| 1 | package auth |
| 2 | |
| 3 | import ( |
| 4 | "crypto/rand" |
| 5 | "crypto/sha256" |
| 6 | "encoding/base64" |
| 7 | "encoding/hex" |
| 8 | "errors" |
| 9 | "fmt" |
| 10 | "net/url" |
| 11 | "strings" |
| 12 | "sync" |
| 13 | "time" |
| 14 | |
| 15 | "github.com/FelineStateMachine/tinyrelay/protocol/nostr" |
| 16 | ) |
| 17 | |
| 18 | const tokenSkew = time.Minute |
| 19 | |
| 20 | var ErrMissingAuthorization = errors.New("auth-required: missing Nostr Authorization header" ) |
| 21 | |
| 22 | type Validator struct { |
| 23 | now func() time.Time |
| 24 | mu sync.Mutex |
| 25 | seen map[string]time.Time |
| 26 | } |
| 27 | |
| 28 | // NewValidator uses now to check proof freshness and track replay windows. |
| 29 | // A nil clock selects the system clock. |
| 30 | func NewValidator(now func() time.Time) *Validator { |
| 31 | if now == nil { |
| 32 | now = time.Now |
| 33 | } |
| 34 | return &Validator{now: now, seen: make(map[string]time.Time)} |
| 35 | } |
| 36 | |
| 37 | // VerifyNIP98 validates a kind 27235 request proof against the exact URL, |
| 38 | // method and body supplied by the caller. Successfully verified event IDs are |
| 39 | // retained for the one-minute replay window. |
| 40 | func (v *Validator) VerifyNIP98(header, rawURL, method, body string) (nostr.Event, error) { |
| 41 | e, err := decodeToken(header, "NIP-98" ) |
| 42 | if err != nil { |
| 43 | return nostr.Event{}, err |
| 44 | } |
| 45 | if err := nostr.Validate(e); err != nil { |
| 46 | return nostr.Event{}, authError(err.Error()) |
| 47 | } |
| 48 | if e.Kind != 27235 { |
| 49 | return nostr.Event{}, authError("token must be kind 27235" ) |
| 50 | } |
| 51 | now := v.now() |
| 52 | if outsideSkew(now, e.CreatedAt) { |
| 53 | return nostr.Event{}, authError("token expired" ) |
| 54 | } |
| 55 | if err := sameRequestURL(nostr.Tag(e, "u" ), rawURL); err != nil { |
| 56 | return nostr.Event{}, err |
| 57 | } |
| 58 | if strings.ToUpper(nostr.Tag(e, "method" )) != strings.ToUpper(method) { |
| 59 | return nostr.Event{}, authError("token was signed for another method" ) |
| 60 | } |
| 61 | if body != "" && nostr.Tag(e, "payload" ) != hashBytes([]byte(body)) { |
| 62 | return nostr.Event{}, authError("token payload hash does not match the body" ) |
| 63 | } |
| 64 | if err := v.mark(e.ID, now); err != nil { |
| 65 | return nostr.Event{}, err |
| 66 | } |
| 67 | return e, nil |
| 68 | } |
| 69 | |
| 70 | // VerifyBlossom validates a BUD-11 authorization for action. It accepts the |
| 71 | // protocol's reusable authorization form and checks its action and expiry. |
| 72 | func (v *Validator) VerifyBlossom(header, action string) (nostr.Event, error) { |
| 73 | return v.verifyBlossom(header, action, "" , "" , false) |
| 74 | } |
| 75 | |
| 76 | // VerifyBlossomRequest validates a BUD-11 authorization with optional server |
| 77 | // and blob-hash scope. Upload, delete, mirror and media actions require an x |
| 78 | // tag when this scoped form is used. |
| 79 | func (v *Validator) VerifyBlossomRequest(header, action, server, blobHash string) (nostr.Event, error) { |
| 80 | return v.verifyBlossom(header, action, server, blobHash, true) |
| 81 | } |
| 82 | |
| 83 | // IsBlossomAuthorization reports whether an Authorization header contains a |
| 84 | // signed BUD-11 event. Malformed tokens return false so callers can produce |
| 85 | // their normal authentication error through the protocol-specific verifier. |
| 86 | func IsBlossomAuthorization(header string) bool { |
| 87 | e, err := decodeToken(header, "Blossom" ) |
| 88 | return err == nil && e.Kind == 24242 |
| 89 | } |
| 90 | |
