Sliver is an open-source cross-platform adversary emulation/red team framework; organizations of all sizes can use it to perform security testing. Sliver's implants support C2 over Mutual TLS (mTLS), WireGuard, HTTP(S), and DNS and are dynamically compiled with per-binary asymmetric encryption keys.
The server and client support macOS, Windows, and Linux. Implants are supported on macOS, Windows, and Linux (and possibly every Golang compiler target, but we've not tested them all).
Source code and additional information can be found here: https://github.com/BishopFox/sliver