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322 lines
11 KiB
322 lines
11 KiB
/*
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* Copyright 2017 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "pc/dtls_srtp_transport.h"
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#include <string.h>
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#include <string>
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#include <utility>
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#include "rtc_base/checks.h"
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#include "rtc_base/logging.h"
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#include "rtc_base/ssl_stream_adapter.h"
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namespace {
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// Value specified in RFC 5764.
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static const char kDtlsSrtpExporterLabel[] = "EXTRACTOR-dtls_srtp";
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} // namespace
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namespace webrtc {
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DtlsSrtpTransport::DtlsSrtpTransport(bool rtcp_mux_enabled)
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: SrtpTransport(rtcp_mux_enabled) {}
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void DtlsSrtpTransport::SetDtlsTransports(
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cricket::DtlsTransportInternal* rtp_dtls_transport,
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cricket::DtlsTransportInternal* rtcp_dtls_transport) {
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// Transport names should be the same.
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if (rtp_dtls_transport && rtcp_dtls_transport) {
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RTC_DCHECK(rtp_dtls_transport->transport_name() ==
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rtcp_dtls_transport->transport_name());
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}
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// When using DTLS-SRTP, we must reset the SrtpTransport every time the
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// DtlsTransport changes and wait until the DTLS handshake is complete to set
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// the newly negotiated parameters.
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// If |active_reset_srtp_params_| is true, intentionally reset the SRTP
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// parameter even though the DtlsTransport may not change.
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if (IsSrtpActive() && (rtp_dtls_transport != rtp_dtls_transport_ ||
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active_reset_srtp_params_)) {
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ResetParams();
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}
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const std::string transport_name =
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rtp_dtls_transport ? rtp_dtls_transport->transport_name() : "null";
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if (rtcp_dtls_transport && rtcp_dtls_transport != rtcp_dtls_transport_) {
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// This would only be possible if using BUNDLE but not rtcp-mux, which isn't
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// allowed according to the BUNDLE spec.
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RTC_CHECK(!(IsSrtpActive()))
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<< "Setting RTCP for DTLS/SRTP after the DTLS is active "
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"should never happen.";
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}
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RTC_LOG(LS_INFO) << "Setting RTCP Transport on " << transport_name
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<< " transport " << rtcp_dtls_transport;
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SetRtcpDtlsTransport(rtcp_dtls_transport);
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SetRtcpPacketTransport(rtcp_dtls_transport);
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RTC_LOG(LS_INFO) << "Setting RTP Transport on " << transport_name
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<< " transport " << rtp_dtls_transport;
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SetRtpDtlsTransport(rtp_dtls_transport);
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SetRtpPacketTransport(rtp_dtls_transport);
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MaybeSetupDtlsSrtp();
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}
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void DtlsSrtpTransport::SetRtcpMuxEnabled(bool enable) {
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SrtpTransport::SetRtcpMuxEnabled(enable);
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if (enable) {
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MaybeSetupDtlsSrtp();
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}
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}
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void DtlsSrtpTransport::UpdateSendEncryptedHeaderExtensionIds(
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const std::vector<int>& send_extension_ids) {
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if (send_extension_ids_ == send_extension_ids) {
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return;
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}
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send_extension_ids_.emplace(send_extension_ids);
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if (DtlsHandshakeCompleted()) {
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// Reset the crypto parameters to update the send extension IDs.
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SetupRtpDtlsSrtp();
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}
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}
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void DtlsSrtpTransport::UpdateRecvEncryptedHeaderExtensionIds(
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const std::vector<int>& recv_extension_ids) {
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if (recv_extension_ids_ == recv_extension_ids) {
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return;
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}
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recv_extension_ids_.emplace(recv_extension_ids);
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if (DtlsHandshakeCompleted()) {
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// Reset the crypto parameters to update the receive extension IDs.
