MID Server PowerShell files

PowerShell functions are stored in script files (*.ps1) that use a PowerShell Script module (*.psm1) file name extension.

The PowerShell functions are used by the PowerShell MID Server script files included in these activity packs:
  • Active Directory
  • Exchange
  • SCCM
  • PowerShell

PSScript.ps1

This script performs a number of tasks, such as credential testing, password encryption, and the execution of scripts configured in the Orchestration Activity Designer or in MID Script Files. However, this document focuses on how PSScript.ps1 uses the credential.psm1 module for testing access to remote hosts.

The PowerShell variables are generally used directly in the PowerShell execution command or as arguments in the MID Server script file you specify. There are special variables that are passed to PSScript.ps1, such as credType.
Figure 1. Using credType in execution parameters
Using credType in execution parameters

These are the possible credential types:

Table 1. PowerShell credTypes
Type Description
WMI testCredentialWMI
Exchange testCredentilExchange
AD testCredentilAD
SCCM testCredentilSCCM

If no credential type is passed to the PSScrip.ps1 script, the MID Server defaults to the WMI test function to test access to the target host. If there is a credential type used, the MID Server runs the corresponding test function for that credential type.

Exit codes

These exit codes are returned from the PSScript.ps1 script and logged in the MID Server log file.

Table 2. PSScript.ps1 exit codes
Type Test function
0 PowerShell command/script ran successfully.
1 Test finished successfully, but the command/script failed to execute.
2 Incorrect syntax passed to script.
3 All credentials including MID Server service account failed to execute the command/script.
4 Passed test and executed the activity, but an error was returned. Example user cannot be found.

Credentials.psm1

The MID Server uses this module file to test access to a target host. The MID Server loops through all Windows credentials stored in its credentials table using the following access type functions, unless the PowerShell activity has a credential type (credType) defined. All ServiceNow® authored PowerShell activities are hardcoded to use a specific credential type. As a result, the MID Server only tests credential access against the designated function, which is the best practice.
Table 3. PowerShell test functions
Function Description
testCredentialWMI Tests the given user and password on the target host using the Get-WMI object.
testCredentilAD Tests the given user and password on the target host using the built-in DirectoryEntry object.
testCredentialExchange Tests the given user and password to create a session on an Exchange host. This test uses the built-in PowerShell remoting feature on a remote host. WinRM is configured on Exchange servers by default.
testCredentialSCCM Tests the given user and password to create a session on an SCCM server. This test uses the built-in PowerShell remoting feature on a remote host. This requires WinRM to be configured.
testNoCredentialAccessWMI Tests the given user and password on the target host, using the Get-WMI object. This test is used when no credType is used.
Note: If the test passes using one of these functions, that credential is used to run the PowerShell script/command. If the tests fail to access the target host using these functions, the MID Server runs the PowerShell script/command under the account of the MID Server service.

This diagram illustrates the dependency of the credential selection behavior on the host being targeted by the PowerShell activity. If the target host is the IP address or host name of the MID Server, the MID Server bypasses all credentials in the Credentials table and uses the account of the MID Server service. If the target host is not the MID Server, then all Windows credentials are used first. If all credentials in the Credentials table are unsuccessful in running the PowerShell activity, then the MID Server uses the MID Server service account.

Figure 2. PowerShell credential selection criteria
PowerShell credential selection criteria

ActiveDirectory.psm1

This module file stores the functions used by the PowerShell scripts shipped with the Active Directory activity pack.

Exchange.psm1

This module file stores the functions used by the PowerShell scripts shipped with the Exchange activity pack

SCCM.psm1

This module file stores the functions used by the PowerShell scripts shipped with the SCCM activity pack.