package webserver import ( "bytes" "crypto/aes" "crypto/cipher" crand "crypto/rand" "encoding/base64" "errors" "fmt" "io" "log" "net" "net/http" "net/url" "path" "strings" "github.com/pion/webrtc/v3" "github.com/jech/galene/group" "github.com/jech/galene/ice" "github.com/jech/galene/rtpconn" ) var idSecret []byte var idCipher cipher.Block func init() { idSecret = make([]byte, 16) _, err := crand.Read(idSecret) if err != nil { log.Fatalf("crand.Read: %v", err) } idCipher, err = aes.NewCipher(idSecret) if err != nil { log.Fatalf("NewCipher: %v", err) } } func newId() string { b := make([]byte, idCipher.BlockSize()) crand.Read(b) return base64.RawURLEncoding.EncodeToString(b) } // we obfuscate ids to avoid exposing the WHIP session URL func obfuscate(id string) (string, error) { v, err := base64.RawURLEncoding.DecodeString(id) if err != nil { return "", err } if len(v) != idCipher.BlockSize() { return "", errors.New("bad length") } idCipher.Encrypt(v, v) return base64.RawURLEncoding.EncodeToString(v), nil } func deobfuscate(id string) (string, error) { v, err := base64.RawURLEncoding.DecodeString(id) if err != nil { return "", err } if len(v) != idCipher.BlockSize() { return "", errors.New("bad length") } idCipher.Decrypt(v, v) return base64.RawURLEncoding.EncodeToString(v), nil } func canPresent(perms []string) bool { for _, p := range perms { if p == "present" { return true } } return false } func parseBearerToken(auth string) string { auths := strings.Split(auth, ",") for _, a := range auths { a = strings.Trim(a, " \t") s := strings.Split(a, " ") if len(s) == 2 && strings.EqualFold(s[0], "bearer") { return s[1] } } return "" } var iceServerReplacer = strings.NewReplacer(`\`, `\\`, `"`, `\"`) func formatICEServer(server webrtc.ICEServer, u string) string { quote := func(s string) string { return iceServerReplacer.Replace(s) } uu, err := url.Parse(u) if err != nil { return "" } if strings.EqualFold(uu.Scheme, "stun") { return fmt.Sprintf("<%v>; rel=\"ice-server\"", u) } else if strings.EqualFold(uu.Scheme, "turn") || strings.EqualFold(uu.Scheme, "turns") { pw, ok := server.Credential.(string) if !ok { return "" } return fmt.Sprintf("<%v>; rel=\"ice-server\"; "+ "username=\"%v\"; "+ "credential=\"%v\"; "+ "credential-type=\"%v\"", u, quote(server.Username), quote(pw), quote(server.CredentialType.String())) } return "" } func whipICEServers(w http.ResponseWriter) { conf := ice.ICEConfiguration() for _, server := range conf.ICEServers { for _, u := range server.URLs { v := formatICEServer(server, u) if v != "" { w.Header().Add("Link", v) } } } } const sdpLimit = 1024 * 1024 func whipEndpointHandler(w http.ResponseWriter, r *http.Request) { if redirect(w, r) { return } pth, kind, pthid := splitPath(r.URL.Path) if kind != ".whip" || pthid != "" { http.Error(w, "Internal server error", http.StatusInternalServerError) return } name := parseGroupName("/group/", pth) if name == "" { notFound(w) return } g, err := group.Add(name, nil) if err != nil { httpError(w, err) return } conf, err := group.GetConfiguration() if err != nil { httpError(w, err) return } if conf.PublicServer { w.Header().Set("Access-Control-Allow-Origin", "*") } if r.Method == "OPTIONS" { w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, POST") w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type", ) w.Header().Set("Access-Control-Expose-Headers", "Link") whipICEServers(w) return } if r.Method != "POST" { methodNotAllowed(w, "OPTIONS", "POST") return } ctype := r.Header.Get("content-type") if !strings.EqualFold(ctype, "application/sdp") { http.Error(w, "bad