blob: 2f8d06cbeafe59ddf240874b8822fb3440fb6ff1 [file] [log] [blame]
/*
* Copyright 2009 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 "pc/srtp_filter.h"
#include <string.h>
#include <cstdint>
#include <memory>
#include "absl/strings/match.h"
#include "rtc_base/logging.h"
#include "rtc_base/ssl_stream_adapter.h"
#include "rtc_base/third_party/base64/base64.h"
#include "rtc_base/zero_memory.h"
namespace cricket {
SrtpFilter::SrtpFilter() {}
SrtpFilter::~SrtpFilter() {}
bool SrtpFilter::IsActive() const {
return state_ >= ST_ACTIVE;
}
bool SrtpFilter::Process(const std::vector<CryptoParams>& cryptos,
webrtc::SdpType type,
ContentSource source) {
bool ret = false;
switch (type) {
case webrtc::SdpType::kOffer:
ret = SetOffer(cryptos, source);
break;
case webrtc::SdpType::kPrAnswer:
ret = SetProvisionalAnswer(cryptos, source);
break;
case webrtc::SdpType::kAnswer:
ret = SetAnswer(cryptos, source);
break;
default:
break;
}
if (!ret) {
return false;
}
return true;
}
bool SrtpFilter::SetOffer(const std::vector<CryptoParams>& offer_params,
ContentSource source) {
if (!ExpectOffer(source)) {
RTC_LOG(LS_ERROR) << "Wrong state to update SRTP offer";
return false;
}
return StoreParams(offer_params, source);
}
bool SrtpFilter::SetAnswer(const std::vector<CryptoParams>& answer_params,
ContentSource source) {
return DoSetAnswer(answer_params, source, true);
}
bool SrtpFilter::SetProvisionalAnswer(
const std::vector<CryptoParams>& answer_params,
ContentSource source) {
return DoSetAnswer(answer_params, source, false);
}
bool SrtpFilter::ExpectOffer(ContentSource source) {
return ((state_ == ST_INIT) || (state_ == ST_ACTIVE) ||
(state_ == ST_SENTOFFER && source == CS_LOCAL) ||
(state_ == ST_SENTUPDATEDOFFER && source == CS_LOCAL) ||
(state_ == ST_RECEIVEDOFFER && source == CS_REMOTE) ||
(state_ == ST_RECEIVEDUPDATEDOFFER && source == CS_REMOTE));
}
bool SrtpFilter::StoreParams(const std::vector<CryptoParams>& params,
ContentSource source) {
offer_params_ = params;
if (state_ == ST_INIT) {
state_ = (source == CS_LOCAL) ? ST_SENTOFFER : ST_RECEIVEDOFFER;
} else if (state_ == ST_ACTIVE) {
state_ =
(source == CS_LOCAL) ? ST_SENTUPDATEDOFFER : ST_RECEIVEDUPDATEDOFFER;
}
return true;
}
bool SrtpFilter::ExpectAnswer(ContentSource source) {
return ((state_ == ST_SENTOFFER && source == CS_REMOTE) ||
(state_ == ST_RECEIVEDOFFER && source == CS_LOCAL) ||
(state_ == ST_SENTUPDATEDOFFER && source == CS_REMOTE) ||
(state_ == ST_RECEIVEDUPDATEDOFFER && source == CS_LOCAL) ||
(state_ == ST_SENTPRANSWER_NO_CRYPTO && source == CS_LOCAL) ||
(state_ == ST_SENTPRANSWER && source == CS_LOCAL) ||
(state_ == ST_RECEIVEDPRANSWER_NO_CRYPTO && source == CS_REMOTE) ||
(state_ == ST_RECEIVEDPRANSWER && source == CS_REMOTE));
}
bool SrtpFilter::DoSetAnswer(const std::vector<CryptoParams>& answer_params,
ContentSource source,
bool final) {
if (!ExpectAnswer(source)) {
RTC_LOG(LS_ERROR) << "Invalid state for SRTP answer";
return false;
}
// If the answer doesn't requests crypto complete the negotiation of an
// unencrypted session.
// Otherwise, finalize the parameters and apply them.
if (answer_params.empty()) {
if (final) {
return ResetParams();
} else {
// Need to wait for the final answer to decide if
// we should go to Active state.
state_ = (source == CS_LOCAL) ? ST_SENTPRANSWER_NO_CRYPTO
: ST_RECEIVEDPRANSWER_NO_CRYPTO;
return true;
}
}
CryptoParams selected_params;
if (!NegotiateParams(answer_params, &selected_params))
return false;
const CryptoParams& new_send_params =
(source == CS_REMOTE) ? selected_params : answer_params[0];
const CryptoParams& new_recv_params =
(source == CS_REMOTE) ? answer_params[0] : selected_params;
if (!ApplySendParams(new_send_params) || !ApplyRecvParams(new_recv_params)) {
return false;
}
applied_send_params_ = new_send_params;
applied_recv_params_ = new_recv_params;
if (final) {
offer_params_.clear();
state_ = ST_ACTIVE;
} else {
state_ = (source == CS_LOCAL) ? ST_SENTPRANSWER : ST_RECEIVEDPRANSWER;
}
return true;
}
bool SrtpFilter::NegotiateParams(const std::vector<CryptoParams>& answer_params,
CryptoParams* selected_params) {
// We're processing an accept. We should have exactly one set of params,
// unless the offer didn't mention crypto, in which case we shouldn't be here.
