Test-ValidSID.ps1

function Test-ValidSID {
    # .SYNOPSIS
    # Tests to see if the supplied, referenced object is a SID
    #
    # .DESCRIPTION
    # Validates whether the referenced object is a security identifier (SID).
    # An object is considered to be a SID if it is or can be converted to type
    # System.Security.Principal.SecurityIdentifier. If an object is a SID, this
    # function returns $true; otherwise, it returns $false.
    #
    # .PARAMETER ReferenceToObject
    # This parameter is required; it is a reference to an object that will be
    # tested to determine if it is a SID.
    #
    # .EXAMPLE
    # $boolResult = Test-ValidSID -ReferenceToObject ([ref]'S-1-5-21-1234567890-1234567890-1234567890-1000')
    #
    # .EXAMPLE
    # $boolResult = Test-ValidSID ([ref]'S-1-5-21-1234567890-1234567890-1234567890-1000')
    #
    # .INPUTS
    # None. You can't pipe objects to Test-ValidSID.
    #
    # .OUTPUTS
    # System.Boolean. Test-ValidSID returns a boolean value indiciating
    # whether the supplied object was a SID. $true means the object was a SID;
    # $false means the supplied object was not a SID.
    #
    # .NOTES
    # This function also supports the use of a positional parameter instead of a
    # named parameter. If a positional parameter is used intead of a named
    # parameter, then one positional parameters is required: it is a reference to
    # an object that will be tested to determine if it is a SID.
    #
    # Version: 3.0.20241223.0

    #region License ############################################################
    # Copyright (c) 2024 Frank Lesniak
    #
    # Permission is hereby granted, free of charge, to any person obtaining a copy
    # of this software and associated documentation files (the "Software"), to deal
    # in the Software without restriction, including without limitation the rights
    # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    # copies of the Software, and to permit persons to whom the Software is
    # furnished to do so, subject to the following conditions:
    #
    # The above copyright notice and this permission notice shall be included in
    # all copies or substantial portions of the Software.
    #
    # 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.
    #endregion License ############################################################

    #region Acknowledgements ###################################################
    # Thanks to Friedrich Weinmann who suggested an alternative way to test for a
    # SID:
    # https://twitter.com/FredWeinmann/status/1675513443615404032?s=20
    # retrieved on 2023-07-19
    #endregion Acknowledgements ###################################################

    param (
        [ref]$ReferenceToObject = ([ref]$null)
    )

    #region FunctionsToSupportErrorHandling ####################################
    function Get-ReferenceToLastError {
        # .SYNOPSIS
        # Gets a reference (memory pointer) to the last error that occurred.
        #
        # .DESCRIPTION
        # Returns a reference (memory pointer) to $null ([ref]$null) if no
        # errors on on the $error stack; otherwise, returns a reference to the
        # last error that occurred.
        #
        # .EXAMPLE
        # # Intentionally empty trap statement to prevent terminating errors
        # # from halting processing
        # trap { }
        #
        # # Retrieve the newest error on the stack prior to doing work:
        # $refLastKnownError = Get-ReferenceToLastError
        #
        # # Store current error preference; we will restore it after we do some
        # # work:
        # $actionPreferenceFormerErrorPreference = $global:ErrorActionPreference
        #
        # # Set ErrorActionPreference to SilentlyContinue; this will suppress
        # # error output. Terminating errors will not output anything, kick to
        # # the empty trap statement and then continue on. Likewise, non-
        # # terminating errors will also not output anything, but they do not
        # # kick to the trap statement; they simply continue on.
        # $global:ErrorActionPreference = [System.Management.Automation.ActionPreference]::SilentlyContinue
        #
        # # Do something that might trigger an error
        # Get-Item -Path 'C:\MayNotExist.txt'
        #
        # # Restore the former error preference
        # $global:ErrorActionPreference = $actionPreferenceFormerErrorPreference
        #
        # # Retrieve the newest error on the error stack
        # $refNewestCurrentError = Get-ReferenceToLastError
        #
        # $boolErrorOccurred = $false
        # if (($null -ne $refLastKnownError.Value) -and ($null -ne $refNewestCurrentError.Value)) {
        #     # Both not $null
        #     if (($refLastKnownError.Value) -ne ($refNewestCurrentError.Value)) {
        #         $boolErrorOccurred = $true
        #     }
        # } else {
        #     # One is $null, or both are $null
        #     # NOTE: $refLastKnownError could be non-null, while
        #     # $refNewestCurrentError could be null if $error was cleared;
        #     # this does not indicate an error.
        #     # So:
        #     # If both are null, no error
        #     # If $refLastKnownError is null and $refNewestCurrentError is
        #     # non-null, error
        #     # If $refLastKnownError is non-null and $refNewestCurrentError is
        #     # null, no error
        #     if (($null -eq $refLastKnownError.Value) -and ($null -ne $refNewestCurrentError.Value)) {
        #         $boolErrorOccurred = $true
        #     }
        # }
        #
        # .INPUTS
        # None. You can't pipe objects to Get-ReferenceToLastError.
        #
        # .OUTPUTS
        # System.Management.Automation.PSReference ([ref]).
        # Get-ReferenceToLastError returns a reference (memory pointer) to the
        # last error that occurred. It returns a reference to $null
        # ([ref]$null) if there are no errors on on the $error stack.
        #
        # .NOTES
        # Version: 2.0.20241223.0

