functions/Backup-DbaDbCertificate.ps1

function Backup-DbaDbCertificate {
    <#
        .SYNOPSIS
            Exports database certificates from SQL Server using SMO.
 
        .DESCRIPTION
            Exports database certificates from SQL Server using SMO and outputs the .cer and .pvk files.
 
        .PARAMETER SqlInstance
            SQL Server name or SMO object representing the SQL Server to connect to. This can be a collection and receive pipeline input to allow the function to be executed against multiple SQL Server instances.
 
        .PARAMETER SqlCredential
            Login to the target instance using alternative credentials. Windows and SQL Authentication supported. Accepts credential objects (Get-Credential)
 
        .PARAMETER Certificate
            Exports certificate that matches the name(s).
 
        .PARAMETER Database
            Exports the encryptor for specific database(s).
 
        .PARAMETER ExcludeDatabase
            Database(s) to skip when exporting encryptors.
 
        .PARAMETER EncryptionPassword
            A string value that specifies the system path to encrypt the private key.
 
        .PARAMETER DecryptionPassword
            A string value that specifies the system path to decrypt the private key.
 
        .PARAMETER Path
            The path to output the files to. The path is relative to the SQL Server itself. If no path is specified, the default data directory will be used.
 
        .PARAMETER Suffix
            The suffix of the filename of the exported certificate.
 
        .PARAMETER InputObject
            Certificate object
 
        .PARAMETER Confirm
            If this switch is enabled, you will be prompted for confirmation before executing any operations that change state.
 
        .PARAMETER EnableException
            By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message.
            This avoids overwhelming you with "sea of red" exceptions, but is inconvenient because it basically disables advanced scripting.
            Using this switch turns this "nice by default" feature off and enables you to catch exceptions with your own try/catch.
 
        .PARAMETER WhatIf
            If this switch is enabled, no actions are performed but informational messages will be displayed that explain what would happen if the command were to run.
 
        .NOTES
            Author: Jess Pomfret (@jpomfret)
            Tags: Migration, Certificate
 
            Website: https://dbatools.io
            Copyright: (C) Chrissy LeMaire, clemaire@gmail.com
            License: MIT https://opensource.org/licenses/MIT
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1
            Exports all the certificates on the specified SQL Server to the default data path for the instance.
 
        .EXAMPLE
            $cred = Get-Credential sqladmin
            Backup-DbaDbCertificate -SqlInstance Server1 -SqlCredential $cred
 
            Connects using sqladmin credential and exports all the certificates on the specified SQL Server to the default data path for the instance.
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1 -Certificate Certificate1
            Exports only the certificate named Certificate1 on the specified SQL Server to the default data path for the instance.
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1 -Database AdventureWorks
            Exports only the certificates for AdventureWorks on the specified SQL Server to the default data path for the instance.
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1 -ExcludeDatabase AdventureWorks
            Exports all certificates except those for AdventureWorks on the specified SQL Server to the default data path for the instance.
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1 -Path \\Server1\Certificates -EncryptionPassword (ConvertTo-SecureString -force -AsPlainText GoodPass1234!!)
            Exports all the certificates and private keys on the specified SQL Server.
 
        .EXAMPLE
            $EncryptionPassword = ConvertTo-SecureString -AsPlainText "GoodPass1234!!" -force
            $DecryptionPassword = ConvertTo-SecureString -AsPlainText "Password4567!!" -force
            Backup-DbaDbCertificate -SqlInstance Server1 -EncryptionPassword $EncryptionPassword -DecryptionPassword $DecryptionPassword
            Exports all the certificates on the specified SQL Server using the supplied DecryptionPassword, since an EncryptionPassword is specified private keys are also exported.
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1 -Path \\Server1\Certificates
            Exports all certificates on the specified SQL Server to the specified path.
 
        .EXAMPLE
            Backup-DbaDbCertificate -SqlInstance Server1 -Suffix DbaTools
            Exports all certificates on the specified SQL Server to the specified path, appends DbaTools to the end of the filenames.
 
        .EXAMPLE
            Get-DbaDbCertificate -SqlInstance sql2016 | Backup-DbaDbCertificate
            Exports all certificates found on sql2016 to the default data directory.
    #>

    [CmdletBinding(DefaultParameterSetName = "Default", SupportsShouldProcess = $true)]
    param (
        [parameter(Mandatory, ParameterSetName = "instance")]
        [Alias("ServerInstance", "SqlServer")]
        [DbaInstanceParameter[]]$SqlInstance,
        [PSCredential]$SqlCredential,
        [parameter(ParameterSetName = "instance")]
        [object[]]$Certificate,
        [parameter(ParameterSetName = "instance")]
        [object[]]$Database,
        [parameter(ParameterSetName = "instance")]
        [object[]]$ExcludeDatabase,
        [parameter(Mandatory = $false)]
        [Security.SecureString]$EncryptionPassword,
        [parameter(Mandatory = $false)]
        [Security.SecureString]$DecryptionPassword,
        [System.IO.FileInfo]$Path,
        [string]$Suffix = "$(Get-Date -format 'yyyyMMddHHmmssms')",
        [parameter(ValueFromPipeline, ParameterSetName = "collection")]
        [Microsoft.SqlServer.Management.Smo.Certificate[]]$InputObject,
        [Alias('Silent')]
        [switch]$EnableException
    )

    begin {

        if ($EncryptionPassword.Length -eq 0 -and $DecryptionPassword.Length -gt 0) {
            Stop-Function -Message "If you specify an decryption password, you must also specify an encryption password" -Target $DecryptionPassword
        }

