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ORC – Un réseau de stockage cloud, anonyme et décentralisé reposant sur Tor

02/11/2017 Comments off

Counterpoint Hackerspace, une bande de geeks localisée à Roswell dans l’état de Georgie aux États unis, a eu l’excellente idée de mettre au point un outil permettant de stocker sur Tor des fichiers, un peu à la manière d’un espace « cloud », mais avec tous les avantages que Tor peut apporter : anonymat, décentralisation et gestion par la communauté. Lire la suite…

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Categories: Logiciel, Sécurité, Système Tags: , ,

Linux: 20 Iptables Examples For New SysAdmins

28/09/2017 Comments off

According to the official project site:

netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack.

This Linux based firewall is controlled by the program called iptables to handles filtering for IPv4, and ip6tables handles filtering for IPv6. I strongly recommend that you first read our quick tutorial that explains how to configure a host-based firewall called Netfilter (iptables) under CentOS / RHEL / Fedora / Redhat Enterprise Linux. This post lists most simple iptables solutions required by a new Linux user to secure his or her Linux operating system from intruders.

IPTABLES Rules Example

  • Most of the actions listed in this post written with the assumption that they will be executed by the root user running the bash or any other modern shell. Do not type commands on the remote system as it will disconnect your access.
  • For demonstration purpose, I’ve used RHEL 6.x, but the following command should work with any modern Linux distro that use the netfliter.
  • It is NOT a tutorial on how to set iptables. See tutorial here. It is a quick cheat sheet to common iptables commands.

#1: Displaying the Status of Your Firewall

Type the following command as root:
# iptables -L -n -v
Sample outputs:

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Above output indicates that the firewall is not active. The following sample shows an active firewall:
# iptables -L -n -v
Sample outputs:

Chain INPUT (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 DROP       all  --  *      *       0.0.0.0/0            0.0.0.0/0           state INVALID
  394 43586 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
   93 17292 ACCEPT     all  --  br0    *       0.0.0.0/0            0.0.0.0/0
    1   142 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0

Chain FORWARD (policy DROP 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination
    0     0 ACCEPT     all  --  br0    br0     0.0.0.0/0            0.0.0.0/0
    0     0 DROP       all  --  *      *       0.0.0.0/0            0.0.0.0/0           state INVALID
    0     0 TCPMSS     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0           tcp flags:0x06/0x02 TCPMSS clamp to PMTU
    0     0 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
    0     0 wanin      all  --  vlan2  *       0.0.0.0/0            0.0.0.0/0
    0     0 wanout     all  --  *      vlan2   0.0.0.0/0            0.0.0.0/0
    0     0 ACCEPT     all  --  br0    *       0.0.0.0/0            0.0.0.0/0

Chain OUTPUT (policy ACCEPT 425 packets, 113K bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain wanin (1 references)
 pkts bytes target     prot opt in     out     source               destination

Chain wanout (1 references)
 pkts bytes target     prot opt in     out     source               destination

Where,

  • -L : List rules.
  • -v : Display detailed information. This option makes the list command show the interface name, the rule options, and the TOS masks. The packet and byte counters are also listed, with the suffix ‘K’, ‘M’ or ‘G’ for 1000, 1,000,000 and 1,000,000,000 multipliers respectively.
  • -n : Display IP address and port in numeric format. Do not use DNS to resolve names. This will speed up listing.

#1.1: To inspect firewall with line numbers, enter:

# iptables -n -L -v --line-numbers
Sample outputs:

Chain INPUT (policy DROP)
num  target     prot opt source               destination
1    DROP       all  --  0.0.0.0/0            0.0.0.0/0           state INVALID
2    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
3    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
4    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0

Chain FORWARD (policy DROP)
num  target     prot opt source               destination
1    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
2    DROP       all  --  0.0.0.0/0            0.0.0.0/0           state INVALID
3    TCPMSS     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp flags:0x06/0x02 TCPMSS clamp to PMTU
4    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
5    wanin      all  --  0.0.0.0/0            0.0.0.0/0
6    wanout     all  --  0.0.0.0/0            0.0.0.0/0
7    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

Chain wanin (1 references)
num  target     prot opt source               destination

Chain wanout (1 references)
num  target     prot opt source               destination

You can use line numbers to delete or insert new rules into the firewall.

#1.2: To display INPUT or OUTPUT chain rules, enter:

# iptables -L INPUT -n -v
# iptables -L OUTPUT -n -v --line-numbers

#2: Stop / Start / Restart the Firewall

If you are using CentOS / RHEL / Fedora Linux, enter:
# service iptables stop
# service iptables start
# service iptables restart

You can use the iptables command itself to stop the firewall and delete all rules:
# iptables -F
# iptables -X
# iptables -t nat -F
# iptables -t nat -X
# iptables -t mangle -F
# iptables -t mangle -X
# iptables -P INPUT ACCEPT
# iptables -P OUTPUT ACCEPT
# iptables -P FORWARD ACCEPT

Where,

  • -F : Deleting (flushing) all the rules.
  • -X : Delete chain.
  • -t table_name : Select table (called nat or mangle) and delete/flush rules.
  • -P : Set the default policy (such as DROP, REJECT, or ACCEPT).

