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broke zssp into files

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mamoniot 2022-12-14 11:47:31 -05:00
parent f8ed545f32
commit 1cbe9a57dc
6 changed files with 612 additions and 575 deletions
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72
zssp/src/app_layer.rs Normal file
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use std::ops::Deref;
use zerotier_crypto::{p384::{P384KeyPair, P384PublicKey}, secret::Secret};
use crate::{zssp::{Session, ReceiveContext}, ints::SessionId};
/// Trait to implement to integrate the session into an application.
///
/// Templating the session on this trait lets the code here be almost entirely transport, OS,
/// and use case independent.
pub trait ApplicationLayer: Sized {
/// Arbitrary opaque object associated with a session, such as a connection state object.
type SessionUserData;
/// Arbitrary object that dereferences to the session, such as Arc<Session<Self>>.
type SessionRef: Deref<Target = Session<Self>>;
/// A buffer containing data read from the network that can be cached.
///
/// This can be e.g. a pooled buffer that automatically returns itself to the pool when dropped.
/// It can also just be a Vec<u8> or Box<[u8]> or something like that.
type IncomingPacketBuffer: AsRef<[u8]>;
/// Remote physical address on whatever transport this session is using.
type RemoteAddress;
/// Rate limit for attempts to rekey existing sessions in milliseconds (default: 2000).
const REKEY_RATE_LIMIT_MS: i64 = 2000;
/// Get a reference to this host's static public key blob.
///
/// This must contain a NIST P-384 public key but can contain other information. In ZeroTier this
/// is a byte serialized identity. It could just be a naked NIST P-384 key if that's all you need.
fn get_local_s_public_raw(&self) -> &[u8];
/// Get SHA384(this host's static public key blob).
///
/// This allows us to avoid computing SHA384(public key blob) over and over again.
fn get_local_s_public_hash(&self) -> &[u8; 48];
/// Get a reference to this hosts' static public key's NIST P-384 secret key pair.
///
/// This must return the NIST P-384 public key that is contained within the static public key blob.
fn get_local_s_keypair(&self) -> &P384KeyPair;
/// Extract the NIST P-384 ECC public key component from a static public key blob or return None on failure.
///
/// This is called to parse the static public key blob from the other end and extract its NIST P-384 public
/// key. SECURITY NOTE: the information supplied here is from the wire so care must be taken to parse it
/// safely and fail on any error or corruption.
fn extract_s_public_from_raw(static_public: &[u8]) -> Option<P384PublicKey>;
/// Look up a local session by local session ID or return None if not found.
fn lookup_session(&self, local_session_id: SessionId) -> Option<Self::SessionRef>;
/// Rate limit and check an attempted new session (called before accept_new_session).
fn check_new_session(&self, rc: &ReceiveContext<Self>, remote_address: &Self::RemoteAddress) -> bool;
/// Check whether a new session should be accepted.
///
/// On success a tuple of local session ID, static secret, and associated object is returned. The
/// static secret is whatever results from agreement between the local and remote static public
/// keys.
fn accept_new_session(
&self,
receive_context: &ReceiveContext<Self>,
remote_address: &Self::RemoteAddress,
remote_static_public: &[u8],
remote_metadata: &[u8],
) -> Option<(SessionId, Secret<64>, Self::SessionUserData)>;
}

108
zssp/src/constants.rs Normal file
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/// Minimum size of a valid physical ZSSP packet or packet fragment.
pub const MIN_PACKET_SIZE: usize = HEADER_SIZE + AES_GCM_TAG_SIZE;
/// Minimum physical MTU for ZSSP to function.
pub const MIN_TRANSPORT_MTU: usize = 1280;
/// Minimum recommended interval between calls to service() on each session, in milliseconds.
pub const SERVICE_INTERVAL: u64 = 10000;
/// Setting this to true enables kyber1024 post-quantum forward secrecy.
///
/// Kyber1024 is used for data forward secrecy but not authentication. Authentication would
/// require Kyber1024 in identities, which would make them huge, and isn't needed for our
/// threat model which is data warehousing today to decrypt tomorrow. Breaking authentication
/// is only relevant today, not in some mid to far future where a QC that can break 384-bit ECC
/// exists.
///
/// This is normally enabled but could be disabled at build time for e.g. very small devices.
/// It might not even be necessary there to disable it since it's not that big and is usually
/// faster than NIST P-384 ECDH.
pub(crate) const JEDI: bool = true;
/// Maximum number of fragments for data packets.
pub(crate) const MAX_FRAGMENTS: usize = 48; // hard protocol max: 63
/// Maximum number of fragments for key exchange packets (can be smaller to save memory, only a few needed)
pub(crate) const KEY_EXCHANGE_MAX_FRAGMENTS: usize = 2; // enough room for p384 + ZT identity + kyber1024 + tag/hmac/etc.
/// Start attempting to rekey after a key has been used to send packets this many times.
///
/// This is 1/4 the NIST recommended maximum and 1/8 the absolute limit where u32 wraps.
/// As such it should leave plenty of margin against nearing key reuse bounds w/AES-GCM.
pub(crate) const REKEY_AFTER_USES: u64 = 536870912;
/// Maximum random jitter to add to rekey-after usage count.
pub(crate) const REKEY_AFTER_USES_MAX_JITTER: u32 = 1048576;
/// Hard expiration after this many uses.
///
/// Use of the key beyond this point is prohibited. If we reach this number of key uses
/// the key will be destroyed in memory and the session will cease to function. A hard
/// error is also generated.
pub(crate) const EXPIRE_AFTER_USES: u64 = (u32::MAX - 1024) as u64;
/// Start attempting to rekey after a key has been in use for this many milliseconds.
pub(crate) const REKEY_AFTER_TIME_MS: i64 = 1000 * 60 * 60; // 1 hour
/// Maximum random jitter to add to rekey-after time.
pub(crate) const REKEY_AFTER_TIME_MS_MAX_JITTER: u32 = 1000 * 60 * 10; // 10 minutes
/// Version 0: AES-256-GCM + NIST P-384 + optional Kyber1024 PQ forward secrecy
pub(crate) const SESSION_PROTOCOL_VERSION: u8 = 0x00;
/// Secondary key type: none, use only P-384 for forward secrecy.
pub(crate) const E1_TYPE_NONE: u8 = 0;
/// Secondary key type: Kyber1024, PQ forward secrecy enabled.
pub(crate) const E1_TYPE_KYBER1024: u8 = 1;
/// Size of packet header
pub(crate) const HEADER_SIZE: usize = 16;
/// Size of AES-GCM keys (256 bits)
pub(crate) const AES_KEY_SIZE: usize = 32;
/// Size of AES-GCM MAC tags
pub(crate) const AES_GCM_TAG_SIZE: usize = 16;
/// Size of HMAC-SHA384 MAC tags
pub(crate) const HMAC_SIZE: usize = 48;
/// Size of a session ID, which behaves a bit like a TCP port number.
