| 1 | package roster |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "crypto/rand" |
| 6 | "encoding/base64" |
| 7 | "io" |
| 8 | "net/http" |
| 9 | "net/url" |
| 10 | "sync" |
| 11 | "time" |
| 12 | |
| 13 | "amadan.net/oficina/home/handoff" |
| 14 | "github.com/go-json-experiment/json" |
| 15 | ) |
| 16 | |
| 17 | const ( |
| 18 | RefreshAfter = 30 * time.Second |
| 19 | MaximumAge = 60 * time.Second |
| 20 | FetchTimeout = 5 * time.Second |
| 21 | RetryAfter = 5 * time.Second |
| 22 | // A backward wall-clock discrepancy beyond two seconds fences standing. |
| 23 | // Comparing wall advancement to monotonic advancement tolerates ordinary slew. |
| 24 | ClockTolerance = 2 * time.Second |
| 25 | recordLimit = 1024 |
| 26 | ) |
| 27 | |
| 28 | // Clock returns wall time and monotonic elapsed time from one observation. The |
| 29 | // elapsed value must never go backwards. Nil Config.Clock uses Go's monotonic clock. |
| 30 | type Clock interface { |
| 31 | Now() (time.Time, time.Duration) |
| 32 | } |
| 33 | type realClock struct{ start time.Time } |
| 34 | |
| 35 | func (c realClock) Now() (time.Time, time.Duration) { n := time.Now(); return n, n.Sub(c.start) } |
| 36 | |
| 37 | // Durable stores one opaque envelope. Save must atomically replace it, retaining |
| 38 | // the previous value on error. Load reports ErrNoEvidence only for absent data. |
| 39 | // Its implementation must honor context cancellation and use bounded local IO. |
| 40 | type Durable interface { |
| 41 | Load(context.Context) ([]byte, error) |
| 42 | Save(context.Context, []byte) error |
| 43 | } |
| 44 | |
| 45 | type Config struct { |
| 46 | Record VerifiedRecord |
| 47 | Token string |
| 48 | Transport http.RoundTripper |
| 49 | Durable Durable |
| 50 | Sealer handoff.Sealer |
| 51 | Clock Clock |
| 52 | } |
| 53 | |
| 54 | type State uint8 |
| 55 | |
| 56 | const ( |
| 57 | Unknown State = iota |
| 58 | NotMember |
| 59 | Member |
| 60 | ) |
| 61 | |
| 62 | type Decision struct { |
| 63 | State State |
| 64 | Role string |
| 65 | Lease Lease |
| 66 | } |
| 67 | |
| 68 | // Lease is an observation, not a stored authorization grant. Call Valid at the |
| 69 | // protected operation boundary; stream users must recheck and re-arm their timer |
| 70 | // from a new decision after renewal, or close when renewal cannot authorize it. |
| 71 | // Both accessors refuse immediately on cache contention: a caller may hold the |
| 72 | // database writer that an in-flight durable publication needs to acquire. |
| 73 | type Lease struct { |
| 74 | cache *Cache |
| 75 | version uint64 |
| 76 | deadline time.Duration |
| 77 | } |
| 78 | |
| 79 | func (l Lease) Valid() bool { |
| 80 | if l.cache == nil { |
| 81 | return false |
| 82 | } |
| 83 | c := l.cache |
| 84 | if !c.mu.TryLock() { |
| 85 | return false |
| 86 | } |
| 87 | defer c.mu.Unlock() |
| 88 | _, n := c.observe() |
| 89 | return c.version == l.version && c.usable && n < l.deadline |
| 90 | } |
| 91 | func (l Lease) Remaining() time.Duration { |
| 92 | if l.cache == nil { |
| 93 | return 0 |
| 94 | } |
| 95 | c := l.cache |
| 96 | if !c.mu.TryLock() { |
| 97 | return 0 |
| 98 | } |
| 99 | defer c.mu.Unlock() |
| 100 | _, n := c.observe() |
| 101 | if c.version != l.version || !c.usable || n >= l.deadline { |
| 102 | return 0 |
| 103 | } |
| 104 | return l.deadline - n |
| 105 | } |
| 106 | |
| 107 | type receipt struct { |
| 108 | Operation string `json:"operation"` |
| 109 | Digest string `json:"digest"` |
| 110 | } |
| 111 | type evidence struct { |
