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ZeroTierOne/core/Peer.cpp
Adam Ierymenko f898029241
formatting, aes-gmac-siv crate
2021-07-14 15:38:37 -04:00

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/*
* Copyright (c)2013-2021 ZeroTier, Inc.
*
* Use of this software is governed by the Business Source License included
* in the LICENSE.TXT file in the project's root directory.
*
* Change Date: 2026-01-01
*
* On the date above, in accordance with the Business Source License, use
* of this software will be governed by version 2.0 of the Apache License.
*/
/****/
#include "Peer.hpp"
#include "Constants.hpp"
#include "Context.hpp"
#include "Endpoint.hpp"
#include "Expect.hpp"
#include "InetAddress.hpp"
#include "Protocol.hpp"
#include "SelfAwareness.hpp"
#include "Topology.hpp"
#include "Trace.hpp"
namespace ZeroTier {
// An arbitrary byte to send in single byte probes, incremented on each probe.
static uint8_t s_arbitraryByte = (uint8_t)Utils::random();
Peer::Peer() : m_key((uintptr_t)&m_identityKey), m_keyRenegotiationNeeded(false), m_lastReceive(0), m_lastSend(0), m_lastSentHello(0), m_lastWhoisRequestReceived(0), m_lastEchoRequestReceived(0), m_lastProbeReceived(0), m_alivePathCount(0), m_bestPath(0), m_vProto(0), m_vMajor(0), m_vMinor(0), m_vRevision(0) {}
Peer::~Peer() { Utils::burn(m_helloMacKey, sizeof(m_helloMacKey)); }
bool Peer::init(const Context &ctx, const CallContext &cc, const Identity &peerIdentity)
{
RWMutex::Lock l(m_lock);
m_id = peerIdentity;
uint8_t k[ZT_SYMMETRIC_KEY_SIZE];
if (unlikely(!ctx.identity.agree(peerIdentity, k)))
return false;
m_identityKey.init(cc.ticks, k);
Utils::burn(k, sizeof(k));
m_deriveSecondaryIdentityKeys();
return true;
}
void Peer::received(const Context &ctx, const CallContext &cc, const SharedPtr<Path> &path, const unsigned int hops, const uint64_t packetId, const unsigned int payloadLength, const Protocol::Verb verb, const Protocol::Verb /*inReVerb*/)
{
m_lastReceive.store(cc.ticks, std::memory_order_relaxed);
m_inMeter.log(cc.ticks, payloadLength);
// NOTE: in the most common scenario we will be talking via the best path.
// This does a check without a full mutex lock and if so there's nothing more
// to do, which speeds things up in that case.
if ((hops == 0) && ((uintptr_t)path.ptr() != m_bestPath.load(std::memory_order_relaxed))) {
RWMutex::RMaybeWLock l(m_lock);
// If this matches an existing path, skip path learning stuff. For the small number
// of paths a peer will have linear scan is the fastest way to do lookup.
for (unsigned int i = 0; i < m_alivePathCount; ++i) {
if (m_paths[i] == path)
return;
}
// If we made it here, we don't already know this path.
if (ctx.node->filterPotentialPath(cc.tPtr, m_id, path->localSocket(), path->address())) {
// SECURITY: note that if we've made it here we expected this OK, see Expect.hpp.
// There is replay protection in effect for OK responses.
if (verb == Protocol::VERB_OK) {
// Acquire write access to the object and thus path set.
l.writing();
unsigned int newPathIdx;
if (m_alivePathCount == ZT_MAX_PEER_NETWORK_PATHS) {
m_prioritizePaths(cc);
if (m_alivePathCount == ZT_MAX_PEER_NETWORK_PATHS) {
newPathIdx = ZT_MAX_PEER_NETWORK_PATHS - 1;
}
else {
newPathIdx = m_alivePathCount++;
}
}
else {
newPathIdx = m_alivePathCount++;
}
// Save a reference to the current path in case we replace it. This
// should technically never happen, but this ensures safety if it does.