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SetupRtpDtlsSrtp();
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}
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}
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bool DtlsSrtpTransport::IsDtlsActive() {
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auto rtcp_dtls_transport =
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rtcp_mux_enabled() ? nullptr : rtcp_dtls_transport_;
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return (rtp_dtls_transport_ && rtp_dtls_transport_->IsDtlsActive() &&
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(!rtcp_dtls_transport || rtcp_dtls_transport->IsDtlsActive()));
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}
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bool DtlsSrtpTransport::IsDtlsConnected() {
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auto rtcp_dtls_transport =
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rtcp_mux_enabled() ? nullptr : rtcp_dtls_transport_;
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return (rtp_dtls_transport_ &&
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rtp_dtls_transport_->dtls_state() ==
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cricket::DTLS_TRANSPORT_CONNECTED &&
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(!rtcp_dtls_transport || rtcp_dtls_transport->dtls_state() ==
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cricket::DTLS_TRANSPORT_CONNECTED));
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}
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bool DtlsSrtpTransport::IsDtlsWritable() {
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auto rtcp_packet_transport =
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rtcp_mux_enabled() ? nullptr : rtcp_dtls_transport_;
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return rtp_dtls_transport_ && rtp_dtls_transport_->writable() &&
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(!rtcp_packet_transport || rtcp_packet_transport->writable());
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}
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bool DtlsSrtpTransport::DtlsHandshakeCompleted() {
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return IsDtlsActive() && IsDtlsConnected();
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}
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void DtlsSrtpTransport::MaybeSetupDtlsSrtp() {
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if (IsSrtpActive() || !IsDtlsWritable()) {
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return;
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}
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SetupRtpDtlsSrtp();
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if (!rtcp_mux_enabled() && rtcp_dtls_transport_) {
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SetupRtcpDtlsSrtp();
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}
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}
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void DtlsSrtpTransport::SetupRtpDtlsSrtp() {
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// Use an empty encrypted header extension ID vector if not set. This could
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// happen when the DTLS handshake is completed before processing the
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// Offer/Answer which contains the encrypted header extension IDs.
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std::vector<int> send_extension_ids;
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std::vector<int> recv_extension_ids;
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if (send_extension_ids_) {
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send_extension_ids = *send_extension_ids_;
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}
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if (recv_extension_ids_) {
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recv_extension_ids = *recv_extension_ids_;
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}
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int selected_crypto_suite;
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rtc::ZeroOnFreeBuffer<unsigned char> send_key;
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rtc::ZeroOnFreeBuffer<unsigned char> recv_key;
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if (!ExtractParams(rtp_dtls_transport_, &selected_crypto_suite, &send_key,
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&recv_key) ||
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!SetRtpParams(selected_crypto_suite, &send_key[0],
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static_cast<int>(send_key.size()), send_extension_ids,
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selected_crypto_suite, &recv_key[0],
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static_cast<int>(recv_key.size()), recv_extension_ids)) {
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SignalDtlsSrtpSetupFailure(this, /*rtcp=*/false);
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RTC_LOG(LS_WARNING) << "DTLS-SRTP key installation for RTP failed";
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}
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}
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void DtlsSrtpTransport::SetupRtcpDtlsSrtp() {
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// Return if the DTLS-SRTP is active because the encrypted header extension
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// IDs don't need to be updated for RTCP and the crypto params don't need to
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// be reset.
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if (IsSrtpActive()) {
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return;
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}
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std::vector<int> send_extension_ids;
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std::vector<int> recv_extension_ids;
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if (send_extension_ids_) {
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send_extension_ids = *send_extension_ids_;
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}
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if (recv_extension_ids_) {
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recv_extension_ids = *recv_extension_ids_;
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}
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int selected_crypto_suite;
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rtc::ZeroOnFreeBuffer<unsigned char> rtcp_send_key;
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rtc::ZeroOnFreeBuffer<unsigned char> rtcp_recv_key;
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if (!ExtractParams(rtcp_dtls_transport_, &selected_crypto_suite,
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&rtcp_send_key, &rtcp_recv_key) ||
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!SetRtcpParams(selected_crypto_suite, &rtcp_send_key[0],
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static_cast<int>(rtcp_send_key.size()), send_extension_ids,
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selected_crypto_suite, &rtcp_recv_key[0],
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static_cast<int>(rtcp_recv_key.size()),
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recv_extension_ids)) {
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SignalDtlsSrtpSetupFailure(this, /*rtcp=*/true);
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RTC_LOG(LS_WARNING) << "DTLS-SRTP key installation for RTCP failed";
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}
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}
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bool DtlsSrtpTransport::ExtractParams(
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cricket::DtlsTransportInternal* dtls_transport,
