RADARCTF

RADARCTF writeup Black

  • Black
  • Points: 200
  • Type: Misc
  • Solves: 141
  • Download
Just a black photo ..
ダウンロードしたファイルを解凍するとjpgファイルができます。ImageJで開いて[Image]-[Adjust]-[Color Balance]で調整すると次のような画像になります。

1

フラグは、
radar{reverse_color_give_flag}
です。



RADARCTF writeup Chars

  • Chars
  • Points: 100
  • Type: Crypto
  • Solves: 175
  • Download

Can you find then flag inside this matrix ?
ダウンロードしたファイルを解凍するとflag.txtができます。次のようなテキストデータです。
cRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RmRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRFRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRkRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRYRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRXRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRJRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRR7RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRYRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRR2RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRcRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRlRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRR9RRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRZRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRnRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRlRRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRcRRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRlRRRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRR9RRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRjRRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRaRRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRGRRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRFRRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRyRRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRXRRRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRR2RRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRdRRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRpRRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRdRRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRmRRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRVRRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRfRRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRZRRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRmRRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRxRRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRhRRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRZRR
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR3R
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR0
左上から斜め方向に文字を抽出すると次のような文字列になります。
cmFkYXJ7Y2hhcl9hZnRlcl9jaGFyX2dpdmVfZmxhZ30
これをBASE64でデコードするとフラグになります。
フラグは、
radar{char_after_char_give_flag}

RADARCTF writeup MD5Play2

  • MD5Play2
  • Points: 100
  • Type: Web
  • Solves: 159
  • Download
Just understand the code ;)

--------------------------------------------
Challenge's URL : 
http://blackfoxs.org/radar/md5play
URLにアクセスするとphpのソースコードが表示されます。
<?php
if(!isset($_GET['md5'])){die(highlight_file(__FILE__));}
if (isset($_GET['md5']) and strlen($_GET['md5']) == 3 and !is_numeric($_GET['md5'])){
    $md5=$_GET['md5'];
    if (floatval($md5)==md5($md5)){
        die(highlight_file("flag.php"));
    }else{
        echo htmlspecialchars($md5)."!=",md5($md5);
    }
}else{die(highlight_file(__FILE__));}
?> 1
GETパラメータのmd5が3文字で数値ではなくmd5のハッシュ値の先頭が数字でなければフラグが表示されそうです。eeeのMD5ハッシュ値はd2f2297d6e829cd3493aa7de4416a18fですのでeeeを指定してみます。
<?php
$flag='radar{s0m3_bug5_1s_fun}';
?> 1
フラグは、
radar{s0m3_bug5_1s_fun}

RADARCTF writeup Random

  • Random
  • Points: 400
  • Type: Crypto & RE
  • Solves: 132
  • Download
Oh no !
We encoded the flag but we don't know how to decode it ..
We attach the encode php code , try to reverse it and decode the flag
ファイルを解凍すると暗号化されたテキストデータとphpの暗号化プログラムができます。phpプログラムの処理内容は、乱数を生成して入力文字列のASCIIコードから減算し最後に乱数を暗号化文字列に付加していますので、次のPythonプログラムで容易に復号できます。
f = open('flag.txt')
s = f.read()
f.close()
a = s.split('.')
randkey = int(chr(int(a[-1]) - 49))
print(randkey)
flag = ''
for c in a:
flag += chr(int(c) + randkey)
print(flag)
実行すると次の結果が得られます。
$ python aaa.py 
5
radar{rand_is_not_good_idea_lol}k
フラグは、
radar{rand_is_not_good_idea_lol}
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