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ZeroTierOne/node/Packet.hpp

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/*
* ZeroTier One - Network Virtualization Everywhere
* Copyright (C) 2011-2015 ZeroTier, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* --
*
* ZeroTier may be used and distributed under the terms of the GPLv3, which
* are available at: http://www.gnu.org/licenses/gpl-3.0.html
*
* If you would like to embed ZeroTier into a commercial application or
* redistribute it in a modified binary form, please contact ZeroTier Networks
* LLC. Start here: http://www.zerotier.com/
*/
#ifndef ZT_N_PACKET_HPP
#define ZT_N_PACKET_HPP
#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <string>
#include <iostream>
#include "Constants.hpp"
#include "Address.hpp"
#include "Poly1305.hpp"
#include "Salsa20.hpp"
#include "Utils.hpp"
#include "Buffer.hpp"
#include "../ext/lz4/lz4.h"
/**
* Protocol version -- incremented only for MAJOR changes
*
* 1 - 0.2.0 ... 0.2.5
* 2 - 0.3.0 ... 0.4.5
* * Added signature and originating peer to multicast frame
* * Double size of multicast frame bloom filter
* 3 - 0.5.0 ... 0.6.0
* * Yet another multicast redesign
* * New crypto completely changes key agreement cipher
* 4 - 0.6.0 ... CURRENT
* * New identity format based on hashcash design
*
* This isn't going to change again for a long time unless your
* author wakes up again at 4am with another great idea. :P
*/
#define ZT_PROTO_VERSION 4
/**
* Minimum supported protocol version
*/
#define ZT_PROTO_VERSION_MIN 4
/**
* Maximum hop count allowed by packet structure (3 bits, 0-7)
*
* This is not necessarily the maximum hop counter after which
* relaying is no longer performed.
*/
#define ZT_PROTO_MAX_HOPS 7
/**
* Cipher suite: Curve25519/Poly1305/Salsa20/12 without payload encryption
*
* This specifies Poly1305 MAC using a 32-bit key derived from the first
* 32 bytes of a Salsa20/12 keystream as in the Salsa20/12 cipher suite,
* but the payload is not encrypted. This is currently only used to send
* HELLO since that's the public key specification packet and must be
* sent in the clear. Key agreement is performed using Curve25519 elliptic
* curve Diffie-Hellman.
*/
#define ZT_PROTO_CIPHER_SUITE__C25519_POLY1305_NONE 0
/**
* Cipher suite: Curve25519/Poly1305/Salsa20/12
*
* This specifies Poly1305 using the first 32 bytes of a Salsa20/12 key
* stream as its one-time-use key followed by payload encryption with
* the remaining Salsa20/12 key stream. Key agreement is performed using
* Curve25519 elliptic curve Diffie-Hellman.
*/
#define ZT_PROTO_CIPHER_SUITE__C25519_POLY1305_SALSA2012 1
/**
* Cipher suite: PFS negotiated ephemeral cipher suite and authentication
*
* This message is encrypted with the latest negotiated ephemeral (PFS)
* key pair and cipher suite. If authentication fails, VERB_SET_EPHEMERAL_KEY
* may be sent to renegotiate ephemeral keys. To prevent attacks, this
* attempted renegotiation should be limited to some sane rate such as
* once per second.
*/
#define ZT_PROTO_CIPHER_SUITE__EPHEMERAL 7
/**
* DEPRECATED payload encrypted flag, will be removed for re-use soon.
*
* This has been replaced by the two-bit cipher suite selection field where
* a value of 0 indicated unencrypted (but authenticated) messages.
*/
#define ZT_PROTO_FLAG_ENCRYPTED 0x80
/**
* Header flag indicating that a packet is fragmented
*
* If this flag is set, the receiver knows to expect more than one fragment.
* See Packet::Fragment for details.
*/
#define ZT_PROTO_FLAG_FRAGMENTED 0x40
/**
* Verb flag indicating payload is compressed with LZ4
*/
#define ZT_PROTO_VERB_FLAG_COMPRESSED 0x80
/**
* Rounds used for Salsa20 encryption in ZT
*/
#define ZT_PROTO_SALSA20_ROUNDS 12
// Indices of fields in normal packet header -- do not change as this
// might require both code rework and will break compatibility.
#define ZT_PACKET_IDX_IV 0
#define ZT_PACKET_IDX_DEST 8
#define ZT_PACKET_IDX_SOURCE 13
#define ZT_PACKET_IDX_FLAGS 18
#define ZT_PACKET_IDX_MAC 19
#define ZT_PACKET_IDX_VERB 27
#define ZT_PACKET_IDX_PAYLOAD 28
/**
* Packet buffer size (can be changed)
*/
#define ZT_PROTO_MAX_PACKET_LENGTH (ZT_MAX_PACKET_FRAGMENTS * ZT_UDP_DEFAULT_PAYLOAD_MTU)
/**
* Minimum viable packet length (also length of header)
*/
#define ZT_PROTO_MIN_PACKET_LENGTH ZT_PACKET_IDX_PAYLOAD
// Indexes of fields in fragment header -- also can't be changed without
// breaking compatibility.
