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Articles taggués ‘ssh’

Configuration d’un serveur dédié de A à Z

15/12/2018 Comments off

Installation, configuration et administration d’un serveur dédié

debianCes tutoriaux ont été réalisés sous Debian (versions Etch 4.0 et Lenny 5.0) mais peuvent être transposés à d’autres distributions Linux, notamment Ubuntu. Ils sont applicables aux serveurs dédiés 1&1, Dedibox, OVH, Amen, et bien d’autres.

warning Tous les tutoriaux sont basés sur un serveur nommé test.alsacreations.com pour lequel nous disposons d’un utilisateur dew et d’un accès root (super-administrateur), chacun avec leur propre mot de passe.

Nous partons de l’idée d’obtenir un serveur web avec tout ce qu’il faut pour héberger plusieurs domaines et sites. Vous pouvez tout configurer à la main ou bien faire confiance à un panel d’administration.

Liste complète sans panel web

idee Ces tutoriaux conviennent à l’installation complète d’un serveur

  1. Première connexion : SSH, accès root et bases
  2. Apache et PHP : le serveur web
  3. MySQL : les bases de données
  4. Proftpd : le serveur FTP
  5. Postfix : le serveur mail POP3 et SMTP
  6. Sauvegarde automatique : avec backup-manager et export FTP
  7. Sécurisation : les règles de base, un firewall avec iptables, fail2ban…
  8. Bind : exécuter le serveur DNS en chroot
  9. Monitoring : garder un oeil sur son serveur grâce à monit et logwatch
  10. Roundcube : un webmail léger et rapide

Liste complète avec panel d’administration DTC

dtclogo

idee Si vous choisissez d’installer le panel d’administration DTC, suivez ces tutoriels. DTC se chargera de la configuration du reste des services.

  1. Première connexion : SSH, accès root et bases
  2. Bind : exécuter le serveur DNS en chroot
  3. Sécurisation : les règles de base, un firewall avec iptables, fail2ban…
  4. Panel DTC : pour installer et gérer les services web, ftp, mysql, e-mail, dns…
  5. Monitoring : garder un oeil sur son serveur grâce à monit et logwatch
  6. Sauvegarde automatique : backup-manager et export FTP
  7. Roundcube : un webmail léger et rapide

Attention : nous préconisons désormais l’utilisation du panel ISPConfig, en lieu et place du panel DTC. Il est tout aussi simple à installer et à utiliser. Veuillez vous référer à sa documentation.

How To Use Port Knocking to Hide your SSH Daemon from Attackers on Ubuntu

10/12/2018 Comments off

Introduction

Servers, by definition, are implemented as a means of providing services and making applications and resources accessible to users. However, any computer connected to the internet is inevitably targeted by malicious users and scripts hoping to take advantage of security vulnerabilities.

Firewalls exist and should be used to block access on ports not being utilized by a service, but there is still the question of what to do about services that you want access to, but do not want to expose to everybody. You want access when you need it, but want it blocked off otherwise.

Port knocking is one method of obscuring the services that you have running on your machine. It allows your firewall to protect your services until you ask for a port to be opened through a specific sequence of network traffic.

In this guide, we will discuss how to implement port knocking as a method of obscuring your SSH daemon on an Ubuntu 12.04 VPS using the knockd package.

Note: This tutorial covers IPv4 security. In Linux, IPv6 security is maintained separately from IPv4. For example, « iptables » only maintains firewall rules for IPv4 addresses but it has an IPv6 counterpart called « ip6tables », which can be used to maintain firewall rules for IPv6 network addresses.

If your VPS is configured for IPv6, please remember to secure both your IPv4 and IPv6 network interfaces with the appropriate tools. For more information about IPv6 tools, refer to this guide: How To Configure Tools to Use IPv6 on a Linux VPS

Lire la suite…

How To Configure Port Knocking Using Only IPTables on an Ubuntu VPS

10/12/2018 Comments off

Source: digitalocean.com

Introduction

Servers that are connected to the internet are subjected to all manners of attacks and probes by malicious users, scripts, and automated bots. It is sometimes a balancing act to secure your server from attacks without affecting legitimate access to your services and resources.

Certain types of services are meant to be visible and consumable to the public internet. An example of this is a web server. Other types of services are typically used by only the system administrator or a select number of individuals and are not meant to be a public resource.

A concept known as port knocking is a way of shielding processes that fit into the latter description. Port knocking works by covering the ports associated with a process behind a firewall until a specific, predetermined sequence of network activity occurs. At this point, the port knocking service reconfigures the firewall to allow access to the protected application.

