(Excel) Validate JWS Using RSASSA-PKCS1-v1_5 SHA-256

Validates a JSON Web Signature (JWS) that uses RSASSA-PKCS1-v1_5 SHA-256.

Note: This example requires Chilkat v9.5.0.66 or greater.

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

' Note: This example requires Chilkat v9.5.0.66 or greater.

' This example takes a JSON signature in compact serialization format,
' and uses an RSA public key to validate and recover the protected header and payload.

' We only need a public key for signature validation.  This is the RSA public key
' that is used:

'      {"kty":"RSA", 
'       "n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx
'            HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs
'            D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH
'            SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV
'            MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8
'            NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ", 
'       "e":"AQAB"
'      }

Dim sbPubKey As Chilkat.StringBuilder
Set sbPubKey = Chilkat.NewStringBuilder
Dim success As Boolean
success = sbPubKey.Append("{""kty"":""RSA"",")
success = sbPubKey.Append("""n"":""ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx")
success = sbPubKey.Append("HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs")
success = sbPubKey.Append("D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH")
success = sbPubKey.Append("SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV")
success = sbPubKey.Append("MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8")
success = sbPubKey.Append("NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ"",")
success = sbPubKey.Append("""e"":""AQAB""")
success = sbPubKey.Append("}")

Dim pubKey As Chilkat.PublicKey
Set pubKey = Chilkat.NewPublicKey

success = pubKey.LoadFromString(sbPubKey.GetAsString())
If (success <> True) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Dim jws As Chilkat.Jws
Set jws = Chilkat.NewJws

' Set the RSA public key:

signatureIndex = 0
success = jws.SetPublicKey(signatureIndex,pubKey)

' Load the JWS.
Dim sbJws As Chilkat.StringBuilder
Set sbJws = Chilkat.NewStringBuilder
success = sbJws.Append("eyJhbGciOiJSUzI1NiJ9")
success = sbJws.Append(".")
success = sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
success = sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
success = sbJws.Append(".")
success = sbJws.Append("cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7")
success = sbJws.Append("AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4")
success = sbJws.Append("BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K")
success = sbJws.Append("0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv")
success = sbJws.Append("hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB")
success = sbJws.Append("p0igcN_IoypGlUPQGe77Rw")

success = jws.LoadJwsSb(sbJws)
If (success <> True) Then
    Debug.Print jws.LastErrorText
    Exit Sub
End If

' Validate the 1st (and only) signature at index 0..

v = jws.Validate(signatureIndex)
If (v < 0) Then
    ' Perhaps Chilkat was not unlocked or the trial expired..
    Debug.Print "Method call failed for some other reason."
    Debug.Print jws.LastErrorText
    Exit Sub
End If

If (v = 0) Then
    Debug.Print "Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both."
    Exit Sub
End If

' If we get here, the signature was validated..
Debug.Print "Signature validated."
Debug.Print "--"

' Recover the original content:
Debug.Print "Recovered content:"
Debug.Print jws.GetPayload("utf-8")
Debug.Print "--"

' Examine the protected header:

Set joseHeader = jws.GetProtectedHeader(signatureIndex)
If (jws.LastMethodSuccess <> True) Then
    Debug.Print "No protected header found at the given index."
    Exit Sub
End If

joseHeader.EmitCompact = False

Debug.Print "Protected (JOSE) header:"
Debug.Print joseHeader.Emit()

' Output:

' 	Signature validated.
' 	--
' 	Recovered content:
' 	{"iss":"joe", 
' 	 "exp":1300819380,
' 	 "http://example.com/is_root":true}
' 	--
' 	Protected (JOSE) header:
' 	{ 
' 	  "alg": "RS256"
' 	}