New Bitcoin DDoS Technique

https://github.com/bitcoin/bitcoin/issues/26585

by pbear2k21 • 4 years ago

49 32 4 years ago

github.com

xcombelle• 4 years ago

it is slowloris [1] isn't it ?

[1] https://en.wikipedia.org/wiki/Slowloris_(computer_security)

pstrateman3• 4 years ago

He's just DDoSing himself.

Unless there's been a significant regression these issues were fixed after I found the slowloris type attacks to be an issue in 2012.

Edit: Maybe he's attacking his own RPC port, which again doesn't matter since it's not open to the internet.

pbear2k2111• 4 years ago

yes - testing his own node. that is how pen testing blockchain nodes works. from there you can make projections of scaled attacks.

it's not an rpc port - and the computer in the screen shot using telnet is an external machine that isn't participating in the attack.

pstrateman3• 4 years ago

Nah all that's happening is he's using connection slots.

The attacking node will have a very low score and get disconnected when other legitimate connections are made.

durpkingOP• 4 years ago

Prove it. Setup a node and test this method on it. Otherwise this comment should be redacted.

yonixw• 4 years ago

I guess the punchline here is that there are no rate limits/cool downs per IP? But surely a hardened Linux VM will have those...

pbear2k2111• 4 years ago

it is

nibbleshifter• 4 years ago

Sending lots of junk connections to a service will degrade performance.

News at eleven.

pbear2k2111• 4 years ago

bitcoind not having ip associated throttling edit: BUILT IN* is questionable. this attack shouldn't work on out-of-the-box installs of bitcoin. as i mentioned earlier - there is no rationale behind a single machine making 1k handshake requests per second.

BenoitP2• 4 years ago

    sudo iptables --append INPUT --source 123.123.123.123 --jump DROP

8organicbits• 4 years ago

Slightly more details here:

https://g.livejournal.com/14363.html

nullc5• 4 years ago

Having not followed the projects' security process, presumably this is something the author didn't think was a serious issue themselves.

This doesn't appear to be new or interesting: If you exhaust a hosts incoming sockets it temporarily can't accept new connections.

Bitcoin itself already prioritizes existing and "good" connections to a substantial extent. Networks and IPs with multiple existing connections are prioritized for disconnection to handle new connections[1]. The result is that most existing connections are undisturbed, which makes it fairly ineffectual as an attack-- unless someone has broken something in the last couple years since I worked on it. A few years ago there were some periodic waves of people attempting attacks like this that went completely unnoticed in public due to their lack of meaningful effect.

It's annoying that new connections can be frustrated while an attack is ongoing, but since bitcoin connections are extremely long lived it doesn't have much of an impact, which is the security property the software is intended to uphold. The comment about 'finalization' suggests the author of the post isn't particularly familiar with how bitcoin works.

And at least if the attack is at a high enough rate, since the exhaustion will happen at the kernel before it gets to the bitcoin software, there isn't much for the bitcoin software to do. The host can implement firewall rules to mitigate, though even that can only work to the extent that the attack hasn't just effectively become volumetric.

It might be reasonable for the bitcoin authors to recommend some standard iptables rules that people should deploy as a best practice to protect their kernel's TCP stack (and avoid the issue that people will screw them up when coming up with their own).

[1] https://github.com/bitcoin/bitcoin/blob/master/src/node/evic...

pbear2k2111• 4 years ago

i considered this and needed clarification. i didn't know whether the p2p connections remained open or made frequent disconnect/reconnects. what happens to sync'd nodes with active peers is yet to be seen. it's too early, at least for me, to know whether peers would drop a node under attack over timeouts, how bitcoind behaves with peers while tcp/8333 is experiencing stress, etc.

nullc5• 4 years ago

A large portion of a nodes connections live as long as possible given the uptime of the connected nodes. Care is taken it protect long working connections to provide as strong a protection against new and short lived attacks as possible-- a working network should stay working. A sustained attack can frustrate newly connecting/restarting hosts when the recipient is publicly reachable and known to the attacker, but I think that's essentially insoluble (if nothing else, a volumetric attack would guarantee it).

If you're going to be making announcements and whatever, you probably should have taken the time to characterize your observations completely! The failure to do so makes it kinda just look like more lamesauce attempts at market manipulation (not to lob an accusation, it's just what it looks like -- there is a long history of that kind of activity).

it's too early, at least for me, to know whether peers would drop a node under attack over timeouts,

Do your homework! You're not the first person who ever thought of attacking a bitcoin node. While I'm sure there are areas for improvement, you're not likely to be able to make useful suggestions from a position of almost total ignorance.

CommitSyn• 4 years ago

There are many tools that will help you answer things like this i.e. Wireshark.

New Bitcoin DDoS Technique

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