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diff --git a/blog/server-hardening/index.org b/blog/server-hardening/index.org new file mode 100644 index 0000000..ba8a994 --- /dev/null +++ b/blog/server-hardening/index.org @@ -0,0 +1,334 @@ +#+title: Hardening a Public-Facing Home Server +#+date: 2022-03-24 +#+description: Learn some basic techniques to harden a home server and network. +#+filetags: :security: + +* Post Updates + +#+begin_quote +After reviewing this post today (2022-10-04), I noticed quite a few gaps +in my write-up and wanted to add a few things, even though this blog is +really just a retrospective and knowledge dump for myself. I left things +intact and simply crossed them out (+like this+) for posterity. +#+end_quote + +* Planning Data Flows & Security +** My Personal Data Flow +#+begin_src txt + ┌───────┐ ┌─────────────────┐ + ┌──► VLAN1 ├───► Private Devices │ + │ └───────┘ └─────────────────┘ +┌──────────┐ ┌────────┐ ┌──────────┐ ┌────────┐ │ +│ Internet ├───► Router ├───► Firewall ├───► Switch ├──┤ +└──────────┘ └────────┘ └──────────┘ └────────┘ │ + │ ┌───────┐ ┌───────────────┐ + └──► VLAN2 ├───► Public Server │ + └───────┘ └───────────────┘ +#+end_src + +** Thought Process +To serve content from your home server and harden your security posture, +you have to think about the transport of data from =server= to =client=. + +Let's start with the actual server itself. Think about the following: + +- Do I have a firewall enabled? Do I need to update this to allow new + ports or IPs? +- Do I have an IPS/IDS that may prevent outside traffic? +- Do I have any other security software installed? +- Are the services hosted inside Docker containers, behind a reverse + proxy, or virtualized? If so, are they configured to allow outside + traffic? + +Once the data leaves the server, where does it go? In my case, it goes +to a managed switch. In this case, I asked the following: + +- What configurations is the switch using? +- Am I using VLANs? + - Yes, I am using 802.1Q VLANs. +- Are the VLANs configured properly? + - Yes, as shown in the Switch section below, I have a + separate VLAN to allow outside traffic to and from the server alone. + No other devices, except for a service port, and in that VLAN. + +At this point, the data has been processed through the switch. Where +does it go next? In my case, it's pretty simple: it goes to the +router/modem device. + +- Does my ISP block any ports that I need? + - This is an important step that a lot of people run into when + self-hosting at home. Use an online port-checker tool for your IP or + call your ISP if you think ports are blocked. +- Is there a router firewall? + - Yes, I checked that it's configured to allow the ports I need to run + my services publicly. Common web servers and reverse proxies require + ports 80 and 443, but other services like media servers or games can + require unique ports, so be sure to check the documentation for your + service(s). +- Are there any other settings affecting inbound/outbound traffic? + - Schedules or access blocks + - Static Routing + - QoS + - Port Forwarding + - DMZ Hosting + - Remote Management (this can sometimes mess with services that also + require the use of ports 80 and 443) + +Once the data leaves my router, it goes to the upstream ISP and can be +accessed publicly. + +*** Server ++The services I run on my server are installed straight into the OS, +without any use of Docker or VMs, so I don't need any extra application +configuration to make them accessible to the outside world.+ + +As of 2022-10-04, the paragraph above is no longer true as I now run a +reverse proxy with Nginx and host many services inside Docker. However, +it doesn't change anything regarding this post as I still just need to +open ports 80 & 443 and create the necessary website configuration +files. + +When creating new services - either installed directly on bare metal or +within something like Docker - I ensure that I read through the +documentation thoroughly to understand a few key things: - What network +activities should this app perform (if any)? Using which ports and +protocols? - Does this app require any commands/services to be run as +=root=? - Does this app log errors, authentication failures/successes, +or anything else that would be useful for an investigation? + +For extra security, I use limit all