[tptacek]

I understand the impulse, but I think it misconstrues the "red tape" this method avoids. It's sidestepping a quirky OS limitation, which dates back to an era of "privileged ports" and multi-user machines. It's not really sidestepping any sort of modern policy boundary. For instance: you could do the exact same thing with WebSockets (and people do).

[taeric]

I was thinking websockets; though, I thought those largely hit the same criticisms? That is, tons of things moved to them specifically to avoid any firewall rules about what they were allowed to send over a network.

I'll fully grant that that seems to be the norm for everything browser related. Policies got difficult to install new software, just point your browser to this url and call it a day.

[mindcrime]

I was thinking websockets; though, I thought those largely hit the same criticisms? That is, tons of things moved to them specifically to avoid any firewall rules about what they were allowed to send over a network.

Arguably, this basic phenomenon has been going on for 20+ years. A lot of people by 2005-2007 or so had come to belive (and probably correctly) that a lot of the impetus for adopting SOAP based web-services over the preceding few years was simply because everything ran over ports 80 and 443 which were already open in the firewall. So deploying a remote service this way was more tractable than submitting a request to allow access to yet another port in firewall, and deal with the inevitable bureaucratic nightmare of getting that approved.

[Xelynega]

You can also sidestep that "quirky OS limitation" by just setting the first unprivileged port to 0(ip_unprivileged_port_start), no need for an new stack.

https://www.kernel.org/doc/Documentation/networking/ip-sysct...

[tptacek]

You can do that. Random programs cannot. Our CLI, which also does user-mode WireGuard and TCP/IP, doesn't even want to run under sudo. You're seeing the point, now: you want to build interesting network features that work the same way everywhere without demanding that your users be system administrators. Hence: user-mode TCP/IP.

[Xelynega]

I'm still not seeing the point sadly.

If you're running on a system you don't administrate that has ports under 1024 set as privileged, there's no way(with or without your cli) to have a userspace program receive TCP or UDP packets coming into the kernel from external devices for these ports(unless I'm completely mistaken).

What can you accomplish with "user-mode TCP/IP" that you can't from userspace with system calls?

[tptacek]

You are completely mistaken. You can do literally anything you want with TCP/IP provided you can talk UDP on any port, by running a user-mode TCP/IP stack over WireGuard on that port.

[Xelynega]

I don't think you understand, and based on your reply it doesn't sound like I'm mistaken.

With this CLI I am able to listen for external packets to port 80 from userspace without any elevated permissions and intercept traffic that's going to an application that's bound to that port on the OS?

Edit: I think I understand what you're trying to do, but if I do then traffic is going from the kernel UDP stack to the userland TCP stack, back to the UDP kernel stack. Not sure how that avoids sending the packet to the kernel. If it's to get around the port restrictions, why can you not just use unprivileged ports?

[tptacek]

I'm not sure I can make this any simpler for you or easier to get your head around. If it helps: the idea here is giving an invocation of your program its own IP address. It can then do whatever it likes with TCP/IP for that address; its own routing, arbitrary protocols, whatever. The Go standard library makes it extremely easy to integrate. To the OS, it's all just ordinary socket code.

[nonameiguess]

When they're talking about classified defense networks, the actual restrictions they mean is least privilege and separation of duties. Devs are not admins. They don't get root privilege on their machines. They can't create virtual network interfaces and they also can't change kernel settings. But if you put a full TCP/IP stack in userspace, well, they can run that and do whatever they want with it.

To answer the upstream question about why arbitary outbound connections are allowed, they're not. This is connecting to a cloud development environment, and I would have to assume this service can be self-hosted, because on a classified network, the "cloud" isn't the cloud as Hacker News readers know it. Amazon et all run private data centers on US military installations that only the military and the IC can access and they're airgapped from the Internet. If you're on a workstation that can access this environment, that's all it can access. The only place you can exfiltrate data to is other military-controlled servers.

[Xelynega]

If you're talking about developer machines, isn't the best(and easiest) solution to just run a VM that you administer so you can create virtual networks?

If you're talking about production machines, a userspace application wouldn't be able to sniff privileged ports without elevated permissions, so I fail to see how this application would let you get around that limitation.

[tptacek]

No, because VMs are expensive and require some base level of system administration to operate, booting them usually requires privilege, and if the only problem you're trying to solve is reliably running (e.g.) Postgres and Redis protocol between your CLI and a server somewhere, it's extreme overkill.

[Xelynega]

VMs are free and can be run by any semi-competent developer wanting to host a test server on their development machine.

Postgres and Redis can use non-privileged ports, so I don't understand why this would matter.

[tptacek]

"Just use a VM" instead of running a Unix command that drives a UDP socket is... a take.

[anyfoo]

Getting that change onto the system sounds like "at best a big delay and at worst a nonstarter".