///
/// This is large since some ZeroTier nodes handle huge numbers of links, like roots and controllers.
pub(crate) const SESSION_ID_SIZE: usize = 6;
/// Number of session keys to hold at a given time (current, previous, next).
pub(crate) const KEY_HISTORY_SIZE: usize = 3;
// Packet types can range from 0 to 15 (4 bits) -- 0-3 are defined and 4-15 are reserved for future use
pub(crate) const PACKET_TYPE_DATA: u8 = 0;
pub(crate) const PACKET_TYPE_NOP: u8 = 1;
pub(crate) const PACKET_TYPE_KEY_OFFER: u8 = 2; // "alice"
pub(crate) const PACKET_TYPE_KEY_COUNTER_OFFER: u8 = 3; // "bob"
// Key usage labels for sub-key derivation using NIST-style KBKDF (basically just HMAC KDF).
pub(crate) const KBKDF_KEY_USAGE_LABEL_HMAC: u8 = b'M'; // HMAC-SHA384 authentication for key exchanges
pub(crate) const KBKDF_KEY_USAGE_LABEL_HEADER_CHECK: u8 = b'H'; // AES-based header check code generation
pub(crate) const KBKDF_KEY_USAGE_LABEL_AES_GCM_ALICE_TO_BOB: u8 = b'A'; // AES-GCM in A->B direction
pub(crate) const KBKDF_KEY_USAGE_LABEL_AES_GCM_BOB_TO_ALICE: u8 = b'B'; // AES-GCM in B->A direction
pub(crate) const KBKDF_KEY_USAGE_LABEL_RATCHETING: u8 = b'R'; // Key input for next ephemeral ratcheting
// AES key size for header check code generation
pub(crate) const HEADER_CHECK_AES_KEY_SIZE: usize = 16;
/// Aribitrary starting value for master key derivation.
///
/// It doesn't matter very much what this is but it's good for it to be unique. It should
/// be changed if this code is changed in any cryptographically meaningful way like changing
/// the primary algorithm from NIST P-384 or the transport cipher from AES-GCM.
pub(crate) const INITIAL_KEY: [u8; 64] = [
// macOS command line to generate:
// echo -n 'ZSSP_Noise_IKpsk2_NISTP384_?KYBER1024_AESGCM_SHA512' | shasum -a 512 | cut -d ' ' -f 1 | xxd -r -p | xxd -i
0x35, 0x6a, 0x75, 0xc0, 0xbf, 0xbe, 0xc3, 0x59, 0x70, 0x94, 0x50, 0x69, 0x4c, 0xa2, 0x08, 0x40, 0xc7, 0xdf, 0x67, 0xa8, 0x68, 0x52,
0x6e, 0xd5, 0xdd, 0x77, 0xec, 0x59, 0x6f, 0x8e, 0xa1, 0x99, 0xb4, 0x32, 0x85, 0xaf, 0x7f, 0x0d, 0xa9, 0x6c, 0x01, 0xfb, 0x72, 0x46,
0xc0, 0x09, 0x58, 0xb8, 0xe0, 0xa8, 0xcf, 0xb1, 0x58, 0x04, 0x6e, 0x32, 0xba, 0xa8, 0xb8, 0xf9, 0x0a, 0xa4, 0xbf, 0x36,
];

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zssp/src/ints.rs Normal file
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use std::{io::Read, sync::atomic::{AtomicU64, Ordering}};
use zerotier_crypto::random;
use zerotier_utils::memory;
use crate::constants::*;
/// "Canonical header" for generating 96-bit AES-GCM nonce and for inclusion in HMACs.
///
/// This is basically the actual header but with fragment count and fragment total set to zero.
/// Fragmentation is not considered when authenticating the entire packet. A separate header
/// check code is used to make fragmentation itself more robust, but that's outside the scope
/// of AEAD authentication.
#[derive(Clone, Copy)]
#[repr(C, packed)]
pub(crate) struct CanonicalHeader(pub u64, pub u32);
impl CanonicalHeader {
#[inline(always)]
pub fn make(session_id: SessionId, packet_type: u8, counter: u32) -> Self {
CanonicalHeader(
(u64::from(session_id) | (packet_type as u64).wrapping_shl(48)).to_le(),
counter.to_le(),
)
}
#[inline(always)]
pub fn as_bytes(&self) -> &[u8; 12] {
memory::as_byte_array(self)
}
}
/// 48-bit session ID (most significant 16 bits of u64 are unused)
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
#[repr(transparent)]
pub struct SessionId(pub(crate) u64);
impl SessionId {
/// The nil session ID used in messages initiating a new session.
///
/// This is all 1's so that ZeroTier can easily tell the difference between ZSSP init packets
/// and ZeroTier V1 packets.
pub const NIL: SessionId = SessionId(0xffffffffffff);
#[inline]
pub fn new_from_u64(i: u64) -> Option<SessionId> {
if i < Self::NIL.0 {
Some(Self(i))
} else {
None
}
}
#[inline]
pub fn new_from_reader<R: Read>(r: &mut R) -> std::io::Result<Option<SessionId>> {
let mut tmp = 0_u64.to_ne_bytes();
r.read_exact(&mut tmp[..SESSION_ID_SIZE])?;
Ok(Self::new_from_u64(u64::from_le_bytes(tmp)))
}
#[inline]
pub fn new_random() -> Self {
Self(random::next_u64_secure() % Self::NIL.0)
}
}
impl From<SessionId> for u64 {
#[inline(always)]
fn from(sid: SessionId) -> Self {
sid.0
}
}
/// Outgoing packet counter with strictly ordered atomic semantics.