incoming connections to SSH +connections through my server firewall (=ufw=) and disable common SSH +settings. After all of that, I use =fail2ban= as a preventative measure +against brute-force login attempts. + +As another piece of security, you can randomize your SSH port to ensure +that random scanners or attackers can't easily try to force their way +into your network. For example, you can edit the port rules in your +server to block all connection requests to port =22= but forward all +remote connections from port =12345= to your server's port =22=. Then +you just need to SSH to your network via your randomized port. + +** =ufw= +To see how to configure =ufw=, see my other post: +[[../secure-your-network-with-the-uncomplicated-firewall/][Secure +Your Network with the Uncomplicated Firewall]]. + +The general notion with an on-device firewall is that you want to deny +all incoming connections by default and then selectively open certain +ports for services or users that you know need access. + +If you know that you will only be logging into this server from a +certain set or list of IPs, you can always set the firewall to only +allow connections to port 22 from those IPs. + +For a quick start to only allow SSH connections to the server, use this: + +#+begin_src sh +sudo ufw default deny incoming +sudo ufw default allow outgoing +sudo ufw allow 22 +sudo ufw enable +#+end_src + +#+caption: ufw +[[https://img.cleberg.net/blog/20220324-hardening-a-public-facing-home-server/ufw.png]] + +** =ssh= +1. Using SSH Keys + + First, make sure you have an SSH keypair generated on the device(s) + that you'll be using to log in to the server. If you don't have an + SSH key, run this command: + + #+begin_src sh + ssh-keygen + #+end_src + + Now that we have an SSH key, copy it to the server with the following + command, which will ask for the user's password before accepting the + key: + + #+begin_src sh + ssh-copy-id my_user@my_server + #+end_src + + If you have multiple keys, you'll need to specify which to use. After + it's complete, =ssh= back into the server as that user and make sure + it doesn't ask for a password. + +2. Disable Password & Root Authentication + + Now that we can access the server without a password, we will disable + password authentication and disable anyone from using =ssh= to login + as =root=. + + To do this, open the =sshd_config= file: + + #+begin_src sh + sudo nano /etc/ssh/sshd_config + #+end_src + + You'll need to update the parameters to the values below. If one of + these rules is commented-out or doesn't exist, create the rule at the + bottom of the file. + + #+begin_src config + PermitRootLogin no + PasswordAuthentication no + PubkeyAuthentication yes + #+end_src + + Finally, restart the =ssh= service: + + #+begin_src sh + sudo systemctl restart sshd.service + #+end_src + + To test that everything's working so far, open ANOTHER terminal and + try logging in as =root= over SSH. It is very important that you keep + your current SSH session open and test with an additional session, or + you will lock yourself out at some point and will need to use a + recovery method (e.g., hooking monitor up to home server) to get + yourself back in. + +3. Enable MFA for =ssh= + + This part is optional, but I highly recommend it. So far, we've + ensured that no one can log into our user on the server without using + our secret key, and we've ensured that no one can log in remotely as + =root=. Next, you can enable MFA authentication for =ssh= + connections. + + This process involves editing a couple files and installing an MFA + package, so I will not include all the details in this post. To see + how to configure MFA for =ssh=, see my other post: + [[../enable-totp-mfa-for-ssh/][Enabling MFA for SSH]]. + + #+caption: SSH MFA + [[https://img.cleberg.net/blog/20220324-hardening-a-public-facing-home-server/ssh_mfa.png]] + +** =fail2ban= +I haven't written a post on how I use =fail2ban=, but it's quite simple. +I use the default =sshd= jail, but you can always create new jails for +respective applications or ports. For example, if you use Nginx as your +web server, you can use the =nginx-http-auth= jail. + +In order to get it up and running, use the following commands: + +#+begin_src sh +sudo apt install fail2ban +sudo fail2ban-client start sshd +sudo fail2ban-client status sshd +#+end_src + +This should be