greeter: Add support for Debian greetd user/group name (#1685)

* greeter: Detect user and group used by greetd

On most distros greetd runs as user and group "greeter",
but on Debian the user and group "_greetd" are used.

* greeter: Use correct group in sync command

* greeter: more generic group detection

---------

Co-authored-by: bbedward <bbedward@gmail.com>

core/cmd/dms/commands_greeter.go

@@ -169,7 +169,8 @@ func syncGreeter() error {
 		return fmt.Errorf("greeter cache directory not found at %s\nPlease install the greeter first", cacheDir)
 	}
 
-	greeterGroupExists := checkGroupExists("greeter")
+	greeterGroup := greeter.DetectGreeterGroup()
+	greeterGroupExists := utils.HasGroup(greeterGroup)
 	if greeterGroupExists {
 		currentUser, err := user.Current()
 		if err != nil {
@@ -182,24 +183,24 @@ func syncGreeter() error {
 			return fmt.Errorf("failed to check groups: %w", err)
 		}
 
-		inGreeterGroup := strings.Contains(string(groupsOutput), "greeter")
+		inGreeterGroup := strings.Contains(string(groupsOutput), greeterGroup)
 		if !inGreeterGroup {
-			fmt.Println("\n⚠ Warning: You are not in the greeter group.")
+			fmt.Printf("\n⚠ Warning: You are not in the %s group.\n", greeterGroup)
-			fmt.Print("Would you like to add your user to the greeter group? (Y/n): ")
+			fmt.Printf("Would you like to add your user to the %s group? (Y/n): ", greeterGroup)
 
 			var response string
 			fmt.Scanln(&response)
 			response = strings.ToLower(strings.TrimSpace(response))
 
 			if response != "n" && response != "no" {
-				fmt.Println("\nAdding user to greeter group...")
+				fmt.Printf("\nAdding user to %s group...\n", greeterGroup)
-				addUserCmd := exec.Command("sudo", "usermod", "-aG", "greeter", currentUser.Username)
+				addUserCmd := exec.Command("sudo", "usermod", "-aG", greeterGroup, currentUser.Username)
 				addUserCmd.Stdout = os.Stdout
 				addUserCmd.Stderr = os.Stderr
 				if err := addUserCmd.Run(); err != nil {
-					return fmt.Errorf("failed to add user to greeter group: %w", err)
+					return fmt.Errorf("failed to add user to %s group: %w", greeterGroup, err)
 				}
-				fmt.Println("✓ User added to greeter group")
+				fmt.Printf("✓ User added to %s group\n", greeterGroup)
 				fmt.Println("⚠ You will need to log out and back in for the group change to take effect")
 			} else {
 				return fmt.Errorf("aborted: user must be in the greeter group before syncing")
@@ -245,21 +246,6 @@ func syncGreeter() error {
 	return nil
 }
 
-func checkGroupExists(groupName string) bool {
-	data, err := os.ReadFile("/etc/group")
-	if err != nil {
-		return false
-	}
-
-	lines := strings.SplitSeq(string(data), "\n")
-	for line := range lines {
-		if strings.HasPrefix(line, groupName+":") {
-			return true
-		}
-	}
-	return false
-}
-
 func disableDisplayManager(dmName string) (bool, error) {
 	state, err := getSystemdServiceState(dmName)
 	if err != nil {

core/internal/greeter/installer.go

@@ -22,6 +22,21 @@ func DetectDMSPath() (string, error) {
 	return config.LocateDMSConfig()
 }
 
+func DetectGreeterGroup() string {
+	data, err := os.ReadFile("/etc/group")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "⚠ Warning: could not read /etc/group, defaulting to greeter")
+		return "greeter"
+	}
+
+	if group, found := utils.FindGroupData(string(data), "greeter", "greetd", "_greeter"); found {
+		return group
+	}
+
+	fmt.Fprintln(os.Stderr, "⚠ Warning: no greeter group found in /etc/group, defaulting to greeter")
+	return "greeter"
+}
+
 // DetectCompositors checks which compositors are installed
 func DetectCompositors() []string {
 	var compositors []string
@@ -194,14 +209,17 @@ func CopyGreeterFiles(dmsPath, compositor string, logFunc func(string), sudoPass
 		return fmt.Errorf("failed to create cache directory: %w", err)
 	}
 