#[repr(transparent)]
pub(crate) struct Counter(AtomicU64);
impl Counter {
#[inline(always)]
pub fn new() -> Self {
// Using a random value has no security implication. Zero would be fine. This just
// helps randomize packet contents a bit.
Self(AtomicU64::new(random::next_u32_secure() as u64))
}
/// Get the value most recently used to send a packet.
#[inline(always)]
pub fn previous(&self) -> CounterValue {
CounterValue(self.0.load(Ordering::SeqCst))
}
/// Get a counter value for the next packet being sent.
#[inline(always)]
pub fn next(&self) -> CounterValue {
CounterValue(self.0.fetch_add(1, Ordering::SeqCst))
}
}
/// A value of the outgoing packet counter.
///
/// The used portion of the packet counter is the least significant 32 bits, but the internal
/// counter state is kept as a 64-bit integer. This makes it easier to correctly handle
/// key expiration after usage limits are reached without complicated logic to handle 32-bit
/// wrapping. Usage limits are below 2^32 so the actual 32-bit counter will not wrap for a
/// given shared secret key.
#[repr(transparent)]
#[derive(Copy, Clone)]
pub(crate) struct CounterValue(pub u64);
impl CounterValue {
#[inline(always)]
pub fn to_u32(&self) -> u32 {
self.0 as u32
}
}
/// Was this side the one who sent the first offer (Alice) or countered (Bob).
/// Note that role is not fixed. Either side can take either role. It's just who
/// initiated first.
pub enum Role {
Alice,
Bob,
}

3
zssp/src/lib.rs
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@ -1,2 +1,5 @@
pub mod constants;
pub mod zssp;
pub mod app_layer;
pub mod ints;

221
zssp/src/tests.rs Normal file
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@ -0,0 +1,221 @@
#[cfg(test)]
mod tests {
use std::collections::LinkedList;
use std::sync::{Arc, Mutex};
use zerotier_utils::hex;
#[allow(unused_imports)]
use super::*;
struct TestHost {
local_s: P384KeyPair,
local_s_hash: [u8; 48],
psk: Secret<64>,
session: Mutex<Option<Arc<Session<Box<TestHost>>>>>,
session_id_counter: Mutex<u64>,
queue: Mutex<LinkedList<Vec<u8>>>,
key_id: Mutex<[u8; 16]>,
this_name: &'static str,
other_name: &'static str,
}
impl TestHost {
fn new(psk: Secret<64>, this_name: &'static str, other_name: &'static str) -> Self {
let local_s = P384KeyPair::generate();
let local_s_hash = SHA384::hash(local_s.public_key_bytes());
Self {
local_s,
local_s_hash,
psk,
session: Mutex::new(None),
session_id_counter: Mutex::new(1),
queue: Mutex::new(LinkedList::new()),
key_id: Mutex::new([0; 16]),
this_name,
other_name,
}
}
}
impl ApplicationLayer for Box<TestHost> {
type SessionUserData = u32;
type SessionRef = Arc<Session<Box<TestHost>>>;
type IncomingPacketBuffer = Vec<u8>;
type RemoteAddress = u32;
const REKEY_RATE_LIMIT_MS: i64 = 0;
fn get_local_s_public_raw(&self) -> &[u8] {
self.local_s.public_key_bytes()
}
fn get_local_s_public_hash(&self) -> &[u8; 48] {
&self.local_s_hash
}
fn get_local_s_keypair(&self) -> &P384KeyPair {
&self.local_s
}
fn extract_s_public_from_raw(static_public: &[u8]) -> Option<P384PublicKey> {
P384PublicKey::from_bytes(static_public)
}
fn lookup_session(&self, local_session_id: SessionId) -> Option<Self::SessionRef> {
self.session.lock().unwrap().as_ref().and_then(|s| {
if s.id == local_session_id {
Some(s.clone())
} else {
None
}
})
}
fn check_new_session(&self, _: &ReceiveContext<Self>, _: &Self::RemoteAddress) -> bool {
true
}
fn accept_new_session(
&self,
_: &ReceiveContext<Self>,
_: &u32,
_: &[u8],
_: &[u8],
) -> Option<(SessionId, Secret<64>, Self::SessionUserData)> {
loop {
let mut new_id = self.session_id_counter.lock().unwrap();
*new_id += 1;
return Some((SessionId::new_from_u64(*new_id).unwrap(), self.psk.clone(), 0));
}
}
}
#[allow(unused_variables)]
#[test]
fn establish_session() {
let mut data_buf = [0_u8; (1280 - 32) * MAX_FRAGMENTS];
let mut mtu_buffer = [0_u8; 1280];
let mut psk: Secret<64> = Secret::default();
random::fill_bytes_secure(&mut psk.0);
let alice_host = Box::new(TestHost::new(psk.clone(), "alice", "bob"));
let bob_host = Box::new(TestHost::new(psk.clone(), "bob", "alice"));
let alice_rc: Box<ReceiveContext<Box<TestHost>>> = Box::new(ReceiveContext::new(&alice_host));
let bob_rc: Box<ReceiveContext<Box<TestHost>>> = Box::new(ReceiveContext::new(&bob_host));
//println!("zssp: size of session (bytes): {}", std::mem::size_of::<Session<Box<TestHost>>>());
let _ = alice_host.session.lock().unwrap().insert(Arc::new(
Session::start_new(
&alice_host,
|data| bob_host.queue.lock().unwrap().push_front(data.to_vec()),
SessionId::new_random(),
bob_host.local_s.public_key_bytes(),
&[],
&psk,
1,
mtu_buffer.len(),
1,
)
.unwrap(),
));
let mut ts = 0;
for test_loop in 0..256 {
for host in [&alice_host, &bob_host] {
let send_to_other = |data: &mut [u8]| {
if std::ptr::eq(host, &alice_host) {
bob_host.queue.lock().unwrap().push_front(data.to_vec());
} else {
alice_host.queue.lock().unwrap().push_front(data.to_vec());
}
};
let rc = if std::ptr::eq(host, &alice_host) {
&alice_rc
} else {
&bob_rc
};
loop {
if let Some(qi) = host.queue.lock().unwrap().pop_back() {
let qi_len = qi.len();
ts += 1;
let r = rc.receive(host, &0, send_to_other, &mut data_buf, qi, mtu_buffer.len(), ts);
if r.is_ok() {
let r = r.unwrap();
match r {
