BlueTeam CheatSheet * CVE-2020-0601 * crypt32.dll | Last updated: 2020-01-21 1817 UTC

20200114-TLP-WHITE_CVE-2020-0601.md

CVE-2020-0601 AKA ChainOfFools OR CurveBall

General

• Microsoft disclosed a vulnerability in their monthly Patch Tuesday referenced under CVE-2020-0601.
• The vulnerability was discovered by the U.S. National Security Agency, anounced today (2020-01-14) in their press conference, followed by a blog post and an official security advisory.
• The flaw is located in the "CRYPT32.DLL" file under the C:\Windows\System32\ directory.

Vulnerability explanation

• NSA description:

• NSA has discovered a critical vulnerability (CVE-2020-0601) affecting Microsoft Windows® cryptographic functionality.

• The certificate validation vulnerability allows an attacker to undermine how Windows verifies cryptographic trust and can enable remote code execution.

• The vulnerability affects Windows 10 and Windows Server 2016/2019 as well as applications that rely on Windows for trust functionality. Exploitation of the vulnerability allows attackers to defeat trusted network connections and deliver executable code while appearing as legitimately trusted entities.

• Examples where validation of trust may be impacted include:

  • HTTPS connections
  • Signed files and emails
  • Signed executable code launched as user-mode processes

• The vulnerability places Windows endpoints at risk to a broad range of exploitation vectors.

• NSA assesses the vulnerability to be severe and that sophisticated cyber actors will understand the underlying flaw very quickly and, if exploited, would render the previously mentioned platforms as fundamentally vulnerable.

• The consequences of not patching the vulnerability are severe and widespread. Remote exploitation tools will likely be made quickly and widely available.

• Rapid adoption of the patch is the only known mitigation at this time and should be the primary focus for all network owners.

• If you really want to deep dive in the cryptographic part and understand better the root cause of this vulnerability, Tal Be'ery published today a very didactic explanation:

  • Tal Be'ery Medium BlogPost Part 1
  • Tal Be'ery Medium BlogPost Part 2

EXPLOIT

• Publicly available: YES

  • PoC published the 2020-01-16 1208 AM GMT+1 (PoC1)

    • Interesting nuggets: RSA 2048, use NIST P-384 (secp384r1) curve, 365 days default expire date.
    • 1 Sample uploaded on VTI, seems related to the previous PoC, but no confirmation
      • https://www.virustotal.com/gui/file/95597ed5ed579d4fe1e9a2177c29178038e4f837998bc058c94ede6ec55b7547/details
    • Updated PoC (2020-01-16 1448)
      • Updated include new nuggets: 10000 days default expire date, now abuse CA: "Microsoft ECC Product Root Certificate Authority 2018", still use NIST P-384 (secp384r1) curve, added a mark in the end "Signed by ollypwn"

  • PoC published the 2020-01-16 1214 AM GMT+1 [PoC2]

    • Interesting nuggets: default serial number = 0x5c8b99c55a94c5d27156decd8980cc26, use NIST P-384 (secp384r1) curve, 500 days default expire date, configured to abuse USERTrust ECC Certification Authority, some others hardcoded information but could be changed easily, C = CH, ST = Vaud, L = Lausanne, O = Kudelski Security, CN = 85.184.255.36.

• Privately available: YES (Around 10 private PoC)

• In The Wild Exploitation: YES

REFERENCES

• Microsoft Security Advisory
• NSA Security Advisory
• Microsoft BlogPost
• NSA BlogPost
• CISA-ED20-02
• CISA-Alert-aa20-014a
• CERT-FR_ALERTE
• CERT/CC VU#849224
• NCSC IE
• Research BlogPost

Affected Versions (Exhaustive list)

• Windows 10 for 32-bit Systems
• Windows 10 for x64-based Systems
• Windows 10 Version 1607 for 32-bit Systems
• Windows 10 Version 1607 for x64-based Systems
• Windows 10 Version 1709 for 32-bit Systems
• Windows 10 Version 1709 for ARM64-based Systems
• Windows 10 Version 1709 for x64-based Systems
• Windows 10 Version 1803 for 32-bit Systems
• Windows 10 Version 1803 for ARM64-based Systems
• Windows 10 Version 1803 for x64-based Systems
• Windows 10 Version 1809 for 32-bit Systems
• Windows 10 Version 1809 for ARM64-based Systems
• Windows 10 Version 1809 for x64-based Systems
• Windows 10 Version 1903 for 32-bit Systems
• Windows 10 Version 1903 for ARM64-based Systems
• Windows 10 Version 1903 for x64-based Systems
• Windows 10 Version 1909 for 32-bit Systems
• Windows 10 Version 1909 for ARM64-based Systems
• Windows 10 Version 1909 for x64-based Systems
• Windows Server 2016
• Windows Server 2016 (Server Core installation)
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server, version 1803 (Server Core Installation)
• Windows Server, version 1903 (Server Core installation)
• Windows Server, version 1909 (Server Core installation)

