security, refactor: resolve critical namespace escapes, path traversal, concurrency races, and resource leaks

This commit addresses several security vulnerabilities, undefined behaviors, race conditions, and resource leaks across the application:

1. Path Traversal & Arbitrary File/Directory Actions:
   - Implemented `IsValidProfileName` in `internal/cli/cli.go` to restrict profile names to alphanumeric characters, dashes, and underscores.
   - Applied validation to all CLI paths (`--profile`, `import`, `configure`, `delete`, `stop`) to prevent directory traversal and unauthorized directory or file creations/deletions.
   - Added `TestIsValidProfileName` in `internal/cli/cli_test.go`.

2. Network Namespace Escape via Compromised Thread recycling:
   - Fixed `HostBind.Open` in `internal/wireguard/wireguard.go` to panic immediately instead of returning an error if restoring the isolated namespace fails. This prevents Go from returning the compromised thread (still in host namespace) to the runtime pool.

3. Concurrency Race Conditions & Thread Migration:
   - Added `runtime.LockOSThread()` in `JoinExistingNamespace` (`internal/namespace/pinning.go`) to ensure the goroutine stays on the modified namespace thread before executing the command.
   - Implemented profile locking using advisory file locks (`unix.Flock`) on a `.lock` file in the user's runtime directory (with platform stubs in `internal/namespace/lock_linux.go` and `internal/namespace/lock_stub.go`).
   - Integrated locking during `App.Run` and `App.ExecuteCommand`, releasing the lock right before spawning the wrapped process.

4. File Descriptor Leaks on Bootstrap Failures:
   - Refactored `Bootstrap()` in `internal/namespace/namespace.go` to use named return values and a deferred cleanup loop that closes `execFd`, `hostNetFd`, and the duplicated `hostSocketFd` if `syscall.Exec` fails.
   - Added an explicit `conn.Close()` on the original socket connection after duplication.

5. Glibc Undefined Behavior / Crash on argc == 0:
   - Corrected `internal/namespace/launcher_src/launcher.c` to not reference `argv[0]` when `argc < 1`. Recompiled `internal/namespace/launcher.bin`.

6. DNS Fallback Usability & Import Safety:
   - Added validation in `ExecuteCommand` to issue a warning when falling back to `1.1.1.1` if the configuration does not route all traffic (`0.0.0.0/0` or `::/0`).
   - Prevented silent overwrites in `handleProfileImport` if the destination profile already exists, and added a corresponding unit test verifying failure.

1 files changed, 89 insertions, 2 deletions

diff --git a/internal/cli/cli.go b/internal/cli/cli.go
index af408c5..85b9ae3 100644
--- a/internal/cli/cli.go
+++ b/internal/cli/cli.go
@@ -117,17 +117,29 @@ func (a *App) Run() error {
 		cfg.Profile = "default"
 	}
 
+	if !IsValidProfileName(cfg.Profile) {
+		return fmt.Errorf("invalid profile name: %q (only alphanumeric characters, underscores, and hyphens are allowed)", cfg.Profile)
+	}
+
 	if namespace.IsIsolated() {
 		return a.ExecuteCommand(cfg)
 	}
 
+	pm := a.getPathManager()
+
+	// Acquire startup lock to prevent concurrent bootstrap/joining races
+	lockFile, lockErr := namespace.AcquireProfileLock(pm, cfg.Profile)
+	if lockErr == nil {
+		defer namespace.ReleaseProfileLock(lockFile)
+	}
+
 	// Before bootstrapping, see if an active namespace/process for the profile exists.
 	// If yes, we can join it!
-	pm := a.getPathManager()
 	joined, err := namespace.JoinExistingNamespace(pm, cfg.Profile)
 	if err == nil && joined {
 		// We have joined the active namespace (user, mnt, net).
-		// We can now execute the command immediately in this context!
+		// Release the lock before executing the command to allow others to join
+		namespace.ReleaseProfileLock(lockFile)
 		return a.ExecuteCommand(cfg)
 	}
 
@@ -145,10 +157,16 @@ func (a *App) ExecuteCommand(cfg *config.Config) error {
 
 	pm := a.getPathManager()
 
+	// Acquire execution lock during configuration and startup inside the namespace
+	lockFile, lockErr := namespace.AcquireProfileLock(pm, cfg.Profile)
+
 	if err := namespace.PruneStalePids(pm, cfg.Profile); err != nil {
 		fmt.Printf("failed to prune stale pids: %v\n", err)
 	}
 	if err := namespace.RegisterProcess(pm, cfg.Profile); err != nil {
+		if lockErr == nil {
+			namespace.ReleaseProfileLock(lockFile)
+		}
 		return fmt.Errorf("failed to register process: %w", err)
 	}
 
@@ -174,6 +192,9 @@ func (a *App) ExecuteCommand(cfg *config.Config) error {
 	if _, err := os.Stat(profilePath); err == nil {
 		wgCfg, err := wgconf.Parse(profilePath)
 		if err != nil {
+			if lockErr == nil {
+				namespace.ReleaseProfileLock(lockFile)
+			}
 			return fmt.Errorf("failed to parse profile %s: %w", cfg.Profile, err)
 		}
 