ReceiveResult::Ok => {
//println!("zssp: {} => {} ({}): Ok", host.other_name, host.this_name, qi_len);
}
ReceiveResult::OkData(data) => {
//println!("zssp: {} => {} ({}): OkData length=={}", host.other_name, host.this_name, qi_len, data.len());
assert!(!data.iter().any(|x| *x != 0x12));
}
ReceiveResult::OkNewSession(new_session) => {
println!(
"zssp: {} => {} ({}): OkNewSession ({})",
host.other_name,
host.this_name,
qi_len,
u64::from(new_session.id)
);
let mut hs = host.session.lock().unwrap();
assert!(hs.is_none());
let _ = hs.insert(Arc::new(new_session));
}
ReceiveResult::Ignored => {
println!("zssp: {} => {} ({}): Ignored", host.other_name, host.this_name, qi_len);
}
}
} else {
println!(
"zssp: {} => {} ({}): error: {}",
host.other_name,
host.this_name,
qi_len,
r.err().unwrap().to_string()
);
panic!();
}
} else {
break;
}
}
data_buf.fill(0x12);
if let Some(session) = host.session.lock().unwrap().as_ref().cloned() {
if session.established() {
{
let mut key_id = host.key_id.lock().unwrap();
let security_info = session.status().unwrap();
if !security_info.0.eq(key_id.as_ref()) {
*key_id = security_info.0;
println!(
"zssp: new key at {}: fingerprint {} ratchet {} kyber {}",
host.this_name,
hex::to_string(key_id.as_ref()),
security_info.2,
security_info.3
);
}
}
for _ in 0..4 {
assert!(session
.send(
send_to_other,
&mut mtu_buffer,
&data_buf[..((random::xorshift64_random() as usize) % data_buf.len())]
)
.is_ok());
}
if (test_loop % 8) == 0 && test_loop >= 8 && host.this_name.eq("alice") {
session.service(host, send_to_other, &[], mtu_buffer.len(), test_loop as i64, true);
}
}
}
}
}
}
}

655
zssp/src/zssp.rs
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@ -4,8 +4,6 @@
// FIPS compliant Noise_IK with Jedi powers and built-in attack-resistant large payload (fragmentation) support.
use std::io::{Read, Write};
use std::ops::Deref;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::{Mutex, RwLock};
use zerotier_crypto::aes::{Aes, AesGcm};
@ -20,113 +18,14 @@ use zerotier_utils::ringbuffermap::RingBufferMap;
use zerotier_utils::unlikely_branch;
use zerotier_utils::varint;
/// Minimum size of a valid physical ZSSP packet or packet fragment.
pub const MIN_PACKET_SIZE: usize = HEADER_SIZE + AES_GCM_TAG_SIZE;
use crate::app_layer::ApplicationLayer;
use crate::ints::*;
use crate::constants::*;
/// Minimum physical MTU for ZSSP to function.
pub const MIN_TRANSPORT_MTU: usize = 1280;
/// Minimum recommended interval between calls to service() on each session, in milliseconds.
pub const SERVICE_INTERVAL: u64 = 10000;
/// Setting this to true enables kyber1024 post-quantum forward secrecy.
///
/// Kyber1024 is used for data forward secrecy but not authentication. Authentication would
/// require Kyber1024 in identities, which would make them huge, and isn't needed for our
/// threat model which is data warehousing today to decrypt tomorrow. Breaking authentication
/// is only relevant today, not in some mid to far future where a QC that can break 384-bit ECC
/// exists.
///
/// This is normally enabled but could be disabled at build time for e.g. very small devices.
/// It might not even be necessary there to disable it since it's not that big and is usually
/// faster than NIST P-384 ECDH.
const JEDI: bool = true;
/// Maximum number of fragments for data packets.
const MAX_FRAGMENTS: usize = 48; // hard protocol max: 63
/// Maximum number of fragments for key exchange packets (can be smaller to save memory, only a few needed)
const KEY_EXCHANGE_MAX_FRAGMENTS: usize = 2; // enough room for p384 + ZT identity + kyber1024 + tag/hmac/etc.
/// Start attempting to rekey after a key has been used to send packets this many times.
///
/// This is 1/4 the NIST recommended maximum and 1/8 the absolute limit where u32 wraps.
/// As such it should leave plenty of margin against nearing key reuse bounds w/AES-GCM.
const REKEY_AFTER_USES: u64 = 536870912;
/// Maximum random jitter to add to rekey-after usage count.
const REKEY_AFTER_USES_MAX_JITTER: u32 = 1048576;
/// Hard expiration after this many uses.
///
/// Use of the key beyond this point is prohibited. If we reach this number of key uses
/// the key will be destroyed in memory and the session will cease to function. A hard
/// error is also generated.
const EXPIRE_AFTER_USES: u64 = (u32::MAX - 1024) as u64;
/// Start attempting to rekey after a key has been in use for this many milliseconds.
const REKEY_AFTER_TIME_MS: i64 = 1000 * 60 * 60; // 1 hour
/// Maximum random jitter to add to rekey-after time.
const REKEY_AFTER_TIME_MS_MAX_JITTER: u32 = 1000 * 60 * 10; // 10 minutes
/// Version 0: AES-256-GCM + NIST P-384 + optional Kyber1024 PQ forward secrecy
const SESSION_PROTOCOL_VERSION: u8 = 0x00;
/// Secondary key type: none, use only P-384 for forward secrecy.
const E1_TYPE_NONE: u8 = 0;
/// Secondary key type: Kyber1024, PQ forward secrecy enabled.
const E1_TYPE_KYBER1024: u8 = 1;
/// Size of packet header
const HEADER_SIZE: usize = 16;
/// Size of AES-GCM keys (256 bits)
const AES_KEY_SIZE: usize = 32;
/// Size of AES-GCM MAC tags
const AES_GCM_TAG_SIZE: usize = 16;
/// Size of HMAC-SHA384 MAC tags
const HMAC_SIZE: usize = 48;
/// Size of a session ID, which behaves a bit like a TCP port number.
