Dev and Maintainer of Lemmy Userdata Migration

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  • 12 Comments
Joined 3 months ago
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Cake day: April 20th, 2024

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  • I’ve been tempted by Tailscale a few times before, but I don’t want to depend on their proprietary clients and control server. The latter could be solved by selfhosting Headscale, but at this point I figure that going for a basic Wireguard setup is probably easier to maintain.

    I’d like to have a look at your rules setup, I’m especially curious if/how you approached the event of the commercial VPN Wireguard tunnel(s) on your exit node(s) going down, which depending on the setup may send requests meant to go through the commercial VPN through your VPS exit node.

    Personally, I ended up with two Wireguard containers in the target LAN, a wireguard-server and a **wireguard-client **container.

    They both share a docker network with a specific subnet {DOCKER_SUBNET} and wireguard-client has a static IP {WG_CLIENT_IP} in that subnet.


    The wireguard-client has a slightly altered standard config to establish a tunnel to an external endpoint, a commercial VPN in this case:

    [Interface]
    PrivateKey = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    Address = XXXXXXXXXXXXXXXXXXX
    
    PostUp = iptables -t nat -A POSTROUTING -o wg+ -j MASQUERADE
    PreDown = iptables -t nat -D POSTROUTING -o wg+ -j MASQUERADE
    
    PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT && ip6tables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
    
    PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT && ip6tables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
    
    [Peer]
    PublicKey = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    AllowedIPs = 0.0.0.0/0,::0/0
    Endpoint = XXXXXXXXXXXXXXXXXXXX
    

    where

    PostUp = iptables -t nat -A POSTROUTING -o wg+ -j MASQUERADE
    PreDown = iptables -t nat -D POSTROUTING -o wg+ -j MASQUERADE
    

    are responsible for properly routing traffic coming in from outside the container and

    PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT && ip6tables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
    
    PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT && ip6tables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
    

    is your standard kill-switch meant to block traffic going out of any network interface except the tunnel interface in the event of the tunnel going down.


    The wireguard-server container has these PostUPs and -Downs:

    PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -A FORWARD -o %i -j ACCEPT; iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

    default rules that come with the template and allow for routing packets through the server tunnel

    PostUp = wg set wg0 fwmark 51820

    the traffic out of the tunnel interface get marked

    PostUp = ip -4 route add 0.0.0.0/0 via {WG_CLIENT_IP} table 51820

    add a rule to routing table 51820 for routing all packets through the wireguard-client container

    PostUp = ip -4 rule add not fwmark 51820 table 51820

    packets not marked should use routing table 51820

    PostUp = ip -4 rule add table main suppress_prefixlength 0

    respect manual rules added to main routing table

    PostUp = ip route add {LAN_SUBNET} via {DOCKER_SUBNET_GATEWAY_IP} dev eth0

    route packages with a destination in {LAN_SUBNET} to the actual {LAN_SUBNET} of the host

    PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -D FORWARD -o %i -j ACCEPT; iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE; ip route del {LAN_SUBNET} via {DOCKER_SUBNET_GATEWAY_IP} dev eth0

    delete those rules after the tunnel goes down

    PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark 0xca6c -m addrtype ! --dst-type LOCAL -j REJECT && ip6tables -I OUTPUT ! -o %i -m mark ! --mark 0xca6c -m addrtype ! --dst-type LOCAL -j REJECT
    PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark 0xca6c -m addrtype ! --dst-type LOCAL -j REJECT && ip6tables -D OUTPUT ! -o %i -m mark ! --mark 0xca6c -m addrtype ! --dst-type LOCAL -j REJECT
    

    Basically the same kill-switch as in wireguard-client, but with the mark manually substituted since the command it relied on didn’t work in my server container for some reason and AFAIK the mark actually doesn’t change.


    Now do I actually need the kill-switch in wireguard-server? Is the kill-switch in wireguard-client sufficient? I’m not even sure anymore.



  • Oh, neat! Never noticed that option in the Wireguard app before. That’s very helpful already. Regarding your opnsense setup:

    I’ve dabbled in some (simple) routing before, but I’m far from anything one could call competent in that regard and even if I’d read up properly before writing my own routes/rules, I’d probably still wouldn’t trust that I hadn’t forgotten something to e.g. prevent IP/DNS leaks.

