Bypass SSL certificate validation check when using Invoke-WebRequest or Invoke-RestMethod in Windows PowerShell

SslFix.ps1

if ($PSEdition -eq 'Desktop') {
    class TrustAllCertsPolicy : System.Net.ICertificatePolicy {
        [bool] CheckValidationResult (
            [System.Net.ServicePoint]$srvPoint,
            [System.Security.Cryptography.X509Certificates.X509Certificate]$certificate,
            [System.Net.WebRequest]$request,
            [int]$certificateProblem
        ) {
            return $true
        }
    }

    [System.Net.ServicePointManager]::CertificatePolicy = New-Object -TypeName TrustAllCertsPolicy
}

SslFix_CsharpType.ps1

if ($PSEdition -eq 'Desktop') {
    Add-Type @'
    using System.Net;
    using System.Security.Cryptography.X509Certificates;

    public class TrustAllCertsPolicy : ICertificatePolicy {
        public bool CheckValidationResult(
            ServicePoint srvPoint,
            X509Certificate certificate,
            WebRequest request,
            int certificateProblem
        ) {
            return true;
        }
    }
'@

    [System.Net.ServicePointManager]::CertificatePolicy = New-Object TrustAllCertsPolicy
}

SslFix_DeclaredNamespace.ps1

using namespace System.Net
using namespace System.Security.Cryptography.X509Certificates
using namespace System.Management.Automation

if ($PSEdition -eq 'Desktop') {
    class TrustAllCertsPolicy : ICertificatePolicy {
        [bool] CheckValidationResult (
            [ServicePoint]$srvPoint,
            [X509Certificate]$certificate,
            [WebRequest]$request,
            [int]$certificateProblem
        ) {
            return $true
        }
    }

    [ServicePointManager]::CertificatePolicy = New-Object -TypeName TrustAllCertsPolicy
}

I've seen, and used myself, the C# code to define the TrustAllCertsPolicy class so much over the years, and it only dawned on me today that this could be done using PowerShell code.

Three implementations of the fix are in this gist. The traditional C# method, how I like to do it by defining using namespace at the start of my script, and by using the full class names that can be pasted anywhere you need it.

Note, that this snippet of code is only required in Windows PowerShell. Since PowerShell 6.0.0, you can append the -SkipCertificateCheck switch to both Invoke-RestMethod and Invoke-WebRequest which achieves the same result.