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Rhel ftp11/17/2023 All requests from unprivileged child processes are distrusted by the parent process - Communication with child processes are received over a socket, and the validity of any information from child processes is checked before being acted on.This allows the privileged, parent process to be as small as possible and handle relatively few tasks. All operations requiring elevated privileges are handled by a small parent process - Much like the Apache HTTP Server, vsftpd launches unprivileged child processes to handle incoming connections.Child processes handle direct interaction with the FTP clients and run with as close to no privileges as possible. The parent process runs with the least privileges required - The parent process dynamically calculates the level of privileges it requires to minimize the level of risk.Use of these security practices has the following effect on how vsftpd deals with requests: This disallows any potential malicious hacker activities for any directories not contained below the new root directory. For example, if the directory /var/ftp/ is the primary shared directory, vsftpd reassigns /var/ftp/ to the new root directory, known as /. Most processes run in a chroot jail - Whenever possible, processes are change-rooted to the directory being shared this directory is then considered a chroot jail.Tasks requiring elevated privileges are handled by processes with the minimal privilege necessary - By leveraging compatibilities found in the libcap library, tasks that usually require full root privileges can be executed more safely from a less privileged process.Strong separation of privileged and non-privileged processes - Separate processes handle different tasks, and each of these processes run with the minimal privileges required for the task.The security model used by vsftpd has three primary aspects: vsftpd is the only stand-alone FTP server distributed with Red Hat Enterprise Linux, due to its ability to handle large numbers of connections efficiently and securely. The Very Secure FTP Daemon ( vsftpd) is designed from the ground up to be fast, stable, and, most importantly, secure. You can reduce the number of open ports on a server by limiting the range of unprivileged ports on the FTP server. While passive mode resolves issues for client-side firewall interference with data connections, it can complicate administration of the server-side firewall. The client then connects to that port on the server to download the requested information. When requesting data from the server, the FTP client indicates it wants to access the data in passive mode and the server provides the IP address and a random, unprivileged port (greater than 1024) on the server. passive mode - Passive mode, like active mode, is initiated by the FTP client application.Because these client-side firewalls often deny incoming connections from active mode FTP servers, passive mode was devised. With the growth of insecure networks, such as the Internet, the use of firewalls to protect client machines is now prevalent. This arrangement means that the client machine must be allowed to accept connections over any port above 1024. When an active mode data transfer is initiated by the FTP client, the server opens a connection from port 20 on the server to the IP address and a random, unprivileged port (greater than 1024) specified by the client. active mode - Active mode is the original method used by the FTP protocol for transferring data to the client application.The port number for data connections, and the way in which data connections are initialized, vary depending upon whether the client requests the data in active or passive mode. ![]() ![]() Any data requested from the server is returned to the client via a data port. ![]() This port is used to issue all commands to the server. When an FTP client application initiates a connection to an FTP server, it opens port 21 on the server - known as the command port. Unlike most protocols used on the Internet, FTP requires multiple network ports to work properly. System administrators, therefore, should be aware of the FTP protocol’s unique characteristics. However, because FTP is so prevalent on the Internet, it is often required to share files to the public. It allows users to access files on remote systems using a standard set of simple commands. Its purpose is to reliably transfer files between computer hosts on a network without requiring the user to log directly into the remote host or have knowledge of how to use the remote system. File Transfer Protocol (FTP) is one of the oldest and most commonly used protocols found on the Internet today.
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