#define ZT_PACKET_FRAGMENT_IDX_PACKET_ID 0
#define ZT_PACKET_FRAGMENT_IDX_DEST 8
#define ZT_PACKET_FRAGMENT_IDX_FRAGMENT_INDICATOR 13
#define ZT_PACKET_FRAGMENT_IDX_FRAGMENT_NO 14
#define ZT_PACKET_FRAGMENT_IDX_HOPS 15
#define ZT_PACKET_FRAGMENT_IDX_PAYLOAD 16
/**
* Value found at ZT_PACKET_FRAGMENT_IDX_FRAGMENT_INDICATOR in fragments
*/
#define ZT_PACKET_FRAGMENT_INDICATOR ZT_ADDRESS_RESERVED_PREFIX
/**
* Minimum viable fragment length
*/
#define ZT_PROTO_MIN_FRAGMENT_LENGTH ZT_PACKET_FRAGMENT_IDX_PAYLOAD
/**
* Length of LAN beacon packets
*/
#define ZT_PROTO_BEACON_LENGTH 13
/**
* Index of address in a LAN beacon
*/
#define ZT_PROTO_BEACON_IDX_ADDRESS 8
// Destination address types from HELLO and OK(HELLO)
#define ZT_PROTO_DEST_ADDRESS_TYPE_NONE 0
#define ZT_PROTO_DEST_ADDRESS_TYPE_ETHERNET 1
#define ZT_PROTO_DEST_ADDRESS_TYPE_IPV4 4
#define ZT_PROTO_DEST_ADDRESS_TYPE_IPV6 6
// Ephemeral key record flags
#define ZT_PROTO_EPHEMERAL_KEY_FLAG_FIPS 0x01
// Ephemeral key record symmetric cipher types
#define ZT_PROTO_EPHEMERAL_KEY_SYMMETRIC_CIPHER_SALSA2012_POLY1305 0x01
#define ZT_PROTO_EPHEMERAL_KEY_SYMMETRIC_CIPHER_AES256_GCM 0x02
// Ephemeral key record public key types
#define ZT_PROTO_EPHEMERAL_KEY_PK_C25519 0x01
#define ZT_PROTO_EPHEMERAL_KEY_PK_NISTP256 0x02
// Field incides for parsing verbs -------------------------------------------
// Some verbs have variable-length fields. Those aren't fully defined here
// yet-- instead they are parsed using relative indexes in IncomingPacket.
// See their respective handler functions.
#define ZT_PROTO_VERB_HELLO_IDX_PROTOCOL_VERSION (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_HELLO_IDX_MAJOR_VERSION (ZT_PROTO_VERB_HELLO_IDX_PROTOCOL_VERSION + 1)
#define ZT_PROTO_VERB_HELLO_IDX_MINOR_VERSION (ZT_PROTO_VERB_HELLO_IDX_MAJOR_VERSION + 1)
#define ZT_PROTO_VERB_HELLO_IDX_REVISION (ZT_PROTO_VERB_HELLO_IDX_MINOR_VERSION + 1)
#define ZT_PROTO_VERB_HELLO_IDX_TIMESTAMP (ZT_PROTO_VERB_HELLO_IDX_REVISION + 2)
#define ZT_PROTO_VERB_HELLO_IDX_IDENTITY (ZT_PROTO_VERB_HELLO_IDX_TIMESTAMP + 8)
#define ZT_PROTO_VERB_ERROR_IDX_IN_RE_VERB (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_ERROR_IDX_IN_RE_PACKET_ID (ZT_PROTO_VERB_ERROR_IDX_IN_RE_VERB + 1)
#define ZT_PROTO_VERB_ERROR_IDX_ERROR_CODE (ZT_PROTO_VERB_ERROR_IDX_IN_RE_PACKET_ID + 8)
#define ZT_PROTO_VERB_ERROR_IDX_PAYLOAD (ZT_PROTO_VERB_ERROR_IDX_ERROR_CODE + 1)
#define ZT_PROTO_VERB_OK_IDX_IN_RE_VERB (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_OK_IDX_IN_RE_PACKET_ID (ZT_PROTO_VERB_OK_IDX_IN_RE_VERB + 1)
#define ZT_PROTO_VERB_OK_IDX_PAYLOAD (ZT_PROTO_VERB_OK_IDX_IN_RE_PACKET_ID + 8)
#define ZT_PROTO_VERB_WHOIS_IDX_ZTADDRESS (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_RENDEZVOUS_IDX_FLAGS (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_RENDEZVOUS_IDX_ZTADDRESS (ZT_PROTO_VERB_RENDEZVOUS_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_RENDEZVOUS_IDX_PORT (ZT_PROTO_VERB_RENDEZVOUS_IDX_ZTADDRESS + 5)
#define ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRLEN (ZT_PROTO_VERB_RENDEZVOUS_IDX_PORT + 2)
#define ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRESS (ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRLEN + 1)
#define ZT_PROTO_VERB_FRAME_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_FRAME_IDX_ETHERTYPE (ZT_PROTO_VERB_FRAME_IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_FRAME_IDX_PAYLOAD (ZT_PROTO_VERB_FRAME_IDX_ETHERTYPE + 2)
#define ZT_PROTO_VERB_EXT_FRAME_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_EXT_FRAME_LEN_NETWORK_ID 8
#define ZT_PROTO_VERB_EXT_FRAME_IDX_FLAGS (ZT_PROTO_VERB_EXT_FRAME_IDX_NETWORK_ID + ZT_PROTO_VERB_EXT_FRAME_LEN_NETWORK_ID)
#define ZT_PROTO_VERB_EXT_FRAME_LEN_FLAGS 1
#define ZT_PROTO_VERB_EXT_FRAME_IDX_COM (ZT_PROTO_VERB_EXT_FRAME_IDX_FLAGS + ZT_PROTO_VERB_EXT_FRAME_LEN_FLAGS)
#define ZT_PROTO_VERB_EXT_FRAME_IDX_TO (ZT_PROTO_VERB_EXT_FRAME_IDX_FLAGS + ZT_PROTO_VERB_EXT_FRAME_LEN_FLAGS)
#define ZT_PROTO_VERB_EXT_FRAME_LEN_TO 6
#define ZT_PROTO_VERB_EXT_FRAME_IDX_FROM (ZT_PROTO_VERB_EXT_FRAME_IDX_TO + ZT_PROTO_VERB_EXT_FRAME_LEN_TO)
#define ZT_PROTO_VERB_EXT_FRAME_LEN_FROM 6
#define ZT_PROTO_VERB_EXT_FRAME_IDX_ETHERTYPE (ZT_PROTO_VERB_EXT_FRAME_IDX_FROM + ZT_PROTO_VERB_EXT_FRAME_LEN_FROM)
#define ZT_PROTO_VERB_EXT_FRAME_LEN_ETHERTYPE 2
#define ZT_PROTO_VERB_EXT_FRAME_IDX_PAYLOAD (ZT_PROTO_VERB_EXT_FRAME_IDX_ETHERTYPE + ZT_PROTO_VERB_EXT_FRAME_LEN_ETHERTYPE)
#define ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT_LEN (ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT (ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST_IDX_DICT_LEN + 2)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_FLAGS (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC + 6)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_GATHER_LIMIT (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI + 4)
