transmission/libtransmission/crypto.c

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/*
* This file Copyright (C) 2007 Charles Kerr <charles@rebelbase.com>
*
* This file is licensed by the GPL version 2. Works owned by the
* Transmission project are granted a special exemption to clause 2(b)
* so that the bulk of its code can remain under the MIT license.
* This exemption does not extend to derived works not owned by
* the Transmission project.
*
* $Id$
*/
#include <assert.h>
#include <inttypes.h> /* uint8_t */
#include <string.h> /* memcpy */
#include <stdarg.h>
#include <arpa/inet.h>
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/rc4.h>
#include <openssl/sha.h>
#include <event.h>
#include "crypto.h"
#include "utils.h"
/**
***
**/
void
tr_sha1( uint8_t * setme,
const void * content1,
int content1_len,
... )
{
va_list vl;
SHA_CTX sha;
SHA1_Init( &sha );
SHA1_Update( &sha, content1, content1_len );
va_start( vl, content1_len );
for( ;; ) {
const void * content = (const void*) va_arg( vl, const void* );
const int content_len = content ? (int) va_arg( vl, int ) : -1;
if( content==NULL || content_len<1 )
break;
SHA1_Update( &sha, content, content_len );
}
SHA1_Final( setme, &sha );
}
/**
***
**/
#define KEY_LEN 96
#define PRIME_LEN 96
static const uint8_t dh_P[PRIME_LEN] =
{
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
0xA6, 0x3A, 0x36, 0x21, 0x00, 0x00, 0x00, 0x00, 0x00, 0x09, 0x05, 0x63,
};
static const uint8_t dh_G[] = { 2 };
struct tr_crypto
{
RC4_KEY dec_key;
RC4_KEY enc_key;
uint8_t torrentHash[SHA_DIGEST_LENGTH];
unsigned int isIncoming : 1;
unsigned int torrentHashIsSet : 1;
unsigned int mySecretIsSet : 1;
uint8_t myPublicKey[KEY_LEN];
uint8_t mySecret[KEY_LEN];
};
/**
***
**/
static DH*
getSharedDH( void )
{
static DH * dh = NULL;
if( dh == NULL )
{
dh = DH_new( );
dh->p = BN_bin2bn( dh_P, sizeof(dh_P), NULL );
dh->g = BN_bin2bn( dh_G, sizeof(dh_G), NULL );
DH_generate_key( dh );
}
return dh;
}
tr_crypto *
tr_cryptoNew( const uint8_t * torrentHash,
int isIncoming )
{
int len, offset;
tr_crypto * crypto;
DH * dh = getSharedDH( );
crypto = tr_new0( tr_crypto, 1 );
crypto->isIncoming = isIncoming ? 1 : 0;
tr_cryptoSetTorrentHash( crypto, torrentHash );
/* DH can generate key sizes that are smaller than the size of
P with exponentially decreasing probability, in which case
the msb's of myPublicKey need to be zeroed appropriately. */
len = DH_size( dh );
offset = KEY_LEN - len;
assert( len <= KEY_LEN );
memset( crypto->myPublicKey, 0, offset );
BN_bn2bin( dh->pub_key, crypto->myPublicKey + offset );
return crypto;
}
void
tr_cryptoFree( tr_crypto * crypto )
{
tr_free( crypto );
}
/**
***
**/
const uint8_t*
tr_cryptoComputeSecret( tr_crypto * crypto,
const uint8_t * peerPublicKey )
{
int len, offset;
uint8_t secret[KEY_LEN];
BIGNUM * bn = BN_bin2bn( peerPublicKey, KEY_LEN, NULL );
DH * dh = getSharedDH( );
assert( DH_size(dh) == KEY_LEN );
len = DH_compute_key( secret, bn, dh );
assert( len <= KEY_LEN );
offset = KEY_LEN - len;
memset( crypto->mySecret, 0, offset );
memcpy( crypto->mySecret + offset, secret, len );
crypto->mySecretIsSet = 1;
BN_free( bn );
return crypto->mySecret;
}
const uint8_t*
tr_cryptoGetMyPublicKey( const tr_crypto * crypto, int * setme_len )
{
*setme_len = KEY_LEN;
return crypto->myPublicKey;
}
/**
***
**/
static void
initRC4( tr_crypto * crypto, RC4_KEY * setme, const char * key )
{
SHA_CTX sha;
uint8_t buf[SHA_DIGEST_LENGTH];
assert( crypto->torrentHashIsSet );
assert( crypto->mySecretIsSet );
SHA1_Init( &sha );
SHA1_Update( &sha, key, 4 );
SHA1_Update( &sha, crypto->mySecret, KEY_LEN );
SHA1_Update( &sha, crypto->torrentHash, SHA_DIGEST_LENGTH );
SHA1_Final( buf, &sha );
RC4_set_key( setme, SHA_DIGEST_LENGTH, buf );
}
void
tr_cryptoDecryptInit( tr_crypto * crypto )
{
unsigned char discard[1024];
const char * txt = crypto->isIncoming ? "keyA" : "keyB";
initRC4( crypto, &crypto->dec_key, txt );
RC4( &crypto->dec_key, sizeof(discard), discard, discard );
}
void
tr_cryptoDecrypt( tr_crypto * crypto,
size_t buf_len,
const void * buf_in,
void * buf_out )
{
RC4( &crypto->dec_key, buf_len,
(const unsigned char*)buf_in,
(unsigned char*)buf_out );
}
void
tr_cryptoEncryptInit( tr_crypto * crypto )
{
unsigned char discard[1024];
const char * txt = crypto->isIncoming ? "keyB" : "keyA";
initRC4( crypto, &crypto->enc_key, txt );
RC4( &crypto->enc_key, sizeof(discard), discard, discard );
}
void
tr_cryptoEncrypt( tr_crypto * crypto,
size_t buf_len,
const void * buf_in,
void * buf_out )
{
RC4( &crypto->enc_key, buf_len,
(const unsigned char*)buf_in,
(unsigned char*)buf_out );
}
/**
***
**/
void
tr_cryptoSetTorrentHash( tr_crypto * crypto,
const uint8_t * hash )
{
crypto->torrentHashIsSet = hash ? 1 : 0;
if( hash != NULL )
memcpy( crypto->torrentHash, hash, SHA_DIGEST_LENGTH );
else
memset( crypto->torrentHash, 0, SHA_DIGEST_LENGTH );
}
const uint8_t*
tr_cryptoGetTorrentHash( const tr_crypto * crypto )
{
assert( crypto != NULL );
assert( crypto->torrentHashIsSet );
return crypto->torrentHash;
}
int
tr_cryptoHasTorrentHash( const tr_crypto * crypto )
{
assert( crypto != NULL );
return crypto->torrentHashIsSet ? 1 : 0;
}