| 91 | func (v *Validator) verifyBlossom(header, action, server, blobHash string, strict bool) (nostr.Event, error) { |
| 92 | e, err := decodeToken(header, "Blossom" ) |
| 93 | if err != nil { |
| 94 | return nostr.Event{}, err |
| 95 | } |
| 96 | if err := nostr.Validate(e); err != nil { |
| 97 | return nostr.Event{}, authError(err.Error()) |
| 98 | } |
| 99 | if e.Kind != 24242 { |
| 100 | return nostr.Event{}, authError("token must be kind 24242" ) |
| 101 | } |
| 102 | if nostr.Tag(e, "t" ) != action { |
| 103 | return nostr.Event{}, authError(fmt.Sprintf("token is not for %s" , action)) |
| 104 | } |
| 105 | if strict && server != "" && !blossomServerScope(e, server) { |
| 106 | return nostr.Event{}, authError("token is not scoped to this server" ) |
| 107 | } |
| 108 | now := v.now() |
| 109 | expiration := nostr.Expiration(e) |
| 110 | if expiration == 0 || expiration <= now.Unix() { |
| 111 | return nostr.Event{}, authError("token expired" ) |
| 112 | } |
| 113 | // BUD-11 authorization timestamps may not be from the future. The |
| 114 | // expiration tag, rather than an arbitrary maximum age, controls how long |
| 115 | // an otherwise valid token remains usable. |
| 116 | if e.CreatedAt > now.Unix() { |
| 117 | return nostr.Event{}, authError("token is from the future" ) |
| 118 | } |
| 119 | if strict && requiresBlobScope(action) && len(nostr.TagValues(e, "x" )) == 0 { |
| 120 | return nostr.Event{}, authError("token must include an x tag" ) |
| 121 | } |
| 122 | if strict && blobHash != "" && len(nostr.TagValues(e, "x" )) > 0 && !contains(nostr.TagValues(e, "x" ), blobHash) { |
| 123 | return nostr.Event{}, authError("token x tag does not name this blob" ) |
| 124 | } |
| 125 | return e, nil |
| 126 | } |
| 127 | |
| 128 | func requiresBlobScope(action string) bool { |
| 129 | switch action { |
| 130 | case "upload" , "delete" , "mirror" , "media" : |
| 131 | return true |
| 132 | default: |
| 133 | return false |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | func blossomServerScope(e nostr.Event, server string) bool { |
| 138 | for _, value := range nostr.TagValues(e, "server" ) { |
| 139 | if strings.EqualFold(strings.TrimSpace(value), strings.TrimSpace(server)) { |
| 140 | return true |
| 141 | } |
| 142 | } |
| 143 | return len(nostr.TagValues(e, "server" )) == 0 |
| 144 | } |
| 145 | |
| 146 | func (v *Validator) WhoAsks(header, rawURL, method, body, action, blobHash string) ([]string, error) { |
| 147 | if strings.TrimSpace(header) == "" { |
| 148 | return nil, nil |
| 149 | } |
| 150 | e, err := decodeToken(header, "authorization" ) |
| 151 | if err != nil { |
| 152 | return nil, err |
| 153 | } |
| 154 | if e.Kind == 24242 { |
| 155 | if action == "" { |
| 156 | return nil, authError("this door takes a NIP-98 signature" ) |
| 157 | } |
| 158 | e, err = v.VerifyBlossom(header, action) |
| 159 | if err != nil { |
| 160 | return nil, err |
| 161 | } |
| 162 | xs := nostr.TagValues(e, "x" ) |
| 163 | if blobHash != "" && len(xs) > 0 && !contains(xs, blobHash) { |
| 164 | return nil, authError("token x tag does not name this blob" ) |
| 165 | } |
| 166 | return []string{e.PubKey}, nil |
| 167 | } |
| 168 | e, err = v.VerifyNIP98(header, rawURL, method, body) |
| 169 | if err != nil { |
| 170 | return nil, err |
| 171 | } |
| 172 | return []string{e.PubKey}, nil |
| 173 | } |
| 174 | |
| 175 | // ValidateBlobPayload checks the hash binding on a token that was already |
| 176 | // authenticated by WhoAsks. It deliberately does not mark the event as seen a |
| 177 | // second time: upload authorization and the streamed body validator inspect |