How-To detect that

Vendors detections

Microsoft

Definitions

• Exploit:Win32/CVE-2020-0601.A
• Exploit:Win32/CVE-2020-0601.B
• Exploit:Win32/CVE-2020-0601.D
• Exploit:Win32/CVE-2020-0601.E

Azure Sentinel

• Medium BlogPost

Inside Windows logs

• Matt Graeber gave a us a oneliner command to check quickly in the log if there's any evidence of an event linked to CVE-2020-0601 (Application/EID 1-2)

Get-WinEvent -FilterHashtable @{ LogName = 'Application'; Id = 1; ProviderName = 'Microsoft-Windows-Audit-CVE' } | select -Property * -ExcludeProperty MachineName, UserId

• Source
• Microsoft API documentation

Crowdstrike

• Detection using Windows new API on patched devices
• Reddit CrowStrike Post

CheckPoint

• CheckPoint BlogPost cpai-2020-0019

Tanium

• Tanium BlogPost

Tehtris XDR

• Detection using Windows new API on patched devices
• Tehtris BlogPost

Google Chrome

• Not affected if you're running the following or up version: 79.0.3945.130
• Security update changelog
• Code Commit CVE-2020-0601

TrendMicro

• Deep Security and Vulnerability Protection
  • Rule 1010130 - Microsoft Windows CryptoAPI Spoofing Vulnerability (CVE-2020-0601)
• Apex One Vulnerability Protection (iVP)
  • Rule 1010130 - Microsoft Windows CryptoAPI Spoofing Vulnerability (CVE-2020-0601)
• TippingPoint Filter
  • 36956: HTTP: Microsoft Windows CryptoAPI Spoofing Vulnerability
• Deep Security Log Inspection
  • Rule 1010129 - Microsoft Windows CryptoAPI Spoofing Vulnerability (CVE-2020-0601)
• Deep Discovery Inspector (DDI)
  • Rule 3202 – CVE-2020-0601 Spoofed Certificate Attempt – TLS – Beta
• Trend Micro Microsoft Windows CryptoAPI Spoofing Vulnerability Assessment Tool (SHA256: 11e6b2e96e4e10c00b137aa1c362ac6ac7e65751948bd1f4ef2e34312da8dac0)
• TrendMicro BlogPost
• TrendMicro CurveBall BlogPost
• TrendMicro Security Alert

SOCPrime

• BlogPost

Symantec

• ID Not assigned yet
• ThreatCenter

ZSCALER

• BlogPost Zscaler

SentinelOne

• SentinelOne BlogPost

SNORT

• 1:52593 <-> DISABLED <-> OS-WINDOWS Microsoft Windows CryptoAPI signed binary with spoofed certificate attempt (os-windows.rules)
• 1:52594 <-> DISABLED <-> OS-WINDOWS Microsoft Windows CryptoAPI signed binary with spoofed certificate attempt (os-windows.rules)
• 1:52595 <-> DISABLED <-> OS-WINDOWS Microsoft Windows CryptoAPI signed binary with spoofed certificate attempt (os-windows.rules)
• 1:52596 <-> DISABLED <-> OS-WINDOWS Microsoft Windows CryptoAPI signed binary with spoofed certificate attempt (os-windows.rules)

McAfee

• McAfee KB

Fortinet

• Signature Fortinet 48661
• Fortinet BlogPost

Kaspersky

• Kaspersky security products blocked fake ssl forged certificates, I wasn't able to confirm for the PE or script.
• Kaspersky BlogPost

Paloalto Networks (PAN)

• PAN BlogPost

Qualys

• QID: 91595
• Qualys BlogPost

Tenable

• Plugins ID list
• Tenable BlogPost

Zeek / BRO IDS

• Thanks to 0xxon for the work on Zeek / Bro iDS
• GitHub
• Zeek BlogPost
• Tweet 0xxon

Emerging Threats Pro:

• 2840457 - ETPRO EXPLOIT Possible Spoofed ECDSA Certificate Inbound (CVE-2020-0601) M1 (exploit.rules)
• 2840458 - ETPRO EXPLOIT Possible Spoofed ECDSA Certificate Inbound (CVE-2020-0601) M2 (exploit.rules)

Rapid7 - InsightVM

• BlogPost Rapid7

SIGMA RULE

• Thanks to Florian Roth, there's a sigma rule to detect an exploitation attempst on patched devices.
• GITHUB Sigma Rule
• Tweet Florian Roth

Sophos

• Offcial guidace: Update your system !

