#37466 [BC-Medium] Evil-client OOM crash (fast P2P crash)

Submitted on Dec 5th 2024 at 12:13:38 UTC by [redacted] for Attackathon | Ethereum Protocol

• Report ID: #37466

• Report Type: Blockchain/DLT

• Report severity: Medium

• Target: https://github.com/NethermindEth/nethermind

• Impacts:

  • Unintended chain split affecting greater than or equal to 25% of the network (Network partition)

Description

Brief/Intro

A new critical remote P2P crash vulnerability has been identified in Nethermind 1.29.1 (latest). If used in the wild it would result in netsplits - as is also seen in report #37120, although this crash is triggered significantly faster from a single attacking machine. To be precise - both attacks result in the same netsplits - with this attack just being a bit faster.

Vulnerability Details

Requesting block receipts isn't sufficiently rate-limited. By handshaking into nethermind, which oddly doesn't require the same 1 IP per 30 seconds rule as geth does, completing the handshakes and peering into victim nodes; it is possible to quickly crash any machine running the nethermind process, regardless of the machine's hardware.

Attack Scenario

An attacker would traverse the network to gather peer enode://hash@ip:port, and then weaponize a modified version of this attack script on a very, very small botnet - one that could be easily, and inexpensively built for less than $1000.

The script would be modified to target a list of public listening nodes as opposed to aiming it at a single test node, as we will be doing later in this report. It is as simple as the zombies running down the lists of online nodes running nethermind, crashing them inside of 30 - 60 seconds and moving onto the next, etc. in a simultaneous, scaled way that would certainly partition the network.

Attack code

Given the size of the attack script, over 1,000 lines, also given that it's something of a light Ethereum client, we have securely uploaded it to a private location in our internal Dropbox: https://www.dropbox.com/scl/fi/ulm9ql1o5hmcfvnrnhwin/receipts.go?rlkey=x1s7cexwa5nt4d91g9831q1yx&st=cx1cd8p6&dl=0 - the password to download the attack script is: alienbrain

Steps to reproduce (Ubuntu)

1. Open receipts.go in a text editor on your attack machine and change enodeURL := "enode://fefddae3a6fe5c04910ea0ffc7295969ebfac94cba0beaf07b8f0021020214852d24c5658cb4616f0d90d534870e1b28a052da9da2de5a920eec9dbd5112fe59@95.216.219.8:30303" to your test victim node's enode://hash@ip:port

2. Install go: snap install go --classic

3. ulimit -n 100000

4. go build receipts.go - and run the dependency commands it outputs, if any - then run go build receipts.go again.

5. ./receipts

6. Enter 50 threads - but feel free to experiment with this, and pauses, etc.

Outro and patch suggestion

This is an advanced attack given that it replicates what the remote peer expects of a valid peer, but is actually an evil peer that attacks from within by spamming the receipts protocol message. A patch is to simply rate limit the message because there is no rationale behind it not being limited.

Impact Details

Network partitioning affecting >25% of the network. A single attacker with an inconsequential amount of resources would likely short the markets and fracture the network.

Proof of Concept

Proof of Concept

We're attaching screenshots of the attack:

1. Before the attack

2. During the attack

3. After the attack

and again, we have also securely uploaded functioning attack code to a private location in our internal Dropbox: https://www.dropbox.com/scl/fi/ulm9ql1o5hmcfvnrnhwin/receipts.go?rlkey=x1s7cexwa5nt4d91g9831q1yx&st=cx1cd8p6&dl=0

Dropbox download password: alienbrain

Screenshots attached.