package dtls import ( "context" "crypto/rand" "github.com/pion/dtls/v2/pkg/crypto/elliptic" "github.com/pion/dtls/v2/pkg/protocol" "github.com/pion/dtls/v2/pkg/protocol/alert" "github.com/pion/dtls/v2/pkg/protocol/extension" "github.com/pion/dtls/v2/pkg/protocol/handshake" ) func flight0Parse(ctx context.Context, c flightConn, state *State, cache *handshakeCache, cfg *handshakeConfig) (flightVal, *alert.Alert, error) { seq, msgs, ok := cache.fullPullMap(0, handshakeCachePullRule{handshake.TypeClientHello, cfg.initialEpoch, true, false}, ) if !ok { // No valid message received. Keep reading return 0, nil, nil } state.handshakeRecvSequence = seq var clientHello *handshake.MessageClientHello // Validate type if clientHello, ok = msgs[handshake.TypeClientHello].(*handshake.MessageClientHello); !ok { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InternalError}, nil } if !clientHello.Version.Equal(protocol.Version1_2) { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.ProtocolVersion}, errUnsupportedProtocolVersion } state.remoteRandom = clientHello.Random cipherSuites := []CipherSuite{} for _, id := range clientHello.CipherSuiteIDs { if c := cipherSuiteForID(CipherSuiteID(id), cfg.customCipherSuites); c != nil { cipherSuites = append(cipherSuites, c) } } if state.cipherSuite, ok = findMatchingCipherSuite(cipherSuites, cfg.localCipherSuites); !ok { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errCipherSuiteNoIntersection } for _, val := range clientHello.Extensions { switch e := val.(type) { case *extension.SupportedEllipticCurves: if len(e.EllipticCurves) == 0 { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errNoSupportedEllipticCurves } state.namedCurve = e.EllipticCurves[0] case *extension.UseSRTP: profile, ok := findMatchingSRTPProfile(e.ProtectionProfiles, cfg.localSRTPProtectionProfiles) if !ok { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errServerNoMatchingSRTPProfile } state.srtpProtectionProfile = profile case *extension.UseExtendedMasterSecret: if cfg.extendedMasterSecret != DisableExtendedMasterSecret { state.extendedMasterSecret = true } case *extension.ServerName: state.serverName = e.ServerName // remote server name case *extension.ALPN: state.peerSupportedProtocols = e.ProtocolNameList } } if cfg.extendedMasterSecret == RequireExtendedMasterSecret && !state.extendedMasterSecret { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, errServerRequiredButNoClientEMS } if state.localKeypair == nil { var err error state.localKeypair, err = elliptic.GenerateKeypair(state.namedCurve) if err != nil { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.IllegalParameter}, err } } return handleHelloResume(clientHello.SessionID, state, cfg, flight2) } func handleHelloResume(sessionID []byte, state *State, cfg *handshakeConfig, next flightVal) (flightVal, *alert.Alert, error) { if len(sessionID) > 0 && cfg.sessionStore != nil { if s, err := cfg.sessionStore.Get(sessionID); err != nil { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InternalError}, err } else if s.ID != nil { cfg.log.Tracef("[handshake] resume session: %x", sessionID) state.SessionID = sessionID state.masterSecret = s.Secret if err := state.initCipherSuite(); err != nil { return 0, &alert.Alert{Level: alert.Fatal, Description: alert.InternalError}, err } clientRandom := state.localRandom.MarshalFixed() cfg.writeKeyLog(keyLogLabelTLS12, clientRandom[:], state.masterSecret) return flight4b, nil, nil } } return next, nil, nil } func flight0Generate(c flightConn, state *State, cache *handshakeCache, cfg *handshakeConfig) ([]*packet, *alert.Alert, error) { // Initialize state.cookie = make([]byte, cookieLength) if _, err := rand.Read(state.cookie); err != nil { return nil, nil, err } var zeroEpoch uint16 state.localEpoch.Store(zeroEpoch) state.remoteEpoch.Store(zeroEpoch) state.namedCurve = defaultNamedCurve if err := state.localRandom.Populate(); err != nil { return nil, nil, err } return nil, nil, nil }