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| RogerWilco is probably the most famous tool that lets gamers to speak together during the matches with their preferred games. It is shareware and is developed by GameSpy. Two vulnerabilities in the product allow attackers to cause the client to crash (while executing arbitrary code), and the server to freeze. |
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Credit:
The information has been provided by Auriemma Luigi.
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Vulnerable systems:
* RogerWilco version 1.4.1.1d3 and prior
Immune systems:
* RogerWilco version 1.4.1.2
Broadcast Buffer Overflow
This bug is just the perfect situation to make tons of damage using the minimum energy. Until now Auriemma has never found a "broadcast" buffer overflow, so Auriemma was very interested about it.
This buffer overflow happens when a client that connects to the server sends a nickname string that is too long (a classical buffer overflow). The nickname must be at least 516 bytes long to overwrite the return address of EVERY client that receive this nickname.
In fact the server (both normal and dedicated server) will send the nickname field in broadcast to ALL the clients connected to it. That mean that ALL the clients connected to the server (the graphical program become both server and client when hosts a channel) will execute the malicious code in the nickname field sent by the attacker!
Now a bit of assembly for those that are interested in the details:
The vulnerable function starts at offset 0x40a1b0 of roger.exe. The instructions that cause the overwriting of the return address are the following:
:0040A200 8BF7 mov esi, edi
:0040A202 8B7C2414 mov edi, dword ptr [esp+14]
:0040A206 C1E902 shr ecx, 02
:0040A209 F3A5 repz movsd
:0040A200 ESI will point to the beginning of the nickname sent by the
client ("aaaaaaaaaaaaaaaaaaaaaa...")
:0040A202 now the address of the destination buffer will be copied
into EDI register
:0040A206 the size of the data will be divided for 4 (it copies 32
bits each time)
:0040A209 it copies the bytes that starts at the address pointed by
ESI to the new buffer overwriting the return address stored
at offset 0x0068f080 (the right return address stored before
the BoF was 0x00409304)
When RogerWilco executes the instruction at offset 0x0040A209 the return address stored at offset 0x0068f080 will be fully overwritten.
Server Freeze
A client can connect to the server that hosts a channel and instead of sending a full packet it sends it partially. The "join-packet" contains all the data of the client as the channel it wants to join to, the password for the channel, its nickname and some other little information.
The problem happens when the client uses the nickname tag ("\x0f\x10") BUT doesn't complete the packet with all the other needed information. An example is the following packet:
"\x0f\x00"
"\x00\x14"
"\x6a\xd6\x4c\x03\x96\xed\x3b\xe7\x88\xe2\xa9\x74"
"channel\0"
"\x0f\x10"
<-- here there is nothing!
As you can see there is nothing after the nickname tag. The problem happens in NETWORK.DLL when the program calls the function WSOCK32.recv:
---
:100027B1 51 push ecx
* Reference To: WSOCK32.recv, Ord:0010h
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:100027B2 E8BF440000 Call 10006C76
:100027B7 CC int 03
---
In fact the recv() function will NOT return until the malicious client is connected to the server (probably because it waits the other pieces of data that the attacker has not sent).
Once the attacker disconnects itself, the situation returns normally.
Exploit code:
Auriemma Luigi has written a program that tests the 2 bugs he found. You can choose your nickname, the channel to join, the password to use, the port to connect to, an auto-rejoin option (so you can rejoin infinitely), get remote information and naturally you can also see what happens in real-time on the server, as who enters, who exits, their IP addresses, who changes his nickname, etc.
Naturally, as almost all Auriemma Luigi's tools, it can be compiled on both UNIX and Windows: http://www.pivx.com/luigi/poc/wilco.zip
Fix:
RogerWilco supports the auto-update feature so you should already have the patched version, in any case the latest (1.4.1.2) released 16th June 2003 is available on the official homepage: http://www.rogerwilco.com
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