| 1 | //go:build linux |
| 2 | |
| 3 | package host |
| 4 | |
| 5 | import ( |
| 6 | "context" |
| 7 | "crypto/sha256" |
| 8 | "encoding/hex" |
| 9 | "errors" |
| 10 | "fmt" |
| 11 | "os" |
| 12 | "path/filepath" |
| 13 | "strings" |
| 14 | "testing" |
| 15 | "time" |
| 16 | ) |
| 17 | |
| 18 | // The generation census that carlos-system-recover runs, on the two |
| 19 | // refusals the harness box hit: a non-root service still running the |
| 20 | // /opt/carlos/carlos an apply renamed over ("(deleted)"), and short-lived |
| 21 | // tasks the service lookup refused with a bare "permission denied". These |
| 22 | // drive the production service lookup (generationServiceEnv.reader) over a |
| 23 | // fake /proc, replacing only systemctl, the unit files' ownership check, |
| 24 | // the signed-binary proof and the owner uid a non-root test cannot have. |
| 25 | |
| 26 | type deletedExeFixture struct { |
| 27 | generationProcFixture |
| 28 | opt, image string |
| 29 | env generationServiceEnv |
| 30 | current string // digest the env proves for <opt>/carlos |
| 31 | prev string // and for <opt>/carlos.prev; "" is no carlos.prev |
| 32 | execStart string |
| 33 | mainPID string |
| 34 | unit string |
| 35 | tt *testing.T |
| 36 | // deletedName is the exe link's base name; "" is "carlos (deleted)". |
| 37 | deletedName string |
| 38 | // imageFile is the open descriptor of the task's current image. |
| 39 | imageFile *os.File |
| 40 | } |
| 41 | |
| 42 | func (f *deletedExeFixture) t() *testing.T { return f.tt } |
| 43 | |
| 44 | const deletedExeBody = "carlos router build, now renamed over" |
| 45 | |
| 46 | func deletedExe(t *testing.T) *deletedExeFixture { |
| 47 | t.Helper() |
| 48 | g := generationProc(t) |
| 49 | f := &deletedExeFixture{generationProcFixture: g, opt: filepath.Join(t.TempDir(), "opt", "carlos"), mainPID: "41", unit: "carlos-relay.service"} |
| 50 | if err := os.MkdirAll(f.opt, 0o755); err != nil { |
| 51 | t.Fatal(err) |
| 52 | } |
| 53 | f.execStart = "{ path=" + f.opt + "/carlos ; argv[]=" + f.opt + "/carlos relay ; ignore_errors=no ; start_time=[n/a] ; stop_time=[n/a] ; pid=41 ; code=(null) ; status=0/0 }" |
| 54 | generationWrite(t, f.task+"/status", "Tgid:\t41\nUid:\t1001\t1001\t1001\t1001\nKthread:\t0\n") |
| 55 | group := "/system.slice/carlos-relay.service" |
| 56 | generationWrite(t, f.task+"/cgroup", "0::"+group+"\n") |
| 57 | generationWrite(t, f.proc+"/41/cgroup", "0::"+group+"\n") |
| 58 | // The image the task runs: open, then unlinked, as the apply's rename |
| 59 | // leaves the edge's. The exe link reads "<opt>/carlos (deleted)" and |
| 60 | // opens that image, as /proc/<pid>/exe does. |
| 61 | f.image = filepath.Join(t.TempDir(), "image") |
| 62 | f.writeImage(t, deletedExeBody, 0o755, true) |
| 63 | sum := sha256.Sum256([]byte(deletedExeBody)) |
| 64 | f.current = "not-this-build" |
| 65 | f.prev = hex.EncodeToString(sum[:]) |
| 66 | f.env = generationServiceEnv{proc: f.proc, opt: f.opt, owner: uint32(os.Getuid()), |
| 67 | show: func(_ context.Context, unit string) (map[string]string, error) { |
| 68 | if unit != f.unit { |
| 69 | return nil, fmt.Errorf("systemctl show %s: no such unit", unit) |
| 70 | } |
| 71 | return map[string]string{"ControlGroup": group, "MainPID": f.mainPID, "ExecStart": f.execStart, "FragmentPath": "/etc/systemd/system/" + unit}, nil |
| 72 | }, |
| 73 | trust: func(string) error { return nil }, |
| 74 | binary: func(_ context.Context, opt, path string) (rootFloorBinary, error) { |
| 75 | switch path { |
| 76 | case filepath.Join(opt, "carlos"): |
| 77 | return rootFloorBinary{Digest: f.current}, nil |
| 78 | case filepath.Join(opt, "carlos.prev"): |
| 79 | if f.prev == "" { |
| 80 | return rootFloorBinary{}, os.ErrNotExist |
| 81 | } |
| 82 | return rootFloorBinary{Digest: f.prev}, nil |
| 83 | } |
| 84 | return rootFloorBinary{}, os.ErrPermission |
| 85 | }, |
| 86 | } |
| 87 | return f |
| 88 | } |
| 89 | |
| 90 | // writeImage replaces the task's image with body at mode, unlinked or not. |
| 91 | func (f *deletedExeFixture) writeImage(t *testing.T, body string, mode os.FileMode, unlink bool) { |
| 92 | t.Helper() |
| 93 | path := f.image + fmt.Sprint(time.Now().UnixNano()) |
| 94 | if err := os.WriteFile(path, []byte(body), 0o600); err != nil { |
| 95 | t.Fatal(err) |
| 96 | } |
| 97 | if err := os.Chmod(path, mode); err != nil { |
| 98 | t.Fatal(err) |
| 99 | } |
| 100 | img, err := os.Open(path) |
| 101 | if err != nil { |
| 102 | t.Fatal(err) |
| 103 | } |
