(Go) 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.

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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.

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

    // ---------------------------------------------------
    // Use the following RSA key loaded from JWK format.
    sbRsaJwk := chilkat.NewStringBuilder()
    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("}")

    rsaKey := chilkat.NewPublicKey()
    success := rsaKey.LoadFromString(*sbRsaJwk.GetAsString())
    if success != true {
        fmt.Println(rsaKey.LastErrorText())
        sbRsaJwk.DisposeStringBuilder()
        rsaKey.DisposePublicKey()
        return
    }

    // ---------------------------------------------------
    // Use the following ECC public key loaded from JWK format.
    sbEccJwk := chilkat.NewStringBuilder()
    sbEccJwk.Append("{\"kty\":\"EC\",")
    sbEccJwk.Append("\"crv\":\"P-256\",")
    sbEccJwk.Append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",")
    sbEccJwk.Append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"")
    sbEccJwk.Append("}")

    eccKey := chilkat.NewPublicKey()
    success = eccKey.LoadFromString(*sbEccJwk.GetAsString())
    if success != true {
        fmt.Println(eccKey.LastErrorText())
        sbRsaJwk.DisposeStringBuilder()
        rsaKey.DisposePublicKey()
        sbEccJwk.DisposeStringBuilder()
        eccKey.DisposePublicKey()
        return
    }

    // ---------------------------------------------------
    // 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"
    //     }
    //   ]
    // }

    sbJws := chilkat.NewStringBuilder()
    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("}")

    jws := chilkat.NewJws()

    success = jws.LoadJwsSb(sbJws)
    if success != true {
        fmt.Println(jws.LastErrorText())
        sbRsaJwk.DisposeStringBuilder()
        rsaKey.DisposePublicKey()
        sbEccJwk.DisposeStringBuilder()
        eccKey.DisposePublicKey()
        sbJws.DisposeStringBuilder()
        jws.DisposeJws()
        return
    }

    // The payload is easily accessible:
    fmt.Println("Payload: ", *jws.GetPayload("utf-8"))

    // protHeader is a JsonObject
    sbKeyId := chilkat.NewStringBuilder()
    bCaseSensitive := false

    numSignatures := jws.NumSignatures()
    i := 0
    for i < numSignatures {
        protHeader := jws.GetProtectedHeader(i)

        fmt.Println("--------------------------")
        fmt.Println(i, ": ")

        // Get the protected header.
        protHeader.SetEmitCompact(false)
        fmt.Println(*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 {
            jws.SetPublicKey(i,rsaKey)
        }

        if sbKeyId.ContentsEqual("myEcKey",bCaseSensitive) == true {
            jws.SetPublicKey(i,eccKey)
        }

        if sbKeyId.ContentsEqual("myMacKey",bCaseSensitive) == true {
            jws.SetMacKey(i,hmacKey,"base64url")
        }

        // Validate this signature.
        v := jws.Validate(i)
        if v < 0 {
            // Perhaps Chilkat was not unlocked or the trial expired..
            fmt.Println("Validate failed for some other reason.")
            fmt.Println(jws.LastErrorText())
        }
        else {
            if v == 0 {
                fmt.Println("Invalid signature.  The key was incorrect, the JWS was invalid, or both.")
            }
            else {
                fmt.Println("Signature validated.")
            }

        }

        protHeader.DisposeJsonObject()
        i = i + 1
    }

    // 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.

    sbRsaJwk.DisposeStringBuilder()
    rsaKey.DisposePublicKey()
    sbEccJwk.DisposeStringBuilder()
    eccKey.DisposePublicKey()
    sbJws.DisposeStringBuilder()
    jws.DisposeJws()
    sbKeyId.DisposeStringBuilder()