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WIP: add more detail to suspicious scriptblock logging #21475

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WIP: add more detail to suspicious scriptblock logging #21475

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13 changes: 9 additions & 4 deletions src/System.Management.Automation/engine/runtime/CompiledScriptBlock.cs
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Expand Up @@ -1426,29 +1426,34 @@ internal static void LogScriptBlockCreation(ScriptBlock scriptBlock, bool force)
}

string scriptBlockText = scriptBlock.Ast.Extent.Text;
string word = SuspiciousContentChecker.Match(scriptBlockText);

string message = @"Detected term: '" + word + @"'; " + scriptBlockText;

bool written = false;

// Maximum size of ETW events is 64kb. Split a message if it is larger than 20k (Unicode) characters.
if (scriptBlockText.Length < 20000)
if (message.Length < 20000)
{
written = WriteScriptBlockToLog(scriptBlock, 0, 1, scriptBlock.Ast.Extent.Text);
written = WriteScriptBlockToLog(scriptBlock, 0, 1, message);
}
else
{
// But split the segments into random sizes (10k + between 0 and 10kb extra)
// so that attackers can't creatively force their scripts to span well-known
// segments (making simple rules less reliable).
int segmentSize = 10000 + (new Random()).Next(10000);
int segments = (int)Math.Floor((double)(scriptBlockText.Length / segmentSize)) + 1;
int segments = (int)Math.Floor((double)(message.Length / segmentSize)) + 1;
int currentLocation = 0;
int currentSegmentSize = 0;

for (int segment = 0; segment < segments; segment++)
{
currentLocation = segment * segmentSize;
// are we at the end of the string, if so only get the rest of the string
currentSegmentSize = Math.Min(segmentSize, scriptBlockText.Length - currentLocation);

string textToLog = scriptBlockText.Substring(currentLocation, currentSegmentSize);
string textToLog = message.Substring(currentLocation, currentSegmentSize);
written = WriteScriptBlockToLog(scriptBlock, segment, segments, textToLog);
}
}
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