(Excel) Validate JWS with Multiple Signatures using the General JSON Serialization Format

Validates and recovers data and headers from a JSON Web Signature (JWS) containing 3 signatures.

Note: Chilkat supports all of the following JWS algorithms:

   +--------------+-------------------------------+--------------------+
   | "alg" Param  | Digital Signature or MAC      | Implementation     |
   | Value        | Algorithm                     | Requirements       |
   +--------------+-------------------------------+--------------------+
   | HS256        | HMAC using SHA-256            | Required           |
   | HS384        | HMAC using SHA-384            | Optional           |
   | HS512        | HMAC using SHA-512            | Optional           |
   | RS256        | RSASSA-PKCS1-v1_5 using       | Recommended        |
   |              | SHA-256                       |                    |
   | RS384        | RSASSA-PKCS1-v1_5 using       | Optional           |
   |              | SHA-384                       |                    |
   | RS512        | RSASSA-PKCS1-v1_5 using       | Optional           |
   |              | SHA-512                       |                    |
   | ES256        | ECDSA using P-256 and SHA-256 | Recommended+       |
   | ES384        | ECDSA using P-384 and SHA-384 | Optional           |
   | ES512        | ECDSA using P-521 and SHA-512 | Optional           |
   | PS256        | RSASSA-PSS using SHA-256 and  | Optional           |
   |              | MGF1 with SHA-256             |                    |
   | PS384        | RSASSA-PSS using SHA-384 and  | Optional           |
   |              | MGF1 with SHA-384             |                    |
   | PS512        | RSASSA-PSS using SHA-512 and  | Optional           |
   |              | MGF1 with SHA-512             |                    |
   +--------------+-------------------------------+--------------------+

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

Download Excel Class Modules Chilkat Excel Class Modules

' 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.

' First, prepare the public keys that will be needed for each signature.

' ---------------------------------------------------
' Use the following RSA key loaded from JWK format.
Dim sbRsaJwk As Chilkat.StringBuilder
Set sbRsaJwk = Chilkat.NewStringBuilder
Dim success As Boolean
success = sbRsaJwk.Append("{""kty"":""RSA"",")
success = sbRsaJwk.Append("""n"":""ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx")
success = sbRsaJwk.Append("HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs")
success = sbRsaJwk.Append("D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH")
success = sbRsaJwk.Append("SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV")
success = sbRsaJwk.Append("MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8")
success = sbRsaJwk.Append("NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ"",")
success = sbRsaJwk.Append("""e"":""AQAB""")
success = sbRsaJwk.Append("}")

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

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

' ---------------------------------------------------
' Use the following ECC public key loaded from JWK format.
Dim sbEccJwk As Chilkat.StringBuilder
Set sbEccJwk = Chilkat.NewStringBuilder
success = sbEccJwk.Append("{""kty"":""EC"",")
success = sbEccJwk.Append("""crv"":""P-256"",")
success = sbEccJwk.Append("""x"":""f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU"",")
success = sbEccJwk.Append("""y"":""x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0""")
success = sbEccJwk.Append("}")

Dim eccKey As Chilkat.PublicKey
Set eccKey = Chilkat.NewPublicKey
success = eccKey.LoadFromString(sbEccJwk.GetAsString())
If (success <> True) Then
    Debug.Print eccKey.LastErrorText
    Exit Sub
End If

' ---------------------------------------------------
' The HMAC key (in base64url format)

hmacKey = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"

' The code below will verify each of the signatures in this JWS:

' { 
'   "payload": "SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu",
'   "signatures": [
'     { 
'       "protected": "eyJhbGciOiJSUzI1NiIsImtpZCI6Im15UnNhS2V5In0",
'       "signature": "IPMQ02niTQDwLzsRZSCaEm9VEyAX_AVe3HWjniNt9kW-a8d6ZVbd2k6jGae8s1yIh0cgxDnXQ6-p6_sBI0cnMO0xpuJANhh2vFtNJl5lisad94-H3mB3lSfafRqxeYp5D8bh39BPv7y3PrUNVMQdKEJp_D5oJ0ROPTIYx3EG8eJQOx1HO0KqhcUo401XR6KSsIyFm5joBLNKTVzxZUTT1RRZZtwTdeZkbGevugIOX_9gHAtARpV6WaFA4Vvjnq8X9wPgqjWNCQRupadhTPz0JAsa-wy5vXQjsFlXAn43mDPpMfna5Ab3F5pS4yDwkbX6nRn7XBxH1SnnNJRFholQZw"
'     },
'     { 
'       "protected": "eyJhbGciOiJFUzI1NiIsImtpZCI6Im15RWNLZXkifQ",
'       "signature": "1OQtaT3pgZmkDxvlfghvxL_8kX16WIen6u1MadEq1pA4qytA0--_EwZDNk00GDPWFpoJtKznibMZzLOg_UhHIw"
'     },
'     { 
'       "protected": "eyJhbGciOiJIUzI1NiIsImtpZCI6Im15TWFjS2V5In0",
'       "signature": "YY8yVjmJJfy7YJOn3uUydG8WCY2PEuCvOLil5Ks5lnw"
'     }
'   ]
' }

