myfirstCTF writeup === 我只會寫水題qq by.ニオ 因為code部分應該會被擋到所以以下是原文(hackmd)網址 https://hackmd.io/@NeoDoggy/mfctf2021 --- ### welcome 猜數字通靈，把這串輸入到那ㄍ東西裡面 ```=1 2025830455298 ``` ```=1 flag=忘惹 ``` --- ### copy&paste 在html中會看到一個叫做f14g.php的檔案 再加上截圖 ![](https://i.imgur.com/AWqxJ1O.png) 大致上可以推出flag 然後這題我一直送F1aG結果是f1aG 哭啊我的first blood ```=1 flag=AIS3{Re33Ee3E33e3eEEe3eE3El11I1l1i11y_lo0O0oo00o00oOC0OOoo00o0Oo0O0o0Ooo0Oo0oo0Oo0OOOO000OO0ng_f1aG} ``` --- ### covid-19 CSY orz 用以下這兩個code可以print出flag ```cpp=1 char target[26]{0x41, 0x48, 0x51, 0x30, 0x7f, 0x30, 0x31, 0x33, 0x71, 0x56, 0x62, 0x3b, 0x61, 0x3e, 0x72, 0x78, 0x23, 0x25, 0x60, 0x4c, 0x79, 0x21, 0x23, 0x7c, 0x65, 0x00}; ``` ```cpp=1 void check(char *flag) { long long b = 1; for(int i = 0; i < 25; i++){ b = b & (((flag[i] ^ i)) == target[i]); } } ``` ```=1 flag=AIS3{574y_h0m3|w34r_m45k} ``` --- ### yuki OS:108新課綱w這題時事題 總之我是foremost flag.png後裡面的zip檔打開還就有了 flag: ![](https://i.imgur.com/OTDvdQS.png) 到底為什麼會有中文ㄉflag www --- ### Judgment 總之他在玩undertell的梗 寫這題時我比較無腦 直接建表 但是建表會有碰撞 所以要手動修正 ```python=1 from hashlib import sha256 import string flag = '' cand = string.ascii_letters + string.digits + '_{}' charset = string.printable[:93] enc = '' for c in flag: assert(c in cand) enc += charset[int(sha256(c.encode()).hexdigest(), 16) % len(charset)] print(enc) ``` ```python=1 flag= ')g;Fk@>2g;2V2J?d5G3_8V2<dR2i5GZ@<?2)g\j_2V&?2;@[F@ek2_3"=k&;2)\F2J9LL4g[W2"[2<)RZ23@<?2elFZ?2=@jZ23@=F2Yi52;lL5Vj2J?2J8\e@eW23e2lF330' main= 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890_{}' table=')J%jk_F_g(<VV[L7=&;>8Xy>Y5dq<<?}rl@T=94e"*_\ZG5F=kRt3GFV_We)ki2k0' ans='' for i in flag: t=0 for x in table: if i==x: ans+=main[t] break t+=1 print(ans) ``` 只有這樣會print出 ```=1 AISGEiT_IS_L_BeaZt1FUL_Kay_0ZtsiKe_AIrDF_LRe_SiNGinE_F1oQERS_ArG_BlOOmIN6_oN_KAys_1iKe_nhGse_QiDs_1iQG_Y0Z_ShOZLD_Be_BUrnin6_1n_hG11} ``` 顯然他不是flag，所以我叫出undertale來看看 ```=1 it's a beautiful day outside, birds are singing, flowers are blooming... on days like these, kids like you... should be burning in hell. ``` 手動修正一下 ```=1 AIS3{iT_IS_4_BeaZt1FUL_Kay_0ZtsiKe_AIrDF_LRe_SiNGinE_F1oQERS_ArG_BlOOmIN6_oN_KAys_1iKe_nhGse_QiDs_1iQG_Y0Z_ShOZLD_Be_BUrnin6_1n_hG11} ``` 完成 --- ### piano 應該是反組譯 但是我沒完成就結束了ww ###### tags: ais3,mfctf,ctf