///
/// This is large since some ZeroTier nodes handle huge numbers of links, like roots and controllers.
const SESSION_ID_SIZE: usize = 6;
/// Number of session keys to hold at a given time (current, previous, next).
const KEY_HISTORY_SIZE: usize = 3;
// Packet types can range from 0 to 15 (4 bits) -- 0-3 are defined and 4-15 are reserved for future use
const PACKET_TYPE_DATA: u8 = 0;
const PACKET_TYPE_NOP: u8 = 1;
const PACKET_TYPE_KEY_OFFER: u8 = 2; // "alice"
const PACKET_TYPE_KEY_COUNTER_OFFER: u8 = 3; // "bob"
// Key usage labels for sub-key derivation using NIST-style KBKDF (basically just HMAC KDF).
const KBKDF_KEY_USAGE_LABEL_HMAC: u8 = b'M'; // HMAC-SHA384 authentication for key exchanges
const KBKDF_KEY_USAGE_LABEL_HEADER_CHECK: u8 = b'H'; // AES-based header check code generation
const KBKDF_KEY_USAGE_LABEL_AES_GCM_ALICE_TO_BOB: u8 = b'A'; // AES-GCM in A->B direction
const KBKDF_KEY_USAGE_LABEL_AES_GCM_BOB_TO_ALICE: u8 = b'B'; // AES-GCM in B->A direction
const KBKDF_KEY_USAGE_LABEL_RATCHETING: u8 = b'R'; // Key input for next ephemeral ratcheting
// AES key size for header check code generation
const HEADER_CHECK_AES_KEY_SIZE: usize = 16;
/// Aribitrary starting value for master key derivation.
///
/// It doesn't matter very much what this is but it's good for it to be unique. It should
/// be changed if this code is changed in any cryptographically meaningful way like changing
/// the primary algorithm from NIST P-384 or the transport cipher from AES-GCM.
const INITIAL_KEY: [u8; 64] = [
// macOS command line to generate:
// echo -n 'ZSSP_Noise_IKpsk2_NISTP384_?KYBER1024_AESGCM_SHA512' | shasum -a 512 | cut -d ' ' -f 1 | xxd -r -p | xxd -i
0x35, 0x6a, 0x75, 0xc0, 0xbf, 0xbe, 0xc3, 0x59, 0x70, 0x94, 0x50, 0x69, 0x4c, 0xa2, 0x08, 0x40, 0xc7, 0xdf, 0x67, 0xa8, 0x68, 0x52,
0x6e, 0xd5, 0xdd, 0x77, 0xec, 0x59, 0x6f, 0x8e, 0xa1, 0x99, 0xb4, 0x32, 0x85, 0xaf, 0x7f, 0x0d, 0xa9, 0x6c, 0x01, 0xfb, 0x72, 0x46,
0xc0, 0x09, 0x58, 0xb8, 0xe0, 0xa8, 0xcf, 0xb1, 0x58, 0x04, 0x6e, 0x32, 0xba, 0xa8, 0xb8, 0xf9, 0x0a, 0xa4, 0xbf, 0x36,
];
////////////////////////////////////////////////////////////////
// types
////////////////////////////////////////////////////////////////
pub enum Error {
/// The packet was addressed to an unrecognized local session (should usually be ignored)
@ -166,6 +65,80 @@ pub enum Error {
UnexpectedIoError(std::io::Error),
}
/// Result generated by the packet receive function, with possible payloads.
pub enum ReceiveResult<'a, H: ApplicationLayer> {
/// Packet is valid, no action needs to be taken.
Ok,
/// Packet is valid and a data payload was decoded and authenticated.
///
/// The returned reference is to the filled parts of the data buffer supplied to receive.
OkData(&'a mut [u8]),
/// Packet is valid and a new session was created.
///
/// The session will have already been gated by the accept_new_session() method in the Host trait.
OkNewSession(Session<H>),
/// Packet appears valid but was ignored e.g. as a duplicate.
Ignored,
}
/// State information to associate with receiving contexts such as sockets or remote paths/endpoints.
///
/// This holds the data structures used to defragment incoming packets that are not associated with an
/// existing session, which would be new attempts to create sessions. Typically one of these is associated
/// with a single listen socket, local bound port, or other inbound endpoint.
pub struct ReceiveContext<H: ApplicationLayer> {
initial_offer_defrag: Mutex<RingBufferMap<u32, GatherArray<H::IncomingPacketBuffer, KEY_EXCHANGE_MAX_FRAGMENTS>, 1024, 128>>,
incoming_init_header_check_cipher: Aes,
}
/// ZSSP bi-directional packet transport channel.
pub struct Session<Layer: ApplicationLayer> {
/// This side's session ID (unique on this side)
pub id: SessionId,
/// An arbitrary object associated with session (type defined in Host trait)
pub user_data: Layer::SessionUserData,
send_counter: Counter, // Outgoing packet counter and nonce state
psk: Secret<64>, // Arbitrary PSK provided by external code
noise_ss: Secret<48>, // Static raw shared ECDH NIST P-384 key
header_check_cipher: Aes, // Cipher used for header MAC (fragmentation)
state: RwLock<SessionMutableState>, // Mutable parts of state (other than defrag buffers)
remote_s_public_hash: [u8; 48], // SHA384(remote static public key blob)
remote_s_public_raw: [u8; P384_PUBLIC_KEY_SIZE], // Remote NIST P-384 static public key
defrag: Mutex<RingBufferMap<u32, GatherArray<Layer::IncomingPacketBuffer, MAX_FRAGMENTS>, 8, 8>>,
}
struct SessionMutableState {
remote_session_id: Option<SessionId>, // The other side's 48-bit session ID
session_keys: [Option<SessionKey>; KEY_HISTORY_SIZE], // Buffers to store current, next, and last active key
cur_session_key_idx: usize, // Pointer used for keys[] circular buffer
offer: Option<Box<EphemeralOffer>>, // Most recent ephemeral offer sent to remote
last_remote_offer: i64, // Time of most recent ephemeral offer (ms)
}
/// Alice's KEY_OFFER, remembered so Noise agreement process can resume on KEY_COUNTER_OFFER.
