(PowerShell) Validate Certificate using OCSP Protocol

Demonstrates how to validate a certificate (check the revoked status) using the OCSP protocol.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

# Note: Requires Chilkat v9.5.0.75 or greater.

# This requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

# This example will check the revoked status of a certificate loaded from a file.
$cert = New-Object Chilkat.Cert
$success = $cert.LoadFromFile("qa_data/certs/google.crt")
if ($success -ne $true) {
    $($cert.LastErrorText)
    exit
}

# Get the cert's OCSP URL.
$ocspUrl = $cert.OcspUrl

# Build the JSON that will be the OCSP request.

# Possible hash algorithms are sha1, sha256, sha384, sha512.  
$hashAlg = "sha256"
$prng = New-Object Chilkat.Prng
$json = New-Object Chilkat.JsonObject
$json.EmitCompact = $false
# Read more about OCSP nonce lengths
$json.UpdateString("extensions.ocspNonce",$prng.GenRandom(16,"base64"))
$json.I = 0
$json.UpdateString("request[i].cert.hashAlg",$hashAlg)
$json.UpdateString("request[i].cert.issuerNameHash",$cert.HashOf("IssuerDN",$hashAlg,"base64"))
$json.UpdateString("request[i].cert.issuerKeyHash",$cert.HashOf("IssuerPublicKey",$hashAlg,"base64"))
$json.UpdateString("request[i].cert.serialNumber",$cert.SerialNumber)

$($json.Emit())

# Our OCSP request looks something like this:
# {
#   "extensions": {
#     "ocspNonce": "qZDfbpO+nUxRzz6c/SPjE5QCAsPfpkQlRDxTnGl0gnxt7iXO"
#   },
#   "request": [
#     {
#       "cert": {
#         "hashAlg": "sha1",
#         "issuerNameHash": "9u2wY2IygZo19o11oJ0CShGqbK0=",
#         "issuerKeyHash": "d8K4UJpndnaxLcKG0IOgfqZ+uks=",
#         "serialNumber": "6175535D87BF94B6"
#       }
#     }
#   ]
# }

$ocspRequest = New-Object Chilkat.BinData
$http = New-Object Chilkat.Http

# Convert our JSON to a binary (ASN.1) OCSP request
$success = $http.CreateOcspRequest($json,$ocspRequest)
if ($success -eq $false) {
    $($http.LastErrorText)
    exit
}

# Send the OCSP request to the OCSP server
$resp = $http.PBinaryBd("POST",$ocspUrl,$ocspRequest,"application/ocsp-request",$false,$false)
if ($http.LastMethodSuccess -ne $true) {
    $($http.LastErrorText)
    exit
}

# Get the binary (ASN.1) OCSP reply
$ocspReply = New-Object Chilkat.BinData
$resp.GetBodyBd($ocspReply)

# Convert the binary reply to JSON.
# Also returns the overall OCSP response status.
$jsonReply = New-Object Chilkat.JsonObject
$ocspStatus = $http.ParseOcspReply($ocspReply,$jsonReply)

# The ocspStatus can have one of these values:
# -1:  The ARG1 does not contain a valid OCSP reply.
# 0:  Successful - Response has valid confirmations..
# 1: Malformed request - Illegal confirmation request.
# 2: Internal error - Internal error in issuer.
# 3: Try later -  Try again later.
# 4: Not used - This value is never returned.
# 5: Sig required - Must sign the request.
# 6: Unauthorized - Request unauthorized.

if ($ocspStatus -lt 0) {
    $("Invalid OCSP reply.")
    exit
}

$("Overall OCSP Response Status: " + $ocspStatus)

# Let's examine the OCSP response (in JSON).
$jsonReply.EmitCompact = $false
$($jsonReply.Emit())

# The JSON reply looks like this:
# (Use the online tool at https://tools.chilkat.io/jsonParse.cshtml
# to generate JSON parsing code.)

# {
#   "responseStatus": 0,
#   "responseTypeOid": "1.3.6.1.5.5.7.48.1.1",
#   "responseTypeName": "ocspBasic",
#   "response": {
#     "responderIdChoice": "KeyHash",
#     "responderKeyHash": "d8K4UJpndnaxLcKG0IOgfqZ+uks=",
#     "dateTime": "20180803193937Z",
#     "cert": [
#       {
#         "hashOid": "1.3.14.3.2.26",
#         "hashAlg": "SHA-1",
#         "issuerNameHash": "9u2wY2IygZo19o11oJ0CShGqbK0=",
#         "issuerKeyHash": "d8K4UJpndnaxLcKG0IOgfqZ+uks=",
#         "serialNumber": "6175535D87BF94B6",
#         "status": 0,
#         "thisUpdate": "20180803193937Z",
#         "nextUpdate": "20180810193937Z"
#       }
#     ]
#   }
# }
# 

# The certificate status:
$certStatus = -1
if ($jsonReply.HasMember("response.cert[0].status") -eq $true) {
    $certStatus = $jsonReply.IntOf("response.cert[0].status")
}

# Possible certStatus values are:
# -1: No status returned.
# 0: Good
# 1: Revoked
# 2: Unknown.
$("Certificate Status: " + $certStatus)