windows changes

Signed-off-by: Harrison Affel <harrisonaffel@gmail.com>

pkg/agent/config/config.go

@@ -200,7 +200,16 @@ func ensureNodePassword(nodePasswordFile string) (string, error) {
 		return "", err
 	}
 	nodePassword := hex.EncodeToString(password)
-	return nodePassword, os.WriteFile(nodePasswordFile, []byte(nodePassword+"\n"), 0600)
+
+	if err = os.WriteFile(nodePasswordFile, []byte(nodePassword+"\n"), 0600); err != nil {
+		return nodePassword, err
+	}
+
+	if err = configureACL(nodePassword); err != nil {
+		return nodePassword, err
+	}
+
+	return nodePassword, nil
 }
 
 func upgradeOldNodePasswordPath(oldNodePasswordFile, newNodePasswordFile string) {

pkg/agent/config/config_linux.go

@@ -45,3 +45,9 @@ func applyContainerdQoSClassConfigFileIfPresent(envInfo *cmds.Agent, containerdC
 		}
 	}
 }
+
+// configureACL will configure an Access Control List for the specified file.
+// On Linux, this function is a no-op
+func configureACL(file string) error {
+	return nil
+}

pkg/agent/config/config_windows.go

@@ -6,8 +6,11 @@ package config
 import (
 	"path/filepath"
 
+	"github.com/k3s-io/k3s/pkg/agent/util/acl"
 	"github.com/k3s-io/k3s/pkg/cli/cmds"
 	"github.com/k3s-io/k3s/pkg/daemons/config"
+	"github.com/pkg/errors"
+	"golang.org/x/sys/windows"
 )
 
 func applyContainerdStateAndAddress(nodeConfig *config.Node) {
@@ -22,3 +25,19 @@ func applyCRIDockerdAddress(nodeConfig *config.Node) {
 func applyContainerdQoSClassConfigFileIfPresent(envInfo *cmds.Agent, containerdConfig *config.Containerd) {
 	// QoS-class resource management not supported on windows.
 }
+
+// configureACL will configure an Access Control List for the specified file,
+// ensuring that only the LocalSystem and Administrators Group have access to the file contents
+func configureACL(file string) error {
+	// by default Apply will use the current user (LocalSystem in the case of a Windows service)
+	// as the owner and current user group as the allowed group
+	// additionally, we define a DACL to permit access to the file to the local system and all administrators
+	if err := acl.Apply(file, nil, nil, []windows.EXPLICIT_ACCESS{
+		acl.GrantSid(windows.GENERIC_ALL, acl.LocalSystemSID()),
+		acl.GrantSid(windows.GENERIC_ALL, acl.BuiltinAdministratorsSID()),
+	}...); err != nil {
+		return errors.Wrapf(err, "failed to configure Access Control List For %s", file)
+	}
+
+	return nil
+}

