PicoCTF - Powershelly

Background

Powershell 命令提示字元比較 What is ‘@{}’ meaning in PowerShell What does @() mean in Powershell? [Python] 學習使用集合 (Set)

Source code

:::spoiler Source Code

$input = ".\input.txt"

$out = Get-Content -Path $input
$enc = [System.IO.File]::ReadAllBytes("$input")
$encoding = [system.Text.Encoding]::UTF8
$total = 264
$t = ($total + 1) * 5 #1325
$numLength = ($total * 30 ) + $t # 9245
if ($out.Length -gt 5 -or $enc.count -ne $numLength)
{
  Write-Output "Wrong format 5"
  Exit
}

else
{
  for($i=0; $i -lt $enc.count ; $i++)
  {
    if (($enc[$i] -ne 49) -and ($enc[$i] -ne 48) -and ($enc[$i] -ne 10) -and ($enc[$i] -ne 13) -and ($enc[$i] -ne 32))
    {
      Write-Output "Wrong format 1/0/"
      Exit
    }
  }
}

$blocks = @{}
for ($i=0; $i -lt $out.Length ; $i++)
{
  $r = $out[$i].Split(" ")
  if ($i -gt 0)
  {
    for ($j=0; $j -lt $r.Length ; $j++)
    {
      if ($r[$j].Length -ne 6)
      {
        Write-Output "Wrong Format 6" $r[$j].Length
        Exit
      }
      $blocks[$j] += $r[$j]
    }
  }
  else
  {
    for ($j=0; $j -lt $r.Length ; $j++)
    {
      if ($r[$j].Length -ne 6)
      {
        Write-Output "Wrong Format 6" $r[$j].Length
        Exit
      }
      $blocks[$j] = @()
      $blocks[$j] += $r[$j]
    }
  }

}


function Exit  {
  exit
}


function Random-Gen {
  $list1 = @()
  for ($i=1; $i -lt ($blocks.count + 1); $i++)
  {
    $y = ((($i * 327) % 681 ) + 344) % 313
    $list1 += $y
  }
  return $list1
}


function Scramble {
    param (
        $block,
        $seed
    )
    $raw = [system.String]::Join("", $block)
    $bm = "10 " * $raw.Length
    $bm = $bm.Split(" ")
    for ($i=0; $i -lt $raw.Length ; $i++)
    {

      $y = ($i * $seed) % $raw.Length
      $n = $bm[$y]
      while ($n -ne "10")
      {
        $y = ($y + 1) % $raw.Length
        $n = $bm[$y]
      }
      if ($raw[$i] -eq "1" )
      {
        $n = "11"
      }
      else
      {
        $n = "00"
      }
      $bm[$y] = $n
    }
    $raw2 = [system.String]::Join("", $bm)
    $b = [convert]::ToInt64($raw2,2)
    return $b
}


$result = 0
$seeds = @()
for ($i=1; $i -lt ($blocks.count +1); $i++)
{
  $seeds += ($i * 127) % 500
}

$randoms = Random-Gen
$output_file = @()
for ($i=0; $i -lt $blocks.count ; $i++)
{

  $fun = Scramble -block $blocks[$i] -seed $seeds[$i]
  if($i -eq 263)
  {
    Write-Output $seeds[$i]
    Write-Output $randoms[$i]
    Write-Output $fun
  }
  $result = $fun -bxor $result -bxor $randoms[$i]
  $output_file += $result
}
Add-Content -Path output_test.txt -Value $output_file

:::

Recon

這一題太難了，花了好多時間，不看¹的WP大概猜到了六七成，不過最後的部分才是關鍵，再加上不是很懂powershell的語法

1. Check File Format 首先他先檢查input.txt的格式，可以從這邊看出來他應該是一個==5列的content==，以及總字元數(所有bytes的數量)是9245，接著他判斷每個字元是否都符合0, 1, carriage return, \n, <space>