// Note: COM, GATHER_LIMIT, and SOURCE_MAC are optional, and so are specified without size
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_FLAGS (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_COM (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_GATHER_LIMIT (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_SOURCE_MAC (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_DEST_MAC (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_DEST_ADI (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_DEST_MAC + 6)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_ETHERTYPE (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_DEST_ADI + 4)
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_FRAME (ZT_PROTO_VERB_MULTICAST_FRAME_IDX_ETHERTYPE + 2)
#define ZT_PROTO_VERB_HELLO__OK__IDX_TIMESTAMP (ZT_PROTO_VERB_OK_IDX_PAYLOAD)
#define ZT_PROTO_VERB_HELLO__OK__IDX_PROTOCOL_VERSION (ZT_PROTO_VERB_HELLO__OK__IDX_TIMESTAMP + 8)
#define ZT_PROTO_VERB_HELLO__OK__IDX_MAJOR_VERSION (ZT_PROTO_VERB_HELLO__OK__IDX_PROTOCOL_VERSION + 1)
#define ZT_PROTO_VERB_HELLO__OK__IDX_MINOR_VERSION (ZT_PROTO_VERB_HELLO__OK__IDX_MAJOR_VERSION + 1)
#define ZT_PROTO_VERB_HELLO__OK__IDX_REVISION (ZT_PROTO_VERB_HELLO__OK__IDX_MINOR_VERSION + 1)
#define ZT_PROTO_VERB_WHOIS__OK__IDX_IDENTITY (ZT_PROTO_VERB_OK_IDX_PAYLOAD)
#define ZT_PROTO_VERB_WHOIS__ERROR__IDX_ZTADDRESS (ZT_PROTO_VERB_ERROR_IDX_PAYLOAD)
#define ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_NETWORK_ID (ZT_PROTO_VERB_OK_IDX_PAYLOAD)
#define ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT_LEN (ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT (ZT_PROTO_VERB_NETWORK_CONFIG_REQUEST__OK__IDX_DICT_LEN + 2)
#define ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_NETWORK_ID (ZT_PROTO_VERB_OK_IDX_PAYLOAD)
#define ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_MAC (ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_ADI (ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_MAC + 6)
#define ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_GATHER_RESULTS (ZT_PROTO_VERB_MULTICAST_GATHER__OK__IDX_ADI + 4)
#define ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_NETWORK_ID (ZT_PROTO_VERB_OK_IDX_PAYLOAD)
#define ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_MAC (ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_NETWORK_ID + 8)
#define ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_ADI (ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_MAC + 6)
#define ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_FLAGS (ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_ADI + 4)
#define ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_COM_AND_GATHER_RESULTS (ZT_PROTO_VERB_MULTICAST_FRAME__OK__IDX_FLAGS + 1)
// ---------------------------------------------------------------------------
namespace ZeroTier {
/**
* ZeroTier packet
*
* Packet format:
* <[8] random initialization vector (doubles as 64-bit packet ID)>
* <[5] destination ZT address>
* <[5] source ZT address>
* <[1] flags/cipher (top 5 bits) and ZT hop count (last 3 bits)>
* <[8] 8-bit MAC (currently first 8 bytes of poly1305 tag)>
* [... -- begin encryption envelope -- ...]
* <[1] encrypted flags (top 3 bits) and verb (last 5 bits)>
* [... verb-specific payload ...]
*
* Packets smaller than 28 bytes are invalid and silently discarded.
*
* The flags/cipher/hops bit field is: FFCCCHHH where C is a 3-bit cipher
* selection allowing up to 7 cipher suites, F is outside-envelope flags,
* and H is hop count.
*
* The three-bit hop count is the only part of a packet that is mutable in
* transit without invalidating the MAC. All other bits in the packet are
* immutable. This is because intermediate nodes can increment the hop
* count up to 7 (protocol max).
*
* http://tonyarcieri.com/all-the-crypto-code-youve-ever-written-is-probably-broken
*
* For unencrypted packets, MAC is computed on plaintext. Only HELLO is ever
* sent in the clear, as it's the "here is my public key" message.
*
* Beacon format and beacon packets:
* <[8] 8 random bytes>
* <[5] sender ZT address>
*
* A beacon is a 13-byte packet containing only the address of the sender.
* Receiving peers may or may not respond to beacons with a HELLO or other
* message to initiate direct communication.
*
* Beacons may be used for direct LAN announcement or NAT traversal.
*/
class Packet : public Buffer<ZT_PROTO_MAX_PACKET_LENGTH>
{
public:
/**
* A packet fragment
*
* Fragments are sent if a packet is larger than UDP MTU. The first fragment
* is sent with its normal header with the fragmented flag set. Remaining
* fragments are sent this way.
