/**
* If we don't know her key, the handshake has to be done backwards.
* Reverse handshake requests are signaled by sending a non-obfuscated zero nonce.
*/
static uint8_t genReverseHandshake(struct Message* message,
struct CryptoAuth_Wrapper* wrapper,
union Headers_CryptoAuth* header)
{
reset(wrapper);
Message_shift(message, -Headers_CryptoAuth_SIZE, NULL);
// Buffer the packet so it can be sent ASAP
if (wrapper->bufferedMessage != NULL) {
// Not exactly a drop but a message is not going to reach the destination.
cryptoAuthDebug0(wrapper,
"DROP Expelled a message because a session has not yet been setup");
Allocator_free(wrapper->bufferedMessage->alloc);
}
cryptoAuthDebug0(wrapper, "Buffered a message");
struct Allocator* bmalloc = Allocator_child(wrapper->externalInterface.allocator);
wrapper->bufferedMessage = Message_clone(message, bmalloc);
Assert_ifParanoid(wrapper->nextNonce == 0);
Message_shift(message, Headers_CryptoAuth_SIZE, NULL);
header = (union Headers_CryptoAuth*) message->bytes;
header->nonce = UINT32_MAX;
message->length = Headers_CryptoAuth_SIZE;
// sessionState must be 0, auth and 24 byte nonce are garbaged and public key is set
// now garbage the authenticator and the encrypted key which are not used.
Random_bytes(wrapper->context->rand, (uint8_t*) &header->handshake.authenticator, 48);
// This is a special packet which the user should never see.
Headers_setSetupPacket(&header->handshake.auth, 1);
return wrapper->wrappedInterface->sendMessage(message, wrapper->wrappedInterface);
}
/**
* If we don't know her key, the handshake has to be done backwards.
* Reverse handshake requests are signaled by sending a non-obfuscated zero nonce.
*/
static uint8_t genReverseHandshake(struct Message* message,
struct CryptoAuth_Wrapper* wrapper,
union Headers_CryptoAuth* header)
{
wrapper->nextNonce = 0;
Message_shift(message, -Headers_CryptoAuth_SIZE);
// Buffer the packet so it can be sent ASAP
if (wrapper->bufferedMessage == NULL) {
cryptoAuthDebug0(wrapper, "Buffered a message");
wrapper->bufferedMessage =
Message_clone(message, wrapper->externalInterface.allocator);
Assert_true(wrapper->nextNonce == 0);
} else {
cryptoAuthDebug0(wrapper, "Expelled a message because a session has not yet been setup");
Message_copyOver(wrapper->bufferedMessage,
message,
wrapper->externalInterface.allocator);
Assert_true(wrapper->nextNonce == 0);
}
wrapper->hasBufferedMessage = true;
Message_shift(message, Headers_CryptoAuth_SIZE);
header = (union Headers_CryptoAuth*) message->bytes;
header->nonce = UINT32_MAX;
message->length = Headers_CryptoAuth_SIZE;
// sessionState must be 0, auth and 24 byte nonce are garbaged and public key is set
// now garbage the authenticator and the encrypted key which are not used.
Random_bytes(wrapper->context->rand, (uint8_t*) &header->handshake.authenticator, 48);
return wrapper->wrappedInterface->sendMessage(message, wrapper->wrappedInterface);
}
static uint8_t receiveMessage(struct Message* received, struct Interface* interface)
{
struct CryptoAuth_Wrapper* wrapper =
Identity_cast((struct CryptoAuth_Wrapper*) interface->receiverContext);
union Headers_CryptoAuth* header = (union Headers_CryptoAuth*) received->bytes;
if (received->length < (wrapper->authenticatePackets ? 20 : 4)) {
cryptoAuthDebug0(wrapper, "Dropped runt");
return Error_UNDERSIZE_MESSAGE;
}
Assert_true(received->padding >= 12 || "need at least 12 bytes of padding in incoming message");
#ifdef Log_DEBUG
Assert_true(!((uintptr_t)received->bytes % 4) || !"alignment fault");
#endif
Message_shift(received, -4);
uint32_t nonce = Endian_bigEndianToHost32(header->nonce);
if (wrapper->nextNonce < 5) {
if (nonce > 3 && nonce != UINT32_MAX && knowHerKey(wrapper)) {
cryptoAuthDebug(wrapper, "Trying final handshake step, nonce=%u\n", nonce);
uint8_t secret[32];
getSharedSecret(secret,
wrapper->secret,
wrapper->tempKey,
NULL,
wrapper->context->logger);
// We'll optimistically advance the nextNonce value because decryptMessage()
// passes the message on to the upper level and if this message causes a
// response, we want the CA to be in ESTABLISHED state.
// if the decryptMessage() call fails, we CryptoAuth_reset() it back.
wrapper->nextNonce += 3;
if (decryptMessage(wrapper, nonce, received, secret)) {
cryptoAuthDebug0(wrapper, "Final handshake step succeeded");
Bits_memcpyConst(wrapper->secret, secret, 32);
return callReceivedMessage(wrapper, received);
}
CryptoAuth_reset(&wrapper->externalInterface);
cryptoAuthDebug0(wrapper, "Final handshake step failed");
return Error_UNDELIVERABLE;
}
} else if (nonce > 4) {
if (decryptMessage(wrapper, nonce, received, wrapper->secret)) {
return callReceivedMessage(wrapper, received);
} else {
cryptoAuthDebug0(wrapper, "Failed to decrypt message");
return Error_UNDELIVERABLE;
}
} else {
cryptoAuthDebug0(wrapper, "Received handshake message during established connection");
}
Message_shift(received, 4);
return decryptHandshake(wrapper, nonce, received, header);
}
/** @return 0 on success, -1 otherwise. */
int CryptoAuth_encrypt(struct CryptoAuth_Session* sessionPub, struct Message* msg)
{
struct CryptoAuth_Session_pvt* session =
Identity_check((struct CryptoAuth_Session_pvt*) sessionPub);
// If there has been no incoming traffic for a while, reset the connection to state 0.
// This will prevent "connection in bad state" situations from lasting forever.
// this will reset the session if it has timed out.
resetIfTimeout(session);
// If the nonce wraps, start over.
if (session->nextNonce >= 0xfffffff0) {
reset(session);
}
Assert_true(!((uintptr_t)msg->bytes % 4) || !"alignment fault");
// nextNonce 0: sending hello, we are initiating connection.
// nextNonce 1: sending another hello, nothing received yet.
// nextNonce 2: sending key, hello received.
// nextNonce 3: sending key again, no data packet recieved yet.
// nextNonce >3: handshake complete
//
// if it's a blind handshake, every message will be empty and nextNonce will remain
// zero until the first message is received back.
if (session->nextNonce < 5) {
if (session->nextNonce < 4) {
encryptHandshake(msg, session, 0);
return 0;
} else {
cryptoAuthDebug0(session, "Doing final step to send message. nonce=4");
Assert_ifParanoid(!Bits_isZero(session->ourTempPrivKey, 32));
Assert_ifParanoid(!Bits_isZero(session->herTempPubKey, 32));
getSharedSecret(session->sharedSecret,
session->ourTempPrivKey,
session->herTempPubKey,
NULL,
session->context->logger);
}
}
Assert_true(msg->length > 0 && "Empty packet during handshake");
Assert_true(msg->padding >= 36 || !"not enough padding");
encrypt(session->nextNonce, msg, session->sharedSecret, session->isInitiator);
Message_push32(msg, session->nextNonce, NULL);
session->nextNonce++;
return 0;
}
static inline bool decryptMessage(struct CryptoAuth_Wrapper* wrapper,
uint32_t nonce,
struct Message* content,
uint8_t secret[32])
{
// Decrypt with authentication and replay prevention.
