Local Authority

link: https://play.picoctf.org/practice/challenge/278

題目

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

連結

website

解法

這題的 like 數超高!

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

連我寫完也送了一個 like 給他呢 wwww

這題雖然 100 points,但實際上絕對不值,因為真的太太太太簡單了!

這也象徵著再打 CTF 時千萬不能有分數迷思,一定要審題一下,跟考大考一樣 www

我們就來解這題!

首先打開網站:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

然後打開 dev-tools:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

打 CTF 的好習慣,正確說是進行紅隊時的好習慣:偵查、偵查、再偵查。

再打 Web 時,看到 input 就是會興奮,因為這代表其有洞可以鑽,雖然不知道這個洞會鑽出什麼,但是就鑽鑽看。

先看一下原始網頁碼:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

這邊 login 會送到 login.php,那麼就會是跟後面的 DB 進行交互。

我們就先試試看 sql injection 的做法進行盲注看看會發生什麼事情:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

密碼部分我打上 1=1 --,我就先預設他是 MySQL 的語法。

然後送出後看到:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

往右一瞥發現多了個 js ,我們再繼續看一下:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

有程式 sense 的應該都清楚了

真的不要以為這件事情是不會發生的!

之前看過有內部系統,就是這樣寫的

然後就把東西輸入吧:

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

密碼我就是用 strongPassword098765

最後就

Image Not Showing Possible Reasons
  • The image was uploaded to a note which you don't have access to
  • The note which the image was originally uploaded to has been deleted
Learn More →

結案!

結語

這題好適合作為給學生破題使用,因為實在是太簡單了。

但是卻是需要一點點好習慣才能變得簡單!

不然你在第一頁做分析做到死大概也得不出結果。

So,開打前先偵查,摸清楚所有情報,是重要的!