Question

我正在解析从脱机配置文件审核生成的.nessus文件。我已经为ReportItem节点设置了一个Linq并验证了命名空间是否正常，但是当我尝试获取cm:compliance-solution值时，它返回null（验证此元素中也有一个值）。

这是我正在使用的Linq--fixText变量是问题所在（已通过注释掉所有其他注释来验证）

XElement xelement = XElement.Load(fileName);
IEnumerable<XElement> findings = xelement.Elements();
XNamespace ns = xelement.GetNamespaceOfPrefix("cm");

var findingDetails = from f in findings.Descendants("ReportItem")
             select new
                 {
                      title = f.Element(ns + "compliance-check-name").Value,
                      description = f.Element("description").Value,
                      vulLevel = f.Element(ns + "compliance-result").Value,
                      fixText = f.Element(ns + "compliance-solution").Value,
                      testID = f.Element(ns + "compliance-check-id").Value,
                      source = f.Element(ns + "compliance-audit-file").Value
                 };

这是我正在使用的.nessus文件示例：

<?xml version="1.0" ?>
<NessusClientData_v2 xmlns:cm="http://www.nessus.org/cm">
<Policy><policyName>Offline Config Audit</policyName>
</Policy>
<Report name="Router">
<ReportHost name="router-001.config"><HostProperties>
<tag name="source_type">offline_audit</tag>
<tag name="source_name">Cisco</tag>
<tag name="operating-system">Cisco IOS</tag>
<tag name="host-fqdn">router-001</tag>
<tag name="HOST_END">Fri Jun 29 09:56:38 2018</tag>
</HostProperties>
<ReportItem port="0" svc_name="general" protocol="tcp" severity="2" pluginID="46689" pluginName="Cisco IOS Compliance Checks" pluginFamily="Policy Compliance">
<compliance>true</compliance>
<fname>cisco_compliance_check.nbin</fname>
<plugin_modification_date>2018/05/31</plugin_modification_date>
<plugin_name>Cisco IOS Compliance Checks</plugin_name>
<plugin_publication_date>2010/05/17</plugin_publication_date>
<plugin_type>local</plugin_type>
<risk_factor>None</risk_factor>
<script_version>$Revision: 1.278 $</script_version>
<cm:compliance-check-name>NET-VLAN-024 - Restricted VLAN not assigned to non-802.1x device.</cm:compliance-check-name>
<description>&quot;NET-VLAN-024 - Restricted VLAN not assigned to non-802.1x device.&quot; : [WARNING] The SA will ensure a packet filter is implemented to filter the enclave traffic to and from printer VLANs to allow only print traffic.

 A firewall rule set can filter network traffic within the printer VLAN to only expected printer protocols. The SA managing the local enclave should identify the printer port traffic within the enclave. Ports commonly used by printers are typically tcp port 515, 631, 1782 and tcp ports 9100, 9101, 9102 but others are used throughout the industry. The SA can review RFC 1700 Port Assignments and review printer vendor documents for the filter rule-set.

 NOTE: This check is derived from the L3 switch guidance, if the scan target is a router the check can be ignored.
 NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution : 

Define the filter on the VLAN ACL or build a firewall ruleset to accomplish the requirment.

See Also : 

https://iasecontent.disa.mil/stigs/zip/U_Network_Perimeter_Router_L3_Switch_V8R28_STIG.zip

Reference(s) : 

8500.2|ECND-2,CAT|II,Rule-ID|SV-20089r1_rule,STIG-ID|NET-VLAN-024,Vuln-ID|V-18545 </description>
<cm:compliance-audit-file>DISA_STIG_Cisco_Perimeter_Router_L3_Switch_V8R28.audit</cm:compliance-audit-file>
<cm:compliance-check-id>acfebcd97143973eabbc5132d9035dcc</cm:compliance-check-id>
<cm:compliance-info>The SA will ensure a packet filter is implemented to filter the enclave traffic to and from printer VLANs to allow only print traffic.

 A firewall rule set can filter network traffic within the printer VLAN to only expected printer protocols. The SA managing the local enclave should identify the printer port traffic within the enclave. Ports commonly used by printers are typically tcp port 515, 631, 1782 and tcp ports 9100, 9101, 9102 but others are used throughout the industry. The SA can review RFC 1700 Port Assignments and review printer vendor documents for the filter rule-set.

 NOTE: This check is derived from the L3 switch guidance, if the scan target is a router the check can be ignored.
 NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
</cm:compliance-info>
<cm:compliance-result>WARNING</cm:compliance-result>
<cm:compliance-reference>8500.2|ECND-2,CAT|II,Rule-ID|SV-20089r1_rule,STIG-ID|NET-VLAN-024,Vuln-ID|V-18545
</cm:compliance-reference>
<cm:compliance-solution>Define the filter on the VLAN ACL or build a firewall ruleset to accomplish the requirment.
</cm:compliance-solution>
<cm:compliance-see-also>https://iasecontent.disa.mil/stigs/zip/U_Network_Perimeter_Router_L3_Switch_V8R28_STIG.zip
</cm:compliance-see-also>
</ReportItem>
</ReportHost>
</Report>
</NessusClientData_v2>

错误详细信息：

System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.

Answer 1

我针对该示例运行了代码，一切正常。

尝试在选择部分中使用 ?. Value ，以更轻松地找到空值。

具有命名空间的Linq XML Xelement返回Null

1 个答案: