| // Copyright 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "remoting/protocol/spake2_authenticator.h" |
| |
| #include <utility> |
| |
| #include "base/base64.h" |
| #include "base/logging.h" |
| #include "base/memory/ptr_util.h" |
| #include "base/sys_byteorder.h" |
| #include "crypto/hmac.h" |
| #include "crypto/secure_util.h" |
| #include "remoting/base/constants.h" |
| #include "remoting/base/rsa_key_pair.h" |
| #include "remoting/protocol/ssl_hmac_channel_authenticator.h" |
| #include "third_party/boringssl/src/include/openssl/curve25519.h" |
| #include "third_party/libjingle_xmpp/xmllite/xmlelement.h" |
| |
| namespace remoting { |
| namespace protocol { |
| |
| namespace { |
| |
| // Each peer sends 2 messages: <spake-message> and <verification-hash>. The |
| // content of <spake-message> is the output of SPAKE2_generate_msg() and must |
| // be passed to SPAKE2_process_msg() on the other end. This is enough to |
| // generate authentication key. <verification-hash> is sent to confirm that both |
| // ends get the same authentication key (which means they both know the |
| // password). This verification hash is calculated in |
| // CalculateVerificationHash() as follows: |
| // HMAC_SHA256(auth_key, ("host"|"client") + local_jid.length() + local_jid + |
| // remote_jid.length() + remote_jid) |
| // where auth_key is the key produced by SPAKE2. |
| |
| const jingle_xmpp::StaticQName kSpakeMessageTag = {kChromotingXmlNamespace, |
| "spake-message"}; |
| const jingle_xmpp::StaticQName kVerificationHashTag = {kChromotingXmlNamespace, |
| "verification-hash"}; |
| const jingle_xmpp::StaticQName kCertificateTag = {kChromotingXmlNamespace, |
| "certificate"}; |
| |
| std::unique_ptr<jingle_xmpp::XmlElement> EncodeBinaryValueToXml( |
| const jingle_xmpp::StaticQName& qname, |
| const std::string& content) { |
| std::string content_base64; |
| base::Base64Encode(content, &content_base64); |
| |
| std::unique_ptr<jingle_xmpp::XmlElement> result(new jingle_xmpp::XmlElement(qname)); |
| result->SetBodyText(content_base64); |
| return result; |
| } |
| |
| // Finds tag named |qname| in base_message and decodes it from base64 and stores |
| // in |data|. If the element is not present then found is set to false otherwise |
| // it's set to true. If the element is there and it's content cound't be decoded |
| // then false is returned. |
| bool DecodeBinaryValueFromXml(const jingle_xmpp::XmlElement* message, |
| const jingle_xmpp::QName& qname, |
| bool* found, |
| std::string* data) { |
| const jingle_xmpp::XmlElement* element = message->FirstNamed(qname); |
| *found = element != nullptr; |
| if (!*found) |
| return true; |
| |
| if (!base::Base64Decode(element->BodyText(), data)) { |
| LOG(WARNING) << "Failed to parse " << qname.LocalPart(); |
| return false; |
| } |
| |
| return !data->empty(); |
| } |
| |
| std::string PrefixWithLength(const std::string& str) { |
| uint32_t length = base::HostToNet32(str.size()); |
| return std::string(reinterpret_cast<char*>(&length), sizeof(length)) + str; |
| } |
| |
| } // namespace |
| |
| // static |
| std::unique_ptr<Authenticator> Spake2Authenticator::CreateForClient( |
| const std::string& local_id, |
| const std::string& remote_id, |
| const std::string& shared_secret, |
| Authenticator::State initial_state) { |
| return base::WrapUnique(new Spake2Authenticator( |
| local_id, remote_id, shared_secret, false, initial_state)); |
| } |
| |
| // static |
| std::unique_ptr<Authenticator> Spake2Authenticator::CreateForHost( |
