style: match the user select to the panel buttons

- agent reports the OS user it runs as (enroll + poll header)
- per-machine terminal user on the edit page; defaults to the agent's own user (root on Linux)
- create a new user from the panel: name, password, optional sudo group
- show the reason in the terminal when a shell fails to start
- bump version to 0.0.2

README.md

@@ -2,7 +2,7 @@
 
 Лёгкий self-hosted сервис для доступа к Linux-машинам **без белого IP** (за NAT).
 Агент на клиенте сам исходяще подключается к серверу по HTTP long-polling; админ
-в веб-панели видит список машин и открывает по каждой **root-терминал в браузере**.
+в веб-панели видит список машин и открывает по каждой **терминал в браузере** (по умолчанию от root, пользователя можно сменить).
 
 ```
 браузер ──WS──> [nginx :8445 TLS] ──> [Go server 127.0.0.1:8091] <──long-poll── агент (root, за NAT)
@@ -42,10 +42,16 @@ curl -fsSL https://localhost:8445/install.sh | sudo HOST=https://localhost:8445
 curl -fsSL https://localhost:8445/install.sh | sudo sh
 ```
 
+## Пользователь терминала
+По умолчанию терминал открывается от пользователя, под которым запущен агент (на Linux — root).
+В окне «Изменить машину» можно выбрать другого пользователя машины или создать нового
+(имя, пароль, опционально — добавить в sudo). Смена и создание работают, только если агент запущен от root.
+Файловый менеджер по-прежнему работает от пользователя агента.
+
 ## Безопасность
 - Пароли админов — bcrypt; сессии в HttpOnly/Secure/SameSite куках; CSRF на формах; rate-limit логина.
 - Агенты: общий enroll-секрет → индивидуальный токен (хранится хешем, сверка constant-time).
-- Открытие терминала пишется в таблицу `audit` (терминал даёт root-доступ).
+- Открытие терминала пишется в таблицу `audit` (терминал даёт root-доступ), как и смена/создание пользователя.
 
 ## Скриншоты
 <img width="1256" height="709" alt="image" src="https://github.com/user-attachments/assets/5f0b30f1-d5e3-4b62-817e-4041641df6e3" />

VERSION.txt

@@ -1 +1 @@
-0.0.1
+0.0.2

internal/agent/client.go

@@ -120,6 +120,7 @@ func (a *Agent) enroll(ctx context.Context) error {
 		OS:       runtime.GOOS,
 		Arch:     runtime.GOARCH,
 		Version:  Version,
+		User:     currentUser(),
 	})
 	req, _ := http.NewRequestWithContext(ctx, http.MethodPost, a.cfg.Host+"/api/agent/enroll", bytes.NewReader(body))
 	req.Header.Set("X-Enroll-Secret", a.cfg.EnrollSecret)
@@ -145,11 +146,12 @@ func (a *Agent) enroll(ctx context.Context) error {
 func (a *Agent) pollOnce(ctx context.Context) error {
 	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, a.cfg.Host+"/api/agent/poll", nil)
 	a.authHeaders(req)
-	// Report the version occasionally (not every poll), so the panel can flag
+	// Report the version and our OS user occasionally (not every poll), so the
-	// outdated agents without extra traffic.
+	// panel can flag outdated agents without extra traffic.
 	a.pollCount++
 	if a.pollCount%20 == 1 {
 		req.Header.Set("X-Agent-Version", Version)
+		req.Header.Set("X-Agent-User", currentUser())
 	}
 	resp, err := a.http.Do(req)
 	if err != nil {
@@ -169,7 +171,7 @@ func (a *Agent) pollOnce(ctx context.Context) error {
 	// Dispatch in the background so we keep polling for more work.
 	switch msg.Type {
 	case proto.CtrlOpenTerminal:
-		go a.runTerminal(ctx, msg.SessionID)
+		go a.runTerminal(ctx, msg.SessionID, msg.User)
 	case proto.CtrlOpenForward:
 		go a.runForward(ctx, msg.SessionID, msg.Port)
 	case proto.CtrlTask:

internal/agent/session.go

@@ -15,14 +15,17 @@ import (
 )
 
 // runTerminal spawns a PTY and bridges it to the session.
-func (a *Agent) runTerminal(parent context.Context, sid string) {
+// user is the OS user to run the shell as ("" = the agent's own user).
-	term, err := StartPTY()
+func (a *Agent) runTerminal(parent context.Context, sid, user string) {
+	term, err := StartPTY(user)
 	if err != nil {
 		log.Printf("term %s: start pty: %v", sid, err)
+		// Show the reason in the browser terminal before closing it.
+		a.postOut(context.Background(), sid, proto.OutMessage{Data: b64.EncodeToString([]byte("lpra: " + err.Error() + "\r\n"))})
 		a.postOut(context.Background(), sid, proto.OutMessage{Exit: true})
 		return
 	}
-	log.Printf("term %s: shell started", sid)
+	log.Printf("term %s: shell started (user %q)", sid, user)
 	a.bridgeStream(parent, sid, term, term.Resize)
 	log.Printf("term %s: ended", sid)
 }

internal/agent/task.go

@@ -54,9 +54,10 @@ func (a *Agent) postResult(ctx context.Context, taskID string, res proto.TaskRes
 	resp.Body.Close()
 }
 
