tendermint v0.33.3 Release Notes

  • April 6, 2020

    ๐Ÿš€ This security release fixes:

    Denial of service 1

    Tendermint 0.33.2 and earlier does not limit P2P connection requests number. For each p2p connection, Tendermint allocates ~0.5MB. Even though this memory is garbage collected once the connection is terminated (due to duplicate IP or reaching a maximum number of inbound peers), temporary memory spikes can lead to OOM (Out-Of-Memory) exceptions.

    Tendermint 0.33.3 (and 0.32.10) limits the total number of P2P incoming connection requests to to p2p.max_num_inbound_peers + len(p2p.unconditional_peer_ids).

    Notes:

    • Tendermint does not rate limit P2P connection requests per IP (an attacker can saturate all the inbound slots);
    • Tendermint does not rate limit HTTP(S) requests. If you expose any RPC endpoints to the public, please make sure to put in place some protection (https://www.nginx.com/blog/rate-limiting-nginx/). We may implement this in the future (#1696).

    Denial of service 2

    Tendermint 0.33.2 and earlier does not reclaim activeID of a peer after it's โœ‚ removed in Mempool reactor. This does not happen all the time. It only happens when a connection fails (for any reason) before the Peer is created and โž• added to all reactors. RemovePeer is therefore called before AddPeer, which leads to always growing memory (activeIDs map). The activeIDs map has a maximum size of 65535 and the node will panic if this map reaches the maximum. An attacker can create a lot of connection attempts (exploiting Denial of service 1), which ultimately will lead to the node panicking.

    Tendermint 0.33.3 (and 0.32.10) claims activeID for a peer in InitPeer, which is executed before MConnection is started.

    Notes:

    • InitPeer function was added to all reactors to combat a similar issue - #3338;
    • Denial of service 2 is independent of Denial of service 1 and can be executed without it.

    โฌ†๏ธ All clients are recommended to upgrade

    Special thanks to fudongbai for finding and reporting this.

    Friendly reminder, we have a bug bounty program.

    ๐Ÿ”’ SECURITY:

    • [mempool] Reserve IDs in InitPeer instead of AddPeer (@tessr)
    • [p2p] Limit the number of incoming connections (@melekes)