Rewrite of the entrypoint in Golang (#71)

- General improvements
    - Parallel download of only needed files at start
    - Prettier console output with all streams merged (openvpn, unbound, shadowsocks etc.)
    - Simplified Docker final image
    - Faster bootup
- DNS over TLS
    - Finer grain blocking at DNS level: malicious, ads and surveillance
    - Choose your DNS over TLS providers
    - Ability to use multiple DNS over TLS providers for DNS split horizon
    - Environment variables for DNS logging
    - DNS block lists needed are downloaded and built automatically at start, in parallel
- PIA
    - A random region is selected if the REGION parameter is left empty (thanks @rorph for your PR)
    - Routing and iptables adjusted so it can work as a Kubernetes pod sidecar (thanks @rorph for your PR)

internal/openvpn/auth.go

@@ -0,0 +1,23 @@
+package openvpn
+
+import (
+	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+)
+
+// WriteAuthFile writes the OpenVPN auth file to disk with the right permissions
+func (c *configurator) WriteAuthFile(user, password string, uid, gid int) error {
+	authExists, err := c.fileManager.FileExists(string(constants.OpenVPNAuthConf))
+	if err != nil {
+		return err
+	} else if authExists { // in case of container stop/start
+		c.logger.Info("%s: %s already exists", logPrefix, constants.OpenVPNAuthConf)
+		return nil
+	}
+	c.logger.Info("%s: writing auth file %s", logPrefix, constants.OpenVPNAuthConf)
+	return c.fileManager.WriteLinesToFile(
+		string(constants.OpenVPNAuthConf),
+		[]string{user, password},
+		files.FileOwnership(uid, gid),
+		files.FilePermissions(0400))
+}

internal/openvpn/command.go

@@ -0,0 +1,28 @@
+package openvpn
+
+import (
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+)
+
+func (c *configurator) Start() (stdout io.ReadCloser, err error) {
+	c.logger.Info("%s: starting openvpn", logPrefix)
+	stdout, _, _, err = c.commander.Start("openvpn", "--config", string(constants.OpenVPNConf))
+	return stdout, err
+}
+
+func (c *configurator) Version() (string, error) {
+	output, err := c.commander.Run("openvpn", "--version")
+	if err != nil && err.Error() != "exit status 1" {
+		return "", err
+	}
+	firstLine := strings.Split(output, "\n")[0]
+	words := strings.Fields(firstLine)
+	if len(words) < 2 {
+		return "", fmt.Errorf("openvpn --version: first line is too short: %q", firstLine)
+	}
+	return words[1], nil
+}

internal/openvpn/openvpn.go

@@ -0,0 +1,35 @@
+package openvpn
+
+import (
+	"io"
+	"os"
+
+	"github.com/qdm12/golibs/command"
+	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/golibs/logging"
+)
+
+const logPrefix = "openvpn configurator"
+
+type Configurator interface {
+	Version() (string, error)
+	WriteAuthFile(user, password string, uid, gid int) error
+	CheckTUN() error
+	Start() (stdout io.ReadCloser, err error)
+}
+
+type configurator struct {
+	fileManager files.FileManager
+	logger      logging.Logger
+	commander   command.Commander
+	openFile    func(name string, flag int, perm os.FileMode) (*os.File, error)
+}
+
+func NewConfigurator(logger logging.Logger, fileManager files.FileManager) Configurator {
+	return &configurator{
+		fileManager: fileManager,
+		logger:      logger,
+		commander:   command.NewCommander(),
+		openFile:    os.OpenFile,
+	}
+}

internal/openvpn/tun.go

@@ -0,0 +1,21 @@
+package openvpn
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+)
+
+// CheckTUN checks the tunnel device is present and accessible
+func (c *configurator) CheckTUN() error {
+	c.logger.Info("%s: checking for device %s", logPrefix, constants.TunnelDevice)
+	f, err := c.openFile(string(constants.TunnelDevice), os.O_RDWR, 0)
+	if err != nil {
+		return fmt.Errorf("TUN device is not available: %w", err)
+	}
+	if err := f.Close(); err != nil {
+		c.logger.Warn("Could not close TUN device file: %s", err)
+	}
+	return nil
+}