In a previous article, we discussed how to enable port knocking through a specially designed port knocking service. In this article, we will discuss an alternative method of configuring port knocking.

This method does not rely on an external application to alter the firewall rules. Instead, the iptables firewall can take advantage of a state-tracking module called « recent » to do all of this within the firewall rules themselves.

We will be configuring this on an Ubuntu 12.04 droplet, but any kind of Linux server should operate in a similar manner.

Note: This tutorial covers IPv4 security. In Linux, IPv6 security is maintained separately from IPv4. For example, « iptables » only maintains firewall rules for IPv4 addresses but it has an IPv6 counterpart called « ip6tables », which can be used to maintain firewall rules for IPv6 network addresses.

If your VPS is configured for IPv6, please remember to secure both your IPv4 and IPv6 network interfaces with the appropriate tools. For more information about IPv6 tools, refer to this guide: How To Configure Tools to Use IPv6 on a Linux VPS

Lire la suite…

How to Setup Reverse SSH Tunnel on Linux

03/12/2018 Comments off

Reverse SSH is a technique that can be used to access systems (that are behind a firewall) from the outside world.

As you already know SSH is a network protocol that supports cryptographic communication between network nodes. Using this protocol, you can do a secure remote login, secure copy from/to a remote machine etc.

You’ll typically do the following to connect to a remote server securely using ssh command.

$ ssh [your-account-login]@[server-ip]

What is Reverse SSH?

SSH is very good tool to access remote machine or server securely. But, the problem arises when you try to connect to a remote server which is behind a firewall and this firewall denies any incoming connection or data transfer request that has no prior outgoing request. This means that only those connections would be allowed which are initiated by the remote server machine. This is a real problem for those who want to access this server machine remotely. Lire la suite…

Filtrer les connexions ssh

01/12/2018 Comments off

Portier SSH

Si vous possédez un serveur avec ssh opérationnel, vous ne serez pas long à avoir des messages tels que ceux ci dans le fichier /var/log/auth.log:

...
Mar 11 12:48:21 serv sshd[12956]: Failed password for invalid user root from 64.71.148.162 port 47270 ssh2
Mar 11 15:45:04 serv sshd[6954]: Did not receive identification string from 210.21.30.72
Mar 11 15:46:48 serv sshd[7041]: Did not receive identification string from 81.93.188.5
Mar 11 15:47:50 serv sshd[7106]: User root from 210.21.30.72 not allowed because none of user s groups are listed in AllowGroups
Mar 11 15:47:50 serv sshd[7106]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=210.21.30.72  user=root
Mar 11 15:47:52 serv sshd[7106]: Failed password for invalid user root from 210.21.30.72 port 54346 ssh2
Mar 11 15:49:33 serv sshd[7241]: User root from 81.93.188.5 not allowed because none of user s groups are listed in AllowGroups
Mar 11 15:49:33 serv sshd[7241]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=81.93.188.5  user=root
Mar 11 15:49:35 serv sshd[7241]: Failed password for invalid user root from 81.93.188.5 port 44663 ssh2
Mar 12 00:51:18 serv sshd[22229]: User root from host.ongamemarketing.com not allowed because none of user s groups are listed in AllowGroups
Mar 12 00:51:18 serv sshd[22229]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=host.ongamemarketing.com  user=root
Mar 12 00:51:20 serv sshd[22229]: Failed password for invalid user root from 174.133.12.130 port 48089 ssh2
Mar 12 00:51:22 serv sshd[22236]: User root from host.ongamemarketing.com not allowed because none of user s groups are listed in AllowGroups
Mar 12 00:51:22 serv sshd[22236]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=host.ongamemarketing.com  user=root
Mar 12 00:51:24 serv sshd[22236]: Failed password for invalid user root from 174.133.12.130 port 48521 ssh2
Mar 12 01:47:10 serv sshd[30827]: Did not receive identification string from 114.200.199.144
Mar 12 01:53:17 serv sshd[31227]: Invalid user staff from 114.200.199.144
Mar 12 01:53:17 serv sshd[31227]: pam_unix(sshd:auth): check pass; user unknown
Mar 12 01:53:17 serv sshd[31227]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=114.200.199.144
Mar 12 01:53:19 serv sshd[31227]: Failed password for invalid user staff from 114.200.199.144 port 35343 ssh2
Mar 12 01:53:27 serv sshd[31234]: Invalid user sales from 114.200.199.144
...

sshsessionforwardingVous avez besoin de pouvoir vous connecter en ssh depuis le réseau local, depuis l’extérieur, mais vous voulez limiter les risques. Il existe plusieurs solutions, qui peuvent être cumulées: Lire la suite…

Categories: Réseau Tags: , ,