   1 2 3

   if ($out.Length -gt 5 -or $enc.count -ne $numLength) ... if (($enc[$i] -ne 49) -and ($enc[$i] -ne 48) -and ($enc[$i] -ne 10) -and ($enc[$i] -ne 13) -and ($enc[$i] -ne 32))

   另外他還會檢查每一個row中，用空格split的每一個element是不是都符合6個字元，簡單解釋一下下面在幹嘛，他先創一個dictionary，叫做$blocks，然後把$out第一個row，先用空格格開，再比對每一個element是否都是6個字元，實際跑過之後他會長下面這樣 :::spoiler $blocks的格式

   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

   Name Value ---- ----- 263 {110011, 100011, 110011, 110011...} 262 {100001, 001100, 001100, 001100...} 261 {110011, 100011, 110011, 110011...} 260 {110011, 100011, 110011, 110011...} 259 {110011, 100011, 110011, 110011...} 258 {110011, 100011, 110011, 110011...} 257 {110011, 100011, 110011, 110011...} 256 {100001, 001100, 001100, 001100...} 255 {110011, 100011, 110011, 110011...} 254 {100001, 001100, 001100, 001100...} 253 {100001, 001100, 001100, 001100...} 252 {100001, 001100, 001100, 001100...} 251 {100001, 001100, 001100, 001100...} 250 {110011, 100011, 110011, 110011...} 249 {100001, 001100, 001100, 001100...} 248 {100001, 001100, 001100, 001100...} 247 {100001, 001100, 001100, 001100...} 246 {100001, 001100, 001100, 001100...} 245 {110011, 100011, 110011, 110011...} 244 {110011, 100011, 110011, 110011...} 243 {100001, 001100, 001100, 001100...} 242 {110011, 100011, 110011, 110011...} 241 {110011, 100011, 110011, 110011...} 240 {100001, 001100, 001100, 001100...} 239 {110011, 100011, 110011, 110011...} 238 {100001, 001100, 001100, 001100...} 237 {110011, 100011, 110011, 110011...} 236 {100001, 001100, 001100, 001100...} 235 {100001, 001100, 001100, 001100...} 234 {110011, 100011, 110011, 110011...} 233 {110011, 100011, 110011, 110011...} 232 {100001, 001100, 001100, 001100...} 231 {100001, 001100, 001100, 001100...} 230 {100001, 001100, 001100, 001100...} 229 {100001, 001100, 001100, 001100...} 228 {110011, 100011, 110011, 110011...} 227 {100001, 001100, 001100, 001100...} 226 {110011, 100011, 110011, 110011...} 225 {110011, 100011, 110011, 110011...} 224 {100001, 001100, 001100, 001100...} 223 {100001, 001100, 001100, 001100...} 222 {100001, 100011, 001100, 001100...} 221 {110011, 001100, 110011, 110011...} 220 {100001, 001100, 001100, 001100...} 219 {100001, 001100, 001100, 001100...} 218 {110011, 100011, 110011, 110011...} 217 {100001, 001100, 001100, 001100...} 216 {100001, 001100, 001100, 001100...} 215 {100001, 001100, 001100, 001100...} 214 {110011, 100011, 110011, 110011...} 213 {100001, 001100, 001100, 001100...} 212 {100001, 001100, 001100, 001100...} 211 {110011, 100011, 110011, 110011...} 210 {110011, 100011, 110011, 110011...} 209 {110011, 100011, 110011, 110011...} 208 {100001, 001100, 001100, 001100...} 207 {110011, 100011, 110011, 110011...} 206 {110011, 100011, 110011, 110011...} 205 {100001, 001100, 001100, 001100...} 204 {100001, 001100, 001100, 001100...} 203 {110011, 100011, 110011, 110011...} 202 {110011, 100011, 110011, 110011...} 201 {100001, 001100, 001100, 001100...} 200 {100001, 001100, 001100, 001100...} 199 {110011, 100011, 110011, 110011...} 198 {110011, 100011, 110011, 110011...} 197 {110011, 100011, 110011, 110011...} 196 {100001, 001100, 001100, 001100...} 195 {110011, 100011, 110011, 110011...} 194 {110011, 100011, 110011, 110011...} 193 {110011, 100011, 110011, 110011...} 192 {100001, 001100, 001100, 001100...} 191 {110011, 100011, 110011, 110011...} 190 {110011, 100011, 110011, 110011...} 189 {110011, 100011, 110011, 110011...} 188 {110011, 100011, 110011, 110011...} 187 {100001, 001100, 001100, 001100...} 186 {110011, 100011, 110011, 110011...} 185 {110011, 100011, 110011, 110011...} 184 {100001, 001100, 001100, 001100...