95 lines
2.6 KiB
Go
95 lines
2.6 KiB
Go
package sshrpc
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import (
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"fmt"
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"log"
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"net/rpc"
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"dev.justinjudd.org/justin/easyssh"
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"golang.org/x/crypto/ssh"
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)
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// DefaultRPCChannel is the Channel Name that will be used to carry the RPC traffic, can be changed in Serverr and Client
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const DefaultRPCChannel = "RPCChannel"
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// RPCSubsystem is the subsystem that will be used to trigger RPC endpoint creation
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const RPCSubsystem = "RPCSubsystem"
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// CallbackFunc to be called when reverse RPC client is created
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type CallbackFunc func(RPCClient *rpc.Client, conn ssh.Conn)
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// Server represents an SSH Server that spins up RPC servers when requested.
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type Server struct {
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*rpc.Server
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Config *ssh.ServerConfig
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ChannelName string
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CallbackFunc
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}
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// NewServer returns a new Server to handle incoming SSH and RPC requests.
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func NewServer() *Server {
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c := &ssh.ServerConfig{
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PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
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if c.User() == "sshrpc" && string(pass) == "sshrpc" {
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return nil, nil
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}
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return nil, fmt.Errorf("password rejected for %q", c.User())
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},
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}
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return &Server{Server: rpc.NewServer(), Config: c, ChannelName: DefaultRPCChannel}
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}
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// StartServer starts the server listening for requests
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func (s *Server) StartServer(address string) {
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server := easyssh.Server{Addr: address, Config: s.Config}
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handler := easyssh.NewSSHConnHandler()
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channelsMux := easyssh.NewChannelsMux()
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channelsMux.HandleChannel(s.ChannelName, s)
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handler.MultipleChannelsHandler = channelsMux
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server.Handler = handler
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server.ListenAndServe()
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}
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func (s *Server) HandleChannel(newChannel ssh.NewChannel, channel ssh.Channel, reqs <-chan *ssh.Request, sshConn ssh.Conn) {
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go func(in <-chan *ssh.Request) {
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for req := range in {
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ok := false
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switch req.Type {
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case easyssh.SubsystemRequest:
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ok = true
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log.Printf("subsystem '%s'", req.Payload[4:])
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switch string(req.Payload[4:]) {
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//RPCSubsystem Request made indicates client desires RPC Server access
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case RPCSubsystem:
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go s.ServeConn(channel)
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log.Printf("Started SSH RPC")
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// triggers reverse RPC connection as well
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clientChannel, err := openRPCClientChannel(sshConn, s.ChannelName+"-reverse")
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if err != nil {
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log.Printf("Failed to create client channel: " + err.Error())
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continue
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}
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rpcClient := rpc.NewClient(clientChannel)
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if s.CallbackFunc != nil {
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s.CallbackFunc(rpcClient, sshConn)
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}
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log.Printf("Started SSH RPC client")
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default:
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log.Printf("Unknown subsystem: %s", req.Payload)
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}
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}
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if !ok {
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log.Printf("declining %s request...", req.Type)
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}
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req.Reply(ok, nil)
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}
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}(reqs)
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}
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