T1553.003: SIP and Trust Provider Hijacking
| View on MITRE ATT&CK | T1553.003 |
|---|---|
| Tactic(s) | Defense Evasion |
Data from MITRE ATT&CK®:
Adversaries may tamper with SIP and trust provider components to mislead the operating system and application control tools when conducting signature validation checks. In user mode, Windows Authenticode (Citation: Microsoft Authenticode) digital signatures are used to verify a file's origin and integrity, variables that may be used to establish trust in signed code (ex: a driver with a valid Microsoft signature may be handled as safe). The signature validation process is handled via the WinVerifyTrust application programming interface (API) function, (Citation: Microsoft WinVerifyTrust) which accepts an inquiry and coordinates with the appropriate trust provider, which is responsible for validating parameters of a signature. (Citation: SpectorOps Subverting Trust Sept 2017)
Because of the varying executable file types and corresponding signature formats, Microsoft created software components called Subject Interface Packages (SIPs) (Citation: EduardosBlog SIPs July 2008) to provide a layer of abstraction between API functions and files. SIPs are responsible for enabling API functions to create, retrieve, calculate, and verify signatures. Unique SIPs exist for most file formats (Executable, PowerShell, Installer, etc., with catalog signing providing a catch-all (Citation: Microsoft Catalog Files and Signatures April 2017)) and are identified by globally unique identifiers (GUIDs). (Citation: SpectorOps Subverting Trust Sept 2017)
Similar to Code Signing, adversaries may abuse this architecture to subvert trust controls and bypass security policies that allow only legitimately signed code to execute on a system. Adversaries may hijack SIP and trust provider components to mislead operating system and application control tools to classify malicious (or any) code as signed by: (Citation: SpectorOps Subverting Trust Sept 2017)
- Modifying the
DllandFuncNameRegistry values inHKLM\SOFTWARE[\WOW6432Node]Microsoft\Cryptography\OID\EncodingType 0\CryptSIPDllGetSignedDataMsg{SIP_GUID}that point to the dynamic link library (DLL) providing a SIP’s CryptSIPDllGetSignedDataMsg function, which retrieves an encoded digital certificate from a signed file. By pointing to a maliciously-crafted DLL with an exported function that always returns a known good signature value (ex: a Microsoft signature for Portable Executables) rather than the file’s real signature, an adversary can apply an acceptable signature value to all files using that SIP (Citation: GitHub SIP POC Sept 2017) (although a hash mismatch will likely occur, invalidating the signature, since the hash returned by the function will not match the value computed from the file). - Modifying the
DllandFuncNameRegistry values inHKLM\SOFTWARE[WOW6432Node]Microsoft\Cryptography\OID\EncodingType 0\CryptSIPDllVerifyIndirectData{SIP_GUID}that point to the DLL providing a SIP’s CryptSIPDllVerifyIndirectData function, which validates a file’s computed hash against the signed hash value. By pointing to a maliciously-crafted DLL with an exported function that always returns TRUE (indicating that the validation was successful), an adversary can successfully validate any file (with a legitimate signature) using that SIP (Citation: GitHub SIP POC Sept 2017) (with or without hijacking the previously mentioned CryptSIPDllGetSignedDataMsg function). This Registry value could also be redirected to a suitable exported function from an already present DLL, avoiding the requirement to drop and execute a new file on disk. - Modifying the
DLLandFunctionRegistry values inHKLM\SOFTWARE[WOW6432Node]Microsoft\Cryptography\Providers\Trust\FinalPolicy{trust provider GUID}that point to the DLL providing a trust provider’s FinalPolicy function, which is where the decoded and parsed signature is checked and the majority of trust decisions are made. Similar to hijacking SIP’s CryptSIPDllVerifyIndirectData function, this value can be redirected to a suitable exported function from an already present DLL or a maliciously-crafted DLL (though the implementation of a trust provider is complex). - Note: The above hijacks are also possible without modifying the Registry via DLL Search Order Hijacking.
Hijacking SIP or trust provider components can also enable persistent code execution, since these malicious components may be invoked by any application that performs code signing or signature validation. (Citation: SpectorOps Subverting Trust Sept 2017)
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Mitigations for this technique
MITRE ATT&CK Mitigations
Execution Prevention
Block execution of code on a system through application control, and/or script blocking.Restrict File and Directory Permissions
Restrict access by setting directory and file permissions that are not specific to users or privileged accounts.Restrict Registry Permissions
Restrict the ability to modify certain hives or keys in the Windows Registry.How to detect this technique
MITRE ATT&CK Data Components
Windows Registry Key Modification (Windows Registry)
Changes made to a Registry Key and/or Key value (ex: Windows EID 4657 or Sysmon EID 13|14)File Modification (File)
Changes made to a file, or its access permissions and attributes, typically to alter the contents of the targeted file (ex: Windows EID 4670 or Sysmon EID 2)Module Load (Module)
Attaching a module into the memory of a process/program, typically to access shared resources/features provided by the module (ex: Sysmon EID 7)Control Validation Tests for this Technique
Use Atomic Red Team tests to test your defenses against this technique.
Sigma Detections for this Technique
SP800-53 Controls
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