CMS Signature Creation/Validation with Swift and OpenSSL

gistfile1.txt

        let testBundle = Bundle(for: type(of: self))
        
        guard let textUrl = testBundle.url(forResource: "test_message", withExtension: "txt"),
            let signingKeyUrl = testBundle.url(forResource: "key", withExtension: "pem"),
            let signingCertUrl = testBundle.url(forResource: "cert", withExtension: "pem") else {
                exit(1)
        }
        
        let certFileObject = signingCertUrl.path.withCString { filePtr in
            return fopen(filePtr, "rb")
        }
        defer {
            fclose(certFileObject)
        }
        
        let keyFileObject = signingKeyUrl.path.withCString { filePtr in
            return fopen(filePtr, "rb")
        }
        defer {
            fclose(keyFileObject)
        }
        
        guard let key = PEM_read_PrivateKey(keyFileObject, nil, nil, nil),
            let cert = PEM_read_X509(certFileObject, nil, nil, nil) else {
                exit(1)
        }
        
        OpenSSL_add_all_ciphers()
        OpenSSL_add_all_digests()
        OPENSSL_add_all_algorithms_conf()
        
        guard let textData = FileManager.default.contents(atPath: textUrl.path) else {
            print("Unable to read text file")
            exit(1)
        }
        
        guard let textBIO = BIO_new(BIO_s_mem()) else {
            print("Unable to create textBIO")
            exit(1)
        }
        
        _ = textData.withUnsafeBytes({dataBytes in
            BIO_write(textBIO, dataBytes, Int32(textData.count))
        })
        
        guard let cms = CMS_sign(cert, key, nil, textBIO, UInt32(CMS_BINARY)) else {
            print("Unale to sign data")
            exit(1)
        }
        
        print("cms : \(cms)")
        
        let store = X509_STORE_new()
        X509_STORE_add_cert(store, cert)
        
        let outBIO = BIO_new(BIO_s_mem())
        let result = CMS_verify(cms, nil, store, nil, outBIO, 0)
        print("result : \(result)")
        
        if result != 1 {
            ERR_print_errors(outBIO!)
//            let errorCode: UInt = ERR_get_error()
//            print("ERROR : \(String(format: "%2X", errorCode))")
        }
        
        var ptr = UnsafeRawPointer(bitPattern: 1)!
        let cnt = BIO_ctrl(outBIO, BIO_CTRL_INFO, 1, &ptr)
        
        // Create data from pointer and count:
        let outBIOData = Data(bytes: ptr, count: cnt)
        let outBIOStr = String(data: outBIOData, encoding: .utf8)
        
        print("outBIOStr : \(String(describing: outBIOStr))")