Create certificates from OpenID well known configurations meta data by following the 'jwks_uri' and iterate the keys result.

openid-jwks.ps1

Param(
    [Parameter(Mandatory = $True, Position=1)][string]$BaseUrl
)

function Get-Json {
    Param([string]$json, [string]$key)
    ConvertFrom-Json $json | Select-Object -expand $key
}

$configuration = Invoke-WebRequest -ContentType "application/json" -Uri "$BaseUrl/.well-known/openid-configuration"

$jwksUri = Get-Json $configuration.Content "jwks_uri"

$response = Invoke-WebRequest -ContentType "application/json" -Uri $jwksUri

$certificates = @{}

Get-Json $response.Content 'keys' | ForEach-Object { $certificates[$_.kid] = [string]$_.x5c }

$certificates.Keys | ForEach-Object {
    $cert = [System.Security.Cryptography.X509Certificates.X509Certificate2]([System.Convert]::FromBase64String($certificates[$_]))
    $filePath = "${_}.crt"
    Export-Certificate -Cert $cert -FilePath $filePath
    Write-Host "Exported certificate '${cert}' to '${filePath}'" }