const SharedPtr<Path> currentBest(reinterpret_cast<Path *>(m_bestPath.load(std::memory_order_acquire)));
SharedPtr<Path> old;
old.move(m_paths[newPathIdx]);
m_paths[newPathIdx] = path;
m_prioritizePaths(cc);
ctx.t->learnedNewPath(cc, 0x582fabdd, packetId, m_id, path->address(), (old) ? old->address() : InetAddress());
}
else {
int64_t &lt = m_lastTried[Endpoint(path->address())];
if ((cc.ticks - lt) < ZT_PATH_MIN_TRY_INTERVAL) {
lt = cc.ticks;
path->sent(cc, m_hello(ctx, cc, path->localSocket(), path->address(), false));
ctx.t->tryingNewPath(cc, 0xb7747ddd, m_id, path->address(), path->address(), packetId, (uint8_t)verb, m_id);
}
}
}
}
}
void Peer::send(const Context &ctx, const CallContext &cc, const void *data, unsigned int len) noexcept
{
SharedPtr<Path> via(reinterpret_cast<Path *>(m_bestPath.load(std::memory_order_acquire)));
if (likely(via)) {
if (likely(via->send(ctx, cc, data, len)))
this->sent(cc, len);
}
else {
const SharedPtr<Peer> root(ctx.topology->root());
if (likely((root) && (root.ptr() != this))) {
via = root->path(cc);
if (likely(via)) {
if (likely(via->send(ctx, cc, data, len))) {
root->relayed(cc, len);
this->sent(cc, len);
}
}
}
}
}
void Peer::pulse(const Context &ctx, const CallContext &cc)
{
RWMutex::Lock l(m_lock);
// Grab current key (this is never NULL).
SymmetricKey *const key = reinterpret_cast<SymmetricKey *>(m_key.load(std::memory_order_relaxed));
// Determine if we need a new ephemeral key pair and if a new HELLO needs
// to be sent. The latter happens every ZT_PEER_HELLO_INTERVAL or if a new
// ephemeral key pair is generated.
bool needHello = (((m_vProto >= 20) && (m_keyRenegotiationNeeded || (key == &m_identityKey) || ((cc.ticks - key->timestamp()) >= (ZT_SYMMETRIC_KEY_TTL / 2)) || (key->odometer() > (ZT_SYMMETRIC_KEY_TTL_MESSAGES / 2)))) || ((cc.ticks - m_lastSentHello) >= ZT_PEER_HELLO_INTERVAL));
// Prioritize paths and more importantly for here forget dead ones.
m_prioritizePaths(cc);
if (m_tryQueue.empty()) {
if (m_alivePathCount == 0) {
// If there are no living paths and nothing in the try queue, try addresses
// from any locator we have on file or that are fetched via the external API
// callback (if one was supplied).
if (m_locator) {
for (Vector<std::pair<Endpoint, SharedPtr<const Locator::EndpointAttributes>>>::const_iterator ep(m_locator->endpoints().begin()); ep != m_locator->endpoints().end(); ++ep) {
if (ep->first.type == ZT_ENDPOINT_TYPE_IP_UDP) {
if (ctx.node->filterPotentialPath(cc.tPtr, m_id, -1, ep->first.ip())) {
int64_t &lt = m_lastTried[ep->first];
if ((cc.ticks - lt) > ZT_PATH_MIN_TRY_INTERVAL) {
lt = cc.ticks;
ctx.t->tryingNewPath(cc, 0x84b22322, m_id, ep->first.ip(), InetAddress::NIL, 0, 0, Identity::NIL);
sent(cc, m_sendProbe(ctx, cc, -1, ep->first.ip(), nullptr, 0));
}
}
}
}
}
InetAddress addr;
if (ctx.node->externalPathLookup(cc.tPtr, m_id, -1, addr)) {
if ((addr) && ctx.node->filterPotentialPath(cc.tPtr, m_id, -1, addr)) {
int64_t &lt = m_lastTried[Endpoint(addr)];
if ((cc.ticks - lt) > ZT_PATH_MIN_TRY_INTERVAL) {
lt = cc.ticks;
ctx.t->tryingNewPath(cc, 0x84a10000, m_id, addr, InetAddress::NIL, 0, 0, Identity::NIL);
sent(cc, m_sendProbe(ctx, cc, -1, addr, nullptr, 0));
}
}
}
}
}
else {
unsigned int attempts = 0;
for (;;) {
p_TryQueueItem &qi = m_tryQueue.front();
if (qi.target.isInetAddr()) {
// Skip entry if it overlaps with any currently active IP.
