open-nomad/client/allocdir/task_dir_test.go
Michael Schurter 10c3bad652 client: never embed alloc_dir in chroot
Fixes #2522

Skip embedding client.alloc_dir when building chroot. If a user
configures a Nomad client agent so that the chroot_env will embed the
client.alloc_dir, Nomad will happily infinitely recurse while building
the chroot until something horrible happens. The best case scenario is
the filesystem's path length limit is hit. The worst case scenario is
disk space is exhausted.

A bad agent configuration will look something like this:

```hcl
data_dir = "/tmp/nomad-badagent"

client {
  enabled = true

  chroot_env {
    # Note that the source matches the data_dir
    "/tmp/nomad-badagent" = "/ohno"
    # ...
  }
}
```

Note that `/ohno/client` (the state_dir) will still be created but not
`/ohno/alloc` (the alloc_dir).
While I cannot think of a good reason why someone would want to embed
Nomad's client (and possibly server) directories in chroots, there
should be no cause for harm. chroots are only built when Nomad runs as
root, and Nomad disables running exec jobs as root by default. Therefore
even if client state is copied into chroots, it will be inaccessible to
tasks.

Skipping the `data_dir` and `{client,server}.state_dir` is possible, but
this PR attempts to implement the minimum viable solution to reduce risk
of unintended side effects or bugs.

When running tests as root in a vm without the fix, the following error
occurs:

```
=== RUN   TestAllocDir_SkipAllocDir
    alloc_dir_test.go:520:
                Error Trace:    alloc_dir_test.go:520
                Error:          Received unexpected error:
                                Couldn't create destination file /tmp/TestAllocDir_SkipAllocDir1457747331/001/nomad/test/testtask/nomad/test/testtask/.../nomad/test/testtask/secrets/.nomad-mount: open /tmp/TestAllocDir_SkipAllocDir1457747331/001/nomad/test/.../testtask/secrets/.nomad-mount: file name too long
                Test:           TestAllocDir_SkipAllocDir
--- FAIL: TestAllocDir_SkipAllocDir (22.76s)
```

Also removed unused Copy methods on AllocDir and TaskDir structs.

Thanks to @eveld for not letting me forget about this!
2021-10-18 09:22:01 -07:00

139 lines
3.7 KiB
Go

package allocdir
import (
"io/ioutil"
"os"
"path/filepath"
"testing"
"github.com/hashicorp/nomad/helper/testlog"
)
// Test that building a chroot will skip nonexistent directories.
func TestTaskDir_EmbedNonexistent(t *testing.T) {
tmp, err := ioutil.TempDir("", "AllocDir")
if err != nil {
t.Fatalf("Couldn't create temp dir: %v", err)
}
defer os.RemoveAll(tmp)
d := NewAllocDir(testlog.HCLogger(t), tmp, "test")
defer d.Destroy()
td := d.NewTaskDir(t1.Name)
if err := d.Build(); err != nil {
t.Fatalf("Build() failed: %v", err)
}
fakeDir := "/foobarbaz"
mapping := map[string]string{fakeDir: fakeDir}
if err := td.embedDirs(mapping); err != nil {
t.Fatalf("embedDirs(%v) should should skip %v since it does not exist", mapping, fakeDir)
}
}
// Test that building a chroot copies files from the host into the task dir.
func TestTaskDir_EmbedDirs(t *testing.T) {
tmp, err := ioutil.TempDir("", "AllocDir")
if err != nil {
t.Fatalf("Couldn't create temp dir: %v", err)
}
defer os.RemoveAll(tmp)
d := NewAllocDir(testlog.HCLogger(t), tmp, "test")
defer d.Destroy()
td := d.NewTaskDir(t1.Name)
if err := d.Build(); err != nil {
t.Fatalf("Build() failed: %v", err)
}
// Create a fake host directory, with a file, and a subfolder that contains
// a file.
host, err := ioutil.TempDir("", "AllocDirHost")
if err != nil {
t.Fatalf("Couldn't create temp dir: %v", err)
}
defer os.RemoveAll(host)
subDirName := "subdir"
subDir := filepath.Join(host, subDirName)
if err := os.MkdirAll(subDir, 0777); err != nil {
t.Fatalf("Failed to make subdir %v: %v", subDir, err)
}
file := "foo"
subFile := "bar"
if err := ioutil.WriteFile(filepath.Join(host, file), []byte{'a'}, 0777); err != nil {
t.Fatalf("Couldn't create file in host dir %v: %v", host, err)
}
if err := ioutil.WriteFile(filepath.Join(subDir, subFile), []byte{'a'}, 0777); err != nil {
t.Fatalf("Couldn't create file in host subdir %v: %v", subDir, err)
}
// Create mapping from host dir to task dir.
taskDest := "bin/test/"
mapping := map[string]string{host: taskDest}
if err := td.embedDirs(mapping); err != nil {
t.Fatalf("embedDirs(%v) failed: %v", mapping, err)
}
exp := []string{filepath.Join(td.Dir, taskDest, file), filepath.Join(td.Dir, taskDest, subDirName, subFile)}
for _, f := range exp {
if _, err := os.Stat(f); os.IsNotExist(err) {
t.Fatalf("File %v not embedded: %v", f, err)
}
}
}
// Test that task dirs for image based isolation don't require root.
func TestTaskDir_NonRoot_Image(t *testing.T) {
if os.Geteuid() == 0 {
t.Skip("test should be run as non-root user")
}
tmp, err := ioutil.TempDir("", "AllocDir")
if err != nil {
t.Fatalf("Couldn't create temp dir: %v", err)
}
defer os.RemoveAll(tmp)
d := NewAllocDir(testlog.HCLogger(t), tmp, "test")
defer d.Destroy()
td := d.NewTaskDir(t1.Name)
if err := d.Build(); err != nil {
t.Fatalf("Build() failed: %v", err)
}
if err := td.Build(false, nil); err != nil {
t.Fatalf("TaskDir.Build failed: %v", err)
}
}
// Test that task dirs with no isolation don't require root.
func TestTaskDir_NonRoot(t *testing.T) {
if os.Geteuid() == 0 {
t.Skip("test should be run as non-root user")
}
tmp, err := ioutil.TempDir("", "AllocDir")
if err != nil {
t.Fatalf("Couldn't create temp dir: %v", err)
}
defer os.RemoveAll(tmp)
d := NewAllocDir(testlog.HCLogger(t), tmp, "test")
defer d.Destroy()
td := d.NewTaskDir(t1.Name)
if err := d.Build(); err != nil {
t.Fatalf("Build() failed: %v", err)
}
if err := td.Build(false, nil); err != nil {
t.Fatalf("TaskDir.Build failed: %v", err)
}
// ${TASK_DIR}/alloc should not exist!
if _, err = os.Stat(td.SharedTaskDir); !os.IsNotExist(err) {
t.Fatalf("Expected a NotExist error for shared alloc dir in task dir: %q", td.SharedTaskDir)
}
}