Sliver is a command and control framework that uses a custom Wireguard netstack. In versions 1.5.43 and earlier, and in development version 1.6.0-dev, the netstack does not limit traffic between Wireguard clients. This allows clients to communicate with each other unrestrictedly, potentially enabling leaked or recovered keypairs to be used to attack operators or allowing port forwardings to be accessible from other implants.

Affected: Go: github.com/BishopFox/sliver

### Summary Sliver's custom Wireguard netstack doesn't limit traffic between Wireguard clients, this could lead to: 1. Leaked/recovered keypair (from a beacon) being used to attack operators. 2. Port forwardings usable from other implants.

### Details 1. Sliver treat operators' Wireguard config and beacon/session's Wireguard config equally, they both connect to the wireguard listener created from the CLI.

2. The current netstack implementation does not filter traffic between clients. I think this piece of code handle traffic between clients, from experimental results clients can ping and connect to each other freely, and I didn't see any filtering here either: ``` File: server\c2\wireguard.go 246: func socketWGWriteEnvelope(connection net.Conn, envelope *sliverpb.Envelope) error { 247: data, err := proto.Marshal(envelope) 248: if err != nil { 249: wgLog.Errorf("Envelope marshaling error: %v", err) 250: return err 251: } 252: dataLengthBuf := new(bytes.Buffer) 253: binary.Write(dataLengthBuf, binary.LittleEndian, uint32(len(data))) 254: connection.Write(dataLengthBuf.Bytes()) 255: connection.Write(data) 256: return nil 257: } 258:

``` 3. The docs says to use a Wireguard clients and operator wg-config to connect to the same WG listener as beacons: https://sliver.sh/docs?name=Port%20Forwarding

4. If the operator uses official wireguard clients that integrates with the OS's netstack (I'm using the [Windows client](https://www.wireguard.com/install/)) then thei…

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