-// execTask runs a single file-manager operation natively and returns a result.
+// execTask runs a single file-manager or user-management operation natively
+// and returns a result.
 func (a *Agent) execTask(env proto.TaskEnvelope) proto.TaskResult {
-	data, err := dispatchFS(env)
+	data, err := dispatchTask(env)
 	if err != nil {
 		return proto.TaskResult{Error: err.Error()}
 	}

internal/agent/terminal.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"fmt"
 	"os"
 	"os/exec"
 
@@ -13,14 +14,30 @@ type PTY struct {
 	f   *os.File
 }
 
-// StartPTY launches the shell attached to a new PTY. The agent runs as root
+// StartPTY launches a login shell attached to a new PTY. With user empty (or
-// (systemd User=root), so this is a root shell by design.
+// equal to the agent's own user) it is the agent's shell — root by default,
-func StartPTY() (*PTY, error) {
+// since the agent runs as a root systemd service. Any other user is entered via
-	shell := "/bin/bash"
+// `su -l`, which only a root agent can do without a password.
-	if _, err := os.Stat(shell); err != nil {
+func StartPTY(user string) (*PTY, error) {
-		shell = "/bin/sh"
+	var cmd *exec.Cmd
+	if user == "" || user == currentUser() {
+		cmd = exec.Command(defaultShell(), "-l")
+	} else {
+		if !validUserName(user) {
+			return nil, fmt.Errorf("недопустимое имя пользователя %q", user)
+		}
+		if os.Geteuid() != 0 {
+			return nil, fmt.Errorf("агент запущен от %s и не может открыть сессию от %s", currentUser(), user)
+		}
+		if !userExists(user) {
+			return nil, fmt.Errorf("пользователь %s не найден", user)
+		}
+		su, err := exec.LookPath("su")
+		if err != nil {
+			return nil, fmt.Errorf("su не найден: %w", err)
+		}
+		cmd = exec.Command(su, "-l", user)
 	}
-	cmd := exec.Command(shell, "-l")
 	cmd.Env = append(os.Environ(), "TERM=xterm-256color")
 	f, err := pty.Start(cmd)
 	if err != nil {