#3: Delete Firewall Rules

To display line number along with other information for existing rules, enter:
# iptables -L INPUT -n --line-numbers
# iptables -L OUTPUT -n --line-numbers
# iptables -L OUTPUT -n --line-numbers | less
# iptables -L OUTPUT -n --line-numbers | grep 202.54.1.1

You will get the list of IP. Look at the number on the left, then use number to delete it. For example delete line number 4, enter:
# iptables -D INPUT 4
OR find source IP 202.54.1.1 and delete from rule:
# iptables -D INPUT -s 202.54.1.1 -j DROP
Where,

  • -D : Delete one or more rules from the selected chain

#4: Insert Firewall Rules

To insert one or more rules in the selected chain as the given rule number use the following syntax. First find out line numbers, enter:
# iptables -L INPUT -n –line-numbers
Sample outputs:

Chain INPUT (policy DROP)
num  target     prot opt source               destination
1    DROP       all  --  202.54.1.1           0.0.0.0/0
2    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state NEW,ESTABLISHED 

To insert rule between 1 and 2, enter:
# iptables -I INPUT 2 -s 202.54.1.2 -j DROP
To view updated rules, enter:
# iptables -L INPUT -n --line-numbers
Sample outputs:

Chain INPUT (policy DROP)
num  target     prot opt source               destination
1    DROP       all  --  202.54.1.1           0.0.0.0/0
2    DROP       all  --  202.54.1.2           0.0.0.0/0
3    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state NEW,ESTABLISHED

#5: Save Firewall Rules

To save firewall rules under CentOS / RHEL / Fedora Linux, enter:
# service iptables save
In this example, drop an IP and save firewall rules:
# iptables -A INPUT -s 202.5.4.1 -j DROP
# service iptables save

For all other distros use the iptables-save command:
# iptables-save > /root/my.active.firewall.rules
# cat /root/my.active.firewall.rules

#6: Restore Firewall Rules

To restore firewall rules form a file called /root/my.active.firewall.rules, enter:
# iptables-restore < /root/my.active.firewall.rules
To restore firewall rules under CentOS / RHEL / Fedora Linux, enter:
# service iptables restart

#7: Set the Default Firewall Policies

To drop all traffic:
# iptables -P INPUT DROP
# iptables -P OUTPUT DROP
# iptables -P FORWARD DROP
# iptables -L -v -n
#### you will not able to connect anywhere as all traffic is dropped ###
# ping cyberciti.biz
# wget http://www.kernel.org/pub/linux/kernel/v3.0/testing/linux-3.2-rc5.tar.bz2

#7.1: Only Block Incoming Traffic

To drop all incoming / forwarded packets, but allow outgoing traffic, enter:
# iptables -P INPUT DROP
# iptables -P FORWARD DROP
# iptables -P OUTPUT ACCEPT
# iptables -A INPUT -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -L -v -n
### *** now ping and wget should work *** ###
# ping cyberciti.biz
# wget http://www.kernel.org/pub/linux/kernel/v3.0/testing/linux-3.2-rc5.tar.bz2

#8:Drop Private Network Address On Public Interface

IP spoofing is nothing but to stop the following IPv4 address ranges for private networks on your public interfaces. Packets with non-routable source addresses should be rejected using the following syntax:
# iptables -A INPUT -i eth1 -s 192.168.0.0/24 -j DROP
# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -j DROP

#8.1: IPv4 Address Ranges For Private Networks (make sure you block them on public interface)

  • 10.0.0.0/8 -j (A)
  • 172.16.0.0/12 (B)
  • 192.168.0.0/16 (C)
  • 224.0.0.0/4 (MULTICAST D)
  • 240.0.0.0/5 (E)
  • 127.0.0.0/8 (LOOPBACK)

#9: Blocking an IP Address (BLOCK IP)

To block an attackers ip address called 1.2.3.4, enter:
# iptables -A INPUT -s 1.2.3.4 -j DROP
# iptables -A INPUT -s 192.168.0.0/24 -j DROP

#10: Block Incoming Port Requests (BLOCK PORT)

To block all service requests on port 80, enter:
# iptables -A INPUT -p tcp --dport 80 -j DROP
# iptables -A INPUT -i eth1 -p tcp --dport 80 -j DROP

To block port 80 only for an ip address 1.2.3.4, enter:
# iptables -A INPUT -p tcp -s 1.2.3.4 --dport 80 -j DROP
# iptables -A INPUT -i eth1 -p tcp -s 192.168.1.0/24 --dport 80 -j DROP