for (unsigned int i = 0; i < m_alivePathCount; ++i) {
if (m_paths[i]->address().ipsEqual(qi.target.ip()))
goto discard_queue_item;
}
}
if (qi.target.type == ZT_ENDPOINT_TYPE_IP_UDP) {
// TODO: need to send something like a NOP for older target nodes.
++attempts;
if (qi.iteration < 0) {
// If iteration is less than zero, try to contact the original address.
// It may be set to a larger negative value to try multiple times such
// as e.g. -3 to try 3 times.
sent(cc, m_sendProbe(ctx, cc, -1, qi.target.ip(), nullptr, 0));
++qi.iteration;
goto requeue_item;
}
else if (qi.target.ip().isV4() && (m_alivePathCount == 0)) {
// When iteration reaches zero the queue item is dropped unless it's
// IPv4 and we have no direct paths. In that case some heavier NAT-t
// strategies are attempted.
if (qi.target.ip().port() < 1024) {
// If the source port is privileged, we actually scan every possible
// privileged port in random order slowly over multiple iterations
// of pulse(). This is done in batches of ZT_NAT_T_PORT_SCAN_MAX.
uint16_t ports[ZT_NAT_T_PORT_SCAN_MAX];
unsigned int pn = 0;
while ((pn < ZT_NAT_T_PORT_SCAN_MAX) && (qi.iteration < 1023)) {
const uint16_t p = ctx.randomPrivilegedPortOrder[qi.iteration++];
if ((unsigned int)p != qi.target.ip().port())
ports[pn++] = p;
}
if (pn > 0)
sent(cc, m_sendProbe(ctx, cc, -1, qi.target.ip(), ports, pn));
if (qi.iteration < 1023)
goto requeue_item;
}
else {
// For un-privileged ports we'll try ZT_NAT_T_PORT_SCAN_MAX ports
// beyond the one we were sent to catch some sequentially assigning
// symmetric NATs.
InetAddress tmp(qi.target.ip());
unsigned int p = tmp.port() + 1 + (unsigned int)qi.iteration++;
if (p > 65535)
p -= 64512; // wrap back to 1024
tmp.setPort(p);
sent(cc, m_sendProbe(ctx, cc, -1, tmp, nullptr, 0));
if (qi.iteration < ZT_NAT_T_PORT_SCAN_MAX)
goto requeue_item;
}
}
}
// Discard front item unless the code skips to requeue_item.
discard_queue_item:
m_tryQueue.pop_front();
if (attempts >= std::min((unsigned int)m_tryQueue.size(), (unsigned int)ZT_NAT_T_PORT_SCAN_MAX))
break;
else
continue;
// If the code skips here the front item is instead moved to the back.
requeue_item:
if (m_tryQueue.size() > 1) // no point in doing this splice if there's only one item
m_tryQueue.splice(m_tryQueue.end(), m_tryQueue, m_tryQueue.begin());
if (attempts >= std::min((unsigned int)m_tryQueue.size(), (unsigned int)ZT_NAT_T_PORT_SCAN_MAX))
break;
else
continue;
}
}
// Do keepalive on all currently active paths, sending HELLO to the first
// if needHello is true and sending small keepalives to others.