internal/agent/users.go

@@ -0,0 +1,235 @@
+package agent
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/user"
+	"regexp"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+
+	"github.com/x-grk/longpolling-remote-access/internal/proto"
+)
+
+// userNameRe is the login name shape accepted for existing users; it keeps a
+// name from ever being parsed as an option by su. newUserNameRe is the stricter
+// shape useradd accepts everywhere.
+var (
+	userNameRe    = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_.-]{0,31}$`)
+	newUserNameRe = regexp.MustCompile(`^[a-z_][a-z0-9_-]{0,31}$`)
+)
+
+func validUserName(name string) bool { return userNameRe.MatchString(name) }
+
+// dispatchTask runs one task: user management here, everything else is a
+// file-manager operation.
+func dispatchTask(env proto.TaskEnvelope) (any, error) {
+	switch env.Type {
+	case proto.TaskSysUsers:
+		return sysUsers(), nil
+	case proto.TaskSysUserAdd:
+		var a proto.SysUserAddArgs
+		_ = json.Unmarshal(env.Args, &a)
+		return nil, addUser(a)
+	}
+	return dispatchFS(env)
+}
+
+// currentUser is the OS user the agent process runs as.
+func currentUser() string {
+	if u, err := user.Current(); err == nil && u.Username != "" {
+		return u.Username
+	}
+	if os.Geteuid() == 0 {
+		return "root"
+	}
+	if n := os.Getenv("USER"); n != "" {
+		return n
+	}
+	return strconv.Itoa(os.Geteuid())
+}
+
+func userExists(name string) bool {
+	if _, err := user.Lookup(name); err == nil {
+		return true
+	}
+	// Without cgo, os/user only reads /etc/passwd, which macOS doesn't use.
+	if runtime.GOOS == "darwin" {
+		for _, n := range darwinUsers() {
+			if n == name {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func defaultShell() string {
+	if _, err := os.Stat("/bin/bash"); err == nil {
+		return "/bin/bash"
+	}
+	return "/bin/sh"
+}
+
+// sysUsers reports who the agent is and which users a terminal can be opened as.
+func sysUsers() proto.SysUsersResult {
+	cur := currentUser()
+	res := proto.SysUsersResult{Current: cur, CanSwitch: os.Geteuid() == 0, Users: []string{cur}}
+	if !res.CanSwitch {
+		return res
+	}
+	seen := map[string]bool{cur: true}
+	for _, n := range loginUsers() {
+		if !seen[n] && validUserName(n) {
+			seen[n] = true
+			res.Users = append(res.Users, n)
+		}
+	}
+	sort.Strings(res.Users[1:])
+	return res
+}
+
+// loginUsers lists root plus the regular (non-system) accounts with a real shell.
+func loginUsers() []string {
+	if runtime.GOOS == "darwin" {
+		return darwinUsers()
+	}
+	b, err := os.ReadFile("/etc/passwd")
+	if err != nil {
+		return nil
+	}
+	var out []string
+	for _, line := range strings.Split(string(b), "\n") {
+		// name:passwd:uid:gid:gecos:home:shell
+		f := strings.Split(line, ":")
+		if len(f) < 7 || strings.HasPrefix(line, "#") {
+			continue
+		}
+		uid, err := strconv.Atoi(f[2])
+		if err != nil || (uid != 0 && (uid < 1000 || uid == 65534)) {
+			continue
+		}
+		if sh := f[6]; strings.HasSuffix(sh, "/nologin") || strings.HasSuffix(sh, "/false") {
+			continue
+		}
+		out = append(out, f[0])
+	}
+	return out
+}
+
+func darwinUsers() []string {
+	b, err := exec.Command("dscl", ".", "-list", "/Users", "UniqueID").Output()
+	if err != nil {
+		return nil
+	}
+	var out []string
+	for _, line := range strings.Split(string(b), "\n") {
+		f := strings.Fields(line)
+		if len(f) != 2 {
+			continue
+		}
+		if uid, err := strconv.Atoi(f[1]); err == nil && (uid == 0 || uid >= 500) {
+			out = append(out, f[0])
+		}
+	}
+	return out
+}
+
+// addUser creates an OS user with a home directory, optionally sets its
+// password and adds it to the sudo group.
+func addUser(a proto.SysUserAddArgs) error {
+	if runtime.GOOS != "linux" {
+		return errors.New("создание пользователей поддерживается только на Linux")
+	}
+	if os.Geteuid() != 0 {
+		return errors.New("агент запущен не от root и не может создавать пользователей")
+	}
+	if !newUserNameRe.MatchString(a.Name) {
+		return errors.New("недопустимое имя: строчные латинские буквы, цифры, '_' и '-', до 32 символов")
+	}
+	if strings.ContainsAny(a.Password, "\r\n") {
+		return errors.New("пароль не должен содержать перевод строки")
+	}
+	if userExists(a.Name) {
+		return fmt.Errorf("пользователь %s уже существует", a.Name)
+	}
+	// Resolve the sudo group up front so we don't leave a half-configured user.
+	group := ""
+	if a.Sudo {
+		if group = sudoGroup(); group == "" {
+			return errors.New("на машине нет группы sudo или wheel")
+		}
+	}
+
+	switch {
+	case hasCmd("useradd"):
+		if err := run(nil, "useradd", "-m", "-s", defaultShell(), a.Name); err != nil {
+			return err
+		}
+	case hasCmd("adduser"): // BusyBox / Alpine
+		if err := run(nil, "adduser", "-D", "-s", defaultShell(), a.Name); err != nil {
+			return err
+		}
+	default:
+		return errors.New("не найдены useradd/adduser")
+	}
+
+	if a.Password != "" {
+		if err := run([]byte(a.Name+":"+a.Password+"\n"), "chpasswd"); err != nil {
+			return fmt.Errorf("пользователь создан, но пароль не задан: %w", err)
+		}
+	}
+	if group != "" {
+		var err error
+		switch {
+		case hasCmd("usermod"):
+			err = run(nil, "usermod", "-aG", group, a.Name)
+		case hasCmd("gpasswd"):
+			err = run(nil, "gpasswd", "-a", a.Name, group)
+		default: // BusyBox: adduser USER GROUP
+			err = run(nil, "adduser", a.Name, group)
+		}
+		if err != nil {
+			return fmt.Errorf("пользователь создан, но не добавлен в %s: %w", group, err)
+		}
+	}
+	return nil
+}
+
+// sudoGroup returns the group that grants sudo on this distro, or "".
+func sudoGroup() string {
+	for _, g := range []string{"sudo", "wheel"} {
+		if _, err := user.LookupGroup(g); err == nil {
+			return g
+		}
+	}
+	return ""
+}
+
+func hasCmd(name string) bool {
+	_, err := exec.LookPath(name)
+	return err == nil
+}
+
+// run executes a command (optionally feeding stdin) and folds its output into
+// the error so the panel can show why it failed.
+func run(stdin []byte, name string, args ...string) error {
+	cmd := exec.Command(name, args...)
+	if stdin != nil {
+		cmd.Stdin = bytes.NewReader(stdin)
+	}
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		if msg := strings.TrimSpace(string(out)); msg != "" {
+			return fmt.Errorf("%s: %s", name, msg)
+		}
+		return fmt.Errorf("%s: %w", name, err)
+	}
+	return nil
+}

internal/proto/proto.go

@@ -27,6 +27,7 @@ type EnrollRequest struct {
 	OS       string `json:"os"`
 	Arch     string `json:"arch"`
 	Version  string `json:"version"`
+	User     string `json:"user,omitempty"` // OS user the agent runs as
 }
 
