B1级数据库管理系统强制存取控制模型研究

The Model of Mandatory Access Control with Extended Security Label

具有强制存取控制的数据库称为 B1级数据库 .强制存取控制为所有主体和客体定义一安全级 ,安全级为一分层密级和一非分层范围组成的二元组 .现有的强制存取控制系统都采用向上写向下读的策略 ,严重地影响了系统的可用性和灵活性 .此外 ,现有的对非分层范围的安全控制规则也存在着缺陷 .针对这些问题 ,文中提出一种改进的多级安全模型 ,修改了安全级的定义和相应的安全检查规则 ,从而增强了系统的安全性和可用性 .修改后的安全级定义中将读安全级和写安全级分开 ,并且可按不同分类方法定义多个非分层范围 。

Mandatory access control (MAC) plays an important role in highly secured database systems. MAC requires that all users and resources are classified and assigned a security label, which is a combination of a hierarchical security level and non hierarchical security categories. Most MAC systems use “downward read” and “upward write” as access rules, which seriously constrains data availability. Besides, there are some flaws in the rule for category control. To solve these problems and improve both flexibility and security, this paper introduces an enhanced multilevel security (MLS) model with extended security labels and corresponding access rules. An extended label specifies a user's clearance for read and write separately, which allows the user to read and write data of appropriate sensitivity respectively. More over, an extended security label may include multiple category sets, controlling data access from different aspects. This paper also gives the formal representations of the mandatory access control model with a series of definitions and theorems as well as its access control rules. The model presented in this paper is compared with some available commercial DBMS with MAC: Trusted Oracle 7 and DM2.