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* Copyright 2011 The WebRTC Project Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <memory>
#include <string>
#include <vector>
#include "api/crypto/crypto_options.h"
#include "p2p/base/dtls_transport_internal.h"
#include "p2p/base/ice_transport_internal.h"
#include "rtc_base/buffer.h"
#include "rtc_base/buffer_queue.h"
#include "rtc_base/constructor_magic.h"
#include "rtc_base/ssl_stream_adapter.h"
#include "rtc_base/stream.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/thread_checker.h"
namespace rtc {
class PacketTransportInternal;
namespace cricket {
// A bridge between a packet-oriented/transport-type interface on
// the bottom and a StreamInterface on the top.
class StreamInterfaceChannel : public rtc::StreamInterface {
explicit StreamInterfaceChannel(IceTransportInternal* ice_transport);
// Push in a packet; this gets pulled out from Read().
bool OnPacketReceived(const char* data, size_t size);
// Implementations of StreamInterface
rtc::StreamState GetState() const override;
void Close() override;
rtc::StreamResult Read(void* buffer,
size_t buffer_len,
size_t* read,
int* error) override;
rtc::StreamResult Write(const void* data,
size_t data_len,
size_t* written,
int* error) override;
IceTransportInternal* ice_transport_; // owned by DtlsTransport
rtc::StreamState state_;
rtc::BufferQueue packets_;
// This class provides a DTLS SSLStreamAdapter inside a TransportChannel-style
// packet-based interface, wrapping an existing TransportChannel instance
// (e.g a P2PTransportChannel)
// Here's the way this works:
// DtlsTransport {
// SSLStreamAdapter* dtls_ {
// StreamInterfaceChannel downward_ {
// IceTransportInternal* ice_transport_;
// }
// }
// }
// - Data which comes into DtlsTransport from the underlying
// ice_transport_ via OnReadPacket() is checked for whether it is DTLS
// or not, and if it is, is passed to DtlsTransport::HandleDtlsPacket,
// which pushes it into to downward_. dtls_ is listening for events on
// downward_, so it immediately calls downward_->Read().
// - Data written to DtlsTransport is passed either to downward_ or directly
// to ice_transport_, depending on whether DTLS is negotiated and whether
// the flags include PF_SRTP_BYPASS
// - The SSLStreamAdapter writes to downward_->Write() which translates it
// into packet writes on ice_transport_.
// This class is not thread safe; all methods must be called on the same thread
// as the constructor.
class DtlsTransport : public DtlsTransportInternal {
// |ice_transport| is the ICE transport this DTLS transport is wrapping. It
// must outlive this DTLS transport.
// |crypto_options| are the options used for the DTLS handshake. This affects
// whether GCM crypto suites are negotiated.
// |event_log| is an optional RtcEventLog for logging state changes. It should
// outlive the DtlsTransport.
explicit DtlsTransport(IceTransportInternal* ice_transport,
const webrtc::CryptoOptions& crypto_options,
webrtc::RtcEventLog* event_log);
~DtlsTransport() override;
const webrtc::CryptoOptions& crypto_options() const override;
DtlsTransportState dtls_state() const override;
const std::string& transport_name() const override;
int component() const override;
// DTLS is active if a local certificate was set. Otherwise this acts in a
// "passthrough" mode, sending packets directly through the underlying ICE
// transport.
// TODO(deadbeef): Remove this weirdness, and handle it in the upper layers.
bool IsDtlsActive() const override;
// SetLocalCertificate is what makes DTLS active. It must be called before
// SetRemoteFinterprint.
// TODO(deadbeef): Once DtlsTransport no longer has the concept of being
// "active" or not (acting as a passthrough if not active), just require this
// certificate on construction or "Start".
bool SetLocalCertificate(
const rtc::scoped_refptr<rtc::RTCCertificate>& certificate) override;
rtc::scoped_refptr<rtc::RTCCertificate> GetLocalCertificate() const override;
// SetRemoteFingerprint must be called after SetLocalCertificate, and any
// other methods like SetDtlsRole. It's what triggers the actual DTLS setup.