 // EnrollResponse carries the identity the agent persists and uses from then on.
@@ -41,6 +42,7 @@ type ControlMessage struct {
 	SessionID string `json:"session_id,omitempty"`
 	Port      int    `json:"port,omitempty"`    // CtrlOpenForward: client-side port to dial
 	TaskID    string `json:"task_id,omitempty"` // CtrlTask
+	User      string `json:"user,omitempty"`    // CtrlOpenTerminal: OS user for the shell ("" = the agent's own)
 }
 
 // Terminal / stream frame types on the session "in" channel (server -> agent).
@@ -84,7 +86,9 @@ const (
 	TaskFSMove     = "fs.move"     // move/rename
 	TaskFSDownload = "fs.download" // read a whole file (larger cap) for browser download
 
-	TaskSysUpdate = "sys.update" // download the latest agent binary and restart
+	TaskSysUpdate  = "sys.update"  // download the latest agent binary and restart
+	TaskSysUsers   = "sys.users"   // report the agent's user and the login-capable users
+	TaskSysUserAdd = "sys.useradd" // create a new OS user
 )
 
 // TaskEnvelope is what the agent fetches for a task id.
@@ -144,3 +148,17 @@ type FSReadResult struct {
 	Truncated bool   `json:"truncated"`
 	Binary    bool   `json:"binary"`
 }
+
+// SysUsersResult is returned for TaskSysUsers.
+type SysUsersResult struct {
+	Current   string   `json:"current"`    // user the agent runs as
+	CanSwitch bool     `json:"can_switch"` // agent is root, so it can open shells as (and create) other users
+	Users     []string `json:"users"`
+}
+
+// SysUserAddArgs are the arguments of TaskSysUserAdd.
+type SysUserAddArgs struct {
+	Name     string `json:"name"`
+	Password string `json:"password,omitempty"` // empty leaves the account without a password
+	Sudo     bool   `json:"sudo"`               // add to the sudo/wheel group
+}

internal/server/agents.go

@@ -34,7 +34,7 @@ func bearerToken(r *http.Request) string {
 
 // enroll creates a new agent record for a valid enroll secret and returns the
 // generated id plus a one-time plaintext token (only the hash is stored).
-func (s *Server) enroll(name, hostname, os, arch, version string) (id, token string, err error) {
+func (s *Server) enroll(name, hostname, os, arch, version, runUser string) (id, token string, err error) {
 	id = randToken()[:16]
 	token = randToken()
 	a := Agent{
@@ -44,6 +44,7 @@ func (s *Server) enroll(name, hostname, os, arch, version string) (id, token str
 		OS:        os,
 		Arch:      arch,
 		Version:   version,
+		RunUser:   runUser,
 		TokenHash: hashToken(token),
 	}
 	if err = s.db.CreateAgent(a); err != nil {

internal/server/db.go

@@ -59,6 +59,8 @@ CREATE TABLE IF NOT EXISTS agents (
     arch        TEXT NOT NULL,
     token_hash  TEXT NOT NULL,
     version     TEXT NOT NULL DEFAULT '',
+    run_user    TEXT NOT NULL DEFAULT '',
+    login_user  TEXT NOT NULL DEFAULT '',
     enrolled_at INTEGER NOT NULL,
     last_seen   INTEGER NOT NULL
 );
@@ -101,6 +103,8 @@ CREATE TABLE IF NOT EXISTS forward_rules (
 		`ALTER TABLE forward_rules ADD COLUMN proto TEXT NOT NULL DEFAULT 'http'`,
 		`ALTER TABLE agents ADD COLUMN version TEXT NOT NULL DEFAULT ''`,
 		`ALTER TABLE ufw_rules ADD COLUMN rule_id INTEGER NOT NULL DEFAULT 0`,
+		`ALTER TABLE agents ADD COLUMN run_user TEXT NOT NULL DEFAULT ''`,
+		`ALTER TABLE agents ADD COLUMN login_user TEXT NOT NULL DEFAULT ''`,
 	} {
 		if _, err := db.sql.Exec(alter); err != nil && !strings.Contains(err.Error(), "duplicate column") {
 			return err
@@ -222,9 +226,18 @@ type Agent struct {
 	Arch      string
 	TokenHash string
 	Version   string
+	RunUser   string // OS user the agent process runs as (reported by the agent)
+	LoginUser string // OS user terminals are opened as; "" = RunUser
 	LastSeen  time.Time
 }
 
