Mitigate single-host P2P Sybil attack

[jacksteroo]

Description

libp2p peer ID is based only on RSA public key. This allows an attacker to create unlimited number of nodes on a single machine (same IP address) and use these nodes to monopolize the incoming/outgoing connections of victim nodes.

Context

The current design allows incoming connections without checking against IP-based for duplicity. An attacker controlling a host may create a large number of libp2p peer IDs and create connection to a victim host under those peer IDs. This leads to a few problems:

• A victim host may run out of available file descriptors, leading to denial-of-service.
• Since libp2p pubsub uses a fixed number of outbound connections for outbound message propagation (6-8 by default), if the Sybil peers advertise critical topics (such as shard topics) the probability of the victim node choosing one of the sound, non-Sybil nodes for outbound messaging reaches zero.

Use case

If this is solved, this may lead to a use case where multiple nodes NAT'ed behind a gateway (using the same public/external IP address) may be affected. This will be out of the scope of this resolution. Support for NAT whitelisting as a configuration policy can be planned to mitigate this if we receive reports from validators regarding this issue.

See GitHub issue

Acceptance Criteria

• [ ] Adding a configurable parameter to allow a maximum of n-IP addresses (two by default)
• [ ] Gate incoming connections by their source IP address (with the max configured param), and dropping others
• [ ] Run a sybil attack simulation on the Testnet, from a single IP, to prove the effects, before and after
• [ ] Submit PR into Harmony repository to be reviewed
• [ ] Discuss with Harmony core team for PR to be approved and merged

Reward

USD $750 (in ONEs)

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Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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