T1548.001: Setuid and Setgid
| View on MITRE ATT&CK | T1548.001 |
|---|---|
| Tactic(s) | Defense Evasion, Privilege Escalation |
Data from MITRE ATT&CK®:
An adversary may abuse configurations where an application has the setuid or setgid bits set in order to get code running in a different (and possibly more privileged) user’s context. On Linux or macOS, when the setuid or setgid bits are set for an application binary, the application will run with the privileges of the owning user or group respectively.(Citation: setuid man page) Normally an application is run in the current user’s context, regardless of which user or group owns the application. However, there are instances where programs need to be executed in an elevated context to function properly, but the user running them may not have the specific required privileges.
Instead of creating an entry in the sudoers file, which must be done by root, any user can specify the setuid or setgid flag to be set for their own applications (i.e. Linux and Mac File and Directory Permissions Modification). The chmod command can set these bits with bitmasking, chmod 4777 [file] or via shorthand naming, chmod u+s [file]. This will enable the setuid bit. To enable the setgid bit, chmod 2775 and chmod g+s can be used.
Adversaries can use this mechanism on their own malware to make sure they're able to execute in elevated contexts in the future.(Citation: OSX Keydnap malware) This abuse is often part of a "shell escape" or other actions to bypass an execution environment with restricted permissions.
Alternatively, adversaries may choose to find and target vulnerable binaries with the setuid or setgid bits already enabled (i.e. File and Directory Discovery). The setuid and setguid bits are indicated with an "s" instead of an "x" when viewing a file's attributes via ls -l. The find command can also be used to search for such files. For example, find / -perm +4000 2>/dev/null can be used to find files with setuid set and find / -perm +2000 2>/dev/null may be used for setgid. Binaries that have these bits set may then be abused by adversaries.(Citation: GTFOBins Suid)
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Mitigations for this technique
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MITRE ATT&CK Data Components
File Metadata (File)
Contextual data about a file, which may include information such as name, the content (ex: signature, headers, or data/media), user/owner, permissions, etc.Command Execution (Command)
The execution of a line of text, potentially with arguments, created from program code (e.g. a cmdlet executed via powershell.exe, interactive commands like >dir, shell executions, etc. )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)Control Validation Tests for this Technique
Use Atomic Red Team tests to test your defenses against this technique.
Provide the SetUID capability to a file
Make and modify capabilities of a binary
Do reconnaissance for files that have the setgid bit set
Make and modify binary from C source
Set a SetUID flag on file
Set a SetGID flag on file
Set a SetUID flag on file (freebsd)
Do reconnaissance for files that have the setuid bit set
Make and modify binary from C source (freebsd)
Set a SetGID flag on file (freebsd)
Sigma Detections for this Technique
SP800-53 Controls
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