Lua Requires Chilkat v11.0.0+

Azure Key Vault Sign with a Certificate's Private Key

See more Azure Key Vault Examples

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

local chilkat = require("chilkat")

-- 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.
local json = chilkat.JsonObject.new()
json:update_string("client_id", "APP_ID")
json:update_string("client_secret", "APP_PASSWORD")
json:update_string("resource", "https://vault.azure.net")
json:update_string("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"
local sb = chilkat.StringBuilder.new()
local signedString = "This is a test"
sb:append(signedString)
local hash_base64url = sb:get_hash("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..

local jsonBody = chilkat.JsonObject.new()
jsonBody:update_string("alg", "RS256")
jsonBody:update_string("value", hash_base64url)

local http = chilkat.Http.new()

-- 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.auth_token = json:emit()

http:set_url_var("certName", "importCert01")
http:set_url_var("certVersion", "7140c8755ed14839b5d86a9f7e7f0497")
-- Note: Replace "VAULT_NAME" with the name of your Azure key vault.
local url = "https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4"
local resp = chilkat.HttpResponse.new()
local success = http:http_json("POST", url, jsonBody, "application/json", resp)
if not success then
    print(http.last_error_text)
    return
end

local statusCode = resp.status_code

local jsonResp = chilkat.JsonObject.new()
resp:get_body_json(jsonResp)

jsonResp.emit_compact = false
print(jsonResp:emit())

if statusCode ~= 200 then
    print("Failed.")
    return
end

-- 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.
--
local cert = chilkat.Cert.new()
success = cert:load_from_file("qa_data/certs/chilkat_code_signing_2024.cer")
if not success then
    print(cert.last_error_text)
    return
end

local rsa = chilkat.Rsa.new()
-- Tell the RSA object to use the cert's public key.
success = rsa:set_x509_cert(cert, false)
if not success then
    print(rsa.last_error_text)
    return
end

-- Verify the signature using the cert's public key against the original string.
rsa.encoding_mode = "base64url"
local valid = rsa:verify_string_enc(signedString, "sha-256", jsonResp:string_of("value"))
print("signature valid = " .. tostring(valid))