| 104 | t.Cleanup(func() { img.Close() }) |
| 105 | f.imageFile = img |
| 106 | if unlink { |
| 107 | if err := os.Remove(path); err != nil { |
| 108 | t.Fatal(err) |
| 109 | } |
| 110 | } |
| 111 | name := f.deletedName |
| 112 | if name == "" { |
| 113 | name = "carlos (deleted)" |
| 114 | } |
| 115 | deleted := filepath.Join(f.opt, name) |
| 116 | os.Remove(deleted) |
| 117 | generationLink(t, fmt.Sprintf("/proc/%d/fd/%d", os.Getpid(), img.Fd()), deleted) |
| 118 | os.Remove(f.task + "/exe") |
| 119 | generationLink(t, deleted, f.task+"/exe") |
| 120 | } |
| 121 | |
| 122 | // kernelCensus is one census pass through the production lookup, as |
| 123 | // productionGenerationKernelCensus wires it: classify and recheck. |
| 124 | func (f *deletedExeFixture) kernelCensus(ctx context.Context) error { |
| 125 | service, recheck := f.env.reader(ctx) |
| 126 | _, err := (generationKernel{proc: f.proc, service: service, recheck: recheck}).absent(ctx, f.reservation) |
| 127 | return err |
| 128 | } |
| 129 | |
| 130 | func (f *deletedExeFixture) census(t *testing.T) error { |
| 131 | t.Helper() |
| 132 | return f.kernelCensus(t.Context()) |
| 133 | } |
| 134 | |
| 135 | func TestRecoverCensusAcceptsADeletedExeOfTheCurrentOrPreviousBuild(t *testing.T) { |
| 136 | for _, which := range []string{"previous", "current", "current-no-prev"} { |
| 137 | t.Run(which, func(t *testing.T) { |
| 138 | f := deletedExe(t) |
| 139 | switch which { |
| 140 | case "current": |
| 141 | f.current, f.prev = f.prev, "other-build" |
| 142 | case "current-no-prev": |
| 143 | f.current, f.prev = f.prev, "" |
| 144 | } |
| 145 | if err := f.census(t); err != nil { |
| 146 | t.Fatalf("census refused a deleted exe of the %s signed build: %v", which, err) |
| 147 | } |
| 148 | }) |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | func TestRecoverCensusAcceptsTheEdgesDeletedExeInSupervise(t *testing.T) { |
| 153 | // The harness's b2 task: carlos-edge.service's main process, in its |
| 154 | // supervise/ group, still running the pre-apply image, with and |
| 155 | // without the guard drop-in (whose ExecStart is the guard and whose |
| 156 | // selected program is <opt>/carlos). |
| 157 | for _, guarded := range []bool{false, true} { |
| 158 | t.Run(map[bool]string{false: "unguarded", true: "guarded"}[guarded], func(t *testing.T) { |
| 159 | f := deletedExe(t) |
| 160 | f.unit = "carlos-edge.service" |
| 161 | if guarded { |
| 162 | f.execStart = "{ path=/opt/carlos/system/guard/carlos ; argv[]=/opt/carlos/system/guard/carlos system guard-exec edge ; ignore_errors=no ; start_time=[n/a] ; stop_time=[n/a] ; pid=41 ; code=(null) ; status=0/0 }" |
| 163 | binary := f.env.binary |
| 164 | f.env.binary = func(ctx context.Context, opt, path string) (rootFloorBinary, error) { |
| 165 | if path == "/opt/carlos/system/guard/carlos" { |
| 166 | return rootFloorBinary{Digest: "guard"}, nil |
| 167 | } |
| 168 | b, err := binary(ctx, opt, path) |
| 169 | b.File.Inode = 7 // the live <opt>/carlos, not the deleted image |
| 170 | return b, err |
| 171 | } |
| 172 | } |
| 173 | base := "/system.slice/carlos-edge.service" |
| 174 | generationWrite(t, f.task+"/cgroup", "0::"+base+"/supervise\n") |
| 175 | generationWrite(t, f.proc+"/41/cgroup", "0::"+base+"/supervise\n") |
| 176 | show := f.env.show |
| 177 | f.env.show = func(ctx context.Context, unit string) (map[string]string, error) { |
| 178 | props, err := show(ctx, unit) |
| 179 | if err == nil { |
| 180 | props["ControlGroup"] = base |
| 181 | } |
| 182 | return props, err |
| 183 | } |
| 184 | if err := f.census(t); err != nil { |
| 185 | t.Fatalf("census refused the edge's deleted signed image: %v", err) |
| 186 | } |
| 187 | // The same edge running some other deleted image still refuses. |
| 188 | f.writeImage(t, "an image no identity signs", 0o755, true) |
| 189 | if err := f.census(t); err == nil { |
| 190 | t.Fatal("census accepted an unsigned deleted image in the edge") |
| 191 | } |
| 192 | }) |
| 193 | } |
| 194 | } |
| 195 | |
| 196 | func TestRecoverCensusRefusesOtherDeletedExes(t *testing.T) { |
| 197 | for _, attack := range []string{"unsigned", "no-proof", "linked", "group-writable", "not-router-binary", "other-program", "deleted-helper", "other-path"} { |
| 198 | t.Run(attack, func(t *testing.T) { |
| 199 | f := deletedExe(t) |
| 200 | switch attack { |
| 201 | case "unsigned": |
| 202 | f.writeImage(t, "some other build", 0o755, true) |
| 203 | case "no-proof": |
| 204 | f.env.binary = func(context.Context, string, string) (rootFloorBinary, error) { |
