PowerShell remoting for Discovery
Summarize
Summary of PowerShell remoting for Discovery
The PowerShell remote execution framework in ServiceNow Discovery standardizes and automates the execution of PowerShell scripts on remote target devices. This unified approach eliminates inconsistencies, improves efficiency, and enhances stability when probes collect information from remote Windows systems.
Show less
Requirements
- The MID Server must have read/write access to the network share of the target device.
- Remote targets must have PowerShell version 3 through 5.1 installed.
- For MID Servers using WinRM or WMI that copy scripts to the remote target, the MachinePolicy and UserPolicy execution policy scopes must be set to Undefined.
- If scripts are not copied, the execution policy can be set to any level up to Restrictive.
Application Discovery Considerations
The framework supports copying scripts to the remote target, which is essential for probes like Windows — File discovery. This method helps avoid errors with WMI’s launchProcess when scripts are lengthy and prevents execution failures.
However, copying scripts might trigger antivirus alerts on the target device. To prevent disruptions, customers should whitelist these scripts in their antivirus software.
Probe Configuration
Within probes such as Windows — Active Connections (part of the Windows — ADM multiprobe), configuration options allow controlling script execution:
- Execute script remotely: When enabled, scripts run on the remote target rather than on the MID Server.
- Copy script to target: When enabled alongside remote execution, scripts are copied and executed on the target. If disabled, scripts execute remotely without copying.
PowerShell Probe Development
Probe developers can write PowerShell scripts as if running locally, relying on the remote execution framework to manage remote invocation transparently. This eliminates the need to develop custom remote execution logic, reducing inconsistencies.
The framework supports both WMI and WinRM protocols for remote execution. While WMI uses launchProcess to run commands (which can be complex and prone to failure), WinRM provides a more stable and efficient execution method by avoiding launchProcess.
Probe developers can use the PowerShell remote execution framework to automatically handle remote execution of scripts on target devices. The unified framework removes inconsistencies in remote execution, increases efficiency, and improves stability.
Requirements
- The MID Server must be able to write to and read from the network share of the target.
- The remote target must have PowerShell 3 or higher (up to 5.1).
- For MID Servers using WinRM or WMI which choose to copy the script to the remote target, the MachinePolicy and UserPolicy scopes must be set to Undefined. If the script is not copied, the execution policy can be any other setting up to Restrictive.
See Set up MID Servers to use PowerShell for more information.
Application discovery
The PowerShell remote execution framework has options for copying files to the remote target when executing a scan. Copying files to the target is important for probes like Windows — File discovery because its script invokes itself on the remote target to spawn off a new process. MID Servers using WMI to execute scripts remotely can experience an error with launchProcess if the script is too long. Copying the script to the remote target resolves this error. Copying a script to a remote target may result in anti-virus software on the target flagging the script. To avoid issues with anti-virus software, add the scripts to the permitted list in the anti-virus app.
Probe configuration
The following is the configuration page for the Windows — Active Connections probe, which is included in the Windows — ADM multiprobe.
The Execute script remotely check box is visible when the ECC queue topic is WMIRunner or PowerShell. When checked, the script executes on the remote target. Otherwise the script executes on the MID Server.
The Copy script to target check box is visible when Execute script remotely is checked. If Copy script to target is checked, then the script is copied to, and run on, the target. If Copy script to target is unchecked, then the script is executed on the target without copying it.
PowerShell probe development
PowerShell remote execution framework is a unified method of executing PowerShell scripts, contained in a probe parameter, on a remote target server. The framework removes the need for probe developers to write their own remote execution code, which can cause inconsistencies between developers. The probe developer writes the script as if the probe was collecting information locally because the remote execution framework automatically handles remote script execution.
The framework handles remote execution whether the MID Server is configured to use WMI or WinRM. If the MID Server is configured for WMI, the probe uses launchProcess to execute commands on the remote target. Using launchProcess complicates remote execution and can cause failures. However, a MID Server configured for WinRM does not use launchProcess, and so is more efficient and stable.