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/*
* libjingle
* Copyright 2009, Google Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#undef HAVE_CONFIG_H
#include "talk/session/phone/srtpfilter.h"
#include <algorithm>
#include <cstring>
#include "talk/base/base64.h"
#include "talk/base/logging.h"
#include "talk/base/timeutils.h"
#include "talk/session/phone/rtputils.h"
// Enable this line to turn on SRTP debugging
// #define SRTP_DEBUG
#ifdef HAVE_SRTP
#ifdef SRTP_RELATIVE_PATH
#include "srtp.h" // NOLINT
#else
#include "third_party/libsrtp/include/srtp.h"
#endif // SRTP_RELATIVE_PATH
#ifdef _DEBUG
extern "C" debug_module_t mod_srtp;
extern "C" debug_module_t mod_auth;
extern "C" debug_module_t mod_cipher;
extern "C" debug_module_t mod_stat;
extern "C" debug_module_t mod_alloc;
extern "C" debug_module_t mod_aes_icm;
extern "C" debug_module_t mod_aes_hmac;
#endif
#else
// SrtpFilter needs that constant.
#define SRTP_MASTER_KEY_LEN 30
#endif // HAVE_SRTP
namespace cricket {
const char CS_AES_CM_128_HMAC_SHA1_80[] = "AES_CM_128_HMAC_SHA1_80";
const char CS_AES_CM_128_HMAC_SHA1_32[] = "AES_CM_128_HMAC_SHA1_32";
const int SRTP_MASTER_KEY_BASE64_LEN = SRTP_MASTER_KEY_LEN * 4 / 3;
#ifndef HAVE_SRTP
// This helper function is used on systems that don't (yet) have SRTP,
// to log that the functions that require it won't do anything.
namespace {
bool SrtpNotAvailable(const char *func) {
LOG(LS_ERROR) << func << ": SRTP is not available on your system.";
return false;
}
} // anonymous namespace
#endif // !HAVE_SRTP
void EnableSrtpDebugging() {
#ifdef HAVE_SRTP
#ifdef _DEBUG
debug_on(mod_srtp);
debug_on(mod_auth);
debug_on(mod_cipher);
debug_on(mod_stat);
debug_on(mod_alloc);
debug_on(mod_aes_icm);
// debug_on(mod_aes_cbc);
// debug_on(mod_hmac);
#endif
#endif // HAVE_SRTP
}
SrtpFilter::SrtpFilter()
: state_(ST_INIT),
send_session_(new SrtpSession()),
recv_session_(new SrtpSession()) {
SignalSrtpError.repeat(send_session_->SignalSrtpError);
SignalSrtpError.repeat(recv_session_->SignalSrtpError);
}
SrtpFilter::~SrtpFilter() {
}
bool SrtpFilter::IsActive() const {
return (state_ == ST_ACTIVE);
}
bool SrtpFilter::SetOffer(const std::vector<CryptoParams>& offer_params,
ContentSource source) {
bool ret = false;
if (state_ == ST_INIT) {
ret = StoreParams(offer_params, source);
} else {
LOG(LS_ERROR) << "Invalid state for SRTP offer";
}
return ret;
}
bool SrtpFilter::SetAnswer(const std::vector<CryptoParams>& answer_params,
ContentSource source) {
bool ret = false;
if ((state_ == ST_SENTOFFER && source == CS_REMOTE) ||
(state_ == ST_RECEIVEDOFFER && source == CS_LOCAL)) {
// If the answer requests crypto, finalize the parameters and apply them.
