151 lines
2.8 KiB
Go
151 lines
2.8 KiB
Go
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// The code in this file creates a Docker image layer containing the binary of the
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// application itself.
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package main
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import (
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"archive/tar"
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"bytes"
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"compress/gzip"
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"crypto/sha256"
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"encoding/json"
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"fmt"
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"io/ioutil"
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"log"
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"os"
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"time"
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)
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// This function creates a Docker-image digest (i.e. SHA256 hash with
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// algorithm-specification prefix)
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func Digest(b []byte) string {
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hash := sha256.New()
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hash.Write(b)
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return fmt.Sprintf("sha256:%x", hash.Sum(nil))
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}
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func GetImageOfCurrentExecutable() Image {
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binary := getCurrentBinary()
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tarArchive := createTarArchive(&map[string][]byte{
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"/main": binary,
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})
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configJson, configElem := createConfig([]string{Digest(tarArchive)})
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compressed := gzipArchive("Quinistry image", tarArchive)
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manifest := createManifest(&configElem, &compressed)
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manifestJson, _ := json.Marshal(manifest)
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return Image{
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Layer: compressed,
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LayerDigest: Digest(compressed),
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Manifest: manifestJson,
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ManifestDigest: Digest(manifestJson),
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Config: configJson,
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ConfigDigest: Digest(configJson),
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}
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}
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func getCurrentBinary() []byte {
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path, _ := os.Executable()
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file, _ := ioutil.ReadFile(path)
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return file
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}
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func createTarArchive(files *map[string][]byte) []byte {
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buf := new(bytes.Buffer)
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w := tar.NewWriter(buf)
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for name, file := range *files {
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hdr := &tar.Header{
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Name: name,
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// Everything is executable \o/
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Mode: 0755,
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Size: int64(len(file)),
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}
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w.WriteHeader(hdr)
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w.Write(file)
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}
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if err := w.Close(); err != nil {
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log.Fatalln(err)
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os.Exit(1)
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}
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return buf.Bytes()
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}
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func gzipArchive(name string, archive []byte) []byte {
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buf := new(bytes.Buffer)
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w := gzip.NewWriter(buf)
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w.Name = name
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w.Write(archive)
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if err := w.Close(); err != nil {
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log.Fatalln(err)
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os.Exit(1)
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}
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return buf.Bytes()
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}
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func createConfig(layerDigests []string) (configJson []byte, elem Element) {
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now := time.Now()
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imageConfig := &ImageConfig{
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Cmd: []string{"/main"},
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Env: []string{"PATH=/"},
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}
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rootFs := RootFs{
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DiffIds: layerDigests,
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Type: "layers",
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}
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history := []History{
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{
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Created: now,
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CreatedBy: "Quinistry magic",
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},
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}
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config := Config{
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Created: now,
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Author: "tazjin",
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Architecture: "amd64",
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Os: "linux",
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Config: imageConfig,
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RootFs: rootFs,
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History: history,
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}
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configJson, _ = json.Marshal(config)
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elem = Element{
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MediaType: ImageConfigMediaType,
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Size: len(configJson),
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Digest: Digest(configJson),
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}
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return
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}
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func createManifest(config *Element, layer *[]byte) Manifest {
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layers := []Element{
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{
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MediaType: LayerMediaType,
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Size: len(*layer),
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// Layers must contain the digest of the *gzipped* layer.
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Digest: Digest(*layer),
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},
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}
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return Manifest{
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SchemaVersion: 2,
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MediaType: ManifestMediaType,
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Config: *config,
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Layers: layers,
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}
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}
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