| 205 | return rootFloorBinary{}, errRootFloorHistory |
| 206 | } |
| 207 | case "linked": |
| 208 | f.writeImage(t, deletedExeBody, 0o755, false) |
| 209 | case "group-writable": |
| 210 | f.writeImage(t, deletedExeBody, 0o775, true) |
| 211 | case "not-router-binary": |
| 212 | // The unit runs another program: a deleted <opt>/carlos is |
| 213 | // not what it selects. |
| 214 | f.execStart = strings.ReplaceAll(f.execStart, f.opt+"/carlos", f.opt+"/helper") |
| 215 | case "other-program": |
| 216 | f.execStart = strings.ReplaceAll(f.execStart, f.opt+"/carlos", "/usr/bin/carlos") |
| 217 | case "other-path": |
| 218 | // The unit selects <opt>/carlos, but the task's image was |
| 219 | // somewhere else when it was deleted. |
| 220 | f.deletedName = "carlos-copy (deleted)" |
| 221 | f.writeImage(t, deletedExeBody, 0o755, true) |
| 222 | case "deleted-helper": |
| 223 | // The unit's own program, deleted, with a signed router |
| 224 | // build's bytes: only <opt>/carlos is ever accepted. |
| 225 | f.execStart = strings.ReplaceAll(f.execStart, f.opt+"/carlos", f.opt+"/helper") |
| 226 | f.deletedName = "helper (deleted)" |
| 227 | f.writeImage(t, deletedExeBody, 0o755, true) |
| 228 | } |
| 229 | err := f.census(t) |
| 230 | if err == nil { |
| 231 | t.Fatalf("%s: census accepted the deleted exe", attack) |
| 232 | } |
| 233 | if !errors.Is(err, os.ErrPermission) && attack != "no-proof" { |
| 234 | t.Fatalf("%s: refusal %v is not a permission refusal", attack, err) |
| 235 | } |
| 236 | if !strings.Contains(err.Error(), "deleted exe check refused") { |
| 237 | t.Fatalf("%s: refusal %q does not name the deleted exe check", attack, err) |
| 238 | } |
| 239 | }) |
| 240 | } |
| 241 | } |
| 242 | |
| 243 | func TestRecoverCensusRefusesADeletedExeNotOwnedByRoot(t *testing.T) { |
| 244 | if os.Getuid() == 0 { |
| 245 | t.Skip("the fixture's image is root-owned when run as root") |
| 246 | } |
| 247 | f := deletedExe(t) |
| 248 | f.env.owner = 0 // production: the image must be root's |
| 249 | if err := f.census(t); err == nil || !strings.Contains(err.Error(), "not an unlinked root-owned file") { |
| 250 | t.Fatalf("census = %v, want a refusal of a non-root-owned image", err) |
| 251 | } |
| 252 | } |
| 253 | |
| 254 | func TestRecoverCensusStillChecksReferencesOfAnAcceptedDeletedExe(t *testing.T) { |
| 255 | for _, ref := range []string{"fd", "mapped", "cwd"} { |
| 256 | t.Run(ref, func(t *testing.T) { |
| 257 | f := deletedExe(t) |
| 258 | b := f.reservation.Binding |
| 259 | switch ref { |
| 260 | case "fd": |
| 261 | generationLink(t, b.Path, f.task+"/fd/3") |
| 262 | case "mapped": |
| 263 | generationWrite(t, f.task+"/maps", fmt.Sprintf("1000-2000 r-xp 0000 %x:%x %d %s\n", generationMajor(b.Executable.Device), generationMinor(b.Executable.Device), b.Executable.Inode, b.Path)) |
| 264 | case "cwd": |
| 265 | generationRelink(t, b.Tree, f.task+"/cwd") |
| 266 | } |
| 267 | if err := f.census(t); err == nil { |
| 268 | t.Fatalf("a deleted-exe task referencing a retired generation (%s) was accepted", ref) |
| 269 | } |
| 270 | }) |
| 271 | } |
| 272 | } |
| 273 | |
| 274 | func TestRecoverCensusRefusalsNameCheckUnitCgroupAndExe(t *testing.T) { |
| 275 | for _, tc := range []struct { |
| 276 | name, check, unit, group string |
| 277 | setup func(*deletedExeFixture) |
| 278 | }{ |
| 279 | {"activating", "main pid", "carlos-relay.service", "/system.slice/carlos-relay.service", func(f *deletedExeFixture) { f.mainPID = "0" }}, |
| 280 | {"session", "unit", "session-3.scope", "/user.slice/user-1000.slice/session-3.scope", func(f *deletedExeFixture) { |
| 281 | generationWrite(f.t(), f.task+"/cgroup", "0::/user.slice/user-1000.slice/session-3.scope\n") |
| 282 | }}, |
| 283 | {"live-exe", "exe", "carlos-relay.service", "/system.slice/carlos-relay.service", func(f *deletedExeFixture) { |
| 284 | // A live (not deleted) exe the lookup cannot walk to as a |
| 285 | // root-owned file under the task's root. |
| 286 | generationRelink(f.t(), f.unrelated, f.task+"/exe") |
| 287 | generationRelink(f.t(), "/", f.task+"/root") |
| 288 | }}, |
| 289 | } { |
| 290 | t.Run(tc.name, func(t *testing.T) { |
| 291 | f := deletedExe(t) |
| 292 | f.tt = t |
| 293 | tc.setup(f) |
| 294 | exe, _ := os.Readlink(f.task + "/exe") |
| 295 | err := f.census(t) |
| 296 | if err == nil { |
| 297 | t.Fatal("census accepted") |
| 298 | } |
| 299 | for _, want := range []string{"/41/task/41: service: " + tc.check, "service: " + tc.check + " check refused", "unit " + tc.unit, "cgroup " + tc.group, "exe " + exe} { |
