[8.17](backport #5988) Add support for pre existing Active Directory user

changelog/fragments/1731314919-Added-support-for-custom-Active-Directory-user-for-unprivileged-mode.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: feature
+
+# Change summary; a 80ish characters long description of the change.
+summary: Added support for pre-existing Active Directory user for unprivileged mode
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+description: User can specify custom pre-existing user for running unprivileged mode. This user will be given permissions to log on as a service.
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component:
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: https://github.com/owner/repo/1234
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+issue: https://github.com/elastic/elastic-agent/issues/4585

internal/pkg/agent/cmd/install.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"runtime"
 
 	"github.com/spf13/cobra"
 
@@ -28,6 +29,10 @@ const (
 	flagInstallDevelopment            = "develop"
 	flagInstallNamespace              = "namespace"
 	flagInstallRunUninstallFromBinary = "run-uninstall-from-binary"
+
+	flagInstallCustomUser  = "user"
+	flagInstallCustomGroup = "group"
+	flagInstallCustomPass  = "password"
 )
 
 func newInstallCommandWithArgs(_ []string, streams *cli.IOStreams) *cobra.Command {
@@ -61,6 +66,13 @@ would like the Agent to operate.
 	cmd.Flags().Bool(flagInstallDevelopment, false, "Install into a standardized development namespace, may enable development specific options. Allows multiple Elastic Agents to be installed at once. (experimental)")
 	_ = cmd.Flags().MarkHidden(flagInstallDevelopment) // For internal use only.
 
+	// Active directory user specification
+	cmd.Flags().String(flagInstallCustomUser, "", "Custom user used to run Elastic Agent")
+	cmd.Flags().String(flagInstallCustomGroup, "", "Custom group used to access Elastic Agent files")
+	if runtime.GOOS == "windows" {
+		cmd.Flags().String(flagInstallCustomPass, "", "Password for user used to run Elastic Agent")
+	}
+
 	addEnrollFlags(cmd)
 
 	return cmd
@@ -249,7 +261,14 @@ func installCmd(streams *cli.IOStreams, cmd *cobra.Command) error {
 		progBar.Describe("Successfully uninstalled Elastic Agent")
 	}
 	if status != install.PackageInstall {
-		ownership, err = install.Install(cfgFile, topPath, unprivileged, log, progBar, streams)
+		customUser, _ := cmd.Flags().GetString(flagInstallCustomUser)
+		customGroup, _ := cmd.Flags().GetString(flagInstallCustomGroup)
+		customPass := ""
+		if runtime.GOOS == "windows" {
+			customPass, _ = cmd.Flags().GetString(flagInstallCustomPass)
+		}
+
+		ownership, err = install.Install(cfgFile, topPath, unprivileged, log, progBar, streams, customUser, customGroup, customPass)
 		if err != nil {
 			return fmt.Errorf("error installing package: %w", err)
 		}

internal/pkg/agent/cmd/privileged.go

@@ -69,7 +69,7 @@ func privilegedCmd(streams *cli.IOStreams, cmd *cobra.Command) (err error) {
 	}
 
 	pt := install.CreateAndStartNewSpinner(streams.Out, "Converting Elastic Agent to privileged...")
-	err = install.SwitchExecutingMode(topPath, pt, "", "")
+	err = install.SwitchExecutingMode(topPath, pt, "", "", "")
 	if err != nil {
 		// error already adds context
 		return err

internal/pkg/agent/cmd/unprivileged.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"runtime"
 
 	"github.com/spf13/cobra"
 
@@ -44,6 +45,13 @@ unprivileged it will still perform all the same work, including stopping and sta
 	cmd.Flags().BoolP("force", "f", false, "Do not prompt for confirmation")
 	cmd.Flags().DurationP("daemon-timeout", "", 0, "Timeout waiting for Elastic Agent daemon restart after the change is applied (-1 = no wait)")
 
+	// Custom  user specification
+	cmd.Flags().String(flagInstallCustomUser, "", "Custom user used to run Elastic Agent")
+	cmd.Flags().String(flagInstallCustomGroup, "", "Custom group used to access Elastic Agent files")
+	if runtime.GOOS == "windows" {
+		cmd.Flags().String(flagInstallCustomPass, "", "Password for user used to run Elastic Agent")
+	}
+
 	return cmd
 }
 
@@ -56,6 +64,13 @@ func unprivilegedCmd(streams *cli.IOStreams, cmd *cobra.Command) (err error) {
 		return fmt.Errorf("unable to perform unprivileged command, not executed with %s permissions", utils.PermissionUser)
 	}
 
