Add support for custom tls.Configs

[lukescott]

This adds the ability to customize the tls.Config object so you can:

• Specify a custom RootCA (instead of skip verify)
• Specify a client certificate for authentication w/ or w/out a password

Example of how it would be used:

package main

import (
    "crypto/tls"
    "crypto/x509"
    "database/sql"
    "fmt"
    "github.com/lukescott/mysql"
    "io/ioutil"
    "log"
)

func main() {
    rootCAs := x509.NewCertPool()
    {
        pem, err := ioutil.ReadFile("/path/ca-cert.pem")
        if err != nil {
            log.Fatal(err)
        }
        if ok := rootCAs.AppendCertsFromPEM(pem); !ok {
            log.Fatal("Failed to append PEM.")
        }
    }
    clientCerts := make([]tls.Certificate, 0, 1)
    {
        certs, err := tls.LoadX509KeyPair("/path/client-cert.pem", "/path/client-key.pem")
        if err != nil {
            log.Fatal(err)
        }
        clientCerts = append(clientCerts, certs)
    }
    mysql.RegisterTLSConfig("custom", &tls.Config{
        RootCAs:      rootCAs,
        Certificates: clientCerts,
    })
    db, err := sql.Open("mysql", "user@tcp(localhost:3306)/test?tls=custom")
    if err != nil {
        log.Fatal(err)
    }
    var row string
    err = db.QueryRow("SHOW DATABASES").Scan(&row)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%#v\n", row)
}

[julienschmidt]

What is this interface for?

[lukescott]

Not needed, as you commented on later.

[lukescott]

Ok all the changes are made. I'm not very good at writing documentation, but gave it my best shot.

[julienschmidt]

Sorry for my delayed response.
Please keep it up here. It is not necessary to make a new section for a single parameter. Just note that you can register your own configurations and refer to the godoc.
Ignore the INFILE section, this will be reworked before the next release.

[julienschmidt]

LGTM
@arnehormann ?

[arnehormann]

@julienschmidt LGTM; I'd love to have tests for it, though.
Sorry for the late reaction, I thought it's sufficient if one non-author okays it - which would be you for external contributions in most cases.

[julienschmidt]

Yes, this is the general case. But I'm more comfortable if another pair of eyes checks this PR to make sure we didn't miss a thing.

[julienschmidt]

Missed this one... the extra scopes are a bit confusing since they are not conventional Go-style.

[lukescott]

Missed what?

[julienschmidt]

Missed the note on this line 😉

[julienschmidt]

Please replace the TestTLS function in driver_test.go with the following code:

func TestTLS(t *testing.T) {
    tlsTest := func(dbt *DBTest) {
        if err := dbt.db.Ping(); err != nil {
            if err == errNoTLS {
                dbt.Skip("Server does not support TLS")
            } else {
                dbt.Fatalf("Error on Ping: %s", err.Error())
            }
        }

        rows := dbt.mustQuery("SHOW STATUS LIKE 'Ssl_cipher'")

        var variable, value *sql.RawBytes
        for rows.Next() {
            if err := rows.Scan(&variable, &value); err != nil {
                dbt.Fatal(err.Error())
            }

            if value == nil {
                dbt.Fatal("No Cipher")
            }
        }
    }

    runTests(t, dsn+"&tls=skip-verify", tlsTest)

    // Verify that registering / using a custom cfg works
    RegisterTLSConfig("custom-skip-verify", &tls.Config{
        InsecureSkipVerify: true,
    })
    runTests(t, dsn+"&tls=custom-skip-verify", tlsTest)
}

Also add "crypto/tls" to the package imports of driver_test.go

This adds a simple test, that verifies that registering a custom tls.Config works (regardless of the server supports TLS)

[lukescott]

Ok, I've made the changes. Tests pass. Here is the diff. Anything else before I make the next commit?

(Scopes removed in example, test added, tls.Config{} changed to &tls.Config{})

...

[julienschmidt]

No, looks good to me now.
Please commit and wait for @arnehormann to make the final LGTM in order to merge this PR.

[julienschmidt]

Oh sorry, he already did earlier. Just commit and I merge it

[julienschmidt]

Thanks a lot!