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SEC-T CTF 2019 Writeup

SEC-T CTF 2019 had been held from September 18th, 15:00 to 19th, 21:00 UTC. I played this CTF in zer0pts and we reached 6th place with 4485pts. It was a really nice CTF and I learned a lot. Thank you for hosting the CTF! [misc 79pts] sanit…

TokyoWesterns CTF 5th 2019 Writeup

TokyoWesterns CTF 5th 2019が日本時間で8/31 09:00から9/02 09:00まで開催されました。 私はチームHarekazeとして参加し、Harekazeは1481点を獲得して33位でした。 そのうち5問を私は解いたので、そのwriteupを書こうと思います。 [Pwn 78pts] nothing more…

angrをいろいろ使ってみる【yoshi-camp備忘録】

CTF

はじめに yoshikingがセキュリティキャンプに落ち、私もチューターに落ちたのでチームinsecureと阪大からの2人ほどで08/17と08/18にyoshi-campという名の勉強会を開いています。 やる場所が定まらなくて困っていたのですが、つてを辿って阪大の良いお部屋を…

RedpwnCTF 2019 Writeup

RedpwnCTF 2019 had been held from Aug 12th to 16th and I played this CTF in zer0pts. We got 4433pts and reached 29th place. I gained 3605pts, solving mostly pwn and some forensics, misc, crypto, rev challs. In this post I'll write only abo…

InterKosenCTF 2019で作問しました

はじめに 8月11日、12日に開かれたInterKosenCTF 2019でいくつか作問を担当しました。 今回は簡単な問題だけ出題するということで、CTF初心者だった頃を思い出しつつ、初心者の勉強になるような問題を心がけて作りました。 その結果、難易度を押さえつつ良い…

CyBRICS CTF 2019 Writeup

I played CyBRICS CTF 2019 in zer0pts. Our team got 386pts and reached 69th place. It's not a good result but I really enjoyed the CTF as there were many well-designed challenges. [Forensics 67pts] Disk Data [Cyber 50pts] QShell [Network 10…

2019年のpwn問を全部解くチャレンジ【前半戦】

CTF

後半戦: 2019年のpwn問を全部解くチャレンジ【後半戦】 - CTFするぞ まえがき (2019年3月記) 最近CTFに出るとそこそこ良い成績が残せる一方,チームのpwn担当として実力不足を感じています. そこで,pwn苦手意識を克服すべく本日2019年3月13日から,2019年…

ISITDTU CTF 2019 Quals Writeup

ISITDTU CTF 2019 took place from June 29th for 25 hours. I played this CTF in zer0pts and we reached the 10th place. Thank you for holding the CTF. I enjoyed it :-) [Pwn 395] iz_heap_lv1 [Pwn 908] Tokenizer [Pwn 738] babyshellcode [Cryptog…

Midnight Sun CTF 2019 Finals参加記

CTF

Midnight Sun CTF 2019 Finalにdcuaで参加し、14チーム中8位でした。 チームメンバーにpwnerがいたので私はrevとhardwareを中心に取り組みました。 いろんな人とお話できて楽しかったです。 取り組んだ問題たち:https://bitbucket.org/ptr-yudai/writeups/s…

HSCTF 6 Writeup

I played HSCTF 6 in yoshikingdom and our team reached 11th place. I didn't plan to play this CTF but @y05h1k1ng suggested us to play this one as a joke (not in ordinary team) because it was about to the end of the CTF. So, 11th place in ha…

Facebook CTF 2019 Writeup

Facebook CTF 2019 had been held from June 1st 00:00 UTC to June 2nd 00:00 UTC. I played this CTF as a member of zer0pts. We got 9372pts and reached 18th place. I solved several challs and gained 4718pts. The CTF was pretty hard but I reall…

ヒープ系問題におけるstdout / stderrを利用したメモリリーク

CTF

はじめに 数カ月前から始めた鬼のpwn特訓により最近CTFでもヒープ系問題に挑戦できるようになりつつあるのですが、たまにShow機能がない(=一見libcのアドレスがリークできない)ヒープ系問題が出ます。 HITCONのbabytcacheという問題のwriteupを読んでstdout…

SECCON Beginners CTF 2019のWriteup

5月25日(土)15:00から24時間開催されたSECCON Beginners CTF 2019にzer0ptsのメンバーで参加しました。 大会の存在をすっかり忘れていたので途中から参加しましたが、担当分野は無事全部解くことができました。 初心者向けながら典型とは外れたものもあり、…

Harekaze CTF 2019のWriteup

5月18日の15時から24時間Harekaze CTF 2019が開催されました。 私はチームYokosuka Hackersとして参加し、チーム全体で3060ptsを獲得して1位でした。 なんとフラグを通したのは2問だけという失態ですが、今回はみんなで情報共有して協力しながらという感じだ…

