(Tcl) 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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load ./chilkat.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.
set json [new_CkJsonObject]

CkJsonObject_UpdateString $json "client_id" "APP_ID"
CkJsonObject_UpdateString $json "client_secret" "APP_PASSWORD"
CkJsonObject_UpdateString $json "resource" "https://vault.azure.net"
CkJsonObject_UpdateString $json "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"
set sb [new_CkStringBuilder]

set signedString "This is a test"
CkStringBuilder_Append $sb $signedString
set hash_base64url [CkStringBuilder_getHash $sb "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..

set jsonBody [new_CkJsonObject]

CkJsonObject_UpdateString $jsonBody "alg" "RS256"
CkJsonObject_UpdateString $jsonBody "value" $hash_base64url

set http [new_CkHttp]

# 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.
CkHttp_put_AuthToken $http [CkJsonObject_emit $json]

CkHttp_SetUrlVar $http "certName" "importCert01"
CkHttp_SetUrlVar $http "certVersion" "7140c8755ed14839b5d86a9f7e7f0497"
# Note: Replace "VAULT_NAME" with the name of your Azure key vault.
set url "https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4"
# resp is a CkHttpResponse
set resp [CkHttp_PostJson3 $http $url "application/json" $jsonBody]
if {[CkHttp_get_LastMethodSuccess $http] == 0} then {
    # This means something failed before we got a response.
    puts [CkHttp_lastErrorText $http]
    delete_CkJsonObject $json
    delete_CkStringBuilder $sb
    delete_CkJsonObject $jsonBody
    delete_CkHttp $http
    exit
}

set statusCode [CkHttpResponse_get_StatusCode $resp]

set jsonResp [new_CkJsonObject]

CkHttpResponse_GetBodyJson $resp $jsonResp
delete_CkHttpResponse $resp

CkJsonObject_put_EmitCompact $jsonResp 0
puts [CkJsonObject_emit $jsonResp]

if {$statusCode != 200} then {
    puts "Failed."
    delete_CkJsonObject $json
    delete_CkStringBuilder $sb
    delete_CkJsonObject $jsonBody
    delete_CkHttp $http
    delete_CkJsonObject $jsonResp
    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.
# 
set cert [new_CkCert]

set success [CkCert_LoadFromFile $cert "qa_data/certs/chilkat_code_signing_2024.cer"]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkJsonObject $json
    delete_CkStringBuilder $sb
    delete_CkJsonObject $jsonBody
    delete_CkHttp $http
    delete_CkJsonObject $jsonResp
    delete_CkCert $cert
    exit
}

set rsa [new_CkRsa]

# Tell the RSA object to use the cert's public key.
set success [CkRsa_SetX509Cert $rsa $cert 0]
if {$success == 0} then {
    puts [CkRsa_lastErrorText $rsa]
    delete_CkJsonObject $json
    delete_CkStringBuilder $sb
    delete_CkJsonObject $jsonBody
    delete_CkHttp $http
    delete_CkJsonObject $jsonResp
    delete_CkCert $cert
    delete_CkRsa $rsa
    exit
}

# Verify the signature using the cert's public key against the original string.
CkRsa_put_EncodingMode $rsa "base64url"
set valid [CkRsa_VerifyStringENC $rsa $signedString "sha-256" [CkJsonObject_stringOf $jsonResp "value"]]
puts "signature valid = $valid"

delete_CkJsonObject $json
delete_CkStringBuilder $sb
delete_CkJsonObject $jsonBody
delete_CkHttp $http
delete_CkJsonObject $jsonResp
delete_CkCert $cert
delete_CkRsa $rsa