        Test-DbaDeprecation -DeprecatedOn "1.0.0" -Alias Backup-DbaDatabaseCertificate

        function export-cert ($cert) {
            $certName = $cert.Name
            $db = $cert.Parent
            $server = $db.Parent
            $instance = $server.Name
            $actualPath = $Path

            if ($null -eq $actualPath) {
                $actualPath = Get-SqlDefaultPaths -SqlInstance $server -filetype Data
            }

            $actualPath = "$actualPath".TrimEnd('\')
            $fullCertName = "$actualPath\$certName$Suffix"
            $exportPathKey = "$fullCertName.pvk"

            if (!(Test-DbaPath -SqlInstance $server -Path $actualPath)) {
                Stop-Function -Message "$SqlInstance cannot access $actualPath" -Target $actualPath
            }

            if ($Pscmdlet.ShouldProcess($instance, "Exporting certificate $certName from $db on $instance to $actualPath")) {
                Write-Message -Level Verbose -Message "Exporting Certificate: $certName to $fullCertName"
                try {

                    $exportPathCert = "$fullCertName.cer"

                    # because the password shouldn't go to memory...
                    if ($EncryptionPassword.Length -gt 0 -and $DecryptionPassword.Length -gt 0) {

                        Write-Message -Level Verbose -Message "Both passwords passed in. Will export both cer and pvk."

                        $cert.export(
                            $exportPathCert,
                            $exportPathKey,
                            [System.Runtime.InteropServices.marshal]::PtrToStringAuto([System.Runtime.InteropServices.marshal]::SecureStringToBSTR($EncryptionPassword)),
                            [System.Runtime.InteropServices.marshal]::PtrToStringAuto([System.Runtime.InteropServices.marshal]::SecureStringToBSTR($DecryptionPassword))
                        )
                    }
                    elseif ($EncryptionPassword.Length -gt 0 -and $DecryptionPassword.Length -eq 0) {
                        Write-Message -Level Verbose -Message "Only encryption password passed in. Will export both cer and pvk."

                        $cert.export(
                            $exportPathCert,
                            $exportPathKey,
                            [System.Runtime.InteropServices.marshal]::PtrToStringAuto([System.Runtime.InteropServices.marshal]::SecureStringToBSTR($EncryptionPassword))
                        )
                    }
                    else {
                        Write-Message -Level Verbose -Message "No passwords passed in. Will export just cer."
                        $exportPathKey = "Password required to export key"
                        $cert.export($exportPathCert)
                    }

                    [pscustomobject]@{
                        ComputerName   = $server.ComputerName
                        InstanceName   = $server.ServiceName
                        SqlInstance    = $server.DomainInstanceName
                        Database       = $db.Name
                        Certificate    = $certName
                        Path           = $exportPathCert
                        Key            = $exportPathKey
                        ExportPath     = $exportPathCert
                        ExportKey      = $exportPathKey
                        exportPathCert = $exportPathCert
                        exportPathKey  = $exportPathKey
                        Status         = "Success"
                    } | Select-DefaultView -ExcludeProperty exportPathCert, exportPathKey, ExportPath, ExportKey
                }
                catch {

                    if ($_.Exception.InnerException) {
                        $exception = $_.Exception.InnerException.ToString() -Split "System.Data.SqlClient.SqlException: "
                        $exception = ($exception[1] -Split "at Microsoft.SqlServer.Management.Common.ConnectionManager")[0]
                    }
                    else {
                        $exception = $_.Exception
                    }
                    [pscustomobject]@{
                        ComputerName   = $server.ComputerName
                        InstanceName   = $server.ServiceName
                        SqlInstance    = $server.DomainInstanceName
                        Database       = $db.Name
                        Certificate    = $certName
                        Path           = $exportPathCert
                        Key            = $exportPathKey
                        ExportPath     = $exportPathCert
                        ExportKey      = $exportPathKey
                        exportPathCert = $exportPathCert
                        exportPathKey  = $exportPathKey
                        Status         = "Failure: $exception"
                    } | Select-DefaultView -ExcludeProperty exportPathCert, exportPathKey, ExportPath, ExportKey
                    Stop-Function -Message "$certName from $db on $instance cannot be exported." -Continue -Target $cert -ErrorRecord $_
                }
            }
        }
    }

    process {
        if (Test-FunctionInterrupt) { return }
        foreach ($instance in $SqlInstance) {
            try {
                Write-Message -Level Verbose -Message "Connecting to $instance"
                $server = Connect-SqlInstance -SqlInstance $instance -SqlCredential $SqlCredential
            }
            catch {
                Stop-Function -Message "Failure" -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue
                return
            }
            $databases = Get-DbaDatabase -SqlInstance $server | Where-Object IsAccessible

            if ($Database) {
                $databases = $databases | Where-Object Name -in $Database
            }
            if ($ExcludeDatabase) {
                $databases = $databases | Where-Object Name -NotIn $ExcludeDatabase
            }
            foreach ($db in $databases.Name) {
                $DBInputObject = Get-DbaDbCertificate -SqlInstance $server -Database $db
                if ($Certificate) {
                    $InputObject += $DBInputObject | Where-Object Name -In $Certificate
                }
                else {
                    $InputObject += $DBInputObject | Where-Object Name -NotLike "##*"
                }
                if (!$InputObject) {
                    Write-Message -Level Output -Message "No certificates found to export in $db."
                    continue
                }
            }

        }

        foreach ($cert in $InputObject) {
            if ($cert.Name.StartsWith("##")) {
                Write-Message -Level Output -Message "Skipping system cert $cert"
            }
            else {
                export-cert $cert
            }
        }
    }
}