| 300 | if !strings.Contains(err.Error(), want) { |
| 301 | t.Fatalf("refusal %q does not name %q", err, want) |
| 302 | } |
| 303 | } |
| 304 | }) |
| 305 | } |
| 306 | } |
| 307 | |
| 308 | func TestRecoverCensusRetriesATransientRefusalWithinTheWindow(t *testing.T) { |
| 309 | clock := time.Unix(0, 0) |
| 310 | var slept []time.Duration |
| 311 | now := func() time.Time { return clock } |
| 312 | sleep := func(_ context.Context, d time.Duration) error { |
| 313 | if clock.Sub(time.Unix(0, 0)) > time.Minute { |
| 314 | return errors.New("unbounded retry") // ends a run with no window |
| 315 | } |
| 316 | slept = append(slept, d) |
| 317 | clock = clock.Add(d) |
| 318 | return nil |
| 319 | } |
| 320 | |
| 321 | // A unit still activating, through the real census pass: it clears on |
| 322 | // the fourth pass. |
| 323 | f := deletedExe(t) |
| 324 | passes := 0 |
| 325 | inspect := func(ctx context.Context) (string, string, error) { |
| 326 | passes++ |
| 327 | f.mainPID = "0" |
| 328 | if passes == 4 { |
| 329 | f.mainPID = "41" |
| 330 | } |
| 331 | err := f.kernelCensus(ctx) |
| 332 | return "boot", "digest", err |
| 333 | } |
| 334 | if _, _, err := generationCensusRetryFor(t.Context(), inspect, 20*time.Second, now, sleep); err != nil { |
| 335 | t.Fatalf("a transient refusal did not clear within the window: %v", err) |
| 336 | } |
| 337 | if passes != 4 || fmt.Sprint(slept) != "[250ms 500ms 1s]" { |
| 338 | t.Fatalf("passes=%d slept=%v, want 4 passes after 250ms, 500ms, 1s", passes, slept) |
| 339 | } |
| 340 | |
| 341 | // The same refusal, persistent: refused once the next wait would end |
| 342 | // past the window, with the last pass's refusal. |
| 343 | clock, slept, passes = time.Unix(0, 0), nil, 0 |
| 344 | persistent := func(ctx context.Context) (string, string, error) { |
| 345 | passes++ |
| 346 | f.mainPID = "0" |
| 347 | err := f.kernelCensus(ctx) |
| 348 | return "", "", err |
| 349 | } |
| 350 | _, _, err := generationCensusRetryFor(t.Context(), persistent, 20*time.Second, now, sleep) |
| 351 | if err == nil || !strings.Contains(err.Error(), "main pid check refused") { |
| 352 | t.Fatalf("persistent refusal = %v", err) |
| 353 | } |
| 354 | var total time.Duration |
| 355 | for _, d := range slept { |
| 356 | total += d |
| 357 | } |
| 358 | if total > 20*time.Second || total < 15*time.Second || passes != len(slept)+1 { |
| 359 | t.Fatalf("persistent refusal: %d passes, slept %v (%s), want about 20 s then refuse", passes, slept, total) |
| 360 | } |
| 361 | } |
| 362 | |
| 363 | func TestRecoverCensusRetriesOnlyTaskLevelTransients(t *testing.T) { |
| 364 | sleep := func(context.Context, time.Duration) error { return nil } |
| 365 | for _, tc := range []struct { |
| 366 | name string |
| 367 | err error |
| 368 | retry bool |
| 369 | }{ |
| 370 | {"service", &generationTaskRefusal{task: "/proc/9/task/9", err: fmt.Errorf("service: %w", &generationServiceRefusal{check: "unit", err: os.ErrPermission})}, true}, |
| 371 | {"exited", &generationTaskRefusal{task: "/proc/9/task/9", err: os.ErrNotExist}, true}, |
| 372 | {"replaced", &generationTaskRefusal{task: "/proc/9/task/9", err: errGenerationTaskReplaced}, true}, |
| 373 | {"reference", &generationTaskRefusal{task: "/proc/9/task/9", err: fmt.Errorf("fd: %w", os.ErrPermission)}, false}, |
| 374 | {"mounts", &generationTaskRefusal{task: "/proc/9/task/9", err: fmt.Errorf("mounts: %w", os.ErrPermission)}, false}, |
| 375 | {"structural", os.ErrPermission, false}, |
| 376 | } { |
| 377 | t.Run(tc.name, func(t *testing.T) { |
| 378 | passes := 0 |
| 379 | _, _, err := generationCensusRetryFor(t.Context(), func(context.Context) (string, string, error) { |
| 380 | passes++ |
| 381 | if passes == 2 { |
| 382 | return "boot", "digest", nil |
| 383 | } |
| 384 | return "", "", tc.err |
| 385 | }, 20*time.Second, time.Now, sleep) |
| 386 | if tc.retry && (err != nil || passes != 2) { |
| 387 | t.Fatalf("transient %s: passes=%d err=%v", tc.name, passes, err) |
| 388 | } |
| 389 | if !tc.retry && (err == nil || passes != 1) { |
| 390 | t.Fatalf("%s retried: passes=%d err=%v", tc.name, passes, err) |
| 391 | } |
| 392 | }) |
| 393 | } |
| 394 | // A cancelled wait refuses with the refusal it was waiting out. |
| 395 | ctx, cancel := context.WithCancel(t.Context()) |
| 396 | refusal := &generationTaskRefusal{task: "/proc/9/task/9", err: os.ErrNotExist} |
