VAPIX access for ACAP applications

From AXIS OS 11.6, ACAP applications can acquire VAPIX service account credentials in runtime. With these credentials, the ACAP application can call a local virtual host to make VAPIX requests on the device. A username and a password with high complexity are created for every credential acquisition. These credentials are only valid on the local virtual host (127.0.0.12) and aren’t stored in any file. It should only be kept in memory by the ACAP application.

Important

In AXIS OS 11.6, a first beta version of VAPIX access was provided.

In AXIS OS 11.8, the following updates were made:

The D-Bus object path changed from /com/axis/HTTPConf1/Auth to /com/axis/HTTPConf1/VAPIXServiceAccounts1.

The D-Bus interface changed from com.axis.HTTPConf1.Auth1 to com.axis.HTTPConf1.VAPIXServiceAccounts1.

The method name changed from GetVapixServiceAccountCredentials to GetCredentials.

The return format of the credentials changed.

from ('id:a0-testuser, pass:MH757eGZdsyBuAbhAQ3j2ZtRNg9xchEg',)

to ('a0-testuser:MH757eGZdsyBuAbhAQ3j2ZtRNg9xchEg',)

In AXIS OS 11.9 the VAPIX access feature reached General Availability.

Starting from AXIS OS 11.11, an ACAP application user can get SSH access by enabling Developer Mode.

Example application

vapix is an example in C that retrieves VAPIX credentials over D-Bus and makes VAPIX calls over a loopback interface.

The following steps show details on how to get VAPIX credentials in an ACAP application and can be found implemented in the example.

Modify the manifest file

Add the required D-Bus method com.axis.HTTPConf1.VAPIXServiceAccounts1.GetCredentials in the manifest file under field resources.dbus.requiredMethods.
Use a dynamic user by removing the user section from the manifest. To use this D-Bus service, the ACAP application must run as a generated user and it is not available for the general SDK user.

Example manifest

{
    "schemaVersion": "1.3.1",
    "acapPackageConf": {
        "setup": {
            "appName": "vapix_access",
            "vendor": "Axis Communications",
            "embeddedSdkVersion": "3.0",
            "runMode": "never",
            "version": "1.0.0"
        }
    },
    "resources": {
        "dbus": {
            "requiredMethods": [
                "com.axis.HTTPConf1.VAPIXServiceAccounts1.GetCredentials"
            ]
        }
    }
}

Acquire credentials

An ACAP application can acquire VAPIX service account credentials through a D-Bus call. This example uses GDBus, a high-level D-Bus library for working with D-Bus.

Establish a D-Bus connection to the system bus:

This connection allows the application to communicate over the D-Bus system.
```
 GDBusConnection *connection = g_bus_get_sync(G_BUS_TYPE_SYSTEM, NULL, &error);
```

Invoke the D-Bus method using the D-Bus connection:

The user can effectively call the method that returns the credentials by doing this.

 GVariant *username = g_variant_new("(s)", "testuser");

 GVariant *result = g_dbus_connection_call_sync (connection,
                                                 "com.axis.HTTPConf1",
                                                 "/com/axis/HTTPConf1/VAPIXServiceAccounts1",
                                                 "com.axis.HTTPConf1.VAPIXServiceAccounts1",
                                                 "GetCredentials",
                                                 username,
                                                 NULL,
                                                 G_DBUS_CALL_FLAGS_NONE,
                                                 -1,
                                                 NULL,
                                                 &error);

When the GetCredentials method is invoked, it generates credentials with the specified username and a random password, which is returned to the ACAP as a string.

Make a VAPIX call

After obtaining the credentials, it’s ready to make the actual VAPIX call. The ACAP application communicates with a local server, which then checks the given credentials (using basic access authentication) and forwards the VAPIX request.

Define a VAPIX endpoint:

VAPIX calls are essentially HTTP requests and require a URL.

 curl_easy_setopt(curl, CURLOPT_URL, "http://127.0.0.12/axis-cgi/applications/list.cgi");

Generate and set credentials:

The credentials obtained from the D-Bus call are concatenated and then added to the curl request.
```
 curl_easy_setopt(curl, CURLOPT_USERPWD, credentials);
```

Set the authentication method and make the VAPIX call:

Here, basic access authentication is used, and then the actual curl request is made.

 curl_easy_setopt(curl, CURLOPT_HTTPAUTH, CURLAUTH_ANY);

 curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_to_file);

 curl_easy_setopt(curl, CURLOPT_WRITEDATA, &file);

Test from command-line

SSH into a device and make a D-Bus call using a command-line to get VAPIX service account credentials.

Note Starting from AXIS OS 11.11, an ACAP application user can get SSH access by enabling Developer Mode.

Example call:

gdbus call \
        --system \
        --dest com.axis.HTTPConf1 \
        --object-path /com/axis/HTTPConf1/VAPIXServiceAccounts1 \
        --method com.axis.HTTPConf1.VAPIXServiceAccounts1.GetCredentials \
        "testuser"

Example response:

('a0-testuser:MH757eGZdsyBuAbhAQ3j2ZtRNg9xchEg',)

Make a VAPIX request on local virtual host 127.0.0.12 with the given credentials using curl.

Example

curl -s -u <id>:<pass> http://127.0.0.12/axis-cgi/applications/list.cgi

Where id and pass are the credentials obtained from the GDBus call. This curl command sends an HTTP GET request to the specified VAPIX endpoint with the required authentication.

Limitations

A device can hold a maximum of 200 VAPIX service accounts.
There are no VAPIX service accounts after rebooting a device. Restarting the device removes all the created credentials.
The credentials should be re-fetched each time the ACAP application starts and should only be kept in memory by the ACAP application, not stored in any file.
We officially support only the specific D-Bus method calls introduced in this feature. Use of other D-Bus methods outside of this feature is not supported and may result in undefined behavior.