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|
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"
_ = os.Mkdir(tmpDir, 0755)
defer os.RemoveAll(tmpDir)
err := exec.Command("mkdir", "-p", filepath.Join(tmpDir, filepath.Dir(command))).Run()
if err != nil {
fmt.Printf("Err: %v", err)
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)
os.Exit(1)
}
cmd.SysProcAttr = &syscall.SysProcAttr{
Chroot: tmpDir,
Cloneflags: syscall.CLONE_NEWPID,
}
err = cmd.Run()
if err != nil {
if exitError, ok := err.(*exec.ExitError); ok {
os.Exit(exitError.ExitCode())
} else {
fmt.Printf("Err: %v", err)
os.Exit(1)
}
}
}
|
