| 1 | //go:build linux |
| 2 | |
| 3 | package stopevidence |
| 4 | |
| 5 | import ( |
| 6 | "errors" |
| 7 | "os" |
| 8 | "path/filepath" |
| 9 | "slices" |
| 10 | "strconv" |
| 11 | "syscall" |
| 12 | "testing" |
| 13 | ) |
| 14 | |
| 15 | // holdersFixture is a fake /proc: pid 20 (the agent) holds the database |
| 16 | // at fd 7 and its WAL at fd 8 in its leader table, and an unrelated file |
| 17 | // at fd 9; pid 30 holds nothing watched. Each pid has a stat file whose |
| 18 | // field 22 is "start-<pid>". |
| 19 | func holdersFixture(t *testing.T) (root, db string) { |
| 20 | t.Helper() |
| 21 | root, dir := t.TempDir(), t.TempDir() |
| 22 | db = filepath.Join(dir, "data.db") |
| 23 | for _, name := range []string{db, db + "-wal", filepath.Join(dir, "other")} { |
| 24 | if err := os.WriteFile(name, nil, 0o600); err != nil { |
| 25 | t.Fatal(err) |
| 26 | } |
| 27 | } |
| 28 | link := func(pid, tid, fd int, target string) { |
| 29 | fdDir := filepath.Join(root, strconv.Itoa(pid), "task", strconv.Itoa(tid), "fd") |
| 30 | if err := os.MkdirAll(fdDir, 0o700); err != nil { |
| 31 | t.Fatal(err) |
| 32 | } |
| 33 | if err := os.Symlink(target, filepath.Join(fdDir, strconv.Itoa(fd))); err != nil { |
| 34 | t.Fatal(err) |
| 35 | } |
| 36 | } |
| 37 | link(20, 20, 7, db) |
| 38 | link(20, 20, 8, db+"-wal") |
| 39 | link(20, 20, 9, filepath.Join(dir, "other")) |
| 40 | link(30, 30, 3, filepath.Join(dir, "other")) |
| 41 | for _, pid := range []int{20, 30} { |
| 42 | writeStat(t, root, pid, "start-"+strconv.Itoa(pid)) |
| 43 | } |
| 44 | return root, db |
| 45 | } |
| 46 | |
| 47 | func writeStat(t *testing.T, root string, pid int, start string) { |
| 48 | t.Helper() |
| 49 | fields := "S" |
| 50 | for i := 4; i <= 21; i++ { |
| 51 | fields += " 0" |
| 52 | } |
| 53 | body := strconv.Itoa(pid) + " (carlos) " + fields + " " + start + " 0 0\n" |
| 54 | if err := os.WriteFile(filepath.Join(root, strconv.Itoa(pid), "stat"), []byte(body), 0o600); err != nil { |
| 55 | t.Fatal(err) |
| 56 | } |
| 57 | } |
| 58 | |
| 59 | func identity(t *testing.T, path string) (uint64, uint64) { |
| 60 | t.Helper() |
| 61 | fi, err := os.Stat(path) |
| 62 | if err != nil { |
| 63 | t.Fatal(err) |
| 64 | } |
| 65 | st := fi.Sys().(*syscall.Stat_t) |
| 66 | return uint64(st.Dev), st.Ino |
| 67 | } |
| 68 | |
| 69 | func dbPathsOf(db string) []string { return []string{db, db + "-wal", db + "-shm"} } |
| 70 | |
| 71 | func TestHoldersReportsEveryDescriptorWithItsIdentity(t *testing.T) { |
| 72 | root, db := holdersFixture(t) |
| 73 | got, err := Holders(t.Context(), root, dbPathsOf(db), nil) |
| 74 | if err != nil { |
| 75 | t.Fatal(err) |
| 76 | } |
| 77 | dev, ino := identity(t, db) |
| 78 | wdev, wino := identity(t, db+"-wal") |
| 79 | want := []Descriptor{{PID: 20, TID: 20, FD: 7, Device: dev, Inode: ino}, {PID: 20, TID: 20, FD: 8, Device: wdev, Inode: wino}} |
| 80 | if !slices.Equal(got, want) { |
| 81 | t.Fatalf("got %+v want %+v", got, want) |
| 82 | } |
| 83 | // A file named only by its identity (the launch journal's record) is |
| 84 | // found under whatever name it was opened by. |
| 85 | byID, err := Holders(t.Context(), root, nil, []FileIdentity{{Device: dev, Inode: ino}}) |
| 86 | if err != nil || !slices.Equal(byID, want[:1]) { |
| 87 | t.Fatalf("by identity: %+v %v", byID, err) |
| 88 | } |
