Pull request: * all: move internal Go packages to internal/

Merge in DNS/adguard-home from 2234-move-to-internal to master

Squashed commit of the following:

commit d26a288cabeac86f9483fab307677b1027c78524
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Oct 30 12:44:18 2020 +0300

    * all: move internal Go packages to internal/

    Closes #2234.

internal/home/auth_glinet.go

@@ -0,0 +1,102 @@
+package home
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"os"
+	"time"
+	"unsafe"
+
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// GLMode - enable GL-Inet compatibility mode
+var GLMode bool
+
+var glFilePrefix = "/tmp/gl_token_"
+
+const glTokenTimeoutSeconds = 3600
+const glCookieName = "Admin-Token"
+
+func glProcessRedirect(w http.ResponseWriter, r *http.Request) bool {
+	if !GLMode {
+		return false
+	}
+	// redirect to gl-inet login
+	host, _, _ := net.SplitHostPort(r.Host)
+	url := "http://" + host
+	log.Debug("Auth: redirecting to %s", url)
+	http.Redirect(w, r, url, http.StatusFound)
+	return true
+}
+
+func glProcessCookie(r *http.Request) bool {
+	if !GLMode {
+		return false
+	}
+
+	glCookie, glerr := r.Cookie(glCookieName)
+	if glerr != nil {
+		return false
+	}
+
+	log.Debug("Auth: GL cookie value: %s", glCookie.Value)
+	if glCheckToken(glCookie.Value) {
+		return true
+	}
+	log.Info("Auth: invalid GL cookie value: %s", glCookie)
+	return false
+}
+
+func glCheckToken(sess string) bool {
+	tokenName := glFilePrefix + sess
+	_, err := os.Stat(tokenName)
+	if err != nil {
+		log.Error("os.Stat: %s", err)
+		return false
+	}
+	tokenDate := glGetTokenDate(tokenName)
+	now := uint32(time.Now().UTC().Unix())
+	return now <= (tokenDate + glTokenTimeoutSeconds)
+}
+
+func archIsLittleEndian() bool {
+	var i int32 = 0x01020304
+	u := unsafe.Pointer(&i)
+	pb := (*byte)(u)
+	b := *pb
+	return (b == 0x04)
+}
+
+func glGetTokenDate(file string) uint32 {
+	f, err := os.Open(file)
+	if err != nil {
+		log.Error("os.Open: %s", err)
+		return 0
+	}
+	var dateToken uint32
+	bs, err := ioutil.ReadAll(f)
+	if err != nil {
+		log.Error("ioutil.ReadAll: %s", err)
+		return 0
+	}
+	buf := bytes.NewBuffer(bs)
+
+	if archIsLittleEndian() {
+		err := binary.Read(buf, binary.LittleEndian, &dateToken)
+		if err != nil {
+			log.Error("binary.Read: %s", err)
+			return 0
+		}
+	} else {
+		err := binary.Read(buf, binary.BigEndian, &dateToken)
+		if err != nil {
+			log.Error("binary.Read: %s", err)
+			return 0
+		}
+	}
+	return dateToken
+}