        #region License ####################################################
        # Copyright (c) 2024 Frank Lesniak
        #
        # Permission is hereby granted, free of charge, to any person obtaining
        # a copy of this software and associated documentation files (the
        # "Software"), to deal in the Software without restriction, including
        # without limitation the rights to use, copy, modify, merge, publish,
        # distribute, sublicense, and/or sell copies of the Software, and to
        # permit persons to whom the Software is furnished to do so, subject to
        # the following conditions:
        #
        # The above copyright notice and this permission notice shall be
        # included in all copies or substantial portions of the Software.
        #
        # 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.
        #endregion License ####################################################

        if ($Error.Count -gt 0) {
            return ([ref]($Error[0]))
        } else {
            return ([ref]$null)
        }
    }

    function Test-ErrorOccurred {
        # .SYNOPSIS
        # Checks to see if an error occurred during a time period, i.e., during
        # the execution of a command.
        #
        # .DESCRIPTION
        # Using two references (memory pointers) to errors, this function
        # checks to see if an error occurred based on differences between the
        # two errors.
        #
        # To use this function, you must first retrieve a reference to the last
        # error that occurred prior to the command you are about to run. Then,
        # run the command. After the command completes, retrieve a reference to
        # the last error that occurred. Pass these two references to this
        # function to determine if an error occurred.
        #
        # .PARAMETER ReferenceToEarlierError
        # This parameter is required; it is a reference (memory pointer) to a
        # System.Management.Automation.ErrorRecord that represents the newest
        # error on the stack earlier in time, i.e., prior to running the
        # command for which you wish to determine whether an error occurred.
        #
        # If no error was on the stack at this time, ReferenceToEarlierError
        # must be a reference to $null ([ref]$null).
        #
        # .PARAMETER ReferenceToLaterError
        # This parameter is required; it is a reference (memory pointer) to a
        # System.Management.Automation.ErrorRecord that represents the newest
        # error on the stack later in time, i.e., after to running the command
        # for which you wish to determine whether an error occurred.
        #
        # If no error was on the stack at this time, ReferenceToLaterError
        # must be a reference to $null ([ref]$null).
        #
        # .EXAMPLE
        # # Intentionally empty trap statement to prevent terminating errors
        # # from halting processing
        # trap { }
        #
        # # Retrieve the newest error on the stack prior to doing work
        # if ($Error.Count -gt 0) {
        #     $refLastKnownError = ([ref]($Error[0]))
        # } else {
        #     $refLastKnownError = ([ref]$null)
        # }
        #
        # # Store current error preference; we will restore it after we do some
        # # work:
        # $actionPreferenceFormerErrorPreference = $global:ErrorActionPreference
        #
        # # Set ErrorActionPreference to SilentlyContinue; this will suppress
        # # error output. Terminating errors will not output anything, kick to
        # # the empty trap statement and then continue on. Likewise, non-
        # # terminating errors will also not output anything, but they do not
        # # kick to the trap statement; they simply continue on.
        # $global:ErrorActionPreference = [System.Management.Automation.ActionPreference]::SilentlyContinue
        #
        # # Do something that might trigger an error
        # Get-Item -Path 'C:\MayNotExist.txt'
        #
        # # Restore the former error preference
        # $global:ErrorActionPreference = $actionPreferenceFormerErrorPreference
        #
        # # Retrieve the newest error on the error stack
        # if ($Error.Count -gt 0) {
        #     $refNewestCurrentError = ([ref]($Error[0]))
        # } else {
        #     $refNewestCurrentError = ([ref]$null)
        # }
        #
        # if (Test-ErrorOccurred -ReferenceToEarlierError $refLastKnownError -ReferenceToLaterError $refNewestCurrentError) {
        #     # Error occurred
        # } else {
        #     # No error occurred
        # }
        #
        # .INPUTS
        # None. You can't pipe objects to Test-ErrorOccurred.
        #
        # .OUTPUTS
        # System.Boolean. Test-ErrorOccurred returns a boolean value indicating
        # whether an error occurred during the time period in question. $true
        # indicates an error occurred; $false indicates no error occurred.
        #
        # .NOTES
        # This function also supports the use of positional parameters instead
        # of named parameters. If positional parameters are used intead of
        # named parameters, then two positional parameters are required:
        #
        # The first positional parameter is a reference (memory pointer) to a
        # System.Management.Automation.ErrorRecord that represents the newest
        # error on the stack earlier in time, i.e., prior to running the
        # command for which you wish to determine whether an error occurred. If
        # no error was on the stack at this time, the first positional
        # parameter must be a reference to $null ([ref]$null).
        #
        # The second positional parameter is a reference (memory pointer) to a
        # System.Management.Automation.ErrorRecord that represents the newest
        # error on the stack later in time, i.e., after to running the command
        # for which you wish to determine whether an error occurred. If no
        # error was on the stack at this time, ReferenceToLaterError must be
        # a reference to $null ([ref]$null).
        #
        # Version: 2.0.20241223.0