#11: Block Outgoing IP Address

To block outgoing traffic to a particular host or domain such as cyberciti.biz, enter:
# host -t a cyberciti.biz
Sample outputs:

cyberciti.biz has address 75.126.153.206

Note down its ip address and type the following to block all outgoing traffic to 75.126.153.206:
# iptables -A OUTPUT -d 75.126.153.206 -j DROP
You can use a subnet as follows:
# iptables -A OUTPUT -d 192.168.1.0/24 -j DROP
# iptables -A OUTPUT -o eth1 -d 192.168.1.0/24 -j DROP

#11.1: Example – Block Facebook.com Domain

First, find out all ip address of facebook.com, enter:
# host -t a www.facebook.com
Sample outputs:

www.facebook.com has address 69.171.228.40

Find CIDR for 69.171.228.40, enter:
# whois 69.171.228.40 | grep CIDR
Sample outputs:

CIDR:           69.171.224.0/19

To prevent outgoing access to www.facebook.com, enter:
# iptables -A OUTPUT -p tcp -d 69.171.224.0/19 -j DROP
You can also use domain name, enter:
# iptables -A OUTPUT -p tcp -d www.facebook.com -j DROP
# iptables -A OUTPUT -p tcp -d facebook.com -j DROP

From the iptables man page:

… specifying any name to be resolved with a remote query such as DNS (e.g., facebook.com is a really bad idea), a network IP address (with /mask), or a plain IP address …

#12: Log and Drop Packets

Type the following to log and block IP spoofing on public interface called eth1
# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -j LOG --log-prefix "IP_SPOOF A: "
# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -j DROP

By default everything is logged to /var/log/messages file.
# tail -f /var/log/messages
# grep --color 'IP SPOOF' /var/log/messages

#13: Log and Drop Packets with Limited Number of Log Entries

The -m limit module can limit the number of log entries created per time. This is used to prevent flooding your log file. To log and drop spoofing per 5 minutes, in bursts of at most 7 entries .
# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -m limit --limit 5/m --limit-burst 7 -j LOG --log-prefix "IP_SPOOF A: "
# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -j DROP

#14: Drop or Accept Traffic From Mac Address

Use the following syntax:
# iptables -A INPUT -m mac --mac-source 00:0F:EA:91:04:08 -j DROP
## *only accept traffic for TCP port # 8080 from mac 00:0F:EA:91:04:07 * ##
# iptables -A INPUT -p tcp --destination-port 22 -m mac --mac-source 00:0F:EA:91:04:07 -j ACCEPT

#15: Block or Allow ICMP Ping Request

Type the following command to block ICMP ping requests:
# iptables -A INPUT -p icmp --icmp-type echo-request -j DROP
# iptables -A INPUT -i eth1 -p icmp --icmp-type echo-request -j DROP

Ping responses can also be limited to certain networks or hosts:
# iptables -A INPUT -s 192.168.1.0/24 -p icmp --icmp-type echo-request -j ACCEPT
The following only accepts limited type of ICMP requests:
### ** assumed that default INPUT policy set to DROP ** #############
iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT
iptables -A INPUT -p icmp --icmp-type destination-unreachable -j ACCEPT
iptables -A INPUT -p icmp --icmp-type time-exceeded -j ACCEPT
## ** all our server to respond to pings ** ##
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT

#16: Open Range of Ports

Use the following syntax to open a range of ports:
iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 7000:7010 -j ACCEPT 

#17: Open Range of IP Addresses

Use the following syntax to open a range of IP address:
## only accept connection to tcp port 80 (Apache) if ip is between 192.168.1.100 and 192.168.1.200 ##
iptables -A INPUT -p tcp --destination-port 80 -m iprange --src-range 192.168.1.100-192.168.1.200 -j ACCEPT

## nat example ##
iptables -t nat -A POSTROUTING -j SNAT --to-source 192.168.1.20-192.168.1.25

#18: Established Connections and Restaring The Firewall

When you restart the iptables service it will drop established connections as it unload modules from the system under RHEL / Fedora / CentOS Linux. Edit, /etc/sysconfig/iptables-config and set IPTABLES_MODULES_UNLOAD as follows:

IPTABLES_MODULES_UNLOAD = no

#19: Help Iptables Flooding My Server Screen

Use the crit log level to send messages to a log file instead of console:
iptables -A INPUT -s 1.2.3.4 -p tcp --destination-port 80 -j LOG --log-level crit

#20: Block or Open Common Ports

The following shows syntax for opening and closing common TCP and UDP ports:

Replace ACCEPT with DROP to block port:
## open port ssh tcp port 22 ##
iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 22 -j ACCEPT
 
## open cups (printing service) udp/tcp port 631 for LAN users ##
iptables -A INPUT -s 192.168.1.0/24 -p udp -m udp --dport 631 -j ACCEPT
iptables -A INPUT -s 192.168.1.0/24 -p tcp -m tcp --dport 631 -j ACCEPT
 
## allow time sync via NTP for lan users (open udp port 123) ##
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p udp --dport 123 -j ACCEPT
 