used as a last-resort defense and shouldn't be a +replacement for the security measures mentioned above. + +#+caption: fail2ban +[[https://img.cleberg.net/blog/20220324-hardening-a-public-facing-home-server/fail2ban.png]] + +* Switch +Between the router and any local devices is my managed switch, which is +used to create VLANs. The example below shows how I would isolate the +VLANs if I were starting to host a single service at home. + +** 802.1Q VLAN Configuration +In this configuration, port 8 is the public server that needs to be +accessed from the outside. Port 23 is my 'dedicated service port' for +this server. In order to SSH to this server, I need to plug my laptop +into port 23 or else I cannot SSH. Otherwise, I'd need to hook up a +monitor and keyboard directly to the server to manage it. + +| VLAN ID | VLAN Name | Member Ports | Tagged Ports | Untagged Ports | +|---------+-----------+--------------+--------------+----------------| +| 1 | Default | 1-24 | | 1-24 | +| 2 | Server | 1,8,23 | | 1,8,23 | + +** 802.1Q VLAN PVID Setting +Once the VLAN is created, I simply add the =VLAN ID= of =2= as the +=PVID= for any related ports (in this case, see that ports =8= and =23= +have a PVID of =2=). + +| Port | PVID | +|------+------| +| 1 | 1 | +| 2 | 1 | +| 3 | 1 | +| 4 | 1 | +| 5 | 1 | +| 6 | 1 | +| 7 | 1 | +| 8 | 2 | +| 9 | 1 | +| 10 | 1 | +| 11 | 1 | +| 12 | 1 | +| 13 | 1 | +| 14 | 1 | +| 15 | 1 | +| 16 | 1 | +| 17 | 1 | +| 18 | 1 | +| 19 | 1 | +| 20 | 1 | +| 21 | 1 | +| 22 | 1 | +| 23 | 2 | +| 24 | 1 | + +* Router +On my router, the configuration was as easy as opening the firewall +settings and unblocking the ports I needed for my services (e.g., +HTTP/S, Plex, SSH, MySQL, etc.). + ++Since I'm relying on an ISP-provided modem/router combo for now (not by +choice), I do not use any other advanced settings on my router that +would inhibit any valid traffic to these services.+ + +The paragraph above regarding the ISP-owned router is no longer accurate +as I now use the Ubiquiti Unifi Dream Machine Pro as my router. Within +this router, I enabled port forwarding/firewall rules, segregate the +network based on the device, and enable traffic restrictions (e.g., +silently drop traffic from certain countries and threat categories). + +If you have the option with your ISP, I recommend using a personal +router with software that you are familiar with so that you can explore +all the options available to you. + +* Physical Security +One large piece of self-hosting that people generally don't discuss +online is physical security. However, physical security is very +important for everyone who hosts a server like this. Exactly /how/ +important it is depends on the server use/purpose. + +If you self-host customer applications that hold protected data (HIPAA, +GDPR, COPPA, etc.), then physical security is extremely important and +cannot be ignored. If you simply host a blog and some hobby sites, then +it's a relatively minor consideration, but one you still need to think +about. + +** Location +The first consideration is quite simple: location. - Is the server +within a property you own or housed on someone else's property? - Is it +nearby (in your house, in your work office, in your neighbor's garage, +in a storage unit, etc.)? - Do you have 24/7 access to the server? - Are +there climate considerations, such as humidity, fires, tornadoes, +monsoons? - Do you have emergency equipment nearby in case of emergency? + +** Hardware Ownership +Secondly, consider the hardware itself: - Do you own the server in its +entirety? - Are any other users able to access the server, even if your +data/space is segregated? - If you're utilizing a third party, do they +have any documentation to show responsibility? This could be a SOC 1/2/3 +report, ISO compliance report, internal security/safety documentation. + +** Physical Controls +Regardless of who owns the hardware, ensure that there are adequate +safeguards in place, if necessary. These usually don't apply to small +home servers and are usually covered already if you're utilizing a third +party. + +These can include: - Server bezel locks - Server room locks - physical, +digital, or biometric authentication - Security cameras - Raised +floors/lowered ceilings with proper guards/gates in-place within the +floors or ceilings - Security personnel - Log sheets and/or guest badges |