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|
/* net_crypto.c
*
* Functions for the core network crypto.
* See also: docs/Crypto.txt
*
* NOTE: This code has to be perfect. We don't mess around with encryption.
*
Copyright (C) 2013 Tox project All Rights Reserved.
This file is part of Tox.
Tox 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.
Tox 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 Tox. If not, see <http://www.gnu.org/licenses/>.
*/
#include "net_crypto.h"
//Our public and secret keys.
uint8_t self_public_key[crypto_box_PUBLICKEYBYTES];
uint8_t self_secret_key[crypto_box_SECRETKEYBYTES];
typedef struct
{
uint8_t public_key[crypto_box_PUBLICKEYBYTES];//the real public key of the peer.
uint8_t recv_nonce[crypto_box_NONCEBYTES];//nonce of recieved packets
uint8_t sent_nonce[crypto_box_NONCEBYTES];//nonce of sent packets.
uint8_t sessionpublic_key[crypto_box_PUBLICKEYBYTES];//our public key for this session.
uint8_t sessionsecret_key[crypto_box_SECRETKEYBYTES];//our private key for this session.
uint8_t peersessionpublic_key[crypto_box_PUBLICKEYBYTES];//The public key of the peer.
uint8_t status;//0 if no connection, 1 we have sent a handshake, 2 if connexion is not confirmed yet
//(we have recieved a hanshake but no empty data packet), 3 if the connection is established.
//4 if the connection is timed out.
uint16_t number; //Lossless_UDP connection number corresponding to this connection.
}Crypto_Connection;
#define MAX_CRYPTO_CONNECTIONS 256
Crypto_Connection crypto_connections[MAX_CRYPTO_CONNECTIONS];
#define MAX_FRIEND_REQUESTS 32
//keeps track of the connection numbers for friends request so we can check later if they were sent
int outbound_friendrequests[MAX_FRIEND_REQUESTS];
#define MAX_INCOMING 64
//keeps track of the connection numbers for friends request so we can check later if they were sent
int incoming_connections[MAX_INCOMING];
//encrypts plain of length length to encrypted of length + 16 using the
//public key(32 bytes) of the reciever and the secret key of the sender and a 24 byte nonce
//return -1 if there was a problem.
//return length of encrypted data if everything was fine.
int encrypt_data(uint8_t * public_key, uint8_t * secret_key, uint8_t * nonce,
uint8_t * plain, uint32_t length, uint8_t * encrypted)
{
if(length - crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES > MAX_DATA_SIZE || length == 0)
{
return -1;
}
uint8_t temp_plain[MAX_DATA_SIZE + crypto_box_ZEROBYTES - crypto_box_BOXZEROBYTES] = {0};
uint8_t temp_encrypted[MAX_DATA_SIZE + crypto_box_ZEROBYTES];
uint8_t zeroes[crypto_box_BOXZEROBYTES] = {0};
memcpy(temp_plain + crypto_box_ZEROBYTES, plain, length);//pad the message with 32 0 bytes.
crypto_box(temp_encrypted, temp_plain, length + crypto_box_ZEROBYTES, nonce, public_key, secret_key);
//if encryption is successful the first crypto_box_BOXZEROBYTES of the message will be zero
if(memcmp(temp_encrypted, zeroes, crypto_box_BOXZEROBYTES) != 0)
{
return -1;
}
//unpad the encrypted message
memcpy(encrypted, temp_encrypted + crypto_box_BOXZEROBYTES, length - crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES);
return length - crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES;
}
//decrypts encrypted of length length to plain of length length - 16 using the
//public key(32 bytes) of the sender, the secret key of the reciever and a 24 byte nonce
//return -1 if there was a problem(decryption failed)
//return length of plain data if everything was fine.
int decrypt_data(uint8_t * public_key, uint8_t * secret_key, uint8_t * nonce,
uint8_t * encrypted, uint32_t length, uint8_t * plain)
{
if(length > MAX_DATA_SIZE || length <= crypto_box_BOXZEROBYTES)
{
return -1;
}
uint8_t temp_plain[MAX_DATA_SIZE - crypto_box_ZEROBYTES + crypto_box_BOXZEROBYTES];
uint8_t temp_encrypted[MAX_DATA_SIZE + crypto_box_ZEROBYTES] = {0};
uint8_t zeroes[crypto_box_ZEROBYTES] = {0};
memcpy(temp_encrypted + crypto_box_BOXZEROBYTES, encrypted, length);//pad the message with 16 0 bytes.