ESET

• Seems ESET detecte the exploitation attempts

Website to check if your device is vulnerable

• Website available to check if you're browser is vulnerable to CVE-2020-0601
• Browser Website Check

EMULATE CVE-2020-0601 exploitation attempt

• From Didier Stevens blog, with a bit of VBA, you can test, if your system is patched, to create an emulated event.
• Didier Stevens Blog: Using CveEventWrite From VBA CVE-2020-0601

DETECT

Detect the current version of "crypt32.dll"

Detect with PowerShell

[System.Diagnostics.FileVersionInfo]::GetVersionInfo("C:\Windows\System32\crypt32.dll").FileVersionRaw.ToString()

Check the file signatures and dates

On Windows 10 Clients

• the new DLL is signed with the following timestamp "Friday 3 january 2020 06:14:45"
• Windows 10, the new DLL has the following version "10.0.18362.592"
• Windows 10, the new DLL has the following hashes:
  • CRC32: 2B82D538
  • CRC64: 14D5AADB0BD14B22
  • SHA256: E832E3A58B542E15A169B1545CE82451ACE19BD361FD81764383048528F9B540
  • SHA1: 7A9DD389B0E3C124D4BFE5C1FF15F9A93285514F
  • BLAKE2sp: EEE317CD4E1C395DD1DBCA3DCD066728FAE00250D6884EA63B9F6CAD83C14610

On Windows Server 2016 version 1607

• the new DLL is signed with the following timestamp "Friday 20 december 2019 06:10:17"
• the new DLL has the following version "10.0.14393.3442"
• the new DLL has the following hashes:
  • CRC32: A3F4A8B6
  • CRC64: 190E000CED3B17BB
  • SHA256: 6AE927255B0576AF136DF57210A1BA64C42A504D50867F58B7A128B4FD26A77C
  • SHA1: EF881BAE1A18EC6017DDC9AC5076ED00730C6572
  • BLAKE2sp: 2EAAAE609B2A1D1353CD780BEDF30089C7F0399BC9288E197A04DF2C23FDC767

PowerShell & SCCM are your friends to gain a visibility in your networks

Detect with OSQUERY if your device is patched

• You can detect devices patched with the following oneliner command:

SELECT * FROM patches WHERE HOTFIX_ID='KB4534273';

• Thanks to Kolide Kolide Tweet

Detect with SPLUNK if your device is attacked by CVE-2020-0601

• You can detect in your patched devices any try of exploitation with the following oneliner command:

sourcetype=WinEventLog EventCode=1 LogName=Application Message="*[CVE-2020-0601]*"

• Splunk BlogPost
• Thanks to Richard Davis DAVISRICHARDG Tweet
• Thanks to TomU who explained the necessary configuration for recovering the events in Splunk HF inputs.conf

Parses the ASN.1-encoded ECC curve parameters from an Audit-CVE By Matt Graeber

• Check his github gist Matt Graeber Gist
• Tweets explanations Tweets

Errors, typos, something to say ?

• Feel free to report any mistake directly below in the comment or in DM on Twitter @SwitHak

Is it possible to update only that DLL ? (I don't really want to update my entire system for 1 faulty file)

If yes, on what versions of Windows does it work ? (I have 1903 on x86 system, I can check this one for you.)

@Jm56Z in theory. But it's also best to apply the official hotfixes. Windows update usually allows you to select individual updates you'd like to install.

Is it possible to update only that DLL ? (I don't really want to update my entire system for 1 faulty file)

If yes, on what versions of Windows does it work ? (I have 1903 on x86 system, I can check this one for you.)

Hi,
I advise you to update through Windows Update. I didn't try to just replace the file so I can't tell you.

@Jm56Z in theory. But it's also best to apply the official hotfixes. Windows update usually allows you to select individual updates you'd like to install.