*
* The fragmented bit indicates that there is at least one fragment. Fragments
* themselves contain the total, so the receiver must "learn" this from the
* first fragment it receives.
*
* Fragments are sent with the following format:
* <[8] packet ID of packet whose fragment this belongs to>
* <[5] destination ZT address>
* <[1] 0xff, a reserved address, signals that this isn't a normal packet>
* <[1] total fragments (most significant 4 bits), fragment no (LS 4 bits)>
* <[1] ZT hop count (top 5 bits unused and must be zero)>
* <[...] fragment data>
*
* The protocol supports a maximum of 16 fragments. If a fragment is received
* before its main packet header, it should be cached for a brief period of
* time to see if its parent arrives. Loss of any fragment constitutes packet
* loss; there is no retransmission mechanism. The receiver must wait for full
* receipt to authenticate and decrypt; there is no per-fragment MAC. (But if
* fragments are corrupt, the MAC will fail for the whole assembled packet.)
*/
class Fragment : public Buffer<ZT_PROTO_MAX_PACKET_LENGTH>
{
public:
Fragment() :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>()
{
}
template<unsigned int C2>
Fragment(const Buffer<C2> &b)
throw(std::out_of_range) :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(b)
{
}
Fragment(const void *data,unsigned int len) :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(data,len)
{
}
/**
* Initialize from a packet
*
* @param p Original assembled packet
* @param fragStart Start of fragment (raw index in packet data)
* @param fragLen Length of fragment in bytes
* @param fragNo Which fragment (>= 1, since 0 is Packet with end chopped off)
* @param fragTotal Total number of fragments (including 0)
* @throws std::out_of_range Packet size would exceed buffer
*/
Fragment(const Packet &p,unsigned int fragStart,unsigned int fragLen,unsigned int fragNo,unsigned int fragTotal)
throw(std::out_of_range)
{
init(p,fragStart,fragLen,fragNo,fragTotal);
}
/**
* Initialize from a packet
*
* @param p Original assembled packet
* @param fragStart Start of fragment (raw index in packet data)
* @param fragLen Length of fragment in bytes
* @param fragNo Which fragment (>= 1, since 0 is Packet with end chopped off)
* @param fragTotal Total number of fragments (including 0)
* @throws std::out_of_range Packet size would exceed buffer
*/
inline void init(const Packet &p,unsigned int fragStart,unsigned int fragLen,unsigned int fragNo,unsigned int fragTotal)
throw(std::out_of_range)
{
if ((fragStart + fragLen) > p.size())
throw std::out_of_range("Packet::Fragment: tried to construct fragment of packet past its length");
setSize(fragLen + ZT_PROTO_MIN_FRAGMENT_LENGTH);
// NOTE: this copies both the IV/packet ID and the destination address.
memcpy(field(ZT_PACKET_FRAGMENT_IDX_PACKET_ID,13),p.field(ZT_PACKET_IDX_IV,13),13);
(*this)[ZT_PACKET_FRAGMENT_IDX_FRAGMENT_INDICATOR] = ZT_PACKET_FRAGMENT_INDICATOR;
(*this)[ZT_PACKET_FRAGMENT_IDX_FRAGMENT_NO] = (char)(((fragTotal & 0xf) << 4) | (fragNo & 0xf));
(*this)[ZT_PACKET_FRAGMENT_IDX_HOPS] = 0;
memcpy(field(ZT_PACKET_FRAGMENT_IDX_PAYLOAD,fragLen),p.field(fragStart,fragLen),fragLen);
}
/**
* Get this fragment's destination
*
* @return Destination ZT address
*/
inline Address destination() const { return Address(field(ZT_PACKET_FRAGMENT_IDX_DEST,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH); }
/**
* @return True if fragment is of a valid length
*/
inline bool lengthValid() const { return (size() >= ZT_PACKET_FRAGMENT_IDX_PAYLOAD); }
/**
* @return ID of packet this is a fragment of
*/
inline uint64_t packetId() const { return at<uint64_t>(ZT_PACKET_FRAGMENT_IDX_PACKET_ID); }
/**
* @return Total number of fragments in packet
*/
inline unsigned int totalFragments() const { return (((unsigned int)((*this)[ZT_PACKET_FRAGMENT_IDX_FRAGMENT_NO]) >> 4) & 0xf); }
/**
* @return Fragment number of this fragment
*/
inline unsigned int fragmentNumber() const { return ((unsigned int)((*this)[ZT_PACKET_FRAGMENT_IDX_FRAGMENT_NO]) & 0xf); }
/**
* @return Fragment ZT hop count
*/
inline unsigned int hops() const { return (unsigned int)((*this)[ZT_PACKET_FRAGMENT_IDX_HOPS]); }
/**
* Increment this packet's hop count
*/
inline void incrementHops()
{
(*this)[ZT_PACKET_FRAGMENT_IDX_HOPS] = (((*this)[ZT_PACKET_FRAGMENT_IDX_HOPS]) + 1) & ZT_PROTO_MAX_HOPS;
}
/**
* @return Length of payload in bytes
*/
inline unsigned int payloadLength() const { return ((size() > ZT_PACKET_FRAGMENT_IDX_PAYLOAD) ? (size() - ZT_PACKET_FRAGMENT_IDX_PAYLOAD) : 0); }
/**
* @return Raw packet payload
*/
inline const unsigned char *payload() const
{
return field(ZT_PACKET_FRAGMENT_IDX_PAYLOAD,size() - ZT_PACKET_FRAGMENT_IDX_PAYLOAD);
}
};
/**
* ZeroTier protocol verbs
*/
enum Verb /* Max value: 32 (5 bits) */
{
/* No operation, payload ignored, no reply */
VERB_NOP = 0,
/* Announcement of a node's existence:
* <[1] protocol version>
* <[1] software major version>
* <[1] software minor version>
* <[2] software revision>
* <[8] timestamp (ms since epoch)>
* <[...] binary serialized identity (see Identity)>
* <[1] destination address type>
* [<[...] destination address>]
*
* This is the only message that ever must be sent in the clear, since it
* is used to push an identity to a new peer.
