How to download the SSL certificate from a website using PowerShell?

To share more knowledge :-)

$webRequest = [Net.WebRequest]::Create("https://www.outlook.com")try { $webRequest.GetResponse() } catch {}$cert = $webRequest.ServicePoint.Certificate$bytes = $cert.Export([Security.Cryptography.X509Certificates.X509ContentType]::Cert)set-content -value $bytes -encoding byte -path "$pwd\Outlook.Com.cer"

My co-worker Michael J. Lyons shared this with me.

You should be able to get the public key by using the ServicePoint property on the HttpWebRequest object. This necessary information will be populated once we have made a http request to the site in question.

If the request is made to a site which has an untrusted certificate the GetResponse method will throw an exception, However, the ServicePoint will still contain the Certificate so we want to ensure we ignore WebException if the status is a trust failure.

So something like the following should work:

function Get-PublicKey{    [OutputType([byte[]])]    PARAM (        [Uri]$Uri    )    if (-Not ($uri.Scheme -eq "https"))    {        Write-Error "You can only get keys for https addresses"        return    }    $request = [System.Net.HttpWebRequest]::Create($uri)    try    {        #Make the request but ignore (dispose it) the response, since we only care about the service point        $request.GetResponse().Dispose()    }    catch [System.Net.WebException]    {        if ($_.Exception.Status -eq [System.Net.WebExceptionStatus]::TrustFailure)        {            #We ignore trust failures, since we only want the certificate, and the service point is still populated at this point        }        else        {            #Let other exceptions bubble up, or write-error the exception and return from this method            throw        }    }    #The ServicePoint object should now contain the Certificate for the site.    $servicePoint = $request.ServicePoint    $key = $servicePoint.Certificate.GetPublicKey()    Write-Output $key}Get-PublicKey -Uri "https://www.bing.com"Get-PublicKey -Uri "https://www.facebook.com"

If you want to call the method many times and some might have the same address, you might want to improve the function by using the ServicePointManager.FindServicePoint(System.Uri) method, since it will return a cached version if a request has already been made to that site. So you could check if the service point has been populated with information. If it hasn't, make the web request. If it has, just use the already existing information, saving yourself an http request.

From http://poshcode.org/2521:

function Get-WebsiteCertificate {  [CmdletBinding()]  param (    [Parameter(Mandatory=$true)] [System.Uri]      $Uri,    [Parameter()] [System.IO.FileInfo]      $OutputFile,    [Parameter()] [Switch]      $UseSystemProxy,      [Parameter()] [Switch]      $UseDefaultCredentials,    [Parameter()] [Switch]      $TrustAllCertificates  )  try {    $request = [System.Net.WebRequest]::Create($Uri)    if ($UseSystemProxy) {      $request.Proxy = [System.Net.WebRequest]::DefaultWebProxy    }    if ($UseSystemProxy -and $UseDefaultCredentials) {      $request.Proxy.Credentials = [System.Net.CredentialCache]::DefaultNetworkCredentials    }    if ($TrustAllCertificates) {      # Create a compilation environment      $Provider=New-Object Microsoft.CSharp.CSharpCodeProvider      $Compiler=$Provider.CreateCompiler()      $Params=New-Object System.CodeDom.Compiler.CompilerParameters      $Params.GenerateExecutable=$False      $Params.GenerateInMemory=$True      $Params.IncludeDebugInformation=$False      $Params.ReferencedAssemblies.Add("System.DLL") > $null      $TASource=@'        namespace Local.ToolkitExtensions.Net.CertificatePolicy {          public class TrustAll : System.Net.ICertificatePolicy {            public TrustAll() {             }            public bool CheckValidationResult(System.Net.ServicePoint sp,              System.Security.Cryptography.X509Certificates.X509Certificate cert,               System.Net.WebRequest req, int problem) {              return true;            }          }        }'@       $TAResults=$Provider.CompileAssemblyFromSource($Params,$TASource)      $TAAssembly=$TAResults.CompiledAssembly      ## We now create an instance of the TrustAll and attach it to the ServicePointManager      $TrustAll=$TAAssembly.CreateInstance("Local.ToolkitExtensions.Net.CertificatePolicy.TrustAll")      [System.Net.ServicePointManager]::CertificatePolicy=$TrustAll    }    $response = $request.GetResponse()    $servicePoint = $request.ServicePoint    $certificate = $servicePoint.Certificate    if ($OutputFile) {      $certBytes = $certificate.Export(          [System.Security.Cryptography.X509Certificates.X509ContentType]::Cert        )      [System.IO.File]::WriteAllBytes( $OutputFile, $certBytes )      $OutputFile.Refresh()      return $OutputFile    } else {      return $certificate    }  } catch {    Write-Error "Failed to get website certificate. The error was '$_'."    return $null  }  <#    .SYNOPSIS      Retrieves the certificate used by a website.    .DESCRIPTION      Retrieves the certificate used by a website. Returns either an object or file.    .PARAMETER  Uri      The URL of the website. This should start with https.    .PARAMETER  OutputFile      Specifies what file to save the certificate as.    .PARAMETER  UseSystemProxy      Whether or not to use the system proxy settings.    .PARAMETER  UseDefaultCredentials      Whether or not to use the system logon credentials for the proxy.    .PARAMETER  TrustAllCertificates      Ignore certificate errors for certificates that are expired, have a mismatched common name or are self signed.    .EXAMPLE      PS C:\> Get-WebsiteCertificate "https://www.gmail.com" -UseSystemProxy -UseDefaultCredentials -TrustAllCertificates -OutputFile C:\gmail.cer    .INPUTS      Does not accept pipeline input.    .OUTPUTS      System.Security.Cryptography.X509Certificates.X509Certificate, System.IO.FileInfo  #>}function Import-Certificate {<#    .SYNOPSIS        Imports certificate in specified certificate store.    .DESCRIPTION        Imports certificate in specified certificate store.    .PARAMETER  CertFile        The certificate file to be imported.    .PARAMETER  StoreNames        The certificate store(s) in which the certificate should be imported.    .PARAMETER  LocalMachine        Using the local machine certificate store to import the certificate    .PARAMETER  CurrentUser        Using the current user certificate store to import the certificate    .PARAMETER  CertPassword        The password which may be used to protect the certificate file    .EXAMPLE        PS C:\> Import-Certificate C:\Temp\myCert.cer        Imports certificate file myCert.cer into the current users personal store    .EXAMPLE        PS C:\> Import-Certificate -CertFile C:\Temp\myCert.cer -StoreNames my        Imports certificate file myCert.cer into the current users personal store    .EXAMPLE        PS C:\> Import-Certificate -Cert $certificate -StoreNames my -StoreType LocalMachine        Imports the certificate stored in $certificate into the local machines personal store     .EXAMPLE        PS C:\> Import-Certificate -Cert $certificate -SN my -ST Machine        Imports the certificate stored in $certificate into the local machines personal store using alias names    .EXAMPLE        PS C:\> ls cert:\currentUser\TrustedPublisher | Import-Certificate -ST Machine -SN TrustedPublisher        Copies the certificates found in current users TrustedPublishers store to local machines TrustedPublisher using alias      .INPUTS        System.String|System.Security.Cryptography.X509Certificates.X509Certificate2, System.String, System.String    .OUTPUTS        NA    .NOTES        NAME:      Import-Certificate        AUTHOR:    Patrick Sczepanksi (Original anti121)        VERSION:   20110502        #Requires -Version 2.0    .LINK        http://poshcode.org/2643        http://poshcode.org/1937 (Link to original script)#>    [CmdletBinding()]    param    (        [Parameter(ValueFromPipeline=$true,Mandatory=$true, Position=0, ParameterSetName="CertFile")]        [System.IO.FileInfo]        $CertFile,        [Parameter(ValueFromPipeline=$true,Mandatory=$true, Position=0, ParameterSetName="Cert")]        [System.Security.Cryptography.X509Certificates.X509Certificate2]        $Cert,        [Parameter(Position=1)]        [Alias("SN")]        [string[]] $StoreNames = "My",        [Parameter(Position=2)]        [Alias("Type","ST")]        [ValidateSet("LocalMachine","Machine","CurrentUser","User")]        [string]$StoreType = "CurrentUser",        [Parameter(Position=3)]        [Alias("Password","PW")]        [string] $CertPassword    )    begin    {        [void][System.Reflection.Assembly]::LoadWithPartialName("System.Security")    }    process     {        switch ($pscmdlet.ParameterSetName) {            "CertFile" {                try {                    $Cert = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 $($CertFile.FullName),$CertPassword                }                catch {                       Write-Error ("Error reading '$CertFile': $_ .") -ErrorAction:Continue                }            }            "Cert" {            }            default {                Write-Error "Missing parameter:`nYou need to specify either a certificate or a certificate file name."            }        }        switch -regex ($storeType) {            "Machine$" { $StoreScope = "LocalMachine" }            "User$"  { $StoreScope = "CurrentUser" }        }         if ( $Cert ) {            $StoreNames | ForEach-Object {                $StoreName = $_                Write-Verbose " [Import-Certificate] :: $($Cert.Subject) ($($Cert.Thumbprint))"                Write-Verbose " [Import-Certificate] :: Import into cert:\$StoreScope\$StoreName"                if (Test-Path "cert:\$StoreScope\$StoreName") {                    try                    {                        $store = New-Object System.Security.Cryptography.X509Certificates.X509Store $StoreName, $StoreScope                        $store.Open([System.Security.Cryptography.X509Certificates.OpenFlags]::ReadWrite)                        $store.Add($Cert)                        if ( $CertFile ) {                            Write-Verbose " [Import-Certificate] :: Successfully added '$CertFile' to 'cert:\$StoreScope\$StoreName'."                        } else {                            Write-Verbose " [Import-Certificate] :: Successfully added '$($Cert.Subject) ($($Cert.Thumbprint))' to 'cert:\$StoreScope\$StoreName'."                        }                    }                    catch                    {                        Write-Error ("Error adding '$($Cert.Subject) ($($Cert.Thumbprint))' to 'cert:\$StoreScope\$StoreName': $_ .") -ErrorAction:Continue                    }                    if ( $store ) {                        $store.Close()                    }                }                 else {                    Write-Warning "Certificate store '$StoreName' does not exist. Skipping..."                }            }        } else {            Write-Warning "No certificates found."        }    }    end {         Write-Host "Finished importing certificates."     }}

I successfully used these functions like this:

##Import self-signed certificateGet-WebsiteCertificate $baseUrl local.cer -trust | Out-NullImport-Certificate -certfile local.cer -SN Root  | Out-Null