Hi, through the Microsoft Update catalog, select the following KB :"KB4534273"

https://blog.lessonslearned.org/chain-of-fools/

@SwitHak
https://gist.github.com/kitkaat/b74134bc27686884c777bd219f4df4a8/revisions

Can you check the revisions I made and consider adding them to your gist?
It includes a small variance of checking the crypt32.dll version number (where the last digit didn't show up for me with the current command), and the file-hashes and signing date for the server 2016 1607 versions of the file.

Kind regards,

kitkaat

Is it possible to update only that DLL ? (I don't really want to update my entire system for 1 faulty file)
If yes, on what versions of Windows does it work ? (I have 1903 on x86 system, I can check this one for you.)

Hi,
I advise you to update through Windows Update. I didn't try to just replace the file so I can't tell you.

@Jm56Z in theory. But it's also best to apply the official hotfixes. Windows update usually allows you to select individual updates you'd like to install.

Hi, through the Microsoft Update catalog, select the following KB :"KB4534273"

I would also advise against the idea to manually update the crypt32.dll as this is most likely not the only dll which changed in the update. If you visit https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2020-0601 and click on a corresponding KB article link, you can find a link at the bottom of that page for a "file information" csv download for that specific KB, which showcases all the version changes to files and that contains way more libs and files than just crypt32.dll.

Yes, apologies; my in theory was not meant as a recommendation. Please don't do manual security updates; you're asking for problems. Use official means of patching/updating, as others have mentioned.

Emerging Threats has network coverage in:

• 2840457 - ETPRO EXPLOIT Possible Spoofed ECDSA Certificate Inbound (CVE-2020-0601) M1 (exploit.rules)
• 2840458 - ETPRO EXPLOIT Possible Spoofed ECDSA Certificate Inbound (CVE-2020-0601) M2 (exploit.rules)

Emerging Threats has network coverage in:

• 2840457 - ETPRO EXPLOIT Possible Spoofed ECDSA Certificate Inbound (CVE-2020-0601) M1 (exploit.rules)
• 2840458 - ETPRO EXPLOIT Possible Spoofed ECDSA Certificate Inbound (CVE-2020-0601) M2 (exploit.rules)

Hi,
Thanks for the information, updated 👍

@SwitHak
https://gist.github.com/kitkaat/b74134bc27686884c777bd219f4df4a8/revisions

Can you check the revisions I made and consider adding them to your gist?
It includes a small variance of checking the crypt32.dll version number (where the last digit didn't show up for me with the current command), and the file-hashes and signing date for the server 2016 1607 versions of the file.

Kind regards,

kitkaat

Hi,
Can you share a screenshot of the difference between the 2 commands ?
And same for the timestamp date of crypt32.dll for server 2016 1607 version ?
Thanks in advance.

should i be worried if powershell and explorer give me two different versions?

should i be worried if powershell and explorer give me two different versions?

You probably still have the old version loaded in memory, I guess? Did you reboot your computer after installing the update to allow the OS to load the new dll?

You probably still have the old version loaded in memory, I guess? Did you reboot your computer after installing the update to allow the OS to load the new dll?

yupp, just rebooted again. keeps showing different versions.

@SwitHak

Sure, here you go:

Kind regards.

@zined

yupp, just rebooted again. keeps showing different versions.

what version does
[System.Diagnostics.FileVersionInfo]::GetVersionInfo("C:\Windows\System32\crypt32.dll").FileVersionRaw.ToString()
give you ?

what version does
[System.Diagnostics.FileVersionInfo]::GetVersionInfo("C:\Windows\System32\crypt32.dll").FileVersionRaw.ToString()
give you ?

just read your above comment, here you go:

@zined

Thank you kindly for testing it out. That shows the same behaviour I saw on server 2016 1607. I think the most reliable variable to check the current crypt32.dll version is FileVersionRaw instead of FileVersion, as we both experienced that FileVersion could differ with what the GUI displays.
What OS version are you running ?

Thank you kindly for testing it out.

don't thank me, i'm learning some powershell on-the-go ;-) <3

What OS version are you running ?

I would actually guess you have two different versions of crypt32.dll installed and they're reading different versions. It's not unheard of for Windows to copy DLLs all over the place for convenience/un-optimized build/packaging processes.

Would be interested to look at the file handles of each process pulling the versions to see which exact canonical file paths are being loaded into memory when performing the version retrieval, as this might indicate another potential vector if the hotfixes aren't updating all copies of crypt32.dll.

Then again, I'm not a windows expert and I'm not doing any research on this particular vuln, so I might be talking out of my ass. However, the mismatch of versions is very troublesome, especially since it has been reproduced by another individual (for a total of at least 2).

