TLS with selfsigned certificate

Question

I'm trying to establish a TLS connection with the use of a self signed server certificate.

I generated the certificate with this example code: http://golang.org/src/pkg/crypto/tls/generate_cert.go

My relevant client code looks like that:

// server cert is self signed -> server_cert == ca_cert CA_Pool := x509.NewCertPool() severCert, err := ioutil.ReadFile("./cert.pem") if err != nil {     log.Fatal("Could not load server certificate!") } CA_Pool.AppendCertsFromPEM(severCert)  config := tls.Config{RootCAs: CA_Pool}  conn, err := tls.Dial("tcp", "127.0.0.1:8000", &config) if err != nil {     log.Fatalf("client: dial: %s", err) } 

And the relevant server code like that:

cert, err := tls.LoadX509KeyPair("./cert.pem", "./key.pem") config := tls.Config{Certificates: []tls.Certificate{cert}} listener, err := tls.Listen("tcp", "127.0.0.1:8000", &config)  for {     conn, err := listener.Accept()     if err != nil {         log.Printf("server: accept: %s", err)         break     }     log.Printf("server: accepted from %s", conn.RemoteAddr())     go handleConnection(conn) } 

Because the server certificate is self signed is use the same certificate for the server and the clients CA_Pool however this does not seem to work since i always get this error:

client: dial: x509: certificate signed by unknown authority  (possibly because of "x509: invalid signature: parent certificate cannot sign this kind of certificate" while trying to verify  candidate authority certificate "serial:0") 

What's my mistake?

Answer 1

It finally worked with the go built in x509.CreateCertificate, the problem was that I did not set the IsCA:true flag, I only set the x509.KeyUsageCertSign which made creating the self signed certificate work, but crashed while verifying the cert chain.

Answer 2

The problem is that you need a CA certificate in the server-side config, and this CA must have signed the server's certificate.

I have written some Go code that will generate a CA certificate, but it hasn't been reviewed by anyone and is mostly a toy for playing around with client certs. The safest bet is probably to use openssl ca to generate and sign the certificate. The basic steps will be:

1. Generate a CA Certificate
2. Generate a Server key
3. Sign the Server key with the CA certificate
4. Add the CA Certificate to the client's tls.Config RootCAs
5. Set up the server's tls.Config with the Server key and signed certificate.