| 89 | if _, err := Holders(t.Context(), root, nil, nil); !errors.Is(err, ErrInvalidInput) { |
| 90 | t.Fatalf("nothing watched: %v", err) |
| 91 | } |
| 92 | if _, err := Holders(t.Context(), filepath.Join(root, "missing"), dbPathsOf(db), nil); !errors.Is(err, ErrIncomplete) { |
| 93 | t.Fatalf("unreadable root: %v", err) |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | func TestOwnDescriptorsReadsOnlyTheLeaderTable(t *testing.T) { |
| 98 | root, db := holdersFixture(t) |
| 99 | // Another process's table is never read: pid 30 has no stat for this |
| 100 | // call to fail on, and its descriptors never appear. |
| 101 | got, err := OwnDescriptors(t.Context(), root, 20, dbPathsOf(db)) |
| 102 | if err != nil { |
| 103 | t.Fatal(err) |
| 104 | } |
| 105 | dev, ino := identity(t, db) |
| 106 | wdev, wino := identity(t, db+"-wal") |
| 107 | want := []DescriptorHint{{FD: 7, Device: dev, Inode: ino}, {FD: 8, Device: wdev, Inode: wino}} |
| 108 | if !slices.Equal(got, want) { |
| 109 | t.Fatalf("got %+v want %+v", got, want) |
| 110 | } |
| 111 | if err := os.Chmod(filepath.Join(root, "20", "task", "20", "fd"), 0); err != nil { |
| 112 | t.Fatal(err) |
| 113 | } |
| 114 | defer os.Chmod(filepath.Join(root, "20", "task", "20", "fd"), 0o700) |
| 115 | if os.Geteuid() != 0 { |
| 116 | if _, err := OwnDescriptors(t.Context(), root, 20, dbPathsOf(db)); !errors.Is(err, ErrIncomplete) { |
| 117 | t.Fatalf("an unreadable table is not an empty one: %v", err) |
| 118 | } |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | func TestReplicatorOnlyIsANarrowingHint(t *testing.T) { |
| 123 | root, db := holdersFixture(t) |
| 124 | dev, ino := identity(t, db) |
| 125 | wdev, wino := identity(t, db+"-wal") |
| 126 | agent := Agent{PID: 20, Start: "start-20"} |
| 127 | hints := []DescriptorHint{{FD: 7, Device: dev, Inode: ino}, {FD: 8, Device: wdev, Inode: wino}} |
| 128 | held := func(t *testing.T) []Descriptor { |
| 129 | got, err := Holders(t.Context(), root, dbPathsOf(db), nil) |
| 130 | if err != nil { |
| 131 | t.Fatal(err) |
| 132 | } |
| 133 | return got |
| 134 | } |
| 135 | t.Run("every holder is a hinted replicator descriptor", func(t *testing.T) { |
| 136 | got, err := ReplicatorOnly(t.Context(), root, held(t), agent, hints) |
| 137 | if err != nil || len(got) != 2 { |
| 138 | t.Fatalf("%+v %v", got, err) |
| 139 | } |
| 140 | }) |
| 141 | t.Run("an unhinted descriptor in the agent itself", func(t *testing.T) { |
| 142 | if _, err := ReplicatorOnly(t.Context(), root, held(t), agent, hints[:1]); !errors.Is(err, ErrForeignHolder) { |
| 143 | t.Fatalf("got %v", err) |
| 144 | } |
| 145 | }) |
| 146 | t.Run("a hint naming another file at the same number", func(t *testing.T) { |
| 147 | wrong := []DescriptorHint{{FD: 7, Device: wdev, Inode: wino}, hints[1]} |
| 148 | if _, err := ReplicatorOnly(t.Context(), root, held(t), agent, wrong); !errors.Is(err, ErrForeignHolder) { |
| 149 | t.Fatalf("got %v", err) |
| 150 | } |
| 151 | }) |
| 152 | t.Run("a hint never widens to another process", func(t *testing.T) { |
| 153 | other := filepath.Join(root, "30", "task", "30", "fd", "4") |
| 154 | if err := os.Symlink(db, other); err != nil { |
| 155 | t.Fatal(err) |
| 156 | } |
| 157 | defer os.Remove(other) |
| 158 | extra := append(slices.Clone(hints), DescriptorHint{FD: 4, Device: dev, Inode: ino}) |
