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BlueTeam CheatSheet * CVE-2020-0601 * crypt32.dll | Last updated: 2020-01-16 1758 UTC

CVE-2020-0601 AKA ChainOfFools

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

EXPLOIT

  • Publicly available: YES

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

    • 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

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

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

Crowdstrike

Tehtris XDR

Symantec

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

Qualys

Tenable

Zeek / BRO IDS

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)

SIGMA RULE

Sophos

  • [TBD]

ESET

  • [TBD]

Kaspersky

  • [TBD]

Website to check if your device is vulnerable

EMULATE CVE-2020-0601 exploitation attempt

DETECT

Detect the current version of "crypt32.dll"

Detect with PowerShell

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

Check the file signatures and dates

  • Eg: On windows 10, the new DLL is signed with the following timestamp "Friday 3 january 2020 06:14:45"

    • Author's note: The timestamp coul be also the 4th January, depending which Microsoft Edition you're running.
  • Eg: On Windows 10, the new DLL has the following version "10.0.18362.592"

  • Eg: On Windows 10, the new DLL has the following hashes:

    • CRC32: 2B82D538
    • CRC64: 14D5AADB0BD14B22
    • SHA256: E832E3A58B542E15A169B1545CE82451ACE19BD361FD81764383048528F9B540
    • SHA1: 7A9DD389B0E3C124D4BFE5C1FF15F9A93285514F
    • BLAKE2sp: EEE317CD4E1C395DD1DBCA3DCD066728FAE00250D6884EA63B9F6CAD83C14610
  • 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';

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]*"

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

Errors, typos, something to say ?

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