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{% endhint %} ## Basic Information The **File Transfer Protocol (FTP)** serves as a standard protocol for file transfer across a computer network between a server and a client.\ It is a **plain-text** protocol that uses as **new line character `0x0d 0x0a`** so sometimes you need to **connect using `telnet`** or **`nc -C`**. **Default Port:** 21 ``` PORT STATE SERVICE 21/tcp open ftp ``` ### Connections Active & Passive In **Active FTP** the FTP **client** first **initiates** the control **connection** from its port N to FTP Servers command port – port 21. The **client** then **listens** to port **N+1** and sends the port N+1 to FTP Server. FTP **Server** then **initiates** the data **connection**, from **its port M to the port N+1** of the FTP Client. But, if the FTP Client has a firewall setup that controls the incoming data connections from outside, then active FTP may be a problem. And, a feasible solution for that is Passive FTP. In **Passive FTP**, the client initiates the control connection from its port N to the port 21 of FTP Server. After this, the client issues a **passv comand**. The server then sends the client one of its port number M. And the **client** **initiates** the data **connection** from **its port P to port M** of the FTP Server. Source: [https://www.thesecuritybuddy.com/vulnerabilities/what-is-ftp-bounce-attack/](https://www.thesecuritybuddy.com/vulnerabilities/what-is-ftp-bounce-attack/) ### Connection debugging The **FTP** commands **`debug`** and **`trace`** can be used to see **how is the communication occurring**. ## Enumeration ### Banner Grabbing ```bash nc -vn 21 openssl s_client -connect crossfit.htb:21 -starttls ftp #Get certificate if any ``` ### Connect to FTP using starttls ``` lftp lftp :~> set ftp:ssl-force true lftp :~> set ssl:verify-certificate no lftp :~> connect 10.10.10.208 lftp 10.10.10.208:~> login Usage: login [] lftp 10.10.10.208:~> login username Password ``` ### Unauth enum With **nmap** ```bash sudo nmap -sV -p21 -sC -A 10.10.10.10 ``` You can us the commands `HELP` and `FEAT` to obtain some information of the FTP server: ``` HELP 214-The following commands are recognized (* =>'s unimplemented): 214-CWD XCWD CDUP XCUP SMNT* QUIT PORT PASV 214-EPRT EPSV ALLO* RNFR RNTO DELE MDTM RMD 214-XRMD MKD XMKD PWD XPWD SIZE SYST HELP 214-NOOP FEAT OPTS AUTH CCC* CONF* ENC* MIC* 214-PBSZ PROT TYPE STRU MODE RETR STOR STOU 214-APPE REST ABOR USER PASS ACCT* REIN* LIST 214-NLST STAT SITE MLSD MLST 214 Direct comments to root@drei.work FEAT 211-Features: PROT CCC PBSZ AUTH TLS MFF modify;UNIX.group;UNIX.mode; REST STREAM MLST modify*;perm*;size*;type*;unique*;UNIX.group*;UNIX.mode*;UNIX.owner*; UTF8 EPRT EPSV LANG en-US MDTM SSCN TVFS MFMT SIZE 211 End STAT #Info about the FTP server (version, configs, status...) ``` ### Anonymous login _anonymous : anonymous_\ &#xNAN;_anonymous :_\ &#xNAN;_ftp : ftp_ ```bash ftp >anonymous >anonymous >ls -a # List all files (even hidden) (yes, they could be hidden) >binary #Set transmission to binary instead of ascii >ascii #Set transmission to ascii instead of binary >bye #exit ``` ### [Brute force](../../generic-methodologies-and-resources/brute-force.md#ftp) Here you can find a nice list with default ftp credentials: [https://github.com/danielmiessler/SecLists/blob/master/Passwords/Default-Credentials/ftp-betterdefaultpasslist.txt](https://github.com/danielmiessler/SecLists/blob/master/Passwords/Default-Credentials/ftp-betterdefaultpasslist.txt) ### Automated Anon login and bounce FTP checks are perform by default by nmap with **-sC** option or: ```bash nmap --script ftp-* -p 21 ``` ## Browser connection You can connect to a FTP server using a browser (like Firefox) using