*
* The destination address is the wire address to which this packet is
* being sent, and in OK is *also* the destination address of the OK
* packet. This can be used by the receiver to detect NAT, learn its real
* external address if behind NAT, and detect changes to its external
* address that require re-establishing connectivity.
*
* Destination address types and formats (not all of these are used now):
* 0 - None -- no destination address data present
* 1 - Ethernet address -- format: <[6] Ethernet MAC>
* 4 - 6-byte IPv4 UDP address/port -- format: <[4] IP>, <[2] port>
* 6 - 18-byte IPv6 UDP address/port -- format: <[16] IP>, <[2] port>
*
* OK payload:
* <[8] timestamp (echoed from original HELLO)>
* <[1] protocol version (of responder)>
* <[1] software major version (of responder)>
* <[1] software minor version (of responder)>
* <[2] software revision (of responder)>
* <[1] destination address type (for this OK, not copied from HELLO)>
* [<[...] destination address>]
*
* ERROR has no payload.
*/
VERB_HELLO = 1,
/* Error response:
* <[1] in-re verb>
* <[8] in-re packet ID>
* <[1] error code>
* <[...] error-dependent payload>
*/
VERB_ERROR = 2,
/* Success response:
* <[1] in-re verb>
* <[8] in-re packet ID>
* <[...] request-specific payload>
*/
VERB_OK = 3,
/* Query an identity by address:
* <[5] address to look up>
*
* OK response payload:
* <[...] binary serialized identity>
*
* ERROR response payload:
* <[5] address>
*/
VERB_WHOIS = 4,
/* Meet another node at a given protocol address:
* <[1] flags (unused, currently 0)>
* <[5] ZeroTier address of peer that might be found at this address>
* <[2] 16-bit protocol address port>
* <[1] protocol address length (4 for IPv4, 16 for IPv6)>
* <[...] protocol address (network byte order)>
*
* This is sent by a relaying node to initiate NAT traversal between two
* peers that are communicating by way of indirect relay. The relay will
* send this to both peers at the same time on a periodic basis, telling
* each where it might find the other on the network.
*
* Upon receipt a peer sends HELLO to establish a direct link.
*
* Nodes should implement rate control, limiting the rate at which they
* respond to these packets to prevent their use in DDOS attacks. Nodes
* may also ignore these messages if a peer is not known or is not being
* actively communicated with.
*
* No OK or ERROR is generated.
*/
VERB_RENDEZVOUS = 5,
/* ZT-to-ZT unicast ethernet frame (shortened EXT_FRAME):
* <[8] 64-bit network ID>
* <[2] 16-bit ethertype>
* <[...] ethernet payload>
*
* MAC addresses are derived from the packet's source and destination
* ZeroTier addresses. This is a shortened EXT_FRAME that elides full
* Ethernet framing and other optional flags and features when they
* are not necessary.
*
* ERROR may be generated if a membership certificate is needed for a
* closed network. Payload will be network ID.
*/
VERB_FRAME = 6,
/* Full Ethernet frame with MAC addressing and optional fields:
* <[8] 64-bit network ID>
* <[1] flags>
* [<[...] certificate of network membership>]
* <[6] destination MAC or all zero for destination node>
* <[6] source MAC or all zero for node of origin>
* <[2] 16-bit ethertype>
* <[...] ethernet payload>
*
* Flags:
* 0x01 - Certificate of network membership is attached
*
* An extended frame carries full MAC addressing, making them a
* superset of VERB_FRAME. They're used for bridging or when we
* want to attach a certificate since FRAME does not support that.
*
* Multicast frames may not be sent as EXT_FRAME.
*
* ERROR may be generated if a membership certificate is needed for a
* closed network. Payload will be network ID.
*/
VERB_EXT_FRAME = 7,
/* DEPRECATED */
VERB_P5_MULTICAST_FRAME = 8,
/* Announce interest in multicast group(s):
* <[8] 64-bit network ID>
* <[6] multicast Ethernet address>
* <[4] multicast additional distinguishing information (ADI)>
* [... additional tuples of network/address/adi ...]
*
* LIKEs are sent to peers with whom you have a direct peer to peer
* connection, and always including root servers.
*
* OK/ERROR are not generated.
*/
VERB_MULTICAST_LIKE = 9,
/* Network member certificate replication/push:
* <[...] serialized certificate of membership>
* [ ... additional certificates may follow ...]
*
* Certificate contains network ID, peer it was issued for, etc.
*
* OK/ERROR are not generated.
*/
VERB_NETWORK_MEMBERSHIP_CERTIFICATE = 10,
/* Network configuration request:
* <[8] 64-bit network ID>
* <[2] 16-bit length of request meta-data dictionary>
* <[...] string-serialized request meta-data>
* [<[8] 64-bit revision of netconf we currently have>]
*
* This message requests network configuration from a node capable of
* providing it. If the optional revision is included, a response is
* only generated if there is a newer network configuration available.
*
* OK response payload:
* <[8] 64-bit network ID>
* <[2] 16-bit length of network configuration dictionary>
* <[...] network configuration dictionary>
*
* OK returns a Dictionary (string serialized) containing the network's
* configuration and IP address assignment information for the querying
* node. It also contains a membership certificate that the querying
* node can push to other peers to demonstrate its right to speak on
* a given network.