// Otherwise, complete the negotiation of a unencrypted session.
if (!answer_params.empty()) {
CryptoParams selected_params;
ret = NegotiateParams(answer_params, &selected_params);
if (ret) {
if (state_ == ST_SENTOFFER) {
ret = ApplyParams(selected_params, answer_params[0]);
} else { // ST_RECEIVEDOFFER
ret = ApplyParams(answer_params[0], selected_params);
}
}
} else {
ret = ResetParams();
}
} else {
LOG(LS_ERROR) << "Invalid state for SRTP answer";
}
return ret;
}
bool SrtpFilter::ProtectRtp(void* p, int in_len, int max_len, int* out_len) {
if (!IsActive()) {
LOG(LS_WARNING) << "Failed to ProtectRtp: SRTP not active";
return false;
}
return send_session_->ProtectRtp(p, in_len, max_len, out_len);
}
bool SrtpFilter::ProtectRtcp(void* p, int in_len, int max_len, int* out_len) {
if (!IsActive()) {
LOG(LS_WARNING) << "Failed to ProtectRtcp: SRTP not active";
return false;
}
return send_session_->ProtectRtcp(p, in_len, max_len, out_len);
}
bool SrtpFilter::UnprotectRtp(void* p, int in_len, int* out_len) {
if (!IsActive()) {
LOG(LS_WARNING) << "Failed to UnprotectRtp: SRTP not active";
return false;
}
return recv_session_->UnprotectRtp(p, in_len, out_len);
}
bool SrtpFilter::UnprotectRtcp(void* p, int in_len, int* out_len) {
if (!IsActive()) {
LOG(LS_WARNING) << "Failed to UnprotectRtcp: SRTP not active";
return false;
}
return recv_session_->UnprotectRtcp(p, in_len, out_len);
}
void SrtpFilter::set_signal_silent_time(uint32 signal_silent_time_in_ms) {
send_session_->set_signal_silent_time(signal_silent_time_in_ms);
recv_session_->set_signal_silent_time(signal_silent_time_in_ms);
}
bool SrtpFilter::StoreParams(const std::vector<CryptoParams>& params,
ContentSource source) {
offer_params_ = params;
state_ = (source == CS_LOCAL) ? ST_SENTOFFER : ST_RECEIVEDOFFER;
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) {
LOG(LS_WARNING) << "Invalid parameters in SRTP answer";
}
return ret;
}
bool SrtpFilter::ApplyParams(const CryptoParams& send_params,
const CryptoParams& recv_params) {
// TODO: Zero these buffers after use.
bool ret;
uint8 send_key[SRTP_MASTER_KEY_LEN], recv_key[SRTP_MASTER_KEY_LEN];
ret = (ParseKeyParams(send_params.key_params, send_key, sizeof(send_key)) &&
ParseKeyParams(recv_params.key_params, recv_key, sizeof(recv_key)));
if (ret) {
ret = (send_session_->SetSend(send_params.cipher_suite,
send_key, sizeof(send_key)) &&
recv_session_->SetRecv(recv_params.cipher_suite,
recv_key, sizeof(recv_key)));
}
if (ret) {
offer_params_.clear();
state_ = ST_ACTIVE;
LOG(LS_INFO) << "SRTP activated with negotiated parameters:"
<< " send cipher_suite " << send_params.cipher_suite
<< " recv cipher_suite " << recv_params.cipher_suite;
} else {
LOG(LS_WARNING) << "Failed to apply negotiated SRTP parameters";
}
return ret;
}
bool SrtpFilter::ResetParams() {
offer_params_.clear();
state_ = ST_INIT;
LOG(LS_INFO) << "SRTP reset to init state";
return true;
}
bool SrtpFilter::ParseKeyParams(const std::string& key_params,
uint8* key, int len) {
// example key_params: "inline:YUJDZGVmZ2hpSktMbW9QUXJzVHVWd3l6MTIzNDU2"
// Fail if key-method is wrong.
