この大会は2020/3/22 2:00(JST)～2020/3/23 2:00(JST)に開催されました。
今回もチームで参戦。結果は1972点で429チーム中61位でした。
自分で解けた問題をWriteupとして書いておきます。
Welcome To Securinets !
Discordに入り、#generalチャネルのメッセージを見ると、フラグが書いてあった。
Securinets{PreQu@l$_2K20}
ASCII ART 0 (Misc)
$ nc 52.73.40.215 1337 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! ____ ____ _ _ _ __ __| _ \ | _ \ | | __(_)| |__ \ \ /\ / /| |_) || |_) || |/ /| || '_ \ \ V V / | _ < | _ < | < | || |_) | \_/\_/ |_| \_\|_| \_\|_|\_\|_||_.__/ >wRRkib Too late... $ nc 52.73.40.215 1337 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! ___ _ __ __ ___ ( _ ) | |__ __\ \/ / _ __ / __| / _ \ | |\ \ / / \ / | '__| \__ \| (_) || | \ V / / \ | | |___/ \___/ |_| \_/ /_/\_\|_| >s8lvXr Too late... $ nc 52.73.40.215 1337 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! _ _ __ __ _ _ _____ ____ _ _ | \ | |\ \/ /| || | |___ / |_ /| | | || \| | \ / | || |_ |_ \ / / | |_| || |\ | / \ |__ _| ___) | /___| \__,_||_| \_|/_/\_\ |_| |____/ >zuNX43 Too late... $ nc 52.73.40.215 1337 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! ____ ___ __ __ __ _ | _ \ _ __ / _ \ \ \ / / __ _ / _` || |_) || '__|| | | | \ \ /\ / / / _` | | (_| || _ < | | | |_| | \ V V / | (_| | \__, ||_| \_\|_| \___/ \_/\_/ \__, | |___/ |_| >gRr0Wq Too late... $ nc 52.73.40.215 1337 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! _ ____ _ _ __ _ __ ___ | |_ / ___| | |__ | '_ \ | '_ \ / _ \| __|\___ \ | '_ \ | |_) || |_) || __/| |_ ___) || | | | | .__/ | .__/ \___| \__||____/ |_| |_| |_| |_| >ppetSh Too late... $ nc 52.73.40.215 1337 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! ___ _ ____ __ __ ( _ ) __| | ___ | _ \ __ __\ \ / / / _ \ / _` | / _ \| |_) |\ \/ / \ \ /\ / / | (_) || (_| || __/| _ < > < \ V V / \___/ \__,_| \___||_| \_\/_/\_\ \_/\_/ >8deRxW Too late...
アスキーアートの文字を答えていく必要があるが、手入力では間に合わない。なるべく文字の形式を識別できるようデータを取り、辞書として持っておき、比較して対応する文字を答えていく。
import socket letters = { ''' _ / | | | | | |_| ''': '1', ''' ____ |___ \ __) | / __/ |_____| ''': '2', ''' _____ |___ / |_ \ ___) | |____/ ''': '3', ''' _ _ | || | | || |_ |__ _| |_| ''': '4', ''' ____ | ___| |___ \ ___) | |____/ ''': '5', ''' __ / /_ | '_ \ | (_) | \___/ ''': '6', ''' _____ |___ | / / / / /_/ ''': '7', ''' ___ ( _ ) / _ \ | (_) | \___/ ''': '8', ''' ___ / _ \ | (_) | \__, | /_/ ''': '9', ''' _ / \ / _ \ / ___ \ /_/ \_\\ ''': 'A', ''' ____ | __ ) | _ \ | |_) | |____/ ''': 'B', ''' ____ / ___| | | | |___ \____| ''': 'C', ''' ____ | _ \ | | | | | |_| | |____/ ''': 'D', ''' _____ | ____| | _| | |___ |_____| ''': 'E', ''' _____ | ___| | |_ | _| |_| ''': 'F', ''' ____ / ___| | | _ | |_| | \____| ''': 'G', ''' _ _ | | | | | |_| | | _ | |_| |_| ''': 'H', ''' ___ |_ _| | | | | |___| ''': 'I', ''' _ | | _ | | | |_| | \___/ ''': 'J', ''' _ __ | |/ / | ' / | . \ |_|\_\\ ''': 'K', ''' _ | | | | | |___ |_____| ''': 'L', ''' __ __ | \/ | | |\/| | | | | | |_| |_| ''': 'M', ''' _ _ | \ | | | \| | | |\ | |_| \_| ''': 'N', ''' ___ / _ \ | | | | | |_| | \___/ ''': 'O', ''' ____ | _ \ | |_) | | __/ |_| ''': 'P', ''' ___ / _ \ | | | | | |_| | \__\_\\ ''': 'Q', ''' ____ | _ \ | |_) | | _ < |_| \_\\ ''': 'R', ''' ____ / ___| \___ \ ___) | |____/ ''': 'S', ''' _____ |_ _| | | | | |_| ''': 'T', ''' _ _ | | | | | | | | | |_| | \___/ ''': 'U', '''__ __ \ \ / / \ \ / / \ V / \_/ ''': 'V', '''__ __ \ \ / / \ \ /\ / / \ V V / \_/\_/ ''': 'W', '''__ __ \ \/ / \ / / \ /_/\_\\ ''': 'X', '''__ __ \ \ / / \ V / | | |_| ''': 'Y', ''' _____ |__ / / / / /_ /____| ''': 'Z', ''' __ _ / _` | | (_| | \__,_| ''': 'a', ''' _ | |__ | '_ \ | |_) | |_.__/ ''': 'b', ''' ___ / __| | (__ \___| ''': 'c', ''' _ __| | / _` | | (_| | \__,_| ''': 'd', ''' ___ / _ \\ | __/ \___| ''': 'e', ''' __ / _| | |_ | _| |_| ''': 'f', ''' __ _ / _` | | (_| | \__, | |___/ ''': 'g', ''' _ | |__ | '_ \ | | | | |_| |_| ''': 'h', ''' _ (_) | | | | |_| ''': 'i', ''' _ (_) | | | | _/ | |__/ ''': 'j', ''' _ | | __ | |/ / | < |_|\_\\ ''': 'k', ''' _ | | | | | | |_| ''': 'l', ''' _ __ ___ | '_ ` _ \ | | | | | | |_| |_| |_| ''': 'm', ''' _ __ | '_ \ | | | | |_| |_| ''': 'n', ''' ___ / _ \ | (_) | \___/ ''': 'o', ''' _ __ | '_ \ | |_) | | .__/ |_| ''': 'p', ''' __ _ / _` | | (_| | \__, | |_|''': 'q', ''' _ __ | '__| | | |_| ''': 'r', ''' ___ / __| \__ \\ |___/ ''': 's', ''' _ | |_ | __| | |_ \__| ''': 't', ''' _ _ | | | | | |_| | \__,_| ''': 'u', ''' __ __ \ \ / / \ V / \_/ ''': 'v', ''' __ __ \ \ /\ / / \ V V / \_/\_/ ''': 'w', ''' __ __ \ \/ / > < /_/\_\\ ''': 'x', ''' _ _ | | | | | |_| | \__, | |___/ ''': 'y', ''' ____ |_ / / / /___| ''': 'z' } def recvuntil(s, tail): data = '' while True: if tail in data: return data data += s.recv(1) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(('52.73.40.215', 1337)) data = recvuntil(s, 'for me!\n').rstrip() print data for round in range(30): print 'Round %d' % (round + 1) data = recvuntil(s, '\n>') print data, data = data.split('\n')[:6] l = len(data[0]) i = 0 ans = '' while True: for j in range(3, 13): ascii = '\n'.join([data[k][:-1][i:i+j] for k in range(6)]) if ascii in letters: ans += letters[ascii] i += j break if i == l - 1: break print ans s.sendall(ans + '\n') data = recvuntil(s, '\n').rstrip() print data
実行結果は以下の通り。
Welcome to securinets CTF!
Let's play a game!
I'll tell u words words in ascii art and you should repeat them for me!