| 397 | _, _, err := generationCensusRetryFor(ctx, func(context.Context) (string, string, error) { return "", "", refusal }, 20*time.Second, time.Now, func(context.Context, time.Duration) error { cancel(); return context.Canceled }) |
| 398 | if !errors.Is(err, refusal) { |
| 399 | t.Fatalf("cancelled wait = %v", err) |
| 400 | } |
| 401 | } |
| 402 | |
| 403 | func TestProductionGenerationCensusRefusalsAreTyped(t *testing.T) { |
| 404 | // Every refusal of the production census is a generationCensusRefusal, |
| 405 | // which is what lets a no-journal recovery defer it. As a non-root test |
| 406 | // the census refuses at its first check. |
| 407 | if os.Geteuid() == 0 { |
| 408 | t.Skip("the census does not refuse at once as root") |
| 409 | } |
| 410 | _, _, err := productionGenerationKernelCensus(t.Context()) |
| 411 | var refusal *generationCensusRefusal |
| 412 | if !errors.As(err, &refusal) || !onlyCensusRefusal(err) || !errors.Is(err, os.ErrPermission) { |
| 413 | t.Fatalf("census refusal = %#v, want a typed census refusal", err) |
| 414 | } |
| 415 | } |
| 416 | |
| 417 | // execRace runs one census pass through the production lookup with a hook |
| 418 | // around each of its rechecks: before(final) runs before the recheck and |
| 419 | // after(final) after it. The hooks stand in for the task exec'ing (the |
| 420 | // same PID, the same start time) while the census inspects it. |
| 421 | func (f *deletedExeFixture) execRace(t *testing.T, after func(final bool, call int), before func(final bool, call int)) error { |
| 422 | t.Helper() |
| 423 | classify, recheck := f.env.reader(t.Context()) |
| 424 | calls := 0 |
| 425 | hooked := func(path string, final bool) error { |
| 426 | calls++ |
| 427 | if before != nil { |
| 428 | before(final, calls) |
| 429 | } |
| 430 | err := recheck(path, final) |
| 431 | if after != nil { |
| 432 | after(final, calls) |
| 433 | } |
| 434 | return err |
| 435 | } |
| 436 | _, err := (generationKernel{proc: f.proc, service: classify, recheck: hooked}).absent(t.Context(), f.reservation) |
| 437 | return err |
| 438 | } |
| 439 | |
| 440 | func TestRecoverCensusRefusesATaskThatExecsAfterItsImageWasProven(t *testing.T) { |
| 441 | helper := func(f *deletedExeFixture) { generationRelink(t, f.unrelated, f.task+"/exe") } |
| 442 | for _, tc := range []struct { |
| 443 | name string |
| 444 | race func(f *deletedExeFixture) (after, before func(bool, int)) |
| 445 | }{ |
| 446 | // The task execs an unsigned helper between the hash and the first |
| 447 | // use of the trust. |
| 448 | {"after-classification", func(f *deletedExeFixture) (func(bool, int), func(bool, int)) { |
| 449 | return nil, func(_ bool, call int) { |
| 450 | if call == 1 { |
| 451 | helper(f) |
| 452 | } |
| 453 | } |
| 454 | }}, |
| 455 | // It execs another image that reads the same, "<opt>/carlos |
| 456 | // (deleted)" with signed bytes, but is not the inode hashed. |
| 457 | {"same-name-other-inode", func(f *deletedExeFixture) (func(bool, int), func(bool, int)) { |
| 458 | return nil, func(_ bool, call int) { |
| 459 | if call == 1 { |
| 460 | f.writeImage(t, deletedExeBody, 0o755, true) |
| 461 | } |
| 462 | } |
| 463 | }}, |
| 464 | // It execs the helper after the first check and is back on the |
| 465 | // proven image by the end: the check at the mounts use sees it. |
| 466 | {"between-uses", func(f *deletedExeFixture) (func(bool, int), func(bool, int)) { |
| 467 | target, err := os.Readlink(f.task + "/exe") |
| 468 | if err != nil { |
| 469 | t.Fatal(err) |
| 470 | } |
| 471 | return func(final bool, call int) { |
| 472 | if !final && call == 1 { |
| 473 | helper(f) |
| 474 | } |
| 475 | }, func(final bool, _ int) { |
| 476 | if final { |
| 477 | generationRelink(t, target, f.task+"/exe") |
| 478 | } |
| 479 | } |
| 480 | }}, |
| 481 | // The proven image itself is made group-writable mid-inspection. |
| 482 | {"image-made-writable", func(f *deletedExeFixture) (func(bool, int), func(bool, int)) { |
| 483 | return nil, func(_ bool, call int) { |
| 484 | if call == 1 { |
| 485 | if err := f.imageFile.Chmod(0o775); err != nil { |
| 486 | t.Fatal(err) |
| 487 | } |
| 488 | } |
| 489 | } |
| 490 | }}, |
| 491 | // It execs the helper after the last use, before the end. |
| 492 | {"before-the-end", func(f *deletedExeFixture) (func(bool, int), func(bool, int)) { |
| 493 | return func(final bool, call int) { |
| 494 | if !final && call == 2 { |
| 495 | helper(f) |
| 496 | } |
| 497 | }, nil |
| 498 | }}, |
| 499 | } { |
| 500 | t.Run(tc.name, func(t *testing.T) { |
