Improved the behavior of recording event log #5
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1. Added MaxSize to avoid missing event log records if their message sizes too big Although powershell-protect can record events to Application event log on Windows, if the message size of an event is too big, the message will not be recorded due to a limitation or a bug while block and file actions work correctly. I confirmed it when It detected some of powershell empire agent and modules such as Invoke-Empire and Invoke-Mimikatz. To avoid this problem, I implemented maxSize for each event. Currently, I only limit the size of Script field. 2. Changed event log IDs In the original code, all event IDs will be 0. I changed the behavior according to the event type.
To avoid an exception if a string is null.
This reverts commit 609b960.
An exception occurs when a script content or other parts are null. This occurs a rule without checking script contents. For example, if we create a rule like this.
```
<Rule>
<Name>Non-standard powershell executable</Name>
<Conditions>
<Condition>
<Property>ApplicationName</Property>
<Operator>NotContains</Operator>
<Value>C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe</Value>
</Condition>
</Conditions>
<Actions>
<ActionRef>
<Name>File</Name>
</ActionRef>
</Actions>
</Rule>
```
And it occurs when an application name is WMI and DotNet. And the message is here.
```
Failed to analyze script. Object reference not set to an instance of an object.
at Engine.ScriptContext.get_Members()
at Engine.Analyze.Conditions.ListCondition.Analyze(ScriptContext context, Condition condition)
at Engine.Analyzer.Analyze(ScriptContext scriptContext)
at Engine.ProtectEngine.Analyze(String script, String path, String app)
```
To avoid this, I added additional checks if the contents are null or not.
|
I have changed the code to fix another problem occuring an exception. See the issue #8. |
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Added MaxSize to avoid missing event log records if their message sizes are too big
Although powershell-protect can record events to Application event log on Windows, if the message size of an event is too big, the message will not be recorded due to a limitation or a bug while block and file actions work correctly.
I confirmed it when It detected some of powershell empire agent and modules such as Invoke-Empire and Invoke-Mimikatz.
To avoid this problem, I implemented maxSize for each event. Currently, I only limit the size of Script field.
Changed event log IDs
In the original code, all event IDs will be 0. I changed the behavior according to the event type.