a URL like: ```bash ftp://anonymous:anonymous@10.10.10.98 ``` Note that if a **web application** is sending data controlled by a user **directly to a FTP server** you can send double URL encode `%0d%0a` (in double URL encode this is `%250d%250a`) bytes and make the **FTP server perform arbitrary actions**. One of this possible arbitrary actions is to download content from a users controlled server, perform port scanning or try to talk to other plain-text based services (like http). ## Download all files from FTP ```bash wget -m ftp://anonymous:anonymous@10.10.10.98 #Donwload all wget -m --no-passive ftp://anonymous:anonymous@10.10.10.98 #Download all ``` If your user/password has special characters, the [following command](https://stackoverflow.com/a/113900/13647948) can be used: ```bash wget -r --user="USERNAME" --password="PASSWORD" ftp://server.com/ ``` ## Some FTP commands * **`USER username`** * **`PASS password`** * **`HELP`** The server indicates which commands are supported * **`PORT 127,0,0,1,0,80`** This will indicate the FTP server to establish a connection with the IP 127.0.0.1 in port 80 (_you need to put the 5th char as "0" and the 6th as the port in decimal or use the 5th and 6th to express the port in hex_). * **`EPRT |2|127.0.0.1|80|`** This will indicate the FTP server to establish a TCP connection (_indicated by "2"_) with the IP 127.0.0.1 in port 80. This command **supports IPv6**. * **`LIST`** This will send the list of files in current folder * **`LIST -R`** List recursively (if allowed by the server) * **`APPE /path/something.txt`** This will indicate the FTP to store the data received from a **passive** connection or from a **PORT/EPRT** connection to a file. If the filename exists, it will append the data. * **`STOR /path/something.txt`** Like `APPE` but it will overwrite the files * **`STOU /path/something.txt`** Like `APPE`, but if exists it won't do anything. * **`RETR /path/to/file`** A passive or a port connection must be establish. Then, the FTP server will send the indicated file through that connection * **`REST 6`** This will indicate the server that next time it send something using `RETR` it should start in the 6th byte. * **`TYPE i`** Set transfer to binary * **`PASV`** This will open a passive connection and will indicate the user were he can connects * **`PUT /tmp/file.txt`** Upload indicated file to the FTP ![](<../../.gitbook/assets/image (386).png>) ## FTPBounce attack Some FTP servers allow the command PORT. This command can be used to indicate to the server that you wants to connect to other FTP server at some port. Then, you can use this to scan which ports of a host are open through a FTP server. [**Learn here how to abuse a FTP server to scan ports.**](ftp-bounce-attack.md) You could also abuse this behaviour to make a FTP server interact with other protocols. You could **upload a file containing an HTTP request** and make the vulnerable FTP server **send it to an arbitrary HTTP server** (_maybe to add a new admin user?_) or even upload a FTP request and make the vulnerable FTP server download a file for a different FTP server.\ The theory is easy: 1. **Upload the request (inside a text file) to the vulnerable server.** Remember that if you want to talk with another HTTP or FTP server you need to change lines with `0x0d 0x0a` 2. **Use `REST X` to avoid sending the characters you don't want to send** (maybe to upload the request inside the file you needed to put some image header at the beginning) 3. **Use `PORT`to connect to the arbitrary server and service** 4. **Use `RETR`to send the saved request to the server.