+// TerminalUser is the OS user a terminal on this agent runs as. Agents are
+// installed as a root systemd service, so that is the fallback for agents too
+// old to report their user.
+func (a Agent) TerminalUser() string {
+	return firstNonEmpty(a.LoginUser, a.RunUser, "root")
+}
+
 // Online reports whether the agent polled recently enough to be considered up.
 func (a Agent) Online() bool {
 	return time.Since(a.LastSeen) < 45*time.Second
@@ -233,9 +246,9 @@ func (a Agent) Online() bool {
 func (db *DB) CreateAgent(a Agent) error {
 	now := time.Now().Unix()
 	_, err := db.sql.Exec(
-		`INSERT INTO agents(id, name, hostname, os, arch, token_hash, version, enrolled_at, last_seen)
+		`INSERT INTO agents(id, name, hostname, os, arch, token_hash, version, run_user, enrolled_at, last_seen)
-		 VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		 VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
-		a.ID, a.Name, a.Hostname, a.OS, a.Arch, a.TokenHash, a.Version, now, now)
+		a.ID, a.Name, a.Hostname, a.OS, a.Arch, a.TokenHash, a.Version, a.RunUser, now, now)
 	return err
 }
 
@@ -243,8 +256,8 @@ func (db *DB) GetAgent(id string) (*Agent, error) {
 	a := &Agent{}
 	var last int64
 	err := db.sql.QueryRow(
-		`SELECT id, name, hostname, os, arch, token_hash, version, last_seen FROM agents WHERE id = ?`, id).
+		`SELECT id, name, hostname, os, arch, token_hash, version, run_user, login_user, last_seen FROM agents WHERE id = ?`, id).
-		Scan(&a.ID, &a.Name, &a.Hostname, &a.OS, &a.Arch, &a.TokenHash, &a.Version, &last)
+		Scan(&a.ID, &a.Name, &a.Hostname, &a.OS, &a.Arch, &a.TokenHash, &a.Version, &a.RunUser, &a.LoginUser, &last)
 	if err == sql.ErrNoRows {
 		return nil, nil
 	}
@@ -257,7 +270,7 @@ func (db *DB) GetAgent(id string) (*Agent, error) {
 
 func (db *DB) ListAgents() ([]Agent, error) {
 	rows, err := db.sql.Query(
-		`SELECT id, name, hostname, os, arch, version, last_seen FROM agents ORDER BY name`)
+		`SELECT id, name, hostname, os, arch, version, run_user, login_user, last_seen FROM agents ORDER BY name`)
 	if err != nil {
 		return nil, err
 	}
@@ -266,7 +279,7 @@ func (db *DB) ListAgents() ([]Agent, error) {
 	for rows.Next() {
 		var a Agent
 		var last int64
-		if err := rows.Scan(&a.ID, &a.Name, &a.Hostname, &a.OS, &a.Arch, &a.Version, &last); err != nil {
+		if err := rows.Scan(&a.ID, &a.Name, &a.Hostname, &a.OS, &a.Arch, &a.Version, &a.RunUser, &a.LoginUser, &last); err != nil {
 			return nil, err
 		}
 		a.LastSeen = time.Unix(last, 0)
@@ -280,10 +293,16 @@ func (db *DB) TouchAgent(id string) error {
 	return err
 }
 
-// TouchAgentVersion updates last_seen and the reported version together.
+// TouchAgentInfo updates last_seen together with the reported version and OS user.
-func (db *DB) TouchAgentVersion(id, version string) error {
+func (db *DB) TouchAgentInfo(id, version, runUser string) error {
-	_, err := db.sql.Exec(`UPDATE agents SET last_seen = ?, version = ? WHERE id = ?`,
+	_, err := db.sql.Exec(`UPDATE agents SET last_seen = ?, version = ?, run_user = ? WHERE id = ?`,
-		time.Now().Unix(), version, id)
+		time.Now().Unix(), version, runUser, id)
+	return err
+}
+
+// SetAgentLoginUser sets the OS user terminals are opened as ("" = the agent's own).
+func (db *DB) SetAgentLoginUser(id, user string) error {
+	_, err := db.sql.Exec(`UPDATE agents SET login_user = ? WHERE id = ?`, user, id)
 	return err
 }
 