## open tcp port 25 (smtp) for all ##
iptables -A INPUT -m state --state NEW -p tcp --dport 25 -j ACCEPT
 
# open dns server ports for all ##
iptables -A INPUT -m state --state NEW -p udp --dport 53 -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 53 -j ACCEPT
 
## open http/https (Apache) server port to all ##
iptables -A INPUT -m state --state NEW -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 443 -j ACCEPT
 
## open tcp port 110 (pop3) for all ##
iptables -A INPUT -m state --state NEW -p tcp --dport 110 -j ACCEPT
 
## open tcp port 143 (imap) for all ##
iptables -A INPUT -m state --state NEW -p tcp --dport 143 -j ACCEPT
 
## open access to Samba file server for lan users only ##
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 137 -j ACCEPT
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 138 -j ACCEPT
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 139 -j ACCEPT
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 445 -j ACCEPT
 
## open access to proxy server for lan users only ##
iptables -A INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 3128 -j ACCEPT
 
## open access to mysql server for lan users only ##
iptables -I INPUT -p tcp --dport 3306 -j ACCEPT

#21: Restrict the Number of Parallel Connections To a Server Per Client IP

You can use connlimit module to put such restrictions. To allow 3 ssh connections per client host, enter:
# iptables -A INPUT -p tcp --syn --dport 22 -m connlimit --connlimit-above 3 -j REJECT

Set HTTP requests to 20:
# iptables -p tcp --syn --dport 80 -m connlimit --connlimit-above 20 --connlimit-mask 24 -j DROP
Where,

  1. –connlimit-above 3 : Match if the number of existing connections is above 3.
  2. –connlimit-mask 24 : Group hosts using the prefix length. For IPv4, this must be a number between (including) 0 and 32.

#22: HowTO: Use iptables Like a Pro

For more information about iptables, please see the manual page by typing man iptables from the command line:
$ man iptables
You can see the help using the following syntax too:
# iptables -h
To see help with specific commands and targets, enter:
# iptables -j DROP -h

#22.1: Testing Your Firewall

Find out if ports are open or not, enter:
# netstat -tulpn
Find out if tcp port 80 open or not, enter:
# netstat -tulpn | grep :80
If port 80 is not open, start the Apache, enter:
# service httpd start
Make sure iptables allowing access to the port 80:
# iptables -L INPUT -v -n | grep 80
Otherwise open port 80 using the iptables for all users:
# iptables -A INPUT -m state --state NEW -p tcp --dport 80 -j ACCEPT
# service iptables save

Use the telnet command to see if firewall allows to connect to port 80:
$ telnet www.cyberciti.biz 80
Sample outputs:

Trying 75.126.153.206...
Connected to www.cyberciti.biz.
Escape character is '^]'.
^]

telnet> quit
Connection closed.

You can use nmap to probe your own server using the following syntax:
$ nmap -sS -p 80 www.cyberciti.biz
Sample outputs:

Starting Nmap 5.00 ( http://nmap.org ) at 2011-12-13 13:19 IST
Interesting ports on www.cyberciti.biz (75.126.153.206):
PORT   STATE SERVICE
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 1.00 seconds

I also recommend you install and use sniffer such as tcpdupm and ngrep to test your firewall settings.

CONCLUSION:

This post only list basic rules for new Linux users. You can create and build more complex rules. This requires good understanding of TCP/IP, Linux kernel tuning via sysctl.conf, and good knowledge of your own setup. Stay tuned for next topics:

  • Stateful packet inspection.
  • Using connection tracking helpers.
  • Network address translation.
  • Layer 2 filtering.
  • Firewall testing tools.
  • Dealing with VPNs, DNS, Web, Proxy, and other protocols.
 
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How To Secure Apache with Let’s Encrypt on Ubuntu 16.04

25/03/2017 Comments off

Introduction

This tutorial will show you how to set up a TLS/SSL certificate from Let’s Encrypt on an Ubuntu 16.04 server running Apache as a web server. We will also cover how to automate the certificate renewal process using a cron job.

SSL certificates are used within web servers to encrypt the traffic between the server and client, providing extra security for users accessing your application. Let’s Encrypt provides an easy way to obtain and install trusted certificates for free. 

Prerequisites

In order to complete this guide, you will need:

  • An Ubuntu 16.04 server with a non-root sudo user, which you can set up by following our Initial Server Setup guide
  • The Apache web server installed with one or more domain names properly configured through Virtual Hosts that specify ServerName.

When you are ready to move on, log into your server using your sudo account.

 

Step 1 — Install the Let’s Encrypt Client

First, we will download the Let’s Encrypt client from the official repositories. Although the Let’s Encrypt project has renamed their client to certbot, the client included in the Ubuntu 16.04 repositories is simply called letsencrypt. This version is completely adequate for our purposes.

Update the server’s local apt package indexes and install the client by typing:

  • sudo apt-get update
  • sudo apt-get install python-letsencrypt-apache

The letsencrypt client should now be ready to use.