Rapid7 also has an entry in its vuln db: https://www.rapid7.com/db/vulnerabilities/msft-cve-2020-0601

Why the hell it is possible for a server to send a root certificate which is normally available client-side?

Would be interested to look at the file handles of each process pulling the versions to see which exact canonical file paths are being loaded into memory when performing the version retrieval, as this might indicate another potential vector if the hotfixes aren't updating all copies of crypt32.dll.

Then again, I'm not a windows expert and I'm not doing any research on this particular vuln, so I might be talking out of my ass. However, the mismatch of versions is very troublesome, especially since it has been reproduced by another individual (for a total of at least 2).

I tried to trace it with procmon.exe (sysinternals) and it looks to me the commands pull the same file from the same path. So I believe FileVersion is not a reliable parameter to base a test on, but FileVersionRaw.Tostring() is.

ProcMon trace with the .FileVersion command:

ProcMon trace with the .FileVersionRaw.ToString() command:

So, I finally got Windows to download and install the sole fix for this exploit (It really wanted to download some others updates I don't want, I prefer to check if they're stable before doing them).
The update size is 84 GB.
Thanks @kitkaat !

Many thanks @SwitHak and @kitkaat! This Gist helped me greatly with patching today.

@SwitHak

Sure, here you go:

Kind regards.

Hi,
Sorry for the delay.
I chose finally your command, despite i wasn't unable to reproduce your output.
Regards,
SwitHak.

To determine number of devices received and installed the patch and how many still required to do so (only if you deployed the patch already from SCCM ) - you can use the following SQL or create a report in SSRS.
use cm_j01
/
SELECT

• FROM CM_J01.INFORMATION_SCHEMA.TABLES
  WHERE TABLE_TYPE = 'VIEW' and TABLE_NAME like '%quick%'
  select * from v_gs_quick_fix_engineering where HotFixID0 in ('KB4528760',
  'KB4534271',
  'KB4534273',
  'KB4534276',
  'KB4534293',
  'KB4534306',
  'KB4528760')
  */

--
Select [Update],Sum([Installed]) 'Installed' ,sum([Not Installed]) 'Not Installed' from (
Select [update] , count([computer]) 'Installed',0 'Not Installed' from
(
SELECT DISTINCT
SYS.Name0 'Computer',
SYS.Operating_System_Name_and0 'OS',
UIN.Title 'Update',
CASE
WHEN UIN.Title LIKE '%KB4528760%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534271%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534273%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534276%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534293%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534306%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
ELSE 'No'
END 'KB Installed'

FROM v_R_System SYS
left JOIN v_UpdateComplianceStatus UCS ON SYS.ResourceID = UCS.ResourceID
left JOIN v_UpdateInfo UIN ON UCS.CI_ID = UIN.CI_ID

WHERE
(UIN.Title LIKE '%KB4528760%') OR
(UIN.Title LIKE '%KB4534271%') OR
(UIN.Title LIKE '%KB4534273%') OR
(UIN.Title LIKE '%KB4534276%') OR
(UIN.Title LIKE '%KB4534293%') OR
(UIN.Title LIKE '%KB4534306%')

) A
where [KB Installed]='Yes'
group by [update]
-- ORDER BY SYS.Name0
UNION
Select [update] , 0 'Installed' ,count([computer]) 'Not Installed' from
(
SELECT DISTINCT
SYS.Name0 'Computer',
SYS.Operating_System_Name_and0 'OS',
UIN.Title 'Update',
CASE
WHEN UIN.Title LIKE '%KB4528760%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534271%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534273%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534276%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534293%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
WHEN UIN.Title LIKE '%KB4534306%' and (UCS.status=1 or UCS.status=3) THEN 'Yes'
ELSE 'No'
END 'KB Installed'

FROM v_R_System SYS
left JOIN v_UpdateComplianceStatus UCS ON SYS.ResourceID = UCS.ResourceID
left JOIN v_UpdateInfo UIN ON UCS.CI_ID = UIN.CI_ID

WHERE
(UIN.Title LIKE '%KB4528760%') OR
(UIN.Title LIKE '%KB4534271%') OR
(UIN.Title LIKE '%KB4534273%') OR
(UIN.Title LIKE '%KB4534276%') OR
(UIN.Title LIKE '%KB4534293%') OR
(UIN.Title LIKE '%KB4534306%')

) A
where [KB Installed]='No'
group by [update]
) C group by [Update]