if (key_params.find("inline:") != 0) {
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 (!talk_base::Base64::Decode(key_b64, talk_base::Base64::DO_STRICT,
&key_str, NULL) ||
static_cast<int>(key_str.size()) != len) {
return false;
}
memcpy(key, key_str.c_str(), len);
return true;
}
///////////////////////////////////////////////////////////////////////////////
// SrtpSession
#ifdef HAVE_SRTP
bool SrtpSession::inited_ = false;
std::list<SrtpSession*> SrtpSession::sessions_;
SrtpSession::SrtpSession()
: session_(NULL),
rtp_auth_tag_len_(0),
rtcp_auth_tag_len_(0),
srtp_stat_(new SrtpStat()),
last_send_seq_num_(-1) {
sessions_.push_back(this);
SignalSrtpError.repeat(srtp_stat_->SignalSrtpError);
}
SrtpSession::~SrtpSession() {
sessions_.erase(std::find(sessions_.begin(), sessions_.end(), this));
if (session_) {
srtp_dealloc(session_);
}
}
bool SrtpSession::SetSend(const std::string& cs, const uint8* key, int len) {
return SetKey(ssrc_any_outbound, cs, key, len);
}
bool SrtpSession::SetRecv(const std::string& cs, const uint8* key, int len) {
return SetKey(ssrc_any_inbound, cs, key, len);
}
bool SrtpSession::ProtectRtp(void* p, int in_len, int max_len, int* out_len) {
if (!session_) {
LOG(LS_WARNING) << "Failed to protect SRTP packet: no SRTP Session";
return false;
}
int need_len = in_len + rtp_auth_tag_len_; // NOLINT
if (max_len < need_len) {
LOG(LS_WARNING) << "Failed to protect SRTP packet: The buffer length "
<< max_len << " is less than the needed " << need_len;
return false;
}
*out_len = in_len;
int err = srtp_protect(session_, p, out_len);
uint32 ssrc;
if (GetRtpSsrc(p, in_len, &ssrc)) {
srtp_stat_->AddProtectRtpResult(ssrc, err);
}
int seq_num;
GetRtpSeqNum(p, in_len, &seq_num);
if (err != err_status_ok) {
LOG(LS_WARNING) << "Failed to protect SRTP packet, seqnum="
<< seq_num << ", err=" << err << ", last seqnum="
<< last_send_seq_num_;
return false;
}
last_send_seq_num_ = seq_num;
return true;
}
bool SrtpSession::ProtectRtcp(void* p, int in_len, int max_len, int* out_len) {
if (!session_) {
LOG(LS_WARNING) << "Failed to protect SRTCP packet: no SRTP Session";
return false;
}
int need_len = in_len + sizeof(uint32) + rtcp_auth_tag_len_; // NOLINT
if (max_len < need_len) {
LOG(LS_WARNING) << "Failed to protect SRTCP packet: The buffer length "
<< max_len << " is less than the needed " << need_len;
return false;
}
*out_len = in_len;
int err = srtp_protect_rtcp(session_, p, out_len);
srtp_stat_->AddProtectRtcpResult(err);
if (err != err_status_ok) {
LOG(LS_WARNING) << "Failed to protect SRTCP packet, err=" << err;
return false;
}
return true;
}
bool SrtpSession::UnprotectRtp(void* p, int in_len, int* out_len) {
if (!session_) {
LOG(LS_WARNING) << "Failed to unprotect SRTP packet: no SRTP Session";
return false;
}
*out_len = in_len;
int err = srtp_unprotect(session_, p, out_len);
uint32 ssrc;
if (GetRtpSsrc(p, in_len, &ssrc)) {
srtp_stat_->AddUnprotectRtpResult(ssrc, err);
}
if (err != err_status_ok) {
LOG(LS_WARNING) << "Failed to unprotect SRTP packet, err=" << err;
return false;
}
return true;
}
bool SrtpSession::UnprotectRtcp(void* p, int in_len, int* out_len) {
