Server Help

emileej · Posted: Sun Aug 22, 2004 7:50 am Post subject: Port of twCore encryption to C++

I finally got my encryption by porting the encryption of twCore to C++ and in the spirit of open source I now return it:

Code: Show/Hide

Uint32 encClientKey,encServerKey;
Uint8 encKeyStream[520];
bool encryptionEnabled;

void InitEncryption(){
Uint32 oldSeed,tempSeed=encServerKey;
Uint16 res;
for(int i=0;i<520;i+=sizeof(res)){
oldSeed=tempSeed;
tempSeed=((oldSeed * 0x834E0B5F) >> 48) & 0xffffffff;
tempSeed=((tempSeed + (tempSeed >> 31)) & 0xffffffff);
tempSeed=((((oldSeed % 0x1F31D) * 16807) - (tempSeed * 2836) + 123) & 0xffffffff);
if(tempSeed > 0x7fffffff)
tempSeed=((tempSeed + 0x7fffffff) & 0xffffffff);
res=(Uint16)(tempSeed & 0xffff);
memcpy(encKeyStream+i,&res,sizeof(res));
}

encryptionEnabled=true;
}

void SwitchEndianness(void *ptr,int size){
for(int i=0;i<size/2;i++){
((char*)ptr)[i]^=((char*)ptr)[size-1-i];
((char*)ptr)[size-1-i]^=((char*)ptr)[i];
((char*)ptr)[i]^=((char*)ptr)[size-1-i];
}
}

void Encrypt(char *packet,int size){
if(!encryptionEnabled)
return;

char *data=packet+1;
int len=size-1;
if(!packet[0]){
data++;
len++;
}

Uint32 dataInt,streamInt,tempKey=encServerKey,resInt;
int count=len + (sizeof(tempKey) - len%sizeof(tempKey));

for(int i=0;i<count;i+=sizeof(tempKey)){
memcpy(&dataInt,data+i,sizeof(dataInt));
SwitchEndianness(&dataInt,sizeof(dataInt));
memcpy(&streamInt,encKeyStream+i,sizeof(streamInt));
SwitchEndianness(&streamInt,sizeof(streamInt));

resInt=dataInt ^ streamInt ^ tempKey;

tempKey=resInt;
SwitchEndianness(&resInt,sizeof(resInt));
memcpy(data+i,&resInt,sizeof(resInt));
}
}

void CSSConnection::Decrypt(char *packet,int size){
if(!encryptionEnabled)
return;

char *data=packet+1;
int len=size-1;
if(!packet[0]){
data++;
len++;
}

Uint32 dataInt,streamInt,tempKey=encServerKey,resInt;
int count=len + (sizeof(tempKey) - len%sizeof(tempKey));

for(int i=0;i<count;i+=sizeof(tempKey)){
memcpy(&dataInt,data+i,sizeof(dataInt));
SwitchEndianness(&dataInt,sizeof(dataInt));
memcpy(&streamInt,encKeyStream+i,sizeof(streamInt));
SwitchEndianness(&streamInt,sizeof(streamInt));

resInt=streamInt ^ tempKey ^ dataInt;

tempKey=dataInt;
SwitchEndianness(&resInt,sizeof(resInt));
memcpy(data+i,&resInt,sizeof(resInt));
}
}

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Cyan~Fire · Posted: Sun Aug 22, 2004 11:43 am Post subject:

Talk about hard-to-read code...

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This help is informational only. No representation is made or warranty given as to its content. User assumes all risk of use. Cyan~Fire assumes no responsibility for any loss or delay resulting from such use.
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Solo Ace · Posted: Sun Aug 22, 2004 11:59 am Post subject:

Restyled.

Code: Show/Hide

Uint32 encClientKey, encServerKey;
Uint8 encKeyStream[520];
bool encryptionEnabled;

void InitEncryption()
{
Uint32 oldSeed, tempSeed = encServerKey;
Uint16 res;

for (int i = 0;i < 520;i += sizeof(res))
{
   oldSeed = tempSeed;

   tempSeed = ((oldSeed * 0x834E0B5F) >> 48) & 0xffffffff;
   tempSeed = ((tempSeed + (tempSeed >> 31)) & 0xffffffff);
   tempSeed = ((((oldSeed % 0x1F31D) * 16807) - (tempSeed * 2836) + 123) & 0xffffffff);

   if(tempSeed > 0x7fffffff)
      tempSeed = ((tempSeed + 0x7fffffff) & 0xffffffff);

   res = (Uint16) (tempSeed & 0xffff);
   memcpy(encKeyStream + i, &res, sizeof(res));
}

encryptionEnabled = true;
}

void SwitchEndianness(void *ptr, int size)
{
for(int i = 0;i < size / 2;i++)
{
   ((char *) ptr)[i] ^= ((char *) ptr) [size - 1 - i];
   ((char *) ptr)[size - 1 - i] ^= ((char *) ptr)[i];
   ((char *) ptr)[i] ^= ((char *) ptr) [size - 1 - i];
}
}

void Encrypt(char *packet, int size)
{
if (!encryptionEnabled)
   return;

char *data = packet + 1;
int len = size - 1;

if(!packet[0])
{
   data++;
   len++;
}

Uint32 dataInt, streamInt, tempKey = encServerKey, resInt;

int count = len + (sizeof(tempKey) - len % sizeof(tempKey));

for(int i = 0;i < count;i += sizeof(tempKey))
{
   memcpy(&dataInt, data + i, sizeof(dataInt));
   SwitchEndianness(&dataInt, sizeof(dataInt));