if (decrypt(nonce, content, secret, wrapper->isInitiator)) {
cryptoAuthDebug0(wrapper, "DROP authenticated decryption failed");
return false;
}
if (!ReplayProtector_checkNonce(nonce, &wrapper->replayProtector)) {
cryptoAuthDebug(wrapper, "DROP nonce checking failed nonce=[%u]", nonce);
return false;
}
return true;
}
static inline Gcc_USE_RET bool decryptMessage(struct CryptoAuth_Session_pvt* session,
uint32_t nonce,
struct Message* content,
uint8_t secret[32])
{
// Decrypt with authentication and replay prevention.
if (decrypt(nonce, content, secret, session->isInitiator)) {
cryptoAuthDebug0(session, "DROP authenticated decryption failed");
return false;
}
if (!ReplayProtector_checkNonce(nonce, &session->pub.replayProtector)) {
cryptoAuthDebug(session, "DROP nonce checking failed nonce=[%u]", nonce);
return false;
}
return true;
}
static uint8_t sendMessage(struct Message* message, struct Interface* interface)
{
struct CryptoAuth_Wrapper* wrapper =
Identity_cast((struct CryptoAuth_Wrapper*) interface->senderContext);
// If there has been no incoming traffic for a while, reset the connection to state 0.
// This will prevent "connection in bad state" situations from lasting forever.
// this will reset the session if it has timed out.
CryptoAuth_getState(interface);
// If the nonce wraps, start over.
if (wrapper->nextNonce >= 0xfffffff0) {
reset(wrapper);
}
#ifdef Log_DEBUG
Assert_true(!((uintptr_t)message->bytes % 4) || !"alignment fault");
#endif
// nextNonce 0: sending hello, we are initiating connection.
// nextNonce 1: sending another hello, nothing received yet.
// nextNonce 2: sending key, hello received.
// nextNonce 3: sending key again, no data packet recieved yet.
// nextNonce >3: handshake complete
//
// if it's a blind handshake, every message will be empty and nextNonce will remain
// zero until the first message is received back.
if (wrapper->nextNonce < 5) {
if (wrapper->nextNonce < 4) {
return encryptHandshake(message, wrapper, 0);
} else {
cryptoAuthDebug0(wrapper, "Doing final step to send message. nonce=4");
Assert_true(!Bits_isZero(wrapper->ourTempPrivKey, 32));
Assert_true(!Bits_isZero(wrapper->herTempPubKey, 32));
getSharedSecret(wrapper->sharedSecret,
wrapper->ourTempPrivKey,
wrapper->herTempPubKey,
NULL,
wrapper->context->logger);
}
}
Assert_true(message->length > 0 && "Empty packet during handshake");
return encryptMessage(message, wrapper);
}
static inline bool decryptMessage(struct CryptoAuth_Wrapper* wrapper,
uint32_t nonce,
struct Message* content,
uint8_t secret[32])
{
if (wrapper->authenticatePackets) {
// Decrypt with authentication and replay prevention.
int ret = decrypt(nonce, content, secret, wrapper->isInitiator, true);
if (ret) {
cryptoAuthDebug(wrapper, "Authenticated decryption failed returning %u", ret);
return false;
}
ret = !ReplayProtector_checkNonce(nonce, &wrapper->replayProtector);
if (ret) {
cryptoAuthDebug0(wrapper, "Nonce checking failed");
return false;
}
} else {
decrypt(nonce, content, secret, wrapper->isInitiator, false);
}
return true;
}
static uint8_t receiveMessage(struct Message* received, struct Interface* interface)
{
struct CryptoAuth_Wrapper* wrapper =
Identity_check((struct CryptoAuth_Wrapper*) interface->receiverContext);
union Headers_CryptoAuth* header = (union Headers_CryptoAuth*) received->bytes;
if (received->length < 20) {
cryptoAuthDebug0(wrapper, "DROP runt");
return Error_UNDERSIZE_MESSAGE;
}
Assert_true(received->padding >= 12 || "need at least 12 bytes of padding in incoming message");
Assert_true(!((uintptr_t)received->bytes % 4) || !"alignment fault");
Message_shift(received, -4, NULL);
uint32_t nonce = Endian_bigEndianToHost32(header->nonce);
if (!wrapper->established) {
if (nonce > 3 && nonce != UINT32_MAX) {
if (wrapper->nextNonce < 3) {
// This is impossible because we have not exchanged hello and key messages.
cryptoAuthDebug0(wrapper, "DROP Received a run message to an un-setup session");
return Error_UNDELIVERABLE;
}
cryptoAuthDebug(wrapper, "Trying final handshake step, nonce=%u\n", nonce);
uint8_t secret[32];
Assert_ifParanoid(!Bits_isZero(wrapper->ourTempPrivKey, 32));
Assert_ifParanoid(!Bits_isZero(wrapper->herTempPubKey, 32));
getSharedSecret(secret,
wrapper->ourTempPrivKey,
wrapper->herTempPubKey,
NULL,
wrapper->context->logger);
// We'll optimistically advance the nextNonce value because decryptMessage()
// passes the message on to the upper level and if this message causes a
// response, we want the CA to be in ESTABLISHED state.
// if the decryptMessage() call fails, we CryptoAuth_reset() it back.
wrapper->nextNonce += 3;
if (decryptMessage(wrapper, nonce, received, secret)) {
cryptoAuthDebug0(wrapper, "Final handshake step succeeded");
Bits_memcpyConst(wrapper->sharedSecret, secret, 32);
// Now we're in run mode, no more handshake packets will be accepted
Bits_memset(wrapper->ourTempPrivKey, 0, 32);
Bits_memset(wrapper->ourTempPubKey, 0, 32);
Bits_memset(wrapper->herTempPubKey, 0, 32);
wrapper->established = true;
return callReceivedMessage(wrapper, received);
}
CryptoAuth_reset(&wrapper->externalInterface);
cryptoAuthDebug0(wrapper, "DROP Final handshake step failed");
return Error_UNDELIVERABLE;
}
Message_shift(received, 4, NULL);
return decryptHandshake(wrapper, nonce, received, header);
} else if (nonce > 3 && nonce != UINT32_MAX) {
Assert_ifParanoid(!Bits_isZero(wrapper->sharedSecret, 32));
if (decryptMessage(wrapper, nonce, received, wrapper->sharedSecret)) {
return callReceivedMessage(wrapper, received);
} else {
cryptoAuthDebug0(wrapper, "DROP Failed to decrypt message");
return Error_UNDELIVERABLE;
}
} else if (nonce < 2) {
cryptoAuthDebug(wrapper, "hello packet during established session nonce=[%d]", nonce);
Message_shift(received, 4, NULL);
return decryptHandshake(wrapper, nonce, received, header);
} else {
// setup keys are already zeroed, not much we can do here.
cryptoAuthDebug(wrapper, "DROP key packet during established session nonce=[%d]", nonce);
return Error_UNDELIVERABLE;
}
Assert_true(0);
}
static uint8_t decryptHandshake(struct CryptoAuth_Wrapper* wrapper,
const uint32_t nonce,
struct Message* message,
union Headers_CryptoAuth* header)
{
if (message->length < Headers_CryptoAuth_SIZE) {
cryptoAuthDebug0(wrapper, "DROP runt");
return Error_UNDERSIZE_MESSAGE;
}
// handshake
// nextNonce 0: recieving hello.
// nextNonce 1: recieving key, we sent hello.
// nextNonce 2: recieving first data packet or duplicate hello.
// nextNonce 3: recieving first data packet.