} 183 {100001, 001100, 001100, 001100...} 182 {100001, 001100, 001100, 001100...} 181 {100001, 001100, 001100, 001100...} 180 {100001, 001100, 001100, 001100...} 179 {110011, 100011, 110011, 110011...} 178 {110011, 100011, 110011, 110011...} 177 {110011, 100011, 110011, 110011...} 176 {100001, 001100, 001100, 001100...} 175 {110011, 100011, 110011, 110011...} 174 {110011, 100011, 110011, 110011...} 173 {110011, 100011, 110011, 110011...} 172 {110011, 100011, 110011, 110011...} 171 {110011, 100011, 110011, 110011...} 170 {100001, 001100, 001100, 001100...} 169 {110011, 100011, 110011, 110011...} 168 {100001, 001100, 001100, 001100...} 167 {100001, 001100, 001100, 001100...} 166 {110011, 100011, 110011, 110011...} 165 {100001, 001100, 001100, 001100...} 164 {100001, 001100, 001100, 001100...} 163 {110011, 100011, 110011, 110011...} 162 {110011, 100011, 110011, 110011...} 161 {100001, 001100, 001100, 001100...} 160 {100001, 001100, 001100, 001100...} 159 {110011, 100011, 110011, 110011...} 158 {110011, 100011, 110011, 110011...} 157 {110011, 100011, 110011, 110011...} 156 {110011, 100011, 110011, 110011...} 155 {110011, 100011, 110011, 110011...} 154 {100001, 001100, 001100, 001100...} 153 {110011, 100011, 110011, 110011...} 152 {100001, 001100, 001100, 001100...} 151 {110011, 100011, 110011, 110011...} 150 {100001, 001100, 001100, 001100...} 149 {100001, 001100, 001100, 001100...} 148 {110011, 100011, 110011, 110011...} 147 {110011, 100011, 110011, 110011...} 146 {110011, 100011, 110011, 110011...} 145 {110011, 100011, 110011, 110011...} 144 {100001, 001100, 001100, 001100...} 143 {100001, 001100, 001100, 001100...} 142 {100001, 001100, 001100, 001100...} 141 {100001, 001100, 001100, 001100...} 140 {100001, 001100, 001100, 001100...} 139 {100001, 001100, 001100, 001100...} 138 {100001, 001100, 001100, 001100...} 137 {110011, 100011, 110011, 110011...} 136 {100001, 001100, 001100, 001100...} 135 {110011, 100011, 110011, 110011...} 134 {110011, 100011, 110011, 110011...} 133 {110011, 100011, 110011, 110011...} 132 {100001, 001100, 001100, 001100...} 131 {110011, 100011, 110011, 110011...} 130 {110011, 100011, 110011, 110011...} 129 {110011, 100011, 110011, 110011...} 128 {100001, 001100, 001100, 001100...} 127 {100001, 001100, 001100, 001100...} 126 {100001, 001100, 001100, 001100...} 125 {100001, 001100, 001100, 001100...} 124 {110011, 100011, 110011, 110011...} 123 {100001, 001100, 001100, 001100...} 122 {110011, 100011, 110011, 110011...} 121 {110011, 100011, 110011, 110011...} 120 {100001, 001100, 001100, 001100...} 119 {110011, 100011, 110011, 110011...} 118 {110011, 100011, 110011, 110011...} 117 {110011, 100011, 110011, 110011...} 116 {100001, 001100, 001100, 001100...} 115 {100001, 001100, 001100, 001100...} 114 {110011, 100011, 110011, 110011...} 113 {110011, 100011, 110011, 110011...} 112 {100001, 001100, 001100, 001100...} 111 {110011, 100011, 110011, 110011...} 110 {100001, 001100, 001100, 001100...} 109 {100001, 001100, 001100, 001100...} 108 {110011, 100011, 110011, 110011...} 107 {100001, 001100, 001100, 001100...} 106 {110011, 100011, 110011, 110011...} 105 {110011, 100011, 110011, 110011...} 104 {100001, 001100, 001100, 001100...} 103 {100001, 001100, 001100, 001100...} 102 {100001, 001100, 001100, 001100...} 101 {100001, 001100, 001100, 001100...} 100 {110011, 100011, 110011, 110011...} 99 {100001, 001100, 001100, 001100...} 98 {110011, 100011, 110011, 110011...} 97 {110011, 100011, 110011, 110011...} 96 {100001, 001100, 001100, 001100...} 95 {100001, 001100, 001100, 001100...} 94 {100001, 001100, 001100, 001100...} 93 {100001, 001100, 001100, 001100...