if(crypto_box_open(temp_plain, temp_encrypted, length + crypto_box_BOXZEROBYTES,
nonce, public_key, secret_key) == -1)
{
return -1;
}
//if decryption is successful the first crypto_box_ZEROBYTES of the message will be zero
if(memcmp(temp_plain, zeroes, crypto_box_ZEROBYTES) != 0)
{
return -1;
}
//unpad the plain message
memcpy(plain, temp_plain + crypto_box_ZEROBYTES, length - crypto_box_ZEROBYTES + crypto_box_BOXZEROBYTES);
return length - crypto_box_ZEROBYTES + crypto_box_BOXZEROBYTES;
}
//increment the given nonce by 1
void increment_nonce(uint8_t * nonce)
{
uint32_t i;
for(i = 0; i < crypto_box_NONCEBYTES; i++)
{
nonce[i]++;
if(nonce[i] != 0)
{
break;
}
}
}
//fill the given nonce with random bytes.
//TODO: make this more optimized
void random_nonce(uint8_t * nonce)
{
uint32_t i;
for(i = 0; i < crypto_box_NONCEBYTES; i++)
{
nonce[i] = random_int() % 256;
}
}
//return 0 if there is no received data in the buffer
//return -1 if the packet was discarded.
//return length of recieved data if successful
int read_cryptpacket(int crypt_connection_id, uint8_t * data)
{
if(crypto_connections[crypt_connection_id].status != 3)
{
return 0;
}
uint8_t temp_data[MAX_DATA_SIZE];
int length = read_packet(crypto_connections[crypt_connection_id].number, temp_data);
if(length == 0)
{
return 0;
}
if(temp_data[0] != 3)
{
return -1;
}
int len = decrypt_data(crypto_connections[crypt_connection_id].peersessionpublic_key,
crypto_connections[crypt_connection_id].sessionsecret_key,
crypto_connections[crypt_connection_id].recv_nonce, temp_data + 1, length - 1, data);
if(len != -1)
{
increment_nonce(crypto_connections[crypt_connection_id].recv_nonce);
return len;
}
return -1;
}
//return 0 if data could not be put in packet queue
//return 1 if data was put into the queue
int write_cryptpacket(int crypt_connection_id, uint8_t * data, uint32_t length)
{
if(length - crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES > MAX_DATA_SIZE - 1)
{
return 0;
}
if(crypto_connections[crypt_connection_id].status != 3)
{
return 0;
}
uint8_t temp_data[MAX_DATA_SIZE];
int len = encrypt_data(crypto_connections[crypt_connection_id].peersessionpublic_key,
crypto_connections[crypt_connection_id].sessionsecret_key,
crypto_connections[crypt_connection_id].sent_nonce, data, length, temp_data + 1);
if(len == -1)
{
return 0;
}
temp_data[0] = 3;
if(write_packet(crypto_connections[crypt_connection_id].number, temp_data, len + 1) == 0)
{
return 0;
}
increment_nonce(crypto_connections[crypt_connection_id].sent_nonce);
return 1;
}
//send a friend request to peer with public_key and ip_port.
//Data represents the data we send with the friends request.
//returns -1 on failure
//returns a positive friend request id that can be used later to see if it was sent correctly on success.
int send_friendrequest(uint8_t * public_key, IP_Port ip_port, uint8_t * data, uint32_t length)
{
if(length > MAX_DATA_SIZE - 1 - crypto_box_PUBLICKEYBYTES - crypto_box_NONCEBYTES)
{
return -1;
}
uint32_t i;
for(i = 0; i < MAX_FRIEND_REQUESTS; i++)
{
if(outbound_friendrequests[i] == -1)
{
break;
}
}
if(i == MAX_FRIEND_REQUESTS)
{
return -1;
}
uint8_t temp_data[MAX_DATA_SIZE];
uint8_t nonce[crypto_box_NONCEBYTES];
random_nonce(nonce);
int len = encrypt_data(public_key, self_secret_key, nonce, data, length,
1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES + temp_data);
if(len == -1)
{
return -1;
}
temp_data[0] = 1;
memcpy(temp_data + 1, self_public_key, crypto_box_PUBLICKEYBYTES);
memcpy(temp_data + 1 + crypto_box_PUBLICKEYBYTES, nonce, crypto_box_NONCEBYTES);
int id = new_connection(ip_port);
if(id == -1)
{
return -1;
}
if(write_packet(id, temp_data, len + 1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES) == 1)
{
outbound_friendrequests[i] = id;
return i;
}
return -1;
}
//return -1 if failure
//return 0 if connection is still trying to send the request.
