Can you crack it (Part 7)

Dan O'Connor — Sat, 17 Dec 2011 04:35:55 +0000

Here is the contents of the JS file. The file explains exactly what we need to do. Lets dig out some perl and see if we can write something to run this.

//--------------------------------------------------------------------------------------------------
//
// stage 2 of 3
//
// challenge:
//   reveal the solution within VM.mem
//
// disclaimer:
//   tested in ie 9, firefox 6, chrome 14 and v8 shell (http://code.google.com/apis/v8/build.html),
//   other javascript implementations may or may not work.
//
//--------------------------------------------------------------------------------------------------

var VM = {

  cpu: {
    ip: 0x00,

    r0: 0x00,
    r1: 0x00,
    r2: 0x00,
    r3: 0x00,

    cs: 0x00,
    ds: 0x10,

    fl: 0x00,

    firmware: [0xd2ab1f05, 0xda13f110]
  },

  mem: [
    0x31, 0x04, 0x33, 0xaa, 0x40, 0x02, 0x80, 0x03, 0x52, 0x00, 0x72, 0x01, 0x73, 0x01, 0xb2, 0x50,
    0x30, 0x14, 0xc0, 0x01, 0x80, 0x00, 0x10, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

    0x98, 0xab, 0xd9, 0xa1, 0x9f, 0xa7, 0x83, 0x83, 0xf2, 0xb1, 0x34, 0xb6, 0xe4, 0xb7, 0xca, 0xb8,
    0xc9, 0xb8, 0x0e, 0xbd, 0x7d, 0x0f, 0xc0, 0xf1, 0xd9, 0x03, 0xc5, 0x3a, 0xc6, 0xc7, 0xc8, 0xc9,
    0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9,
    0xda, 0xdb, 0xa9, 0xcd, 0xdf, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
    0x26, 0xeb, 0xec, 0xed, 0xee, 0xef, 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9,
    0x7d, 0x1f, 0x15, 0x60, 0x4d, 0x4d, 0x52, 0x7d, 0x0e, 0x27, 0x6d, 0x10, 0x6d, 0x5a, 0x06, 0x56,
    0x47, 0x14, 0x42, 0x0e, 0xb6, 0xb2, 0xb2, 0xe6, 0xeb, 0xb4, 0x83, 0x8e, 0xd7, 0xe5, 0xd4, 0xd9,
    0xc3, 0xf0, 0x80, 0x95, 0xf1, 0x82, 0x82, 0x9a, 0xbd, 0x95, 0xa4, 0x8d, 0x9a, 0x2b, 0x30, 0x69,
    0x4a, 0x69, 0x65, 0x55, 0x1c, 0x7b, 0x69, 0x1c, 0x6e, 0x04, 0x74, 0x35, 0x21, 0x26, 0x2f, 0x60,
    0x03, 0x4e, 0x37, 0x1e, 0x33, 0x54, 0x39, 0xe6, 0xba, 0xb4, 0xa2, 0xad, 0xa4, 0xc5, 0x95, 0xc8,
    0xc1, 0xe4, 0x8a, 0xec, 0xe7, 0x92, 0x8b, 0xe8, 0x81, 0xf0, 0xad, 0x98, 0xa4, 0xd0, 0xc0, 0x8d,
    0xac, 0x22, 0x52, 0x65, 0x7e, 0x27, 0x2b, 0x5a, 0x12, 0x61, 0x0a, 0x01, 0x7a, 0x6b, 0x1d, 0x67,
    0x75, 0x70, 0x6c, 0x1b, 0x11, 0x25, 0x25, 0x70, 0x7f, 0x7e, 0x67, 0x63, 0x30, 0x3c, 0x6d, 0x6a,
    0x01, 0x51, 0x59, 0x5f, 0x56, 0x13, 0x10, 0x43, 0x19, 0x18, 0xe5, 0xe0, 0xbe, 0xbf, 0xbd, 0xe9,
    0xf0, 0xf1, 0xf9, 0xfa, 0xab, 0x8f, 0xc1, 0xdf, 0xcf, 0x8d, 0xf8, 0xe7, 0xe2, 0xe9, 0x93, 0x8e,
    0xec, 0xf5, 0xc8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

    0x37, 0x7a, 0x07, 0x11, 0x1f, 0x1d, 0x68, 0x25, 0x32, 0x77, 0x1e, 0x62, 0x23, 0x5b, 0x47, 0x55,
    0x53, 0x30, 0x11, 0x42, 0xf6, 0xf1, 0xb1, 0xe6, 0xc3, 0xcc, 0xf8, 0xc5, 0xe4, 0xcc, 0xc0, 0xd3,
    0x85, 0xfd, 0x9a, 0xe3, 0xe6, 0x81, 0xb5, 0xbb, 0xd7, 0xcd, 0x87, 0xa3, 0xd3, 0x6b, 0x36, 0x6f,
    0x6f, 0x66, 0x55, 0x30, 0x16, 0x45, 0x5e, 0x09, 0x74, 0x5c, 0x3f, 0x29, 0x2b, 0x66, 0x3d, 0x0d,
    0x02, 0x30, 0x28, 0x35, 0x15, 0x09, 0x15, 0xdd, 0xec, 0xb8, 0xe2, 0xfb, 0xd8, 0xcb, 0xd8, 0xd1,
    0x8b, 0xd5, 0x82, 0xd9, 0x9a, 0xf1, 0x92, 0xab, 0xe8, 0xa6, 0xd6, 0xd0, 0x8c, 0xaa, 0xd2, 0x94,
    0xcf, 0x45, 0x46, 0x67, 0x20, 0x7d, 0x44, 0x14, 0x6b, 0x45, 0x6d, 0x54, 0x03, 0x17, 0x60, 0x62,
    0x55, 0x5a, 0x4a, 0x66, 0x61, 0x11, 0x57, 0x68, 0x75, 0x05, 0x62, 0x36, 0x7d, 0x02, 0x10, 0x4b,
    0x08, 0x22, 0x42, 0x32, 0xba, 0xe2, 0xb9, 0xe2, 0xd6, 0xb9, 0xff, 0xc3, 0xe9, 0x8a, 0x8f, 0xc1,
    0x8f, 0xe1, 0xb8, 0xa4, 0x96, 0xf1, 0x8f, 0x81, 0xb1, 0x8d, 0x89, 0xcc, 0xd4, 0x78, 0x76, 0x61,
    0x72, 0x3e, 0x37, 0x23, 0x56, 0x73, 0x71, 0x79, 0x63, 0x7c, 0x08, 0x11, 0x20, 0x69, 0x7a, 0x14,
    0x68, 0x05, 0x21, 0x1e, 0x32, 0x27, 0x59, 0xb7, 0xcf, 0xab, 0xdd, 0xd5, 0xcc, 0x97, 0x93, 0xf2,
    0xe7, 0xc0, 0xeb, 0xff, 0xe9, 0xa3, 0xbf, 0xa1, 0xab, 0x8b, 0xbb, 0x9e, 0x9e, 0x8c, 0xa0, 0xc1,
    0x9b, 0x5a, 0x2f, 0x2f, 0x4e, 0x4e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
  ],