} 92 {110011, 100011, 110011, 110011...} 91 {110011, 100011, 110011, 110011...} 90 {110011, 100011, 110011, 110011...} 89 {100001, 001100, 001100, 001100...} 88 {100001, 001100, 001100, 001100...} 87 {110011, 100011, 110011, 110011...} 86 {100001, 001100, 001100, 001100...} 85 {100001, 001100, 001100, 001100...} 84 {100001, 001100, 001100, 001100...} 83 {110011, 100011, 110011, 110011...} 82 {110011, 100011, 110011, 110011...} 81 {100001, 001100, 001100, 001100...} 80 {100001, 001100, 001100, 001100...} 79 {100001, 001100, 001100, 001100...} 78 {100001, 001100, 001100, 001100...} 77 {100001, 001100, 001100, 001100...} 76 {100001, 001100, 001100, 001100...} 75 {110011, 100011, 110011, 110011...} 74 {110011, 100011, 110011, 110011...} 73 {100001, 001100, 001100, 001100...} 72 {100001, 001100, 001100, 001100...} 71 {100001, 001100, 001100, 001100...} 70 {110011, 100011, 110011, 110011...} 69 {100001, 001100, 001100, 001100...} 68 {100001, 001100, 001100, 001100...} 67 {110011, 100011, 110011, 110011...} 66 {110011, 100011, 110011, 110011...} 65 {100001, 001100, 001100, 001100...} 64 {100001, 001100, 001100, 001100...} 63 {110011, 100011, 110011, 110011...} 62 {110011, 100011, 110011, 110011...} 61 {100001, 001100, 001100, 001100...} 60 {110011, 100011, 110011, 110011...} 59 {110011, 100011, 110011, 110011...} 58 {110011, 100011, 110011, 110011...} 57 {110011, 100011, 110011, 110011...} 56 {100001, 001100, 001100, 001100...} 55 {100001, 001100, 001100, 001100...} 54 {110011, 100011, 110011, 110011...} 53 {110011, 100011, 110011, 110011...} 52 {100001, 001100, 001100, 001100...} 51 {100001, 001100, 001100, 001100...} 50 {100001, 001100, 001100, 001100...} 49 {110011, 100011, 110011, 110011...} 48 {100001, 001100, 001100, 001100...} 47 {100001, 001100, 001100, 001100...} 46 {100001, 001100, 001100, 001100...} 45 {110011, 100011, 110011, 110011...} 44 {100001, 001100, 001100, 001100...} 43 {110011, 100011, 110011, 110011...} 42 {100001, 001100, 001100, 001100...} 41 {110011, 100011, 110011, 110011...} 40 {100001, 001100, 001100, 001100...} 39 {110011, 100011, 110011, 110011...} 38 {110011, 100011, 110011, 110011...} 37 {100001, 001100, 001100, 001100...} 36 {100001, 001100, 001100, 001100...} 35 {100001, 001100, 001100, 001100...} 34 {100001, 001100, 001100, 001100...} 33 {110011, 100011, 110011, 110011...} 32 {100001, 001100, 001100, 001100...} 31 {110011, 100011, 110011, 110011...} 30 {110011, 100011, 110011, 110011...} 29 {110011, 100011, 110011, 110011...} 28 {110011, 100011, 110011, 110011...} 27 {100001, 001100, 001100, 001100...} 26 {110011, 100011, 110011, 110011...} 25 {110011, 100011, 110011, 110011...} 24 {100001, 001100, 001100, 001100...} 23 {110011, 100011, 110011, 110011...} 22 {110011, 100011, 110011, 110011...} 21 {100001, 001100, 001100, 001100...} 20 {100001, 001100, 001100, 001100...} 19 {100001, 001100, 001100, 001100...} 18 {110011, 100011, 110011, 110011...} 17 {110011, 100011, 110011, 110011...} 16 {100001, 001100, 001100, 001100...} 15 {110011, 100011, 110011, 110011...} 14 {100001, 001100, 001100, 001100...} 13 {100001, 001100, 001100, 001100...} 12 {110011, 100011, 110011, 110011...} 11 {100001, 001100, 001100, 001100...} 10 {110011, 100011, 110011, 110011...} 9 {110011, 100011, 110011, 110011...} 8 {100001, 001100, 001100, 001100...} 7 {100001, 001100, 001100, 001100...} 6 {100001, 001100, 001100, 001100...} 5 {100001, 001100, 001100, 001100...} 4 {100001, 001100, 001100, 001100...} 3 {110011, 100011, 110011, 110011...} 2 {110011, 100011, 110011, 110011...} 1 {110011, 100011, 110011, 110011...} 0 {100001, 001100, 001100, 001100...}