*
* When a new network configuration is received, another config request
* should be sent with the new netconf's revision. This confirms receipt
* and also causes any subsequent changes to rapidly propagate as this
* cycle will repeat until there are no changes. This is optional but
* recommended behavior.
*
* ERROR response payload:
* <[8] 64-bit network ID>
*
* UNSUPPORTED_OPERATION is returned if this service is not supported,
* and OBJ_NOT_FOUND if the queried network ID was not found.
*/
VERB_NETWORK_CONFIG_REQUEST = 11,
/* Network configuration refresh request:
* <[...] array of 64-bit network IDs>
*
* This message can be sent by the network configuration master node
* to request that nodes refresh their network configuration. It can
* thus be used to "push" updates so that network config changes will
* take effect quickly.
*
* It does not generate an OK or ERROR message, and is treated only as
* a hint to refresh now.
*/
VERB_NETWORK_CONFIG_REFRESH = 12,
/* Request endpoints for multicast distribution:
* <[8] 64-bit network ID>
* <[1] flags>
* <[6] MAC address of multicast group being queried>
* <[4] 32-bit ADI for multicast group being queried>
* <[4] 32-bit requested max number of multicast peers>
* [<[...] network certificate of membership>]
*
* Flags:
* 0x01 - Network certificate of membership is attached
*
* This message asks a peer for additional known endpoints that have
* LIKEd a given multicast group. It's sent when the sender wishes
* to send multicast but does not have the desired number of recipient
* peers.
*
* OK response payload:
* <[8] 64-bit network ID>
* <[6] MAC address of multicast group being queried>
* <[4] 32-bit ADI for multicast group being queried>
* [begin gather results -- these same fields can be in OK(MULTICAST_FRAME)]
* <[4] 32-bit total number of known members in this multicast group>
* <[2] 16-bit number of members enumerated in this packet>
* <[...] series of 5-byte ZeroTier addresses of enumerated members>
*
* If no endpoints are known, OK and ERROR are both optional. It's okay
* to return nothing in that case since gathering is "lazy."
*
* ERROR response payload:
* <[8] 64-bit network ID>
* <[6] MAC address of multicast group being queried>
* <[4] 32-bit ADI for multicast group being queried>
*
* ERRORs are optional and are only generated if permission is denied,
* certificate of membership is out of date, etc.
*/
VERB_MULTICAST_GATHER = 13,
/* Multicast frame:
* <[8] 64-bit network ID>
* <[1] flags>
* [<[...] network certificate of membership>]
* [<[4] 32-bit implicit gather limit>]
* [<[6] source MAC>]
* <[6] destination MAC (multicast address)>
* <[4] 32-bit multicast ADI (multicast address extension)>
* <[2] 16-bit ethertype>
* <[...] ethernet payload>
*
* Flags:
* 0x01 - Network certificate of membership is attached
* 0x02 - Implicit gather limit field is present
* 0x04 - Source MAC is specified -- otherwise it's computed from sender
*
* OK and ERROR responses are optional. OK may be generated if there are
* implicit gather results or if the recipient wants to send its own
* updated certificate of network membership to the sender. ERROR may be
* generated if a certificate is needed or if multicasts to this group
* are no longer wanted (multicast unsubscribe).
*
* OK response payload:
* <[8] 64-bit network ID>
* <[6] MAC address of multicast group>
* <[4] 32-bit ADI for multicast group>
* <[1] flags>
* [<[...] network certficate of membership>]
* [<[...] implicit gather results if flag 0x01 is set>]
*
* OK flags (same bits as request flags):
* 0x01 - OK includes certificate of network membership
* 0x02 - OK includes implicit gather results
*
* ERROR response payload:
* <[8] 64-bit network ID>
* <[6] multicast group MAC>
* <[4] 32-bit multicast group ADI>
*/
VERB_MULTICAST_FRAME = 14,
/* Ephemeral (PFS) key push:
* <[2] flags (unused and reserved, must be 0)>
* <[2] length of padding / extra field section>
* <[...] padding / extra field section>
* <[8] 64-bit PFS key set ID sender holds for recipient (0==none)>
* <[8] 64-bit PFS key set ID of this key set>
* [... begin PFS key record ...]
* <[1] flags>
* <[1] symmetric cipher ID>
* <[1] public key type ID>
* <[2] public key length in bytes>
* <[...] public key>
* [... additional records may follow up to max packet length ...]
*
* This message is sent to negotiate an ephemeral key. If the recipient's
* current key pair for the sender does not match the one the sender
* claims to have on file, it must respond with its own SET_EPHEMERAL_KEY.
*
* PFS key IDs are random and must not be zero, since zero indicates that
* the sender does not have an ephemeral key on file for the recipient.
*
* One or more records may be sent. If multiple records are present,
* the first record with common symmetric cipher, public key type,
* and relevant flags must be used.
*
* The padding section may be filled with an arbitrary amount of random
* or empty payload. This may be used as a countermeasure to prevent PFS
* key pushes from being recognized by packet size vs. other packets in
* the stream. This also provides potential space for additional fields
* that might be indicated in the future by flags.
*
* Flags (all unspecified flags must be zero):
* 0x01 - FIPS mode, only use record if FIPS compliant crypto in use
*
* Symmetric cipher IDs:
* 0x01 - Salsa20/12 with Poly1305 authentication (ZT default)
* 0x02 - AES256-GCM combined crypto and authentication
*
* Public key types:
* 0x01 - Curve25519 ECDH with SHA-512 KDF
* 0x02 - NIST P-256 ECDH with SHA-512 KDF
*
* Once both peers have a PFS key, they will attempt to send PFS key
* encrypted messages with the PFS flag set using the negotiated
* cipher/auth type.