for (unsigned int i = 0; i < m_alivePathCount; ++i) {
if (needHello) {
needHello = false;
const unsigned int bytes = m_hello(ctx, cc, m_paths[i]->localSocket(), m_paths[i]->address(), m_keyRenegotiationNeeded);
if (bytes) {
m_paths[i]->sent(cc, bytes);
sent(cc, bytes);
m_lastSentHello = cc.ticks;
m_keyRenegotiationNeeded = false;
}
}
else if ((cc.ticks - m_paths[i]->lastOut()) >= ZT_PATH_KEEPALIVE_PERIOD) {
m_paths[i]->send(ctx, cc, &s_arbitraryByte, 1);
++s_arbitraryByte;
sent(cc, 1);
}
}
// Send a HELLO indirectly if we were not able to send one via any direct path.
if (needHello) {
const SharedPtr<Peer> root(ctx.topology->root());
if (root) {
const SharedPtr<Path> via(root->path(cc));
if (via) {
const unsigned int bytes = m_hello(ctx, cc, via->localSocket(), via->address(), m_keyRenegotiationNeeded);
if (bytes) {
via->sent(cc, bytes);
root->relayed(cc, bytes);
sent(cc, bytes);
m_lastSentHello = cc.ticks;
m_keyRenegotiationNeeded = false;
}
}
}
}
// Clean m_lastTried
for (Map<Endpoint, int64_t>::iterator i(m_lastTried.begin()); i != m_lastTried.end();) {
if ((cc.ticks - i->second) > (ZT_PATH_MIN_TRY_INTERVAL * 3))
m_lastTried.erase(i++);
else
++i;
}
}
void Peer::contact(const Context &ctx, const CallContext &cc, const Endpoint &ep, int tries)
{
RWMutex::Lock l(m_lock);
// See if there's already a path to this endpoint and if so ignore it.
if (ep.isInetAddr()) {
for (unsigned int i = 0; i < m_alivePathCount; ++i) {
if (m_paths[i]->address().ipsEqual(ep.ip()))
return;
}
}
// Check underlying path attempt rate limit.
int64_t &lt = m_lastTried[ep];
if ((cc.ticks - lt) < ZT_PATH_MIN_TRY_INTERVAL)
return;
lt = cc.ticks;
// For IPv4 addresses we send a tiny packet with a low TTL, which helps to
// traverse some NAT types. It has no effect otherwise.
if (ep.isInetAddr() && ep.ip().isV4()) {
ctx.cb.wirePacketSendFunction(reinterpret_cast<ZT_Node *>(ctx.node), ctx.uPtr, cc.tPtr, -1, reinterpret_cast<const ZT_InetAddress *>(&ep.ip()), &s_arbitraryByte, 1, 2);
++s_arbitraryByte;
}
// Make sure address is not already in the try queue. If so just update it.
for (List<p_TryQueueItem>::iterator i(m_tryQueue.begin()); i != m_tryQueue.end(); ++i) {
if (i->target.isSameAddress(ep)) {
i->target = ep;
i->iteration = -tries;
return;
}
}
m_tryQueue.push_back(p_TryQueueItem(ep, -tries));
}
void Peer::resetWithinScope(const Context &ctx, const CallContext &cc, InetAddress::IpScope scope, int inetAddressFamily)
{
RWMutex::Lock l(m_lock);
unsigned int pc = 0;
for (unsigned int i = 0; i < m_alivePathCount; ++i) {
if ((m_paths[i]) && (((int)m_paths[i]->address().as.sa.sa_family == inetAddressFamily) && (m_paths[i]->address().ipScope() == scope))) {
const unsigned int bytes = m_sendProbe(ctx, cc, m_paths[i]->localSocket(), m_paths[i]->address(), nullptr, 0);
m_paths[i]->sent(cc, bytes);
sent(cc, bytes);
}
else if (pc != i) {
m_paths[pc++] = m_paths[i];
}
}
m_alivePathCount = pc;
while (pc < ZT_MAX_PEER_NETWORK_PATHS)
m_paths[pc++].zero();
}
void Peer::save(const Context &ctx, const CallContext &cc) const
{
uint8_t buf[8 + ZT_PEER_MARSHAL_SIZE_MAX];
// Prefix each saved peer with the current timestamp.