if (!session_) {
LOG(LS_WARNING) << "Failed to unprotect SRTCP packet: no SRTP Session";
return false;
}
*out_len = in_len;
int err = srtp_unprotect_rtcp(session_, p, out_len);
srtp_stat_->AddUnprotectRtcpResult(err);
if (err != err_status_ok) {
LOG(LS_WARNING) << "Failed to unprotect SRTCP packet, err=" << err;
return false;
}
return true;
}
void SrtpSession::set_signal_silent_time(uint32 signal_silent_time_in_ms) {
srtp_stat_->set_signal_silent_time(signal_silent_time_in_ms);
}
bool SrtpSession::SetKey(int type, const std::string& cs,
const uint8* key, int len) {
if (session_) {
LOG(LS_ERROR) << "Failed to create SRTP session: "
<< "SRTP session already created";
return false;
}
if (!Init()) {
return false;
}
srtp_policy_t policy;
memset(&policy, 0, sizeof(policy));
if (cs == CS_AES_CM_128_HMAC_SHA1_80) {
crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtp);
crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp);
} else if (cs == CS_AES_CM_128_HMAC_SHA1_32) {
crypto_policy_set_aes_cm_128_hmac_sha1_32(&policy.rtp); // rtp is 32,
crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp); // rtcp still 80
} else {
LOG(LS_WARNING) << "Failed to create SRTP session: unsupported"
<< " cipher_suite " << cs.c_str();
return false;
}
if (!key || len != SRTP_MASTER_KEY_LEN) {
LOG(LS_WARNING) << "Failed to create SRTP session: invalid key";
return false;
}
policy.ssrc.type = static_cast<ssrc_type_t>(type);
policy.ssrc.value = 0;
policy.key = const_cast<uint8*>(key);
// TODO parse window size from WSH session-param
policy.window_size = 1024;
policy.allow_repeat_tx = 1;
policy.next = NULL;
int err = srtp_create(&session_, &policy);
if (err != err_status_ok) {
LOG(LS_ERROR) << "Failed to create SRTP session, err=" << err;
return false;
}
rtp_auth_tag_len_ = policy.rtp.auth_tag_len;
rtcp_auth_tag_len_ = policy.rtcp.auth_tag_len;
return true;
}
bool SrtpSession::Init() {
if (!inited_) {
int err;
err = srtp_init();
if (err != err_status_ok) {
LOG(LS_ERROR) << "Failed to init SRTP, err=" << err;
return false;
}
err = srtp_install_event_handler(&SrtpSession::HandleEventThunk);
if (err != err_status_ok) {
LOG(LS_ERROR) << "Failed to install SRTP event handler, err=" << err;
return false;
}
inited_ = true;
}
return true;
}
void SrtpSession::HandleEvent(const srtp_event_data_t* ev) {
switch (ev->event) {
case event_ssrc_collision:
LOG(LS_INFO) << "SRTP event: SSRC collision";
break;
case event_key_soft_limit:
LOG(LS_INFO) << "SRTP event: reached soft key usage limit";
break;
case event_key_hard_limit:
LOG(LS_INFO) << "SRTP event: reached hard key usage limit";
break;
case event_packet_index_limit:
LOG(LS_INFO) << "SRTP event: reached hard packet limit (2^48 packets)";
break;
default:
LOG(LS_INFO) << "SRTP event: unknown " << ev->event;
break;
}
}
void SrtpSession::HandleEventThunk(srtp_event_data_t* ev) {
for (std::list<SrtpSession*>::iterator it = sessions_.begin();
it != sessions_.end(); ++it) {
if ((*it)->session_ == ev->session) {
(*it)->HandleEvent(ev);
break;
}
}
}
#else // !HAVE_SRTP
// On some systems, SRTP is not (yet) available.