Round 1
_____ ___ _ __ __ ____ _
|_ _| / _ \ | |__ | \/ || _ \ | |_
| | | (_) || '_ \ | |\/| || | | || __|
| | \__, || |_) || | | || |_| || |_
|_| /_/ |_.__/ |_| |_||____/ \__|
> T9bMDt
Round 2
_____ _ _ _ _ __ __
|__ /| || | / || | __\ \ / / __ _
/ / | || |_ | || |/ / \ V / / _` |
/ /_ |__ _|| || < | | | (_| |
/____| |_| |_||_|\_\ |_| \__, |
|_|
> Z41kYq
Round 3
_____ _ ___ _____
| ___|| |__ |_ _| ____| ____| ____
| |_ | '_ \ | | |_ /| _| |_ /
| _| | | | | | | / / | |___ / /
|_| |_| |_||___|/___||_____|/___|
> FhIzEz
Round 4
__ __ ___ _ __ __ _ _ _
| \/ | / _ \ | | \ \ / / __| || | | |
| |\/| || | | || | \ \ / / / _` || |_| |
| | | || |_| || |___ \ V / | (_| || _ |
|_| |_| \___/ |_____| \_/ \__,_||_| |_|
> MOLVdH
：
Round 30
_ _ ____ ___
| |__ / \ / ___| / _ \ _ __ _ __ ___
| '_ \ / _ \ | | _ | | | || '_ \ | '_ ` _ \
| |_) | / ___ \ | |_| || |_| || |_) || | | | | |
|_.__/ /_/ \_\ \____| \___/ | .__/ |_| |_| |_|
|_|
> bAGOpm
securinets{w3ll_d0n3_g00d!!}
securinets{w3ll_d0n3_g00d!!}
ASCII ART 1 (Misc)
$ nc 52.73.40.215 1338 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! __ _ _ / /_ _ | || | | '_ \ _| |_ | || |_ | (_) ||_ _||__ _| \___/ |_| |_| >10 Too late... $ nc 52.73.40.215 1338 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! ____ ___ |___ \ / _ \ __) | _____ | (_) | / __/ |_____| \__, | |_____| /_/ >-7 Too late... $ nc 52.73.40.215 1338 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! _ _____ / |__/\__|___ / | |\ / |_ \ | |/_ _\ ___) | |_| \/ |____/ >3 ____ __ | ___| / /_ |___ \ _____ | '_ \ ___) ||_____|| (_) | |____/ \___/ >-1 Too late... $ nc 52.73.40.215 1338 Welcome to securinets CTF! Let's play a game! I'll tell u words words in ascii art and you should repeat them for me! _____ ____ |___ | _ |___ \ / / _| |_ __) | / / |_ _| / __/ /_/ |_| |_____| >9 __ __ _____ / /_ / /|___ / | '_ \ / / |_ \ | (_) | / / ___) | \___/ /_/ |____/ >2 _____ __ |___ / __/\__ / /_ |_ \ \ /| '_ \ ___) |/_ _\| (_) | |____/ \/ \___/ >18 _____ __ _____ |___ | / /|___ / / / / / |_ \ / / / / ___) | /_/ /_/ |____/ >2 Too late...
今度も ASCII ART 0 と同じようにして計算だけすればよい。
import socket letters = { ''' _ / | | | | | |_| ''': '1', ''' ____ |___ \ __) | / __/ |_____| ''': '2', ''' _____ |___ / |_ \ ___) | |____/ ''': '3', ''' _ _ | || | | || |_ |__ _| |_| ''': '4', ''' ____ | ___| |___ \ ___) | |____/ ''': '5', ''' __ / /_ | '_ \ | (_) | \___/ ''': '6', ''' _____ |___ | / / / / /_/ ''': '7', ''' ___ ( _ ) / _ \ | (_) | \___/ ''': '8', ''' ___ / _ \ | (_) | \__, | /_/ ''': '9', ''' _ _| |_ |_ _| |_| ''': '+', ''' _____ |_____| ''': '-', ''' __/\__ \ / /_ _\\ \/ ''': '*', ''' __ / / / / / / /_/ ''': '/' } def recvuntil(s, tail): data = '' while True: if tail in data: return data data += s.recv(1) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(('52.73.40.215', 1338)) data = recvuntil(s, 'for me!\n').rstrip() print data for round in range(100): print 'Round %d' % (round + 1) data = recvuntil(s, '\n>') print data, data = data.split('\n')[:6] l = len(data[0]) i = 0 ans = '' while True: for j in range(3, 13): ascii = '\n'.join([data[k][:-1][i:i+j] for k in range(6)]) if ascii in letters: ans += letters[ascii] i += j break if i == l - 1: break ans = str(eval(ans)) print ans s.sendall(ans + '\n') data = recvuntil(s, '\n').rstrip() print data
実行結果は以下の通り。
Welcome to securinets CTF!
Let's play a game!
I'll tell u words words in ascii art and you should repeat them for me!
Round 1
____ _ _
| ___| _ | || |
|___ \ _| |_ | || |_
___) ||_ _||__ _|
|____/ |_| |_|
> 9
Round 2
_ _ ___
| || | / _ \
| || |_ _____ | (_) |
|__ _||_____| \__, |
|_| /_/
> -5
Round 3
_ _ ____
| || | |___ \
| || |_ _____ __) |
|__ _||_____| / __/
|_| |_____|
> 2
Round 4
___ _ _
/ _ \ _ | || |
| (_) | _| |_ | || |_
\__, ||_ _||__ _|
/_/ |_| |_|
> 13
Round 5
____ _
| ___| / |
|___ \ _____ | |
___) ||_____|| |
|____/ |_|
> 4
：
Round 100
_ ___
/ |__/\__ ( _ )
| |\ / / _ \
| |/_ _\| (_) |
|_| \/ \___/
> 8
securinets{th1s_w4s_g00d_r1ght??}
securinets{th1s_w4s_g00d_r1ght??}