internal/server/handlers_agent.go

@@ -28,7 +28,7 @@ func (s *Server) handleEnroll(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "bad request", http.StatusBadRequest)
 		return
 	}
-	id, token, err := s.enroll(req.Name, req.Hostname, req.OS, req.Arch, req.Version)
+	id, token, err := s.enroll(req.Name, req.Hostname, req.OS, req.Arch, req.Version, req.User)
 	if err != nil {
 		http.Error(w, "internal error", http.StatusInternalServerError)
 		return
@@ -43,9 +43,12 @@ func (s *Server) handlePoll(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "unauthorized", http.StatusUnauthorized)
 		return
 	}
-	// The agent sends its version occasionally; record it when present.
+	// The agent sends its version and OS user occasionally; record them when
-	if v := r.Header.Get("X-Agent-Version"); v != "" && v != a.Version {
+	// present. Agents older than 0.0.2 send no user, so keep what we have.
-		_ = s.db.TouchAgentVersion(a.ID, v)
+	v := r.Header.Get("X-Agent-Version")
+	u := firstNonEmpty(r.Header.Get("X-Agent-User"), a.RunUser)
+	if v != "" && (v != a.Version || u != a.RunUser) {
+		_ = s.db.TouchAgentInfo(a.ID, v, u)
 	} else {
 		_ = s.db.TouchAgent(a.ID)
 	}
@@ -121,7 +124,11 @@ func (s *Server) handleTermOut(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if msg.Exit {
-		s.hub.CloseSession(sess.ID)
+		// End the stream now, but keep the session reachable for a moment so
+		// the panel can still collect the last output (e.g. why the shell
+		// failed to start).
+		sess.close()
+		time.AfterFunc(pollHold, func() { s.hub.CloseSession(sess.ID) })
 	}
 	w.WriteHeader(http.StatusNoContent)
 }

internal/server/handlers_panel.go

@@ -1,9 +1,13 @@
 package server
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"net/http"
+	"net/url"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -152,13 +156,135 @@ func (s *Server) handleAgentEdit(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 		return
 	}
-	s.render(w, "edit.html", map[string]any{
+	data := map[string]any{
 		"Agent":         a,
 		"CSRF":          csrfToken(r),
 		"ServerVersion": Version,
 		"Outdated":      a.Version != "" && a.Version != Version,
 		"Updated":       r.URL.Query().Get("updated") == "1",
+		"UserOK":        r.URL.Query().Get("uok"),
+		"UserErr":       r.URL.Query().Get("uerr"),
+	}
+	// The user list lives on the machine, so it is only known while it is online.
+	if a.Online() {
+		if users, err := s.agentUsers(id); err == nil {
+			data["Users"] = users
+		} else {
+			data["UsersErr"] = err.Error()
+		}
+	}
+	s.render(w, "edit.html", data)
+}
+
+// usersTaskTimeout bounds how long the edit page waits for the agent.
+const usersTaskTimeout = 8 * time.Second
+
+// agentUsers asks the agent who it runs as and which users it can log in as.
+func (s *Server) agentUsers(agentID string) (*proto.SysUsersResult, error) {
+	taskID, ch := s.hub.CreateTask(agentID, proto.TaskSysUsers, nil)
+	defer s.hub.DiscardTask(taskID)
+	select {
+	case res := <-ch:
+		if !res.OK {
+			// Agents older than 0.0.2 don't know this task.
+			return nil, errors.New("клиент не поддерживает выбор пользователя — обновите его")
+		}
+		var out proto.SysUsersResult
+		if err := json.Unmarshal(res.Data, &out); err != nil {
+			return nil, errors.New("некорректный ответ клиента")
+		}
+		return &out, nil
+	case <-time.After(usersTaskTimeout):
+		return nil, errors.New("таймаут ожидания клиента")
+	}
+}
+
+// editUserRedirect returns to the edit page with a result banner.
+func editUserRedirect(w http.ResponseWriter, r *http.Request, id, key, msg string) {
+	http.Redirect(w, r, "/agents/"+id+"/edit?"+key+"="+url.QueryEscape(msg), http.StatusSeeOther)
+}
+
+// handleAgentSetUser picks the OS user terminals on this machine run as.
+func (s *Server) handleAgentSetUser(w http.ResponseWriter, r *http.Request) {
+	if !checkCSRF(r) {
+		http.Error(w, "bad csrf", http.StatusForbidden)
+		return
+	}
+	id := r.PathValue("id")
+	a, err := s.db.GetAgent(id)
+	if err != nil || a == nil {
+		http.NotFound(w, r)
+		return
+	}
+	name := strings.TrimSpace(r.FormValue("user"))
+	if !a.Online() {
+		editUserRedirect(w, r, id, "uerr", "Машина офлайн — сменить пользователя нельзя.")
+		return
+	}
+	// Only accept a user the machine itself reports, so a typo (or an agent too
+	// old to honour the choice) can't silently leave the terminal as root.
+	users, err := s.agentUsers(id)
+	if err != nil {
+		editUserRedirect(w, r, id, "uerr", err.Error())
+		return
+	}
+	if !slices.Contains(users.Users, name) {
+		editUserRedirect(w, r, id, "uerr", "Пользователя "+name+" нет на машине.")
+		return
+	}
+	if name == users.Current {
+		name = "" // follow the agent's own user
+	}
+	if err := s.db.SetAgentLoginUser(id, name); err != nil {
+		editUserRedirect(w, r, id, "uerr", "Не удалось сохранить.")
+		return
+	}
+	if admin := s.currentAdmin(r); admin != nil {
+		s.db.Audit(admin.ID, id, "set_user:"+firstNonEmpty(name, users.Current))
+	}
+	editUserRedirect(w, r, id, "uok", "Терминал будет открываться от "+firstNonEmpty(name, users.Current)+".")
+}
+
+// handleAgentAddUser creates a new OS user on the machine and switches the
+// terminal to it.
+func (s *Server) handleAgentAddUser(w http.ResponseWriter, r *http.Request) {
+	if !checkCSRF(r) {
+		http.Error(w, "bad csrf", http.StatusForbidden)
+		return
+	}
+	id := r.PathValue("id")
+	a, err := s.db.GetAgent(id)
+	if err != nil || a == nil {
+		http.NotFound(w, r)
+		return
+	}
+	if !a.Online() {
+		editUserRedirect(w, r, id, "uerr", "Машина офлайн — создать пользователя нельзя.")
+		return
+	}
+	name := strings.TrimSpace(r.FormValue("name"))
+	args, _ := json.Marshal(proto.SysUserAddArgs{
+		Name:     name,
+		Password: r.FormValue("password"),
+		Sudo:     r.FormValue("sudo") == "1",
 	})
+	taskID, ch := s.hub.CreateTask(id, proto.TaskSysUserAdd, args)
+	defer s.hub.DiscardTask(taskID)
+	select {
+	case res := <-ch:
+		if !res.OK {
+			editUserRedirect(w, r, id, "uerr", "Не удалось создать пользователя: "+res.Error)
+			return
+		}
+	case <-time.After(30 * time.Second):
+		editUserRedirect(w, r, id, "uerr", "Таймаут ожидания клиента.")
+		return
+	}
+	_ = s.db.SetAgentLoginUser(id, name)
+	if admin := s.currentAdmin(r); admin != nil {
+		s.db.Audit(admin.ID, id, "create_user:"+name)
+	}
+	editUserRedirect(w, r, id, "uok", "Пользователь "+name+" создан и выбран для терминала.")
 }
 
