CTF introductory learning (WEB direction)

Brush questions Edge learning To sum up

1.Robots agreement

“Robots agreement ” Our English full name is Robots Exclusion Protocol, Robot exclusion protocol , It's also called crawler protocol 、 Robot protocol , It refers to a text file placed in the root directory of the website by the website owner , namely robots.txt, Tell the search engine's webbot （ Or web crawler 、 Web spider ） Which pages should not be crawled , Which pages can be crawled , In essence, it is an interactive way between the visited website and the search engine .

robots.txt A file is a text file , Use any common text editor , such as Windows The system is installed Notepad, You can create and edit it [1] .robots.txt It's an agreement , Not an order .robots.txt It's the first file to view when visiting a website in a search engine .robots.txt Files tell the spider what files can be viewed on the server .

When a search spider visits a site , It will first check if the root directory of the site exists robots.txt, If there is , The search robot will follow the contents of the file to determine the scope of access ; If the file does not exist , All search spiders will be able to access all pages on the site that are not password protected . Baidu official suggestion , Only if your website contains content that you do not want to be included by search engines , To use robots.txt file . If you want the search engine to include all the content on the website , Do not create robots.txt file .

If the website is regarded as a room in the hotel ,robots.txt It was hung by the master at the door of the room “ Do not disturb. ” or “ Welcome to clean ” Your sign . This file tells the visiting search engine which rooms can be entered and visited , Which rooms are for storing valuables , Or it may involve the privacy of residents and visitors and not open to search engines . but robots.txt It's not an order , It's not a firewall , Just as the gatekeeper can't stop malicious intruders such as thieves .

The following is a simple application of the protocol ：


Visit the topic scenario robots.txt The file shows flag Path location ,
Then visit the topic scene path flag_ls_h3re.php obtain flag.

2. Backup file

frequently-used Backup file The suffix of is “.git” 、“.svn”、“.swp”、“.~”、“.bak”、“.bash_history”、“.bkf” etc. . In the input index. php.bak After downloading the file .

After downloading the backup file , take "bak" Format changed to "txt" You can see the script code information in text format , It includes flag

3. sandwich biscuits （cookie）

Cookie Not its original intention “ cookie ” It means , It's a simple text file saved in the client , This file is associated with a specific Web Documents are linked together , Save the client's access to this Web The information in the document , When the client visits this again Web This information is available to the document when the document is created . because “Cookie” It has magical features that can be saved on the client , Therefore, it can help us realize the function of recording users' personal information , And all this doesn't have to use complex CGI Applications such as .

for instance , One Web The site may generate a unique ID, And then to Cookie The file format is kept on each user's machine . If you use a browser to access Web, You will see all saved on your hard disk Cookie. In this folder, each file is a file composed of “ name / value ” For the text file composed of , There is also a file that holds all the corresponding Web Site information . Everyone here Cookie The file is a simple and common text file . Through file name , You can see which Web The site is placed on the machine Cookie( Of course, the site information is also saved in the file )

Here are cookie Simple learning application of the protocol


F12 see Cookie Information can be seen in the prompt given by the title “look-here” value cookie.php The script file is added after the title scene path cookie.php Go to the next step .

The next question is “See the http response”. You need to check it here http Of response Information , Use wireshark Software package capture .

The title prompt is to view http Agreed response Field information , Then we can choose the second http（ The first is request）, Double click and click to get flag.