| 1 | package calls |
| 2 | |
| 3 | import ( |
| 4 | "crypto/hmac" |
| 5 | "crypto/sha256" |
| 6 | "encoding/base64" |
| 7 | "encoding/hex" |
| 8 | "net/http" |
| 9 | "strconv" |
| 10 | "strings" |
| 11 | "time" |
| 12 | ) |
| 13 | |
| 14 | const joinCookieName = "calls_join" |
| 15 | |
| 16 | // joinCookie tells POST /signin which live link this browser followed. |
| 17 | // It carries the token's hash, not the token, so a cookie leak is not a |
| 18 | // link leak, and it is signed under the instance key so it cannot be |
| 19 | // forged. Its only job is that one hand-off (spec §3.2). |
| 20 | type joinCookie struct { |
| 21 | TokenHash string |
| 22 | Expires time.Time |
| 23 | } |
| 24 | |
| 25 | func (a *app) joinMAC(payload string) string { |
| 26 | mac := hmac.New(sha256.New, []byte("calls/join\x00"+a.cfg.instanceKey)) |
| 27 | mac.Write([]byte(payload)) |
| 28 | return hex.EncodeToString(mac.Sum(nil)) |
| 29 | } |
| 30 | |
| 31 | func (a *app) setJoinCookie(w http.ResponseWriter, tokenHash string) { |
| 32 | exp := a.store.now().Add(pendingLife) |
| 33 | payload := tokenHash + "|" + strconv.FormatInt(exp.Unix(), 10) |
| 34 | value := base64.RawURLEncoding.EncodeToString([]byte(payload)) + "." + a.joinMAC(payload) |
| 35 | http.SetCookie(w, &http.Cookie{ |
| 36 | Name: joinCookieName, Value: value, Path: "/", HttpOnly: true, |
| 37 | Secure: strings.HasPrefix(a.cfg.Origin, "https://"), SameSite: http.SameSiteLaxMode, |
| 38 | MaxAge: int(pendingLife.Seconds()), |
| 39 | }) |
| 40 | } |
| 41 | |
| 42 | func (a *app) clearJoinCookie(w http.ResponseWriter) { |
| 43 | http.SetCookie(w, &http.Cookie{Name: joinCookieName, Value: "", Path: "/", MaxAge: -1, HttpOnly: true}) |
| 44 | } |
| 45 | |
| 46 | func (a *app) readJoinCookie(r *http.Request) (joinCookie, bool) { |
| 47 | ck, err := r.Cookie(joinCookieName) |
| 48 | if err != nil { |
| 49 | return joinCookie{}, false |
| 50 | } |
| 51 | parts := strings.SplitN(ck.Value, ".", 2) |
| 52 | if len(parts) != 2 { |
| 53 | return joinCookie{}, false |
| 54 | } |
| 55 | raw, err := base64.RawURLEncoding.DecodeString(parts[0]) |
| 56 | if err != nil { |
| 57 | return joinCookie{}, false |
| 58 | } |
| 59 | payload := string(raw) |
| 60 | if !hmac.Equal([]byte(a.joinMAC(payload)), []byte(parts[1])) { |
| 61 | return joinCookie{}, false |
| 62 | } |
| 63 | hash, expStr, ok := strings.Cut(payload, "|") |
| 64 | if !ok || len(hash) != 64 { |
| 65 | return joinCookie{}, false |
| 66 | } |
| 67 | exp, err := strconv.ParseInt(expStr, 10, 64) |
| 68 | if err != nil { |
| 69 | return joinCookie{}, false |
| 70 | } |
| 71 | c := joinCookie{TokenHash: hash, Expires: time.Unix(exp, 0)} |
| 72 | if !c.Expires.After(a.store.now()) { |
| 73 | return joinCookie{}, false |
| 74 | } |
| 75 | return c, true |
| 76 | } |
| 77 | |
amadan