| 178 | // the same proof at two different points in the request. |
| 179 | func (v *Validator) ValidateBlobPayload(header, actualSHA string) error { |
| 180 | e, err := decodeToken(header, "authorization" ) |
| 181 | if err != nil { |
| 182 | return err |
| 183 | } |
| 184 | if err := nostr.Validate(e); err != nil { |
| 185 | return authError(err.Error()) |
| 186 | } |
| 187 | switch e.Kind { |
| 188 | case 24242: |
| 189 | if values := nostr.TagValues(e, "x" ); len(values) > 0 && !contains(values, actualSHA) { |
| 190 | return authError("token x tag does not name this blob" ) |
| 191 | } |
| 192 | case 27235: |
| 193 | if nostr.Tag(e, "payload" ) != actualSHA { |
| 194 | return authError("token payload hash does not match the blob hash" ) |
| 195 | } |
| 196 | default: |
| 197 | return authError("token must be kind 24242 or 27235" ) |
| 198 | } |
| 199 | return nil |
| 200 | } |
| 201 | |
| 202 | // ValidateBlossomPayload rechecks the content hash for a Blossom-authenticated |
| 203 | // operation after a streaming body has been materialized. It does not mark the |
| 204 | // authorization event as seen a second time. |
| 205 | func (v *Validator) ValidateBlossomPayload(header, action, actualSHA string) error { |
| 206 | e, err := v.VerifyBlossom(header, action) |
| 207 | if err != nil { |
| 208 | return err |
| 209 | } |
| 210 | if values := nostr.TagValues(e, "x" ); len(values) > 0 && !contains(values, actualSHA) { |
| 211 | return authError("token x tag does not name this blob" ) |
| 212 | } |
| 213 | return nil |
| 214 | } |
| 215 | |
| 216 | type ChallengeManager struct { |
| 217 | relayURL string |
| 218 | now func() time.Time |
| 219 | mu sync.Mutex |
| 220 | active map[string]time.Time |
| 221 | } |
| 222 | |
| 223 | // NewChallengeManager creates a NIP-42 challenge store for relayURL. Issued |
| 224 | // challenges are single-use and expire with the validator replay window. |
| 225 | func NewChallengeManager(relayURL string, now func() time.Time) *ChallengeManager { |
| 226 | if now == nil { |
| 227 | now = time.Now |
| 228 | } |
| 229 | return &ChallengeManager{relayURL: relayURL, now: now, active: make(map[string]time.Time)} |
| 230 | } |
| 231 | |
| 232 | // Issue creates and stores a cryptographically random NIP-42 challenge. |
| 233 | func (m *ChallengeManager) Issue() (string, error) { |
| 234 | raw := make([]byte, 32) |
| 235 | if _, err := rand.Read(raw); err != nil { |
| 236 | return "" , fmt.Errorf("create NIP-42 challenge: %w" , err) |
| 237 | } |
| 238 | challenge := hex.EncodeToString(raw) |
| 239 | now := m.now() |
| 240 | m.mu.Lock() |
| 241 | m.prune(now) |
| 242 | m.active[challenge] = now.Add(tokenSkew) |
| 243 | m.mu.Unlock() |
| 244 | return challenge, nil |
| 245 | } |
| 246 | |
| 247 | // Verify validates and consumes a NIP-42 AUTH event for the configured relay. |
| 248 | func (m *ChallengeManager) Verify(e nostr.Event) error { |
| 249 | if err := nostr.Validate(e); err != nil { |
| 250 | return authError(err.Error()) |
| 251 | } |
| 252 | if e.Kind != 22242 { |
| 253 | return authError("AUTH event must be kind 22242" ) |
| 254 | } |
| 255 | now := m.now() |
| 256 | if outsideSkew(now, e.CreatedAt) { |
| 257 | return authError("AUTH event timestamp expired" ) |
| 258 | } |
| 259 | if nostr.Tag(e, "relay" ) != m.relayURL { |
| 260 | return authError("AUTH event names another relay" ) |
| 261 | } |
| 262 | challenge := nostr.Tag(e, "challenge" ) |
| 263 | m.mu.Lock() |
| 264 | defer m.mu.Unlock() |
| 265 | m.prune(now) |
| 266 | if _, ok := m.active[challenge]; !ok { |
| 267 | return authError("AUTH challenge is unknown or already used" ) |
| 268 | } |
