/*
* ZeroTier One - Network Virtualization Everywhere
* Copyright (C) 2011-2019 ZeroTier, Inc. https://www.zerotier.com/
*
* 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 .
*
* --
*
* You can be released from the requirements of the license by purchasing
* a commercial license. Buying such a license is mandatory as soon as you
* develop commercial closed-source software that incorporates or links
* directly against ZeroTier software without disclosing the source code
* of your own application.
*/
#ifndef ZT_C25519_HPP
#define ZT_C25519_HPP
#include "Utils.hpp"
namespace ZeroTier {
#define ZT_C25519_PUBLIC_KEY_LEN 64
#define ZT_C25519_PRIVATE_KEY_LEN 64
#define ZT_C25519_SIGNATURE_LEN 96
/**
* A combined Curve25519 ECDH and Ed25519 signature engine
*/
class C25519
{
public:
struct Public { uint8_t data[ZT_C25519_PUBLIC_KEY_LEN]; };
struct Private { uint8_t data[ZT_C25519_PRIVATE_KEY_LEN]; };
struct Signature { uint8_t data[ZT_C25519_SIGNATURE_LEN]; };
struct Pair { Public pub; Private priv; };
/**
* Generate a C25519 elliptic curve key pair
*/
static inline Pair generate()
{
Pair kp;
Utils::getSecureRandom(kp.priv.data,ZT_C25519_PRIVATE_KEY_LEN);
_calcPubDH(kp);
_calcPubED(kp);
return kp;
}
/**
* Generate a key pair satisfying a condition
*
* This begins with a random keypair from a random secret key and then
* iteratively increments the random secret until cond(kp) returns true.
* This is used to compute key pairs in which the public key, its hash
* or some other aspect of it satisfies some condition, such as for a
* hashcash criteria.
*
* @param cond Condition function or function object
* @return Key pair where cond(kp) returns true
* @tparam F Type of 'cond'
*/
template
static inline Pair generateSatisfying(F cond)
{
Pair kp;
void *const priv = (void *)kp.priv.data;
Utils::getSecureRandom(priv,ZT_C25519_PRIVATE_KEY_LEN);
_calcPubED(kp); // do Ed25519 key -- bytes 32-63 of pub and priv
do {
++(((uint64_t *)priv)[1]);
--(((uint64_t *)priv)[2]);
_calcPubDH(kp); // keep regenerating bytes 0-31 until satisfied
} while (!cond(kp));
return kp;
}
/**
* Perform C25519 ECC key agreement
*
* Actual key bytes are generated from one or more SHA-512 digests of
* the raw result of key agreement.
*
* @param mine My private key
* @param their Their public key
* @param keybuf Buffer to fill
* @param keylen Number of key bytes to generate
*/
static void agree(const Private &mine,const Public &their,void *keybuf,unsigned int keylen);
static inline void agree(const Pair &mine,const Public &their,void *keybuf,unsigned int keylen) { agree(mine.priv,their,keybuf,keylen); }
/**
* Sign a message with a sender's key pair
*
* This takes the SHA-521 of msg[] and then signs the first 32 bytes of this
* digest, returning it and the 64-byte ed25519 signature in signature[].
* This results in a signature that verifies both the signer's authenticity
* and the integrity of the message.
*
* This is based on the original ed25519 code from NaCl and the SUPERCOP
* cipher benchmark suite, but with the modification that it always
* produces a signature of fixed 96-byte length based on the hash of an
* arbitrary-length message.
*
* @param myPrivate My private key
* @param myPublic My public key
* @param msg Message to sign
* @param len Length of message in bytes
* @param signature Buffer to fill with signature -- MUST be 96 bytes in length
*/
static void sign(const Private &myPrivate,const Public &myPublic,const void *msg,unsigned int len,void *signature);
static inline void sign(const Pair &mine,const void *msg,unsigned int len,void *signature) { sign(mine.priv,mine.pub,msg,len,signature); }
/**
* Sign a message with a sender's key pair
*
* @param myPrivate My private key
* @param myPublic My public key
* @param msg Message to sign
* @param len Length of message in bytes
* @return Signature
*/
static inline Signature sign(const Private &myPrivate,const Public &myPublic,const void *msg,unsigned int len)
{
Signature sig;
sign(myPrivate,myPublic,msg,len,sig.data);
return sig;
}
static inline Signature sign(const Pair &mine,const void *msg,unsigned int len)
{
Signature sig;
sign(mine.priv,mine.pub,msg,len,sig.data);
return sig;
}
/**
* Verify a message's signature
*
* @param their Public key to verify against
* @param msg Message to verify signature integrity against
* @param len Length of message in bytes
* @param signature 96-byte signature
* @return True if signature is valid and the message is authentic and unmodified
*/
static bool verify(const Public &their,const void *msg,unsigned int len,const void *signature);
/**
* Verify a message's signature
*
* @param their Public key to verify against
* @param msg Message to verify signature integrity against
* @param len Length of message in bytes
* @param signature 96-byte signature
* @return True if signature is valid and the message is authentic and unmodified
*/
static inline bool verify(const Public &their,const void *msg,unsigned int len,const Signature &signature)
{
return verify(their,msg,len,signature.data);
}
private:
// derive first 32 bytes of kp.pub from first 32 bytes of kp.priv
// this is the ECDH key
static void _calcPubDH(Pair &kp);
// derive 2nd 32 bytes of kp.pub from 2nd 32 bytes of kp.priv
// this is the Ed25519 sign/verify key
static void _calcPubED(Pair &kp);
};
} // namespace ZeroTier
#endif