    I’m mainly relying on a Docker and was hoping for pointers on how to configure a Wireguard host container to route only internet traffic through another Wireguard Client container.

    I found this example, which is pretty close to my ideal setup. I’ll read up on that.




  • We have to vote for the people who will admit to that and get rid of them. The U.S. is going to have to choose between a leader who tries to install good people to run the government and one who intends to install people bent on dismantling the government and giving loyalty to the leader alone.

    I largely share your thoughts. I honestly expected Biden to at least be prepared enough to counter the usual Trump tactics of making things up and using strong words to impress his base while deflecting blame or critical questions.

    Instead, we got Trump basically having free rein to appear strong with simple (and wrong) answers to complex questions, twisting the truth to support his positions and straight up lying and deflecting when finally confronted with something.

    I’m not a big fan of Biden, but IMO he’s the obvious, rational choice out of two candidates way past their prime - if you’re into rationality over the antics of a con artist.

    But this isn’t a fair fight, and Biden isn’t the showman Trump managed to be today. Biden was barely audible and mostly on the defensive while appearing weak, Trump was the opposite of that. I can’t imagine any Trump voter switching teams after the debate, but I can image more than a few more emotionally motivated democrats second guessing their choice.


  • Sure, the code is completely client-side, simply clone it. If you’re running into CORS problems due to the file:// scheme Origin of opening a local file, simply host it as a local temporary server with something like python -m http.server .

    This is due to the two ways most instances validate Cross-Origin requests:


    • Sending Access-Control-Allow-Origin: * (allow all hosts)
    • Dynamically putting your Origin into the Origin header of the response to your requests by the backend

    file:// URLs will result in a null or file:// Origin which can’t be authorized via the second option, therefore the need to sometimes host the application via (local) webserver.


  • The whole point of this being a web app is to make it as easy as possible for the user to download/modify/transfer their user data. LASIM is a traditional app the user has to download and install, similar to a script this web app was developed to replace due to being too difficult to use for some users.

    The import functionality targeted by this API is additive and my app features a built-in editor to add, modify or remove information as the user sees fit. To achieve your stated goal, you’d have to remove anything except the blocked_users entries before importing, which my app supports, I added a wiki entry explaining the workflow in more Detail.

    I may add options to modify the exported data in some ways via a simple checkbox in the future, but I wouldn’t count on it. I’m always open for pull requests!



  • The export/import functionality is, yes. This implementation uses the same API endpoints, but the main reason for this existing:

    An instance I was on slowly died, starting with the frontend (default web UI). At least at the time, no client implemented the export/import functionality, so I wrote a simple script in Bash to download the user data, if the backend still works. Running a script can still be a challenge to some users, so I wrote a web application with the same functionality. It’s a bit redundant if we’re talking about regularly working instances, but can be of use if the frontend isn’t available for some reason.





  • The problem isn’t necessarily “stuff not sent over vpn isn’t encrypted”. Everyone uses TLS.

    Never said it was. It’s a noteworthy detail, since some (rare) HTTP unencrypted traffic as well as LAN traffic in general is a bit more concerning than your standard SSL traffic contentwise, apart from the IP.

    For this to be practical you first need a botnet of compromised home routers

    This is more of a Café/Hotel Wi-Fi thing IMO. While it may take some kind of effort to get control over some shitty IoT device in your typical home environment, pretty much every script kiddie can at least force spoof the DHCP server in an open network.


  • Interesting read.

    So, in short:

    • The attacker needs to have access to your LAN and become the DHCP server, e.g. by a starvation attack or timing attacks
    • The attacked host system needs to support DHCP option 121 (atm basically every OS except Android)
    • by abusing DHCP option 121, the attacker can push routes to the attacked host system that supersede other rules in most network stacks by having a more specific prefix, e.g. a 192.168.1.1/32 will supersede 0.0.0.0/0
    • The attacker can now force the attacked host system to route the traffic intended for a VPN virtual network interface (to be encrypted and forwarded to the VPN server) to the (physical) interface used for DHCP
    • This leads to traffic intended to be sent over the VPN to not get encrypted and being sent outside the tunnel.
    • This attack can be used before or after a VPN connection is established
    • Since the VPN tunnel is still established, any implemented kill switch doesn’t get triggered

    DHCP option 121 is still used for a reason, especially in business networks. At least on Linux, using network namespaces will fix this. Firewall mitigations can also work, but create other (very theoretical) attack surfaces.