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transmission/libtransmission/crypto.c

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/* * This file Copyright (C) 2007-2010 Mnemosyne LLC
*
* 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 <limits.h> /* for INT_MAX */
#include <stdarg.h>
#include <stdlib.h> /* for abs() */
#include <string.h> /* memcpy */
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/err.h>
#include <openssl/rc4.h>
#include <openssl/sha.h>
#include <openssl/rand.h>
#include "transmission.h"
#include "crypto.h"
#include "utils.h"
#define MY_NAME "tr_crypto"
/**
***
**/
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 );
}
va_end( vl );
SHA1_Final( setme, &sha );
}
/**
***
**/
#define KEY_LEN 96
#define PRIME_LEN 96
#define DH_PRIVKEY_LEN_MIN 16
#define DH_PRIVKEY_LEN 20
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 };
/** @brief Holds state information for encrypted peer communications */
struct tr_crypto
{
RC4_KEY dec_key;
RC4_KEY enc_key;
uint8_t torrentHash[SHA_DIGEST_LENGTH];
tr_bool isIncoming;
tr_bool torrentHashIsSet;
tr_bool mySecretIsSet;
uint8_t myPublicKey[KEY_LEN];
uint8_t mySecret[KEY_LEN];
DH * dh;
};
/**
***
**/
#define logErrorFromSSL( ... ) \
do { \
if( tr_msgLoggingIsActive( TR_MSG_ERR ) ) { \
char buf[512]; \
ERR_error_string_n( ERR_get_error( ), buf, sizeof( buf ) ); \
tr_msg( __FILE__, __LINE__, TR_MSG_ERR, MY_NAME, "%s", buf ); \
} \
} while( 0 )
static void
ensureKeyExists( tr_crypto * crypto)
{
if( crypto->dh == NULL )
{
int len, offset;
DH * dh = DH_new( );
dh->p = BN_bin2bn( dh_P, sizeof( dh_P ), NULL );
if( dh->p == NULL )
logErrorFromSSL( );
dh->g = BN_bin2bn( dh_G, sizeof( dh_G ), NULL );
if( dh->g == NULL )
logErrorFromSSL( );
/* private DH value: strong random BN of DH_PRIVKEY_LEN*8 bits */
dh->priv_key = BN_new( );
do {
if( BN_rand( dh->priv_key, DH_PRIVKEY_LEN * 8, -1, 0 ) != 1 )
logErrorFromSSL( );
} while ( BN_num_bits( dh->priv_key ) < DH_PRIVKEY_LEN_MIN * 8 );
if( !DH_generate_key( dh ) )
logErrorFromSSL( );
/* 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 = BN_num_bytes( dh->pub_key );
offset = KEY_LEN - len;
assert( len <= KEY_LEN );
memset( crypto->myPublicKey, 0, offset );
BN_bn2bin( dh->pub_key, crypto->myPublicKey + offset );
crypto->dh = dh;
}
}
tr_crypto *
tr_cryptoNew( const uint8_t * torrentHash,
int isIncoming )
{
tr_crypto * crypto;
crypto = tr_new0( tr_crypto, 1 );
crypto->isIncoming = isIncoming ? 1 : 0;
tr_cryptoSetTorrentHash( crypto, torrentHash );
crypto->dh = NULL;
return crypto;
}
void
tr_cryptoFree( tr_crypto * crypto )
{
if( crypto->dh != NULL )
DH_free( crypto->dh );
tr_free( crypto );
}
/**
***
**/
const uint8_t*
tr_cryptoComputeSecret( tr_crypto * crypto,
const uint8_t * peerPublicKey )
{
int len;
uint8_t secret[KEY_LEN];
BIGNUM * bn = BN_bin2bn( peerPublicKey, KEY_LEN, NULL );
DH * dh;
ensureKeyExists( crypto );
dh = crypto->dh;
assert( DH_size( dh ) == KEY_LEN );
len = DH_compute_key( secret, bn, dh );
if( len == -1 )
logErrorFromSSL( );
else {
int offset;
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 )
{
ensureKeyExists( (tr_crypto *) crypto );
*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 );
if( 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 );
}
else
{
logErrorFromSSL( );
}
}
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 )
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 );
assert( crypto->torrentHashIsSet );
return crypto->torrentHash;
}
int
tr_cryptoHasTorrentHash( const tr_crypto * crypto )
{
assert( crypto );
return crypto->torrentHashIsSet ? 1 : 0;
}
int
tr_cryptoRandInt( int upperBound )
{
int noise;
int val;
assert( upperBound > 0 );
if( RAND_pseudo_bytes ( (unsigned char *) &noise, sizeof noise ) >= 0 )
{
val = abs( noise ) % upperBound;
}
else /* fall back to a weaker implementation... */
{
val = tr_cryptoWeakRandInt( upperBound );
}
return val;
}
int
tr_cryptoWeakRandInt( int upperBound )
{
static tr_bool init = FALSE;
assert( upperBound > 0 );
if( !init )
{
srand( tr_date( ) );
init = TRUE;
}
return rand( ) % upperBound;
}
void
tr_cryptoRandBuf( void * buf, size_t len )
{
if( RAND_pseudo_bytes ( (unsigned char*)buf, len ) != 1 )
logErrorFromSSL( );
}
/***
****
***/
char*
tr_ssha1( const void * plaintext )
{
static const char * salter = "0123456789"
"abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"./";
const size_t salter_len = 64;
const size_t saltval_len = 8;
size_t i;
char salt[saltval_len];
uint8_t sha[SHA_DIGEST_LENGTH];
char buf[2*SHA_DIGEST_LENGTH + saltval_len + 2];
for( i=0; i<saltval_len; ++i )
salt[i] = salter[ tr_cryptoRandInt( salter_len ) ];
tr_sha1( sha, plaintext, strlen( plaintext ), salt, saltval_len, NULL );
tr_sha1_to_hex( &buf[1], sha );
memcpy( &buf[1+2*SHA_DIGEST_LENGTH], &salt, saltval_len );
buf[1+2*SHA_DIGEST_LENGTH + saltval_len] = '\0';
buf[0] = '{'; /* signal that this is a hash. this makes saving/restoring
easier */
return tr_strdup( &buf );
}
tr_bool
tr_ssha1_matches( const char * source, const char * pass )
{
char * salt;
size_t saltlen;
char * hashed;
uint8_t buf[SHA_DIGEST_LENGTH];
tr_bool result;
/* extract the salt */
saltlen = strlen( source ) - 2*SHA_DIGEST_LENGTH-1;
salt = tr_malloc( saltlen );
memcpy( salt, source + 2*SHA_DIGEST_LENGTH+1, saltlen );
/* hash pass + salt */
hashed = tr_malloc( 2*SHA_DIGEST_LENGTH + saltlen + 2 );
tr_sha1( buf, pass, strlen( pass ), salt, saltlen, NULL );
tr_sha1_to_hex( &hashed[1], buf );
memcpy( hashed + 1+2*SHA_DIGEST_LENGTH, salt, saltlen );
hashed[1+2*SHA_DIGEST_LENGTH + saltlen] = '\0';
hashed[0] = '{';
result = strcmp( source, hashed ) == 0 ? TRUE : FALSE;
tr_free( hashed );
tr_free( salt );
return result;
}
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