 // handleAgentUpdate asks the agent to download the latest binary and restart.

internal/server/handlers_panel_term.go

@@ -21,9 +21,9 @@ func (s *Server) handlePanelOpen(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 		return
 	}
-	sess := s.hub.CreateSession(agentID)
+	sess := s.hub.CreateSession(agentID, agent.LoginUser)
 	if admin := s.currentAdmin(r); admin != nil {
-		s.db.Audit(admin.ID, agentID, "open_terminal")
+		s.db.Audit(admin.ID, agentID, "open_terminal:"+agent.TerminalUser())
 	}
 	writeJSON(w, map[string]string{"session_id": sess.ID})
 }

internal/server/hub.go

@@ -82,10 +82,11 @@ func (h *Hub) newSession(agentID string) *Session {
 	return s
 }
 
-// CreateSession registers a terminal session and queues it for the agent.
+// CreateSession registers a terminal session and queues it for the agent. user
-func (h *Hub) CreateSession(agentID string) *Session {
+// is the OS user to run the shell as ("" = the agent's own user).
+func (h *Hub) CreateSession(agentID, user string) *Session {
 	s := h.newSession(agentID)
-	h.enqueueJob(agentID, proto.ControlMessage{Type: proto.CtrlOpenTerminal, SessionID: s.ID})
+	h.enqueueJob(agentID, proto.ControlMessage{Type: proto.CtrlOpenTerminal, SessionID: s.ID, User: user})
 	return s
 }
 
@@ -245,7 +246,14 @@ func (s *Session) PollOut(timeout time.Duration) ([]proto.OutMessage, bool) {
 	case <-time.After(timeout):
 		return nil, true
 	case <-s.closed:
-		return nil, false
+		// Hand over output queued before the close (e.g. the reason a shell
+		// failed to start) instead of dropping it.
+		select {
+		case m := <-s.out:
+			batch = append(batch, m)
+		default:
+			return nil, false
+		}
 	}
 	for {
 		select {

internal/server/server.go

@@ -129,6 +129,8 @@ func (s *Server) Handler() http.Handler {
 	mux.Handle("GET /agents/{id}/edit", s.requireAdmin(s.handleAgentEdit))
 	mux.Handle("POST /agents/{id}/rename", s.requireAdmin(s.handleAgentRename))
 	mux.Handle("POST /agents/{id}/update", s.requireAdmin(s.handleAgentUpdate))
+	mux.Handle("POST /agents/{id}/user", s.requireAdmin(s.handleAgentSetUser))
+	mux.Handle("POST /agents/{id}/users/add", s.requireAdmin(s.handleAgentAddUser))
 	mux.Handle("POST /agents/{id}/delete", s.requireAdmin(s.handleAgentDelete))
 	mux.Handle("GET /settings", s.requireAdmin(s.handleSettings))
 	mux.Handle("POST /settings/host", s.requireAdmin(s.handleSetHost))

