[UNIX] Game Networking Engine Format String



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Game Networking Engine Format String
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SUMMARY

<http://www.gillius.org/gne/> GNE is "an open source network library
specifically designed for games". The console output provided by the
library (gout) is affected by a format string vulnerability which can be
exploited if the main program shows the data sent by the clients on the
gout console.

DETAILS

Vulnerable Systems:
* GNE version 0.70

Immune Systems:
* GNE CVS version 24

The problem is caused by the absence of the format argument "%s" in both
mlprintf and mprintf.

From ConsoleStreambuf.cpp:
void goutbuf::flush_output() {
//We always have a space for the null pointer because we reserved an
//extra position when we called setp, and we do so again at the end of
//this function.
if (pptr() > pbase()) {
*pptr() = '\0';
if (x != -1) { //Do a mlprintf if a location was set.
assert(y != -1);
Console::mlprintf(x, y, pbase());
x = y = -1; //Unset last location.
} else
Console::mprintf(pbase());
setp(buf, buf + OBUF_LEN - 1);
}


ADDITIONAL INFORMATION

The information has been provided by <mailto:aluigi@xxxxxxxxxxxxx> Luigi
Auriemma.
The original article can be found at:
<http://aluigi.altervista.org/adv/gnefs-adv.txt>
http://aluigi.altervista.org/adv/gnefs-adv.txt



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