| 501 | f := deletedExe(t) |
| 502 | if err := f.execRace(t, nil, nil); err != nil { |
| 503 | t.Fatalf("census without a race refused: %v", err) |
| 504 | } |
| 505 | after, before := tc.race(f) |
| 506 | err := f.execRace(t, after, before) |
| 507 | if err == nil { |
| 508 | t.Fatal("census accepted a task that exec'd away from its proven image") |
| 509 | } |
| 510 | if !strings.Contains(err.Error(), "exe binding check refused") { |
| 511 | t.Fatalf("refusal %q does not name the exe binding check", err) |
| 512 | } |
| 513 | var task *generationTaskRefusal |
| 514 | if !errors.As(err, &task) || !task.transient() { |
| 515 | t.Fatalf("refusal %v is not a transient task refusal a later pass can clear", err) |
| 516 | } |
| 517 | }) |
| 518 | } |
| 519 | } |
| 520 | |
| 521 | func TestRecoverCensusNeedsABindingForATrustedTask(t *testing.T) { |
| 522 | // A kernel wired with a lookup but no recheck refuses every task the |
| 523 | // lookup trusts. |
| 524 | f := deletedExe(t) |
| 525 | classify, _ := f.env.reader(t.Context()) |
| 526 | if _, err := (generationKernel{proc: f.proc, service: classify}).absent(t.Context(), f.reservation); err == nil || !strings.Contains(err.Error(), "no executable binding") { |
| 527 | t.Fatalf("census without a recheck = %v", err) |
| 528 | } |
| 529 | } |
| 530 | |
| 531 | func TestRecoverCensusDeadlineCountsInspectionTime(t *testing.T) { |
| 532 | clock := time.Unix(0, 0) |
| 533 | now := func() time.Time { return clock } |
| 534 | sleep := func(_ context.Context, d time.Duration) error { clock = clock.Add(d); return nil } |
| 535 | transient := &generationTaskRefusal{task: "/proc/9/task/9", err: os.ErrNotExist} |
| 536 | |
| 537 | // A slow pass that succeeds past the deadline refuses. |
| 538 | _, _, err := generationCensusRetryFor(t.Context(), func(context.Context) (string, string, error) { |
| 539 | clock = clock.Add(25 * time.Second) |
| 540 | return "boot", "digest", nil |
| 541 | }, 20*time.Second, now, sleep) |
| 542 | if !errors.Is(err, errGenerationCensusLate) { |
| 543 | t.Fatalf("a pass that ended past the window = %v, want a late refusal", err) |
| 544 | } |
| 545 | |
| 546 | // Slow refused passes: inspection time and waits share the deadline, |
| 547 | // no pass starts after it, and the census refuses inside it. |
| 548 | clock = time.Unix(0, 0) |
| 549 | var starts []time.Duration |
| 550 | _, _, err = generationCensusRetryFor(t.Context(), func(context.Context) (string, string, error) { |
| 551 | starts = append(starts, clock.Sub(time.Unix(0, 0))) |
| 552 | clock = clock.Add(6 * time.Second) |
| 553 | return "", "", transient |
| 554 | }, 20*time.Second, now, sleep) |
| 555 | if err == nil { |
| 556 | t.Fatal("persistent refusal accepted") |
| 557 | } |
| 558 | for _, s := range starts { |
| 559 | if s >= 20*time.Second { |
| 560 | t.Fatalf("a pass started at %s, past the window (%v)", s, starts) |
| 561 | } |
| 562 | } |
| 563 | if end := clock.Sub(time.Unix(0, 0)); end > 26*time.Second { |
| 564 | t.Fatalf("census ran to %s with 6 s passes; it must stop at the first pass that ends past 20 s", end) |
| 565 | } |
| 566 | if len(starts) < 2 { |
| 567 | t.Fatalf("passes started at %v: the slow passes were not retried inside the window", starts) |
| 568 | } |
| 569 | |
| 570 | // A wait that overruns (a timer firing late) never starts a pass past |
| 571 | // the deadline. |
| 572 | clock, starts = time.Unix(0, 0), nil |
| 573 | oversleep := func(_ context.Context, d time.Duration) error { clock = clock.Add(d + 3*time.Second); return nil } |
| 574 | _, _, err = generationCensusRetryFor(t.Context(), func(context.Context) (string, string, error) { |
| 575 | starts = append(starts, clock.Sub(time.Unix(0, 0))) |
| 576 | return "", "", transient |
| 577 | }, 20*time.Second, now, oversleep) |
| 578 | if !errors.Is(err, errGenerationCensusLate) { |
| 579 | t.Fatalf("overrun wait = %v, want a late refusal", err) |
| 580 | } |
| 581 | for _, s := range starts { |
| 582 | if s >= 20*time.Second { |
| 583 | t.Fatalf("a pass started at %s, past the window (%v)", s, starts) |
| 584 | } |
| 585 | } |
| 586 | } |
| 587 | |
| 588 | func TestRecoverCensusDeadlineReachesTheInspection(t *testing.T) { |
| 589 | // On the real clock: the pass's context ends at the deadline, and a pass |
| 590 | // that only returns when it does is refused, promptly. |
| 591 | start := time.Now() |
| 592 | var deadline time.Time |
| 593 | var has bool |
| 594 | _, _, err := generationCensusRetryFor(t.Context(), func(ctx context.Context) (string, string, error) { |