 

Step 2 — Set Up the SSL Certificate

Generating the SSL Certificate for Apache using the Let’s Encrypt client is quite straightforward. The client will automatically obtain and install a new SSL certificate that is valid for the domains provided as parameters.

To execute the interactive installation and obtain a certificate that covers only a single domain, run the letsencrypt command like so, where example.com is your domain:

  • sudo letsencrypt --apache -d example.com

If you want to install a single certificate that is valid for multiple domains or subdomains, you can pass them as additional parameters to the command. The first domain name in the list of parameters will be the base domain used by Let’s Encrypt to create the certificate, and for that reason we recommend that you pass the bare top-level domain name as first in the list, followed by any additional subdomains or aliases:

  • sudo letsencrypt --apache -d example.com -d www.example.com

For this example, the base domain will be example.com

After the dependencies are installed, you will be presented with a step-by-step guide to customize your certificate options. You will be asked to provide an email address for lost key recovery and notices, and you will be able to choose between enabling both http and https access or forcing all requests to redirect to https. It is usually safest to require https, unless you have a specific need for unencrypted http traffic.

When the installation is finished, you should be able to find the generated certificate files at /etc/letsencrypt/live. You can verify the status of your SSL certificate with the following link (don’t forget to replace example.com with your base domain):

https://www.ssllabs.com/ssltest/analyze.html?d=example.com&latest

You should now be able to access your website using a https prefix.

 

Step 3 — Set Up Auto Renewal

Let’s Encrypt certificates are valid for 90 days, but it’s recommended that you renew the certificates every 60 days to allow a margin of error. The Let’s Encrypt client has a renew command that automatically checks the currently installed certificates and tries to renew them if they are less than 30 days away from the expiration date.

To trigger the renewal process for all installed domains, you should run:

  • sudo letsencrypt renew

Because we recently installed the certificate, the command will only check for the expiration date and print a message informing that the certificate is not due to renewal yet. The output should look similar to this:

   Processing /etc/letsencrypt/renewal/example.com.conf

   The following certs are not due for renewal yet:
     /etc/letsencrypt/live/example.com/fullchain.pem (skipped)
     No renewals were attempted.

Notice that if you created a bundled certificate with multiple domains, only the base domain name will be shown in the output, but the renewal should be valid for all domains included in this certificate.

A practical way to ensure your certificates won’t get outdated is to create a cron job that will periodically execute the automatic renewal command for you. Since the renewal first checks for the expiration date and only executes the renewal if the certificate is less than 30 days away from expiration, it is safe to create a cron job that runs every week or even every day, for instance.

Let’s edit the crontab to create a new job that will run the renewal command every week. To edit the crontab for the root user, run:

  • sudo crontab -e

You may be prompted to select an editor:

Output
no crontab for root - using an empty one

Select an editor.  To change later, run 'select-editor'.
  1. /bin/ed
  2. /bin/nano        <---- easiest
  3. /usr/bin/vim.basic
  4. /usr/bin/vim.tiny

Choose 1-4 [2]:

Unless you’re more comfortable with ed or vim, press Enter to use nano, the default.

Include the following content at the end of the crontab, all in one line:

crontab

30 2 * * 1 /usr/bin/letsencrypt renew >> /var/log/le-renew.log

Save and exit. This will create a new cron job that will execute the letsencrypt-auto renew command every Monday at 2:30 am. The output produced by the command will be piped to a log file located at /var/log/le-renewal.log.

For more information on how to create and schedule cron jobs, you can check our How to Use Cron to Automate Tasks in a VPS guide. 

 

Conclusion

In this guide, we saw how to install a free SSL certificate from Let’s Encrypt in order to secure a website hosted with Apache. We recommend that you check the official Let’s Encrypt blog for important updates from time to time.

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Iptables Allow MYSQL server incoming request on port 3306

24/03/2017 Comments off

MySQL database is a popular for web applications and acts as the database component of the LAMP, MAMP, and WAMP platforms. Its popularity as a web application is closely tied to the popularity of PHP, which is often combined with MySQL. MySQL is open source database server and by default it listen on TCP port 3306. In this tutorial you will learn how to open TCP port # 3306 using iptables command line tool on Linux operating system.

Task: Open port 3306

In most cases following simple rule opens TCP port 3306:

iptables -A INPUT -i eth0 -p tcp -m tcp --dport 3306 -j ACCEPT

The following iptable rules allows incoming client request (open port 3306) for server IP address 202.54.1.20. Add rules to your iptables shell script:

iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 202.54.1.20 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -s 202.54.1.20 --sport 3306 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

However in real life you do not wish give access to everyone. For example in a web hosting company, you need to gives access to MySQL database server from web server only. Following example allows MySQL database server access (202.54.1.20) from Apache web server (202.54.1.50) only:

iptables -A INPUT -p tcp -s 202.54.1.50 --sport 1024:65535 -d 202.54.1.20 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -s 202.54.1.20 --sport 3306 -d 202.54.1.50 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