| 269 | delete(m.active, challenge) |
| 270 | return nil |
| 271 | } |
| 272 | |
| 273 | func (m *ChallengeManager) prune(now time.Time) { |
| 274 | for challenge, expires := range m.active { |
| 275 | if !expires.After(now) { |
| 276 | delete(m.active, challenge) |
| 277 | } |
| 278 | } |
| 279 | } |
| 280 | |
| 281 | func (v *Validator) mark(id string, now time.Time) error { |
| 282 | v.mu.Lock() |
| 283 | defer v.mu.Unlock() |
| 284 | for seenID, at := range v.seen { |
| 285 | if now.Sub(at) > tokenSkew { |
| 286 | delete(v.seen, seenID) |
| 287 | } |
| 288 | } |
| 289 | if _, ok := v.seen[id]; ok { |
| 290 | return authError("token replay detected" ) |
| 291 | } |
| 292 | v.seen[id] = now |
| 293 | return nil |
| 294 | } |
| 295 | |
| 296 | func decodeToken(header, tokenName string) (nostr.Event, error) { |
| 297 | parts := strings.Fields(header) |
| 298 | if len(parts) != 2 || !strings.EqualFold(parts[0], "Nostr" ) { |
| 299 | return nostr.Event{}, ErrMissingAuthorization |
| 300 | } |
| 301 | raw, err := decodeBase64(parts[1]) |
| 302 | if err != nil { |
| 303 | return nostr.Event{}, authError(fmt.Sprintf("malformed %s token" , tokenName)) |
| 304 | } |
| 305 | e, err := nostr.Parse(raw) |
| 306 | if err != nil { |
| 307 | return nostr.Event{}, authError(err.Error()) |
| 308 | } |
| 309 | return e, nil |
| 310 | } |
| 311 | |
| 312 | func decodeBase64(value string) ([]byte, error) { |
| 313 | for _, encoding := range []*base64.Encoding{base64.StdEncoding, base64.RawStdEncoding, base64.URLEncoding, base64.RawURLEncoding} { |
| 314 | if raw, err := encoding.DecodeString(value); err == nil { |
| 315 | return raw, nil |
| 316 | } |
| 317 | } |
| 318 | return nil, errors.New("invalid base64" ) |
| 319 | } |
| 320 | |
| 321 | func sameRequestURL(signed, requested string) error { |
| 322 | want, ok := normalizedRequestURL(requested) |
| 323 | if !ok { |
| 324 | return authError("token was signed for another URL" ) |
| 325 | } |
| 326 | got, ok := normalizedRequestURL(signed) |
| 327 | if !ok || got != want { |
| 328 | return authError("token was signed for another URL" ) |
| 329 | } |
| 330 | return nil |
| 331 | } |
| 332 | |
| 333 | func normalizedRequestURL(raw string) (string, bool) { |
| 334 | u, err := url.Parse(strings.TrimSpace(raw)) |
| 335 | if err != nil || u.Scheme == "" || u.Host == "" || u.User != nil || u.Fragment != "" || u.Opaque != "" { |
| 336 | return "" , false |
| 337 | } |
| 338 | path := u.EscapedPath() |
| 339 | if path == "" { |
| 340 | path = "/" |
| 341 | } |
| 342 | // URL.Host preserves a possibly meaningful port while hostname matching is |
| 343 | // case insensitive. Query strings remain part of the NIP-98 binding. |
| 344 | host := strings.ToLower(u.Hostname()) |
| 345 | if port := u.Port(); port != "" { |
| 346 | host += ":" + port |
| 347 | } |
| 348 | return strings.ToLower(u.Scheme) + "://" + host + path + "?" + u.RawQuery, true |
| 349 | } |
| 350 | |
| 351 | func outsideSkew(now time.Time, createdAt int64) bool { |
| 352 | delta := now.Unix() - createdAt |
| 353 | return delta > int64(tokenSkew/time.Second) || delta < -int64(tokenSkew/time.Second) |
| 354 | } |
| 355 | |
| 356 | func hashBytes(value []byte) string { |
| 357 | sum := sha256.Sum256(value) |
| 358 | return hex.EncodeToString(sum[:]) |
| 359 | } |
| 360 | |
| 361 | func authError(reason string) error { return fmt.Errorf("auth-required: %s" , reason) } |
| 362 | func contains(values []string, value string) bool { |
| 363 | for _, candidate := range values { |
| 364 | if candidate == value { |
| 365 | return true |
| 366 | } |
| 367 | } |
| 368 | return false |
| 369 | } |