Replicate Docker credential locally from a Kubernetes secret

locally-replicate-docker-login.ps1

param (
    [switch]
    $Overwrite = $false,

    # If DockerServer is null, script performs the operation on all servers in the registry credential
    [string]
    $DockerServer = $null,

    [string]
    $SecretName = "regcred",

    [string]
    $Namespace = "default",

    # Provide the output of, for example, "kubectl get secret/regcred -o yaml | ConvertFrom-Yaml"
    [Parameter(ValueFromPipeline = $true)]
    [PSObject]
    $SecretContent = $null
)
function ConvertFrom-Base64 {
    [Parameter(ValueFromPipeline = $true)]
    param ($In)
    [System.Text.Encoding]::UTF8.GetString([System.Convert]::FromBase64String($In))
}

if([string]::IsNullOrEmpty($SecretContent)) {
    $secret = kubectl -n $Namespace get secret/$SecretName -o yaml | ConvertFrom-Yaml
} else {
    $secret = $SecretContent
}

$regcred = ConvertFrom-Base64 $secret.data.'.dockerconfigjson' | ConvertFrom-Json

$servers = $regcred.auths | Get-Member -MemberType NoteProperty | Select -ExpandProperty Name
$matched = $false
foreach ($server in $servers) {
    if([string]::IsNullOrEmpty($DockerServer) -or $server -eq $DockerServer) {
        $matched = $true
        if($Overwrite) {
            Write-Host "Log out of ${server}"
            docker logout $server
        }
        Write-Host "Log into ${server}"
        $regcred.auths.$server.password | docker login $server --username $regcred.auths.$server.username --password-stdin
    }
}
if(!$matched) {
    if([string]::IsNullOrEmpty($DockerServer)) {
        Write-Error "No servers are defined in the list of credentials"
    } else {
        Write-Error "Didn't find $DockerServer in the list of servers"
    }
}