(Classic ASP) Azure Key Vault Sign with a Certificate's Private Key

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Signs a hash using the private key of a certificate previously imported to an Azure Key Vault.

Note: This example requires Chilkat v9.5.0.96 or later.

For more information, see https://learn.microsoft.com/en-us/rest/api/keyvault/certificates/import-certificate/import-certificate?tabs=HTTP

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

' See Azure Key Vault Get Certificates for a more detailed explanation
' for how Chilkat is automatically getting the OAuth2 access token for your application.

' Provide information needed for Chilkat to automatically get an OAuth2 access token as needed.
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set json = Server.CreateObject("Chilkat.JsonObject")
success = json.UpdateString("client_id","APP_ID")
success = json.UpdateString("client_secret","APP_PASSWORD")
success = json.UpdateString("resource","https://vault.azure.net")
success = json.UpdateString("token_endpoint","https://login.microsoftonline.com/TENANT_ID/oauth2/token")

' In this example, we'll sign the SHA256 hash of the string "This is a test"
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.StringBuilder")
set sb = Server.CreateObject("Chilkat.StringBuilder")
signedString = "This is a test"
success = sb.Append(signedString)
hash_base64url = sb.GetHash("sha256","base64url","utf-8")

' We're going to send a POST to the following URL:
' POST {vaultBaseUrl}/keys/{key-or-cert-name}/{key-or-cert-version}/sign?api-version=7.4

' For example:

' POST https://VAULT_NAME.vault.azure.net/keys/CERT_NAME/CERT_VERSION/sign?api-version=7.4
' 
' {
'   "alg": "RS512",
'   "value": "RUE3Nzg4NTQ4QjQ5RjFFN0U2NzAyQzhDNEMwMkJDOTA1MTYyOTUzNjI5NDhBNzZDQTlFOTM1NDA2M0ZGMjk2Mg"
' }

' The alg can be one of the following
' ES256  ECDSA using P-256 and SHA-256
' ES256K ECDSA using P-256K and SHA-256
' ES384  ECDSA using P-384 and SHA-384
' ES512  ECDSA using P-521 and SHA-512
' PS256  RSASSA-PSS using SHA-256 and MGF1 with SHA-256
' PS384  RSASSA-PSS using SHA-384 and MGF1 with SHA-384
' PS512  RSASSA-PSS using SHA-512 and MGF1 with SHA-512
' RS256  RSASSA-PKCS1-v1_5 using SHA-256
' RS384  RSASSA-PKCS1-v1_5 using SHA-384
' RS512  RSASSA-PKCS1-v1_5 using SHA-512

' The sample POST above uses SHA512.  We'll instead sign a SHA256 hash..

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jsonBody = Server.CreateObject("Chilkat.JsonObject")
success = jsonBody.UpdateString("alg","RS256")
success = jsonBody.UpdateString("value",hash_base64url)

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Http")
set http = Server.CreateObject("Chilkat.Http")

' Instead of providing an actual access token, we give Chilkat the information that allows it to 
' automatically fetch the access token using the OAuth2 client credentials flow.
http.AuthToken = json.Emit()

success = http.SetUrlVar("certName","importCert01")
success = http.SetUrlVar("certVersion","7140c8755ed14839b5d86a9f7e7f0497")
' Note: Replace "VAULT_NAME" with the name of your Azure key vault.
url = "https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4"
' resp is a Chilkat.HttpResponse
Set resp = http.PostJson3(url,"application/json",jsonBody)
If (http.LastMethodSuccess = 0) Then
    ' This means something failed before we got a response.
    Response.Write "<pre>" & Server.HTMLEncode( http.LastErrorText) & "</pre>"
    Response.End
End If

statusCode = resp.StatusCode

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.JsonObject")
set jsonResp = Server.CreateObject("Chilkat.JsonObject")
success = resp.GetBodyJson(jsonResp)

jsonResp.EmitCompact = 0
Response.Write "<pre>" & Server.HTMLEncode( jsonResp.Emit()) & "</pre>"

If (statusCode <> 200) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Failed.") & "</pre>"
    Response.End
End If

' A successful response body contains JSON like this:
' Note: Azure's documentation is not very clear, but base64url is the encoding, not "base64".
' {
'   "kid": "https://kvchilkat.vault.azure.net/keys/importCert01/7140c8755ed14839b5d86a9f7e7f0497",
'   "value": "JzWd2YF21gjtW ... Em37hKOQ"
' }

' Let's validate the signature using the cert's public key.
' This example will load the corresponding certificate from a local file and will verify the signature against the original data.
' 
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Cert")
set cert = Server.CreateObject("Chilkat.Cert")
success = cert.LoadFromFile("qa_data/certs/chilkat_code_signing_2024.cer")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( cert.LastErrorText) & "</pre>"
    Response.End
End If

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Rsa")
set rsa = Server.CreateObject("Chilkat.Rsa")
' Tell the RSA object to use the cert's public key.
success = rsa.SetX509Cert(cert,0)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( rsa.LastErrorText) & "</pre>"
    Response.End
End If

' Verify the signature using the cert's public key against the original string.
rsa.EncodingMode = "base64url"
valid = rsa.VerifyStringENC(signedString,"sha-256",jsonResp.StringOf("value"))
Response.Write "<pre>" & Server.HTMLEncode( "signature valid = " & valid) & "</pre>"

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