Visual FoxPro
Azure Key Vault Sign with a Certificate's Private Key

Signs a hash using the private key of a certificate previously imported to an Azure Key Vault.
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Visual FoxPro
LOCAL lnSuccess
LOCAL loJson
LOCAL loSb
LOCAL lcSignedString
LOCAL lcHash_base64url
LOCAL loJsonBody
LOCAL loHttp
LOCAL lcUrl
LOCAL loResp
LOCAL lnStatusCode
LOCAL loJsonResp
LOCAL loCert
LOCAL loRsa
LOCAL lnValid

lnSuccess = 0

* 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.
loJson = CreateObject('Chilkat.JsonObject')
loJson.UpdateString("client_id","APP_ID")
loJson.UpdateString("client_secret","APP_PASSWORD")
loJson.UpdateString("resource","https://vault.azure.net")
loJson.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"
loSb = CreateObject('Chilkat.StringBuilder')
lcSignedString = "This is a test"
loSb.Append(lcSignedString)
lcHash_base64url = loSb.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..

loJsonBody = CreateObject('Chilkat.JsonObject')
loJsonBody.UpdateString("alg","RS256")
loJsonBody.UpdateString("value",lcHash_base64url)

loHttp = 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.
loHttp.AuthToken = loJson.Emit()

loHttp.SetUrlVar("certName","importCert01")
loHttp.SetUrlVar("certVersion","7140c8755ed14839b5d86a9f7e7f0497")
* Note: Replace "VAULT_NAME" with the name of your Azure key vault.
lcUrl = "https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4"
loResp = CreateObject('Chilkat.HttpResponse')
lnSuccess = loHttp.HttpJson("POST",lcUrl,loJsonBody,"application/json",loResp)
IF (lnSuccess = 0) THEN
    ? loHttp.LastErrorText
    RELEASE loJson
    RELEASE loSb
    RELEASE loJsonBody
    RELEASE loHttp
    RELEASE loResp
    CANCEL
ENDIF

lnStatusCode = loResp.StatusCode

loJsonResp = CreateObject('Chilkat.JsonObject')
loResp.GetBodyJson(loJsonResp)

loJsonResp.EmitCompact = 0
? loJsonResp.Emit()

IF (lnStatusCode <> 200) THEN
    ? "Failed."
    RELEASE loJson
    RELEASE loSb
    RELEASE loJsonBody
    RELEASE loHttp
    RELEASE loResp
    RELEASE loJsonResp
    CANCEL
ENDIF

* 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.
* 
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadFromFile("qa_data/certs/chilkat_code_signing_2024.cer")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loJson
    RELEASE loSb
    RELEASE loJsonBody
    RELEASE loHttp
    RELEASE loResp
    RELEASE loJsonResp
    RELEASE loCert
    CANCEL
ENDIF

loRsa = CreateObject('Chilkat.Rsa')
* Tell the RSA object to use the cert's public key.
lnSuccess = loRsa.SetX509Cert(loCert,0)
IF (lnSuccess = 0) THEN
    ? loRsa.LastErrorText
    RELEASE loJson
    RELEASE loSb
    RELEASE loJsonBody
    RELEASE loHttp
    RELEASE loResp
    RELEASE loJsonResp
    RELEASE loCert
    RELEASE loRsa
    CANCEL
ENDIF

* Verify the signature using the cert's public key against the original string.
loRsa.EncodingMode = "base64url"
lnValid = loRsa.VerifyStringENC(lcSignedString,"sha-256",loJsonResp.StringOf("value"))
? "signature valid = " + STR(lnValid)

RELEASE loJson
RELEASE loSb
RELEASE loJsonBody
RELEASE loHttp
RELEASE loResp
RELEASE loJsonResp
RELEASE loCert
RELEASE loRsa