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Version: 4.4

Security

Before operating on any data in an external function, you must ensure that the user:

  • has access to context that the data is located in
  • has permission to perform the relevant action

Validating function parameters​

Before working with any data provided by a user you must validate the parameters against the definitions you have defined.

To do so you should call the validate_parameters() function, passing in the reference to your execute_parameters() function, and the complete list of parameters for the function. The function will return the validated and cleaned parameters.

The validate_parameters() function is defined on the \core_external\external_api class, and can be called as follows:

local/groupmanager/classes/external/create_groups.php
public static function execute(array $groups): array {
    [
        'groups' => $groups,
    ] = self::validate_parameters(self::execute_parameters(), [
        'groups' => $groups,
    ]);
    // ...
}

Validating access to the Moodle context​

Whenever fetching or updating any data within Moodle using an External function definition, you must validate the context that the data exists within.

To do so you should call the validate_context() function, passing the most specific context for the data.

For example, if you are working with data belonging to a specific activity, you should use the activity context. If you are working with data belonging to a course, you should use the course context.

If your function operates on multiple contexts (like a list of courses), you must validate each context right before generating any response data related to that context.

The validate_context() function is defined on the \core_external\external_api class, and can be called as follows:

local/groupmanager/classes/external/create_groups.php
public static function execute(array $groups): array {
    // ...
    foreach ($groups as $group) {
        $coursecontext = \context_course::instance($group['courseid']);
        self::validate_context($coursecontext);
        // ...
    }
}
tip

The validate_context() function will also configure the correct theme, language, and filters required to render content for the current user.

caution

You should not:

  • use the require_login function from an external function - this function is reserved for php scripts returning a web page.
  • call $PAGE->set_context() manually - this will generate warning notices.

The validate_context() function is the only correct way to write external functions.

Ensuring that a user has the appropriate rights​

Once you have confirmed that the provided data is of the correct type, and configured Moodle for the specific context, you should also ensure that all capabilities are checked correctly.

You can use the standard capability functions, including:

  • has_capability() - to check that a user has a single capability
  • has_any_capability() - to check that a user has any capability in a set
  • has_all_capability() - to check that a user has all capabilities in a set
  • require_capability() - to require a single capability
  • require_all_capabilities() - to require that a user has all capabilities in a set