internal/server/web/static/app.css

@@ -38,6 +38,16 @@ input[type=text], input[type=password] {
   width: 100%; padding: 10px 12px; border-radius: 8px;
   border: 1px solid var(--border); background: #0c0f13; color: var(--text); font-size: 14px;
 }
+/* Sized and shaped like .btn.ghost so it lines up with the buttons next to it. */
+select {
+  -webkit-appearance: none; appearance: none; cursor: pointer;
+  min-width: 180px; padding: 10px 38px 10px 14px; border-radius: 8px;
+  border: 1px solid var(--border); color: var(--text);
+  font: inherit; font-size: 14px; font-weight: 500; line-height: 1.5;
+  background: #0c0f13 url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%238b95a5' stroke-width='3' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E") no-repeat right 14px center;
+}
+select:hover, select:focus { border-color: var(--accent); outline: none; }
+select:disabled, button:disabled { opacity: .5; cursor: not-allowed; }
 button, .btn {
   display: inline-block; cursor: pointer; border: 0; border-radius: 8px;
   padding: 10px 16px; font-size: 14px; font-weight: 500;

internal/server/web/templates/edit.html

@@ -4,7 +4,7 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>Изменить машину — LPRA</title>
-<link rel="stylesheet" href="/static/app.css">
+<link rel="stylesheet" href="/static/app.css?v={{.ServerVersion}}-2">
 </head>
 <body>
 <header class="topbar">
@@ -28,6 +28,46 @@
     </p>
   </div>
 
+  <div class="card">
+    <h2>Пользователь</h2>
+    {{if .UserOK}}<div class="err" style="background:#1d3a24;border-color:#2b6b3a;color:#b3ffcb">{{.UserOK}}</div>{{end}}
+    {{if .UserErr}}<div class="err">{{.UserErr}}</div>{{end}}
+    <p class="muted">
+      Клиент запущен от: <code>{{if .Users}}{{.Users.Current}}{{else if .Agent.RunUser}}{{.Agent.RunUser}}{{else}}неизвестно{{end}}</code>
+      · Терминал открывается от: <code>{{.Agent.TerminalUser}}</code>
+    </p>
+    {{if .Users}}
+    <form method="post" action="/agents/{{.Agent.ID}}/user" class="row">
+      <input type="hidden" name="csrf" value="{{.CSRF}}">
+      <select name="user" {{if not .Users.CanSwitch}}disabled{{end}}>
+        {{range .Users.Users}}<option value="{{.}}" {{if eq . $.Agent.TerminalUser}}selected{{end}}>{{.}}</option>{{end}}
+      </select>
+      <button type="submit" {{if not .Users.CanSwitch}}disabled{{end}}>Сохранить</button>
+      {{if .Users.CanSwitch}}<button type="button" class="btn ghost" onclick="document.getElementById('newuser').hidden = !document.getElementById('newuser').hidden">Создать нового</button>{{end}}
+    </form>
+    {{if .Users.CanSwitch}}
+    <form id="newuser" method="post" action="/agents/{{.Agent.ID}}/users/add" style="max-width:360px; margin-top:16px" hidden>
+      <input type="hidden" name="csrf" value="{{.CSRF}}">
+      <label for="nu-name">Имя нового пользователя</label>
+      <input type="text" id="nu-name" name="name" pattern="[a-z_][a-z0-9_\-]{0,31}" autocomplete="off" required>
+      <label for="nu-pass">Пароль</label>
+      <input type="password" id="nu-pass" name="password" autocomplete="new-password">
+      <label style="color:var(--text); font-size:14px">
+        <input type="checkbox" name="sudo" value="1"> Добавить в sudo
+      </label>
+      <p class="muted" style="font-size:13px">Без пароля вход по паролю (и sudo) для него работать не будет — только терминал из панели.</p>
+      <button type="submit">Создать пользователя</button>
+    </form>
+    {{else}}
+    <p class="muted" style="font-size:13px; margin-top:12px">Клиент запущен не от root, поэтому сменить или создать пользователя нельзя.</p>
+    {{end}}
+    {{else if .UsersErr}}
+    <p class="muted" style="font-size:13px">Список пользователей недоступен: {{.UsersErr}}.</p>
+    {{else}}
+    <p class="muted" style="font-size:13px">Машина офлайн — сменить пользователя можно, когда она на связи.</p>
+    {{end}}
+  </div>
+
   <div class="card">
     <h2>Версия клиента</h2>
     {{if .Updated}}<div class="err" style="background:#1d3a24;border-color:#2b6b3a;color:#b3ffcb">Команда обновления отправлена. Клиент скачает свежий бинарник и перезапустится.</div>{{end}}

internal/server/web/templates/terminal.html

@@ -13,7 +13,7 @@
 </head>
 <body>
 <header class="topbar">
-  <div class="brand">LPRA · Терминал — {{.Agent.Name}} <span class="muted">({{.Agent.Hostname}})</span></div>
+  <div class="brand">LPRA · Терминал — {{.Agent.Name}} <span class="muted">({{.Agent.TerminalUser}}@{{.Agent.Hostname}})</span></div>
   <nav>
     <a href="/">← Машины</a>
     <a href="/agents/{{.Agent.ID}}/files">Файлы</a>