Spring ACL adding ACE when the current user has no permission on the ACL - spring

Question

Short Question: When a new user signs up on my website I need to add a read permission to a domain object. Spring ACLs does a check using the current user's permissions to see if a permission can be added. This will always fail because the user has just signed up and has no permissions on the object that they need a read permission on. Is there a way to skip the security check in certain situations?
Long question: The website I'm working on has an invite system that is done using tokens and emails. User A creates an organization and becomes the owner of that organization. User A can then invite User B to the organization by email, an email will be sent telling them to signup, etc. When User B gets the invite they sign up and the token is looked up. This token has a relation to an organization and at this point I try to give the user a ReadPermission but I get the error:
"org.springframework.security.acls.model.NotFoundException: Unable to locate a matching ACE for passed permissions and SIDs"
Is there a way around this security check?
Or
How far into Spring Security do I need to go to change this setup?

Answer 1

Found the answer to this when reading spring docs. You can use a Runnable and DelegatingSecurityContextExecutor to run the required call as a different user.
User newUser = getCurrentUser();
User notOriginalUser = accountsService.findUserById(someId);
SecurityContext context = SecurityContextHolder.createEmptyContext();
Authentication authentication = new UsernamePasswordAuthenticationToken(notOriginalUser, "doesnotmatter", authoritiesList);
context.setAuthentication(authentication);
SimpleAsyncTaskExecutor delegateExecutor = new SimpleAsyncTaskExecutor();
DelegatingSecurityContextExecutor executor = new DelegatingSecurityContextExecutor(delegateExecutor, context);
class PermissionRunnable implements Runnable {
String u;
Organization o;
PermissionRunnable(Organization org, String username) {
o = org;
u = username;
}
public void run() {
permissionsService.setReadableByPrincipal(o, new PrincipalSid(u));
}
}
Runnable originalRunnable = new PermissionRunnable(org, newUser.getUsername());
executor.execute(originalRunnable);