Utils::storeBigEndian<uint64_t>(buf, (uint64_t)cc.clock);
const int len = marshal(ctx, buf + 8);
if (len > 0) {
uint64_t id[2];
id[0] = m_id.address().toInt();
id[1] = 0;
ctx.store->put(cc, ZT_STATE_OBJECT_PEER, id, 1, buf, (unsigned int)len + 8);
}
}
int Peer::marshal(const Context &ctx, uint8_t data[ZT_PEER_MARSHAL_SIZE_MAX]) const noexcept
{
RWMutex::RLock l(m_lock);
data[0] = 16; // serialized peer version
// Include our identity's address to detect if this changes and require
// recomputation of m_identityKey.
ctx.identity.address().copyTo(data + 1);
// SECURITY: encryption in place is only to protect secrets if they are
// cached to local storage. It's not used over the wire. Dumb ECB is fine
// because secret keys are random and have no structure to reveal.
ctx.localSecretCipher.encrypt(m_identityKey.key(), data + 1 + ZT_ADDRESS_LENGTH);
ctx.localSecretCipher.encrypt(m_identityKey.key() + 16, data + 1 + ZT_ADDRESS_LENGTH + 16);
ctx.localSecretCipher.encrypt(m_identityKey.key() + 32, data + 1 + ZT_ADDRESS_LENGTH + 32);
int p = 1 + ZT_ADDRESS_LENGTH + 48;
int s = m_id.marshal(data + p, false);
if (s < 0)
return -1;
p += s;
if (m_locator) {
data[p++] = 1;
s = m_locator->marshal(data + p);
if (s <= 0)
return s;
p += s;
}
else {
data[p++] = 0;
}
Utils::storeBigEndian(data + p, (uint16_t)m_vProto);
p += 2;
Utils::storeBigEndian(data + p, (uint16_t)m_vMajor);
p += 2;
Utils::storeBigEndian(data + p, (uint16_t)m_vMinor);
p += 2;
Utils::storeBigEndian(data + p, (uint16_t)m_vRevision);
p += 2;
data[p++] = 0;
data[p++] = 0;
return p;
}
int Peer::unmarshal(const Context &ctx, const int64_t ticks, const uint8_t *restrict data, const int len) noexcept
{
RWMutex::Lock l(m_lock);
if ((len <= (1 + ZT_ADDRESS_LENGTH + 48)) || (data[0] != 16))
return -1;
for (unsigned int i = 0; i < ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE; ++i) {
m_ephemeralKeysSent[i].creationTime = -1;
m_ephemeralSessions[i].established = false;
}
m_key.store((uintptr_t)&m_identityKey, std::memory_order_relaxed);
bool identityKeyRestored = false;
if (Address(data + 1) == ctx.identity.address()) {
uint8_t k[ZT_SYMMETRIC_KEY_SIZE];
static_assert(ZT_SYMMETRIC_KEY_SIZE == 48, "marshal() and unmarshal() must be revisited if ZT_SYMMETRIC_KEY_SIZE is changed");
ctx.localSecretCipher.decrypt(data + 1 + ZT_ADDRESS_LENGTH, k);
ctx.localSecretCipher.decrypt(data + 1 + ZT_ADDRESS_LENGTH + 16, k + 16);
ctx.localSecretCipher.decrypt(data + 1 + ZT_ADDRESS_LENGTH + 32, k + 32);
m_identityKey.init(ticks, k);
Utils::burn(k, sizeof(k));
identityKeyRestored = true;
}
int p = 1 + ZT_ADDRESS_LENGTH + 48;
int s = m_id.unmarshal(data + p, len - p);
if (s < 0)
return s;
p += s;
if (!identityKeyRestored) {
uint8_t k[ZT_SYMMETRIC_KEY_SIZE];
if (!ctx.identity.agree(m_id, k))
return -1;
m_identityKey.init(ticks, k);
Utils::burn(k, sizeof(k));
}
if (p >= len)
return -1;
if (data[p] == 0) {
++p;
m_locator.zero();
}
else if (data[p] == 1) {
++p;
Locator *const loc = new Locator();
s = loc->unmarshal(data + p, len - p);
m_locator.set(loc);
if (s < 0)
return s;
p += s;
}
else {
return -1;
}
if ((p + 10) > len)
return -1;