Please note if you follow above setup, then you need tell all your hosting customer to use 202.54.1.50 as MySQL host in PHP/Perl code. A better approach is to create following entry in /etc/hosts file or use fully qualified domain name (create dns entry) mysql.hostingservicecompany.com which points to 202.54.1.50 ip:
202.54.1.50 mysql

In shot MySQL database connection code from PHP hosted on our separate webserver would look like as follows:

// ** MySQL settings ** //
define('DB_NAME', 'YOUR-DATABASE-NAME');     // The name of the database
define('DB_USER', 'YOUR-USER-NAME');     // Your MySQL username
define('DB_PASSWORD', 'YOUR-PASSWORD''); // ...and password
define('DB_HOST', 'mysql');       // mysql i.e. 202.54.1.50
// ** rest of PHP code ** //

Lire la suite…

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Make the configuration of iptables persistent (Debian)

22/03/2017 Comments off

Objective

To make the configuration of iptables persistent on a Debian-based system

Background

The iptables and ip6tables commands can be used to instruct Linux to perform functions such as firewalling and network address translation, however the configuration that they create is non-persistent so is lost whenever the machine is rebooted. For most practical applications this is not the desired behaviour, so some means is needed to reinstate the configuration at boot time.

For security, the iptables configuration should be applied at an early stage of the bootstrap process: preferably before any network interfaces are brought up, and certainly before any network services are started or routing is enabled. If this is not done then there will be a window of vulnerability during which the machine is remotely accessible but not firewalled.

Scenario

Suppose you have a machine that you wish to protect using a firewall. You have written iptables and ip6tables rulesets, and wish to install them so that they will remain active if the machine is rebooted.

Lire la suite…

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GeoIP pour iptables

18/03/2017 Comments off

Source: how-to.ovh

Marre des pays exotiques qui essaient de s’introduire sur le serveur et pourrissent vos logs et font bosser fail2ban ?

Une solution pour bloquer les pays avec lesquels vous n’avez pas de relations. Pour Debian mais sûrement adaptable à d’autres distributions.

# Install GeoIP pour iptables

apt-get install dkms xtables-addons-dkms xtables-addons-common xtables-addons-dkms geoip-database libgeoip1 libtext-csv-xs-perl unzip

# On vérifie que c’est ok

dkms status xtables-addons

# on crée le repertoire

mkdir /usr/share/xt_geoip

# on se déplace dedans

cd /usr/share/xt_geoip/

# on télécharge le fichier

wget http://man.sethuper.com/wp-content/uploads/2013/06/geoip-dl-build.tar.gz

# on le décompresse

tar xvf geoip-dl-build.tar.gz

# on l’exécute

./xt_geoip_dl

# si cela donne un message d’erreur, on fait ceci

/usr/bin/perl -MCPAN -e'install Text::CSV_XS'

# on exécute l’autre fichier

./xt_geoip_build -D . *.csv

# on efface les fichiers inutiles

rm -rf geoip-dl-build.tar.gz

# on teste iptables en bloquant la Chine et la Russie

iptables -A INPUT -m geoip --src-cc CN,RU -j DROP

# on vérifie

iptables -L -v

# ce qui donnera cette ligne indiquant que les pays seront bloqués

DROP all -- anywhere anywhere -m geoip --source-country CN,RU

pour interdire le port 22 à ces pays

iptables -A INPUT -p tcp --dport 22 -m geoip --src-cc CN,RU -j DROP
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Block entire countries on Ubuntu server with Xtables and GeoIP

18/03/2017 Comments off

Source: jeshurun.ca

Anyone who has administered even a moderately high traffic server will have noticed that certain unwelcome traffic such as port scans and probes tend to come from IP addresses belonging to a certain group of countries. If your application or service does not cater to users in these countries, it might be a safe bet to block these countries off entirely.

This is especially true for email servers. The average email server, based on anecdotal evidence of servers for around 20 domains, rejects about 30% of incoming email every day as spam. Some servers on some days reject up to as much as 97% of incoming email as spam. Most of these originate in a certain subset of countries. That is a lot of wasted CPU cycles being expended on scanning these undesired emails for spam and viruses. Although tools such as amavisd and spamassasin do a good job of keeping the vast majority of spam out of users’ inboxes, when the rare well crafted and targeted phishing email does get through, it wrecks havoc in the enterprise.

Lire la suite…

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How to save rules of the iptables?

18/03/2017 Comments off
iptables-save

Saving iptables rules for reboot

On a server, iptables rules don’t reload automatically at reboot. You need to reload the rules using ax executable shell scripture a dedicated utility that will load them at the same time as the program itself, i.e. with the kernel.

