| 1 | package docs |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "encoding/base64" |
| 6 | "encoding/json" |
| 7 | "math" |
| 8 | "net/http" |
| 9 | |
| 10 | "amadan.net/oficina/home/handoff" |
| 11 | ) |
| 12 | |
| 13 | const homeReturnCookie = "__Host-oficina-docs-home-return" |
| 14 | const homeReturnLimit = 4096 |
| 15 | |
| 16 | type homeReturnIntent struct { |
| 17 | Path string `json:"path"` |
| 18 | Issued int64 `json:"issued"` |
| 19 | Expires int64 `json:"expires"` |
| 20 | } |
| 21 | |
| 22 | // Resource navigation is separate from the fixed-action local reauth marker. |
| 23 | // Neither cookie authorizes linking or access to the requested document. |
| 24 | func (n *localLinkNavigation) rememberReturn(w http.ResponseWriter, path string) bool { |
| 25 | if !handoff.SafePath(path) { |
| 26 | path = "/" |
| 27 | } |
| 28 | now := n.now().Unix() |
| 29 | if now <= 0 || now > math.MaxInt64-localLinkNavigationLifetime { |
| 30 | return false |
| 31 | } |
| 32 | raw, err := json.Marshal(homeReturnIntent{path, now, now + localLinkNavigationLifetime}) |
| 33 | if err != nil { |
| 34 | return false |
| 35 | } |
| 36 | sealed, err := n.sealer.Seal("docs.home-return.v1:"+n.origin, raw) |
| 37 | if err != nil { |
| 38 | return false |
| 39 | } |
| 40 | value := base64.RawURLEncoding.EncodeToString(sealed) |
| 41 | if len(value) > homeReturnLimit { |
| 42 | return false |
| 43 | } |
| 44 | localNavigationCookie(w, homeReturnCookie, value, int(localLinkNavigationLifetime)) |
| 45 | return true |
| 46 | } |
| 47 | |
| 48 | func (n *localLinkNavigation) returnPath(r *http.Request) string { |
| 49 | value := "" |
| 50 | if cookieCount(r, homeReturnCookie) != 1 { |
| 51 | return "/" |
| 52 | } |
| 53 | cookie, err := r.Cookie(homeReturnCookie) |
| 54 | if err != nil { |
| 55 | return "/" |
| 56 | } |
| 57 | value = cookie.Value |
| 58 | if value == "" || len(value) > homeReturnLimit { |
| 59 | return "/" |
| 60 | } |
| 61 | sealed, err := base64.RawURLEncoding.Strict().DecodeString(value) |
| 62 | if err != nil || base64.RawURLEncoding.EncodeToString(sealed) != value { |
| 63 | return "/" |
| 64 | } |
| 65 | raw, err := n.sealer.Open("docs.home-return.v1:"+n.origin, sealed) |
| 66 | if err != nil || len(raw) > homeReturnLimit { |
| 67 | return "/" |
| 68 | } |
| 69 | var intent homeReturnIntent |
| 70 | if json.Unmarshal(raw, &intent) != nil { |
| 71 | return "/" |
| 72 | } |
| 73 | canonical, _ := json.Marshal(intent) |
| 74 | now := n.now().Unix() |
| 75 | if !bytes.Equal(raw, canonical) || intent.Issued <= 0 || intent.Issued > now || intent.Expires <= now || intent.Expires <= intent.Issued || intent.Expires-intent.Issued > localLinkNavigationLifetime || !handoff.SafePath(intent.Path) { |
| 76 | return "/" |
| 77 | } |
| 78 | return intent.Path |
| 79 | } |
| 80 | |
amadan