// nextNonce >3: handshake complete
if (knowHerKey(wrapper)) {
if (Bits_memcmp(wrapper->herPerminentPubKey, header->handshake.publicKey, 32)) {
cryptoAuthDebug0(wrapper, "DROP a packet with different public key than this session");
return Error_AUTHENTICATION;
}
} else if (!Bits_isZero(wrapper->herIp6, 16)) {
uint8_t calculatedIp6[16];
AddressCalc_addressForPublicKey(calculatedIp6, header->handshake.publicKey);
if (Bits_memcmp(wrapper->herIp6, calculatedIp6, 16)) {
cryptoAuthDebug0(wrapper, "DROP packet with public key not matching ip6 for session");
return Error_AUTHENTICATION;
}
}
if (wrapper->nextNonce < 2 && nonce == UINT32_MAX && !wrapper->requireAuth) {
// Reset without knowing key is allowed until state reaches 2.
// this is because we don't know that the other end knows our key until we
// have received a valid packet from them.
// We can't allow the upper layer to see this message because it's not authenticated.
if (!knowHerKey(wrapper)) {
Bits_memcpyConst(wrapper->herPerminentPubKey, header->handshake.publicKey, 32);
}
Message_shift(message, -Headers_CryptoAuth_SIZE, NULL);
message->length = 0;
reset(wrapper);
wrapper->user = NULL;
cryptoAuthDebug0(wrapper, "Got a connect-to-me message, sending a hello");
// Send an empty response (to initiate the connection).
encryptHandshake(message, wrapper, 1);
return Error_NONE;
}
String* user = NULL;
uint8_t passwordHashStore[32];
uint8_t* passwordHash = tryAuth(header, passwordHashStore, wrapper, &user);
if (wrapper->requireAuth && !user) {
cryptoAuthDebug0(wrapper, "DROP message because auth was not given");
return Error_AUTHENTICATION;
}
if (passwordHash == NULL && header->handshake.auth.challenge.type != 0) {
cryptoAuthDebug0(wrapper, "DROP message with unrecognized authenticator");
return Error_AUTHENTICATION;
}
// What the nextNonce will become if this packet is valid.
uint32_t nextNonce;
// The secret for decrypting this message.
uint8_t sharedSecret[32];
uint8_t* herPermKey = NULL;
if (nonce < 2) {
if (nonce == 0) {
cryptoAuthDebug(wrapper, "Received a hello packet, using auth: %d",
(passwordHash != NULL));
} else {
cryptoAuthDebug0(wrapper, "Received a repeat hello packet");
}
// Decrypt message with perminent keys.
if (!knowHerKey(wrapper) || wrapper->nextNonce == 0) {
herPermKey = header->handshake.publicKey;
#ifdef Log_DEBUG
if (Bits_isZero(header->handshake.publicKey, 32)) {
cryptoAuthDebug0(wrapper, "Node sent public key of ZERO!");
}
#endif
} else {
herPermKey = wrapper->herPerminentPubKey;
if (Bits_memcmp(header->handshake.publicKey, herPermKey, 32)) {
cryptoAuthDebug0(wrapper, "DROP packet contains different perminent key");
return Error_AUTHENTICATION;
}
}
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
herPermKey,
passwordHash,
wrapper->context->logger);
nextNonce = 2;
} else {
if (nonce == 2) {
cryptoAuthDebug0(wrapper, "Received a key packet");
} else if (nonce == 3) {
cryptoAuthDebug0(wrapper, "Received a repeat key packet");
} else {
cryptoAuthDebug(wrapper, "Received a packet of unknown type! nonce=%u", nonce);
}
if (Bits_memcmp(header->handshake.publicKey, wrapper->herPerminentPubKey, 32)) {
cryptoAuthDebug0(wrapper, "DROP packet contains different perminent key");
return Error_AUTHENTICATION;
}
if (!wrapper->isInitiator) {
cryptoAuthDebug0(wrapper, "DROP a stray key packet");
return Error_AUTHENTICATION;
}
// We sent the hello, this is a key
getSharedSecret(sharedSecret,
wrapper->ourTempPrivKey,
wrapper->herPerminentPubKey,
passwordHash,
wrapper->context->logger);
nextNonce = 4;
}
// Shift it on top of the authenticator before the encrypted public key
Message_shift(message, 48 - Headers_CryptoAuth_SIZE, NULL);
#ifdef Log_KEYS
uint8_t sharedSecretHex[65];
printHexKey(sharedSecretHex, sharedSecret);
uint8_t nonceHex[49];
Hex_encode(nonceHex, 49, header->handshake.nonce, 24);
uint8_t cipherHex[65];
printHexKey(cipherHex, message->bytes);
Log_keys(wrapper->context->logger,
"Decrypting message with:\n"
" nonce: %s\n"
" secret: %s\n"
" cipher: %s\n",
nonceHex, sharedSecretHex, cipherHex);
#endif
// Decrypt her temp public key and the message.
if (decryptRndNonce(header->handshake.nonce, message, sharedSecret) != 0) {
// just in case
Bits_memset(header, 0, Headers_CryptoAuth_SIZE);
cryptoAuthDebug(wrapper, "DROP message with nonce [%d], decryption failed", nonce);
return Error_AUTHENTICATION;
}
Assert_ifParanoid(!Bits_isZero(header->handshake.encryptedTempKey, 32));
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger,
"Unwrapping temp public key:\n"
" %s\n",
tempKeyHex);
#endif
Message_shift(message, -32, NULL);
// Post-decryption checking
if (nonce == 0) {
// A new hello packet
if (!Bits_memcmp(wrapper->herTempPubKey, header->handshake.encryptedTempKey, 32)) {
// possible replay attack or duped packet
cryptoAuthDebug0(wrapper, "DROP dupe hello packet with same temp key");
return Error_AUTHENTICATION;
}
} else if (nonce == 2 && wrapper->nextNonce >= 4) {
// we accept a new key packet and let it change the session since the other end might have
// killed off the session while it was in the midst of setting up.
if (!Bits_memcmp(wrapper->herTempPubKey, header->handshake.encryptedTempKey, 32)) {
Assert_true(!Bits_isZero(wrapper->herTempPubKey, 32));
cryptoAuthDebug0(wrapper, "DROP dupe key packet with same temp key");
return Error_AUTHENTICATION;
}
} else if (nonce == 3 && wrapper->nextNonce >= 4) {
// Got a repeat key packet, make sure the temp key is the same as the one we know.
if (Bits_memcmp(wrapper->herTempPubKey, header->handshake.encryptedTempKey, 32)) {
Assert_true(!Bits_isZero(wrapper->herTempPubKey, 32));
cryptoAuthDebug0(wrapper, "DROP repeat key packet with different temp key");
return Error_AUTHENTICATION;
}
}
// If Alice sent a hello packet then Bob sent a hello packet and they crossed on the wire,
// somebody has to yield and the other has to stand firm otherwise they will either deadlock
// each believing their hello packet is superior or they will livelock, each switching to the
// other's session and never synchronizing.
// In this event whoever has the lower permanent public key wins.
// If we receive a (possibly repeat) key packet
if (nextNonce == 4) {
if (wrapper->nextNonce <= 4) {
// and have not yet begun sending "run" data
Assert_true(wrapper->nextNonce <= nextNonce);
wrapper->nextNonce = nextNonce;
wrapper->user = user;
Bits_memcpyConst(wrapper->herTempPubKey, header->handshake.encryptedTempKey, 32);
} else {
// It's a (possibly repeat) key packet and we have begun sending run data.
// We will change the shared secret to the one specified in the new key packet but
// intentionally avoid de-incrementing the nonce just in case
getSharedSecret(wrapper->sharedSecret,
wrapper->ourTempPrivKey,
header->handshake.encryptedTempKey,
NULL,
wrapper->context->logger);
cryptoAuthDebug0(wrapper, "New key packet but we are already sending data");
}
} else if (nextNonce == 2 && (!wrapper->isInitiator || wrapper->established)) {
// This is a hello packet and we are either in ESTABLISHED state or we are
// not the initiator of the connection.
