Month: January 2018

PowerShell oneliners to check Spectre/Meltdown mitigations

Microsoft script (https://gallery.technet.microsoft.com/scriptcenter/Speculation-Control-e36f0050) is somewhat inconvenient to use. While being a fully-functional module, it’s sometimes easier to just paste code into PowerShell window to do quick check. Or do a Zabbix check with a oneliner. So I adapted Microsoft script to be more compact.

  • Results (with no additional details as with Microsoft script)
    • -1 unsupported by kernel (not patched or unsupported OS)
    • 0 disabled (go find out why, for example Meltdown is always disabled on AMD)
    • 1 enabled
  • Should work on pretty much any PowerShell, Windows 2003 with WMF2.0 gave proper result (-1)
  • Works without admin privileges (I presume, original worked as well, never checked), needs full language mode
  • They’re almost the same, only differences are variable names (just as they were in IDE when I was writing/testing) and NtQuerySystemInformation parameter
  • Should fit within Zabbix key if you put 256 chars (strings are 466 chars before escaping) in a helper macro.
  • Corners were cut (some explicit casts shortened variables) but there might be more. I don’t fully understand P/Invoke and Win32 variable casting, so there might still be more clutter to remove to reduce size
  • By varying parameters, you can query any data Microsoft Script can query. Just take a look at original script’s source.

Spectre

[IntPtr]$a=[System.Runtime.InteropServices.Marshal]::AllocHGlobal(4);If(!((Add-Type -Me "[DllImport(`"ntdll.dll`")]`npublic static extern int NtQuerySystemInformation(uint systemInformationClass,IntPtr systemInformation,uint systemInformationLength,IntPtr returnLength);" -name a -Pas)::NtQuerySystemInformation(201,$a,4,[IntPtr][System.Runtime.InteropServices.Marshal]::AllocHGlobal(4)))){[System.Runtime.InteropServices.Marshal]::ReadInt32($a) -band 0x01}Else{-1}

Meltdown

[IntPtr]$b=[System.Runtime.InteropServices.Marshal]::AllocHGlobal(4);If(!((Add-Type -Me "[DllImport(`"ntdll.dll`")]`npublic static extern int NtQuerySystemInformation(uint systemInformationClass,IntPtr systemInformation,uint systemInformationLength,IntPtr returnLength);" -name b -Pas)::NtQuerySystemInformation(196,$b,4,[IntPtr][System.Runtime.InteropServices.Marshal]::AllocHGlobal(4)))){[System.Runtime.InteropServices.Marshal]::ReadInt32($b) -band 0x01}Else{-1}

VMware EVC now exposes Spectre mitigation MSRs with latest patches

Edit: speak of the devil… new vCenter and vSphere patches just released: https://www.vmware.com/security/advisories/VMSA-2018-0004.html Headline revised to reflect update.

Edit 2: As this update requires shutting down and starting VMs (full power cycle, simply restart does not work), use this PowerCLI command to find VMs that don’t yet have new features exposed

Get-VM |? {$_.extensiondata.runtime.featurerequirement.key -notcontains 'cpuid.IBRS'  -or $_.extensiondata.runtime.featurerequirement.key -notcontains 'cpuid.IBPB'}

While you can apply VMware patches and BIOS microcode updates, guests will not see any mitigation options if EVC is enabled (as these options were not in original CPU specification). It’s the same for KVM/QEMU CPU masking, however Hyper-V allows exposing new flags (probably because it doesn’t have anything like EVC besides “compatibility” flag).

I haven’t yet tested without EVC but with all things patched up, clients with Broadwell EVC don’t see required MSRs with ESXi 6.5.