(Go) 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"
    //      }

    sbPubKey := chilkat.NewStringBuilder()
    sbPubKey.Append("{\"kty\":\"RSA\",")
    sbPubKey.Append("\"n\":\"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx")
    sbPubKey.Append("HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs")
    sbPubKey.Append("D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH")
    sbPubKey.Append("SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV")
    sbPubKey.Append("MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8")
    sbPubKey.Append("NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ\",")
    sbPubKey.Append("\"e\":\"AQAB\"")
    sbPubKey.Append("}")

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

    jws := chilkat.NewJws()

    // Set the RSA public key:
    signatureIndex := 0
    jws.SetPublicKey(signatureIndex,pubKey)

    // Load the JWS.
    sbJws := chilkat.NewStringBuilder()
    sbJws.Append("eyJhbGciOiJSUzI1NiJ9")
    sbJws.Append(".")
    sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
    sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
    sbJws.Append(".")
    sbJws.Append("cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7")
    sbJws.Append("AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4")
    sbJws.Append("BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K")
    sbJws.Append("0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv")
    sbJws.Append("hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB")
    sbJws.Append("p0igcN_IoypGlUPQGe77Rw")

    success = jws.LoadJwsSb(sbJws)
    if success != true {
        fmt.Println(jws.LastErrorText())
        sbPubKey.DisposeStringBuilder()
        pubKey.DisposePublicKey()
        jws.DisposeJws()
        sbJws.DisposeStringBuilder()
        return
    }

    // Validate the 1st (and only) signature at index 0..
    v := jws.Validate(signatureIndex)
    if v < 0 {
        // Perhaps Chilkat was not unlocked or the trial expired..
        fmt.Println("Method call failed for some other reason.")
        fmt.Println(jws.LastErrorText())
        sbPubKey.DisposeStringBuilder()
        pubKey.DisposePublicKey()
        jws.DisposeJws()
        sbJws.DisposeStringBuilder()
        return
    }

    if v == 0 {
        fmt.Println("Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both.")
        sbPubKey.DisposeStringBuilder()
        pubKey.DisposePublicKey()
        jws.DisposeJws()
        sbJws.DisposeStringBuilder()
        return
    }

    // If we get here, the signature was validated..
    fmt.Println("Signature validated.")
    fmt.Println("--")

    // Recover the original content:
    fmt.Println("Recovered content:")
    fmt.Println(*jws.GetPayload("utf-8"))
    fmt.Println("--")

    // Examine the protected header:
    joseHeader := jws.GetProtectedHeader(signatureIndex)
    if jws.LastMethodSuccess() != true {
        fmt.Println("No protected header found at the given index.")
        sbPubKey.DisposeStringBuilder()
        pubKey.DisposePublicKey()
        jws.DisposeJws()
        sbJws.DisposeStringBuilder()
        return
    }

    joseHeader.SetEmitCompact(false)

    fmt.Println("Protected (JOSE) header:")
    fmt.Println(*joseHeader.Emit())
    joseHeader.DisposeJsonObject()

    // Output:

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

    sbPubKey.DisposeStringBuilder()
    pubKey.DisposePublicKey()
    jws.DisposeJws()
    sbJws.DisposeStringBuilder()