// If the case is that we are in ESTABLISHED state, the other side tore down the session
// and we have not so lets tear it down.
// If we are not in ESTABLISHED state then we don't allow resetting of the session unless
// they are the sender of the hello packet or their permanent public key is lower.
// this is a tie-breaker in case hello packets cross on the wire.
if (wrapper->established) {
reset(wrapper);
}
// We got a (possibly repeat) hello packet and we have not sent any hello packet,
// new session.
if (wrapper->nextNonce == 3 && nextNonce == 2) {
// We sent a key packet so the next packet is a repeat key but we got another hello
// We'll just keep steaming along sending repeat key packets
nextNonce = 3;
}
Assert_true(wrapper->nextNonce <= nextNonce);
wrapper->nextNonce = nextNonce;
wrapper->user = user;
Bits_memcpyConst(wrapper->herTempPubKey, header->handshake.encryptedTempKey, 32);
} else if (nextNonce == 2
&& Bits_memcmp(header->handshake.publicKey, wrapper->context->pub.publicKey, 32) < 0)
{
// It's a hello and we are the initiator but their permant public key is numerically lower
// than ours, this is so that in the event of two hello packets crossing on the wire, the
// nodes will agree on who is the initiator.
cryptoAuthDebug0(wrapper, "Incoming hello from node with lower key, resetting");
reset(wrapper);
Assert_true(wrapper->nextNonce <= nextNonce);
wrapper->nextNonce = nextNonce;
wrapper->user = user;
Bits_memcpyConst(wrapper->herTempPubKey, header->handshake.encryptedTempKey, 32);
} else {
cryptoAuthDebug0(wrapper, "Incoming hello from node with higher key, not resetting");
}
if (herPermKey && herPermKey != wrapper->herPerminentPubKey) {
Bits_memcpyConst(wrapper->herPerminentPubKey, herPermKey, 32);
}
// If this is a handshake which was initiated in reverse because we
// didn't know the other node's key, now send what we were going to send.
if (wrapper->bufferedMessage) {
// This can only happen when we have received a (maybe repeat) hello packet.
Assert_true(wrapper->nextNonce == 2);
struct Message* bm = wrapper->bufferedMessage;
wrapper->bufferedMessage = NULL;
cryptoAuthDebug0(wrapper, "Sending buffered message");
sendMessage(bm, &wrapper->externalInterface);
Allocator_free(bm->alloc);
}
if (message->length == 0 && Headers_isSetupPacket(&header->handshake.auth)) {
return Error_NONE;
}
Bits_memset(&wrapper->replayProtector, 0, sizeof(struct ReplayProtector));
setRequiredPadding(wrapper);
return callReceivedMessage(wrapper, message);
}
static uint8_t encryptHandshake(struct Message* message,
struct CryptoAuth_Wrapper* wrapper,
int setupMessage)
{
Message_shift(message, sizeof(union Headers_CryptoAuth), NULL);
union Headers_CryptoAuth* header = (union Headers_CryptoAuth*) message->bytes;
// garbage the auth challenge and set the nonce which follows it
Random_bytes(wrapper->context->rand, (uint8_t*) &header->handshake.auth,
sizeof(union Headers_AuthChallenge) + 24);
// set the permanent key
Bits_memcpyConst(&header->handshake.publicKey, wrapper->context->pub.publicKey, 32);
if (!knowHerKey(wrapper)) {
return genReverseHandshake(message, wrapper, header);
} else if (!Bits_isZero(wrapper->herIp6, 16)) {
// If someone starts a CA session and then discovers the key later and memcpy's it into the
// result of getHerPublicKey() then we want to make sure they didn't memcpy in an invalid
// key.
uint8_t calculatedIp6[16];
AddressCalc_addressForPublicKey(calculatedIp6, wrapper->herPerminentPubKey);
Assert_true(!Bits_memcmp(wrapper->herIp6, calculatedIp6, 16));
}
if (wrapper->bufferedMessage) {
// We wanted to send a message but we didn't know the peer's key so we buffered it
// and sent a connectToMe.
// Now we just discovered their key and we're sending a hello packet.
// Lets send 2 hello packets instead and on one will attach our buffered message.
// This can never happen when the machine is beyond the first hello packet because
// it should have been sent either by this or in the recipet of a hello packet from
// the other node.
Assert_true(wrapper->nextNonce == 0);
struct Message* bm = wrapper->bufferedMessage;
wrapper->bufferedMessage = NULL;
cryptoAuthDebug0(wrapper, "Sending buffered message");
sendMessage(bm, &wrapper->externalInterface);
Allocator_free(bm->alloc);
}
// Password auth
uint8_t* passwordHash = NULL;
struct CryptoAuth_Auth auth;
if (wrapper->password != NULL) {
passwordHash = hashPassword(&auth, wrapper->password, wrapper->authType);
Bits_memcpyConst(header->handshake.auth.bytes,
&auth.challenge,
sizeof(union Headers_AuthChallenge));
}
header->handshake.auth.challenge.type = wrapper->authType;
// Packet authentication option is deprecated, it must always be enabled.
Headers_setPacketAuthRequired(&header->handshake.auth, 1);
// This is a special packet which the user should never see.
Headers_setSetupPacket(&header->handshake.auth, setupMessage);
// Set the session state
uint32_t sessionState_be = Endian_hostToBigEndian32(wrapper->nextNonce);
header->nonce = sessionState_be;
if (wrapper->nextNonce == 0 || wrapper->nextNonce == 2) {
// If we're sending a hello or a key
// Here we make up a temp keypair
Random_bytes(wrapper->context->rand, wrapper->ourTempPrivKey, 32);
crypto_scalarmult_curve25519_base(wrapper->ourTempPubKey, wrapper->ourTempPrivKey);
#ifdef Log_KEYS
uint8_t tempPrivateKeyHex[65];
Hex_encode(tempPrivateKeyHex, 65, wrapper->ourTempPrivKey, 32);
uint8_t tempPubKeyHex[65];
Hex_encode(tempPubKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger, "Generating temporary keypair\n"
" myTempPrivateKey=%s\n"
" myTempPublicKey=%s\n",
tempPrivateKeyHex, tempPubKeyHex);
#endif
}
Bits_memcpyConst(header->handshake.encryptedTempKey, wrapper->ourTempPubKey, 32);
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger,
"Wrapping temp public key:\n"
" %s\n",
tempKeyHex);
#endif
cryptoAuthDebug(wrapper, "Sending %s%s packet",
((wrapper->nextNonce & 1) ? "repeat " : ""),
((wrapper->nextNonce < 2) ? "hello" : "key"));
uint8_t sharedSecret[32];
if (wrapper->nextNonce < 2) {
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
wrapper->herPerminentPubKey,
passwordHash,
wrapper->context->logger);
wrapper->isInitiator = true;
Assert_true(wrapper->nextNonce <= 1);
wrapper->nextNonce = 1;
} else {
// Handshake2
// herTempPubKey was set by receiveMessage()
Assert_ifParanoid(!Bits_isZero(wrapper->herTempPubKey, 32));
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
wrapper->herTempPubKey,
passwordHash,
wrapper->context->logger);
Assert_true(wrapper->nextNonce <= 3);
wrapper->nextNonce = 3;
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, wrapper->herTempPubKey, 32);
Log_keys(wrapper->context->logger,
"Using their temp public key:\n"
" %s\n",
tempKeyHex);
#endif
}
// Shift message over the encryptedTempKey field.