+	customUser, _ := cmd.Flags().GetString(flagInstallCustomUser)
+	customGroup, _ := cmd.Flags().GetString(flagInstallCustomGroup)
+	customPass := ""
+	if runtime.GOOS == "windows" {
+		customPass, _ = cmd.Flags().GetString(flagInstallCustomPass)
+	}
+
 	// cannot switch to unprivileged when service components have issues
 	err = ensureNoServiceComponentIssues()
 	if err != nil {
@@ -77,7 +92,10 @@ func unprivilegedCmd(streams *cli.IOStreams, cmd *cobra.Command) (err error) {
 	}
 
 	pt := install.CreateAndStartNewSpinner(streams.Out, "Converting Elastic Agent to unprivileged...")
-	err = install.SwitchExecutingMode(topPath, pt, install.ElasticUsername, install.ElasticGroupName)
+
+	username, password := install.UnprivilegedUser(customUser, customPass)
+	groupName := install.UnprivilegedGroup(customGroup)
+	err = install.SwitchExecutingMode(topPath, pt, username, groupName, password)
 	if err != nil {
 		// error already adds context
 		return err

internal/pkg/agent/install/install.go

@@ -40,7 +40,7 @@ const (
 )
 
 // Install installs Elastic Agent persistently on the system including creating and starting its service.
-func Install(cfgFile, topPath string, unprivileged bool, log *logp.Logger, pt *progressbar.ProgressBar, streams *cli.IOStreams) (utils.FileOwner, error) {
+func Install(cfgFile, topPath string, unprivileged bool, log *logp.Logger, pt *progressbar.ProgressBar, streams *cli.IOStreams, customUser, customGroup, userPassword string) (utils.FileOwner, error) {
 	dir, err := findDirectory()
 	if err != nil {
 		return utils.FileOwner{}, errors.New(err, "failed to discover the source directory for installation", errors.TypeFilesystem)
@@ -49,13 +49,15 @@ func Install(cfgFile, topPath string, unprivileged bool, log *logp.Logger, pt *p
 	var ownership utils.FileOwner
 	username := ""
 	groupName := ""
+	password := ""
 	if unprivileged {
-		username = ElasticUsername
-		groupName = ElasticGroupName
-		ownership, err = EnsureUserAndGroup(username, groupName, pt)
+		username, password = UnprivilegedUser(customUser, userPassword)
+		groupName = UnprivilegedGroup(customGroup)
+		ownership, err = EnsureUserAndGroup(username, groupName, pt, username == ElasticUsername && password == "") // force create only elastic user
 		if err != nil {
 			// error context already added by EnsureUserAndGroup
 			return utils.FileOwner{}, err
+
 		}
 	}
 
@@ -147,7 +149,7 @@ func Install(cfgFile, topPath string, unprivileged bool, log *logp.Logger, pt *p
 
 	// install service
 	pt.Describe("Installing service")
-	err = InstallService(topPath, ownership, username, groupName)
+	err = InstallService(topPath, ownership, username, groupName, password)
 	if err != nil {
 		pt.Describe("Failed to install service")
 		// error context already added by InstallService
@@ -371,11 +373,12 @@ func StatusService(topPath string) (service.Status, error) {
 }
 
 // InstallService installs the service.
-func InstallService(topPath string, ownership utils.FileOwner, username string, groupName string) error {
-	opts, err := withServiceOptions(username, groupName)
+func InstallService(topPath string, ownership utils.FileOwner, username string, groupName string, password string) error {
+	opts, err := withServiceOptions(username, groupName, password)
 	if err != nil {
 		return fmt.Errorf("error getting service installation options: %w", err)
 	}
+
 	svc, err := newService(topPath, opts...)
 	if err != nil {
 		return fmt.Errorf("error creating new service handler for install: %w", err)
@@ -482,3 +485,19 @@ func CreateInstallMarker(topPath string, ownership utils.FileOwner) error {
 	_ = handle.Close()
 	return fixInstallMarkerPermissions(markerFilePath, ownership)
 }
+
+func UnprivilegedUser(username, password string) (string, string) {
+	if username != "" {
+		return username, password
+	}
+
+	return ElasticUsername, password
+}
+
+func UnprivilegedGroup(groupName string) string {
+	if groupName != "" {
+		return groupName
+	}
+
+	return ElasticGroupName
+}

internal/pkg/agent/install/install_test.go

@@ -5,6 +5,7 @@
 package install
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"testing"
@@ -65,6 +66,50 @@ func TestHasAllSSDs(t *testing.T) {
 	}
 }
 