*
* Note: most of these features such as FIPS and other cipher suites are
* not implemented yet. They're just specified in the protocol for future
* use to support e.g. FIPS requirements.
*
* OK response payload:
* <[8] PFS key set ID of received key set>
* <[1] index in record list of chosen key record>
*/
VERB_SET_EPHEMERAL_KEY = 15,
/* "Call me at" -- push of potential endpoints for direct communication:
* <[1] flags>
* <[2] number of addresses>
* <[...] address types and addresses>
*
* Address types and addresses are of the same format as the destination
* address type and address in HELLO.
*
* The receiver may, upon receiving a CMA push, attempt to establish a
* direct link to one or more of the indicated addresses. Senders should
* only send CMA pushes to peers that they have some relationship
* with such as a shared network membership or a mutual trust.
*
* OK/ERROR are not generated.
*/
VERB_CMA = 16
};
/**
* Error codes for VERB_ERROR
*/
enum ErrorCode
{
/* No error, not actually used in transit */
ERROR_NONE = 0,
/* Invalid request */
ERROR_INVALID_REQUEST = 1,
/* Bad/unsupported protocol version */
ERROR_BAD_PROTOCOL_VERSION = 2,
/* Unknown object queried (e.g. with WHOIS) */
ERROR_OBJ_NOT_FOUND = 3,
/* HELLO pushed an identity whose address is already claimed */
ERROR_IDENTITY_COLLISION = 4,
/* Verb or use case not supported/enabled by this node */
ERROR_UNSUPPORTED_OPERATION = 5,
/* Message to private network rejected -- no unexpired certificate on file */
ERROR_NEED_MEMBERSHIP_CERTIFICATE = 6,
/* Tried to join network, but you're not a member */
ERROR_NETWORK_ACCESS_DENIED_ = 7, /* extra _ to avoid Windows name conflict */
/* Multicasts to this group are not wanted */
ERROR_UNWANTED_MULTICAST = 8
};
/**
* @param v Verb
* @return String representation (e.g. HELLO, OK)
*/
static const char *verbString(Verb v)
throw();
/**
* @param e Error code
* @return String error name
*/
static const char *errorString(ErrorCode e)
throw();
template<unsigned int C2>
Packet(const Buffer<C2> &b) :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(b)
{
}
Packet(const void *data,unsigned int len) :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(data,len)
{
}
/**
* Construct a new empty packet with a unique random packet ID
*
* Flags and hops will be zero. Other fields and data region are undefined.
* Use the header access methods (setDestination() and friends) to fill out
* the header. Payload should be appended; initial size is header size.
*/
Packet() :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(ZT_PROTO_MIN_PACKET_LENGTH)
{
Utils::getSecureRandom(field(ZT_PACKET_IDX_IV,8),8);
(*this)[ZT_PACKET_IDX_FLAGS] = 0; // zero flags, cipher ID, and hops
}
/**
* Make a copy of a packet with a new initialization vector and destination address
*
* This can be used to take one draft prototype packet and quickly make copies to
* encrypt for different destinations.
*
* @param prototype Prototype packet
* @param dest Destination ZeroTier address for new packet
*/
Packet(const Packet &prototype,const Address &dest) :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(prototype)
{
Utils::getSecureRandom(field(ZT_PACKET_IDX_IV,8),8);
setDestination(dest);
}
/**
* Construct a new empty packet with a unique random packet ID
*
* @param dest Destination ZT address
* @param source Source ZT address
* @param v Verb
*/
Packet(const Address &dest,const Address &source,const Verb v) :
Buffer<ZT_PROTO_MAX_PACKET_LENGTH>(ZT_PROTO_MIN_PACKET_LENGTH)
{
Utils::getSecureRandom(field(ZT_PACKET_IDX_IV,8),8);
setDestination(dest);
setSource(source);
(*this)[ZT_PACKET_IDX_FLAGS] = 0; // zero flags and hops
setVerb(v);
}
/**
* Reset this packet structure for reuse in place
*
* @param dest Destination ZT address
* @param source Source ZT address
* @param v Verb
*/
inline void reset(const Address &dest,const Address &source,const Verb v)
{
setSize(ZT_PROTO_MIN_PACKET_LENGTH);
Utils::getSecureRandom(field(ZT_PACKET_IDX_IV,8),8);
setDestination(dest);
setSource(source);
(*this)[ZT_PACKET_IDX_FLAGS] = 0; // zero flags, cipher ID, and hops
setVerb(v);
}
/**
* Generate a new IV / packet ID in place
*
* This can be used to re-use a packet buffer multiple times to send
* technically different but otherwise identical copies of the same
* packet.