   memcpy(&streamInt, encKeyStream + i, sizeof(streamInt));
   SwitchEndianness(&streamInt, sizeof(streamInt));

   resInt = dataInt ^ streamInt ^ tempKey;

   tempKey = resInt;
   SwitchEndianness(&resInt, sizeof(resInt));
   memcpy(data + i, &resInt, sizeof(resInt));
}
}

void CSSConnection::Decrypt(char *packet, int size)
{
if (!encryptionEnabled)
   return;

char *data = packet + 1;
int len = size - 1;

if(!packet[0])
{
   data++;
   len++;
}

Uint32 dataInt, streamInt, tempKey = encServerKey, resInt;
int count = len + (sizeof(tempKey) - len % sizeof(tempKey));

for(int i = 0;i < count; i += sizeof(tempKey))
{
   memcpy(&dataInt, data+i, sizeof(dataInt));
   SwitchEndianness(&dataInt, sizeof(dataInt));

   memcpy(&streamInt, encKeyStream + i, sizeof(streamInt));
   SwitchEndianness(&streamInt, sizeof(streamInt));

   resInt = streamInt ^ tempKey ^ dataInt;
   tempKey = dataInt;

   SwitchEndianness(&resInt, sizeof(resInt));
   memcpy(data + i, &resInt, sizeof(resInt));
}
}

emileej · Posted: Sun Aug 22, 2004 2:01 pm Post subject:

Thanks ace - I know my coding style is a bit evil

Cyan~Fire · Posted: Sun Aug 22, 2004 5:04 pm Post subject:

Sweet. Thanks, Solo.

Just looking through it:

Code: Show/Hide

if(tempSeed > 0x7fffffff)
tempSeed = ((tempSeed + 0x7fffffff) & 0xffffffff);

What the hay is the point of the "& 0xffffffff". Doesn't that ALWAYS give the same result as before?

emileej · Posted: Sun Aug 22, 2004 7:01 pm Post subject:

Argh! It seems now that it doesnt work after all - I get further when connecting to as3 test server unencrypted than I do encrypted

-Smong- · Guest Offline

emileej · Posted: Mon Aug 23, 2004 11:31 am Post subject: Hmm

Scratch that - Mr. Ekted has tested the ported encryption and found that it works just fine. Strange problem I have then...

Cyan~Fire · Posted: Mon Aug 23, 2004 5:36 pm Post subject:

-Smong- · Guest Offline

I'm not entirely sure, but I think it is only unsigned while being stored and retrieved, so during a calculation you can sort of change/cast it to some other type that I don't know the name to, hey it works so I'm not bothered.

Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

Mr Ekted · Movie Geek Gender: Joined: Feb 09 2004 Posts: 1379 Offline

In C or C++, any 32-bit value bitwise AND'ed with 0xffffffff does not change value or sign since none of the bits are affected by the operation. In fact, the optimizer would simply remove the expression from the resulting code.
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Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

Yes, but it was from the java code

Cyan~Fire · Posted: Tue Aug 24, 2004 6:25 am Post subject:

Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

Ok I ment 32 bits, err and no it does not change it to unsigned, I am pretty sure of this, I mean how would it? It is not changing on how the number is stored. And there is a point for using &, if you make it a char, it is a byte and is not a number, you can not make any calculalations with it, you would have to put it back to an integer, which is more work.

Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

emileej:

res=(Uint16)(tempSeed & 0xffff);
memcpy(encKeyStream+i,&res,sizeof(res));

encKeyStream is Uint8, how can you put a 16 bit integer in a 8 bit element?

This is what I did and it works:

sub initialize {
use bigint;
my $seed = $_[0];
my ($tempSeed, $oldSeed);
$tempSeed = $seed;

# use Math::BigInt;
# my $seed = Math::BigInt->new($_[0]);
# my ($tempSeed, $oldSeed);
# $tempSeed = Math::BigInt->new("$seed");

for ($i = 0; $i < (520 / 2); $i++) {
$oldSeed = $tempSeed;

$tempSeed = (($oldSeed * 0x834E0B5F) >> 4

& 0xffffffff;
$tempSeed = (($tempSeed + ($tempSeed >> 31)) & 0xffffffff);
$tempSeed = (((($oldSeed % 0x1F31D) * 16807) - ($tempSeed * 2836) + 123) & 0xffffffff);
if ($tempSeed > 0x7fffffff ) {
$tempSeed = (($tempSeed + 0x7fffffff) & 0xffffffff);
}
push(@table, ence_short(short($tempSeed & 0xffff)));
}
}

emileej · Posted: Tue Aug 24, 2004 7:15 am Post subject:

Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

Why would you treat a short as a byte? Also you need each element has to be 1 byte, each 16 bit integer you put into it needs to be 2 elements

emileej · Posted: Tue Aug 24, 2004 7:24 am Post subject:

Why I would treat it a s abyte? Well how on earth do you expect me to put it in my byte array if I was not to?
And yes ofcourse it needs to be two elements. When I said that sizeof returns the size of a variable or type in bytes then exactly which number do you think it returns when it is fed a 16bit variable?

Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

You need to put each 2 bytes from each short into 2 seperate elements

emileej · Posted: Tue Aug 24, 2004 8:07 am Post subject:

Miesco · Newbie Joined: Aug 23 2004 Posts: 24 Offline

emileej · Posted: Wed Aug 25, 2004 2:36 am Post subject: InitEncryption

It seems though that youre partly right - the bug is in fact in the InitEncryption. Take a look at this log of the server key and the resulting keystream.