Message_shift(message, 32 - Headers_CryptoAuth_SIZE, NULL);
encryptRndNonce(header->handshake.nonce, message, sharedSecret);
#ifdef Log_KEYS
uint8_t sharedSecretHex[65];
printHexKey(sharedSecretHex, sharedSecret);
uint8_t nonceHex[49];
Hex_encode(nonceHex, 49, header->handshake.nonce, 24);
uint8_t cipherHex[65];
printHexKey(cipherHex, message->bytes);
Log_keys(wrapper->context->logger,
"Encrypting message with:\n"
" nonce: %s\n"
" secret: %s\n"
" cipher: %s\n",
nonceHex, sharedSecretHex, cipherHex);
#endif
// Shift it back -- encryptRndNonce adds 16 bytes of authenticator.
Message_shift(message, Headers_CryptoAuth_SIZE - 32 - 16, NULL);
return wrapper->wrappedInterface->sendMessage(message, wrapper->wrappedInterface);
}
static uint8_t decryptHandshake(struct CryptoAuth_Wrapper* wrapper,
const uint32_t nonce,
struct Message* message,
union Headers_CryptoAuth* header)
{
if (message->length < Headers_CryptoAuth_SIZE) {
cryptoAuthDebug0(wrapper, "Dropped runt packet");
return Error_UNDERSIZE_MESSAGE;
}
// handshake
// nextNonce 0: recieving hello.
// nextNonce 1: recieving key, we sent hello.
// nextNonce 2: recieving first data packet or duplicate hello.
// nextNonce 3: recieving first data packet.
// nextNonce >3: handshake complete
if (wrapper->nextNonce < 2 && nonce == UINT32_MAX && !wrapper->requireAuth) {
// Reset without knowing key is allowed until state reaches 2.
// this is because we don't know that the other end knows our key until we
// have received a valid packet from them.
// We can't allow the upper layer to see this message because it's not authenticated.
if (!knowHerKey(wrapper)) {
Bits_memcpyConst(wrapper->herPerminentPubKey, header->handshake.publicKey, 32);
}
Message_shift(message, -Headers_CryptoAuth_SIZE);
message->length = 0;
wrapper->nextNonce = 0;
wrapper->user = NULL;
cryptoAuthDebug0(wrapper, "Got a connect-to-me message, sending a hello");
// Send an empty response (to initiate the connection).
encryptHandshake(message, wrapper);
return Error_NONE;
}
void* user = NULL;
uint8_t passwordHashStore[32];
uint8_t* passwordHash = tryAuth(header, passwordHashStore, wrapper, &user);
if (wrapper->requireAuth && !user) {
cryptoAuthDebug0(wrapper, "Dropping message because auth was not given");
return Error_AUTHENTICATION;
}
if (passwordHash == NULL && header->handshake.auth.challenge.type != 0) {
cryptoAuthDebug0(wrapper,
"Dropping message because it contans an authenticator which is unrecognized");
return Error_AUTHENTICATION;
}
// What the nextNonce will become if this packet is valid.
uint32_t nextNonce;
// The secret for decrypting this message.
uint8_t sharedSecret[32];
uint8_t* herPermKey = NULL;
if (nonce < 2) {
if (nonce == 0) {
cryptoAuthDebug(wrapper, "Received a hello packet, using auth: %d",
(passwordHash != NULL));
} else {
cryptoAuthDebug0(wrapper, "Received a repeat hello packet");
}
// Decrypt message with perminent keys.
if (!knowHerKey(wrapper) || wrapper->nextNonce == 0) {
herPermKey = header->handshake.publicKey;
#ifdef Log_DEBUG
if (Bits_isZero(header->handshake.publicKey, 32)) {
cryptoAuthDebug0(wrapper, "Node sent public key of ZERO!");
}
#endif
} else {
herPermKey = wrapper->herPerminentPubKey;
if (Bits_memcmp(header->handshake.publicKey, herPermKey, 32)) {
cryptoAuthDebug0(wrapper, "Packet contains different perminent key");
return Error_AUTHENTICATION;
}
}
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
herPermKey,
passwordHash,
wrapper->context->logger);
nextNonce = 2;
} else {
if (nonce == 2) {
cryptoAuthDebug0(wrapper, "Received a key packet");
} else if (nonce == 3) {
cryptoAuthDebug0(wrapper, "Received a repeat key packet");
} else {
cryptoAuthDebug(wrapper, "Received a packet of unknown type! nonce=%u", nonce);
}
if (Bits_memcmp(header->handshake.publicKey, wrapper->herPerminentPubKey, 32)) {
cryptoAuthDebug0(wrapper, "Packet contains different perminent key");
return Error_AUTHENTICATION;
}
// We sent the hello, this is a key
getSharedSecret(sharedSecret,
wrapper->secret,
wrapper->herPerminentPubKey,
passwordHash,
wrapper->context->logger);
nextNonce = 4;
}
// Shift it on top of the authenticator before the encrypted public key
Message_shift(message, 48 - Headers_CryptoAuth_SIZE);
#ifdef Log_KEYS
uint8_t sharedSecretHex[65];
printHexKey(sharedSecretHex, sharedSecret);
uint8_t nonceHex[49];
Hex_encode(nonceHex, 49, header->handshake.nonce, 24);
uint8_t cipherHex[65];
printHexKey(cipherHex, message->bytes);
Log_keys(wrapper->context->logger,
"Decrypting message with:\n"
" nonce: %s\n"
" secret: %s\n"
" cipher: %s\n",
nonceHex, sharedSecretHex, cipherHex);
#endif
// Decrypt her temp public key and the message.
if (decryptRndNonce(header->handshake.nonce, message, sharedSecret) != 0) {
// just in case
Bits_memset(header, 0, Headers_CryptoAuth_SIZE);
cryptoAuthDebug0(wrapper, "Dropped message because authenticated decryption failed");
return Error_AUTHENTICATION;
}
wrapper->user = user;
Bits_memcpyConst(wrapper->tempKey, header->handshake.encryptedTempKey, 32);
#ifdef Log_DEBUG
Assert_true(!Bits_isZero(header->handshake.encryptedTempKey, 32));
#endif
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, wrapper->tempKey, 32);
Log_keys(wrapper->context->logger,
"Unwrapping temp public key:\n"
" %s\n",
tempKeyHex);
#endif
Message_shift(message, -32);
wrapper->nextNonce = nextNonce;
if (nextNonce == 2) {
wrapper->isInitiator = false;
}
if (herPermKey && herPermKey != wrapper->herPerminentPubKey) {
Bits_memcpyConst(wrapper->herPerminentPubKey, herPermKey, 32);
}
// If this is a handshake which was initiated in reverse because we
// didn't know the other node's key, now send what we were going to send.
