(VB.NET) 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.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

' 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 New Chilkat.StringBuilder
sbRsaJwk.Append("{""kty"":""RSA"",")
sbRsaJwk.Append("""n"":""ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx")
sbRsaJwk.Append("HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs")
sbRsaJwk.Append("D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH")
sbRsaJwk.Append("SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV")
sbRsaJwk.Append("MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8")
sbRsaJwk.Append("NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ"",")
sbRsaJwk.Append("""e"":""AQAB""")
sbRsaJwk.Append("}")

Dim rsaKey As New Chilkat.PublicKey
Dim success As Boolean = rsaKey.LoadFromString(sbRsaJwk.GetAsString())
If (success <> True) Then
    Debug.WriteLine(rsaKey.LastErrorText)
    Exit Sub
End If


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

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


' ---------------------------------------------------
' The HMAC key (in base64url format)
Dim hmacKey As String = "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 New Chilkat.StringBuilder
sbJws.Append("{ ")
sbJws.Append("  ""payload"": ""SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu"",")
sbJws.Append("  ""signatures"": [")
sbJws.Append("    { ")
sbJws.Append("      ""protected"": ""eyJhbGciOiJSUzI1NiIsImtpZCI6Im15UnNhS2V5In0"",")
sbJws.Append("      ""signature"": ""IPMQ02niTQDwLzsRZSCaEm9VEyAX_AVe3HWjniNt9kW-a8d6ZVbd2k6jGae8s1yIh0cgxDnXQ6-p6_sBI0cnMO0xpuJANhh2vFtNJl5lisad94-H3mB3lSfafRqxeYp5D8bh39BPv7y3PrUNVMQdKEJp_D5oJ0ROPTIYx3EG8eJQOx1HO0KqhcUo401XR6KSsIyFm5joBLNKTVzxZUTT1RRZZtwTdeZkbGevugIOX_9gHAtARpV6WaFA4Vvjnq8X9wPgqjWNCQRupadhTPz0JAsa-wy5vXQjsFlXAn43mDPpMfna5Ab3F5pS4yDwkbX6nRn7XBxH1SnnNJRFholQZw""")
sbJws.Append("    },")
sbJws.Append("    { ")
sbJws.Append("      ""protected"": ""eyJhbGciOiJFUzI1NiIsImtpZCI6Im15RWNLZXkifQ"",")
sbJws.Append("      ""signature"": ""1OQtaT3pgZmkDxvlfghvxL_8kX16WIen6u1MadEq1pA4qytA0--_EwZDNk00GDPWFpoJtKznibMZzLOg_UhHIw""")
sbJws.Append("    },")
sbJws.Append("    { ")
sbJws.Append("      ""protected"": ""eyJhbGciOiJIUzI1NiIsImtpZCI6Im15TWFjS2V5In0"",")
sbJws.Append("      ""signature"": ""YY8yVjmJJfy7YJOn3uUydG8WCY2PEuCvOLil5Ks5lnw""")
sbJws.Append("    }")
sbJws.Append("  ]")
sbJws.Append("}")

Dim jws As New Chilkat.Jws

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


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

Dim protHeader As Chilkat.JsonObject
Dim sbKeyId As New Chilkat.StringBuilder
Dim bCaseSensitive As Boolean = False

Dim numSignatures As Integer = jws.NumSignatures
Dim i As Integer = 0
While i < numSignatures
    protHeader = jws.GetProtectedHeader(i)

    Debug.WriteLine("--------------------------")
    Debug.WriteLine(i & ": ")

    ' Get the protected header.
    protHeader.EmitCompact = False
    Debug.WriteLine(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()
    sbKeyId.Append(protHeader.StringOf("kid"))

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

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

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


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

    End If



    i = i + 1
End While

' 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.