** Its highly probably that this **will throw an error like** _**Socket not writable**_ **because the connection doesn't last enough to send the data with `RETR`**. Suggestions to try to avoid that are: * If you are sending an HTTP request, **put the same request one after another** until **\~0.5MB** at least. Like this: {% file src="../../.gitbook/assets/posts.txt" %} posts.txt {% endfile %} * Try to **fill the request with "junk" data relative to the protocol** (talking to FTP maybe just junk commands or repeating the `RETR`instruction to get the file) * Just **fill the request with a lot of null characters or others** (divided on lines or not) Anyway, here you have an [old example about how to abuse this to make a FTP server download a file from a different FTP server.](ftp-bounce-download-2oftp-file.md) ## Filezilla Server Vulnerability **FileZilla** usually **binds** to **local** an **Administrative service** for the **FileZilla-Server** (port 14147). If you can create a **tunnel** from **your machine** to access this port, you can **connect** to **it** using a **blank password** and **create** a **new user** for the FTP service. ## Config files ``` ftpusers ftp.conf proftpd.conf vsftpd.conf ``` ### Post-Exploitation The default configuration of vsFTPd can be found in `/etc/vsftpd.conf`. In here, you could find some dangerous settings: * `anonymous_enable=YES` * `anon_upload_enable=YES` * `anon_mkdir_write_enable=YES` * `anon_root=/home/username/ftp` - Directory for anonymous. * `chown_uploads=YES` - Change ownership of anonymously uploaded files * `chown_username=username` - User who is given ownership of anonymously uploaded files * `local_enable=YES` - Enable local users to login * `no_anon_password=YES` - Do not ask anonymous for password * `write_enable=YES` - Allow commands: STOR, DELE, RNFR, RNTO, MKD, RMD, APPE, and SITE ### Shodan * `ftp` * `port:21` ## HackTricks Automatic Commands ``` Protocol_Name: FTP #Protocol Abbreviation if there is one. Port_Number: 21 #Comma separated if there is more than one. Protocol_Description: File Transfer Protocol #Protocol Abbreviation Spelled out Entry_1: Name: Notes Description: Notes for FTP Note: | Anonymous Login -bi <<< so that your put is done via binary wget --mirror 'ftp://ftp_user:UTDRSCH53c"$6hys@10.10.10.59' ^^to download all dirs and files wget --no-passive-ftp --mirror 'ftp://anonymous:anonymous@10.10.10.98' if PASV transfer is disabled https://book.hacktricks.xyz/pentesting/pentesting-ftp Entry_2: Name: Banner Grab Description: Grab FTP Banner via telnet Command: telnet -n {IP} 21 Entry_3: Name: Cert Grab Description: Grab FTP Certificate if existing Command: openssl s_client -connect {IP}:21 -starttls ftp Entry_4: Name: nmap ftp Description: Anon login and bounce FTP checks are performed Command: nmap --script ftp-* -p 21 {IP} Entry_5: Name: Browser Connection Description: Connect with Browser Note: ftp://anonymous:anonymous@{IP} Entry_6: Name: Hydra Brute Force Description: Need Username Command: hydra -t 1 -l {Username} -P {Big_Passwordlist} -vV {IP} ftp Entry_7: Name: consolesless mfs enumeration ftp Description: FTP enumeration without the need to run msfconsole Note: sourced from https://github.com/carlospolop/legion Command: msfconsole -q -x 'use auxiliary/scanner/ftp/anonymous; set RHOSTS {IP}; set RPORT 21; run; exit' && msfconsole -q -x 'use auxiliary/scanner/ftp/ftp_version; set RHOSTS {IP}; set RPORT 21; run; exit' && msfconsole -q -x 'use auxiliary/scanner/ftp/bison_ftp_traversal; set RHOSTS {IP}; set RPORT 21; run; exit' && msfconsole -q -x 'use auxiliary/scanner/ftp/colorado_ftp_traversal; set RHOSTS {IP}; set RPORT 21; run; exit' && msfconsole -q -x 'use auxiliary/scanner/ftp/titanftp_xcrc_traversal; set RHOSTS {IP}; set RPORT 21; run; exit' ``` {% hint style="success" %} Learn & practice AWS Hacking:

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