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int* selected_crypto_suite,
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rtc::ZeroOnFreeBuffer<unsigned char>* send_key,
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rtc::ZeroOnFreeBuffer<unsigned char>* recv_key) {
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if (!dtls_transport || !dtls_transport->IsDtlsActive()) {
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return false;
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}
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if (!dtls_transport->GetSrtpCryptoSuite(selected_crypto_suite)) {
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RTC_LOG(LS_ERROR) << "No DTLS-SRTP selected crypto suite";
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return false;
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}
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RTC_LOG(LS_INFO) << "Extracting keys from transport: "
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<< dtls_transport->transport_name();
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int key_len;
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int salt_len;
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if (!rtc::GetSrtpKeyAndSaltLengths((*selected_crypto_suite), &key_len,
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&salt_len)) {
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RTC_LOG(LS_ERROR) << "Unknown DTLS-SRTP crypto suite"
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<< selected_crypto_suite;
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return false;
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}
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// OK, we're now doing DTLS (RFC 5764)
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rtc::ZeroOnFreeBuffer<unsigned char> dtls_buffer(key_len * 2 + salt_len * 2);
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// RFC 5705 exporter using the RFC 5764 parameters
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if (!dtls_transport->ExportKeyingMaterial(kDtlsSrtpExporterLabel, NULL, 0,
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false, &dtls_buffer[0],
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dtls_buffer.size())) {
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RTC_LOG(LS_WARNING) << "DTLS-SRTP key export failed";
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RTC_NOTREACHED(); // This should never happen
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return false;
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}
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// Sync up the keys with the DTLS-SRTP interface
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rtc::ZeroOnFreeBuffer<unsigned char> client_write_key(key_len + salt_len);
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rtc::ZeroOnFreeBuffer<unsigned char> server_write_key(key_len + salt_len);
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size_t offset = 0;
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memcpy(&client_write_key[0], &dtls_buffer[offset], key_len);
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offset += key_len;
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memcpy(&server_write_key[0], &dtls_buffer[offset], key_len);
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offset += key_len;
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memcpy(&client_write_key[key_len], &dtls_buffer[offset], salt_len);
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offset += salt_len;
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memcpy(&server_write_key[key_len], &dtls_buffer[offset], salt_len);
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rtc::SSLRole role;
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if (!dtls_transport->GetDtlsRole(&role)) {
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RTC_LOG(LS_WARNING) << "Failed to get the DTLS role.";
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return false;
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}
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if (role == rtc::SSL_SERVER) {
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*send_key = std::move(server_write_key);
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*recv_key = std::move(client_write_key);
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} else {
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*send_key = std::move(client_write_key);
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*recv_key = std::move(server_write_key);
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}
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return true;
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}
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void DtlsSrtpTransport::SetDtlsTransport(
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cricket::DtlsTransportInternal* new_dtls_transport,
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cricket::DtlsTransportInternal** old_dtls_transport) {
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if (*old_dtls_transport == new_dtls_transport) {
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return;
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}
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if (*old_dtls_transport) {
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(*old_dtls_transport)->SignalDtlsState.disconnect(this);
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}
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*old_dtls_transport = new_dtls_transport;
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if (new_dtls_transport) {
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new_dtls_transport->SignalDtlsState.connect(
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this, &DtlsSrtpTransport::OnDtlsState);
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}
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}
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void DtlsSrtpTransport::SetRtpDtlsTransport(
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cricket::DtlsTransportInternal* rtp_dtls_transport) {
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SetDtlsTransport(rtp_dtls_transport, &rtp_dtls_transport_);
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}
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void DtlsSrtpTransport::SetRtcpDtlsTransport(
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cricket::DtlsTransportInternal* rtcp_dtls_transport) {
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SetDtlsTransport(rtcp_dtls_transport, &rtcp_dtls_transport_);
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}
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void DtlsSrtpTransport::OnDtlsState(cricket::DtlsTransportInternal* transport,
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cricket::DtlsTransportState state) {
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RTC_DCHECK(transport == rtp_dtls_transport_ ||
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transport == rtcp_dtls_transport_);
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SignalDtlsStateChange();
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if (state != cricket::DTLS_TRANSPORT_CONNECTED) {
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ResetParams();
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return;
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}
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MaybeSetupDtlsSrtp();
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}
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void DtlsSrtpTransport::OnWritableState(
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rtc::PacketTransportInternal* packet_transport) {
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MaybeSetupDtlsSrtp();
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}
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} // namespace webrtc
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