Add project files

.gitignore

@@ -20,3 +20,6 @@
 # Go workspace file
 go.work
 go.work.sum
+
+# build
+ass

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2024 Julian Müller
+Copyright (c) 2024 Julian Müller (ChaoticByte)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

args.go

@@ -0,0 +1,30 @@
+package main
+
+// Copyright (c) 2024 Julian Müller (ChaoticByte)
+// License: MIT
+
+import (
+	"flag"
+)
+
+var configFilepath string
+var privateKeyFilepath string
+var logFlag bool
+
+func ParseCommandline() bool {
+	flag.StringVar(&configFilepath, "config", "", "The path to the config file (required)")
+	flag.StringVar(&privateKeyFilepath, "pkey", "", "The path to the private key file (required)")
+	flag.BoolVar(&logFlag, "log", false, "Enable logging of messages")
+	flag.Parse()
+	missing := false
+	if configFilepath == "" {
+		missing = true
+	}
+	if privateKeyFilepath == "" {
+		missing = true
+	}
+	if missing {
+		flag.Usage()
+	}
+	return !missing
+}

config.example.yml

@@ -0,0 +1,8 @@
+# Example server config file
+host: ''
+port: 8022
+clients:
+  # This are just examples. Please generate your own keypair for each client you want to add.
+  # username: public-key
+  example1: ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIEg9AzPuPe/zv0HszL+aRdJgZ8DPwVLV59FJoUHe7kWH
+  example2: ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIQH6ESwEHVvlbxZJd7JhTPWXy3yQ5Zaf8qVBxzf6Td/

config.go

@@ -0,0 +1,24 @@
+package main
+
+// Copyright (c) 2024 Julian Müller (ChaoticByte)
+// License: MIT
+
+import (
+	"log"
+	"os"
+
+	"github.com/goccy/go-yaml"
+)
+
+var config struct {
+	Host string `yaml:"host"`
+	Port int `yaml:"port"`
+	Clients map[string]string `yaml:"clients"`
+}
+
+func ParseConfig(filepath string) {
+	data, err := os.ReadFile(filepath)
+	if err != nil { log.Fatal(err) }
+	err = yaml.Unmarshal(data, &config)
+	if err != nil { log.Fatal(err) }
+}

go.mod

@@ -0,0 +1,17 @@
+module github.com/ChaoticByte/ass
+go 1.22.4
+
+require (
+	github.com/gliderlabs/ssh v0.3.7
+	github.com/goccy/go-yaml v1.11.3
+)
+
+require (
+	github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be // indirect
+	github.com/fatih/color v1.17.0 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	golang.org/x/crypto v0.24.0 // indirect
+	golang.org/x/sys v0.21.0 // indirect
+	golang.org/x/xerrors v0.0.0-20231012003039-104605ab7028 // indirect
+)

go.sum

@@ -0,0 +1,43 @@
+github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be h1:9AeTilPcZAjCFIImctFaOjnTIavg87rW78vTPkQqLI8=
+github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be/go.mod h1:ySMOLuWl6zY27l47sB3qLNK6tF2fkHG55UZxx8oIVo4=
+github.com/fatih/color v1.10.0 h1:s36xzo75JdqLaaWoiEHk767eHiwo0598uUxyfiPkDsg=
+github.com/fatih/color v1.10.0/go.mod h1:ELkj/draVOlAH/xkhN6mQ50Qd0MPOk5AAr3maGEBuJM=
+github.com/fatih/color v1.17.0 h1:GlRw1BRJxkpqUCBKzKOw098ed57fEsKeNjpTe3cSjK4=
+github.com/fatih/color v1.17.0/go.mod h1:YZ7TlrGPkiz6ku9fK3TLD/pl3CpsiFyu8N92HLgmosI=
+github.com/gliderlabs/ssh v0.3.7 h1:iV3Bqi942d9huXnzEF2Mt+CY9gLu8DNM4Obd+8bODRE=
+github.com/gliderlabs/ssh v0.3.7/go.mod h1:zpHEXBstFnQYtGnB8k8kQLol82umzn/2/snG7alWVD8=
+github.com/go-playground/locales v0.13.0 h1:HyWk6mgj5qFqCT5fjGBuRArbVDfE4hi8+e8ceBS/t7Q=
+github.com/go-playground/locales v0.13.0/go.mod h1:taPMhCMXrRLJO55olJkUXHZBHCxTMfnGwq/HNwmWNS8=
+github.com/go-playground/universal-translator v0.17.0 h1:icxd5fm+REJzpZx7ZfpaD876Lmtgy7VtROAbHHXk8no=
+github.com/go-playground/universal-translator v0.17.0/go.mod h1:UkSxE5sNxxRwHyU+Scu5vgOQjsIJAF8j9muTVoKLVtA=
+github.com/go-playground/validator/v10 v10.4.1 h1:pH2c5ADXtd66mxoE0Zm9SUhxE20r7aM3F26W0hOn+GE=
+github.com/go-playground/validator/v10 v10.4.1/go.mod h1:nlOn6nFhuKACm19sB/8EGNn9GlaMV7XkbRSipzJ0Ii4=
+github.com/goccy/go-yaml v1.11.3 h1:B3W9IdWbvrUu2OYQGwvU1nZtvMQJPBKgBUuweJjLj6I=
+github.com/goccy/go-yaml v1.11.3/go.mod h1:wKnAMd44+9JAAnGQpWVEgBzGt3YuTaQ4uXoHvE4m7WU=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/leodido/go-urn v1.2.0 h1:hpXL4XnriNwQ/ABnpepYM/1vCLWNDfUNts8dX3xTG6Y=
+github.com/leodido/go-urn v1.2.0/go.mod h1:+8+nEpDfqqsY+g338gtMEUOtuK+4dEMhiQEgxpxOKII=
+github.com/mattn/go-colorable v0.1.8 h1:c1ghPdyEDarC70ftn0y+A/Ee++9zz8ljHG1b13eJ0s8=
+github.com/mattn/go-colorable v0.1.8/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
+github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
+github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+golang.org/x/crypto v0.24.0 h1:mnl8DM0o513X8fdIkmyFE/5hTYxbwYOjDS/+rK6qpRI=
+golang.org/x/crypto v0.24.0/go.mod h1:Z1PMYSOR5nyMcyAVAIQSKCDwalqy85Aqn1x3Ws4L5DM=
+golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.21.0 h1:rF+pYz3DAGSQAxAu1CbC7catZg4ebC4UIeIhKxBZvws=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.21.0 h1:WVXCp+/EBEHOj53Rvu+7KiT/iElMrO8ACK16SMZ3jaA=
+golang.org/x/term v0.21.0/go.mod h1:ooXLefLobQVslOqselCNF4SxFAaoS6KujMbsGzSDmX0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20231012003039-104605ab7028 h1:+cNy6SZtPcJQH3LJVLOSmiC7MMxXNOb3PU/VUEz+EhU=
+golang.org/x/xerrors v0.0.0-20231012003039-104605ab7028/go.mod h1:NDW/Ps6MPRej6fsCIbMTohpP40sJ/P/vI1MoTEGwX90=

