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65 lines
2.7 KiB
Markdown
65 lines
2.7 KiB
Markdown
# Fail2Ban
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**Fail2Ban** is an intrusion prevention software that protects computer servers against brute-force attacks. It monitors certain logs and will ban IP addresses that show brute-force-like behavior.
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In particular, **Fail2Ban** monitors `SSH` connection attempts. After 5 failed SSH connection attempts, Fail2Ban will ban the IP address from connecting via SSH for 10 minutes. If this address fails several times, it might get banned for a week.
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## Unban an IP address
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To unblock an IP address, you must first access your server by some means (for example from another IP address or from another internet connection than the banned one).
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Then, look at the **Fail2Ban’s log** to identify in which `jail` the IP address has been banned:
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```bash
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sudo tail /var/log/fail2ban.log
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2019-01-07 16:24:47 fail2ban.filter [1837]: INFO [sshd] Found 11.22.33.44
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2019-01-07 16:24:49 fail2ban.filter [1837]: INFO [sshd] Found 11.22.33.44
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2019-01-07 16:24:51 fail2ban.filter [1837]: INFO [sshd] Found 11.22.33.44
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2019-01-07 16:24:54 fail2ban.filter [1837]: INFO [sshd] Found 11.22.33.44
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2019-01-07 16:24:57 fail2ban.filter [1837]: INFO [sshd] Found 11.22.33.44
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2019-01-07 16:24:57 fail2ban.actions [1837]: NOTICE [sshd] Ban 11.22.33.44
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2019-01-07 16:24:57 fail2ban.filter [1837]: NOTICE [recidive] Ban 11.22.33.44
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```
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Here, the `11.22.33.44` IP address has been banned in the `sshd` and `recidive` jails.
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Then deban the IP address with the following commands:
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```bash
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sudo fail2ban-client set sshd unbanip 11.22.33.44
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sudo fail2ban-client set recidive unbanip 11.22.33.44
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```
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## Whitelist an IP address
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If you don’t want a "legitimate" IP address to be blocked by **YunoHost** anymore, then you have to fill it in the whitelist of the `jail` configuration file.
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When updating the **Fail2ban** software, the original `/etc/fail2ban/jail.conf` file is overwritten. So it is on a new dedicated file that we will store the changes. They will thus be preserved over time.
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1. Start by creating the new jail configuration file which will be called `yunohost-whitelist.conf`:
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```bash
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sudo touch /etc/fail2ban/jail.d/yunohost-whitelist.conf
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```
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2. Edit this new file with your favorite editor:
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```bash
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sudo nano /etc/fail2ban/jail.d/yunohost-whitelist.conf
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```
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3. Paste the following content into the file and adapt the IP address `XXX.XXX.XXX.XXX` :
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```bash
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[DEFAULT]
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ignoreip = 127.0.0.1/8 XXX.XXX.XXX.XXX #<= the IP address (you can put more than one, separated by a space) that you want to whitelist
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```
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4. Save the file and reload the Fail2Ban configuration:
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```bash
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sudo fail2ban-client reload
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```
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Congratulations, no more risks of banning yourself from your own YunoHost server!
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