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/params/pia.go

@@ -0,0 +1,87 @@
+package params
+
+import (
+	"fmt"
+	"math/rand"
+
+	libparams "github.com/qdm12/golibs/params"
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+	"github.com/qdm12/private-internet-access-docker/internal/models"
+)
+
+// GetUser obtains the user to use to connect to the VPN servers
+func (p *paramsReader) GetUser() (s string, err error) {
+	defer func() {
+		unsetenvErr := p.unsetEnv("USER")
+		if err == nil {
+			err = unsetenvErr
+		}
+	}()
+	s, err = p.envParams.GetEnv("USER")
+	if err != nil {
+		return "", err
+	} else if len(s) == 0 {
+		return s, fmt.Errorf("USER environment variable cannot be empty")
+	}
+	return s, nil
+}
+
+// GetPassword obtains the password to use to connect to the VPN servers
+func (p *paramsReader) GetPassword() (s string, err error) {
+	defer func() {
+		unsetenvErr := p.unsetEnv("PASSWORD")
+		if err == nil {
+			err = unsetenvErr
+		}
+	}()
+	s, err = p.envParams.GetEnv("PASSWORD")
+	if err != nil {
+		return "", err
+	} else if len(s) == 0 {
+		return s, fmt.Errorf("PASSWORD environment variable cannot be empty")
+	}
+	return s, nil
+}
+
+// GetPortForwarding obtains if port forwarding on the VPN provider server
+// side is enabled or not from the environment variable PORT_FORWARDING
+func (p *paramsReader) GetPortForwarding() (activated bool, err error) {
+	s, err := p.envParams.GetEnv("PORT_FORWARDING", libparams.Default("off"))
+	if err != nil {
+		return false, err
+	}
+	// Custom for retro-compatibility
+	if s == "false" || s == "off" {
+		return false, nil
+	} else if s == "true" || s == "on" {
+		return true, nil
+	}
+	return false, fmt.Errorf("PORT_FORWARDING can only be \"on\" or \"off\"")
+}
+
+// GetPortForwardingStatusFilepath obtains the port forwarding status file path
+// from the environment variable PORT_FORWARDING_STATUS_FILE
+func (p *paramsReader) GetPortForwardingStatusFilepath() (filepath models.Filepath, err error) {
+	filepathStr, err := p.envParams.GetPath("PORT_FORWARDING_STATUS_FILE", libparams.Default("/forwarded_port"))
+	return models.Filepath(filepathStr), err
+}
+
+// GetPIAEncryption obtains the encryption level for the PIA connection
+// from the environment variable ENCRYPTION
+func (p *paramsReader) GetPIAEncryption() (models.PIAEncryption, error) {
+	s, err := p.envParams.GetValueIfInside("ENCRYPTION", []string{"normal", "strong"}, libparams.Default("strong"))
+	return models.PIAEncryption(s), err
+}
+
+// GetPIARegion obtains the region for the PIA server from the
+// environment variable REGION
+func (p *paramsReader) GetPIARegion() (region models.PIARegion, err error) {
+	choices := []string{
+		string(constants.AUMelbourne), string(constants.AUPerth), string(constants.AUSydney), string(constants.Austria), string(constants.Belgium), string(constants.CAMontreal), string(constants.CAToronto), string(constants.CAVancouver), string(constants.CzechRepublic), string(constants.DEBerlin), string(constants.DEFrankfurt), string(constants.Denmark), string(constants.Finland), string(constants.France), string(constants.HongKong), string(constants.Hungary), string(constants.India), string(constants.Ireland), string(constants.Israel), string(constants.Italy), string(constants.Japan), string(constants.Luxembourg), string(constants.Mexico), string(constants.Netherlands), string(constants.NewZealand), string(constants.Norway), string(constants.Poland), string(constants.Romania), string(constants.Singapore), string(constants.Spain), string(constants.Sweden), string(constants.Switzerland), string(constants.UAE), string(constants.UKLondon), string(constants.UKManchester), string(constants.UKSouthampton), string(constants.USAtlanta), string(constants.USCalifornia), string(constants.USChicago), string(constants.USDenver), string(constants.USEast), string(constants.USFlorida), string(constants.USHouston), string(constants.USLasVegas), string(constants.USNewYorkCity), string(constants.USSeattle), string(constants.USSiliconValley), string(constants.USTexas), string(constants.USWashingtonDC), string(constants.USWest),
+	}
+	s, err := p.envParams.GetValueIfInside("REGION", choices)
+	if len(s) == 0 { // Suggestion by @rorph https://github.com/rorph
+		s = choices[rand.Int()%len(choices)]
+	}
+	return models.PIARegion(s), err
+}