Sliver server crashes due to socks proxy nill pointer dereference

[Paradoxis]

Issue

We ran into the following issue during an engagement whereby the entire server went down due to a nill pointer dereference error.

Reproducing the bug

The issue occurred whilst proxying a large volume of RDP traffic (from Remmina) using proxychains with socks5, I'm unsure what packet exactly caused the issue though. Unfortunately I can't share a pcap due to privacy reasons

Version Info

Using the latest stable version v1.5.41

Stack Trace

[server] sliver > panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xb8 pc=0xf5cbd6]                                                                                                                                                                                                                                                                                                                                       
goroutine 6684 [running]:                                                                                                                                                                              
github.com/bishopfox/sliver/server/rpc.(*Server).SocksProxy.func2()                                                                                                                                            
github.com/bishopfox/sliver/server/rpc/rpc-socks.go:139 +0x76                                                                                                                                  
created by github.com/bishopfox/sliver/server/rpc.(*Server).SocksProxy                                                                                                                                         
github.com/bishopfox/sliver/server/rpc/rpc-socks.go:131 +0x45

[Paradoxis]

Appears to be a duplicate of #1290