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

Question

I want to download the SSL certificate from, say https://www.outlook.com, using PowerShell. Is it possible? Could someone help me?

Solution 1

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.

Solution 2

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.

Solution 3

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 certificate
Get-WebsiteCertificate $baseUrl local.cer -trust | Out-Null
Import-Certificate -certfile local.cer -SN Root  | Out-Null

Comments

[zneak]

Nit: Powershell happily converts strings to enum members, so $cert.Export("Cert") is a valid thing to write.

[Tilo]

how do I get the root cert or chain with that?

[jpaugh]

Hmm. By using the subtype Net.HttpWebRequest instead, we can set $webRequest.Method = "HEAD" to save some bandwidth.

[jpaugh]

@Tilo a certificate is only considered valid if the client already has access to (and trusts) the root certificate. Passing the chain over the wire would be superfluous. However, if you convert the cert to an X509Certificate2, you do get a lot more information. Something like New-Object -TypeName "System.Security.Cryptography.X509Certificates.X509Certifica‌​te2" -ArgumentList $cert should do.

[CircaLucid]

This only displayed the int values of the public key, and Out-File contents were unusable. Answer from @RafaMarrara produces a valid .cert file and is in-line with OP's request of "download the SSL certificate"

[Ross Presser]

I've tried Get-WebsiteCertificate and the object returned only includes Issuer, Subject and a meaningless handle. Is it possible to get the expiry? EDIT: answering myself. if I use -OutFile and then load the file into a X509Certificate2 object, then I get a full suite of information including NotAfter, DnsNameList, etc.

[DAB]

This should be the accepted answer as it's much simpler

[Marc]

There is no -encoding byte in Set-Content. At least not in PowerShell 7.