1 files changed, 140 insertions, 6 deletions
diff --git a/app/main.go b/app/main.go
index 60585b4..b3f7265 100644
--- a/app/main.go
+++ b/app/main.go
@@ -1,25 +1,134 @@
 package main
 
 import (
+	"encoding/json"
 	"fmt"
+	"net/http"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"syscall"
 )
 
+type TokenResponse struct {
+	Token       string `json:"token"`
+	AccessToken string `json:"access_token"`
+	Expires     int    `json:"expires_in"`
+	IssuedAt    string `json:"issued_at"`
+}
+
+type ManiFest struct {
+	Name     string     `json:"name"`
+	Tag      string     `json:"tag"`
+	FSLayers []fsLayers `json:"fsLayers"`
+}
+
+type fsLayers struct {
+	BlobSum string `json:"blobSum"`
+}
+
+func getToken(repo, image string) (*TokenResponse, error) {
+	url := fmt.Sprintf("https://auth.docker.io/token?service=registry.docker.io&scope=repository:%s/%s:pull", repo, image)
+
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+
+	var token TokenResponse
+
+	err = json.NewDecoder(resp.Body).Decode(&token)
+	if err != nil {
+		return nil, err
+	}
+
+	return &token, nil
+}
+
+func getManifest(repo, image, tag string, token string) (*ManiFest, error) {
+	url := fmt.Sprintf("https://registry.hub.docker.com/v2/%s/%s/manifests/%s", repo, image, tag)
+
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
+	req.Header.Add("Accept", "application/vnd.docker.distribution.manifest.list.v1+json")
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+
+	var manifest ManiFest
+
+	err = json.NewDecoder(resp.Body).Decode(&manifest)
+	if err != nil {
+		return nil, err
+	}
+
+	return &manifest, nil
+}
+
+func downloadBlob(image, blobSum, token, tmpDir string) error {
+	url := fmt.Sprintf("https://registry-1.docker.io/v2/library/%s/blobs/%s", image, blobSum)
+
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return err
+	}
+
+	defer resp.Body.Close()
+
+	out, err := os.Create("/tmp/layer")
+	if err != nil {
+		return err
+	}
+
+	defer out.Close()
+
+	_, err = out.ReadFrom(resp.Body)
+	if err != nil {
+		return err
+	}
+
+	err = exec.Command("tar", "xf", "/tmp/layer", "-C", tmpDir).Run()
+	if err != nil {
+		return err
+	}
+
+	return os.RemoveAll("/tmp/layer")
+}
+
 func main() {
+	img := os.Args[2]
+	split := strings.Split(img, ":")
+	repo := "library"
+	image := split[0]
+	tag := "latest"
+	if len(split) == 2 {
+		tag = split[1]
+	}
+
 	command := os.Args[3]
 	args := os.Args[4:len(os.Args)]
 	tmpDir := "/tmp/mydocker"
 
-	cmd := exec.Command(command, args...)
-
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-
 	_ = os.Mkdir(tmpDir, 0755)
+	defer os.RemoveAll(tmpDir)
 
 	err := exec.Command("mkdir", "-p", filepath.Join(tmpDir, filepath.Dir(command))).Run()
 	if err != nil {
@@ -27,6 +136,31 @@ func main() {
 		os.Exit(1)
 	}
 
+	token, err := getToken(repo, image)
+	if err != nil {
+		fmt.Printf("Err: %v", err)
+		os.Exit(1)
+	}
+
+	manifest, err := getManifest(repo, image, tag, token.Token)
+	if err != nil {
+		fmt.Printf("Err: %v", err)
+		os.Exit(1)
+	}
+
+	for _, layer := range manifest.FSLayers {
+		if err = downloadBlob(image, layer.BlobSum, token.Token, tmpDir); err != nil {
+			fmt.Printf("Err: %v", err)
+			os.Exit(1)
+		}
+	}
+
+	cmd := exec.Command(command, args...)
+
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
 	err = exec.Command("cp", command, filepath.Join(tmpDir, command)).Run()
 	if err != nil {
 		fmt.Printf("Err: %v", err)