Get-TrustedHosts.ps1

#####
### Copyright (c) 2019 Weston Berg
### THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
### IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
### FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
### AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
### LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
### OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
### SOFTWARE.
###
### CMDLET for retrieving the trusted hosts from a machine.
### If the '$Remote' switch is not set then only the trusted
### hosts from the local machine will be retrieved.
###
### Author: Weston Berg
### Date: Aug. 5, 2018
#####

Function Get-TrustedHosts {

    [CmdletBinding(DefaultParameterSetName='RunLocal')]
    param(
        [Parameter(ParameterSetName='RunLocal', Mandatory=$false)][switch]$Local = $false,
        [Parameter(ParameterSetName='RunRemote', Mandatory=$false)][switch]$Remote = $false,
        [Parameter(ParameterSetName='RunRemote', Mandatory=$true,ValueFromPipeline=$true)][string[]]$ComputerName,
        [Parameter(ParameterSetName='RunRemote', Mandatory=$true)][PSCredential]$Credential
    )


    # Pre-Processing
    Begin{}


    # Main processing block.
    # Get the Trusted Hosts via WSMan and 'return' them as output with format 'Computer : TrustedHosts'
    Process{
    
        # Determine if caller only wants local scope or is retrieving from remote computers
        if([string]::Equals($PSCmdlet.ParameterSetName, 'RunLocal')) {
            
            # Only retrieve the trusted hosts for the local computer
            Write-Verbose "Retrieving Trusted Hosts from local machine"

            # Get the Trusted Hosts list from WSMan
            $TrustedHosts = Get-Item WSMan:\localhost\Client\TrustedHosts | Select -ExpandProperty Value
    
            # Format the output
            $Output = "localhost : $TrustedHosts"

            $Output

            # Ignore any computers passed in. Return after one run
            Break

        } else {
            
            # Piping through ForEach loop allows for computers to be passed in via pipline or parameter
            $ComputerName | ForEach-Object {

                # Retrieve Trusted host from specified computer(s) using provided credentials
                Write-Verbose "Retrieving Trusted Hosts from remote machine"

                # Test network connection to the computer 
                Write-Verbose "Checking connection to $_..."

                if(Test-Connection -ComputerName $_ -Count 1 -Quiet) {

                     Write-Verbose "Connection to $_ verified`n"

                    try {
 
                        # Open PowerShell Session
                        Write-Verbose "Creating PowerShell session..."

                        try {

                            $PsSession = New-PSSession -ComputerName $_ -Credential $Credential -ErrorAction Stop 

                        } catch {

                            Write-Host "Error occurred during creation of PowerShell session" -ForegroundColor Red

                            # Throw error to outer catch
                            throw

                        }

                        Write-Verbose "PowerShell session created successfully!`n"

 
                        # Retrieve Trusted Hosts
                        Write-Verbose "Retrieving Trusted Hosts from $_..."

                        try {

                            $RemoteHosts = Invoke-Command -Session $PsSession -ErrorAction Stop -ScriptBlock {
                         
                                    # Get the Trusted Hosts list from WSMan
                                    $TrustedHosts = Get-Item WSMan:\localhost\Client\TrustedHosts | Select -ExpandProperty Value
    
                                    # Format the output
                                    $Output = "$args : $TrustedHosts"

                                    $Output 

                                } -ArgumentList $_

                            $RemoteHosts

                        } catch { 

                            Write-Host "Error while retrieving Trusted Hosts from $_" -ForegroundColor Red

                            # Remove PowerShell session before exiting
                            Remove-PSSession $PsSession

                            # Throw error to outer catch
                            throw

                        }

                        Write-Verbose "Trusted Hosts retrieved successfully`n"


                        # Remove the PowerShell session
                        Write-Verbose "Removing PowerShell session..." 

                        try {

                            Remove-PSSession $PsSession -ErrorAction Stop

                        } catch {

                            Write-Host "Error while removing PowerShell session" -ForegroundColor Red

                            # Throw error to outer catch
                            throw

                        }

                        Write-Verbose "PowerShell session removed`n" 

                    } catch {

                        # Display error
                        Write-Host $Error[0] -ForegroundColor Red

                    }
 

                } else {

                    Write-Verbose "Unable to connect to machine $_"

                    "$_ : Unable To Connect"

                }
            
            }

        }

    } # Process


    # Post-Processing
    End{}


}


# Testing
#Get-TrustedHosts -Verbose

#"localhost", "RemoteMachine" | Get-TrustedHosts -Credential (Get-Credential) -Verbose

#Get-TrustedHosts -Local -Verbose

#Get-TrustedHosts -Remote -ComputerName ("localhost","RemoteMachine") -Credential (Get-Credential) -Verbose