   :::

    $blocks = @{}
    for ($i=0; $i -lt $out.Length ; $i++)
    {
      $r = $out[$i].Split(" ")
      if ($i -gt 0)
      {
        for ($j=0; $j -lt $r.Length ; $j++)
        {
          if ($r[$j].Length -ne 6)
          {
            Write-Output "Wrong Format 6" $r[$j].Length
            Exit
          }
          $blocks[$j] += $r[$j]
        }
      }
      else
      {
        for ($j=0; $j -lt $r.Length ; $j++)
        {
          if ($r[$j].Length -ne 6)
          {
            Write-Output "Wrong Format 6" $r[$j].Length
            Exit
          }
          $blocks[$j] = @()
          $blocks[$j] += $r[$j]
        }
      }
   
    }
   

   Note: $out.Length在只有一列的情況下會return那一列的字元數，但如果列的數量大於一，就會return列的數量，例如：假設input.txt目前有三列，則$out==3，但如果現在只有一列，而此列上寫了10個字元，則$out==10

2. Before Encryption 在執行加密之前，他會運算seeds和random number以便後續的運算

    for ($i=1; $i -lt ($blocks.count +1); $i++)
    {
      $seeds += ($i * 127) % 500
    }
   

    function Random-Gen {
      $list1 = @()
      for ($i=1; $i -lt ($blocks.count + 1); $i++)
      {
        $y = ((($i * 327) % 681 ) + 344) % 313
        $list1 += $y
      }
      return $list1
    }
   

3. Encryption 實際加密的步驟是：計算$fun，他先create一個list，然後先存’10’*$raw.Length，然後用$seed計算index(隨機的)，如果$raw[$index]是1，那就改成11，相反，如果是0，就改成00。接著他會和$result以及$randoms[$i]做xor，就得到最後的ciphertext