// TODO(deadbeef): Rename to "Start" like in ORTC?
bool SetRemoteFingerprint(const std::string& digest_alg,
const uint8_t* digest,
size_t digest_len) override;
// Called to send a packet (via DTLS, if turned on).
int SendPacket(const char* data,
size_t size,
const rtc::PacketOptions& options,
int flags) override;
bool GetOption(rtc::Socket::Option opt, int* value) override;
bool SetSslMaxProtocolVersion(rtc::SSLProtocolVersion version) override;
// Find out which TLS version was negotiated
bool GetSslVersionBytes(int* version) const override;
// Find out which DTLS-SRTP cipher was negotiated
bool GetSrtpCryptoSuite(int* cipher) override;
bool GetDtlsRole(rtc::SSLRole* role) const override;
bool SetDtlsRole(rtc::SSLRole role) override;
// Find out which DTLS cipher was negotiated
bool GetSslCipherSuite(int* cipher) override;
// Once DTLS has been established, this method retrieves the certificate
// chain in use by the remote peer, for use in external identity
// verification.
std::unique_ptr<rtc::SSLCertChain> GetRemoteSSLCertChain() const override;
// Once DTLS has established (i.e., this ice_transport is writable), this
// method extracts the keys negotiated during the DTLS handshake, for use in
// external encryption. DTLS-SRTP uses this to extract the needed SRTP keys.
// See the SSLStreamAdapter documentation for info on the specific parameters.
bool ExportKeyingMaterial(const std::string& label,
const uint8_t* context,
size_t context_len,
bool use_context,
uint8_t* result,
size_t result_len) override;
IceTransportInternal* ice_transport() override;
// For informational purposes. Tells if the DTLS handshake has finished.
// This may be true even if writable() is false, if the remote fingerprint
// has not yet been verified.
bool IsDtlsConnected();
bool receiving() const override;
bool writable() const override;
int GetError() override;
absl::optional<rtc::NetworkRoute> network_route() const override;
int SetOption(rtc::Socket::Option opt, int value) override;
std::string ToString() const {
const absl::string_view RECEIVING_ABBREV[2] = {"_", "R"};
const absl::string_view WRITABLE_ABBREV[2] = {"_", "W"};
rtc::StringBuilder sb;
sb << "DtlsTransport[" << transport_name_ << "|" << component_ << "|"
<< RECEIVING_ABBREV[receiving()] << WRITABLE_ABBREV[writable()] << "]";
return sb.Release();
void ConnectToIceTransport();
void OnWritableState(rtc::PacketTransportInternal* transport);
void OnReadPacket(rtc::PacketTransportInternal* transport,
const char* data,
size_t size,
const int64_t& packet_time_us,
int flags);
void OnSentPacket(rtc::PacketTransportInternal* transport,
const rtc::SentPacket& sent_packet);
void OnReadyToSend(rtc::PacketTransportInternal* transport);
void OnReceivingState(rtc::PacketTransportInternal* transport);
void OnDtlsEvent(rtc::StreamInterface* stream_, int sig, int err);
void OnNetworkRouteChanged(absl::optional<rtc::NetworkRoute> network_route);
bool SetupDtls();
void MaybeStartDtls();
bool HandleDtlsPacket(const char* data, size_t size);
void OnDtlsHandshakeError(rtc::SSLHandshakeError error);
void ConfigureHandshakeTimeout();
void set_receiving(bool receiving);
void set_writable(bool writable);
// Sets the DTLS state, signaling if necessary.
void set_dtls_state(DtlsTransportState state);
rtc::ThreadChecker thread_checker_;
std::string transport_name_;
int component_;
DtlsTransportState dtls_state_ = DTLS_TRANSPORT_NEW;
// Underlying ice_transport, not owned by this class.
IceTransportInternal* ice_transport_;
std::unique_ptr<rtc::SSLStreamAdapter> dtls_; // The DTLS stream
downward_; // Wrapper for ice_transport_, owned by dtls_.
std::vector<int> srtp_ciphers_; // SRTP ciphers to use with DTLS.
bool dtls_active_ = false;
rtc::scoped_refptr<rtc::RTCCertificate> local_certificate_;
absl::optional<rtc::SSLRole> dtls_role_;
rtc::SSLProtocolVersion ssl_max_version_;
webrtc::CryptoOptions crypto_options_;
rtc::Buffer remote_fingerprint_value_;
std::string remote_fingerprint_algorithm_;
// Cached DTLS ClientHello packet that was received before we started the
// DTLS handshake. This could happen if the hello was received before the
// ice transport became writable, or before a remote fingerprint was received.
rtc::Buffer cached_client_hello_;
bool receiving_ = false;
bool writable_ = false;
webrtc::RtcEventLog* const event_log_;
} // namespace cricket