| 595 | deadline, has = ctx.Deadline() |
| 596 | select { |
| 597 | case <-ctx.Done(): |
| 598 | case <-time.After(2 * time.Second): |
| 599 | } |
| 600 | return "boot", "digest", nil |
| 601 | }, 50*time.Millisecond, time.Now, generationSleep) |
| 602 | if !errors.Is(err, errGenerationCensusLate) { |
| 603 | t.Fatalf("a pass blocked to the deadline = %v, want a late refusal", err) |
| 604 | } |
| 605 | if !has || deadline.Sub(start) > 50*time.Millisecond+10*time.Millisecond { |
| 606 | t.Fatalf("pass context deadline = %v (set %t), want the census's", deadline.Sub(start), has) |
| 607 | } |
| 608 | if took := time.Since(start); took > 2*time.Second { |
| 609 | t.Fatalf("census took %s past a 50 ms window", took) |
| 610 | } |
| 611 | // The lookup's own blocking reads get that context: systemctl show and |
| 612 | // the image hash. |
| 613 | f := deletedExe(t) |
| 614 | var showDeadline bool |
| 615 | show := f.env.show |
| 616 | f.env.show = func(ctx context.Context, unit string) (map[string]string, error) { |
| 617 | _, showDeadline = ctx.Deadline() |
| 618 | return show(ctx, unit) |
| 619 | } |
| 620 | if _, _, err := generationCensusRetryFor(t.Context(), func(ctx context.Context) (string, string, error) { |
| 621 | return "boot", "digest", f.kernelCensus(ctx) |
| 622 | }, 20*time.Second, time.Now, generationSleep); err != nil { |
| 623 | t.Fatal(err) |
| 624 | } |
| 625 | if !showDeadline { |
| 626 | t.Fatal("systemctl show ran without the census deadline") |
| 627 | } |
| 628 | // The deadline passes after the lookup has started on the task: the |
| 629 | // image hash stops. |
| 630 | ctx, cancel := context.WithCancel(t.Context()) |
| 631 | f.env.show = func(ctx context.Context, unit string) (map[string]string, error) { |
| 632 | cancel() |
| 633 | return show(ctx, unit) |
| 634 | } |
| 635 | if err := f.kernelCensus(ctx); !errors.Is(err, context.Canceled) || !strings.Contains(err.Error(), "deleted exe check refused") { |
| 636 | t.Fatalf("image hash under an ended context = %v", err) |
| 637 | } |
| 638 | } |
| 639 | |
| 640 | // guardedEdge makes the fixture's unit the guarded carlos-edge.service: |
| 641 | // ExecStart is the guard, the selected program <opt>/carlos, and the task |
| 642 | // is the edge's main process in its supervise/ group. |
| 643 | func (f *deletedExeFixture) guardedEdge(t *testing.T) { |
| 644 | t.Helper() |
| 645 | f.unit = "carlos-edge.service" |
| 646 | f.execStart = "{ path=/opt/carlos/system/guard/carlos ; argv[]=/opt/carlos/system/guard/carlos system guard-exec edge ; ignore_errors=no ; start_time=[n/a] ; stop_time=[n/a] ; pid=41 ; code=(null) ; status=0/0 }" |
| 647 | binary := f.env.binary |
| 648 | f.env.binary = func(ctx context.Context, opt, path string) (rootFloorBinary, error) { |
| 649 | if path == "/opt/carlos/system/guard/carlos" { |
| 650 | return rootFloorBinary{Digest: "guard"}, nil |
| 651 | } |
| 652 | b, err := binary(ctx, opt, path) |
| 653 | b.File.Inode = 7 |
| 654 | return b, err |
| 655 | } |
| 656 | base := "/system.slice/carlos-edge.service" |
| 657 | generationWrite(t, f.task+"/cgroup", "0::"+base+"/supervise\n") |
| 658 | generationWrite(t, f.proc+"/41/cgroup", "0::"+base+"/supervise\n") |
| 659 | show := f.env.show |
| 660 | f.env.show = func(ctx context.Context, unit string) (map[string]string, error) { |
| 661 | props, err := show(ctx, unit) |
| 662 | if err == nil { |
| 663 | props["ControlGroup"] = base |
| 664 | } |
| 665 | return props, err |
| 666 | } |
| 667 | } |
| 668 | |
| 669 | func TestRecoverCensusDeletedExeOfARootTask(t *testing.T) { |
| 670 | // The deleted-exe acceptance also covers a root task of a unit with a |
| 671 | // selected image (the guarded edge), and only that among root tasks. |
| 672 | // The task runs in a private mount namespace, which the strict root |
| 673 | // scan refuses: only a trusted classification lets it pass. |
| 674 | root := func(t *testing.T, f *deletedExeFixture) { |
| 675 | generationWrite(t, f.task+"/status", "Tgid:\t41\nUid:\t0\t0\t0\t0\nKthread:\t0\n") |
| 676 | generationRelink(t, "private-service", f.task+"/ns/mnt") |
| 677 | } |
| 678 | t.Run("selected-image-signed", func(t *testing.T) { |
| 679 | f := deletedExe(t) |
| 680 | f.guardedEdge(t) |
| 681 | root(t, f) |
| 682 | if err := f.census(t); err != nil { |
| 683 | t.Fatalf("census refused a root guarded-edge task on its signed deleted image: %v", err) |
| 684 | } |
| 685 | }) |
| 686 | t.Run("selected-image-unsigned", func(t *testing.T) { |
