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KisMAC Cisco Vendor Tag Encapsulated SSID Overflow
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SUMMARY
<http://www.kismac.de> KisMAC is "a free stumbler application for MacOS
X, that puts your card into the monitor mode. Unlike most other
applications for OS X it has the ability to run completely invisible and
send no probe requests."
While Stefan played around with wifi, raw packets, MacOS X, ppc and KisMAC
a quick audit revealed a remotely triggerable buffer overflow in KisMAC's
parser for tagged data in 80211 management frames, that can lead to
execution of arbitrary code.
To exploit this vulnerability an attacker must either trick the victim in
opening a pcap file containing the special crafted management frames OR
the attacker must send such raw frames while the victim is performing a
passive network scan.
DETAILS
Vulnerable Systems:
* KisMAC dev version 113 and prior
* KisMAC version 73p and prior
Immune Systems:
* KisMAC dev version 114 or newer
* KisMAC version 74p or newer
When KisMAC receives a 80211 management frame (or finds one in a imported
pcap file) it parses the attached tagged data with the function
WavePacket:parseTaggedData. With the help of this method the SSID, the
channel and the rates get extracted from the management packet.
The function in question also supports a special Cisco vendor tag, which
is scanned by KisMAC for additional SSIDs. Unfortunately it then copies
the SSIDs found into a 33 bytes big stackbuffer without any kind of size
check.
slen = (*(ssidl + 5)); // <-- reading SSID length (UINT8)
ssidl += 6;
if ((len -= slen) < 0) break;
@try {
memcpy(ssid, ssidl, slen); // <-- copying without check into 33
// bytes big stackbuffer
ssid[slen]=0;
[_SSIDs addObject:[NSString stringWithUTF8String:ssid]];
}
@catch (NSException *exception) {
[_SSIDs addObject:[NSString stringWithCString:(char*)(ssidl)
length:slen]];
}
Due to the try/catch block around the memcpy() the stacklayout allows to
overwrite the jump_buf for setjmp/longjump which are used for the
exception handling. This actually means it is not only possible to control
the execution flow by manipulating the program counter (pc) but also to
have control over the content of all registers once the execution flow has
been manipulated.
It should be obvious that this eventually leads to the execution of
arbitrary code.
Disclosure Timeline:
22. March 2006 - Contacted KisMAC developers by email
22. March 2006 - Vendor releases KisMAC update
23. March 2006 - Public Disclosure
ADDITIONAL INFORMATION
The information has been provided by <mailto:sesser@hardened-php.net>
Stefan Esser.
The original article can be found at:
<http://www.hardened-php.net/advisory_032006.115.html>
http://www.hardened-php.net/advisory_032006.115.html
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