| 1 | package connect |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "encoding/base64" |
| 6 | "encoding/json" |
| 7 | "math" |
| 8 | "net/http" |
| 9 | "net/url" |
| 10 | "time" |
| 11 | |
| 12 | "amadan.net/oficina/home/handoff" |
| 13 | ) |
| 14 | |
| 15 | const localLinkNavigationCookie = "__Host-oficina-local-link-navigation" |
| 16 | const localLinkNavigationLifetime = int64(600) |
| 17 | const localLinkNavigationLimit = 1024 |
| 18 | const localLinkCompletePath = "/auth/local/complete" |
| 19 | |
| 20 | type localLinkMarker struct { |
| 21 | Version int `json:"v"` |
| 22 | Action string `json:"action"` |
| 23 | Issued int64 `json:"issued"` |
| 24 | Expires int64 `json:"expires"` |
| 25 | } |
| 26 | |
| 27 | type localLinkNavigation struct { |
| 28 | landingPath string |
| 29 | sealer handoff.Sealer |
| 30 | sessionCookie string |
| 31 | readSession func(*http.Request) (*Session, error) |
| 32 | namespace string |
| 33 | fail func(http.ResponseWriter, *http.Request, int) |
| 34 | origin, host string |
| 35 | now func() time.Time |
| 36 | } |
| 37 | |
| 38 | func newLocalLinkNavigation(sealer handoff.Sealer, c RoutesConfig) *localLinkNavigation { |
| 39 | u, err := url.Parse(c.Origin) |
| 40 | if err != nil || u.Scheme != "https" || u.Host == "" || u.User != nil || u.Path != "" || u.RawQuery != "" || u.Fragment != "" || sealer == nil || c.ReadSession == nil { |
| 41 | return nil |
| 42 | } |
| 43 | landing := c.LocalLandingPath |
| 44 | if landing == "" { |
| 45 | landing = "/" |
| 46 | } |
| 47 | if !handoff.SafePath(landing) { |
| 48 | return nil |
| 49 | } |
| 50 | return &localLinkNavigation{landingPath: landing, sealer: sealer, sessionCookie: c.SessionCookie, readSession: c.ReadSession, namespace: c.Namespace, origin: c.Origin, host: u.Host, now: time.Now, fail: func(w http.ResponseWriter, r *http.Request, status int) { c.Render(w, r, "failed", "", status) }} |
| 51 | } |
| 52 | |
| 53 | func localNavigationCookie(w http.ResponseWriter, name, value string, age int) { |
| 54 | http.SetCookie(w, &http.Cookie{Name: name, Value: value, Path: "/", Secure: true, HttpOnly: true, SameSite: http.SameSiteLaxMode, MaxAge: age}) |
| 55 | } |
| 56 | |
| 57 | func (n *localLinkNavigation) purpose() string { |
| 58 | return n.namespace + ".local-link-navigation.v1:" + n.origin |
| 59 | } |
| 60 | |
| 61 | func (n *localLinkNavigation) guard(w http.ResponseWriter, r *http.Request, path string) bool { |
| 62 | w.Header().Set("Cache-Control", "no-store") |
| 63 | if r.Method != http.MethodGet { |
| 64 | w.Header().Set("Allow", http.MethodGet) |
| 65 | n.fail(w, r, http.StatusMethodNotAllowed) |
| 66 | return false |
| 67 | } |
| 68 | if r.Host != n.host || r.URL.Path != path || r.URL.RawQuery != "" { |
| 69 | http.Redirect(w, r, "/", http.StatusSeeOther) |
| 70 | return false |
| 71 | } |
| 72 | return true |
| 73 | } |
| 74 | |
| 75 | // Begin abandons browser pointers to an old link. Rotation and freshness also |
| 76 | // invalidate its binding; clearing cookies does not consume database rows. |
| 77 | // A cross-site top-level GET may abandon a flow, but cannot create a link. |
| 78 | func (n *localLinkNavigation) Begin(w http.ResponseWriter, r *http.Request) { |
| 79 | localNavigationCookie(w, localLinkNavigationCookie, "", -1) |
| 80 | if !n.guard(w, r, "/account/home") { |
| 81 | return |
| 82 | } |
| 83 | localNavigationCookie(w, homeInitCookie, "", -1) |