| 159 | if _, err := ReplicatorOnly(t.Context(), root, held(t), agent, extra); !errors.Is(err, ErrForeignHolder) { |
| 160 | t.Fatalf("got %v", err) |
| 161 | } |
| 162 | }) |
| 163 | t.Run("a hinted descriptor root does not see is ignored", func(t *testing.T) { |
| 164 | extra := append(slices.Clone(hints), DescriptorHint{FD: 99, Device: dev, Inode: ino}) |
| 165 | got, err := ReplicatorOnly(t.Context(), root, held(t), agent, extra) |
| 166 | if err != nil || len(got) != 2 { |
| 167 | t.Fatalf("%+v %v", got, err) |
| 168 | } |
| 169 | }) |
| 170 | t.Run("the agent's pid now names another process", func(t *testing.T) { |
| 171 | writeStat(t, root, 20, "start-reused") |
| 172 | defer writeStat(t, root, 20, "start-20") |
| 173 | if _, err := ReplicatorOnly(t.Context(), root, held(t), agent, hints); !errors.Is(err, ErrForeignHolder) { |
| 174 | t.Fatalf("got %v", err) |
| 175 | } |
| 176 | }) |
| 177 | t.Run("a name-only match has no identity to exempt", func(t *testing.T) { |
| 178 | in := []Descriptor{{PID: 20, TID: 20, FD: 7}} |
| 179 | if _, err := ReplicatorOnly(t.Context(), root, in, agent, []DescriptorHint{{FD: 7}}); !errors.Is(err, ErrForeignHolder) { |
| 180 | t.Fatalf("got %v", err) |
| 181 | } |
| 182 | }) |
| 183 | t.Run("a thread's table", func(t *testing.T) { |
| 184 | thread := filepath.Join(root, "20", "task", "21", "fd") |
| 185 | if err := os.MkdirAll(thread, 0o700); err != nil { |
| 186 | t.Fatal(err) |
| 187 | } |
| 188 | defer os.RemoveAll(filepath.Join(root, "20", "task", "21")) |
| 189 | if err := os.Symlink(db, filepath.Join(thread, "7")); err != nil { |
| 190 | t.Fatal(err) |
| 191 | } |
| 192 | prior := sameFDTable |
| 193 | defer func() { sameFDTable = prior }() |
| 194 | for _, tc := range []struct { |
| 195 | name string |
| 196 | shared bool |
| 197 | err error |
| 198 | want error |
| 199 | }{ |
| 200 | {"shares the leader's", true, nil, nil}, |
| 201 | {"unshared", false, nil, ErrForeignHolder}, |
| 202 | {"cannot be compared", false, syscall.EPERM, ErrIncomplete}, |
| 203 | } { |
| 204 | t.Run(tc.name, func(t *testing.T) { |
| 205 | sameFDTable = func(string, int, int) (bool, error) { return tc.shared, tc.err } |
| 206 | _, err := ReplicatorOnly(t.Context(), root, held(t), agent, hints) |
| 207 | if !errors.Is(err, tc.want) { |
| 208 | t.Fatalf("got %v want %v", err, tc.want) |
| 209 | } |
| 210 | }) |
| 211 | } |
| 212 | }) |
| 213 | t.Run("invalid agent", func(t *testing.T) { |
| 214 | if _, err := ReplicatorOnly(t.Context(), root, held(t), Agent{}, hints); !errors.Is(err, ErrInvalidInput) { |
| 215 | t.Fatalf("got %v", err) |
| 216 | } |
| 217 | }) |
| 218 | t.Run("nothing held needs no agent proof", func(t *testing.T) { |
| 219 | got, err := ReplicatorOnly(t.Context(), root, nil, Agent{PID: 77, Start: "gone"}, nil) |
| 220 | if err != nil || len(got) != 0 { |
| 221 | t.Fatalf("%+v %v", got, err) |
| 222 | } |
| 223 | }) |
| 224 | } |
| 225 | |
| 226 | // FDHolders keeps its result and strictness after the refactor onto |
| 227 | // Holders: the deleted-name match still counts. |
| 228 | func TestFDHoldersStillMatchesNamesAndIdentities(t *testing.T) { |
| 229 | root, db := procFixture(t) |
| 230 | got, err := FDHolders(root, dbPathsOf(db)) |
| 231 | if err != nil || !slices.Equal(got, []int{3, 20}) { |
| 232 | t.Fatalf("%v %v", got, err) |
| 233 | } |
| 234 | } |
| 235 | |
amadan