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Spring Security ACL

Technology

  • Java8
  • Maven3
  • SpringBoot 1.5.8-RELEASE

Domain Object Security & Access Control Lists

Domain Object or granular access control

  • Users control some objects (possessions). And each user has the right to work only with his own possession objects
  • Secondly another user may need to use a possesion from another user (borrow)
  • In above case, the owner will grant some privileges to the borrower over that particular possession
  • Authorization model used until now is not flexible enough to handle above scenario because it define authorities per type of object. So it can define that users that have this authority can do this action on ALL objects of this type. But can't define that users that have this authority can do this action on object A of this type, but not on object B of the SAME type.
  • Granular access can be done in a manually way combining per-type authorization and custom business logic with extra checks but is not a good way because is difficult
  • More flexible and more granular mode is using Spring Security new model that allow us to define the security semantics of a specific domain object, not just a class/type of objects.
  • This model it’s a generic way of defining authorization semantics for each domain entity using what is called an access control list - ACL. And it's going to allow us full granular control over exactly which users in the system can access exactly which objects.

Access Control Lists

Structure (is managed in db)

  • Security Identity (SID): represent the principal that gets access to the domain object. The SID can also represent an authority
  • Domain Object: is composed of two entities
    • Class: the java class of the entity
    • Object Identity: the main identifier of the entity tryig to secure
  • ACL Entry: represents the actual permissions that the principal has on the domain objects. By default these are: read, write, create, delete, admin - and they’re represented with an integer bit mask
    • 32 bits mask: 5 bits for above permissions and other and rest can be used for custom types
{
  "SID" : "Mauro",
  "Domain Object": {
    "Class": "Possession",
    "ObjectId": "Car"
  },
  "Entry": "W (own)"
}

{
  "SID" : "John",
  "Domain Object": {
    "Class": "Possession",
    "ObjectId": "Car"
  },
  "Entry": "R (borrow)"
}

Database structure

CREATE TABLE IF NOT EXISTS acl_sid (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    principal BOOLEAN NOT NULL,
    sid VARCHAR(100) NOT NULL,
    UNIQUE KEY unique_acl_sid (sid, principal)
) ENGINE=InnoDB;
--
CREATE TABLE IF NOT EXISTS acl_class (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    class VARCHAR(100) NOT NULL,
    UNIQUE KEY uk_acl_class (class)
) ENGINE=InnoDB;
--
CREATE TABLE IF NOT EXISTS acl_object_identity (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    object_id_class BIGINT UNSIGNED NOT NULL,
    object_id_identity BIGINT NOT NULL,
    parent_object BIGINT UNSIGNED,
    owner_sid BIGINT UNSIGNED,
    entries_inheriting BOOLEAN NOT NULL,
    UNIQUE KEY uk_acl_object_identity (object_id_class, object_id_identity),
    CONSTRAINT fk_acl_object_identity_parent FOREIGN KEY (parent_object) REFERENCES acl_object_identity (id),
    CONSTRAINT fk_acl_object_identity_class FOREIGN KEY (object_id_class) REFERENCES acl_class (id),
    CONSTRAINT fk_acl_object_identity_owner FOREIGN KEY (owner_sid) REFERENCES acl_sid (id)
) ENGINE=InnoDB;
--
CREATE TABLE IF NOT EXISTS acl_entry (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    acl_object_identity BIGINT UNSIGNED NOT NULL,
    ace_order INTEGER NOT NULL,
    sid BIGINT UNSIGNED NOT NULL,
    mask INTEGER UNSIGNED NOT NULL,
    granting BOOLEAN NOT NULL,
    audit_success BOOLEAN NOT NULL,
    audit_failure BOOLEAN NOT NULL,
    UNIQUE KEY unique_acl_entry (acl_object_identity, ace_order),
    CONSTRAINT fk_acl_entry_object FOREIGN KEY (acl_object_identity) REFERENCES acl_object_identity (id),
    CONSTRAINT fk_acl_entry_acl FOREIGN KEY (sid) REFERENCES acl_sid (id)
) ENGINE=InnoDB;
  • Example setup
  1. Domain objects entities
@Entity
@PasswordMatches
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Email
    @NotEmpty(message = "Email is required.")
    private String email;

    @ValidPassword
    @NotEmpty(message = "Password is required.")
    private String password;

    @Transient
    @NotEmpty(message = "Password confirmation is required.")
    private String passwordConfirmation;

    public User() {
        super();
    }
    
    // setters and getters
}
@Entity
public class Possession {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    @ManyToOne
    @JoinColumn(name = "owner_id", nullable = false)
    private User owner;

    //

    public Possession() {
        super();
    }

    public Possession(String name) {
        super();
        this.name = name;
    }
    
    // getters and setters
}
  1. Artifacts of configurations
INSERT INTO acl_sid (id, principal, sid) 
VALUES
(1, 1, 'user1'),
(2, 1, 'user2');
-- 
INSERT INTO acl_class (id, class) 
VALUES
(1, 'com.maurofokker.demo.model.Possession');
--
INSERT INTO acl_object_identity 
(id, object_id_class, object_id_identity, parent_object, owner_sid, entries_inheriting) 
VALUES
(1, 1, 1, NULL, 1, 1), -- user1 Possession object identity
(2, 1, 2, NULL, 1, 1), -- Common Possession object identity
(3, 1, 3, NULL, 1, 1); -- user2 Possession object identity
  1. Entry configurations
-- each has access to their own possessions, and shared posession is shared to both users to access
INSERT INTO acl_entry 
(id, acl_object_identity, ace_order, sid, mask, granting, audit_success, audit_failure) 
VALUES
(1, 1, 0, 1, 16, 1, 0, 0), -- user1 has Admin permission for Possession 1
(2, 2, 0, 1, 16, 1, 0, 0), -- user1 has Admin permission for Common Possession 2
(3, 2, 1, 2, 1, 1, 0, 0),  -- user2 has Read permission for Common Possession 2
(4, 3, 0, 2, 16, 1, 0, 0); -- user2 has Admin permission for Eric Possession 3

References