struct EphemeralOffer {
id: [u8; 16], // Arbitrary random offer ID
creation_time: i64, // Local time when offer was created
ratchet_count: u64, // Ratchet count starting at zero for initial offer
ratchet_key: Option<Secret<64>>, // Ratchet key from previous offer
ss_key: Secret<64>, // Shared secret in-progress, at state after offer sent
alice_e_keypair: P384KeyPair, // NIST P-384 key pair (Noise ephemeral key for Alice)
alice_e1_keypair: Option<pqc_kyber::Keypair>, // Kyber1024 key pair (agreement result mixed post-Noise)
}
////////////////////////////////////////////////////////////////
// functions
////////////////////////////////////////////////////////////////
impl From<std::io::Error> for Error {
#[cold]
#[inline(never)]
@ -201,168 +174,6 @@ impl std::fmt::Debug for Error {
}
}
/// Result generated by the packet receive function, with possible payloads.
pub enum ReceiveResult<'a, H: ApplicationLayer> {
/// Packet is valid, no action needs to be taken.
Ok,
/// Packet is valid and a data payload was decoded and authenticated.
///
/// The returned reference is to the filled parts of the data buffer supplied to receive.
OkData(&'a mut [u8]),
/// Packet is valid and a new session was created.
///
/// The session will have already been gated by the accept_new_session() method in the Host trait.
OkNewSession(Session<H>),
/// Packet appears valid but was ignored e.g. as a duplicate.
Ignored,
}
/// 48-bit session ID (most significant 16 bits of u64 are unused)
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
#[repr(transparent)]
pub struct SessionId(u64);
impl SessionId {
/// The nil session ID used in messages initiating a new session.
///
/// This is all 1's so that ZeroTier can easily tell the difference between ZSSP init packets
/// and ZeroTier V1 packets.
pub const NIL: SessionId = SessionId(0xffffffffffff);
#[inline]
pub fn new_from_u64(i: u64) -> Option<SessionId> {
if i < Self::NIL.0 {
Some(Self(i))
} else {
None
}
}
#[inline]
pub fn new_from_reader<R: Read>(r: &mut R) -> std::io::Result<Option<SessionId>> {
let mut tmp = 0_u64.to_ne_bytes();
r.read_exact(&mut tmp[..SESSION_ID_SIZE])?;
Ok(Self::new_from_u64(u64::from_le_bytes(tmp)))
}
#[inline]
pub fn new_random() -> Self {
Self(random::next_u64_secure() % Self::NIL.0)
}
}
impl From<SessionId> for u64 {
#[inline(always)]
fn from(sid: SessionId) -> Self {
sid.0
}
}
/// State information to associate with receiving contexts such as sockets or remote paths/endpoints.
///
/// This holds the data structures used to defragment incoming packets that are not associated with an
/// existing session, which would be new attempts to create sessions. Typically one of these is associated
/// with a single listen socket, local bound port, or other inbound endpoint.
pub struct ReceiveContext<H: ApplicationLayer> {
initial_offer_defrag: Mutex<RingBufferMap<u32, GatherArray<H::IncomingPacketBuffer, KEY_EXCHANGE_MAX_FRAGMENTS>, 1024, 128>>,
incoming_init_header_check_cipher: Aes,
}
/// Trait to implement to integrate the session into an application.
///
/// Templating the session on this trait lets the code here be almost entirely transport, OS,
/// and use case independent.
pub trait ApplicationLayer: Sized {
/// Arbitrary opaque object associated with a session, such as a connection state object.
type SessionUserData;
/// Arbitrary object that dereferences to the session, such as Arc<Session<Self>>.
type SessionRef: Deref<Target = Session<Self>>;
/// A buffer containing data read from the network that can be cached.
///
/// This can be e.g. a pooled buffer that automatically returns itself to the pool when dropped.
/// It can also just be a Vec<u8> or Box<[u8]> or something like that.
type IncomingPacketBuffer: AsRef<[u8]>;
/// Remote physical address on whatever transport this session is using.
type RemoteAddress;
/// Rate limit for attempts to rekey existing sessions in milliseconds (default: 2000).
const REKEY_RATE_LIMIT_MS: i64 = 2000;
/// Get a reference to this host's static public key blob.
///
/// This must contain a NIST P-384 public key but can contain other information. In ZeroTier this
/// is a byte serialized identity. It could just be a naked NIST P-384 key if that's all you need.
fn get_local_s_public_raw(&self) -> &[u8];
/// Get SHA384(this host's static public key blob).
///
/// This allows us to avoid computing SHA384(public key blob) over and over again.
fn get_local_s_public_hash(&self) -> &[u8; 48];
/// Get a reference to this hosts' static public key's NIST P-384 secret key pair.
///
/// This must return the NIST P-384 public key that is contained within the static public key blob.
fn get_local_s_keypair(&self) -> &P384KeyPair;
/// Extract the NIST P-384 ECC public key component from a static public key blob or return None on failure.
///
/// This is called to parse the static public key blob from the other end and extract its NIST P-384 public
/// key. SECURITY NOTE: the information supplied here is from the wire so care must be taken to parse it
/// safely and fail on any error or corruption.
fn extract_s_public_from_raw(static_public: &[u8]) -> Option<P384PublicKey>;
/// Look up a local session by local session ID or return None if not found.
fn lookup_session(&self, local_session_id: SessionId) -> Option<Self::SessionRef>;
/// Rate limit and check an attempted new session (called before accept_new_session).
fn check_new_session(&self, rc: &ReceiveContext<Self>, remote_address: &Self::RemoteAddress) -> bool;
/// Check whether a new session should be accepted.