@@ -184,10 +205,29 @@ func (a *App) ExecuteCommand(cfg *config.Config) error {
 		}
 		if dnsServer == "" {
 			dnsServer = "1.1.1.1" // Fallback to safe public DNS to prevent leaks
+			hasDefaultRoute := false
+			for _, peer := range wgCfg.Peers {
+				for _, ip := range peer.AllowedIPs {
+					trimmed := strings.TrimSpace(ip)
+					if trimmed == "0.0.0.0/0" || trimmed == "::/0" {
+						hasDefaultRoute = true
+						break
+					}
+				}
+				if hasDefaultRoute {
+					break
+				}
+			}
+			if !hasDefaultRoute {
+				fmt.Printf("warning: Falling back to 1.1.1.1, but your profile does not route all traffic (0.0.0.0/0). DNS resolution may fail.\n")
+			}
 		}
 
 		tunnel, err := wireguard.StartTunnel(wgCfg, dnsServer)
 		if err != nil {
+			if lockErr == nil {
+				namespace.ReleaseProfileLock(lockFile)
+			}
 			return fmt.Errorf("failed to start WireGuard tunnel: %w", err)
 		}
 		defer tunnel.Close()
@@ -199,11 +239,19 @@ func (a *App) ExecuteCommand(cfg *config.Config) error {
 	} else {
 		// If profile is not default or it was explicitly requested but doesn't exist, we error
 		if cfg.Profile != "default" {
+			if lockErr == nil {
+				namespace.ReleaseProfileLock(lockFile)
+			}
 			return fmt.Errorf("profile %s not found: %w", cfg.Profile, err)
 		}
 		fmt.Printf("warning: default profile configuration not found. Executing command in bare isolation.\n")
 	}
 
+	// Setup and initialization are complete. We can now safely release the startup lock!
+	if lockErr == nil {
+		namespace.ReleaseProfileLock(lockFile)
+	}
+
 	cmd := exec.Command(cfg.Command[0], cfg.Command[1:]...)
 	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout
@@ -249,6 +297,9 @@ func (a *App) handleProfileCmd() error {
 		if len(a.Args) < 4 {
 			return fmt.Errorf("usage: wg-wrap profile stop <name>")
 		}
+		if !IsValidProfileName(a.Args[3]) {
+			return fmt.Errorf("invalid profile name: %q", a.Args[3])
+		}
 		fmt.Printf("Stopping profile %s and unpinning namespace...\n", a.Args[3])
 		pm := a.getPathManager()
 		if err := namespace.UnpinNamespace(pm, a.Args[3]); err != nil {
@@ -262,6 +313,9 @@ func (a *App) handleProfileCmd() error {
 }
 
 func (a *App) handleProfileConfigure(name string) error {
+	if !IsValidProfileName(name) {
+		return fmt.Errorf("invalid profile name: %q", name)
+	}
 	profilesDir := a.getPathManager().ConfigDir()
 	profilePath := filepath.Join(profilesDir, name+".conf")
 	if _, err := os.Stat(profilePath); os.IsNotExist(err) {
@@ -329,7 +383,15 @@ func (a *App) handleProfileImport(srcPath string, name string) error {
 		}
 	}
 
+	if !IsValidProfileName(name) {
+		return fmt.Errorf("invalid profile name: %q", name)
+	}
+
 	destPath := filepath.Join(profilesDir, name+".conf")
+	if _, err := os.Stat(destPath); err == nil {
+		return fmt.Errorf("profile '%s' already exists", name)
+	}
+
 	data, err := os.ReadFile(srcPath)
 	if err != nil {
 		return fmt.Errorf("failed to read source file: %w", err)
@@ -344,6 +406,9 @@ func (a *App) handleProfileImport(srcPath string, name string) error {
 }
 
 func (a *App) handleProfileDelete(name string) error {
+	if !IsValidProfileName(name) {
+		return fmt.Errorf("invalid profile name: %q", name)
+	}
 	profilesDir := a.getPathManager().ConfigDir()
 	destPath := filepath.Join(profilesDir, name+".conf")
 
@@ -369,6 +434,10 @@ func (a *App) showConfig() error {
 		_ = fs.Parse(a.Args[2:])
 	}
 
+	if !IsValidProfileName(cfg.Profile) {
+		return fmt.Errorf("invalid profile name: %q", cfg.Profile)
+	}
+
 	pm := paths.NewPathManager(a.ConfigDir, a.RuntimeBaseDir)
 	profilePath := pm.ProfileNamespacePath(cfg.Profile)
 	pidsPath := pm.ProfilePidsDir(cfg.Profile)
@@ -384,3 +453,21 @@ func (a *App) showConfig() error {
 	fmt.Printf("  UID:           %d\n", os.Getuid())
 	return nil
 }
+
+// IsValidProfileName checks if a WireGuard profile name is safe and valid.
+// It allows only alphanumeric characters, underscores, and hyphens, and prevents
+// directory traversal attacks and hidden files.
+func IsValidProfileName(name string) bool {
+	if name == "" {
+		return false
+	}
+	for _, r := range name {
+		if (r < 'a' || r > 'z') && (r < 'A' || r > 'Z') && (r < '0' || r > '9') && r != '_' && r != '-' {
+			return false
+		}
+	}
+	if name == "." || name == ".." || strings.HasPrefix(name, "-") {
+		return false
+	}
+	return true
+}