| 112 | Snapshot bool `json:"snapshot"` |
| 113 | Blocked bool `json:"blocked"` |
| 114 | Version int `json:"version"` |
| 115 | Sequence int64 `json:"sequence"` |
| 116 | RecordDigest string `json:"record_digest"` |
| 117 | Generation string `json:"generation"` |
| 118 | Epoch int64 `json:"epoch"` |
| 119 | Members []MemberEntry `json:"members"` |
| 120 | Digest string `json:"digest"` |
| 121 | Receipts []receipt `json:"receipts"` |
| 122 | } |
| 123 | |
| 124 | type flight struct { |
| 125 | done chan struct{} |
| 126 | err error |
| 127 | cancel context.CancelFunc |
| 128 | } |
| 129 | type Cache struct { |
| 130 | mu sync.Mutex |
| 131 | record VerifiedRecord |
| 132 | token string |
| 133 | client *http.Client |
| 134 | durable Durable |
| 135 | sealer handoff.Sealer |
| 136 | purpose string |
| 137 | clock Clock |
| 138 | seen bool |
| 139 | wall time.Time |
| 140 | mono time.Duration |
| 141 | version uint64 |
| 142 | usable bool |
| 143 | start time.Duration |
| 144 | members map[string]string |
| 145 | evidence evidence |
| 146 | flight *flight |
| 147 | attempted bool |
| 148 | lastAttempt time.Duration |
| 149 | } |
| 150 | |
| 151 | func New(ctx context.Context, cfg Config) (*Cache, error) { |
| 152 | if !cfg.Record.valid || !ValidChallenge(cfg.Token) || cfg.Durable == nil || cfg.Sealer == nil { |
| 153 | return nil, ErrRefused |
| 154 | } |
| 155 | if cfg.Clock == nil { |
| 156 | cfg.Clock = realClock{time.Now()} |
| 157 | } |
| 158 | if cfg.Transport == nil { |
| 159 | tr := http.DefaultTransport.(*http.Transport).Clone() |
| 160 | tr.DisableCompression = true |
| 161 | cfg.Transport = tr |
| 162 | } |
| 163 | b, _ := json.Marshal(cfg.Record.record.Bindings) |
| 164 | c := &Cache{record: cfg.Record, token: cfg.Token, client: &http.Client{Transport: cfg.Transport, CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}, durable: cfg.Durable, sealer: cfg.Sealer, purpose: "oficina/roster/evidence/v1/" + hash(b), clock: cfg.Clock, version: 1} |
| 165 | raw, e := cfg.Durable.Load(ctx) |
| 166 | if e != nil && e != ErrNoEvidence { |
| 167 | return nil, ErrUnavailable |
| 168 | } |
| 169 | if e == nil { |
| 170 | if len(raw) > EvidenceLimit+128 { |
| 171 | return nil, ErrRefused |
| 172 | } |
| 173 | plain, err := cfg.Sealer.Open(c.purpose, raw) |
| 174 | if err != nil || len(plain) > EvidenceLimit || strict(plain, &c.evidence) != nil || !validEvidence(c.evidence) { |
| 175 | return nil, ErrRefused |
| 176 | } |
| 177 | } |
| 178 | ev, e := nextEvidence(c.evidence, cfg.Record) |
| 179 | if e != nil { |
| 180 | return nil, e |
| 181 | } |
| 182 | if e = c.save(ctx, ev); e != nil { |
| 183 | return nil, e |
| 184 | } |
| 185 | c.evidence = ev |
| 186 | return c, nil |
| 187 | } |
| 188 | func validEvidence(e evidence) bool { |
| 189 | if e.Version != 1 || e.Sequence < 1 || e.Epoch < 1 || !ValidChallenge(e.RecordDigest) || !ValidChallenge(e.Generation) || len(e.Receipts) == 0 || len(e.Receipts) > recordLimit || len(e.Members) > MemberLimit { |
| 190 | return false |
| 191 | } |
| 192 | seen := map[string]bool{} |
| 193 | for _, r := range e.Receipts { |
| 194 | if !atom(r.Operation, 128) || !ValidChallenge(r.Digest) || seen[r.Operation] { |
| 195 | return false |
| 196 | } |
| 197 | seen[r.Operation] = true |
| 198 | } |
| 199 | for i, m := range e.Members { |
| 200 | if !validMember(m) || (i > 0 && e.Members[i-1].Subject >= m.Subject) { |
| 201 | return false |
| 202 | } |
| 203 | } |
| 204 | return e.Digest == memberDigest(e.Members) |
| 205 | } |
