package main

import (
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"os"
	"os/exec"
	"strings"
)

func usage() {
	fmt.Printf("Usage: %s <keyserver> <image> <device>\n", os.Args[0])
	fmt.Printf("Example: %s https://keyserver.example.com /path/to/image.img <device>\n", os.Args[0])
	fmt.Printf("Example: %s https://keyserver.example.com /path/to/image.img /dev/mapper/crypt1\n", os.Args[0])
	os.Exit(1)
}

func fileExists(path string) bool {
	_, err := os.Stat(path)
	return err == nil
}

func deviceExists(device string) bool {
	_, err := os.Stat("/dev/mapper/" + device)
	return err == nil
}

func keyserverReachable(url string) bool {
	resp, err := http.Head(url)
	if err != nil {
		return false
	}
	resp.Body.Close()
	return resp.StatusCode < 400
}

func getUUID() string {
	// Get CPU model name
	cpuinfo, _ := ioutil.ReadFile("/proc/cpuinfo")
	var model string
	for _, line := range strings.Split(string(cpuinfo), "\n") {
		if strings.HasPrefix(line, "model name") {
			model = line
			break
		}
	}
	// Get eth0 MAC address
	iface, err := net.InterfaceByName("eth0")
	mac := ""
	if err == nil {
		mac = iface.HardwareAddr.String()
	}
	// Get system UUID
	out, _ := exec.Command("sudo", "dmidecode", "-s", "system-uuid").Output()
	sysuuid := strings.TrimSpace(string(out))
	uuid := model + mac + sysuuid
	return uuid
}

func main() {
	log.SetFlags(0)
	if len(os.Args) != 4 {
		usage()
	}
	keyserver := os.Args[1]
	image := os.Args[2]
	device := os.Args[3]

	if !fileExists(image) {
		log.Printf("open_volume: (%s) Image file not found", device)
		os.Exit(1)
	}

	if !keyserverReachable(keyserver) {
		log.Printf("open_volume: (%s) Key server not reachable, exiting.", device)
		os.Exit(1)
	}

	if deviceExists(device) {
		fmt.Printf("open_volume: (%s) Device already open, exiting.\n", device)
		os.Exit(1)
	}

	uuid := getUUID()
	h := md5.Sum([]byte(uuid))
	keyid := hex.EncodeToString(h[:])

	log.Printf("open_volume: (%s) Downloading key from key server,", device)
	keyurl := fmt.Sprintf("%s/%s", keyserver, keyid)
	resp, err := http.Get(keyurl)
	if err != nil || resp.StatusCode != 200 {
		log.Printf("open_volume: (%s) Failed to download key from key server", device)
		os.Exit(1)
	}
	defer resp.Body.Close()

	tmpfile, err := ioutil.TempFile("", "keyfile")
	if err != nil {
		log.Printf("open_volume: (%s) Failed to create temp file", device)
		os.Exit(1)
	}
	defer os.Remove(tmpfile.Name())
	_, err = io.Copy(tmpfile, resp.Body)
	tmpfile.Close()
	if err != nil {
		log.Printf("open_volume: (%s) Failed to save key file", device)
		os.Exit(1)
	}

	log.Printf("open_volume:'%s' Key downloaded successfully, opening volume", device)
	cmd := exec.Command("/usr/sbin/cryptsetup", "luksOpen", image, device, "-d", tmpfile.Name())
	out, err := cmd.CombinedOutput()
	if err != nil {
		log.Printf("open_volume: (%s) Failed to open volume: %s", device, string(out))
		os.Exit(1)
	}

	log.Printf("open_volume: (%s) Volume opened successfully, removing key file", device)
	os.Exit(0)
}