bool ret = (answer_params.size() == 1U && !offer_params_.empty());
if (ret) {
// We should find a match between the answer params and the offered params.
std::vector<CryptoParams>::const_iterator it;
for (it = offer_params_.begin(); it != offer_params_.end(); ++it) {
if (answer_params[0].Matches(*it)) {
break;
}
}
if (it != offer_params_.end()) {
*selected_params = *it;
} else {
ret = false;
}
}
if (!ret) {
RTC_LOG(LS_WARNING) << "Invalid parameters in SRTP answer";
}
return ret;
}
bool SrtpFilter::ResetParams() {
offer_params_.clear();
applied_send_params_ = CryptoParams();
applied_recv_params_ = CryptoParams();
send_cipher_suite_ = absl::nullopt;
recv_cipher_suite_ = absl::nullopt;
send_key_.Clear();
recv_key_.Clear();
state_ = ST_INIT;
return true;
}
bool SrtpFilter::ApplySendParams(const CryptoParams& send_params) {
if (applied_send_params_.cipher_suite == send_params.cipher_suite &&
applied_send_params_.key_params == send_params.key_params) {
RTC_LOG(LS_INFO) << "Applying the same SRTP send parameters again. No-op.";
// We do not want to reset the ROC if the keys are the same. So just return.
return true;
}
send_cipher_suite_ = rtc::SrtpCryptoSuiteFromName(send_params.cipher_suite);
if (send_cipher_suite_ == rtc::SRTP_INVALID_CRYPTO_SUITE) {
RTC_LOG(LS_WARNING) << "Unknown crypto suite(s) received:"
" send cipher_suite "
<< send_params.cipher_suite;
return false;
}
int send_key_len, send_salt_len;
if (!rtc::GetSrtpKeyAndSaltLengths(*send_cipher_suite_, &send_key_len,
&send_salt_len)) {
RTC_LOG(LS_ERROR) << "Could not get lengths for crypto suite(s):"
" send cipher_suite "
<< send_params.cipher_suite;
return false;
}
send_key_ = rtc::ZeroOnFreeBuffer<uint8_t>(send_key_len + send_salt_len);
return ParseKeyParams(send_params.key_params, send_key_.data(),
send_key_.size());
}
bool SrtpFilter::ApplyRecvParams(const CryptoParams& recv_params) {
if (applied_recv_params_.cipher_suite == recv_params.cipher_suite &&
applied_recv_params_.key_params == recv_params.key_params) {
RTC_LOG(LS_INFO) << "Applying the same SRTP recv parameters again. No-op.";
// We do not want to reset the ROC if the keys are the same. So just return.
return true;
}
recv_cipher_suite_ = rtc::SrtpCryptoSuiteFromName(recv_params.cipher_suite);
if (recv_cipher_suite_ == rtc::SRTP_INVALID_CRYPTO_SUITE) {
RTC_LOG(LS_WARNING) << "Unknown crypto suite(s) received:"
" recv cipher_suite "
<< recv_params.cipher_suite;
return false;
}
int recv_key_len, recv_salt_len;
if (!rtc::GetSrtpKeyAndSaltLengths(*recv_cipher_suite_, &recv_key_len,
&recv_salt_len)) {
RTC_LOG(LS_ERROR) << "Could not get lengths for crypto suite(s):"
" recv cipher_suite "
<< recv_params.cipher_suite;
return false;
}
recv_key_ = rtc::ZeroOnFreeBuffer<uint8_t>(recv_key_len + recv_salt_len);
return ParseKeyParams(recv_params.key_params, recv_key_.data(),
recv_key_.size());
}
bool SrtpFilter::ParseKeyParams(const std::string& key_params,
uint8_t* key,
size_t len) {
// example key_params: "inline:YUJDZGVmZ2hpSktMbW9QUXJzVHVWd3l6MTIzNDU2"
// Fail if key-method is wrong.
if (!absl::StartsWith(key_params, "inline:")) {
return false;
}
// Fail if base64 decode fails, or the key is the wrong size.
std::string key_b64(key_params.substr(7)), key_str;
if (!rtc::Base64::Decode(key_b64, rtc::Base64::DO_STRICT, &key_str,
nullptr) ||
key_str.size() != len) {
return false;
}
memcpy(key, key_str.c_str(), len);
// TODO(bugs.webrtc.org/8905): Switch to ZeroOnFreeBuffer for storing
// sensitive data.
rtc::ExplicitZeroMemory(&key_str[0], key_str.size());
return true;
}
} // namespace cricket