Dim sbJws As Chilkat.StringBuilder
Set sbJws = Chilkat.NewStringBuilder
success = sbJws.Append("{ ")
success = sbJws.Append("  ""payload"": ""SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu"",")
success = sbJws.Append("  ""signatures"": [")
success = sbJws.Append("    { ")
success = sbJws.Append("      ""protected"": ""eyJhbGciOiJSUzI1NiIsImtpZCI6Im15UnNhS2V5In0"",")
success = sbJws.Append("      ""signature"": ""IPMQ02niTQDwLzsRZSCaEm9VEyAX_AVe3HWjniNt9kW-a8d6ZVbd2k6jGae8s1yIh0cgxDnXQ6-p6_sBI0cnMO0xpuJANhh2vFtNJl5lisad94-H3mB3lSfafRqxeYp5D8bh39BPv7y3PrUNVMQdKEJp_D5oJ0ROPTIYx3EG8eJQOx1HO0KqhcUo401XR6KSsIyFm5joBLNKTVzxZUTT1RRZZtwTdeZkbGevugIOX_9gHAtARpV6WaFA4Vvjnq8X9wPgqjWNCQRupadhTPz0JAsa-wy5vXQjsFlXAn43mDPpMfna5Ab3F5pS4yDwkbX6nRn7XBxH1SnnNJRFholQZw""")
success = sbJws.Append("    },")
success = sbJws.Append("    { ")
success = sbJws.Append("      ""protected"": ""eyJhbGciOiJFUzI1NiIsImtpZCI6Im15RWNLZXkifQ"",")
success = sbJws.Append("      ""signature"": ""1OQtaT3pgZmkDxvlfghvxL_8kX16WIen6u1MadEq1pA4qytA0--_EwZDNk00GDPWFpoJtKznibMZzLOg_UhHIw""")
success = sbJws.Append("    },")
success = sbJws.Append("    { ")
success = sbJws.Append("      ""protected"": ""eyJhbGciOiJIUzI1NiIsImtpZCI6Im15TWFjS2V5In0"",")
success = sbJws.Append("      ""signature"": ""YY8yVjmJJfy7YJOn3uUydG8WCY2PEuCvOLil5Ks5lnw""")
success = sbJws.Append("    }")
success = sbJws.Append("  ]")
success = sbJws.Append("}")

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

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

' The payload is easily accessible:
Debug.Print "Payload: "; jws.GetPayload("utf-8")

Dim sbKeyId As Chilkat.StringBuilder
Set sbKeyId = Chilkat.NewStringBuilder

bCaseSensitive = False


numSignatures = jws.NumSignatures

i = 0
Do While i < numSignatures
    Set protHeader = jws.GetProtectedHeader(i)

    Debug.Print "--------------------------"
    Debug.Print i; ": "

    ' Get the protected header.
    protHeader.EmitCompact = False
    Debug.Print protHeader.Emit()

    ' Get the key ID ("kid") member.

    ' Note: In this example, the "kid" values are contained in the protected headers.
    ' They could've just as easily been located in unprotected headers.  In that case,
    ' we would've called GetUnprotectedHeader(i) instead of GetProtectedHeader(i).

    sbKeyId.Clear 
    success = sbKeyId.Append(protHeader.StringOf("kid"))

    ' Set the key based on key ID.
    If (sbKeyId.ContentsEqual("myRsaKey",bCaseSensitive) = True) Then
        success = jws.SetPublicKey(i,rsaKey)
    End If

    If (sbKeyId.ContentsEqual("myEcKey",bCaseSensitive) = True) Then
        success = jws.SetPublicKey(i,eccKey)
    End If

    If (sbKeyId.ContentsEqual("myMacKey",bCaseSensitive) = True) Then
        success = jws.SetMacKey(i,hmacKey,"base64url")
    End If

    ' Validate this signature.

    v = jws.Validate(i)
    If (v < 0) Then
        ' Perhaps Chilkat was not unlocked or the trial expired..
        Debug.Print "Validate failed for some other reason."
        Debug.Print jws.LastErrorText
    Else
        If (v = 0) Then
            Debug.Print "Invalid signature.  The key was incorrect, the JWS was invalid, or both."
        Else
            Debug.Print "Signature validated."
        End If

    End If

    i = i + 1
Loop

' The output of this program is:

' 	Payload: In our village, folks say God crumbles up the old moon into stars.
' 	--------------------------
' 	0: 
' 	{
' 	  "alg": "RS256",
' 	  "kid": "myRsaKey"
' 	}
' 
' 	Signature validated.
' 	--------------------------
' 	1: 
' 	{
' 	  "alg": "ES256",
' 	  "kid": "myEcKey"
' 	}
' 
' 	Signature validated.
' 	--------------------------
' 	2: 
' 	{
' 	  "alg": "HS256",
' 	  "kid": "myMacKey"
' 	}
' 
' 	Signature validated.