if (wrapper->hasBufferedMessage && message->length == 0) {
cryptoAuthDebug0(wrapper, "Sending buffered message");
sendMessage(wrapper->bufferedMessage, &wrapper->externalInterface);
wrapper->hasBufferedMessage = false;
return Error_NONE;
} else if (wrapper->hasBufferedMessage) {
cryptoAuthDebug0(wrapper, "There is a buffered message");
}
Bits_memset(&wrapper->replayProtector, 0, sizeof(struct ReplayProtector));
setRequiredPadding(wrapper);
return callReceivedMessage(wrapper, message);
}
static uint8_t encryptHandshake(struct Message* message, struct CryptoAuth_Wrapper* wrapper)
{
Message_shift(message, sizeof(union Headers_CryptoAuth));
union Headers_CryptoAuth* header = (union Headers_CryptoAuth*) message->bytes;
// garbage the auth field to frustrate DPI and set the nonce (next 24 bytes after the auth)
Random_bytes(wrapper->context->rand,
(uint8_t*) &header->handshake.auth,
sizeof(union Headers_AuthChallenge) + 24);
Bits_memcpyConst(&header->handshake.publicKey, wrapper->context->pub.publicKey, 32);
if (!knowHerKey(wrapper)) {
return genReverseHandshake(message, wrapper, header);
}
// Password auth
uint8_t* passwordHash = NULL;
struct CryptoAuth_Auth auth;
if (wrapper->password != NULL) {
passwordHash = hashPassword(&auth, wrapper->password, wrapper->authType);
Bits_memcpyConst(header->handshake.auth.bytes,
&auth.challenge,
sizeof(union Headers_AuthChallenge));
}
header->handshake.auth.challenge.type = wrapper->authType;
Headers_setPacketAuthRequired(&header->handshake.auth, wrapper->authenticatePackets);
// set the session state
uint32_t sessionState_be = Endian_hostToBigEndian32(wrapper->nextNonce);
header->nonce = sessionState_be;
if (wrapper->nextNonce == 0 || wrapper->nextNonce == 2) {
// If we're sending a hello or a key
Random_bytes(wrapper->context->rand, wrapper->secret, 32);
crypto_scalarmult_curve25519_base(header->handshake.encryptedTempKey, wrapper->secret);
#ifdef Log_KEYS
uint8_t tempPrivateKeyHex[65];
Hex_encode(tempPrivateKeyHex, 65, wrapper->secret, 32);
uint8_t tempPubKeyHex[65];
Hex_encode(tempPubKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger, "Generating temporary keypair\n"
" myTempPrivateKey=%s\n"
" myTempPublicKey=%s\n",
tempPrivateKeyHex, tempPubKeyHex);
#endif
if (wrapper->nextNonce == 0) {
Bits_memcpyConst(wrapper->tempKey, header->handshake.encryptedTempKey, 32);
}
#ifdef Log_DEBUG
Assert_true(!Bits_isZero(header->handshake.encryptedTempKey, 32));
Assert_true(!Bits_isZero(wrapper->secret, 32));
#endif
} else if (wrapper->nextNonce == 3) {
// Dupe key
// If nextNonce is 1 then we have our pubkey stored in wrapper->tempKey,
// If nextNonce is 3 we need to recalculate it each time
// because tempKey the final secret.
crypto_scalarmult_curve25519_base(header->handshake.encryptedTempKey,
wrapper->secret);
} else {
// Dupe hello
// wrapper->nextNonce == 1
// Our public key is cached in wrapper->tempKey so lets copy it out.
Bits_memcpyConst(header->handshake.encryptedTempKey, wrapper->tempKey, 32);
}
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger,
"Wrapping temp public key:\n"
" %s\n",
tempKeyHex);
#endif
uint8_t sharedSecret[32];
if (wrapper->nextNonce < 2) {
if (wrapper->nextNonce == 0) {
cryptoAuthDebug0(wrapper, "Sending hello packet");
} else {
cryptoAuthDebug0(wrapper, "Sending repeat hello packet");
}
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
wrapper->herPerminentPubKey,
passwordHash,
wrapper->context->logger);
wrapper->isInitiator = true;
wrapper->nextNonce = 1;
} else {
if (wrapper->nextNonce == 2) {
cryptoAuthDebug0(wrapper, "Sending key packet");
} else {
cryptoAuthDebug0(wrapper, "Sending repeat key packet");
}
// Handshake2 wrapper->tempKey holds her public temp key.
// it was put there by receiveMessage()
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
wrapper->tempKey,
passwordHash,
wrapper->context->logger);
wrapper->nextNonce = 3;
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, wrapper->tempKey, 32);
Log_keys(wrapper->context->logger,
"Using their temp public key:\n"
" %s\n",
tempKeyHex);
#endif
}
// Shift message over the encryptedTempKey field.
Message_shift(message, 32 - Headers_CryptoAuth_SIZE);
encryptRndNonce(header->handshake.nonce, message, sharedSecret);
#ifdef Log_KEYS
uint8_t sharedSecretHex[65];
printHexKey(sharedSecretHex, sharedSecret);
uint8_t nonceHex[49];
Hex_encode(nonceHex, 49, header->handshake.nonce, 24);
uint8_t cipherHex[65];
printHexKey(cipherHex, message->bytes);
Log_keys(wrapper->context->logger,
"Encrypting message with:\n"
" nonce: %s\n"
" secret: %s\n"
" cipher: %s\n",
nonceHex, sharedSecretHex, cipherHex);
#endif
#ifdef Log_DEBUG
Assert_true(!Bits_isZero(header->handshake.encryptedTempKey, 32));
#endif
// Shift it back -- encryptRndNonce adds 16 bytes of authenticator.
Message_shift(message, Headers_CryptoAuth_SIZE - 32 - 16);
return wrapper->wrappedInterface->sendMessage(message, wrapper->wrappedInterface);
}
/** @return 0 on success, -1 otherwise. */
int CryptoAuth_decrypt(struct CryptoAuth_Session* sessionPub, struct Message* msg)
{
struct CryptoAuth_Session_pvt* session =
Identity_check((struct CryptoAuth_Session_pvt*) sessionPub);
union CryptoHeader* header = (union CryptoHeader*) msg->bytes;
if (msg->length < 20) {
cryptoAuthDebug0(session, "DROP runt");
return -1;
}
Assert_true(msg->padding >= 12 || "need at least 12 bytes of padding in incoming message");
Assert_true(!((uintptr_t)msg->bytes % 4) || !"alignment fault");
Assert_true(!(msg->capacity % 4) || !"length fault");
Message_shift(msg, -4, NULL);
uint32_t nonce = Endian_bigEndianToHost32(header->nonce);
if (!session->established) {
if (nonce > 3) {
if (session->nextNonce < 3) {
// This is impossible because we have not exchanged hello and key messages.
cryptoAuthDebug0(session, "DROP Received a run message to an un-setup session");
return -1;
}
cryptoAuthDebug(session, "Trying final handshake step, nonce=%u\n", nonce);
uint8_t secret[32];
Assert_ifParanoid(!Bits_isZero(session->ourTempPrivKey, 32));
Assert_ifParanoid(!Bits_isZero(session->herTempPubKey, 32));
getSharedSecret(secret,
session->ourTempPrivKey,
session->herTempPubKey,
NULL,
session->context->logger);
if (decryptMessage(session, nonce, msg, secret)) {
cryptoAuthDebug0(session, "Final handshake step succeeded");
Bits_memcpyConst(session->sharedSecret, secret, 32);
// Now we're in run mode, no more handshake packets will be accepted
Bits_memset(session->ourTempPrivKey, 0, 32);
Bits_memset(session->ourTempPubKey, 0, 32);
Bits_memset(session->herTempPubKey, 0, 32);
session->established = true;
session->nextNonce += 3;
updateTime(session, msg);
return 0;
}
cryptoAuthDebug0(session, "DROP Final handshake step failed");
return -1;
}
Message_shift(msg, 4, NULL);
return decryptHandshake(session, nonce, msg, header);
} else if (nonce > 3) {
Assert_ifParanoid(!Bits_isZero(session->sharedSecret, 32));
if (decryptMessage(session, nonce, msg, session->sharedSecret)) {
updateTime(session, msg);
return 0;
} else {
cryptoAuthDebug0(session, "DROP Failed to decrypt message");
return -1;
}
} else if (nonce < 2) {
cryptoAuthDebug(session, "hello packet during established session nonce=[%d]", nonce);
Message_shift(msg, 4, NULL);
return decryptHandshake(session, nonce, msg, header);
} else {
// setup keys are already zeroed, not much we can do here.
cryptoAuthDebug(session, "DROP key packet during established session nonce=[%d]", nonce);
return -1;
}
Assert_true(0);
}
static Gcc_USE_RET int decryptHandshake(struct CryptoAuth_Session_pvt* session,
const uint32_t nonce,
struct Message* message,
union CryptoHeader* header)
{
if (message->length < CryptoHeader_SIZE) {
cryptoAuthDebug0(session, "DROP runt");
return -1;
}
// handshake
// nextNonce 0: recieving hello.
