| 1 | package relay |
| 2 | |
| 3 | import ( |
| 4 | "encoding/base64" |
| 5 | "encoding/json" |
| 6 | "fmt" |
| 7 | ) |
| 8 | |
| 9 | // RegionMaster is one region's active issuer master (spec §4): the master |
| 10 | // key bytes and the kid it's issued under. |
| 11 | type RegionMaster struct { |
| 12 | Region string |
| 13 | Kid string |
| 14 | Master []byte |
| 15 | } |
| 16 | |
| 17 | // RegionURLs returns the STUN/TURN URLs for a region, built from the |
| 18 | // platform domain. |
| 19 | type RegionURLs func(region string) []string |
| 20 | |
| 21 | // ConfigEntry is one region's worth of the CARLOS_RELAY value (spec §2): |
| 22 | // the URLs to try, the derived key, and the username suffix a client |
| 23 | // appends its own expiry to. |
| 24 | type ConfigEntry struct { |
| 25 | Region string `json:"region"` |
| 26 | URLs []string `json:"urls"` |
| 27 | Key string `json:"key"` |
| 28 | UsernameSuffix string `json:"username_suffix"` |
| 29 | } |
| 30 | |
| 31 | // BuildConfig renders CARLOS_RELAY's value for r: base64(std, padded) of |
| 32 | // the JSON array from spec §2, one entry per region in r.Regions order. |
| 33 | // masters must cover every region in r.Regions, or BuildConfig refuses |
| 34 | // rather than issue a config a region can't actually serve. |
| 35 | func BuildConfig(acct, app string, r *Record, masters []RegionMaster, urls RegionURLs) (string, map[string]string, error) { |
| 36 | byRegion := map[string]RegionMaster{} |
| 37 | for _, m := range masters { |
| 38 | byRegion[m.Region] = m |
| 39 | } |
| 40 | entries := make([]ConfigEntry, 0, len(r.Regions)) |
| 41 | suffixes := map[string]string{} |
| 42 | for _, region := range r.Regions { |
| 43 | m, ok := byRegion[region] |
| 44 | if !ok { |
| 45 | return "", nil, fmt.Errorf("relay: no issuer master for region %s", region) |
| 46 | } |
| 47 | key := DeriveKey(m.Master, acct, app, r.Incarnation) |
| 48 | suffix := Suffix(acct, app, r.Incarnation, m.Kid) |
| 49 | suffixes[region] = suffix |
| 50 | entries = append(entries, ConfigEntry{Region: region, URLs: urls(region), Key: base64.StdEncoding.EncodeToString(key), UsernameSuffix: suffix}) |
| 51 | } |
| 52 | js, err := json.Marshal(entries) |
| 53 | if err != nil { |
| 54 | return "", nil, err |
| 55 | } |
| 56 | return base64.StdEncoding.EncodeToString(js), suffixes, nil |
| 57 | } |
| 58 | |
| 59 | // ParseConfig decodes a CARLOS_RELAY value back into its entries, for the |
| 60 | // config-ack (Task 12) and tests. |
| 61 | func ParseConfig(value string) ([]ConfigEntry, error) { |
| 62 | js, err := base64.StdEncoding.DecodeString(value) |
| 63 | if err != nil { |
| 64 | return nil, fmt.Errorf("relay: CARLOS_RELAY is not base64: %w", err) |
| 65 | } |
| 66 | var out []ConfigEntry |
| 67 | if err := json.Unmarshal(js, &out); err != nil { |
| 68 | return nil, fmt.Errorf("relay: CARLOS_RELAY is not a JSON array: %w", err) |
| 69 | } |
| 70 | return out, nil |
| 71 | } |
| 72 | |
amadan