m_vProto = Utils::loadBigEndian<uint16_t>(data + p);
p += 2;
m_vMajor = Utils::loadBigEndian<uint16_t>(data + p);
p += 2;
m_vMinor = Utils::loadBigEndian<uint16_t>(data + p);
p += 2;
m_vRevision = Utils::loadBigEndian<uint16_t>(data + p);
p += 2;
p += 2 + (int)Utils::loadBigEndian<uint16_t>(data + p);
m_deriveSecondaryIdentityKeys();
return (p > len) ? -1 : p;
}
struct _PathPriorityComparisonOperator {
ZT_INLINE bool operator()(const SharedPtr<Path> &a, const SharedPtr<Path> &b) const noexcept
{
if (a) {
if (b)
return (a->lastIn() > b->lastIn());
else
return true;
}
else {
return false;
}
}
};
void Peer::m_prioritizePaths(const CallContext &cc)
{
// assumes m_lock is locked
// Need to hold the current best just in case we drop it before changing the atomic.
const SharedPtr<Path> oldBest(reinterpret_cast<Path *>(m_bestPath.load(std::memory_order_acquire)));
// Clean and reprioritize paths.
if (m_alivePathCount != 0) {
unsigned int newCnt = 0;
for (unsigned int i = 0; i < m_alivePathCount; ++i) {
if ((m_paths[i]) && (m_paths[i]->alive(cc))) {
if (i != newCnt)
m_paths[newCnt].move(m_paths[i]);
++newCnt;
}
}
for (unsigned int i = newCnt; i < m_alivePathCount; ++i)
m_paths[i].zero();
m_alivePathCount = newCnt;
std::sort(m_paths, m_paths + newCnt, _PathPriorityComparisonOperator());
}
// Update atomic holding pointer to best path.
m_bestPath.store((m_alivePathCount != 0) ? (uintptr_t)m_paths[0].ptr() : (uintptr_t)0, std::memory_order_release);
}
unsigned int Peer::m_sendProbe(const Context &ctx, const CallContext &cc, int64_t localSocket, const InetAddress &atAddress, const uint16_t *ports, const unsigned int numPorts)
{
// Assumes m_lock is locked
// SECURITY: we use the long-lived identity key here since this is used for
// trial contacts, etc. It contains no meaningful payload so who cares if
// some future attacker compromises it.
uint8_t p[ZT_PROTO_MIN_PACKET_LENGTH];
Utils::storeMachineEndian<uint64_t>(p + ZT_PROTO_PACKET_ID_INDEX, m_identityKey.nextMessage(ctx.identity.address(), m_id.address()));
m_id.address().copyTo(p + ZT_PROTO_PACKET_DESTINATION_INDEX);
ctx.identity.address().copyTo(p + ZT_PROTO_PACKET_SOURCE_INDEX);
p[ZT_PROTO_PACKET_FLAGS_INDEX] = 0;
p[ZT_PROTO_PACKET_VERB_INDEX] = Protocol::VERB_NOP;
ctx.expect->sending(Protocol::armor(p, ZT_PROTO_MIN_PACKET_LENGTH, m_identityKey, cipher()), cc.ticks);
if (numPorts > 0) {
InetAddress tmp(atAddress);
for (unsigned int i = 0; i < numPorts; ++i) {
tmp.setPort(ports[i]);
ctx.cb.wirePacketSendFunction(reinterpret_cast<ZT_Node *>(ctx.node), ctx.uPtr, cc.tPtr, -1, reinterpret_cast<const ZT_InetAddress *>(&tmp), p, ZT_PROTO_MIN_PACKET_LENGTH, 0);
}
return ZT_PROTO_MIN_PACKET_LENGTH * numPorts;
}
else {
ctx.cb.wirePacketSendFunction(reinterpret_cast<ZT_Node *>(ctx.node), ctx.uPtr, cc.tPtr, -1, reinterpret_cast<const ZT_InetAddress *>(&atAddress), p, ZT_PROTO_MIN_PACKET_LENGTH, 0);
return ZT_PROTO_MIN_PACKET_LENGTH;
}
}
void Peer::m_deriveSecondaryIdentityKeys() noexcept
{
// This is called in init() and unmarshal() to use KBKDF to derive keys
// for encrypting the dictionary portion of HELLOs and HELLO HMAC from the
// primary long-lived identity key.