Depending of the version of Linux you use, you can select different methods:

sudo su
iptables-save > /etc/iptables.rules

In /etc/network/if-pre-up.d/iptables, put:

#!/bin/sh
iptables-restore < /etc/iptables.rules
exit 0

After, in /etc/network/if-post-down.d/iptables, put:

#!/bin/sh
iptables-save -c > /etc/iptables.rules
if [ -f /etc/iptables.rules ];
       then iptables-restore < /etc/iptables.rules
fi
exit 0

After, give permission to the scripts:

sudo chmod +x /etc/network/if-post-down.d/iptables sudo chmod +x /etc/network/if-pre-up.d/iptables

Another scenario is to is to install iptables-persistent:

sudo apt-get install iptables-persistent

After it’s installed, you can save/reload iptables rules anytime:

    sudo /etc/init.d/iptables-persistent save 
    sudo /etc/init.d/iptables-persistent reload

Or if you use Ubuntu server 16.04, things are simpler:

The installation as described above works without a problem, but the two commands for saving and reloading above do not seem to work with a 16.04 server. The following commands work with that version:

    sudo netfilter-persistent save
    sudo netfilter-persistent reload
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Detect Webcam & Microphone Activity on Mac with Oversight

02/03/2017 Comments off

Source: osxdaily.com

Though Mac users don’t usually have to worry excessively about “camfecting” malware and spyware, some security conscious users may find it nice to know if a process or application is attempting to access their computers web camera or microphone. 

 

With the help of a free third party security utility called Oversight, you can have your Mac alert you anytime an application or process tries to activate either recording device on the computer. 

The developer of Oversight explains why a tool like Oversight could be valuable to some users:

“One of the most insidious actions of malware, is abusing the audio and video capabilities of an infected host to record an unknowing user. Macs, of course, are not immune; malware such as OSX/Eleanor, OSX/Crisis, OSX/Mokes, and others, all attempt to spy on OS X users. OverSight constantly monitors a system, alerting a user whenever the internal microphone is activated, or the built-in webcam is accessed. And yes, while the webcam’s LED will turn on whenever a session is initially started, new research has shown that malware can surreptitious piggyback into such existing sessions (FaceTime, Sykpe, Google Hangouts, etc.) and record both audio and video – without fear of detection.” 

Sound good? If so, it’s a free download that is easy to install on a Mac with either macOS or Mac OS X:

If you’re interested in this app, simply download Oversight and run the installer (it can be just as easily uninstalled later if you decide you do not need it).

Once installed, Oversight is small and lightweight running quietly in the background, and it will alert you anytime the Mac microphone or webcam FaceTime camera are attempting to be activated. You can then directly intervene and either allow the webcam or microphone access (for legitimate use), or deny it (for theoretical illegitimate use).

Oversight alerting to camera and microphone access on Mac

Keep in mind that Oversight does not differentiate between legitimate and illegitimate use of the webcam and microphone on your Mac, that is up to you. For example, you will get a notification alert that the microphone and FaceTime camera are trying to be accessed when you open an app like Skype, Photo Booth, FaceTime, or are recording a video on your Mac with the webcam, but since those applications legitimately use the computers microphone and camera they are probably nothing to be concerned about (assuming you have launched them yourself anyway). On the other hand, if out of the blue and with no provocation if you see a process has attempted to access your microphone, that could potentially be an unauthorized attempt to use the microphone and you could choose to reject it and block the device access with Oversight. Whenever possible, Oversight will attempt to notify you of the process name and PID, but sometimes you will see blank notifications of access anyway – again just think about what apps you are using and if they have any reason to use your camera or microphone, similar to how you can control this type of access in iOS for Photos, camera, and microphone

Microphone activated found by Oversight on Mac

This is a software solution which is quite a bit more fancy than the low-tech solution of putting tape on your web camera like the FBI Director does and many security professionals do. You could always use Oversight along with some tape too if you’re extra concerned about your Mac webcam or microphone access and want to be sure nothing fishy is going on from camfecting or otherwise. 

While apps like Oversight could be considered overboard and unnecessary for many Mac users, others who are privacy conscious or in fields where higher security matters may find them to be helpful. I’ve personally noticed a particular web browser will occasionally attempt to access the microphone on my Mac from time to time without an obvious reason which I find to be… curious… and Oversight notified me each time. It’s not for everyone, but if you want to be notified when something is trying to use your Mac camera or microphone, check out the app yourself. 

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How to Disable Webcam / FaceTime Camera on Mac Completely

02/03/2017 Comments off

Source: osxdaily.com

Some of the more privacy conscious Mac users out there might put tape over their webcam or use apps like Oversight to detect camera activity. While either of those approaches can be satisfactory for many users (or considered totally paranoid and overboard to others), many advanced Mac users in the security community go a step further and just outright disable their Macs front-facing web camera. This article will show you how to completely deactivate the front FaceTime camera on a Mac.

 

To be clear, this aims to completely disable the software components behind the built-in camera on Macs which prevents it from being used by any application, this webcam is sometimes called the FaceTime camera or the iSight camera, or simply the front-facing camera. All modern Macs have this camera, it is located at the top of the display and embedded into the screen bezel. By disabling the Macs camera, any application that requires it’s usage will no longer function as intended because camera access will become impossible. 

