.jpg, all files and sub-folders of c1 folder as well as content.js file in any first-level folder.


If the client is authenticated in advance (auth cookie is set by EVA JS Framework), requests do not require k=APIKEY/TOKEN parameter.

Loading files from PVT Server

A private file can be loaded with the following request:





  • k valid API key

  • f a full relative file path, i.e. map.jpg or c2/content.js

Serving private data from EVA ICS Registry

To serve private structured data from EVA ICS registry, use the following request:


where REGISTRY-KEY - key name, relative to eva/user_data/pvt, e.g. to request a key “eva/user_data/pvt/codes/code1” use the following request:


The session key MUST have permissions either to the whole pvt data (“#”) or to specific registry folders/keys. ACLs for registry keys should start with “%/”, e.g. to grant an access to the above key, pvt ACL MUST be “%/codes/code1”. Wildcards in paths (“#”/”+”) are supported.

By default, registry data is served as JSON. To change format and/or to add locale translation, see Serving structured data.

Serving remote resources (RPVT)

The service can act as a proxy, fetching allowed resources in the local or remote networks.

Local network resources



Example: there is a chart on a storage server in the local network displaying storage usage. The chart is located at

Set rpvt permissions of the API key to:

  # .....
  - .local/

The above grants access to all files on the specified host in /charts/ folder.

Then include remote chart in the interface:

<img src="/rpvt?k=APIKEY&f=.local/" />

Optionally, the protocol schema can be specified:

<img src="/rpvt?k=APIKEY&f=.local/" />

Note that the URL schema is stripped before checking and it must be omitted in ACLs. If access to the remote resource is granted, it can be requested with both http and https.


Avoid using rpvt: [“#”], as this allows /rpvt to work as http proxy for any local and Internet resource and may open a security hole.

Remote network resources

If “.local” (or the local node name) is specified, the HMI service requests the resource. Otherwise, the HMI service works in combination with Replication service.

The remote node always receives rpvt call as “.local/resource”, so the remote replication ACL must be set to “.local/…” only.

Example of a local ACL:

  # .....
  - remote_node/

Example of a remote ACL, assigned to the replication key:

  # .....
  - .local/

Example HTML block with a chart image:

<img src="/rpvt?k=APIKEY&f=remote_node/" />