(Excel) Ibanity HTTP Signature for XS2A, Isabel Connect, Ponto Connect

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Demonstrates how to add a Signature header for Ibanity HTTP requests.

For more information, see https://documentation.ibanity.com/http-signature

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

' In order to sign your HTTP requests, you have to add 2 headers to the HTTP request: Digest: the digest of the request payload and Signature: the actual signature of the request. 

' POST /xs2a/customer-access-tokens HTTP/1.1
' Host: api.ibanity.com
' Content-Type: application/json
' Digest: SHA-512=z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg/SpIdNs6c5H0NE8XYXysP+DGNKHfuwvY7kxvUdBeoGlODJ6+SfaPg==
' Ibanity-Idempotency-Key: 61f02718-eeee-46e1-b5eb-e8fd6e799c2d
' Signature: keyId="62f02718-eeee-46e1-b5eb-e8fd6e799c2e",created=1599659223,algorithm="hs2019",headers="(request-target) host digest (created) ibanity-idempotency-key",signature="SjWJWbWN7i0...zsbM="
' 
' {"data":{"type":"customerAccessToken", "attributes":{"applicationCustomerReference":"15874569"}}}

' The payload (body) of the above HTTP request is the JSON.
' Build the JSON above.
' Use this online tool to generate code from sample JSON: 
' Generate Code to Create JSON
Dim json As Chilkat.JsonObject
Set json = Chilkat.NewJsonObject
Dim success As Boolean
success = json.UpdateString("data.type","customerAccessToken")
success = json.UpdateString("data.attributes.applicationCustomerReference","15874569")


payload = json.Emit()
Debug.Print "payload = "; payload

' Step 1: Build the (created) virtual header

Dim dtNow As Chilkat.CkDateTime
Set dtNow = Chilkat.NewCkDateTime
success = dtNow.SetFromCurrentSystemTime()

created = dtNow.GetAsUnixTimeStr(False)
Debug.Print "created = "; created

' Step 2: Build the Digest header
Dim crypt As Chilkat.Crypt2
Set crypt = Chilkat.NewCrypt2
crypt.HashAlgorithm = "sha512"
crypt.EncodingMode = "base64"
crypt.Charset = "utf-8"

Dim sbDigestHdrValue As Chilkat.StringBuilder
Set sbDigestHdrValue = Chilkat.NewStringBuilder
success = sbDigestHdrValue.Append("SHA-512=")
success = sbDigestHdrValue.Append(crypt.HashStringENC(json.Emit()))

Debug.Print sbDigestHdrValue.GetAsString()

' Step 3: Build the (request target) virtual header

' In order to build the signature you will need a virtual header named (request-target) (the parentheses are important). 
' The (request-target) is the string concatenation of the HTTP method (in lowercase) with the path and query parameters.

request_target = "post /xs2a/customer-access-tokens"

' Step 4: Build the signing string

' The signing string is the concatenation of the signed header names (in lowercase) and values separated by a LF.

' You must always sign the following headers: (request-target), host, (created), digest. 
' If used, you must also sign the authorization header and any ibanity-* headers, such as ibanity-idempotency-key. 

Dim sbSigningString As Chilkat.StringBuilder
Set sbSigningString = Chilkat.NewStringBuilder
success = sbSigningString.Append("(request-target): ")
success = sbSigningString.AppendLine(request_target,False)
success = sbSigningString.Append("host: ")
success = sbSigningString.AppendLine("api.ibanity.com",False)
success = sbSigningString.Append("digest: ")
success = sbSigningString.AppendLine(sbDigestHdrValue.GetAsString(),False)
success = sbSigningString.Append("(created): ")
success = sbSigningString.AppendLine(created,False)
success = sbSigningString.Append("ibanity-idempotency-key: ")

idempotencyKey = crypt.GenerateUuid()
success = sbSigningString.Append(idempotencyKey)

' Step 5: Build the signed headers list

' To allow Ibanity to check the signed headers, you must provide a list of the header names. They should be lowercase and in the same order used to create the signing string. 

signed_headers_list = "(request-target) host digest (created) ibanity-idempotency-key"

' Step 6: Build the Signature header

' This is where the real signing happens. The signature header is a combination of several sub-headers -
' 
'     keyId: the identifier for the application's signature certificate, obtained from the Developer Portal
'     algorithm: the digital signature algorithm used to generate the signature (must be hs2019)
'     headers: The list of HTTP headers created in step 5
'     signature: the Base64-encoded digital signature of the signing string created in step 4.

Dim privKey As Chilkat.PrivateKey
Set privKey = Chilkat.NewPrivateKey
success = privKey.LoadEncryptedPemFile("my_ibanity_signature_private_key.pem","pem_password")
If (success = False) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

Dim rsa As Chilkat.Rsa
Set rsa = Chilkat.NewRsa
rsa.PssSaltLen = 32
rsa.EncodingMode = "base64"
' Use the RSASSA-PSS signature algorithm
rsa.OaepPadding = True

success = rsa.ImportPrivateKeyObj(privKey)
If (success = False) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Sign the signing string.

sigBase64 = rsa.SignStringENC(sbSigningString.GetAsString(),"sha-256")
If (rsa.LastMethodSuccess = False) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Build the signature header value.
Dim sbSigHeaderValue As Chilkat.StringBuilder
Set sbSigHeaderValue = Chilkat.NewStringBuilder
success = sbSigHeaderValue.Append("keyId=""")
' Use your identifier for the application's signature certificate, obtained from the Developer Portal
success = sbSigHeaderValue.Append("62f02718-eeee-46e1-b5eb-e8fd6e799c2e")
success = sbSigHeaderValue.Append(""",created=")
success = sbSigHeaderValue.Append(created)
success = sbSigHeaderValue.Append(",algorithm=""hs2019"",headers=""")
success = sbSigHeaderValue.Append(signed_headers_list)
success = sbSigHeaderValue.Append(""",signature=""")
success = sbSigHeaderValue.Append(sigBase64)
success = sbSigHeaderValue.Append("""")

Debug.Print sbSigHeaderValue.GetAsString()