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Fix CVE-2018-8415 #8253

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Merged
TravisEz13 merged 5 commits into from
Nov 13, 2018
Merged

Fix CVE-2018-8415 #8253

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324a284
log null character in a scriptblock as `\u2400`
TravisEz13 Aug 20, 2018
f06f0ec
Add test for scriptblock logging on mac with null character
TravisEz13 Aug 21, 2018
ec12b15
add test for scriptblock logging with null character on Linux
TravisEz13 Aug 22, 2018
9f47602
Add test case for windows script block logging with null character
TravisEz13 Aug 24, 2018
9dbb973
Fix CodeFactor issues
TravisEz13 Nov 13, 2018
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12 changes: 12 additions & 0 deletions src/System.Management.Automation/engine/runtime/CompiledScriptBlock.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1317,6 +1317,7 @@ private static bool WriteScriptBlockToLog(ScriptBlock scriptBlock, int segment,
// See if we need to encrypt the event log message. This info is all cached by Utils.GetPolicySetting(),
// so we're not hitting the configuration file for every script block we compile.
ProtectedEventLogging logSetting = Utils.GetPolicySetting<ProtectedEventLogging>(Utils.SystemWideOnlyConfig);
bool wasEncoded = false;
if (logSetting != null)
{
lock (s_syncObject)
Expand All @@ -1334,6 +1335,7 @@ private static bool WriteScriptBlockToLog(ScriptBlock scriptBlock, int segment,
// version.
if (s_encryptionRecipients != null)
{
// Encrypt the raw Text from the scriptblock. The user may have to deal with any control characters in the data.
ExecutionContext executionContext = LocalPipeline.GetExecutionContextFromTLS();
ErrorRecord error = null;
byte[] contentBytes = System.Text.Encoding.UTF8.GetBytes(textToLog);
Expand All @@ -1355,11 +1357,21 @@ private static bool WriteScriptBlockToLog(ScriptBlock scriptBlock, int segment,
else
{
textToLog = encodedContent;
wasEncoded = true;
}
}
}
}

if (!wasEncoded)
{
// The logging mechanism(s) cannot handle null and rendering may not be able to handle
// null as we have the string defined as a null terminated string in the manifest.
// So, replace null characters with the Unicode `SYMBOL FOR NULL`
// We don't just remove the characters to preserve the fact that a null character was there.
textToLog = textToLog.Replace('\u0000', '\u2400');
}

if (scriptBlock._scriptBlockData.HasSuspiciousContent)
{
PSEtwLog.LogOperationalWarning(PSEventId.ScriptBlock_Compile_Detail, PSOpcode.Create, PSTask.ExecuteCommand, PSKeyword.UseAlwaysOperational,
Expand Down
72 changes: 72 additions & 0 deletions test/powershell/Host/Logging.Tests.ps1
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Original file line number Diff line number Diff line change
Expand Up @@ -216,6 +216,35 @@ $pid
$createdEvents[2].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f "Write\-Verbose 'testheader123' ;Write\-verbose 'after'")
}

It 'Verifies scriptblock logging with null character' -Skip:(!$IsSupportedEnvironment) {
$configFile = WriteLogSettings -LogId $logId -ScriptBlockLogging -LogLevel Verbose
$script = @'
$pid
& ([scriptblock]::create("Write-Verbose 'testheader123$([char]0x0000)' ;Write-verbose 'after'"))
'@
$testFileName = 'test01.ps1'
$testScriptPath = Join-Path -Path $TestDrive -ChildPath $testFileName
$script | Out-File -FilePath $testScriptPath -Force
$null = & $powershell -NoProfile -SettingsFile $configFile -Command $testScriptPath

# Get log entries from the last 100 that match our id and are after the time we launched Powershell
$items = Get-PSSysLog -Path $SyslogFile -Id $logId -Tail 100 -Verbose -TotalCount 18

$items | Should -Not -Be $null
$items.Count | Should -BeGreaterThan 2
$createdEvents = $items | where-object {$_.EventId -eq 'ScriptBlock_Compile_Detail:ExecuteCommand.Create.Verbose'}
$createdEvents.Count | should -BeGreaterOrEqual 3

# Verify we log that we are executing a file
$createdEvents[0].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f ".*/$testFileName")

# Verify we log that we are the script to create the scriptblock
$createdEvents[1].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f (Get-RegEx -SimpleMatch $Script.Replace([System.Environment]::NewLine,'#012')))

# Verify we log that we are excuting the created scriptblock
$createdEvents[2].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f "Write\-Verbose 'testheader123␀' ;Write\-verbose 'after'")
}

It 'Verifies logging level filtering works' -Skip:(!$IsSupportedEnvironment) {
$configFile = WriteLogSettings -LogId $logId -LogLevel Warning
& $powershell -NoProfile -SettingsFile $configFile -Command '$env:PSModulePath | out-null'
Expand Down Expand Up @@ -342,6 +371,44 @@ $pid
}
}

It 'Verifies scriptblock logging with null character' -Skip:(!$IsSupportedEnvironment) {
try {
$script = @'
$pid
& ([scriptblock]::create("Write-Verbose 'testheader123$([char]0x0000)' ;Write-verbose 'after'"))
'@
$configFile = WriteLogSettings -ScriptBlockLogging -LogId $logId -LogLevel Verbose
$testFileName = 'test01.ps1'
$testScriptPath = Join-Path -Path $TestDrive -ChildPath $testFileName
$script | Out-File -FilePath $testScriptPath -Force
$testPid = & $powershell -NoProfile -SettingsFile $configFile -Command $testScriptPath

Export-PSOsLog -After $after -LogPid $testPid -TimeoutInMilliseconds 30000 -IntervalInMilliseconds 3000 -MinimumCount 18 |
Set-Content -Path $contentFile
$items = @(Get-PSOsLog -Path $contentFile -Id $logId -After $after -Verbose)

$items | Should -Not -Be $null
$items.Count | Should -BeGreaterThan 2
$createdEvents = $items | where-object {$_.EventId -eq 'ScriptBlock_Compile_Detail:ExecuteCommand.Create.Verbose'}
$createdEvents.Count | should -BeGreaterOrEqual 3

# Verify we log that we are executing a file
$createdEvents[0].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f ".*/$testFileName")

# Verify we log that we are the script to create the scriptblock
$createdEvents[1].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f (Get-RegEx -SimpleMatch $Script))

# Verify we log that we are excuting the created scriptblock
$createdEvents[2].Message | Should -Match ($scriptBlockCreatedRegExTemplate -f "Write\-Verbose 'testheader123␀' ;Write\-verbose 'after'")
}
catch {
if (Test-Path $contentFile) {
Send-VstsLogFile -Path $contentFile
}
throw
}
}

# This is pending because it results in false postitives (-Skip:(!$IsSupportedEnvironment) )
It 'Verifies logging level filtering works' -Pending {
try {
Expand Down Expand Up @@ -374,6 +441,11 @@ Describe 'Basic EventLog tests on Windows' -Tag @('CI','RequireAdminOnWindows')
script = "Write-Verbose 'testheader123' ;Write-verbose 'after'"
expectedText="Write-Verbose 'testheader123' ;Write-verbose 'after'`r`n"
}
@{
name = 'script block with Null'
script = "Write-Verbose 'testheader123$([char]0x0000)' ;Write-verbose 'after'"
expectedText="Write-Verbose 'testheader123␀' ;Write-verbose 'after'`r`n"
}
)

if ($IsSupportedEnvironment)
Expand Down