uint8_t hk[ZT_SYMMETRIC_KEY_SIZE];
KBKDFHMACSHA384(m_identityKey.key(), ZT_KBKDF_LABEL_HELLO_DICTIONARY_ENCRYPT, 0, 0, hk);
m_helloCipher.init(hk);
Utils::burn(hk, sizeof(hk));
KBKDFHMACSHA384(m_identityKey.key(), ZT_KBKDF_LABEL_PACKET_HMAC, 0, 0, m_helloMacKey);
}
unsigned int Peer::m_hello(const Context &ctx, const CallContext &cc, int64_t localSocket, const InetAddress &atAddress, const bool forceNewKey)
{
// assumes m_lock is at least locked for reading
/* SECURITY: note that HELLO is sent mostly in the clear and always uses
* the long-lived identity key. This allows us to always bootstrap regardless
* of ephemeral key state. HELLO contains nothing particularly sensitive,
* though part of the message is encrypted with another derived key just to
* conceal things like ephemeral public keys for defense in depth. HELLO is
* always sent with the old salsa/poly algorithm (but minus salsa of course
* as it's plaintext), but terminates with an additional HMAC-SHA3
* authenticator to add extra hardness to the key exchange. The use of HMAC
* here is also needed to satisfy some FIPS/NIST type requirements. */
// Pick or generate an ephemeral key to send with this HELLO.
p_EphemeralPrivate *ephemeral;
{
p_EphemeralPrivate *earliest = m_ephemeralKeysSent;
p_EphemeralPrivate *latest = nullptr;
int64_t earliestEphemeralPrivate = 9223372036854775807LL;
int64_t latestEphemeralPrivate = 0;
for (unsigned int k = 0; k < ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE; ++k) {
const int64_t ct = m_ephemeralKeysSent[k].creationTime;
if (ct <= earliestEphemeralPrivate) {
earliestEphemeralPrivate = ct;
earliest = m_ephemeralKeysSent + k;
}
else if (ct >= latestEphemeralPrivate) { // creationTime will be -1 if not initialized
latestEphemeralPrivate = ct;
latest = m_ephemeralKeysSent + k;
}
}
if ((latest != nullptr) && (!forceNewKey) && ((cc.ticks - latest->creationTime) < (ZT_SYMMETRIC_KEY_TTL / 2))) {
ephemeral = latest;
}
else {
earliest->creationTime = cc.ticks;
earliest->pub.type = ZT_PROTO_EPHEMERAL_KEY_TYPE_C25519_P384;
C25519::generateC25519(earliest->pub.c25519Public, earliest->c25519Private);
ECC384GenerateKey(earliest->pub.p384Public, earliest->p384Private);
SHA384(earliest->sha384OfPublic, &earliest->pub, sizeof(earliest->pub));
ephemeral = earliest;
}
}
// Initialize packet and add basic fields like identity and sent-to address.