| 206 | func memberDigest(m []MemberEntry) string { |
| 207 | if m == nil { |
| 208 | m = []MemberEntry{} |
| 209 | } |
| 210 | b, _ := json.Marshal(m) |
| 211 | return hash(b) |
| 212 | } |
| 213 | func nextEvidence(old evidence, r VerifiedRecord) (evidence, error) { |
| 214 | p := r.record |
| 215 | if old.Version != 0 { |
| 216 | if p.Sequence < old.Sequence { |
| 217 | return evidence{}, ErrRefused |
| 218 | } |
| 219 | if p.Sequence == old.Sequence { |
| 220 | if r.digest != old.RecordDigest { |
| 221 | return evidence{}, ErrRefused |
| 222 | } |
| 223 | return old, nil |
| 224 | } |
| 225 | if p.Generation != old.Generation && p.OwnerConfirmation == "" { |
| 226 | return evidence{}, ErrRefused |
| 227 | } |
| 228 | } |
| 229 | for _, a := range old.Receipts { |
| 230 | if a.Operation == p.Operation { |
| 231 | return evidence{}, ErrRefused |
| 232 | } |
| 233 | } |
| 234 | if len(old.Receipts) >= recordLimit { |
| 235 | return evidence{}, ErrRefused |
| 236 | } |
| 237 | receipts := append(append([]receipt(nil), old.Receipts...), receipt{p.Operation, r.digest}) |
| 238 | ev := evidence{Version: 1, Sequence: p.Sequence, RecordDigest: r.digest, Generation: p.Generation, Epoch: p.MinEpoch, Members: []MemberEntry{}, Digest: memberDigest(nil), Receipts: receipts} |
| 239 | if old.Generation == p.Generation && old.Epoch >= p.MinEpoch { |
| 240 | ev.Epoch = old.Epoch |
| 241 | ev.Members = old.Members |
| 242 | ev.Digest = old.Digest |
| 243 | ev.Snapshot = old.Snapshot |
| 244 | } |
| 245 | if old.Generation == p.Generation { |
| 246 | ev.Blocked = old.Blocked |
| 247 | } |
| 248 | return ev, nil |
| 249 | } |
| 250 | func (c *Cache) save(ctx context.Context, e evidence) error { |
| 251 | raw, err := json.Marshal(e) |
| 252 | if err != nil || len(raw) > EvidenceLimit { |
| 253 | return ErrUnavailable |
| 254 | } |
| 255 | ct, err := c.sealer.Seal(c.purpose, raw) |
| 256 | if err != nil { |
| 257 | return ErrUnavailable |
| 258 | } |
| 259 | if err = c.durable.Save(ctx, ct); err != nil { |
| 260 | return ErrUnavailable |
| 261 | } |
| 262 | return nil |
| 263 | } |
| 264 | |
| 265 | // UpdateRecord accepts only independently operator-verified records for the same |
| 266 | // bindings. Durable failure changes neither the current floor nor usable lease. |
| 267 | func (c *Cache) UpdateRecord(ctx context.Context, r VerifiedRecord) error { |
| 268 | c.mu.Lock() |
| 269 | defer c.mu.Unlock() |
| 270 | if !r.valid || r.record.Bindings != c.record.record.Bindings || r.record.Sequence <= c.record.record.Sequence { |
| 271 | return ErrRefused |
| 272 | } |
| 273 | ev, e := nextEvidence(c.evidence, r) |
| 274 | if e != nil { |
| 275 | return e |
| 276 | } |
| 277 | if e = c.save(ctx, ev); e != nil { |
| 278 | return e |
| 279 | } |
| 280 | c.record = r |
| 281 | c.evidence = ev |
| 282 | c.fence() |
| 283 | c.attempted = false |
| 284 | return nil |
| 285 | } |
| 286 | func (c *Cache) fence() { |
| 287 | c.usable = false |
| 288 | c.version++ |
| 289 | if c.flight != nil { |
| 290 | c.flight.cancel() |
| 291 | } |
| 292 | } |
| 293 | func (c *Cache) observe() (time.Time, time.Duration) { |
| 294 | w, m := c.clock.Now() |
| 295 | if c.seen && (m < c.mono || w.Round(0).Sub(c.wall.Round(0)).Nanoseconds()-(m-c.mono).Nanoseconds() < -ClockTolerance.Nanoseconds()) { |
| 296 | c.fence() |
| 297 | } |
| 298 | c.wall = w |
| 299 | c.mono = m |
| 300 | c.seen = true |
| 301 | return w, m |
| 302 | } |
| 303 | |
| 304 | func (c *Cache) Check(ctx context.Context, issuer, teamID, subject string) Decision { |
