(PowerShell) 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.

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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Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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.
$json = New-Object Chilkat.JsonObject
$json.UpdateString("client_id","APP_ID")
$json.UpdateString("client_secret","APP_PASSWORD")
$json.UpdateString("resource","https://vault.azure.net")
$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"
$sb = New-Object Chilkat.StringBuilder
$signedString = "This is a test"
$sb.Append($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..

$jsonBody = New-Object Chilkat.JsonObject
$jsonBody.UpdateString("alg","RS256")
$jsonBody.UpdateString("value",$hash_base64url)

$http = New-Object 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()

$http.SetUrlVar("certName","importCert01")
$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 = $http.PostJson3($url,"application/json",$jsonBody)
if ($http.LastMethodSuccess -eq $false) {
    # This means something failed before we got a response.
    $($http.LastErrorText)
    exit
}

$statusCode = $resp.StatusCode

$jsonResp = New-Object Chilkat.JsonObject
$resp.GetBodyJson($jsonResp)

$jsonResp.EmitCompact = $false
$($jsonResp.Emit())

if ($statusCode -ne 200) {
    $("Failed.")
    exit
}

# 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.
# 
$cert = New-Object Chilkat.Cert
$success = $cert.LoadFromFile("qa_data/certs/chilkat_code_signing_2024.cer")
if ($success -eq $false) {
    $($cert.LastErrorText)
    exit
}

$rsa = New-Object Chilkat.Rsa
# Tell the RSA object to use the cert's public key.
$success = $rsa.SetX509Cert($cert,$false)
if ($success -eq $false) {
    $($rsa.LastErrorText)
    exit
}

# 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"))
$("signature valid = " + $valid)