//return 1 if sent correctly
//return 2 if connection timed out
int check_friendrequest(int friend_request)
{
if(friend_request < 0 || friend_request > MAX_FRIEND_REQUESTS)
{
return -1;
}
if(outbound_friendrequests[friend_request] == -1)
{
return -1;
}
if(sendqueue(outbound_friendrequests[friend_request]) == 0)
{
kill_connection(outbound_friendrequests[friend_request]);
outbound_friendrequests[friend_request] = -1;
return 1;
}
int status = is_connected(outbound_friendrequests[friend_request]);
if(status == 4)
{
kill_connection(outbound_friendrequests[friend_request]);
outbound_friendrequests[friend_request] = -1;
return 2;
}
if(status == 0)
{
outbound_friendrequests[friend_request] = -1;
return 2;
}
return 0;
}
//Send a crypto handshake packet containing an encrypted secret nonce and session public key
//to peer with connection_id and public_key
//the packet is encrypted with a random nonce which is sent in plain text with the packet
int send_cryptohandshake(int connection_id, uint8_t * public_key, uint8_t * secret_nonce, uint8_t * session_key)
{
uint8_t temp_data[MAX_DATA_SIZE];
uint8_t temp[crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES];
uint8_t nonce[crypto_box_NONCEBYTES];
random_nonce(nonce);
memcpy(temp, secret_nonce, crypto_box_NONCEBYTES);
memcpy(temp + crypto_box_NONCEBYTES, session_key, crypto_box_PUBLICKEYBYTES);
int len = encrypt_data(public_key, self_secret_key, nonce, temp, crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES,
1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES + temp_data);
if(len == -1)
{
return 0;
}
temp_data[0] = 2;
memcpy(temp_data + 1, self_public_key, crypto_box_PUBLICKEYBYTES);
memcpy(temp_data + 1 + crypto_box_PUBLICKEYBYTES, nonce, crypto_box_NONCEBYTES);
return write_packet(connection_id, temp_data, len + 1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES);
}
//Extract secret nonce, session public key and public_key from a packet(data) with length length
//return 1 if successful
//return 0 if failure
int handle_cryptohandshake(uint8_t * public_key, uint8_t * secret_nonce,
uint8_t * session_key, uint8_t * data, uint16_t length)
{
int pad = (- crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES);
if(length != 1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES
+ crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES + pad)
{
return 0;
}
if(data[0] != 2)
{
return 0;
}
uint8_t temp[crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES];
memcpy(public_key, data + 1, crypto_box_PUBLICKEYBYTES);
int len = decrypt_data(public_key, self_secret_key, data + 1 + crypto_box_PUBLICKEYBYTES,
data + 1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES,
crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES + pad, temp);
if(len != crypto_box_NONCEBYTES + crypto_box_PUBLICKEYBYTES)
{
return 0;
}
memcpy(secret_nonce, temp, crypto_box_NONCEBYTES);
memcpy(session_key, temp + crypto_box_NONCEBYTES, crypto_box_PUBLICKEYBYTES);
return 1;
}
//puts the public key of the friend if public_key, the data from the request
//in data if a friend request was sent to us and returns the length of the data.
//return -1 if no valid friend requests.
int handle_friendrequest(uint8_t * public_key, uint8_t * data)
{
uint32_t i;
for(i = 0; i < MAX_INCOMING; i++)
{
if(incoming_connections[i] != -1)
{
if(id_packet(incoming_connections[i]) == 1)
{
uint8_t temp_data[MAX_DATA_SIZE];
uint16_t len = read_packet(incoming_connections[i], temp_data);
if(len > crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES + 1
- crypto_box_BOXZEROBYTES + crypto_box_ZEROBYTES)
{
memcpy(public_key, temp_data + 1, crypto_box_PUBLICKEYBYTES);
uint8_t nonce[crypto_box_NONCEBYTES];
memcpy(nonce, temp_data + 1 + crypto_box_PUBLICKEYBYTES, crypto_box_NONCEBYTES);
int len1 = decrypt_data(public_key, self_secret_key, nonce, temp_data + 1 + crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES,
len - (crypto_box_PUBLICKEYBYTES + crypto_box_NONCEBYTES + 1), data);
if(len1 != -1)
{
kill_connection_in(incoming_connections[i], 1); //conection is useless now, kill it in 1 seconds
incoming_connections[i] = -1;
return len1;
}
}
kill_connection(incoming_connections[i]); //conection is useless now, kill it.