  exec: function()
  {
    // virtual machine architecture
    // ++++++++++++++++++++++++++++
    //
    // segmented memory model with 16-byte segment size (notation seg:offset)
    //
    // 4 general-purpose registers (r0-r3)
    // 2 segment registers (cs, ds equiv. to r4, r5)
    // 1 flags register (fl)
    //
    // instruction encoding
    // ++++++++++++++++++++
    //
    //           byte 1               byte 2 (optional)
    // bits      [ 7 6 5 4 3 2 1 0 ]  [ 7 6 5 4 3 2 1 0 ]
    // opcode      - - -             
    // mod               -           
    // operand1            - - - -
    // operand2                         - - - - - - - -
    //
    // operand1 is always a register index
    // operand2 is optional, depending upon the instruction set specified below
    // the value of mod alters the meaning of any operand2
    //   0: operand2 = reg ix
    //   1: operand2 = fixed immediate value or target segment (depending on instruction)
    //
    // instruction set
    // +++++++++++++++
    // 
    // Notes:
    //   * r1, r2 => operand 1 is register 1, operand 2 is register 2
    //   * movr r1, r2 => move contents of register r2 into register r1
    // 
    // opcode | instruction | operands (mod 0) | operands (mod 1)
    // -------+-------------+------------------+-----------------
    // 0x00   | jmp         | r1               | r2:r1
    // 0x01   | movr        | r1, r2           | rx,   imm 
    // 0x02   | movm        | r1, [ds:r2]      | [ds:r1], r2
    // 0x03   | add         | r1, r2           | r1,   imm
    // 0x04   | xor         | r1, r2           | r1,   imm 
    // 0x05   | cmp         | r1, r2           | r1,   imm 
    // 0x06   | jmpe        | r1               | r2:r1
    // 0x07   | hlt         | N/A              | N/A
    //
    // flags
    // +++++
    // 
    // cmp r1, r2 instruction results in:
    //   r1 == r2 => fl = 0
    //   r1 < r2  => fl = 0xff
    //   r1 > r2  => fl = 1
    // 
    // jmpe r1
    //   => if (fl == 0) jmp r1
    //      else nop

    throw "VM.exec not yet implemented";
  }

};

//--------------------------------------------------------------------------------------------------

try
{
  VM.exec();
}
catch(e)
{
  alert('\nError: ' + e + '\n');
}

//--------------------------------------------------------------------------------------------------

Can you crack it (Part 4)

Dan O'Connor — Tue, 13 Dec 2011 21:40:59 +0000

I tried running the file.exe created, it does not appear to do anything. It’s important but I don’t know what to do with it just yet.

The thing I find odd was the hex was given in a png, that’s worth checking out.

I have both sets of files on my SIFT Workstation. I will start with my favorite tools.

strings

strings cyber.png  | less

Take a look in the file, here is something worth looking at.

]iTXtComment
QkJCQjIAAACR2PFtcCA6q2eaC8SR+8dmD/zNzLQC+td3tFQ4qx8O447TDeuZw5P+0SsbEcYR
78jKLw==2

That looks like unicode. Lets look at the png’s metadata.

exiftool cyber.png

Comment                         : QkJCQjIAAACR2PFtcCA6q2eaC8SR+8dmD/zNzLQC+td3tFQ4qx8O447TDeuZw5P+0SsbEcYR.78jKLw==

Down at the end is what we are looking for in the Comment section.

That definitely is Unicode. I have a script around to decode that somewhere for part 5..

Can you crack it (Part 3)

Dan O'Connor — Tue, 13 Dec 2011 17:35:38 +0000

Well it looks like I am late to the party, I went back to the site and it’s closed.

That’s ok, we will keep going.

If you have not figured out what is contained in the image, it’s a….

> file test.exe
test.exe: DOS executable (COM)

I have recognized this from experience, if you want to see where file gets this from you can find it here.

less /usr/share/misc/magic
# DR-DOS STACKER.COM SCREATE.SYS missed
>0      byte            0xeb            DOS executable (COM)

Double check the file to make sure you have the correct hex entered in to the file, I had a mistake in mine. The file command will still return a DOS exe if the whole file is not correct. It only checks the first bits.

Irregular Expressions » can you crack it

Can you crack it (Part 7)

Can you crack it (Part 4)

Can you crack it (Part 3)