| 1 | //go:build linux |
| 2 | |
| 3 | package hostenv |
| 4 | |
| 5 | import ( |
| 6 | "os" |
| 7 | "path/filepath" |
| 8 | "strings" |
| 9 | "testing" |
| 10 | ) |
| 11 | |
| 12 | // U3 (census condition 2 on runHostEnv): write's path is fixed, and the |
| 13 | // file is written only through etc and etc/carlos held by descriptor, |
| 14 | // each a real directory this user owns and nobody else can write. |
| 15 | func TestWriteGoesOnlyThroughDirectoriesRootAloneCanWrite(t *testing.T) { |
| 16 | read := func(root string) string { |
| 17 | b, _ := os.ReadFile(filepath.Join(root, "etc", "carlos", "host.env")) |
| 18 | return string(b) |
| 19 | } |
| 20 | t.Run("lands whole, and replaces whole", func(t *testing.T) { |
| 21 | root := withHostEnvRoot(t) |
| 22 | if err := writeHostEnv(root, []byte("CARLOS_REGION=ie\n")); err != nil { |
| 23 | t.Fatal(err) |
| 24 | } |
| 25 | fi, err := os.Stat(filepath.Join(root, "etc", "carlos")) |
| 26 | if err != nil || fi.Mode().Perm()&0o022 != 0 || !fi.IsDir() { |
| 27 | t.Fatalf("created directory %v %v", fi, err) |
| 28 | } |
| 29 | first, err := os.Stat(filepath.Join(root, "etc", "carlos", "host.env")) |
| 30 | if err != nil { |
| 31 | t.Fatal(err) |
| 32 | } |
| 33 | if err := writeHostEnv(root, []byte("CARLOS_REGION=uk\n")); err != nil { |
| 34 | t.Fatal(err) |
| 35 | } |
| 36 | f, err := os.Stat(filepath.Join(root, "etc", "carlos", "host.env")) |
| 37 | if err != nil || f.Mode().Perm() != 0o600 || read(root) != "CARLOS_REGION=uk\n" { |
| 38 | t.Fatalf("host.env %v %v %q", f, err, read(root)) |
| 39 | } |
| 40 | // Replaced by rename, not rewritten in place: a reader holding the |
| 41 | // old file never sees part of the new one. |
| 42 | if os.SameFile(first, f) { |
| 43 | t.Fatal("host.env was rewritten in place") |
| 44 | } |
| 45 | ents, _ := os.ReadDir(filepath.Join(root, "etc", "carlos")) |
| 46 | if len(ents) != 1 { |
| 47 | t.Fatalf("left behind: %v", ents) |
| 48 | } |
| 49 | }) |
| 50 | for name, spoil := range map[string]func(t *testing.T, root string){ |
| 51 | "a group-writable etc/carlos": func(t *testing.T, root string) { |
| 52 | dir := filepath.Join(root, "etc", "carlos") |
| 53 | if err := os.Mkdir(dir, 0o755); err != nil { |
| 54 | t.Fatal(err) |
| 55 | } |
| 56 | if err := os.Chmod(dir, 0o775); err != nil { |
| 57 | t.Fatal(err) |
| 58 | } |
| 59 | }, |
| 60 | "a world-writable etc": func(t *testing.T, root string) { |
| 61 | if err := os.Chmod(filepath.Join(root, "etc"), 0o757); err != nil { |
| 62 | t.Fatal(err) |
| 63 | } |
| 64 | }, |
| 65 | "an etc/carlos another user owns": func(t *testing.T, root string) { |
| 66 | if err := os.Mkdir(filepath.Join(root, "etc", "carlos"), 0o755); err != nil { |
| 67 | t.Fatal(err) |
| 68 | } |
| 69 | was := hostEnvOwner |
| 70 | hostEnvOwner = func() int { return was() + 1 } |
| 71 | t.Cleanup(func() { hostEnvOwner = was }) |
| 72 | }, |
| 73 | "a symlinked etc/carlos": func(t *testing.T, root string) { |
| 74 | elsewhere := safeDir(t) |
| 75 | if err := os.Symlink(elsewhere, filepath.Join(root, "etc", "carlos")); err != nil { |
| 76 | t.Fatal(err) |
| 77 | } |
| 78 | }, |
| 79 | "a symlinked etc, an ancestor": func(t *testing.T, root string) { |
| 80 | elsewhere := safeDir(t) |
| 81 | if err := os.Mkdir(filepath.Join(elsewhere, "carlos"), 0o755); err != nil { |
| 82 | t.Fatal(err) |
| 83 | } |
| 84 | if err := os.Remove(filepath.Join(root, "etc")); err != nil { |
| 85 | t.Fatal(err) |
| 86 | } |
| 87 | if err := os.Symlink(elsewhere, filepath.Join(root, "etc")); err != nil { |
| 88 | t.Fatal(err) |
| 89 | } |
| 90 | }, |
| 91 | } { |
| 92 | t.Run(name, func(t *testing.T) { |
| 93 | root := withHostEnvRoot(t) |
| 94 | spoil(t, root) |
| 95 | err := writeHostEnv(root, []byte("CARLOS_REGION=ie\n")) |
| 96 | if err == nil || !strings.Contains(err.Error(), "is not a directory only root can write") { |
| 97 | t.Fatalf("%v", err) |
| 98 | } |
| 99 | if got := read(root); got != "" { |
| 100 | t.Fatalf("wrote %q", got) |
| 101 | } |
| 102 | }) |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | // safeDir is a directory that passes every check but the one under test: |
| 107 | // this user's, 0755 whatever the umask, so a symlink to it is refused only |
| 108 | // for being a symlink. |
| 109 | func safeDir(t *testing.T) string { |
| 110 | t.Helper() |
| 111 | dir := t.TempDir() |
| 112 | if err := os.Chmod(dir, 0o755); err != nil { |
| 113 | t.Fatal(err) |
| 114 | } |
| 115 | return dir |
| 116 | } |
| 117 | |
amadan