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。
フラグは、
radar{reverse_color_give_flag}です。
RADARCTF
フラグは、
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。
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。cRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRmRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRFRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRkRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRYRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRXRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRJRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR7RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRYRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR2RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRcRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRlRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR9RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRZRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRnRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRlRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRcRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRlRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR9RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRjRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRaRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRGRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRFRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRyRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRXRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR2RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRdRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRpRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRdRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRmRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRVRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRfRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRZRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRmRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRxRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRhRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRZRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR3RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR0
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}
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。
<?phpif(!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}
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。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
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.py5radar{rand_is_not_good_idea_lol}k
フラグは、
radar{rand_is_not_good_idea_lol}
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