        #region License ####################################################
        # Copyright (c) 2024 Frank Lesniak
        #
        # Permission is hereby granted, free of charge, to any person obtaining
        # a copy of this software and associated documentation files (the
        # "Software"), to deal in the Software without restriction, including
        # without limitation the rights to use, copy, modify, merge, publish,
        # distribute, sublicense, and/or sell copies of the Software, and to
        # permit persons to whom the Software is furnished to do so, subject to
        # the following conditions:
        #
        # The above copyright notice and this permission notice shall be
        # included in all copies or substantial portions of the Software.
        #
        # 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.
        #endregion License ####################################################
        param (
            [ref]$ReferenceToEarlierError = ([ref]$null),
            [ref]$ReferenceToLaterError = ([ref]$null)
        )

        # TODO: Validate input

        $boolErrorOccurred = $false
        if (($null -ne $ReferenceToEarlierError.Value) -and ($null -ne $ReferenceToLaterError.Value)) {
            # Both not $null
            if (($ReferenceToEarlierError.Value) -ne ($ReferenceToLaterError.Value)) {
                $boolErrorOccurred = $true
            }
        } else {
            # One is $null, or both are $null
            # NOTE: $ReferenceToEarlierError could be non-null, while
            # $ReferenceToLaterError could be null if $error was cleared; this
            # does not indicate an error.
            # So:
            # - If both are null, no error
            # - If $ReferenceToEarlierError is null and $ReferenceToLaterError
            #   is non-null, error
            # - If $ReferenceToEarlierError is non-null and
            #   $ReferenceToLaterError is null, no error
            if (($null -eq $ReferenceToEarlierError.Value) -and ($null -ne $ReferenceToLaterError.Value)) {
                $boolErrorOccurred = $true
            }
        }

        return $boolErrorOccurred
    }
    #endregion FunctionsToSupportErrorHandling ####################################

    trap {
        # Intentionally left empty to prevent terminating errors from halting
        # processing
    }

    # TODO: Validate input

    # Retrieve the newest error on the stack prior to doing work
    $refLastKnownError = Get-ReferenceToLastError

    # Store current error preference; we will restore it after we do the work of
    # this function
    $actionPreferenceFormerErrorPreference = $global:ErrorActionPreference

    # Set ErrorActionPreference to SilentlyContinue; this will suppress error
    # output. Terminating errors will not output anything, kick to the empty trap
    # statement and then continue on. Likewise, non-terminating errors will also
    # not output anything, but they do not kick to the trap statement; they simply
    # continue on.
    $global:ErrorActionPreference = [System.Management.Automation.ActionPreference]::SilentlyContinue

    # This shouldn't error, even if the referenced object is not a SID, but we play
    # it safe and store the result in $objSID. $objSID should be $null if the
    # referenced object is not a SID
    $objSID = ($ReferenceToObject.Value) -as [System.Security.Principal.SecurityIdentifier]

    # Restore the former error preference
    $global:ErrorActionPreference = $actionPreferenceFormerErrorPreference

    # Retrieve the newest error on the error stack
    $refNewestCurrentError = Get-ReferenceToLastError

    if (Test-ErrorOccurred -ReferenceToEarlierError $refLastKnownError -ReferenceToLaterError $refNewestCurrentError) {
        # Error occurred; return indicator that object is not a SID:
        return $false
    } else {
        # No error occurred
        # If $objSID is not $null, then the referenced object was a SID
        # If $objSID is $null, then the referenced object was not a SID
        return ($null -ne $objSID)
    }
}