incoming_connections[i] = -1;
}
}
}
return -1;
}
//Start a secure connection with other peer who has public_key and ip_port
//returns -1 if failure
//returns crypt_connection_id of the initialized connection if everything went well.
int crypto_connect(uint8_t * public_key, IP_Port ip_port)
{
uint32_t i;
if(getconnection_id(ip_port) != -1)
{
return -1;
}
for(i = 0; i < MAX_CRYPTO_CONNECTIONS; i++)
{
if(crypto_connections[i].status == 0)
{
int id = new_connection(ip_port);
if(id == -1)
{
return -1;
}
crypto_connections[i].number = id;
crypto_connections[i].status = 1;
random_nonce(crypto_connections[i].recv_nonce);
memcpy(crypto_connections[i].public_key, public_key, crypto_box_PUBLICKEYBYTES);
crypto_box_keypair(crypto_connections[i].sessionpublic_key, crypto_connections[i].sessionsecret_key);
if(send_cryptohandshake(id, public_key, crypto_connections[i].recv_nonce,
crypto_connections[i].sessionpublic_key) == 1)
{
increment_nonce(crypto_connections[i].recv_nonce);
return i;
}
return -1;//this should never happen.
}
}
return -1;
}
//handle an incoming connection
//return -1 if no crypto inbound connection
//return incomming connection id (Lossless_UDP one) if there is an incomming crypto connection
//Put the public key of the peer in public_key, the secret_nonce from the handshake into secret_nonce
//and the session public key for the connection in session_key
//to accept it see: accept_crypto_inbound(...)
//to refuse it just call kill_connection(...) on the connection id
int crypto_inbound(uint8_t * public_key, uint8_t * secret_nonce, uint8_t * session_key)
{
uint32_t i;
for(i = 0; i < MAX_INCOMING; i++)
{
if(incoming_connections[i] != -1)
{
if(id_packet(incoming_connections[i]) == 2)
{
uint8_t temp_data[MAX_DATA_SIZE];
uint16_t len = read_packet(incoming_connections[i], temp_data);
if(handle_cryptohandshake(public_key, secret_nonce, session_key, temp_data, len))
{
int connection_id = incoming_connections[i];
incoming_connections[i] = -1;//remove this connection from the incoming connection list.
return connection_id;
}
}
}
}
return -1;
}
//kill a crypto connection
//return 0 if killed successfully
//return 1 if there was a problem.
int crypto_kill(int crypt_connection_id)
{
if(crypt_connection_id < 0 || crypt_connection_id >= MAX_CRYPTO_CONNECTIONS)
{
return 1;
}
if(crypto_connections[crypt_connection_id].status != 0)
{
crypto_connections[crypt_connection_id].status = 0;
kill_connection(crypto_connections[crypt_connection_id].number);
return 0;
}
return 1;
}
//accept an incoming connection using the parameters provided by crypto_inbound
//return -1 if not successful
//returns the crypt_connection_id if successful
int accept_crypto_inbound(int connection_id, uint8_t * public_key, uint8_t * secret_nonce, uint8_t * session_key)
{
uint32_t i;
if(connection_id == -1)
{
return -1;
}
for(i = 0; i < MAX_CRYPTO_CONNECTIONS; i++)
{
if(crypto_connections[i].status == 0)
{
crypto_connections[i].number = connection_id;
crypto_connections[i].status = 2;
random_nonce(crypto_connections[i].recv_nonce);
memcpy(crypto_connections[i].sent_nonce, secret_nonce, crypto_box_NONCEBYTES);
memcpy(crypto_connections[i].peersessionpublic_key, session_key, crypto_box_PUBLICKEYBYTES);
increment_nonce(crypto_connections[i].sent_nonce);
memcpy(crypto_connections[i].public_key, public_key, crypto_box_PUBLICKEYBYTES);
crypto_box_keypair(crypto_connections[i].sessionpublic_key, crypto_connections[i].sessionsecret_key);
if(send_cryptohandshake(connection_id, public_key, crypto_connections[i].recv_nonce,
crypto_connections[i].sessionpublic_key) == 1)
{
increment_nonce(crypto_connections[i].recv_nonce);
uint32_t zero = 0;
crypto_connections[i].status = 3;//connection status needs to be 3 for write_cryptpacket() to work
write_cryptpacket(i, ((uint8_t *)&zero), sizeof(zero));
crypto_connections[i].status = 2;//set it to its proper value right after.
return i;
}
return -1;//this should never happen.
}
}
return -1;
}
//return 0 if no connection, 1 we have sent a handshake, 2 if connexion is not confirmed yet
//(we have recieved a hanshake but no empty data packet), 3 if the connection is established.
