sandbox/vfs: add doc comments

Signed-off-by: Ophestra <cat@gensokyo.uk>

sandbox/vfs/unfold_test.go

@@ -0,0 +1,93 @@
+package vfs_test
+
+import (
+	"errors"
+	"reflect"
+	"slices"
+	"strings"
+	"syscall"
+	"testing"
+
+	"git.gensokyo.uk/security/fortify/sandbox/vfs"
+)
+
+func TestUnfold(t *testing.T) {
+	testCases := []struct {
+		name    string
+		sample  string
+		target  string
+		wantErr error
+
+		want         *vfs.MountInfoNode
+		wantCollectF func(n *vfs.MountInfoNode) []*vfs.MountInfoNode
+		wantCollectN []string
+	}{
+		{
+			"no match",
+			sampleMountinfoBase,
+			"/mnt",
+			syscall.ESTALE, nil, nil, nil,
+		},
+		{
+			"cover",
+			`33 1 0:33 / / rw,relatime shared:1 - tmpfs impure rw,size=16777216k,mode=755
+37 33 0:32 / /proc rw,nosuid,nodev,noexec,relatime shared:41 - proc proc rw
+551 33 0:121 / /mnt rw,relatime shared:666 - tmpfs tmpfs rw
+595 551 0:123 / /mnt rw,relatime shared:990 - tmpfs tmpfs rw
+611 595 0:142 / /mnt/etc rw,relatime shared:1112 - tmpfs tmpfs rw
+625 644 0:142 /passwd /mnt/etc/passwd rw,relatime shared:1112 - tmpfs tmpfs rw
+641 625 0:33 /etc/passwd /mnt/etc/passwd rw,relatime shared:1 - tmpfs impure rw,size=16777216k,mode=755
+644 611 0:33 /etc/passwd /mnt/etc/passwd rw,relatime shared:1 - tmpfs impure rw,size=16777216k,mode=755
+`, "/mnt", nil,
+			mn(595, 551, 0, 123, "/", "/mnt", "rw,relatime", o("shared:990"), "tmpfs", "tmpfs", "rw", false,
+				mn(611, 595, 0, 142, "/", "/mnt/etc", "rw,relatime", o("shared:1112"), "tmpfs", "tmpfs", "rw", false,
+					mn(644, 611, 0, 33, "/etc/passwd", "/mnt/etc/passwd", "rw,relatime", o("shared:1"), "tmpfs", "impure", "rw,size=16777216k,mode=755", true,
+						mn(625, 644, 0, 142, "/passwd", "/mnt/etc/passwd", "rw,relatime", o("shared:1112"), "tmpfs", "tmpfs", "rw", true,
+							mn(641, 625, 0, 33, "/etc/passwd", "/mnt/etc/passwd", "rw,relatime", o("shared:1"), "tmpfs", "impure", "rw,size=16777216k,mode=755", false,
+								nil, nil), nil), nil), nil), nil), func(n *vfs.MountInfoNode) []*vfs.MountInfoNode {
+				return []*vfs.MountInfoNode{n, n.FirstChild, n.FirstChild.FirstChild.FirstChild.FirstChild}
+			}, []string{"/mnt", "/mnt/etc", "/mnt/etc/passwd"},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			d := vfs.NewMountInfoDecoder(strings.NewReader(tc.sample))
+			got, err := d.Unfold(tc.target)
+
+			if !errors.Is(err, tc.wantErr) {
+				t.Errorf("Unfold: error = %v, wantErr %v",
+					err, tc.wantErr)
+			}
+
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("Unfold:\ngot  %s\nwant %s",
+					mustMarshal(got), mustMarshal(tc.want))
+			}
+
+			if err == nil && tc.wantCollectF != nil {
+				t.Run("collective", func(t *testing.T) {
+					wantCollect := tc.wantCollectF(got)
+					gotCollect := slices.Collect(got.Collective())
+					if !reflect.DeepEqual(gotCollect, wantCollect) {
+						t.Errorf("Collective: \ngot  %#v\nwant %#v",
+							gotCollect, wantCollect)
+					}
+					t.Run("target", func(t *testing.T) {
+						gotCollectN := slices.Collect[string](func(yield func(v string) bool) {
+							for _, cur := range gotCollect {
+								if !yield(cur.Clean) {
+									return
+								}
+							}
+						})
+						if !reflect.DeepEqual(gotCollectN, tc.wantCollectN) {
+							t.Errorf("Collective: got %q, want %q",
+								gotCollectN, tc.wantCollectN)
+						}
+					})
+				})
+			}
+		})
+	}
+}