4. Decryption
   1. 我們的目標是要還原出一開始input file中的內容，這樣我們才知道最後的flag的形式長怎麼，所以做法就是逆著做回去，先算出$fun是多少，一開始的$result是0，所以我們可以直接再做xor，就得到$fun，

       fun = int(output[i].strip()) ^ result ^ randoms[i]
      

      Note: $seeds和$randoms可以直接用他給的code section用PS跑看看再存成檔案，也可以直接用python實作，答案會是一樣的

   2. 接著，因為他原本是存成binary的形式，所以轉成binary之後要把他split成兩兩一組，再進行之前說的1$\iff$11和0$\iff$00轉換，也就是先計算前面提到的random index by (j * seeds[i]) % len(tmpFlagSplit)，再看對應的array是00還是11

           for j in range(len(tmpFlagSplit)):
               y = (j * seeds[i]) % len(tmpFlagSplit)
               if tmpFlagSplit[y] == 'x':
                   while(tmpFlagSplit[y] == 'x'):
                       y = (y + 1) % len(tmpFlagSplit)
               if tmpFlagSplit[y] == '00':
                   finalFlag += "0"
                   tmpFlagSplit[y] = 'x'
               elif tmpFlagSplit[y] == '11':
                   finalFlag += "1"
                   tmpFlagSplit[y] = 'x'
      

   3. 前面提到他是一個擁有五個列as content的file，然後每一列都會每六個字元用空格隔開的形式，因此我們也要把結果變成這樣才對。

       finalFlagArr = [[], [], [], [], []]
       for i in range(len(finalFlag)):
           finalFlagArr[i % 5].append(finalFlag[i])
      

5. Find Flag 透過上述的形式，我們已經把input.txt還原出來了，仔細觀察會發現每一個row，都只有包含兩種字串，舉例：第一個row就只包含100001和110011而已，而第二個row則只有包含001100和100011，寫CTF也這麼久了，直覺就是一個binary encoding，試著把100001當成0，另外一個當成1，再傳換成utf-8應該就會產生flag了

Exploit

output = open('./PicoCTF/Reverse/Powershelly/output.txt', 'r').readlines()

finalFlag = []
tmpFlagSplit = []
randoms = [45, 59, 18, 32, 304, 5, 277, 291, 250, 264, 223, 237, 196, 210, 169, 183, 142, 156, 115, 129, 88, 102, 61, 75, 34, 48, 62, 21, 35, 307, 8, 280, 294, 253, 267, 226, 240, 199, 213, 172, 186, 145, 159, 118, 132, 91, 105, 64, 78, 37, 51, 65, 24, 38, 310, 11, 283, 297, 256, 270, 229, 243, 202, 216, 175, 189, 148, 162, 121, 135, 94, 108, 67, 81, 40, 54, 68, 27, 41, 0, 14, 286, 300, 259, 273, 232, 246, 205, 219, 178, 192, 151, 165, 124, 138, 97, 111, 70, 84, 43, 57, 71, 30, 44, 3, 17, 289, 303, 262, 276, 235, 249, 208, 222, 181, 195, 154, 168, 127, 141, 100, 114, 73, 87, 46, 60, 74, 33, 47, 6, 20, 292, 306, 265, 279, 238, 252, 211, 225, 184, 198, 157, 171, 130, 144, 103, 117, 76, 90, 49, 63, 77, 36, 50, 9, 23, 295, 309, 268, 282, 241, 255, 214, 228, 187, 201, 160, 174, 133, 147, 106, 120, 79, 93, 52, 66, 80, 39, 53, 12, 26, 298, 312, 271, 285, 244, 258, 217, 231, 190, 204, 163, 177, 136, 150, 109, 123, 82, 96, 55, 69, 83, 42, 56, 15, 29, 301, 2, 274, 288, 247, 261, 220, 234, 193, 207, 166, 180, 139, 153, 112, 126, 85, 99, 58, 72, 31, 45, 59, 18, 32, 304, 5, 277, 291, 250, 264, 223, 237, 196, 210, 169, 183, 142, 156, 115, 129, 88, 102, 61, 75, 34, 48, 62, 21, 35, 307, 8, 280, 294, 253, 267, 226, 240]

