(Go) Validate a JWS Using ECDSA P-256 SHA-256

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 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 ECDSA public key to validate and recover the protected header and payload.

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

    //      {"kty":"EC", 
    //       "crv":"P-256", 
    //       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
    //       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
    //      } 

    sbPubKey := chilkat.NewStringBuilder()
    sbPubKey.Append("{\"kty\":\"EC\",")
    sbPubKey.Append("\"crv\":\"P-256\",")
    sbPubKey.Append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",")
    sbPubKey.Append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"")
    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 ECC public key:
    signatureIndex := 0
    jws.SetPublicKey(signatureIndex,pubKey)

    // Load the JWS.
    sbJws := chilkat.NewStringBuilder()
    sbJws.Append("eyJhbGciOiJFUzI1NiJ9")
    sbJws.Append(".")
    sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
    sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
    sbJws.Append(".")
    sbJws.Append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA")
    sbJws.Append("pmWQxfKTUJqPP3-Kg6NU1Q")

    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 ECC 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": "ES256"
    // 	}

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