This is an advanced tutorial aimed at advanced users, it is not intended for novice or casual Mac users. This approach disables the Mac built-in camera by changing system level permissions for system level files directly relating to the camera components. If you are not comfortable modifying system files using the command line with super user privileges, do not proceed.

This tutorial applies to modern versions of MacOS including Sierra and El Capitan, you will need turn off rootless temporarily so that you can make modifications to the system folder, if you’re not sure how to do that, you can learn how to disable SIP on Mac OS here. You should aways backup a Mac before making any modifications to system software. Older versions of Mac OS X that wish to disable the iSight camera can follow these instructions instead to accomplish the same effect.

How to Disable the Web Camera on Mac

This is a string of commands that will completely disable the built-in Mac camera, meaning no applications will be able to use the front-facing camera at all. This is intended for advanced users only who thoroughly understand proper syntax and command line usage. 

  1. Back up the Mac if you have not done so already, then you will need to disable SIPfirst (and yes you should re-enable it when finished)
  2. Open the Terminal app as found in /Applications/Utilities/
  3. One by one on their own line and executed separately, issue the following five command strings into the command line and authenticate:

sudo chmod a-r /System/Library/Frameworks/CoreMediaIO.framework/Versions/A/Resources/VDC.plugin/Contents/MacOS/VDC

sudo chmod a-r /System/Library/PrivateFrameworks/CoreMediaIOServicesPrivate.framework/Versions/A/Resources/AVC.plugin/Contents/MacOS/AVC

sudo chmod a-r /System/Library/QuickTime/QuickTimeUSBVDCDigitizer.component/Contents/MacOS/QuickTimeUSBVDCDigitizer

sudo chmod a-r /Library/CoreMediaIO/Plug-Ins/DAL/AppleCamera.plugin/Contents/MacOS/AppleCamera

sudo chmod a-r /Library/CoreMediaIO/Plug-Ins/FCP-DAL/AppleCamera.plugin/Contents/MacOS/AppleCamera

  1. Exit Terminal when complete, don’t forget to re-enable SIP on the Mac as well

(Note you can also use chmod 200 instead of a-r if you prefer using numbers, the effect will be the same and permissions will be –w——-)

After the Mac camera has been disabled this way, if you attempt to open FaceTime, Skype, Photo Booth, QuickTime, iMovie, or any other app which uses the built-in camera, you will get a message stating “there is no connected camera” on the Mac – which is exactly what you would want to see if you disabled the camera intentionally.

Mac camera disabled as shown by no camera connected error message

You should not need to reboot for the changes to take effect, though you may need to relaunch some active applications with camera access.

How to Re-Enable the Camera on Mac

Just as before when disabling the camera, to re-enable the Mac camera this way you will likely need to temporarily disable SIP in Mac OS before beginning. Then the commands to issue one by one are as follows:

sudo chmod a+r /System/Library/Frameworks/CoreMediaIO.framework/Versions/A/Resources/VDC.plugin/Contents/MacOS/VDC

sudo chmod a+r /System/Library/PrivateFrameworks/CoreMediaIOServicesPrivate.framework/Versions/A/Resources/AVC.plugin/Contents/MacOS/AVC

sudo chmod a+r /System/Library/QuickTime/QuickTimeUSBVDCDigitizer.component/Contents/MacOS/QuickTimeUSBVDCDigitizer

sudo chmod a+r /Library/CoreMediaIO/Plug-Ins/DAL/AppleCamera.plugin/Contents/MacOS/AppleCamera

sudo chmod a+r /Library/CoreMediaIO/Plug-Ins/FCP-DAL/AppleCamera.plugin/Contents/MacOS/AppleCamera

(Note you can also use chmod 755 instead of a+r if you prefer using numbers to return to -rwxr-xr-x, the effect will be the same)

You’ll notice the difference between the enabling and disabling commands are simply the permissions change chmod command flag – has turned into a +, indicating the file(s) have read access now whereas before they did not, which is what prevented the camera from working. 

If this approach is insufficient for your privacy or security needs for whatever reason, you’d likely need to go a step further and actually disassemble your Mac hardware to physically disconnect any camera cables, a task which is quite advanced but undeniably the most effective approach if you want to completely disable the Mac camera and don’t ever want the Macs camera to be used.

Why would I want to disable the Mac camera?

Most Mac users would not want to disable their FaceTime / iSight camera. Typically only very advanced Mac users who have a specific reason to completely disable the built-in camera on their Mac would want to do this, whether they are systems administrators, security professionals, for privacy reasons, or otherwise. This is not intended for the average Mac user. If you’re an average, casual, or novice Mac user who is concerned about privacy and any possible camera shenanigans, try putting tape on your web cam, like the FBI director does, which is much lower tech and less involved, easy to reverse, and quite effective since obviously if something is obstructing the camera lens than it is not usable.

 

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Categories: Sécurité, Système, Tutoriel Tags: ,