// nextNonce 1: recieving key, we sent hello.
// nextNonce 2: recieving first data packet or duplicate hello.
// nextNonce 3: recieving first data packet.
// nextNonce >3: handshake complete
if (knowHerKey(session)) {
if (Bits_memcmp(session->pub.herPublicKey, header->handshake.publicKey, 32)) {
cryptoAuthDebug0(session, "DROP a packet with different public key than this session");
return -1;
}
} else if (Bits_isZero(session->pub.herIp6, 16)) {
// ok fallthrough
} else if (!ip6MatchesKey(session->pub.herIp6, header->handshake.publicKey)) {
cryptoAuthDebug0(session, "DROP packet with public key not matching ip6 for session");
return -1;
}
struct CryptoAuth_User* userObj = getAuth(&header->handshake.auth, session->context);
uint8_t* restrictedToip6 = NULL;
uint8_t* passwordHash = NULL;
if (userObj) {
passwordHash = userObj->secret;
if (userObj->restrictedToip6[0]) {
restrictedToip6 = userObj->restrictedToip6;
if (!ip6MatchesKey(restrictedToip6, header->handshake.publicKey)) {
cryptoAuthDebug0(session, "DROP packet with key not matching restrictedToip6");
return -1;
}
}
}
if (session->requireAuth && !userObj) {
cryptoAuthDebug0(session, "DROP message because auth was not given");
return -1;
}
if (!userObj && header->handshake.auth.challenge.type != 0) {
cryptoAuthDebug0(session, "DROP message with unrecognized authenticator");
return -1;
}
// What the nextNonce will become if this packet is valid.
uint32_t nextNonce;
// The secret for decrypting this message.
uint8_t sharedSecret[32];
uint8_t* herPermKey = session->pub.herPublicKey;
if (nonce < 2) {
if (nonce == 0) {
cryptoAuthDebug(session, "Received a hello packet, using auth: %d",
(userObj != NULL));
} else {
cryptoAuthDebug0(session, "Received a repeat hello packet");
}
// Decrypt message with perminent keys.
if (!knowHerKey(session) || session->nextNonce == 0) {
herPermKey = header->handshake.publicKey;
if (Defined(Log_DEBUG) && Bits_isZero(header->handshake.publicKey, 32)) {
cryptoAuthDebug0(session, "DROP Node sent public key of ZERO!");
// This is strictly informational, we will not alter the execution path for it.
}
}
getSharedSecret(sharedSecret,
session->context->privateKey,
herPermKey,
passwordHash,
session->context->logger);
nextNonce = 2;
} else {
if (nonce == 2) {
cryptoAuthDebug0(session, "Received a key packet");
} else {
Assert_true(nonce == 3);
cryptoAuthDebug0(session, "Received a repeat key packet");
}
if (Bits_memcmp(header->handshake.publicKey, session->pub.herPublicKey, 32)) {
cryptoAuthDebug0(session, "DROP packet contains different perminent key");
return -1;
}
if (!session->isInitiator) {
cryptoAuthDebug0(session, "DROP a stray key packet");
return -1;
}
// We sent the hello, this is a key
getSharedSecret(sharedSecret,
session->ourTempPrivKey,
session->pub.herPublicKey,
passwordHash,
session->context->logger);
nextNonce = 4;
}
// Shift it on top of the authenticator before the encrypted public key
Message_shift(message, 48 - CryptoHeader_SIZE, NULL);
if (Defined(Log_KEYS)) {
uint8_t sharedSecretHex[65];
printHexKey(sharedSecretHex, sharedSecret);
uint8_t nonceHex[49];
Hex_encode(nonceHex, 49, header->handshake.nonce, 24);
uint8_t cipherHex[65];
printHexKey(cipherHex, message->bytes);
Log_keys(session->context->logger,
"Decrypting message with:\n"
" nonce: %s\n"
" secret: %s\n"
" cipher: %s\n",
nonceHex, sharedSecretHex, cipherHex);
}
// Decrypt her temp public key and the message.
if (decryptRndNonce(header->handshake.nonce, message, sharedSecret)) {
// just in case
Bits_memset(header, 0, CryptoHeader_SIZE);
cryptoAuthDebug(session, "DROP message with nonce [%d], decryption failed", nonce);
return -1;
}
if (Bits_isZero(header->handshake.encryptedTempKey, 32)) {
// we need to reject 0 public keys outright because they will be confused with "unknown"
cryptoAuthDebug0(session, "DROP message with zero as temp public key");
return -1;
}
if (Defined(Log_KEYS)) {
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(session->context->logger,
"Unwrapping temp public key:\n"
" %s\n",
tempKeyHex);
}
Message_shift(message, -32, NULL);
// Post-decryption checking
if (nonce == 0) {
// A new hello packet
if (!Bits_memcmp(session->herTempPubKey, header->handshake.encryptedTempKey, 32)) {
// possible replay attack or duped packet
cryptoAuthDebug0(session, "DROP dupe hello packet with same temp key");
return -1;
}
} else if (nonce == 2 && session->nextNonce >= 4) {
// we accept a new key packet and let it change the session since the other end might have
// killed off the session while it was in the midst of setting up.
// This is NOT a repeat key packet because it's nonce is 2, not 3
if (!Bits_memcmp(session->herTempPubKey, header->handshake.encryptedTempKey, 32)) {
Assert_true(!Bits_isZero(session->herTempPubKey, 32));
cryptoAuthDebug0(session, "DROP dupe key packet with same temp key");
return -1;
}
} else if (nonce == 3 && session->nextNonce >= 4) {
// Got a repeat key packet, make sure the temp key is the same as the one we know.
if (Bits_memcmp(session->herTempPubKey, header->handshake.encryptedTempKey, 32)) {
Assert_true(!Bits_isZero(session->herTempPubKey, 32));
cryptoAuthDebug0(session, "DROP repeat key packet with different temp key");
return -1;
}
}
// If Alice sent a hello packet then Bob sent a hello packet and they crossed on the wire,
// somebody has to yield and the other has to stand firm otherwise they will either deadlock
// each believing their hello packet is superior or they will livelock, each switching to the
// other's session and never synchronizing.
// In this event whoever has the lower permanent public key wins.
// If we receive a (possibly repeat) key packet
if (nextNonce == 4) {
if (session->nextNonce <= 4) {
// and have not yet begun sending "run" data
Bits_memcpyConst(session->herTempPubKey, header->handshake.encryptedTempKey, 32);
} else {
// It's a (possibly repeat) key packet and we have begun sending run data.
// We will change the shared secret to the one specified in the new key packet but
// intentionally avoid de-incrementing the nonce just in case
getSharedSecret(session->sharedSecret,
session->ourTempPrivKey,
header->handshake.encryptedTempKey,
NULL,
session->context->logger);
nextNonce = session->nextNonce + 1;
cryptoAuthDebug0(session, "New key packet but we are already sending data");
}
} else if (nextNonce != 2) {
Assert_true(!"should never happen");
} else if (!session->isInitiator || session->established) {
// This is a hello packet and we are either in ESTABLISHED state or we are
// not the initiator of the connection.
// If the case is that we are in ESTABLISHED state, the other side tore down the session
// and we have not so lets tear it down.
// If we are not in ESTABLISHED state then we don't allow resetting of the session unless
// they are the sender of the hello packet or their permanent public key is lower.