Buf outp;
const uint64_t packetId = m_identityKey.nextMessage(ctx.identity.address(), m_id.address());
int ii = Protocol::newPacket(outp, packetId, m_id.address(), ctx.identity.address(), Protocol::VERB_HELLO);
outp.wI8(ii, ZT_PROTO_VERSION);
outp.wI8(ii, ZEROTIER_VERSION_MAJOR);
outp.wI8(ii, ZEROTIER_VERSION_MINOR);
outp.wI16(ii, ZEROTIER_VERSION_REVISION);
outp.wI64(ii, (uint64_t)cc.clock);
outp.wO(ii, ctx.identity);
outp.wO(ii, atAddress);
// Add 12 random bytes to act as an IV for the encrypted dictionary field.
const int ivStart = ii;
outp.wR(ii, 12);
// LEGACY: the six reserved bytes after the IV exist for legacy compatibility with v1.x nodes.
// Once those are dead they'll become just reserved bytes for future use as flags etc.
outp.wI32(ii, 0); // reserved bytes
void *const legacyMoonCountStart = outp.unsafeData + ii;
outp.wI16(ii, 0);
const uint64_t legacySalsaIv = packetId & ZT_CONST_TO_BE_UINT64(0xfffffffffffffff8ULL);
Salsa20(m_identityKey.key(), &legacySalsaIv).crypt12(legacyMoonCountStart, legacyMoonCountStart, 2);
// Append dictionary containinig meta-data and ephemeral key info.
const int cryptSectionStart = ii;
FCV<uint8_t, 2048> md;
Dictionary::append(md, ZT_PROTO_HELLO_NODE_META_INSTANCE_ID, ctx.instanceId);
// TODO: add other fields and ephemeral key info
outp.wI16(ii, (uint16_t)md.size());
outp.wB(ii, md.data(), (unsigned int)md.size());
if (unlikely((ii + ZT_HMACSHA384_LEN) > ZT_BUF_SIZE)) // sanity check, should be impossible
return 0;
// Encrypt the meta-data dictionary using a derived static key and the IV
// we generated above. This isn't strictly necessary as the data in there is
// not "secret," but it's not a bad idea to hide it for defense in depth. In
// particular this means that the public keys exchanged for ephemeral keying
// are concealed from any observer.
AES::CTR ctr(m_helloCipher);
void *const cryptSection = outp.unsafeData + ii;
ctr.init(outp.unsafeData + ivStart, 0, cryptSection);
ctr.crypt(cryptSection, ii - cryptSectionStart);
ctr.finish();
// Add HMAC at the end for strong verification by v2 nodes.
HMACSHA384(m_helloMacKey, outp.unsafeData, ii, outp.unsafeData + ii);
ii += ZT_HMACSHA384_LEN;
// Add poly1305 MAC for v1 nodes.
uint8_t polyKey[ZT_POLY1305_KEY_SIZE], perPacketKey[ZT_SALSA20_KEY_SIZE];
Protocol::salsa2012DeriveKey(m_identityKey.key(), perPacketKey, outp, ii);
Salsa20(perPacketKey, &packetId).crypt12(Utils::ZERO256, polyKey, sizeof(polyKey));
Poly1305 p1305(polyKey);
p1305.update(outp.unsafeData + ZT_PROTO_PACKET_ENCRYPTED_SECTION_START, ii - ZT_PROTO_PACKET_ENCRYPTED_SECTION_START);
uint64_t polyMac[2];
p1305.finish(polyMac);
Utils::storeMachineEndian<uint64_t>(outp.unsafeData + ZT_PROTO_PACKET_MAC_INDEX, polyMac[0]);
return (likely(ctx.cb.wirePacketSendFunction(reinterpret_cast<ZT_Node *>(ctx.node), ctx.uPtr, cc.tPtr, localSocket, reinterpret_cast<const ZT_InetAddress *>(&atAddress), outp.unsafeData, ii, 0) == 0)) ? (unsigned int)ii : 0U;
}
} // namespace ZeroTier
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