| 1 | //go:build linux && rootrunner |
| 2 | |
| 3 | package host |
| 4 | |
| 5 | import ( |
| 6 | "errors" |
| 7 | "maps" |
| 8 | "os" |
| 9 | "path/filepath" |
| 10 | "slices" |
| 11 | "syscall" |
| 12 | "testing" |
| 13 | |
| 14 | "golang.org/x/sys/unix" |
| 15 | ) |
| 16 | |
| 17 | // TestRootFloorDirsUntrustedAncestry is fix round 2's witness as real root, |
| 18 | // through production's prepareRootFloorDirs (the walk from /, owner root): |
| 19 | // the floor repair checks every directory from / to guard/ before it makes |
| 20 | // or changes anything. An ancestor symlink with the floor directory missing |
| 21 | // behind it, and an ancestor owned by someone else holding a root-owned |
| 22 | // floor directory (or none), each refuse with both trees as they were. A |
| 23 | // floor directory of another owner under a trusted path refuses too. A |
| 24 | // trusted path under umask 077 is repaired to 0755 root:root. |
| 25 | func TestRootFloorDirsUntrustedAncestry(t *testing.T) { |
| 26 | if os.Geteuid() != 0 { |
| 27 | t.Fatal("designated runner must execute as root") |
| 28 | } |
| 29 | const nobody = 65534 |
| 30 | mkopt := func(t *testing.T) (string, string) { |
| 31 | t.Helper() |
| 32 | scratch := generationRootRunnerDir(t) |
| 33 | opt := filepath.Join(scratch, "opt") |
| 34 | for _, dir := range []string{opt, filepath.Join(opt, "system"), systemGuardDir(opt)} { |
| 35 | if err := os.Mkdir(dir, 0o755); err != nil { |
| 36 | t.Fatal(err) |
| 37 | } |
| 38 | if err := os.Chmod(dir, 0o755); err != nil { |
| 39 | t.Fatal(err) |
| 40 | } |
| 41 | } |
| 42 | return scratch, opt |
| 43 | } |
| 44 | mkdir := func(t *testing.T, dir string, mode os.FileMode, uid int) { |
| 45 | t.Helper() |
| 46 | if err := os.Mkdir(dir, mode); err != nil { |
| 47 | t.Fatal(err) |
| 48 | } |
| 49 | if err := os.Chmod(dir, mode); err != nil { |
| 50 | t.Fatal(err) |
| 51 | } |
| 52 | if err := os.Lchown(dir, uid, uid); err != nil { |
| 53 | t.Fatal(err) |
| 54 | } |
| 55 | } |
| 56 | for name, c := range map[string]struct { |
| 57 | setup func(t *testing.T, scratch, opt string) []string // trees outside opt that must not change |
| 58 | want []error |
| 59 | }{ |
| 60 | "symlinked guard, moves missing": {setup: func(t *testing.T, scratch, opt string) []string { |
| 61 | target := filepath.Join(scratch, "realguard") |
| 62 | mkdir(t, target, 0o755, 0) |
| 63 | if err := os.Remove(systemGuardDir(opt)); err != nil { |
| 64 | t.Fatal(err) |
| 65 | } |
| 66 | if err := os.Symlink(target, systemGuardDir(opt)); err != nil { |
| 67 | t.Fatal(err) |
| 68 | } |
| 69 | return []string{target} |
| 70 | }, want: []error{unix.ELOOP, unix.ENOTDIR}}, |
| 71 | "nobody's system, root's moves 0700": {setup: func(t *testing.T, scratch, opt string) []string { |
| 72 | mkdir(t, rootFloorDir(opt), 0o700, 0) |
| 73 | if err := os.Lchown(filepath.Join(opt, "system"), nobody, nobody); err != nil { |
| 74 | t.Fatal(err) |
| 75 | } |
| 76 | return nil |
| 77 | }, want: []error{os.ErrPermission}}, |
| 78 | "nobody's guard, moves missing": {setup: func(t *testing.T, scratch, opt string) []string { |
| 79 | if err := os.Lchown(systemGuardDir(opt), nobody, nobody); err != nil { |
| 80 | t.Fatal(err) |
| 81 | } |
| 82 | return nil |
| 83 | }, want: []error{os.ErrPermission}}, |
| 84 | "nobody's moves 0700": {setup: func(t *testing.T, scratch, opt string) []string { |
| 85 | mkdir(t, rootFloorDir(opt), 0o700, nobody) |
| 86 | return nil |
| 87 | }, want: []error{os.ErrPermission}}, |
| 88 | } { |
| 89 | t.Run(name, func(t *testing.T) { |
| 90 | scratch, opt := mkopt(t) |
| 91 | roots := append([]string{opt}, c.setup(t, scratch, opt)...) |
| 92 | before := floorTree(t, roots...) |
| 93 | err := prepareRootFloorDirs(opt) |
| 94 | if !slices.ContainsFunc(c.want, func(w error) bool { return errors.Is(err, w) }) { |
| 95 | t.Fatalf("prepareRootFloorDirs = %v, want a refusal with one of %v", err, c.want) |
| 96 | } |
| 97 | if after := floorTree(t, roots...); !maps.Equal(before, after) { |
| 98 | t.Fatalf("the refused repair changed the tree:\nbefore %v\nafter %v", before, after) |
| 99 | } |
| 100 | for _, root := range roots[1:] { |
| 101 | if _, err := os.Lstat(filepath.Join(root, "moves")); !errors.Is(err, os.ErrNotExist) { |
| 102 | t.Fatal("moves made through the symlink", err) |
| 103 | } |
| 104 | } |
| 105 | t.Logf("refused with both trees unchanged: %v", err) |
| 106 | }) |
| 107 | } |
| 108 | |
| 109 | // The trusted path, guard/moves left 0700 and guard/seeds missing, under |
| 110 | // the window shell's umask 077: both come out 0755 root:root, and a |
| 111 | // second run changes nothing. |
| 112 | t.Run("trusted, umask 077", func(t *testing.T) { |
| 113 | _, opt := mkopt(t) |
| 114 | mkdir(t, rootFloorDir(opt), 0o700, 0) |
| 115 | old := syscall.Umask(0o077) |
| 116 | err := prepareRootFloorDirs(opt) |
| 117 | syscall.Umask(old) |
| 118 | if err != nil { |
| 119 | t.Fatal(err) |
| 120 | } |
| 121 | for _, dir := range []string{rootFloorDir(opt), rootSeedsFloorDir(opt)} { |
| 122 | st, err := os.Lstat(dir) |
| 123 | if err != nil || !st.IsDir() || st.Mode().Perm() != 0o755 || st.Sys().(*syscall.Stat_t).Uid != 0 || st.Sys().(*syscall.Stat_t).Gid != 0 { |
| 124 | t.Fatalf("%s is not a 0755 root:root directory: %v %v", dir, st, err) |
| 125 | } |
| 126 | } |
| 127 | before := floorTree(t, opt) |
| 128 | if err := prepareRootFloorDirs(opt); err != nil { |
| 129 | t.Fatal("second run", err) |
| 130 | } |
| 131 | if after := floorTree(t, opt); !maps.Equal(before, after) { |
| 132 | t.Fatalf("the second run changed the tree:\nbefore %v\nafter %v", before, after) |
| 133 | } |
| 134 | }) |
| 135 | } |
| 136 | |
amadan