| 305 | c.mu.Lock() |
| 306 | b := c.record.record.Bindings |
| 307 | if issuer != b.Issuer || teamID != b.Team || !validMember(MemberEntry{subject, "member"}) { |
| 308 | c.mu.Unlock() |
| 309 | return Decision{State: Unknown} |
| 310 | } |
| 311 | _, now := c.observe() |
| 312 | usable := c.usable && now < c.start+MaximumAge |
| 313 | due := !c.usable || now >= c.start+RefreshAfter |
| 314 | var f *flight |
| 315 | if due { |
| 316 | f = c.startRefresh(now) |
| 317 | } |
| 318 | if usable { |
| 319 | d := c.decision(subject) |
| 320 | c.mu.Unlock() |
| 321 | return d |
| 322 | } |
| 323 | c.mu.Unlock() |
| 324 | if f != nil { |
| 325 | select { |
| 326 | case <-ctx.Done(): |
| 327 | return Decision{State: Unknown} |
| 328 | case <-f.done: |
| 329 | } |
| 330 | } |
| 331 | c.mu.Lock() |
| 332 | defer c.mu.Unlock() |
| 333 | _, now = c.observe() |
| 334 | if !c.usable || now >= c.start+MaximumAge { |
| 335 | return Decision{State: Unknown} |
| 336 | } |
| 337 | return c.decision(subject) |
| 338 | } |
| 339 | func (c *Cache) decision(subject string) Decision { |
| 340 | role, ok := c.members[subject] |
| 341 | if !ok { |
| 342 | return Decision{State: NotMember} |
| 343 | } |
| 344 | return Decision{State: Member, Role: role, Lease: Lease{c, c.version, c.start + MaximumAge}} |
| 345 | } |
| 346 | |
| 347 | // Refresh joins the same bounded flight as Check. Caller cancellation stops |
| 348 | // waiting, not another request's shared refresh. Backoff never changes lease age. |
| 349 | func (c *Cache) Refresh(ctx context.Context) error { |
| 350 | c.mu.Lock() |
| 351 | _, now := c.observe() |
| 352 | f := c.startRefresh(now) |
| 353 | c.mu.Unlock() |
| 354 | if f == nil { |
| 355 | return ErrUnavailable |
| 356 | } |
| 357 | select { |
| 358 | case <-ctx.Done(): |
| 359 | return ErrUnavailable |
| 360 | case <-f.done: |
| 361 | return f.err |
| 362 | } |
| 363 | } |
| 364 | func (c *Cache) startRefresh(now time.Duration) *flight { |
| 365 | if c.flight != nil { |
| 366 | return c.flight |
| 367 | } |
| 368 | if c.evidence.Blocked { |
| 369 | return nil |
| 370 | } |
| 371 | if c.attempted && now-c.lastAttempt < RetryAfter { |
| 372 | return nil |
| 373 | } |
| 374 | ctx, cancel := context.WithTimeout(context.Background(), FetchTimeout) |
| 375 | f := &flight{done: make(chan struct{}), cancel: cancel} |
| 376 | c.flight = f |
| 377 | c.attempted = true |
| 378 | c.lastAttempt = now |
| 379 | r := c.record |
| 380 | version := c.version |
| 381 | go func() { |
| 382 | defer cancel() |
| 383 | err := c.fetch(ctx, r, version, now) |
| 384 | c.mu.Lock() |
| 385 | f.err = err |
| 386 | c.flight = nil |
| 387 | close(f.done) |
| 388 | c.mu.Unlock() |
| 389 | }() |
| 390 | return f |
| 391 | } |
| 392 | func (c *Cache) fetch(ctx context.Context, r VerifiedRecord, version uint64, start time.Duration) error { |
| 393 | random := make([]byte, 32) |
| 394 | if _, e := rand.Read(random); e != nil { |
| 395 | return ErrUnavailable |
| 396 | } |
| 397 | challenge := base64.RawURLEncoding.EncodeToString(random) |
| 398 | var members []MemberEntry |
| 399 | cursor := "" |
| 400 | epoch := int64(0) |
| 401 | seen := map[string]bool{} |
| 402 | for index := 0; index < 100; index++ { |
| 403 | q := url.Values{"team": {r.record.Bindings.Team}, "fetch": {challenge}} |
| 404 | if cursor != "" { |
| 405 | q.Set("cursor", cursor) |
| 406 | } |
| 407 | target := r.record.Bindings.Directory + "/roster?" + q.Encode() |
| 408 | if len(target) > 4096 { |
| 409 | return ErrRefused |
| 410 | } |