| const std::string& local_id, |
| const std::string& remote_id, |
| const std::string& local_cert, |
| scoped_refptr<RsaKeyPair> key_pair, |
| const std::string& shared_secret, |
| Authenticator::State initial_state) { |
| std::unique_ptr<Spake2Authenticator> result(new Spake2Authenticator( |
| local_id, remote_id, shared_secret, true, initial_state)); |
| result->local_cert_ = local_cert; |
| result->local_key_pair_ = key_pair; |
| return std::move(result); |
| } |
| |
| Spake2Authenticator::Spake2Authenticator(const std::string& local_id, |
| const std::string& remote_id, |
| const std::string& shared_secret, |
| bool is_host, |
| Authenticator::State initial_state) |
| : local_id_(local_id), |
| remote_id_(remote_id), |
| shared_secret_(shared_secret), |
| is_host_(is_host), |
| state_(initial_state) { |
| spake2_context_ = SPAKE2_CTX_new( |
| is_host ? spake2_role_bob : spake2_role_alice, |
| reinterpret_cast<const uint8_t*>(local_id_.data()), local_id_.size(), |
| reinterpret_cast<const uint8_t*>(remote_id_.data()), remote_id_.size()); |
| |
| // Generate first message and push it to |pending_messages_|. |
| uint8_t message[SPAKE2_MAX_MSG_SIZE]; |
| size_t message_size; |
| int result = SPAKE2_generate_msg( |
| spake2_context_, message, &message_size, sizeof(message), |
| reinterpret_cast<const uint8_t*>(shared_secret_.data()), |
| shared_secret_.size()); |
| CHECK(result); |
| local_spake_message_.assign(reinterpret_cast<char*>(message), message_size); |
| } |
| |
| Spake2Authenticator::~Spake2Authenticator() { |
| SPAKE2_CTX_free(spake2_context_); |
| } |
| |
| Authenticator::State Spake2Authenticator::state() const { |
| if (state_ == ACCEPTED && !outgoing_verification_hash_.empty()) |
| return MESSAGE_READY; |
| return state_; |
| } |
| |
| bool Spake2Authenticator::started() const { |
| return started_; |
| } |
| |
| Authenticator::RejectionReason Spake2Authenticator::rejection_reason() const { |
| DCHECK_EQ(state(), REJECTED); |
| return rejection_reason_; |
| } |
| |
| void Spake2Authenticator::ProcessMessage(const jingle_xmpp::XmlElement* message, |
| const base::Closure& resume_callback) { |
| ProcessMessageInternal(message); |
| resume_callback.Run(); |
| } |
| |
| void Spake2Authenticator::ProcessMessageInternal( |
| const jingle_xmpp::XmlElement* message) { |
| DCHECK_EQ(state(), WAITING_MESSAGE); |
| |
| // Parse the certificate. |
| bool cert_present; |
| if (!DecodeBinaryValueFromXml(message, kCertificateTag, &cert_present, |
| &remote_cert_)) { |
| state_ = REJECTED; |
| rejection_reason_ = PROTOCOL_ERROR; |
| return; |
| } |
| |
| // Client always expects certificate in the first message. |
| if (!is_host_ && remote_cert_.empty()) { |
| LOG(WARNING) << "No valid host certificate."; |
| state_ = REJECTED; |
| rejection_reason_ = PROTOCOL_ERROR; |
| return; |
| } |
| |
| bool spake_message_present = false; |
| std::string spake_message; |
| bool verification_hash_present = false; |
| std::string verification_hash; |
| if (!DecodeBinaryValueFromXml(message, kSpakeMessageTag, |
| &spake_message_present, &spake_message) || |
| !DecodeBinaryValueFromXml(message, kVerificationHashTag, |
| &verification_hash_present, |
| &verification_hash)) { |
| state_ = REJECTED; |
| rejection_reason_ = PROTOCOL_ERROR; |
| return; |
| } |
| |
| // |auth_key_| is generated when <spake-message> is received. |
| if (auth_key_.empty()) { |
| if (!spake_message_present) { |
| LOG(WARNING) << "<spake-message> not found."; |
| state_ = REJECTED; |
