From 797a1404213173791a5f4126a77ad383ceb00064 Mon Sep 17 00:00:00 2001 From: Christian Cleberg Date: Mon, 4 Mar 2024 22:34:28 -0600 Subject: initial migration to test org-mode --- content/blog/2022-03-24-server-hardening.md | 353 ---------------------------- 1 file changed, 353 deletions(-) delete mode 100644 content/blog/2022-03-24-server-hardening.md (limited to 'content/blog/2022-03-24-server-hardening.md') diff --git a/content/blog/2022-03-24-server-hardening.md b/content/blog/2022-03-24-server-hardening.md deleted file mode 100644 index 90cb433..0000000 --- a/content/blog/2022-03-24-server-hardening.md +++ /dev/null @@ -1,353 +0,0 @@ -+++ -date = 2022-03-24 -title = "Hardening a Public-Facing Home Server" -description = "Learn some basic techniques to harden a home server and network." -+++ - -## Post Updates - -> 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. - -## Planning Data Flows & Security - -### My Personal Data Flow - -```txt - ┌───────┐ ┌─────────────────┐ - ┌──► VLAN1 ├───► Private Devices │ - │ └───────┘ └─────────────────┘ -┌──────────┐ ┌────────┐ ┌──────────┐ ┌────────┐ │ -│ Internet ├───► Router ├───► Firewall ├───► Switch ├──┤ -└──────────┘ └────────┘ └──────────┘ └────────┘ │ - │ ┌───────┐ ┌───────────────┐ - └──► VLAN2 ├───► Public Server │ - └───────┘ └───────────────┘ -``` - -### 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](#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](/blog/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: - -```sh -sudo ufw default deny incoming -sudo ufw default allow outgoing -sudo ufw allow 22 -sudo ufw enable -``` - -![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: - - ```sh - ssh-keygen - ``` - - 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: - - ```sh - ssh-copy-id my_user@my_server - ``` - - 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: - - ```sh - sudo nano /etc/ssh/sshd_config - ``` - - 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. - - ```config - PermitRootLogin no - PasswordAuthentication no - PubkeyAuthentication yes - ``` - - Finally, restart the `ssh` service: - - ```sh - sudo systemctl restart sshd.service - ``` - - 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: - [Enabling MFA for SSH](/blog/enable-totp-mfa-for-ssh/). - - ![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: - -```sh -sudo apt install fail2ban -sudo fail2ban-client start sshd -sudo fail2ban-client status sshd -``` - -This should be used as a last-resort defense and shouldn't be a -replacement for the security measures mentioned above. - -![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 -- cgit v1.2.3-70-g09d2