// this is a tie-breaker in case hello packets cross on the wire.
if (session->established) {
cryptoAuthDebug0(session, "new hello during established session, resetting");
reset(session);
}
// We got a (possibly repeat) hello packet and we have not sent any hello packet,
// new session.
if (session->nextNonce == 3) {
// We sent a key packet so the next packet is a repeat key but we got another hello
// We'll just keep steaming along sending repeat key packets
nextNonce = 3;
}
Bits_memcpyConst(session->herTempPubKey, header->handshake.encryptedTempKey, 32);
} else if (Bits_memcmp(header->handshake.publicKey, session->context->pub.publicKey, 32) < 0) {
// It's a hello and we are the initiator but their permant public key is numerically lower
// than ours, this is so that in the event of two hello packets crossing on the wire, the
// nodes will agree on who is the initiator.
cryptoAuthDebug0(session, "Incoming hello from node with lower key, resetting");
reset(session);
Bits_memcpyConst(session->herTempPubKey, header->handshake.encryptedTempKey, 32);
} else {
cryptoAuthDebug0(session, "DROP Incoming hello from node with higher key, not resetting");
return -1;
}
if (herPermKey && herPermKey != session->pub.herPublicKey) {
Bits_memcpyConst(session->pub.herPublicKey, herPermKey, 32);
}
if (restrictedToip6) {
Bits_memcpyConst(session->pub.herIp6, restrictedToip6, 16);
}
// Nonces can never go backward and can only "not advance" if they're 0,1,2,3,4 session state.
Assert_true(session->nextNonce < nextNonce ||
(session->nextNonce <= 4 && nextNonce == session->nextNonce)
);
session->nextNonce = nextNonce;
Bits_memset(&session->pub.replayProtector, 0, sizeof(struct ReplayProtector));
return 0;
}
static uint8_t encryptHandshake(struct Message* message,
struct CryptoAuth_Wrapper* wrapper,
int setupMessage)
{
Message_shift(message, sizeof(union Headers_CryptoAuth));
union Headers_CryptoAuth* header = (union Headers_CryptoAuth*) message->bytes;
// garbage the auth challenge and set the nonce which follows it
Random_bytes(wrapper->context->rand, (uint8_t*) &header->handshake.auth,
sizeof(union Headers_AuthChallenge) + 24);
// set the permanent key
Bits_memcpyConst(&header->handshake.publicKey, wrapper->context->pub.publicKey, 32);
if (!knowHerKey(wrapper)) {
return genReverseHandshake(message, wrapper, header);
}
if (wrapper->bufferedMessage) {
// We wanted to send a message but we didn't know the peer's key so we buffered it
// and sent a connectToMe, this or it's reply was lost in the network.
// Now we just discovered their key and we're sending a hello packet.
// Lets send 2 hello packets instead and on one will attach our buffered message.
// This can never happen when the machine is beyond the first hello packet because
// it should have been sent either by this or in the recipet of a hello packet from
// the other node.
Assert_true(wrapper->nextNonce == 0);
struct Message* bm = wrapper->bufferedMessage;
wrapper->bufferedMessage = NULL;
cryptoAuthDebug0(wrapper, "Sending buffered message");
sendMessage(bm, &wrapper->externalInterface);
Allocator_free(bm->alloc);
}
// Password auth
uint8_t* passwordHash = NULL;
struct CryptoAuth_Auth auth;
if (wrapper->password != NULL) {
passwordHash = hashPassword(&auth, wrapper->password, wrapper->authType);
Bits_memcpyConst(header->handshake.auth.bytes,
&auth.challenge,
sizeof(union Headers_AuthChallenge));
}
header->handshake.auth.challenge.type = wrapper->authType;
Headers_setPacketAuthRequired(&header->handshake.auth, wrapper->authenticatePackets);
// This is a special packet which the user should never see.
Headers_setSetupPacket(&header->handshake.auth, setupMessage);
// Set the session state
uint32_t sessionState_be = Endian_hostToBigEndian32(wrapper->nextNonce);
header->nonce = sessionState_be;
if (wrapper->nextNonce == 0 || wrapper->nextNonce == 2) {
// If we're sending a hello or a key
Random_bytes(wrapper->context->rand, wrapper->secret, 32);
crypto_scalarmult_curve25519_base(header->handshake.encryptedTempKey, wrapper->secret);
#ifdef Log_KEYS
uint8_t tempPrivateKeyHex[65];
Hex_encode(tempPrivateKeyHex, 65, wrapper->secret, 32);
uint8_t tempPubKeyHex[65];
Hex_encode(tempPubKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger, "Generating temporary keypair\n"
" myTempPrivateKey=%s\n"
" myTempPublicKey=%s\n",
tempPrivateKeyHex, tempPubKeyHex);
#endif
if (wrapper->nextNonce == 0) {
Bits_memcpyConst(wrapper->tempKey, header->handshake.encryptedTempKey, 32);
}
#ifdef Log_DEBUG
Assert_true(!Bits_isZero(header->handshake.encryptedTempKey, 32));
Assert_true(!Bits_isZero(wrapper->secret, 32));
#endif
} else if (wrapper->nextNonce == 3) {
// Dupe key
// If nextNonce is 1 then we have our pubkey stored in wrapper->tempKey,
// If nextNonce is 3 we need to recalculate it each time
// because tempKey the final secret.
crypto_scalarmult_curve25519_base(header->handshake.encryptedTempKey,
wrapper->secret);
} else {
// Dupe hello
// wrapper->nextNonce == 1
// Our public key is cached in wrapper->tempKey so lets copy it out.
Bits_memcpyConst(header->handshake.encryptedTempKey, wrapper->tempKey, 32);
}
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, header->handshake.encryptedTempKey, 32);
Log_keys(wrapper->context->logger,
"Wrapping temp public key:\n"
" %s\n",
tempKeyHex);
#endif
cryptoAuthDebug(wrapper, "Sending %s%s packet",
((wrapper->nextNonce & 1) ? "repeat " : ""),
((wrapper->nextNonce < 2) ? "hello" : "key"));
uint8_t sharedSecret[32];
if (wrapper->nextNonce < 2) {
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
wrapper->herPerminentPubKey,
passwordHash,
wrapper->context->logger);
wrapper->isInitiator = true;
wrapper->nextNonce = 1;
} else {
// Handshake2 wrapper->tempKey holds her public temp key.
// it was put there by receiveMessage()
getSharedSecret(sharedSecret,
wrapper->context->privateKey,
wrapper->tempKey,
passwordHash,
wrapper->context->logger);
wrapper->nextNonce = 3;
#ifdef Log_KEYS
uint8_t tempKeyHex[65];
Hex_encode(tempKeyHex, 65, wrapper->tempKey, 32);
Log_keys(wrapper->context->logger,
"Using their temp public key:\n"
" %s\n",
tempKeyHex);
#endif
}
// Shift message over the encryptedTempKey field.
Message_shift(message, 32 - Headers_CryptoAuth_SIZE);
encryptRndNonce(header->handshake.nonce, message, sharedSecret);
#ifdef Log_KEYS
uint8_t sharedSecretHex[65];
printHexKey(sharedSecretHex, sharedSecret);
uint8_t nonceHex[49];
Hex_encode(nonceHex, 49, header->handshake.nonce, 24);
uint8_t cipherHex[65];
printHexKey(cipherHex, message->bytes);
Log_keys(wrapper->context->logger,
"Encrypting message with:\n"
" nonce: %s\n"
" secret: %s\n"
" cipher: %s\n",
nonceHex, sharedSecretHex, cipherHex);
#endif
#ifdef Log_DEBUG
Assert_true(!Bits_isZero(header->handshake.encryptedTempKey, 32));
#endif
// Shift it back -- encryptRndNonce adds 16 bytes of authenticator.
Message_shift(message, Headers_CryptoAuth_SIZE - 32 - 16);
return wrapper->wrappedInterface->sendMessage(message, wrapper->wrappedInterface);
}