undocker/rootfs/rootfs_test.go

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package rootfs
import (
"archive/tar"
"bytes"
"encoding/json"
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"io"
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"testing"
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"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
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)
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func TestRootFS(t *testing.T) {
layer0 := tarball{
dir{name: "/", uid: 0},
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file{name: "/file", uid: 0, contents: bytes.NewBufferString("from 0")},
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}
layer1 := tarball{
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file{name: "/file", uid: 1, contents: bytes.NewBufferString("from 1")},
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}
layer2 := tarball{
dir{name: "/", uid: 2},
}
tests := []struct {
name string
image tarball
want []extractable
wantErr string
}{
{
name: "empty tarball",
image: tarball{manifest{}},
want: []extractable{},
},
{
name: "missing layer",
image: tarball{manifest{"layer0/layer.tar"}},
wantErr: "bad or missing manifest.json",
},
{
name: "basic file overwrite, layer order mixed",
image: tarball{
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file{name: "layer1/layer.tar", contents: layer1},
file{name: "layer0/layer.tar", contents: layer0},
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manifest{"layer0/layer.tar", "layer1/layer.tar"},
},
want: []extractable{
dir{name: "/", uid: 0},
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file{name: "/file", uid: 1, contents: bytes.NewBufferString("from 1")},
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},
},
{
name: "directory overwrite retains original dir",
image: tarball{
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file{name: "layer2/layer.tar", contents: layer2},
file{name: "layer0/layer.tar", contents: layer0},
file{name: "layer1/layer.tar", contents: layer1},
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manifest{"layer0/layer.tar", "layer1/layer.tar", "layer2/layer.tar"},
},
want: []extractable{
dir{name: "/", uid: 0},
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file{name: "/file", uid: 1, contents: bytes.NewBufferString("from 1")},
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dir{name: "/", uid: 2},
},
},
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{
name: "simple whiteout",
image: tarball{
file{name: "layer0/layer.tar", contents: tarball{
file{name: "filea"},
file{name: "fileb"},
dir{name: "dira"},
dir{name: "dirb"},
}},
file{name: "layer1/layer.tar", contents: tarball{
hardlink{name: ".wh.filea"},
hardlink{name: ".wh.dira"},
}},
manifest{"layer0/layer.tar", "layer1/layer.tar"},
},
want: []extractable{
file{name: "fileb"},
dir{name: "dirb"},
},
},
{
name: "whiteout with override",
image: tarball{
file{name: "layer0/layer.tar", contents: tarball{
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file{name: "file", contents: bytes.NewBufferString("from 0")},
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}},
file{name: "layer1/layer.tar", contents: tarball{
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hardlink{name: ".wh.file"},
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}},
file{name: "layer2/layer.tar", contents: tarball{
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file{name: "file", contents: bytes.NewBufferString("from 3")},
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}},
manifest{
"layer0/layer.tar",
"layer1/layer.tar",
"layer2/layer.tar",
},
},
want: []extractable{
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file{name: "file", contents: bytes.NewBufferString("from 3")},
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},
},
{
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name: "directories do not whiteout",
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image: tarball{
file{name: "layer0/layer.tar", contents: tarball{
dir{name: "dir"},
}},
file{name: "layer1/layer.tar", contents: tarball{
dir{name: ".wh.dir"},
}},
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manifest{"layer0/layer.tar", "layer1/layer.tar"},
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},
want: []extractable{
dir{name: "dir"},
dir{name: ".wh.dir"},
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},
},
{
name: "simple readdir whiteout",
image: tarball{
file{name: "layer0/layer.tar", contents: tarball{
dir{name: "a"},
file{name: "a/filea"},
}},
file{name: "layer1/layer.tar", contents: tarball{
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dir{name: "a"},
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file{name: "a/fileb"},
hardlink{name: "a/.wh..wh..opq"},
}},
manifest{"layer0/layer.tar", "layer1/layer.tar"},
},
want: []extractable{
dir{name: "a"},
file{name: "a/fileb"},
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},
},
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}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
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in := bytes.NewReader(tt.image.Bytes())
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out := bytes.Buffer{}
err := RootFS(in, &out)
if tt.wantErr != "" {
assert.EqualError(t, err, tt.wantErr)
return
}
require.NoError(t, err)
got := extract(t, &out)
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assert.Equal(t, tt.want, got)
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})
}
}
// Helpers
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type tarrer interface {
tar(*tar.Writer)
}
type byter interface {
Bytes() []byte
}
type tarball []tarrer
func (tb tarball) Bytes() []byte {
buf := bytes.Buffer{}
tw := tar.NewWriter(&buf)
for _, member := range tb {
member.tar(tw)
}
tw.Close()
return buf.Bytes()
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}
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// extractable is an empty interface for comparing extracted outputs in tests.
// Using that just to avoid the ugly `interface{}`.
type extractable interface{}
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type dir struct {
name string
uid int
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}
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func (d dir) tar(tw *tar.Writer) {
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hdr := &tar.Header{
Typeflag: tar.TypeDir,
Name: d.name,
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Mode: 0644,
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Uid: d.uid,
}
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tw.WriteHeader(hdr)
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}
type file struct {
name string
uid int
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contents byter
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}
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func (f file) tar(tw *tar.Writer) {
var contentbytes []byte
if f.contents != nil {
contentbytes = f.contents.Bytes()
}
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hdr := &tar.Header{
Typeflag: tar.TypeReg,
Name: f.name,
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Mode: 0644,
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Uid: f.uid,
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Size: int64(len(contentbytes)),
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}
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tw.WriteHeader(hdr)
tw.Write(contentbytes)
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}
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type manifest []string
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func (m manifest) tar(tw *tar.Writer) {
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b, err := json.Marshal(dockerManifestJSON{{Layers: m}})
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if err != nil {
panic("testerr")
}
file{
name: "manifest.json",
uid: 0,
contents: bytes.NewBuffer(b),
}.tar(tw)
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}
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type hardlink struct {
name string
uid int
}
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func (h hardlink) tar(tw *tar.Writer) {
tw.WriteHeader(&tar.Header{
Typeflag: tar.TypeLink,
Name: h.name,
Mode: 0644,
Uid: h.uid,
})
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}
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func extract(t *testing.T, r io.Reader) []extractable {
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t.Helper()
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ret := []extractable{}
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tr := tar.NewReader(r)
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for {
hdr, err := tr.Next()
if err == io.EOF {
break
}
require.NoError(t, err)
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var elem extractable
switch hdr.Typeflag {
case tar.TypeDir:
elem = dir{name: hdr.Name, uid: hdr.Uid}
case tar.TypeReg:
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f := file{name: hdr.Name, uid: hdr.Uid}
if hdr.Size > 0 {
var buf bytes.Buffer
io.Copy(&buf, tr)
f.contents = &buf
}
elem = f
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}
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ret = append(ret, elem)
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}
return ret
}