+func TestUnprivilegedUser(t *testing.T) {
+	testCases := []struct {
+		username         string
+		password         string
+		expectedUsername string
+		expectedPassword string
+	}{
+		{"", "", ElasticUsername, ""},
+		{"", "pass", ElasticUsername, "pass"},
+		{"user", "", "user", ""},
+		{"user", "pass", "user", "pass"},
+	}
+	for i, tc := range testCases {
+		t.Run(
+			fmt.Sprintf("test case #%d: %s:%s", i, tc.username, tc.password),
+			func(t *testing.T) {
+				username, password := UnprivilegedUser(tc.username, tc.password)
+				assert.Equal(t, tc.expectedUsername, username)
+				assert.Equal(t, password, tc.expectedPassword)
+			},
+		)
+	}
+}
+
+func TestUnprivilegedGroup(t *testing.T) {
+	testCases := []struct {
+		groupName         string
+		expectedGroupName string
+	}{
+		{"", ElasticGroupName},
+		{"custom", "custom"},
+	}
+
+	for i, tc := range testCases {
+		t.Run(
+			fmt.Sprintf("test case #%d: %s", i, tc.groupName),
+			func(t *testing.T) {
+				groupname := UnprivilegedGroup(tc.groupName)
+				assert.Equal(t, tc.expectedGroupName, groupname)
+			},
+		)
+	}
+}
+
 var sampleManifestContent = `
 version: co.elastic.agent/v1
 kind: PackageManifest

internal/pkg/agent/install/install_unix.go

@@ -28,7 +28,7 @@ func fixInstallMarkerPermissions(markerFilePath string, ownership utils.FileOwne
 }
 
 // withServiceOptions just sets the user/group for the service.
-func withServiceOptions(username string, groupName string) ([]serviceOpt, error) {
+func withServiceOptions(username string, groupName string, _ string) ([]serviceOpt, error) {
 	return []serviceOpt{withUserGroup(username, groupName)}, nil
 }
 

internal/pkg/agent/install/install_windows.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 
 	"golang.org/x/sys/windows"
@@ -21,6 +22,13 @@ import (
 	"github.com/elastic/elastic-agent/version"
 )
 
+const (
+	// Conforming to https://learn.microsoft.com/en-us/troubleshoot/windows-server/active-directory/naming-conventions-for-computer-domain-site-ou#domain-names
+	// domain names can contain all alphanumeric characters except for the extended characters that appear in the Disallowed characters list. Names can contain a period, but names can't start with a period.
+	// Disallowed characters: [, ~ : @ # $ % ^ ' . ( ) { } _ {whitespace} \ / ]
+	activeDirectoryUsername = `^[A-Za-z0-9]+(?:\.[A-Za-z0-9]+)*\\[A-Za-z0-9.-]{1,104}$`
+)
+
 // postInstall performs post installation for Windows systems.
 func postInstall(topPath string) error {
 	// delete the top-level elastic-agent.exe
@@ -55,13 +63,24 @@ func fixInstallMarkerPermissions(markerFilePath string, ownership utils.FileOwne
 }
 
 // withServiceOptions just sets the user/group for the service.
-func withServiceOptions(username string, groupName string) ([]serviceOpt, error) {
+func withServiceOptions(username string, groupName string, password string) ([]serviceOpt, error) {
 	if username == "" {
 		// not installed with --unprivileged; nothing to do
 		return []serviceOpt{}, nil
 	}
 
-	// service requires a password to launch as the user
+	if password != "" {
+		if isFullDomainName, err := isWindowsDomainUsername(username); err != nil {
+			return nil, fmt.Errorf("failed to parse username: %w", err)
+		} else if !isFullDomainName {
+			return nil, fmt.Errorf(`username is not in proper format 'domain\username', contains illegal character: ,~:@#$%%^'.(){}_\/ or a whitespace`)
+		}
+
+		// existing user
+		return []serviceOpt{withUserGroup(username, groupName), withPassword(password)}, nil
+	}
+
+	// service requires a password to launch as the use
 	// this sets it to a random password that is only known by the service
 	password, err := RandomPassword()
 	if err != nil {
@@ -109,3 +128,17 @@ func serviceConfigure(ownership utils.FileOwner) error {
 	}
 	return nil
 }
+
+func isWindowsDomainUsername(username string) (bool, error) {
+	if !strings.Contains(username, `\`) {
+		// fail fast
+		return false, nil
+	}
+
+	match, err := regexp.MatchString(activeDirectoryUsername, username)
+	if err != nil {
+		return false, err
+	}
+
+	return match, nil
+}