CVE-2020-5303 (Go, published 2020-04-10T19:15Z)
Description: value: Tendermint before versions 0.33.3, 0.32.10, and 0.31.12 has a denial-of-service vulnerability. Tendermint does not limit the number of P2P connection requests. For each p2p connection, it allocates XXX bytes. 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. Additionally, Tendermint does not reclaim activeID of a peer after it's 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 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 above denial of service), which ultimately will lead to the node panicking. These issues are patched in Tendermint 0.33.3 and 0.32.10.
Severity: MEDIUM (CVSS v3 base score: 3.7)
Weakness: CWE-787 \u2014 Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
Repository: https://github.com/tendermint/tendermint
Files changed:
node/node.go
p2p/transport.go
p2p/transport_test.go
Commit message: p2p: limit the number of incoming connections

to p2p.max_num_inbound_peers + len(p2p.unconditional_peer_ids)


Vulnerable code:
	netAddr  NetAddress
	listener net.Listener

Fixed code:

	// Limit the number of incoming connections.
	max := config.P2P.MaxNumInboundPeers + len(splitAndTrimEmpty(config.P2P.UnconditionalPeerIDs, ",", " "))
	p2p.MultiplexTransportMaxIncomingConnections(max)(transport)

	"golang.org/x/net/netutil"
// MultiplexTransportMaxIncomingConnections sets the maximum number of
// simultaneous connections (incoming). Default: 0 (unlimited)
func MultiplexTransportMaxIncomingConnections(n int) MultiplexTransportOption {
	return func(mt *MultiplexTransport) { mt.maxIncomingConnections = n }
}

	netAddr                NetAddress
	listener               net.Listener
	maxIncomingConnections int // see MaxIncomingConnections
	if mt.maxIncomingConnections > 0 {
		ln = netutil.LimitListener(ln, mt.maxIncomingConnections)
	}

	"strings"
func TestTransportMultiplexMaxIncomingConnections(t *testing.T) {
	mt := newMultiplexTransport(
		emptyNodeInfo(),
		NodeKey{
			PrivKey: ed25519.GenPrivKey(),
		},
	)
	id := mt.nodeKey.ID()

	MultiplexTransportMaxIncomingConnections(0)(mt)

	addr, err := NewNetAddressString(IDAddressString(id, "127.0.0.1:0"))
	if err != nil {
		t.Fatal(err)
	}

	if err := mt.Listen(*addr); err != nil {
		t.Fatal(err)
	}

	errc := make(chan error)

	go func() {
		addr := NewNetAddress(id, mt.listener.Addr())

		_, err := addr.Dial()
		if err != nil {
			errc <- err
			return
		}

		close(errc)
	}()

	if err := <-errc; err != nil {
		t.Errorf("connection failed: %v", err)
	}

	_, err = mt.Accept(peerConfig{})
	if err == nil || !strings.Contains(err.Error(), "connection reset by peer") {
		t.Errorf("expected connection reset by peer error, got %v", err)
	}
}