SrtpSession::SrtpSession() {
LOG(WARNING) << "SRTP implementation is missing.";
}
SrtpSession::~SrtpSession() {
}
bool SrtpSession::SetSend(const std::string& cs, const uint8* key, int len) {
return SrtpNotAvailable(__FUNCTION__);
}
bool SrtpSession::SetRecv(const std::string& cs, const uint8* key, int len) {
return SrtpNotAvailable(__FUNCTION__);
}
bool SrtpSession::ProtectRtp(void* data, int in_len, int max_len,
int* out_len) {
return SrtpNotAvailable(__FUNCTION__);
}
bool SrtpSession::ProtectRtcp(void* data, int in_len, int max_len,
int* out_len) {
return SrtpNotAvailable(__FUNCTION__);
}
bool SrtpSession::UnprotectRtp(void* data, int in_len, int* out_len) {
return SrtpNotAvailable(__FUNCTION__);
}
bool SrtpSession::UnprotectRtcp(void* data, int in_len, int* out_len) {
return SrtpNotAvailable(__FUNCTION__);
}
void SrtpSession::set_signal_silent_time(uint32 signal_silent_time) {
// Do nothing.
}
#endif // HAVE_SRTP
///////////////////////////////////////////////////////////////////////////////
// SrtpStat
#ifdef HAVE_SRTP
SrtpStat::SrtpStat()
: signal_silent_time_(1000) {
}
void SrtpStat::AddProtectRtpResult(uint32 ssrc, int result) {
FailureKey key;
key.ssrc = ssrc;
key.mode = SrtpFilter::PROTECT;
switch (result) {
case err_status_ok:
key.error = SrtpFilter::ERROR_NONE;
break;
case err_status_auth_fail:
key.error = SrtpFilter::ERROR_AUTH;
break;
default:
key.error = SrtpFilter::ERROR_FAIL;
}
HandleSrtpResult(key);
}
void SrtpStat::AddUnprotectRtpResult(uint32 ssrc, int result) {
FailureKey key;
key.ssrc = ssrc;
key.mode = SrtpFilter::UNPROTECT;
switch (result) {
case err_status_ok:
key.error = SrtpFilter::ERROR_NONE;
break;
case err_status_auth_fail:
key.error = SrtpFilter::ERROR_AUTH;
break;
case err_status_replay_fail:
case err_status_replay_old:
key.error = SrtpFilter::ERROR_REPLAY;
break;
default:
key.error = SrtpFilter::ERROR_FAIL;
}
HandleSrtpResult(key);
}
void SrtpStat::AddProtectRtcpResult(int result) {
AddProtectRtpResult(0U, result);
}
void SrtpStat::AddUnprotectRtcpResult(int result) {
AddUnprotectRtpResult(0U, result);
}
void SrtpStat::HandleSrtpResult(const SrtpStat::FailureKey& key) {
// Handle some cases where error should be signalled right away. For other
// errors, trigger error for the first time seeing it. After that, silent
// the same error for a certain amount of time (default 1 sec).
if (key.error != SrtpFilter::ERROR_NONE) {
// For errors, signal first time and wait for 1 sec.
FailureStat* stat = &(failures_[key]);
uint32 current_time = talk_base::Time();
if (stat->last_signal_time == 0 ||
talk_base::TimeDiff(current_time, stat->last_signal_time) >
static_cast<int>(signal_silent_time_)) {
SignalSrtpError(key.ssrc, key.mode, key.error);
stat->last_signal_time = current_time;
}
}
}
#else // !HAVE_SRTP
// On some systems, SRTP is not (yet) available.
SrtpStat::SrtpStat()
: signal_silent_time_(1000) {
LOG(WARNING) << "SRTP implementation is missing.";
}
void SrtpStat::AddProtectRtpResult(uint32 ssrc, int result) {
SrtpNotAvailable(__FUNCTION__);
}
void SrtpStat::AddUnprotectRtpResult(uint32 ssrc, int result) {
SrtpNotAvailable(__FUNCTION__);
}
void SrtpStat::AddProtectRtcpResult(int result) {
SrtpNotAvailable(__FUNCTION__);
}
void SrtpStat::AddUnprotectRtcpResult(int result) {
SrtpNotAvailable(__FUNCTION__);
}
void SrtpStat::HandleSrtpResult(const SrtpStat::FailureKey& key) {
SrtpNotAvailable(__FUNCTION__);
}
#endif // HAVE_SRTP
} // namespace cricket