/// <summary>
/// Returns the entities as per the specifications in the get request
/// </summary>
protected virtual async Task <GetAggregateResponse> GetAggregateImplAsync(GetAggregateArguments args)
{
// Parse the parameters
var filter = FilterExpression.Parse(args.Filter);
var select = AggregateSelectExpression.Parse(args.Select);
// Prepare the query
var query = GetRepository().AggregateQuery <TEntity>();
// Retrieve the user permissions for the current view
var permissions = await UserPermissions(Constants.Read);
var permissionsCount = permissions.Count();
// Filter out permissions with masks that would be violated by the filter argument
// orderby on the other hand is always mandated to be a subset of the selected parameters
// and those in turn must be universally visible to the user, so no need to check orderby
var defaultMask = GetDefaultMask() ?? new MaskTree();
permissions = FilterViolatedPermissionsForAggregateQuery(permissions, defaultMask, filter, select);
var filteredPermissionCount = permissions.Count();
var isPartial = permissionsCount != filteredPermissionCount;
// Apply read permissions
FilterExpression permissionsCriteria = GetReadPermissionsCriteria(permissions);
query = query.Filter(permissionsCriteria);
// Filter
query = query.Filter(filter);
// Apply the top parameter
var top = args.Top == 0 ? int.MaxValue : args.Top; // 0 means get all
top = Math.Min(top, MAXIMUM_AGGREGATE_RESULT_SIZE + 1);
query = query.Top(top);
// Apply the select, which has the general format 'Select=A,B/C,D'
query = query.Select(select);
// Load the data in memory
var result = await query.ToListAsync();
// Put a limit on the number of data points returned, to prevent DoS attacks
if (result.Count > MAXIMUM_AGGREGATE_RESULT_SIZE)
{
var msg = _localizer["Error_NumberOfDataPointsExceedsMaximum0", MAXIMUM_AGGREGATE_RESULT_SIZE];
throw new BadRequestException(msg);
}
// Finally return the result
return(new GetAggregateResponse
{
Top = args.Top,
IsPartial = isPartial,
Result = result,
RelatedEntities = new Dictionary <string, IEnumerable <Entity> >() // TODO: Add ancestors of tree dimensions
});
}
private MaskTree UpdateUserMaskAsPerAggregateSelect(AggregateSelectExpression select, MaskTree userMask)
{
if (select != null)
{
var aggSelectPaths = select.Select(e => (e.Path, e.Property));
var aggSelectMask = MaskTree.GetMaskTree(aggSelectPaths);
var aggSelectAccess = Normalize(aggSelectMask);
userMask = userMask.UnionWith(aggSelectAccess);
}
return(userMask);
}
/// <summary>
/// Removes from the permissions all permissions that would be violated by the filter or aggregate select, the behavior
/// of the system here is that when a user orders by a field that she has no full access too, she only sees the
/// rows where she can see that field, sometimes resulting in a shorter list, this is to prevent the user gaining
/// any insight over fields she has no access to by filter or order the data
/// </summary>
protected IEnumerable <AbstractPermission> FilterViolatedPermissionsForAggregateQuery(IEnumerable <AbstractPermission> permissions, MaskTree defaultMask, FilterExpression filter, AggregateSelectExpression select)
{
// Step 1 - Build the "User Mask", i.e the mask containing the fields mentioned in the relevant components of the user query
var userMask = MaskTree.BasicFieldsMaskTree();
userMask = UpdateUserMaskAsPerFilter(filter, userMask);
userMask = UpdateUserMaskAsPerAggregateSelect(select, userMask);
// Filter out those permissions whose mask does not cover the entire user mask
return(FilterViolatedPermissionsInner(permissions, defaultMask, userMask));
}