///
/// On success a tuple of local session ID, static secret, and associated object is returned. The
/// static secret is whatever results from agreement between the local and remote static public
/// keys.
fn accept_new_session(
&self,
receive_context: &ReceiveContext<Self>,
remote_address: &Self::RemoteAddress,
remote_static_public: &[u8],
remote_metadata: &[u8],
) -> Option<(SessionId, Secret<64>, Self::SessionUserData)>;
}
/// ZSSP bi-directional packet transport channel.
pub struct Session<Layer: ApplicationLayer> {
/// This side's session ID (unique on this side)
pub id: SessionId,
/// An arbitrary object associated with session (type defined in Host trait)
pub user_data: Layer::SessionUserData,
send_counter: Counter, // Outgoing packet counter and nonce state
psk: Secret<64>, // Arbitrary PSK provided by external code
noise_ss: Secret<48>, // Static raw shared ECDH NIST P-384 key
header_check_cipher: Aes, // Cipher used for header MAC (fragmentation)
state: RwLock<SessionMutableState>, // Mutable parts of state (other than defrag buffers)
remote_s_public_hash: [u8; 48], // SHA384(remote static public key blob)
remote_s_public_raw: [u8; P384_PUBLIC_KEY_SIZE], // Remote NIST P-384 static public key
defrag: Mutex<RingBufferMap<u32, GatherArray<Layer::IncomingPacketBuffer, MAX_FRAGMENTS>, 8, 8>>,
}
struct SessionMutableState {
remote_session_id: Option<SessionId>, // The other side's 48-bit session ID
session_keys: [Option<SessionKey>; KEY_HISTORY_SIZE], // Buffers to store current, next, and last active key
cur_session_key_idx: usize, // Pointer used for keys[] circular buffer
offer: Option<Box<EphemeralOffer>>, // Most recent ephemeral offer sent to remote
last_remote_offer: i64, // Time of most recent ephemeral offer (ms)
}
impl<Layer: ApplicationLayer> Session<Layer> {
/// Create a new session and send an initial key offer message to the other end.
@ -1267,84 +1078,6 @@ impl<Layer: ApplicationLayer> ReceiveContext<Layer> {
}
}
/// Outgoing packet counter with strictly ordered atomic semantics.
#[repr(transparent)]
struct Counter(AtomicU64);
impl Counter {
#[inline(always)]
fn new() -> Self {
// Using a random value has no security implication. Zero would be fine. This just
// helps randomize packet contents a bit.
Self(AtomicU64::new(random::next_u32_secure() as u64))
}
/// Get the value most recently used to send a packet.
#[inline(always)]
fn previous(&self) -> CounterValue {
CounterValue(self.0.load(Ordering::SeqCst))
}
/// Get a counter value for the next packet being sent.
#[inline(always)]
fn next(&self) -> CounterValue {
CounterValue(self.0.fetch_add(1, Ordering::SeqCst))
}
}
/// A value of the outgoing packet counter.
///
/// The used portion of the packet counter is the least significant 32 bits, but the internal
/// counter state is kept as a 64-bit integer. This makes it easier to correctly handle
/// key expiration after usage limits are reached without complicated logic to handle 32-bit
/// wrapping. Usage limits are below 2^32 so the actual 32-bit counter will not wrap for a
/// given shared secret key.
#[repr(transparent)]
#[derive(Copy, Clone)]
struct CounterValue(u64);
impl CounterValue {
#[inline(always)]
pub fn to_u32(&self) -> u32 {
self.0 as u32
}
}
/// "Canonical header" for generating 96-bit AES-GCM nonce and for inclusion in HMACs.
///
/// This is basically the actual header but with fragment count and fragment total set to zero.
/// Fragmentation is not considered when authenticating the entire packet. A separate header
/// check code is used to make fragmentation itself more robust, but that's outside the scope
/// of AEAD authentication.
#[derive(Clone, Copy)]
#[repr(C, packed)]
struct CanonicalHeader(u64, u32);
impl CanonicalHeader {
#[inline(always)]
pub fn make(session_id: SessionId, packet_type: u8, counter: u32) -> Self {
CanonicalHeader(
(u64::from(session_id) | (packet_type as u64).wrapping_shl(48)).to_le(),
counter.to_le(),
)
}
#[inline(always)]
pub fn as_bytes(&self) -> &[u8; 12] {
memory::as_byte_array(self)
}
}
/// Alice's KEY_OFFER, remembered so Noise agreement process can resume on KEY_COUNTER_OFFER.
struct EphemeralOffer {
id: [u8; 16], // Arbitrary random offer ID
creation_time: i64, // Local time when offer was created
ratchet_count: u64, // Ratchet count starting at zero for initial offer
ratchet_key: Option<Secret<64>>, // Ratchet key from previous offer
ss_key: Secret<64>, // Shared secret in-progress, at state after offer sent
alice_e_keypair: P384KeyPair, // NIST P-384 key pair (Noise ephemeral key for Alice)
alice_e1_keypair: Option<pqc_kyber::Keypair>, // Kyber1024 key pair (agreement result mixed post-Noise)
}
/// Create and send an ephemeral offer, returning the EphemeralOffer part that must be saved.
fn send_ephemeral_offer<SendFunction: FnMut(&mut [u8])>(
@ -1635,13 +1368,6 @@ fn parse_key_offer_after_header(
))
}
/// Was this side the one who sent the first offer (Alice) or countered (Bob).