content type", http.StatusBadRequest) return } body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, sdpLimit)) if err != nil { httpError(w, err) return } token := parseBearerToken(r.Header.Get("Authorization")) whip := "whip" creds := group.ClientCredentials{ Username: &whip, Token: token, } id := newId() obfuscated, err := obfuscate(id) if err != nil { httpError(w, err) return } var addr net.Addr tcpaddr, err := net.ResolveTCPAddr("tcp", r.RemoteAddr) if err != nil { log.Printf("ResolveTCPAddr: %v", err) } else { addr = tcpaddr } c := rtpconn.NewWhipClient(g, id, token, addr) _, err = group.AddClient(g.Name(), c, creds) if err != nil { log.Printf("WHIP: %v", err) httpError(w, err) return } if !canPresent(c.Permissions()) { group.DelClient(c) http.Error(w, "Forbidden", http.StatusForbidden) return } answer, err := c.NewConnection(r.Context(), body) if err != nil { group.DelClient(c) log.Printf("WHIP offer: %v", err) httpError(w, err) return } w.Header().Set("Location", path.Join(r.URL.Path, obfuscated)) w.Header().Set("Access-Control-Expose-Headers", "Location, Content-Type, Link") whipICEServers(w) w.Header().Set("Content-Type", "application/sdp") w.WriteHeader(http.StatusCreated) w.Write(answer) return } func whipResourceHandler(w http.ResponseWriter, r *http.Request) { pth, kind, rest := splitPath(r.URL.Path) if kind != ".whip" || rest == "" { http.Error(w, "Internal server error", http.StatusInternalServerError) return } id, err := deobfuscate(rest[1:]) if err != nil { httpError(w, err) return } name := parseGroupName("/group/", pth) if name == "" { notFound(w) return } g := group.Get(name) if g == nil { notFound(w) return } cc := g.GetClient(id) if cc == nil { notFound(w) return } c, ok := cc.(*rtpconn.WhipClient) if !ok { notFound(w) return } if t := c.Token(); t != "" { token := parseBearerToken(r.Header.Get("Authorization")) if token != t { http.Error(w, "Forbidden", http.StatusForbidden) return } } conf, err := group.GetConfiguration() if err != nil { httpError(w, err) return } if conf.PublicServer { w.Header().Set("Access-Control-Allow-Origin", "*") } if r.Method == "OPTIONS" { w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, DELETE, PATCH", ) w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type", ) return } if r.Method == "DELETE" { c.Close() return } if r.Method != "PATCH" { methodNotAllowed(w, "OPTIONS", "DELETE", "PATCH") return } ctype := r.Header.Get("content-type") if !strings.EqualFold(ctype, "application/trickle-ice-sdpfrag") { http.Error(w, "bad content type", http.StatusBadRequest) return } body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, sdpLimit)) if err != nil { httpError(w, err) return } if len(body) < 2 { http.Error(w, "SDP truncated", http.StatusBadRequest) return } // RFC 8840 lines := bytes.Split(body, []byte{'\n'}) mLineIndex := -1 var mid, ufrag []byte for _, l := range lines { l = bytes.TrimRight(l, " \r") if bytes.HasPrefix(l, []byte("a=ice-ufrag:")) { ufrag = l[len("a=ice-ufrag:"):] } else if bytes.HasPrefix(l, []byte("m=")) { mLineIndex++ mid = nil } else if bytes.HasPrefix(l, []byte("a=mid:")) { mid = l[len("a=mid:"):] } else if bytes.HasPrefix(l, []byte("a=candidate:")) { init := webrtc.ICECandidateInit{ Candidate: string(l[2:]), } if len(mid) > 0 { s := string(mid) init.SDPMid = &s } if mLineIndex >= 0 { i := uint16(mLineIndex) init.SDPMLineIndex = &i } if len(ufrag) > 0 { s := string(ufrag) init.UsernameFragment = &s } err := c.GotICECandidate(init) if err != nil { log.Printf("WHIP candidate: %v", err) } } } w.WriteHeader(http.StatusNoContent) return }