seeds = [127, 254, 381, 8, 135, 262, 389, 16, 143, 270, 397, 24, 151, 278, 405, 32, 159, 286, 413, 40, 167, 294, 421, 48, 175, 302, 429, 56, 183, 310, 437, 64, 191, 318, 445, 72, 199, 326, 453, 80, 207, 334, 461, 88, 215, 342, 469, 96, 223, 350, 477, 104, 231, 358, 485, 112, 239, 366, 493, 120, 247, 374, 1, 128, 255, 382, 9, 136, 263, 390, 17, 144, 271, 398, 25, 152, 279, 406, 33, 160, 287, 414, 41, 168, 295, 422, 49, 176, 303, 430, 57, 184, 311, 438, 65, 192, 319, 446, 73, 200, 327, 454, 81, 208, 335, 462, 89, 216, 343, 470, 97, 224, 351, 478, 105, 232, 359, 486, 113, 240, 367, 494, 121, 248, 375, 2, 129, 256, 383, 10, 137, 264, 391, 18, 145, 272, 399, 26, 153, 280, 407, 34, 161, 288, 415, 42, 169, 296, 423, 50, 177, 304, 431, 58, 185, 312, 439, 66, 193, 320, 447, 74, 201, 328, 455, 82, 209, 336, 463, 90, 217, 344, 471, 98, 225, 352, 479, 106, 233, 360, 487, 114, 241, 368, 495, 122, 249, 376, 3, 130, 257, 384, 11, 138, 265, 392, 19, 146, 273, 400, 27, 154, 281, 408, 35, 162, 289, 416, 43, 170, 297, 424, 51, 178, 305, 432, 59, 186, 313, 440, 67, 194, 321, 448, 75, 202, 329, 456, 83, 210, 337, 464, 91, 218, 345, 472, 99, 226, 353, 480, 107, 234, 361, 488, 115, 242, 369, 496, 123, 250, 377, 4, 131, 258, 385, 12, 139, 266, 393, 20, 147, 274, 401, 28]

result = 0
for i in range(len(output)):
    fun = int(output[i].strip()) ^ result ^ randoms[i]
    result = int(output[i].strip())
    tmp = bin(fun)[2:]
    tmpFlagSplit = [tmp[i:i+2] for i in range(0, len(tmp), 2)]
    assert len(tmpFlagSplit) == 30

    for j in range(len(tmpFlagSplit)):
        y = (j * seeds[i]) % len(tmpFlagSplit)
        if tmpFlagSplit[y] == 'x':
            while(tmpFlagSplit[y] == 'x'):
                y = (y + 1) % len(tmpFlagSplit)
        if tmpFlagSplit[y] == '00':
            finalFlag += "0"
            tmpFlagSplit[y] = 'x'
        elif tmpFlagSplit[y] == '11':
            finalFlag += "1"
            tmpFlagSplit[y] = 'x'
finalFlag = "".join(finalFlag)
finalFlag = [finalFlag[i:i+6] for i in range(0, len(finalFlag), 6)]
print(finalFlag)

finalFlagArr = [[], [], [], [], []]
for i in range(len(finalFlag)):
    finalFlagArr[i % 5].append(finalFlag[i])

for i in range(len(finalFlagArr)):
    tmp_arr = set(finalFlagArr[i])
    tmp_arr_single_row = " ".join(finalFlagArr[i])
    bit = "0"
    for j in tmp_arr:
        tmp_arr_single_row = tmp_arr_single_row.replace(j, bit)
        bit = '1'
    finalFlagArr[i] = tmp_arr_single_row.replace(" ", "")
print(bytes.fromhex(hex(int(finalFlagArr[0], 2))[2:]).decode('cp437'))

Flag: picoCTF{2018highw@y_2_pow3r$hel!}

Reference

1. Powershelly [180 Points] - 101 Solves ↩