feat: discover active Windows sessions

docs/implementation-plan.v1.md

@@ -805,6 +805,14 @@ Guest Control only with `--passwordfile`. The current VirtualBox `7.2.16`
 Guest Control build supports `--wait-stdout` and `--wait-stderr`, but not
 `--wait-exit`; adapters must not pass that unsupported flag.
 
+For a guest `cmd.exe` command payload, this Guest Control build requires
+`--unquoted-args` so the controller preserves Windows backslashes and the
+single `/c` command payload. Treat each Guest Control process as a bounded,
+owned resource: record its guest session/PID, close it after completion, and
+use `closeprocess` before reset if an output wait does not complete. Do not use
+this compatibility rule to assemble untrusted command text; it is solely the
+adapter transport for prevalidated test commands and exact executable paths.
+
 Use a local, non-secret environment description when operating the lane. The
 host alias must resolve through the operator's SSH config; another controller
 may substitute an equivalent target, but must record the resulting host/VM

internal/client/supervisor/windows/discovery_windows.go

@@ -0,0 +1,100 @@
+//go:build windows
+
+package windows
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+const (
+	wtsCurrentServerHandle windows.Handle = 0
+	invalidSessionID                      = ^uint32(0)
+)
+
+// DiscoverActiveSessions translates only verified active WTS user tokens into
+// selector DTOs. It is intended for the LocalSystem service: WTSQueryUserToken
+// requires LocalSystem and SeTcbPrivilege. A token-query failure leaves that
+// WTS session unusable rather than guessing an identity.
+func DiscoverActiveSessions() ([]SessionCandidate, error) {
+	var sessions *windows.WTS_SESSION_INFO
+	var count uint32
+	if err := windows.WTSEnumerateSessions(wtsCurrentServerHandle, 0, 1, &sessions, &count); err != nil {
+		return nil, fmt.Errorf("enumerate WTS sessions: %w", err)
+	}
+	if sessions == nil {
+		return nil, nil
+	}
+	defer windows.WTSFreeMemory(uintptr(unsafe.Pointer(sessions)))
+
+	console := windows.WTSGetActiveConsoleSessionId()
+	result := make([]SessionCandidate, 0, count)
+	for _, session := range unsafe.Slice(sessions, count) {
+		if session.State != windows.WTSActive {
+			continue
+		}
+		candidate, err := candidateFromSession(session.SessionID, console)
+		if err == nil {
+			result = append(result, candidate)
+		}
+	}
+	return result, nil
+}
+
+func candidateFromSession(sessionID, console uint32) (SessionCandidate, error) {
+	var token windows.Token
+	if err := windows.WTSQueryUserToken(sessionID, &token); err != nil {
+		return SessionCandidate{}, fmt.Errorf("query user token for session %d: %w", sessionID, err)
+	}
+	defer token.Close()
+
+	user, err := token.GetTokenUser()
+	if err != nil || user.User.Sid == nil {
+		return SessionCandidate{}, fmt.Errorf("query token user for session %d: %w", sessionID, err)
+	}
+	logonSID, err := tokenLogonSID(token)
+	if err != nil {
+		return SessionCandidate{}, fmt.Errorf("query token logon SID for session %d: %w", sessionID, err)
+	}
+	facts := tokenFacts(token)
+	if !facts.Usable {
+		return SessionCandidate{}, fmt.Errorf("token for session %d is not usable", sessionID)
+	}
+	return SessionCandidate{
+		SessionID: sessionID, Console: console != invalidSessionID && sessionID == console,
+		UserSID: user.User.Sid.String(), LogonSID: logonSID, Token: facts,
+	}, nil
+}
+
+func tokenFacts(token windows.Token) TokenFacts {
+	facts := TokenFacts{Usable: true}
+	if token.IsElevated() {
+		facts.FullAdministrator = true
+		return facts
+	}
+	// WTSQueryUserToken normally returns the user's standard/filtered primary
+	// token. The launch adapter re-verifies integrity and can create a
+	// restricted medium token if a legacy full-only token is encountered.
+	facts.StandardOrFiltered = true
+	linked, err := token.GetLinkedToken()
+	if err == nil {
+		facts.LinkedFullAvailable = linked.IsElevated()
+		_ = linked.Close()
+	}
+	return facts
+}
+
+func tokenLogonSID(token windows.Token) (string, error) {
+	groups, err := token.GetTokenGroups()
+	if err != nil {
+		return "", err
+	}
+	for _, group := range groups.AllGroups() {
+		if group.Sid != nil && group.Attributes&windows.SE_GROUP_LOGON_ID == windows.SE_GROUP_LOGON_ID {
+			return group.Sid.String(), nil
+		}
+	}
+	return "", fmt.Errorf("token has no logon SID")
+}