Add nasctl: Go NAS control plane with React frontend

internal/system/exec.go

@@ -0,0 +1,138 @@
+package system
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+var (
+	usernamePattern   = regexp.MustCompile(`^[a-z_][a-z0-9_-]*[$]?$`)
+	shareNamePattern  = regexp.MustCompile(`^[a-zA-Z0-9_-]+$`)
+	nfsOptionPattern  = regexp.MustCompile(`^[a-z_]+$`)
+	nfsClientPattern  = regexp.MustCompile(`^[a-zA-Z0-9_.:/\-\*]+$`)
+	allowedNFSOptions = map[string]bool{
+		"rw": true, "ro": true, "sync": true, "async": true,
+		"root_squash": true, "no_root_squash": true, "all_squash": true,
+		"no_all_squash": true, "subtree_check": true, "no_subtree_check": true,
+		"secure": true, "insecure": true, "wdelay": true, "no_wdelay": true,
+		"hide": true, "nohide": true, "crossmnt": true, "fsid": true,
+	}
+)
+
+// Run executes a command with explicit arguments (never via shell).
+func Run(ctx context.Context, name string, args ...string) (stdout, stderr string, err error) {
+	cmd := exec.CommandContext(ctx, name, args...)
+	var outBuf, errBuf strings.Builder
+	cmd.Stdout = &outBuf
+	cmd.Stderr = &errBuf
+	err = cmd.Run()
+	return outBuf.String(), errBuf.String(), err
+}
+
+// RunWithInput executes a command feeding stdin from the provided string.
+// Used for secrets (e.g. passwords) so they never appear in the argument list.
+func RunWithInput(ctx context.Context, stdin, name string, args ...string) (stdout, stderr string, err error) {
+	cmd := exec.CommandContext(ctx, name, args...)
+	cmd.Stdin = strings.NewReader(stdin)
+	var outBuf, errBuf strings.Builder
+	cmd.Stdout = &outBuf
+	cmd.Stderr = &errBuf
+	err = cmd.Run()
+	return outBuf.String(), errBuf.String(), err
+}
+
+// UserExists reports whether a system user is present (via `id -u`).
+func UserExists(ctx context.Context, username string) bool {
+	_, _, err := Run(ctx, "id", "-u", username)
+	return err == nil
+}
+
+// ValidateUsername checks Linux username constraints.
+func ValidateUsername(username string) error {
+	if username == "" || len(username) > 32 {
+		return fmt.Errorf("invalid username length")
+	}
+	if !usernamePattern.MatchString(username) {
+		return fmt.Errorf("invalid username: %q", username)
+	}
+	return nil
+}
+
+// ValidatePath ensures path is absolute and does not contain traversal.
+func ValidatePath(path string) error {
+	if path == "" {
+		return fmt.Errorf("path is required")
+	}
+	if !filepath.IsAbs(path) {
+		return fmt.Errorf("path must be absolute: %q", path)
+	}
+	clean := filepath.Clean(path)
+	if strings.Contains(clean, "..") {
+		return fmt.Errorf("path must not contain .. segments: %q", path)
+	}
+	return nil
+}
+
+// ValidateShareName checks Samba share name constraints.
+func ValidateShareName(name string) error {
+	if name == "" || len(name) > 80 {
+		return fmt.Errorf("invalid share name length")
+	}
+	if !shareNamePattern.MatchString(name) {
+		return fmt.Errorf("invalid share name: %q", name)
+	}
+	return nil
+}
+
+// ValidatePathAllowed validates a path and, if allowedRoots is non-empty,
+// ensures the path is contained within one of the configured roots.
+func ValidatePathAllowed(path string, allowedRoots []string) error {
+	if err := ValidatePath(path); err != nil {
+		return err
+	}
+	if len(allowedRoots) == 0 {
+		return nil
+	}
+	clean := filepath.Clean(path)
+	for _, root := range allowedRoots {
+		root = filepath.Clean(root)
+		if clean == root || strings.HasPrefix(clean, root+string(filepath.Separator)) {
+			return nil
+		}
+	}
+	return fmt.Errorf("path %q is not within an allowed directory", path)
+}
+
+// ValidateNFSClient checks an NFS client/network specifier.
+func ValidateNFSClient(client string) error {
+	if client == "" || len(client) > 255 {
+		return fmt.Errorf("invalid nfs client length")
+	}
+	if !nfsClientPattern.MatchString(client) {
+		return fmt.Errorf("invalid nfs client: %q", client)
+	}
+	return nil
+}
+
+// ValidateNFSOptions checks a comma-separated list of export options against
+// a whitelist, rejecting anything that could break the exports file.
+func ValidateNFSOptions(options string) error {
+	for _, opt := range strings.Split(options, ",") {
+		opt = strings.TrimSpace(opt)
+		if opt == "" {
+			continue
+		}
+		key := opt
+		if idx := strings.IndexByte(opt, '='); idx >= 0 {
+			key = opt[:idx]
+		}
+		if !nfsOptionPattern.MatchString(key) || !allowedNFSOptions[key] {
+			return fmt.Errorf("invalid nfs option: %q", opt)
+		}
+	}
+	return nil
+}