//4 if the connection is timed out and wating to be killed
int is_cryptoconnected(int crypt_connection_id)
{
if(crypt_connection_id >= 0 && crypt_connection_id < MAX_CRYPTO_CONNECTIONS)
{
return crypto_connections[crypt_connection_id].status;
}
return 0;
}
//Generate our public and private keys
//Only call this function the first time the program starts.
void new_keys()
{
crypto_box_keypair(self_public_key,self_secret_key);
}
//TODO: optimize this
//adds an incoming connection to the incoming_connection list.
//returns 0 if successful
//returns 1 if failure
int new_incoming(int id)
{
uint32_t i;
for(i = 0; i < MAX_INCOMING; i++)
{
if(incoming_connections[i] == -1)
{
incoming_connections[i] = id;
return 0;
}
}
return 1;
}
//TODO: optimize this
//handle all new incoming connections.
void handle_incomings()
{
int income;
while(1)
{
income = incoming_connection();
if(income == -1)
{
break;
}
if(new_incoming(income))
{
break;
}
}
}
//handle recieved packets for not yet established crypto connections.
void recieve_crypto()
{
uint32_t i;
for(i = 0; i < MAX_CRYPTO_CONNECTIONS; i++)
{
if(crypto_connections[i].status == 1)
{
if(id_packet(crypto_connections[i].number) == 2)//handle handshake packet.
{
uint8_t temp_data[MAX_DATA_SIZE];
uint8_t secret_nonce[crypto_box_NONCEBYTES];
uint8_t public_key[crypto_box_PUBLICKEYBYTES];
uint8_t session_key[crypto_box_PUBLICKEYBYTES];
uint16_t len = read_packet(crypto_connections[i].number, temp_data);
if(handle_cryptohandshake(public_key, secret_nonce, session_key, temp_data, len))
{
if(memcmp(public_key, crypto_connections[i].public_key, crypto_box_PUBLICKEYBYTES) == 0)
{
memcpy(crypto_connections[i].sent_nonce, secret_nonce, crypto_box_NONCEBYTES);
memcpy(crypto_connections[i].peersessionpublic_key, session_key, crypto_box_PUBLICKEYBYTES);
increment_nonce(crypto_connections[i].sent_nonce);
uint32_t zero = 0;
crypto_connections[i].status = 3;//connection status needs to be 3 for write_cryptpacket() to work
write_cryptpacket(i, ((uint8_t *)&zero), sizeof(zero));
crypto_connections[i].status = 2;//set it to its proper value right after.
}
}
}
else if(id_packet(crypto_connections[i].number) != -1)
{
//This should not happen
//kill the connection if it does
crypto_kill(crypto_connections[i].number);
}
}
if(crypto_connections[i].status == 2)
{
if(id_packet(crypto_connections[i].number) == 3)
{
uint8_t temp_data[MAX_DATA_SIZE];
uint8_t data[MAX_DATA_SIZE];
int length = read_packet(crypto_connections[i].number, temp_data);
int len = decrypt_data(crypto_connections[i].peersessionpublic_key,
crypto_connections[i].sessionsecret_key,
crypto_connections[i].recv_nonce, temp_data + 1, length - 1, data);
uint32_t zero = 0;
if(len == sizeof(uint32_t) && memcmp(((uint8_t *)&zero), data, sizeof(uint32_t)) == 0)
{
increment_nonce(crypto_connections[i].recv_nonce);
crypto_connections[i].status = 3;
}
else
{
//This should not happen
//kill the connection if it does
crypto_kill(crypto_connections[i].number);
}
}
else if(id_packet(crypto_connections[i].number) != -1)
{
//This should not happen
//kill the connection if it does
crypto_kill(crypto_connections[i].number);
}
}
}
}
//run this to (re)initialize net_crypto
//sets all the global connection variables to their default values.
void initNetCrypto()
{
memset(crypto_connections, 0 ,sizeof(crypto_connections));
memset(outbound_friendrequests, -1 ,sizeof(outbound_friendrequests));
memset(incoming_connections, -1 ,sizeof(incoming_connections));
}
void killTimedout()
{
uint32_t i;
for(i = 0; i < MAX_CRYPTO_CONNECTIONS; i++)
{
if(is_connected(crypto_connections[i].number) == 4)
{
crypto_connections[i].status = 4;
}
}
}
//main loop
void doNetCrypto()
{
//TODO:check if friend requests were sent correctly
//handle new incoming connections
//handle friend requests
handle_incomings();
recieve_crypto();
killTimedout();
}
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