比较 XACML 策略中的两个多元素属性

Posted 2023-04-13

【中文标题】比较 XACML 策略中的两个多元素属性

【英文标题】：Compare two multi-element attributes in XACML policy

【发布时间】：2019-05-31 13:36:49

【问题描述】：

考虑一个主题和对象都具有如下定义的标签：

subject/object label = [i1, i2, ..., in]，其中i 是另一个主题的subjectId。

在策略 (ALFA/XACML) 中，我如何对主题和对象标签进行比较，以使两个列表中的元素都不相同。

例如：

subject_label = [i2, i4, i9]
object_label  = [i1, i3, i7, i9]

结果将是DENY，因为两个标签都包含i9。如果在任何列表中均未找到匹配项，则访问结果将为 PERMIT。

【参考方案1】：

您希望使用的是stringAtLeastOneMemberOf（或其他数据类型的等价物）。这个函数有两个参数：

一包字符串类型 一包字符串类型

如果第一个包中至少有一个值等于第二个包中的一个值，则返回 true。对于字符串，比较区分大小写。

namespace com.axiomatics
    /**
     * Ths policy will checks the contents of the user label and the the resource label.
     * It will deny access if there is at least one value in the user label equal to at least
     * one value in the resource label.
     */
    policy denyIfSameContent
        apply firstApplicable
        /**
         * This rule will deny access is user.label contains at least 1 value that is also present
         * in object.label 
         */
        rule denyIfSameContent
            deny
            condition stringAtLeastOneMemberOf(user.label, object.label)
        
    

这里是 XACML/XML 表示：

<?xml version="1.0" encoding="UTF-8"?><!--This file was generated by the 
    ALFA Plugin for Eclipse from Axiomatics AB (http://www.axiomatics.com). --><!--Any modification to this file will 
    be lost upon recompilation of the source ALFA file -->
<xacml3:Policy
    xmlns:xacml3="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17"
    PolicyId="http://axiomatics.com/alfa/identifier/com.axiomatics.denyIfSameContent"
    RuleCombiningAlgId="urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:first-applicable"
    Version="1.0">
    <xacml3:Description>Ths policy will checks the contents of the user
        label and the the resource label.&#13;
        It will deny access if there is at least one value in the user label
        equal to at least&#13;
        one value in the resource label.
    </xacml3:Description>
    <xacml3:PolicyDefaults>
        <xacml3:XPathVersion>http://www.w3.org/TR/1999/REC-xpath-19991116
        </xacml3:XPathVersion>
    </xacml3:PolicyDefaults>
    <xacml3:Target />
    <xacml3:Rule Effect="Deny"
        RuleId="com.axiomatics.denyIfSameContent.denyIfSameContent">
        <xacml3:Description>This rule will deny access is user.label contains
            at least 1 value that is also present&#13;
            in object.label
        </xacml3:Description>
        <xacml3:Target />
        <xacml3:Condition>
            <xacml3:Apply
                FunctionId="urn:oasis:names:tc:xacml:1.0:function:string-at-least-one-member-of">
                <xacml3:AttributeDesignator
                    AttributeId="com.axiomatics.user.label"
                    Category="urn:oasis:names:tc:xacml:1.0:subject-category:access-subject"
                    DataType="http://www.w3.org/2001/XMLSchema#string"
                    MustBePresent="false" />
                <xacml3:AttributeDesignator
                    AttributeId="com.axiomatics.object.label"
                    Category="urn:oasis:names:tc:xacml:3.0:attribute-category:resource"
                    DataType="http://www.w3.org/2001/XMLSchema#string"
                    MustBePresent="false" />
            </xacml3:Apply>
        </xacml3:Condition>
    </xacml3:Rule>
</xacml3:Policy>

【讨论】：

Eclipse 插件（alfa-to-xacml）似乎无法识别您在示例中的apply firstApplicable

您是否在 Eclipse 项目中包含了 system.alfa？

是的，我做到了。问题是我之前定义了denyOverrides。问题已解决，谢谢！

这是一篇关于算法组合的好文章：axiomatics.com/blog/understanding-xacml-combining-algorithms