| 687 | f := deletedExe(t) |
| 688 | f.guardedEdge(t) |
| 689 | root(t, f) |
| 690 | f.writeImage(t, "an image no identity signs", 0o755, true) |
| 691 | if err := f.census(t); err == nil { |
| 692 | t.Fatal("census accepted a root guarded-edge task on an unsigned deleted image") |
| 693 | } |
| 694 | }) |
| 695 | t.Run("no-selected-image", func(t *testing.T) { |
| 696 | // A root task of a unit with no selected image keeps main's path |
| 697 | // walk, which a deleted exe fails, so the strict root scan applies. |
| 698 | f := deletedExe(t) |
| 699 | root(t, f) |
| 700 | if err := f.census(t); err == nil { |
| 701 | t.Fatal("census trusted a root task of an unselected unit on its deleted exe") |
| 702 | } |
| 703 | }) |
| 704 | t.Run("selected-image-exec-race", func(t *testing.T) { |
| 705 | f := deletedExe(t) |
| 706 | f.guardedEdge(t) |
| 707 | root(t, f) |
| 708 | err := f.execRace(t, nil, func(_ bool, call int) { |
| 709 | if call == 1 { |
| 710 | generationRelink(t, f.unrelated, f.task+"/exe") |
| 711 | } |
| 712 | }) |
| 713 | if err == nil || !strings.Contains(err.Error(), "exe binding check refused") { |
| 714 | t.Fatalf("root guarded-edge task that exec'd away = %v", err) |
| 715 | } |
| 716 | }) |
| 717 | } |
| 718 | |
| 719 | // slowImage returns one byte per read and ends ctx after the first. |
| 720 | type slowImage struct { |
| 721 | cancel func() |
| 722 | reads int |
| 723 | } |
| 724 | |
| 725 | func (s *slowImage) Read(p []byte) (int, error) { |
| 726 | s.reads++ |
| 727 | if s.reads == 1 { |
| 728 | s.cancel() |
| 729 | } |
| 730 | if len(p) == 0 { |
| 731 | return 0, nil |
| 732 | } |
| 733 | p[0] = 'x' |
| 734 | return 1, nil |
| 735 | } |
| 736 | |
| 737 | func TestSignedBinaryProofStopsWhenTheCensusDeadlineEnds(t *testing.T) { |
| 738 | // The hash: a slow image whose read outlives the deadline. |
| 739 | ctx, cancel := context.WithCancel(t.Context()) |
| 740 | image := &slowImage{cancel: cancel} |
| 741 | if _, err := rootFloorDigest(ctx, image); !errors.Is(err, context.Canceled) || image.reads > 2 { |
| 742 | t.Fatalf("digest = %v after %d reads, want it stopped at the deadline", err, image.reads) |
| 743 | } |
| 744 | // The identity scan: once the deadline has passed it reads no identity. |
| 745 | reads := 0 |
| 746 | ctx, cancel = context.WithCancel(t.Context()) |
| 747 | cancel() |
| 748 | if _, err := rootFloorSignedIdentity(ctx, nil, rootFloorBinary{Digest: "d"}, []string{"a.json"}, func(string) ([]byte, error) { reads++; return nil, nil }); !errors.Is(err, context.Canceled) || reads != 0 { |
| 749 | t.Fatalf("identity scan after the deadline = %v after %d reads", err, reads) |
| 750 | } |
| 751 | } |
| 752 | |
| 753 | func TestRecoverCensusDeadlineReachesTheSignedBinaryProof(t *testing.T) { |
| 754 | // The lookup hands the census's deadline context to the signed-binary |
| 755 | // proof, for the deleted image and for the guarded edge's guard and |
| 756 | // selected images: a proof that only returns when that context ends |
| 757 | // is cut off at the deadline. |
| 758 | for _, guarded := range []bool{false, true} { |
| 759 | t.Run(map[bool]string{false: "deleted-image", true: "guarded-edge"}[guarded], func(t *testing.T) { |
| 760 | f := deletedExe(t) |
| 761 | if guarded { |
| 762 | f.guardedEdge(t) |
| 763 | } |
| 764 | proofs := 0 |
| 765 | f.env.binary = func(ctx context.Context, opt, path string) (rootFloorBinary, error) { |
| 766 | proofs++ |
| 767 | if _, ok := ctx.Deadline(); !ok { |
| 768 | t.Error("signed-binary proof ran without the census deadline") |
| 769 | } |
| 770 | select { |
| 771 | case <-ctx.Done(): |
| 772 | return rootFloorBinary{}, ctx.Err() |
| 773 | case <-time.After(5 * time.Second): |
| 774 | return rootFloorBinary{}, errors.New("proof outlived the deadline") |
| 775 | } |
| 776 | } |
| 777 | start := time.Now() |
| 778 | _, _, err := generationCensusRetryFor(t.Context(), func(ctx context.Context) (string, string, error) { |
| 779 | return "boot", "digest", f.kernelCensus(ctx) |
| 780 | }, 100*time.Millisecond, time.Now, generationSleep) |
| 781 | if !errors.Is(err, errGenerationCensusLate) { |
| 782 | t.Fatalf("census = %v, want a late refusal", err) |
| 783 | } |
| 784 | if took := time.Since(start); took > 2*time.Second { |
| 785 | t.Fatalf("census took %s past a 100 ms window: the proof ignored its context", took) |
| 786 | } |
| 787 | if proofs == 0 { |
| 788 | t.Fatal("the proof never ran") |
| 789 | } |
| 790 | }) |
| 791 | } |
| 792 | } |
| 793 | |
amadan