/// Note that role is not fixed. Either side can take either role. It's just who
/// initiated first.
enum Role {
Alice,
Bob,
}
/// Key lifetime manager state and logic (separate to spotlight and keep clean)
struct KeyLifetime {
@ -1773,224 +1499,3 @@ fn secret_fingerprint(key: &[u8]) -> [u8; 48] {
tmp.update(key);
tmp.finish()
}
#[cfg(test)]
mod tests {
use std::collections::LinkedList;
use std::sync::{Arc, Mutex};
use zerotier_utils::hex;
#[allow(unused_imports)]
use super::*;
struct TestHost {
local_s: P384KeyPair,
local_s_hash: [u8; 48],
psk: Secret<64>,
session: Mutex<Option<Arc<Session<Box<TestHost>>>>>,
session_id_counter: Mutex<u64>,
queue: Mutex<LinkedList<Vec<u8>>>,
key_id: Mutex<[u8; 16]>,
this_name: &'static str,
other_name: &'static str,
}
impl TestHost {
fn new(psk: Secret<64>, this_name: &'static str, other_name: &'static str) -> Self {
let local_s = P384KeyPair::generate();
let local_s_hash = SHA384::hash(local_s.public_key_bytes());
Self {
local_s,
local_s_hash,
psk,
session: Mutex::new(None),
session_id_counter: Mutex::new(1),
queue: Mutex::new(LinkedList::new()),
key_id: Mutex::new([0; 16]),
this_name,
other_name,
}
}
}
impl ApplicationLayer for Box<TestHost> {
type SessionUserData = u32;
type SessionRef = Arc<Session<Box<TestHost>>>;
type IncomingPacketBuffer = Vec<u8>;
type RemoteAddress = u32;
const REKEY_RATE_LIMIT_MS: i64 = 0;
fn get_local_s_public_raw(&self) -> &[u8] {
self.local_s.public_key_bytes()
}
fn get_local_s_public_hash(&self) -> &[u8; 48] {
&self.local_s_hash
}
fn get_local_s_keypair(&self) -> &P384KeyPair {
&self.local_s
}
fn extract_s_public_from_raw(static_public: &[u8]) -> Option<P384PublicKey> {
P384PublicKey::from_bytes(static_public)
}
fn lookup_session(&self, local_session_id: SessionId) -> Option<Self::SessionRef> {
self.session.lock().unwrap().as_ref().and_then(|s| {
if s.id == local_session_id {
Some(s.clone())
} else {
None
}
})
}
fn check_new_session(&self, _: &ReceiveContext<Self>, _: &Self::RemoteAddress) -> bool {
true
}
fn accept_new_session(
&self,
_: &ReceiveContext<Self>,
_: &u32,
_: &[u8],
_: &[u8],
) -> Option<(SessionId, Secret<64>, Self::SessionUserData)> {
loop {
let mut new_id = self.session_id_counter.lock().unwrap();
*new_id += 1;
return Some((SessionId::new_from_u64(*new_id).unwrap(), self.psk.clone(), 0));
}
}
}
#[allow(unused_variables)]
#[test]
fn establish_session() {
let mut data_buf = [0_u8; (1280 - 32) * MAX_FRAGMENTS];
let mut mtu_buffer = [0_u8; 1280];
let mut psk: Secret<64> = Secret::default();
random::fill_bytes_secure(&mut psk.0);
let alice_host = Box::new(TestHost::new(psk.clone(), "alice", "bob"));
let bob_host = Box::new(TestHost::new(psk.clone(), "bob", "alice"));
let alice_rc: Box<ReceiveContext<Box<TestHost>>> = Box::new(ReceiveContext::new(&alice_host));
let bob_rc: Box<ReceiveContext<Box<TestHost>>> = Box::new(ReceiveContext::new(&bob_host));
//println!("zssp: size of session (bytes): {}", std::mem::size_of::<Session<Box<TestHost>>>());
let _ = alice_host.session.lock().unwrap().insert(Arc::new(
Session::start_new(
&alice_host,
|data| bob_host.queue.lock().unwrap().push_front(data.to_vec()),
SessionId::new_random(),
bob_host.local_s.public_key_bytes(),
&[],
&psk,
1,
mtu_buffer.len(),
1,
)
.unwrap(),
));
let mut ts = 0;
for test_loop in 0..256 {
for host in [&alice_host, &bob_host] {
let send_to_other = |data: &mut [u8]| {
if std::ptr::eq(host, &alice_host) {
bob_host.queue.lock().unwrap().push_front(data.to_vec());
} else {
alice_host.queue.lock().unwrap().push_front(data.to_vec());
}
};
let rc = if std::ptr::eq(host, &alice_host) {
&alice_rc
} else {
&bob_rc
};
loop {
if let Some(qi) = host.queue.lock().unwrap().pop_back() {
let qi_len = qi.len();
ts += 1;
let r = rc.receive(host, &0, send_to_other, &mut data_buf, qi, mtu_buffer.len(), ts);
if r.is_ok() {
let r = r.unwrap();
match r {
ReceiveResult::Ok => {
//println!("zssp: {} => {} ({}): Ok", host.other_name, host.this_name, qi_len);
}
ReceiveResult::OkData(data) => {
//println!("zssp: {} => {} ({}): OkData length=={}", host.other_name, host.this_name, qi_len, data.len());
assert!(!data.iter().any(|x| *x != 0x12));
}
ReceiveResult::OkNewSession(new_session) => {
println!(
"zssp: {} => {} ({}): OkNewSession ({})",
host.other_name,
host.this_name,
qi_len,
u64::from(new_session.id)
);
let mut hs = host.session.lock().unwrap();
assert!(hs.is_none());
let _ = hs.insert(Arc::new(new_session));
}
ReceiveResult::Ignored => {
println!("zssp: {} => {} ({}): Ignored", host.other_name, host.this_name, qi_len);
}
}
} else {
println!(
"zssp: {} => {} ({}): error: {}",
host.other_name,
host.this_name,
qi_len,
r.err().unwrap().to_string()
);
panic!();
}
} else {
break;
}
}
data_buf.fill(0x12);
if let Some(session) = host.session.lock().unwrap().as_ref().cloned() {
if session.established() {
{
let mut key_id = host.key_id.lock().unwrap();
let security_info = session.status().unwrap();
if !security_info.0.eq(key_id.as_ref()) {
*key_id = security_info.0;
println!(
"zssp: new key at {}: fingerprint {} ratchet {} kyber {}",
host.this_name,
hex::to_string(key_id.as_ref()),
security_info.2,
security_info.3
);
}
}
for _ in 0..4 {
assert!(session
.send(
send_to_other,
&mut mtu_buffer,
&data_buf[..((random::xorshift64_random() as usize) % data_buf.len())]
)
.is_ok());
}
if (test_loop % 8) == 0 && test_loop >= 8 && host.this_name.eq("alice") {
session.service(host, send_to_other, &[], mtu_buffer.len(), test_loop as i64, true);
}
}
}
}
}
}
}