pkg/agent/util/acl/acl_windows.go

@@ -0,0 +1,166 @@
+//go:build windows
+// +build windows
+
+package acl
+
+import (
+	"fmt"
+	"golang.org/x/sys/windows"
+	"unsafe"
+)
+
+// TODO: Remove in favor of the rancher/permissions repository once that is setup
+
+func BuiltinAdministratorsSID() *windows.SID {
+	return mustGetSid(windows.WinBuiltinAdministratorsSid)
+}
+
+func LocalSystemSID() *windows.SID {
+	return mustGetSid(windows.WinLocalSystemSid)
+}
+
+func mustGetSid(sidType windows.WELL_KNOWN_SID_TYPE) *windows.SID {
+	sid, err := windows.CreateWellKnownSid(sidType)
+	if err != nil {
+		panic(err)
+	}
+	return sid
+}
+
+// GrantSid creates an EXPLICIT_ACCESS instance granting permissions to the provided SID.
+func GrantSid(accessPermissions windows.ACCESS_MASK, sid *windows.SID) windows.EXPLICIT_ACCESS {
+	return windows.EXPLICIT_ACCESS{
+		AccessPermissions: accessPermissions,
+		AccessMode:        windows.GRANT_ACCESS,
+		Inheritance:       windows.SUB_CONTAINERS_AND_OBJECTS_INHERIT,
+		Trustee: windows.TRUSTEE{
+			TrusteeForm:  windows.TRUSTEE_IS_SID,
+			TrusteeValue: windows.TrusteeValueFromSID(sid),
+		},
+	}
+}
+
+// Apply performs both Chmod and Chown at the same time, where the filemode's owner and group will correspond to
+// the provided owner and group (or the current owner and group, if they are set to nil)
+func Apply(path string, owner *windows.SID, group *windows.SID, access ...windows.EXPLICIT_ACCESS) error {
+	if path == "" {
+		return fmt.Errorf("path cannot be empty")
+	}
+	return apply(path, owner, group, access...)
+}
+
+// apply performs a Chmod (if owner and group are provided) and sets a custom ACL based on the provided EXPLICIT_ACCESS rules
+// To create EXPLICIT_ACCESS rules, see the helper functions in pkg/access
+func apply(path string, owner *windows.SID, group *windows.SID, access ...windows.EXPLICIT_ACCESS) error {
+	// assemble arguments
+	args := securityArgs{
+		path:   path,
+		owner:  owner,
+		group:  group,
+		access: access,
+	}
+
+	securityInfo := args.ToSecurityInfo()
+	if securityInfo == 0 {
+		// nothing to change
+		return nil
+	}
+	dacl, err := args.ToDACL()
+	if err != nil {
+		return err
+	}
+	return windows.SetNamedSecurityInfo(
+		path,
+		windows.SE_FILE_OBJECT,
+		securityInfo,
+		owner,
+		group,
+		dacl,
+		nil,
+	)
+}
+
+type securityArgs struct {
+	path string
+
+	owner *windows.SID
+	group *windows.SID
+
+	access []windows.EXPLICIT_ACCESS
+}
+
+func (a *securityArgs) ToSecurityInfo() windows.SECURITY_INFORMATION {
+	var securityInfo windows.SECURITY_INFORMATION
+
+	if a.owner != nil {
+		// override owner
+		securityInfo |= windows.OWNER_SECURITY_INFORMATION
+	}
+
+	if a.group != nil {
+		// override group
+		securityInfo |= windows.GROUP_SECURITY_INFORMATION
+	}
+
+	if len(a.access) != 0 {
+		// override DACL
+		securityInfo |= windows.DACL_SECURITY_INFORMATION
+		securityInfo |= windows.PROTECTED_DACL_SECURITY_INFORMATION
+	}
+
+	return securityInfo
+}
+
+func (a *securityArgs) ToSecurityAttributes() (*windows.SecurityAttributes, error) {
+	// define empty security descriptor
+	sd, err := windows.NewSecurityDescriptor()
+	if err != nil {
+		return nil, err
+	}
+	err = sd.SetOwner(a.owner, false)
+	if err != nil {
+		return nil, err
+	}
+	err = sd.SetGroup(a.group, false)
+	if err != nil {
+		return nil, err
+	}
+
+	// define security attributes using descriptor
+	var sa windows.SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.SecurityDescriptor = sd
+
+	if len(a.access) == 0 {
+		// security attribute should simply inherit parent rules
+		sa.InheritHandle = 1
+		return &sa, nil
+	}
+
+	// apply provided access rules to the DACL
+	dacl, err := a.ToDACL()
+	if err != nil {
+		return nil, err
+	}
+	err = sd.SetDACL(dacl, true, false)
+	if err != nil {
+		return nil, err
+	}
+
+	// set the protected DACL flag to prevent the DACL of the security descriptor from being modified by inheritable ACEs
+	// (i.e. prevent parent folders from modifying this ACL)
+	err = sd.SetControl(windows.SE_DACL_PROTECTED, windows.SE_DACL_PROTECTED)
+	if err != nil {
+		return nil, err
+	}
+
+	return &sa, nil
+}
+
+func (a *securityArgs) ToDACL() (*windows.ACL, error) {
+	if len(a.access) == 0 {
+		// No rules were specified
+		return nil, nil
+	}
+	return windows.ACLFromEntries(a.access, nil)
+}