DEF CON CTF 2019 Qualifier Writeup

DEF CON CTF 2019 Qualfier had been held this weekend and I played this CTF with team dcua. We got 1347 in total and reached the 35th place. I enjoyed it but I'm not convinced the scoring system of speedrun challs. Anyway, the quality of th…

和暦 - SECCON 令和CTF Writeup

Pwnが1問だけあったのでやりました。 [Pwn 268pts] 和暦 説明文:西暦を和暦に変換してくれるよ サーバ:nc wareki-o-reiwa.seccon.jp 36294 64ビットバイナリがもらえます。 $ checksec wareki [*] 'wareki' Arch: 64 bits (little endian) NX: NX enabled …

*CTF (StarCTF) 2019 Writeup

This CTF took place from April 27th to 29th and I played this one as a member of zer0pts. We got 2570pts and reached the 36th place. Thank you for organizing the CTF. [Pwn 155] quicksort [Pwn 238] girlfriend [Crypto 206] babyprng [Crypto 2…

angstromCTF 2019 Writeup

I played angstromCTF 2019 Quals as a member of team zer0pts. It had been held for 1 week beggining on April 19th. We got 3730pts and reached the 8th place. I was mostly working on pwn challs but also solved another categories and got 1300p…

作った問題がASIS CTFに出題されていた話

CTF

追記[2019/04/24] この記事を見た運営の方から連絡があり、状況を丁寧に説明してくださいました。 私は説明が下手なので重要な部分だけを翻訳してそのまま書きます。 しばらく前に自称韓国国籍のCTFプレイヤーがCTFの作問を手伝うと申し出ました。 我々は彼…

CPCTF 2019に参加しました

はじめに 4月17日の13:30から19:30までCPCTFが開催されました。 東京工業大学デジタル創作同好会traPによるCTF+競プロで、東工大の新入生向けに開かれているっぽいです。 私は編入生なので新入生に含まれませんでしたが、ずっとオンサイトで参加していました…

Defense against Game Hackに参加しました【crackme解説】

はじめに 4月16日に大崎で開かれたninjastars様によるGhidraの勉強会に参加させていただきました。 なんかGhidra使いづらかったので途中から完全にida使ってました。すいません。 内容 内容は以下の三本立てでした。 チートの現状とninjastarsによる対策手法…

Midnightsun CTF 2019 Writeup

Midnightsun CTF 2019 took place from April 5th, 16:00 to April 6th, 16:00 UTC. This CTF is organized by HackingForSoju, a high level Swedish CTF team. I played this CTF as a member of team dcua. We got 7640pts in total and won the 1st plac…

Sunshine CTF 2019 Writeup

Sunshine CTF 2019 took place from 30 March, 9:00 AM to 31 March, 9:00 PM EST. I played this CTF in zer0pts and got 1350pts out of the 3255pts we gained. Thanks @SunshineCTF for holding a CTF. [Pwn 50] Return To Mania [Pwn 200] CyberRumble …

Securinets CTF Quals 2019 Writeup

Securinets CTF Quals 2019 took place from 24th March, 02:00 JST for 24 hours. Our new team zer0pts got 23393pts and stood 2nd place. I solved 9 challenges and got 7570pts. Thank you Securinets CTF for the great challs! [Foren 200pts] Easy …

Teaser CONFidence 2019 CTF Writeup

Teaser CONFidence 2019 CTF took place from 16 March, 11:00 to 17 March, 11:00 UTC. This CTF was organized by p4, a famous Polish team. Since my usual team members were busy, I played this CTF with the members of team Invaders. We got 762pt…

AeroCTF 2019 Writeup

I played AeroCTF as a member of team insecure and got 3411 points, which is worth reaching to the 14th place. I solved several challenges, some of them with the help of my team mates, and enjoyed the CTF. Thank you to the admin for holding…

BSidesSF CTF 2019 Writeup

I participated in BSidesSF CTF 2019 as insecure and got 540pts, reached to the 37th place. I also played TAMUctf and had been awake for 24 hours so unfortunately I spent much time on sleeping... And there were too many challenges to solve …

TAMUctf 19 Writeup

TAMUctf 19 had been held for nearly 2 weeks and I joined as insecure. My team got 19162pts, except for Pwn6 and Alt-F4 For Ops, and reached 16th place. There were so many challenges and I can't write about all of them. I enjoyed most of th…

_IO_str_overflowを使ったvtable改竄検知の回避手法

CTF

はじめに 論文みたいなタイトルになりましたが別に新しくも何ともありません。 趣味で勉強して面白かったので記事にしてみました。 さて、FILE構造体を利用したexploit手法としてFILE Structure Oriented Programmingがあります。 _IO_FILE_plus構造体のvtab…

FireShell CTF 2019 Writeup

FireShell CTF 2019 had been held in 26 and 27 Jan for 24 hours. Our team insecure got 1958pts and reached 16th place. There were so many challenges that I couldn't even check some of them. I'm going to write the solution for some challenge…