| rejection_reason_ = PROTOCOL_ERROR; |
| return; |
| } |
| uint8_t key[SPAKE2_MAX_KEY_SIZE]; |
| size_t key_size; |
| started_ = true; |
| int result = SPAKE2_process_msg( |
| spake2_context_, key, &key_size, sizeof(key), |
| reinterpret_cast<const uint8_t*>(spake_message.data()), |
| spake_message.size()); |
| if (!result) { |
| state_ = REJECTED; |
| rejection_reason_ = INVALID_CREDENTIALS; |
| return; |
| } |
| CHECK(key_size); |
| auth_key_.assign(reinterpret_cast<char*>(key), key_size); |
| |
| outgoing_verification_hash_ = |
| CalculateVerificationHash(is_host_, local_id_, remote_id_); |
| expected_verification_hash_ = |
| CalculateVerificationHash(!is_host_, remote_id_, local_id_); |
| } else if (spake_message_present) { |
| LOG(WARNING) << "Received duplicate <spake-message>."; |
| state_ = REJECTED; |
| rejection_reason_ = PROTOCOL_ERROR; |
| return; |
| } |
| |
| if (spake_message_sent_ && !verification_hash_present) { |
| LOG(WARNING) << "Didn't receive <verification-hash> when expected."; |
| state_ = REJECTED; |
| rejection_reason_ = PROTOCOL_ERROR; |
| return; |
| } |
| |
| if (verification_hash_present) { |
| if (verification_hash.size() != expected_verification_hash_.size() || |
| !crypto::SecureMemEqual(verification_hash.data(), |
| expected_verification_hash_.data(), |
| verification_hash.size())) { |
| state_ = REJECTED; |
| rejection_reason_ = INVALID_CREDENTIALS; |
| return; |
| } |
| state_ = ACCEPTED; |
| return; |
| } |
| |
| state_ = MESSAGE_READY; |
| } |
| |
| std::unique_ptr<jingle_xmpp::XmlElement> Spake2Authenticator::GetNextMessage() { |
| DCHECK_EQ(state(), MESSAGE_READY); |
| |
| std::unique_ptr<jingle_xmpp::XmlElement> message = CreateEmptyAuthenticatorMessage(); |
| |
| if (!spake_message_sent_) { |
| if (!local_cert_.empty()) { |
| message->AddElement( |
| EncodeBinaryValueToXml(kCertificateTag, local_cert_).release()); |
| } |
| |
| message->AddElement( |
| EncodeBinaryValueToXml(kSpakeMessageTag, local_spake_message_) |
| .release()); |
| |
| spake_message_sent_ = true; |
| } |
| |
| if (!outgoing_verification_hash_.empty()) { |
| message->AddElement(EncodeBinaryValueToXml(kVerificationHashTag, |
| outgoing_verification_hash_) |
| .release()); |
| outgoing_verification_hash_.clear(); |
| } |
| |
| if (state_ != ACCEPTED) { |
| state_ = WAITING_MESSAGE; |
| } |
| return message; |
| } |
| |
| const std::string& Spake2Authenticator::GetAuthKey() const { |
| return auth_key_; |
| } |
| |
| std::unique_ptr<ChannelAuthenticator> |
| Spake2Authenticator::CreateChannelAuthenticator() const { |
| DCHECK_EQ(state(), ACCEPTED); |
| CHECK(!auth_key_.empty()); |
| |
| if (is_host_) { |
| return SslHmacChannelAuthenticator::CreateForHost( |
| local_cert_, local_key_pair_, auth_key_); |
| } else { |
| return SslHmacChannelAuthenticator::CreateForClient(remote_cert_, |
| auth_key_); |
| } |
| } |
| |
| std::string Spake2Authenticator::CalculateVerificationHash( |
| bool from_host, |
| const std::string& local_id, |
| const std::string& remote_id) { |
| std::string message = (from_host ? "host" : "client") + |
| PrefixWithLength(local_id) + |
| PrefixWithLength(remote_id); |
| crypto::HMAC hmac(crypto::HMAC::SHA256); |
| std::string result(hmac.DigestLength(), '\0'); |
| if (!hmac.Init(auth_key_) || |
| !hmac.Sign(message, reinterpret_cast<uint8_t*>(&result[0]), |
| result.length())) { |
| LOG(FATAL) << "Failed to calculate HMAC."; |
| } |
| return result; |
| } |
| |
| } // namespace protocol |
| } // namespace remoting |