| 84 | localNavigationCookie(w, homeProofCookie, "", -1) |
| 85 | now := n.now().Unix() |
| 86 | if now <= 0 || now > math.MaxInt64-localLinkNavigationLifetime { |
| 87 | http.Redirect(w, r, "/", http.StatusSeeOther) |
| 88 | return |
| 89 | } |
| 90 | payload, _ := json.Marshal(localLinkMarker{Version: 1, Action: "link-start", Issued: now, Expires: now + localLinkNavigationLifetime}) |
| 91 | sealed, err := n.sealer.Seal(n.purpose(), payload) |
| 92 | if err != nil { |
| 93 | n.fail(w, r, http.StatusServiceUnavailable) |
| 94 | return |
| 95 | } |
| 96 | encoded := base64.RawURLEncoding.EncodeToString(sealed) |
| 97 | if len(encoded) > localLinkNavigationLimit { |
| 98 | n.fail(w, r, http.StatusServiceUnavailable) |
| 99 | return |
| 100 | } |
| 101 | localNavigationCookie(w, localLinkNavigationCookie, encoded, int(localLinkNavigationLifetime)) |
| 102 | http.Redirect(w, r, "/signin/local", http.StatusSeeOther) |
| 103 | } |
| 104 | |
| 105 | func (n *localLinkNavigation) marker(r *http.Request, now int64) bool { |
| 106 | value := "" |
| 107 | count := 0 |
| 108 | for _, c := range r.Cookies() { |
| 109 | if c.Name == localLinkNavigationCookie { |
| 110 | count++ |
| 111 | value = c.Value |
| 112 | } |
| 113 | } |
| 114 | if count != 1 || value == "" || len(value) > localLinkNavigationLimit { |
| 115 | return false |
| 116 | } |
| 117 | sealed, err := base64.RawURLEncoding.Strict().DecodeString(value) |
| 118 | if err != nil || base64.RawURLEncoding.EncodeToString(sealed) != value { |
| 119 | return false |
| 120 | } |
| 121 | payload, err := n.sealer.Open(n.purpose(), sealed) |
| 122 | if err != nil || len(payload) > localLinkNavigationLimit { |
| 123 | return false |
| 124 | } |
| 125 | var marker localLinkMarker |
| 126 | if json.Unmarshal(payload, &marker) != nil { |
| 127 | return false |
| 128 | } |
| 129 | // Only this helper writes the payload. Exact re-encoding excludes duplicate |
| 130 | // and unknown fields, alternate numbers, and any trailing JSON value. |
| 131 | canonical, _ := json.Marshal(marker) |
| 132 | if !bytes.Equal(payload, canonical) { |
| 133 | return false |
| 134 | } |
| 135 | return marker.Version == 1 && marker.Action == "link-start" && marker.Issued > 0 && marker.Issued <= now && now < marker.Expires && marker.Expires > marker.Issued && marker.Expires-marker.Issued <= localLinkNavigationLifetime |
| 136 | } |
| 137 | |
| 138 | // Complete reads the newly presented session after local verification. It |
| 139 | // cannot initiate or confirm linking, and never treats a Home mint as local |
| 140 | // proof. A copied marker can at most repeat navigation to the same page. |
| 141 | func (n *localLinkNavigation) Complete(w http.ResponseWriter, r *http.Request) { |
| 142 | localNavigationCookie(w, localLinkNavigationCookie, "", -1) |
| 143 | if !n.guard(w, r, localLinkCompletePath) { |
| 144 | return |
| 145 | } |
| 146 | now := n.now() |
| 147 | target := n.landingPath |
| 148 | if n.marker(r, now.Unix()) { |
| 149 | count := 0 |
| 150 | for _, c := range r.Cookies() { |
| 151 | if c.Name == n.sessionCookie { |
| 152 | count++ |
| 153 | } |
| 154 | } |
| 155 | if count == 1 { |
| 156 | if session, err := n.readSession(r); err == nil && session != nil { |
| 157 | if _, fresh := FreshLocal(*session, now); fresh { |
| 158 | target = "/account/home" |
| 159 | } |
| 160 | } |
| 161 | } |
| 162 | } |
| 163 | http.Redirect(w, r, target, http.StatusSeeOther) |
| 164 | } |
| 165 | |
amadan