*/
inline void newInitializationVector() { Utils::getSecureRandom(field(ZT_PACKET_IDX_IV,8),8); }
/**
* Set this packet's destination
*
* @param dest ZeroTier address of destination
*/
inline void setDestination(const Address &dest) { dest.copyTo(field(ZT_PACKET_IDX_DEST,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH); }
/**
* Set this packet's source
*
* @param source ZeroTier address of source
*/
inline void setSource(const Address &source) { source.copyTo(field(ZT_PACKET_IDX_SOURCE,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH); }
/**
* Get this packet's destination
*
* @return Destination ZT address
*/
inline Address destination() const { return Address(field(ZT_PACKET_IDX_DEST,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH); }
/**
* Get this packet's source
*
* @return Source ZT address
*/
inline Address source() const { return Address(field(ZT_PACKET_IDX_SOURCE,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH); }
/**
* @return True if packet is of valid length
*/
inline bool lengthValid() const { return (size() >= ZT_PROTO_MIN_PACKET_LENGTH); }
/**
* @return True if packet is fragmented (expect fragments)
*/
inline bool fragmented() const { return (((unsigned char)(*this)[ZT_PACKET_IDX_FLAGS] & ZT_PROTO_FLAG_FRAGMENTED) != 0); }
/**
* Set this packet's fragmented flag
*
* @param f Fragmented flag value
*/
inline void setFragmented(bool f)
{
if (f)
(*this)[ZT_PACKET_IDX_FLAGS] |= (char)ZT_PROTO_FLAG_FRAGMENTED;
else (*this)[ZT_PACKET_IDX_FLAGS] &= (char)(~ZT_PROTO_FLAG_FRAGMENTED);
}
/**
* @return True if compressed (result only valid if unencrypted)
*/
inline bool compressed() const { return (((unsigned char)(*this)[ZT_PACKET_IDX_VERB] & ZT_PROTO_VERB_FLAG_COMPRESSED) != 0); }
/**
* @return ZeroTier forwarding hops (0 to 7)
*/
inline unsigned int hops() const { return ((unsigned int)(*this)[ZT_PACKET_IDX_FLAGS] & 0x07); }
/**
* Increment this packet's hop count
*/
inline void incrementHops()
{
unsigned char &b = (*this)[ZT_PACKET_IDX_FLAGS];
b = (b & 0xf8) | ((b + 1) & 0x07);
}
/**
* @return Cipher suite selector: 0 - 7 (see #defines)
*/
inline unsigned int cipher() const
{
// Note: this uses the new cipher spec field, which is incompatible with <1.0.0 peers
return (((unsigned int)(*this)[ZT_PACKET_IDX_FLAGS] & 0x38) >> 3);
}
/**
* Set this packet's cipher suite
*/
inline void setCipher(unsigned int c)
{
unsigned char &b = (*this)[ZT_PACKET_IDX_FLAGS];
b = (b & 0xc7) | (unsigned char)((c << 3) & 0x38); // bits: FFCCCHHH
// DEPRECATED "encrypted" flag -- used by pre-1.0.3 peers
if (c == ZT_PROTO_CIPHER_SUITE__C25519_POLY1305_SALSA2012)
b |= ZT_PROTO_FLAG_ENCRYPTED;
else b &= (~ZT_PROTO_FLAG_ENCRYPTED);
}
/**
* Get this packet's unique ID (the IV field interpreted as uint64_t)
*
* @return Packet ID
*/
inline uint64_t packetId() const { return at<uint64_t>(ZT_PACKET_IDX_IV); }
/**
* Set packet verb
*
* This also has the side-effect of clearing any verb flags, such as
* compressed, and so must only be done during packet composition.
*
* @param v New packet verb
*/
inline void setVerb(Verb v) { (*this)[ZT_PACKET_IDX_VERB] = (char)v; }
/**
* @return Packet verb (not including flag bits)
*/
inline Verb verb() const { return (Verb)((*this)[ZT_PACKET_IDX_VERB] & 0x1f); }
/**
* @return Length of packet payload
*/
inline unsigned int payloadLength() const { return ((size() < ZT_PROTO_MIN_PACKET_LENGTH) ? 0 : (size() - ZT_PROTO_MIN_PACKET_LENGTH)); }
/**
* @return Raw packet payload
*/
inline const unsigned char *payload() const { return field(ZT_PACKET_IDX_PAYLOAD,size() - ZT_PACKET_IDX_PAYLOAD); }
/**
* Armor packet for transport
*
* @param key 32-byte key
* @param encryptPayload If true, encrypt packet payload, else just MAC
*/
void armor(const void *key,bool encryptPayload);
/**
* Verify and (if encrypted) decrypt packet
*
* @param key 32-byte key
* @return False if packet is invalid or failed MAC authenticity check
*/
bool dearmor(const void *key);
/**
* Attempt to compress payload if not already (must be unencrypted)
*
* This requires that the payload at least contain the verb byte already
* set. The compressed flag in the verb is set if compression successfully
* results in a size reduction. If no size reduction occurs, compression
* is not done and the flag is left cleared.
*
* @return True if compression occurred
*/
bool compress();
/**
* Attempt to decompress payload if it is compressed (must be unencrypted)
*
* If payload is compressed, it is decompressed and the compressed verb
* flag is cleared. Otherwise nothing is done and true is returned.
*
* @return True if data is now decompressed and valid, false on error
*/
bool uncompress();
private:
static const unsigned char ZERO_KEY[32];
/**
* Deterministically mangle a 256-bit crypto key based on packet
*
* This uses extra data from the packet to mangle the secret, giving us an
* effective IV that is somewhat more than 64 bits. This is "free" for
* Salsa20 since it has negligible key setup time so using a different
* key each time is fine.
*
* @param in Input key (32 bytes)
* @param out Output buffer (32 bytes)
*/
inline void _salsa20MangleKey(const unsigned char *in,unsigned char *out) const
{
const unsigned char *d = (const unsigned char *)data();
// IV and source/destination addresses. Using the addresses divides the
// key space into two halves-- A->B and B->A (since order will change).
for(unsigned int i=0;i<18;++i) // 8 + (ZT_ADDRESS_LENGTH * 2) == 18
out[i] = in[i] ^ d[i];
// Flags, but with hop count masked off. Hop count is altered by forwarding
// nodes. It's one of the only parts of a packet modifiable by people
// without the key.
out[18] = in[18] ^ (d[ZT_PACKET_IDX_FLAGS] & 0xf8);
// Raw packet size in bytes -- thus each packet size defines a new
// key space.
out[19] = in[19] ^ (unsigned char)(size() & 0xff);
out[20] = in[20] ^ (unsigned char)((size() >> 8) & 0xff); // little endian
// Rest of raw key is used unchanged
for(unsigned int i=21;i<32;++i)
out[i] = in[i];
}
};
} // namespace ZeroTier
#endif
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