main.go

@@ -0,0 +1,15 @@
+package main
+
+// Copyright (c) 2024 Julian Müller (ChaoticByte)
+// License: MIT
+
+import "os"
+
+func main() {
+	if ParseCommandline() {
+		ParseConfig(configFilepath)
+		RunServer()
+	} else {
+		os.Exit(1)
+	}
+}

ssh.go

@@ -0,0 +1,119 @@
+package main
+
+// Copyright (c) 2024 Julian Müller (ChaoticByte)
+// License: MIT
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"slices"
+	"sync"
+
+	"github.com/gliderlabs/ssh"
+)
+
+var sessionListMutex = &sync.Mutex{}
+var sessionList = []*ssh.Session{}
+
+func PubkeyAuth(ctx ssh.Context, key ssh.PublicKey) bool {
+	// verify public key for auth
+	u := ctx.User()
+	pubkey := config.Clients[u]
+	if pubkey == "" { // username not in config.Clients
+		log.Printf("Authentication failure: Unknown user %s", u)
+		return false
+	}
+	k, _, _, _, err := ssh.ParseAuthorizedKey([]byte(pubkey))
+	if err != nil {
+		log.Printf("Authentication failure: Could not parse public key for %s", u)
+	}
+	if ssh.KeysEqual(k, key) {
+		return true // bassd
+	} else {
+		log.Printf("Authentication failure: Invalid public key for user %s", u)
+		return false
+	}
+}
+
+func AddToSessionList(s *ssh.Session) int {
+	// add new session to list
+	var idx int = -1
+	sessionListMutex.Lock()
+	defer sessionListMutex.Unlock()
+	lenClientList := len(sessionList)
+	// try to reuse an existing nil position in the slice
+	for i := range(lenClientList) {
+		if sessionList[i] == nil {
+			// we found one!
+			sessionList[i] = s
+			idx = i
+			break
+		}
+	}
+	if idx == -1 {
+		// we have to append
+		sessionList = append(sessionList, s)
+		idx = lenClientList
+	}
+	return idx
+}
+
+func RemoveFromSessionList(idx int) {
+	sessionListMutex.Lock()
+	defer sessionListMutex.Unlock()
+	// we have to set it to nil instead of constructing a new
+	// slice, so that the other session handlers have still
+	// the correct index for their own removal
+	sessionList[idx] = nil // session associated with the pointer reference should be freed automatically
+}
+
+func BroadcastLine(line []byte) {
+	if logFlag { log.Printf("%s", line) } // output message
+	sessions := sessionList // create snapshot of client list
+	for i := range(len(sessions)) {
+		session := sessions[i]
+		if session != nil {
+			(*session).Write(line)
+		}
+	}
+}
+
+func HandleSession(session ssh.Session) {
+	// get username
+	user := session.Context().User()
+	msgPrefix := []byte(fmt.Sprintf("%s: ", user))
+	// Add client to list
+	sessionListIdx := AddToSessionList(&session)
+	defer func () { // cleanup tasks
+		RemoveFromSessionList(sessionListIdx)
+		log.Printf("User %s disconnected.\n", user)
+		BroadcastLine([]byte(fmt.Sprintf("[disconnected] %s\n", user)))
+	}()
+	// helo
+	log.Printf("User %s connected.\n", user)
+	BroadcastLine([]byte(fmt.Sprintf("[connected] %s\n", user)))
+	// IO
+	linebuf := bufio.NewReader(session)
+	for {
+		line, err := linebuf.ReadBytes('\n')
+		if err != nil {
+			if err.Error() != "EOF" {
+				log.Println("An error occurred! ", user, " ", err)
+			}
+			break // disconnect
+		} else {
+			BroadcastLine(slices.Concat(msgPrefix, line))
+		}
+	}
+}
+
+func RunServer() {
+	log.Printf("Starting SSH server on %s:%v", config.Host, config.Port)
+	log.Fatal(ssh.ListenAndServe(
+		fmt.Sprintf("%s:%v", config.Host, config.Port),
+		HandleSession,
+		ssh.HostKeyFile(privateKeyFilepath),
+		ssh.PublicKeyAuth(PubkeyAuth),
+		ssh.NoPty()))
+}