| 411 | req, e := http.NewRequestWithContext(ctx, http.MethodGet, target, nil) |
| 412 | if e != nil { |
| 413 | return ErrUnavailable |
| 414 | } |
| 415 | req.Header.Set("Authorization", "Bearer "+c.token) |
| 416 | req.Header.Set("Accept", "application/json") |
| 417 | req.Header.Set("Accept-Encoding", "identity") |
| 418 | response, e := c.client.Do(req) |
| 419 | if e != nil { |
| 420 | return ErrUnavailable |
| 421 | } |
| 422 | raw, readErr := io.ReadAll(io.LimitReader(response.Body, BodyLimit+1)) |
| 423 | response.Body.Close() |
| 424 | if readErr != nil || len(raw) > BodyLimit || response.Header.Get("Content-Type") != "application/json" || response.Header.Get("Content-Encoding") != "" || response.Uncompressed { |
| 425 | return ErrRefused |
| 426 | } |
| 427 | p, e := verifyPage(raw, r, challenge, cursor, response.StatusCode) |
| 428 | if e != nil { |
| 429 | return ErrRefused |
| 430 | } |
| 431 | if p.Generation != r.record.Generation { |
| 432 | c.mu.Lock() |
| 433 | if c.record.digest == r.digest { |
| 434 | ev := c.evidence |
| 435 | ev.Blocked = true |
| 436 | _ = c.save(ctx, ev) |
| 437 | c.evidence.Blocked = true |
| 438 | c.fence() |
| 439 | } |
| 440 | c.mu.Unlock() |
| 441 | return ErrRefused |
| 442 | } |
| 443 | if p.Type != "page" || *p.Index != index || p.Epoch < r.record.MinEpoch || (epoch != 0 && p.Epoch != epoch) { |
| 444 | return ErrRefused |
| 445 | } |
| 446 | epoch = p.Epoch |
| 447 | if len(members) > 0 && len(*p.Members) > 0 && members[len(members)-1].Subject >= (*p.Members)[0].Subject { |
| 448 | return ErrRefused |
| 449 | } |
| 450 | members = append(members, (*p.Members)...) |
| 451 | if len(members) > MemberLimit { |
| 452 | return ErrRefused |
| 453 | } |
| 454 | if *p.Complete { |
| 455 | return c.publish(ctx, r, version, start, epoch, members) |
| 456 | } |
| 457 | cursor = *p.Cursor |
| 458 | if seen[cursor] { |
| 459 | return ErrRefused |
| 460 | } |
| 461 | seen[cursor] = true |
| 462 | } |
| 463 | return ErrRefused |
| 464 | } |
| 465 | func (c *Cache) publish(ctx context.Context, r VerifiedRecord, version uint64, start time.Duration, epoch int64, members []MemberEntry) error { |
| 466 | c.mu.Lock() |
| 467 | defer c.mu.Unlock() |
| 468 | _, now := c.observe() |
| 469 | if ctx.Err() != nil || c.version != version || c.record.digest != r.digest || now-start >= FetchTimeout || epoch < c.evidence.Epoch { |
| 470 | return ErrUnavailable |
| 471 | } |
| 472 | digest := memberDigest(members) |
| 473 | // A provisioned floor without a fetched snapshot has no member digest yet. |
| 474 | if epoch == c.evidence.Epoch && c.evidence.Digest != "" && c.evidenceSnapshot() && digest != c.evidence.Digest { |
| 475 | return ErrRefused |
| 476 | } |
| 477 | ev := c.evidence |
| 478 | ev.Epoch = epoch |
| 479 | ev.Members = append([]MemberEntry{}, members...) |
| 480 | ev.Digest = digest |
| 481 | ev.Snapshot = true |
| 482 | if e := c.save(ctx, ev); e != nil { |
| 483 | return e |
| 484 | } |
| 485 | c.evidence = ev |
| 486 | _, now = c.observe() |
| 487 | if ctx.Err() != nil || c.version != version || now-start >= FetchTimeout { |
| 488 | return ErrUnavailable |
| 489 | } |
| 490 | c.members = make(map[string]string, len(members)) |
| 491 | for _, m := range members { |
| 492 | c.members[m.Subject] = m.Role |
| 493 | } |
| 494 | c.start = start |
| 495 | c.usable = true |
| 496 | c.version++ |
| 497 | return nil |
| 498 | } |
| 499 | func (c *Cache) evidenceSnapshot() bool { |
| 500 | return c.evidence.Snapshot |
| 501 | } |
| 502 | |
amadan