-	if err := runSudoCmd(sudoPassword, "chown", "greeter:greeter", cacheDir); err != nil {
+	group := DetectGreeterGroup()
+	owner := fmt.Sprintf("%s:%s", group, group)
+
+	if err := runSudoCmd(sudoPassword, "chown", owner, cacheDir); err != nil {
 		return fmt.Errorf("failed to set cache directory owner: %w", err)
 	}
 
 	if err := runSudoCmd(sudoPassword, "chmod", "755", cacheDir); err != nil {
 		return fmt.Errorf("failed to set cache directory permissions: %w", err)
 	}
-	logFunc(fmt.Sprintf("✓ Created cache directory %s (owner: greeter:greeter, permissions: 755)", cacheDir))
+	logFunc(fmt.Sprintf("✓ Created cache directory %s (owner: %s, permissions: 755)", cacheDir, owner))
 
 	return nil
 }
@@ -234,6 +252,8 @@ func SetupParentDirectoryACLs(logFunc func(string), sudoPassword string) error {
 		{filepath.Join(homeDir, ".local", "share"), ".local/share directory"},
 	}
 
+	owner := DetectGreeterGroup()
+
 	logFunc("\nSetting up parent directory ACLs for greeter user access...")
 
 	for _, dir := range parentDirs {
@@ -245,9 +265,9 @@ func SetupParentDirectoryACLs(logFunc func(string), sudoPassword string) error {
 		}
 
 		// Set ACL to allow greeter user read+execute permission (for session discovery)
-		if err := runSudoCmd(sudoPassword, "setfacl", "-m", "u:greeter:rx", dir.path); err != nil {
+		if err := runSudoCmd(sudoPassword, "setfacl", "-m", fmt.Sprintf("u:%s:rx", owner), dir.path); err != nil {
 			logFunc(fmt.Sprintf("⚠ Warning: Failed to set ACL on %s: %v", dir.desc, err))
-			logFunc(fmt.Sprintf("  You may need to run manually: setfacl -m u:greeter:x %s", dir.path))
+			logFunc(fmt.Sprintf("  You may need to run manually: setfacl -m u:%s:x %s", owner, dir.path))
 			continue
 		}
 
@@ -271,17 +291,19 @@ func SetupDMSGroup(logFunc func(string), sudoPassword string) error {
 		return fmt.Errorf("failed to determine current user")
 	}
 
+	group := DetectGreeterGroup()
+
 	// Check if user is already in greeter group
 	groupsCmd := exec.Command("groups", currentUser)
 	groupsOutput, err := groupsCmd.Output()
-	if err == nil && strings.Contains(string(groupsOutput), "greeter") {
+	if err == nil && strings.Contains(string(groupsOutput), group) {
-		logFunc(fmt.Sprintf("✓ %s is already in greeter group", currentUser))
+		logFunc(fmt.Sprintf("✓ %s is already in %s group", currentUser, group))
 	} else {
 		// Add current user to greeter group for file access permissions
-		if err := runSudoCmd(sudoPassword, "usermod", "-aG", "greeter", currentUser); err != nil {
+		if err := runSudoCmd(sudoPassword, "usermod", "-aG", group, currentUser); err != nil {
-			return fmt.Errorf("failed to add %s to greeter group: %w", currentUser, err)
+			return fmt.Errorf("failed to add %s to %s group: %w", currentUser, group, err)
 		}
-		logFunc(fmt.Sprintf("✓ Added %s to greeter group (logout/login required for changes to take effect)", currentUser))
+		logFunc(fmt.Sprintf("✓ Added %s to %s group (logout/login required for changes to take effect)", currentUser, group))
 	}
 
 	configDirs := []struct {
@@ -304,7 +326,7 @@ func SetupDMSGroup(logFunc func(string), sudoPassword string) error {
 			}
 		}
 
-		if err := runSudoCmd(sudoPassword, "chgrp", "-R", "greeter", dir.path); err != nil {
+		if err := runSudoCmd(sudoPassword, "chgrp", "-R", group, dir.path); err != nil {
 			logFunc(fmt.Sprintf("⚠ Warning: Failed to set group for %s: %v", dir.desc, err))
 			continue
 		}
@@ -436,10 +458,11 @@ func syncNiriGreeterConfig(logFunc func(string), sudoPassword string) error {
 	}
 
 	greeterDir := "/etc/greetd/niri"
+	greeterGroup := DetectGreeterGroup()
 	if err := runSudoCmd(sudoPassword, "mkdir", "-p", greeterDir); err != nil {
 		return fmt.Errorf("failed to create greetd niri directory: %w", err)
 	}
-	if err := runSudoCmd(sudoPassword, "chown", "root:greeter", greeterDir); err != nil {
+	if err := runSudoCmd(sudoPassword, "chown", fmt.Sprintf("root:%s", greeterGroup), greeterDir); err != nil {
 		return fmt.Errorf("failed to set greetd niri directory ownership: %w", err)
 	}
 	if err := runSudoCmd(sudoPassword, "chmod", "755", greeterDir); err != nil {
@@ -464,7 +487,7 @@ func syncNiriGreeterConfig(logFunc func(string), sudoPassword string) error {
 	if err := backupFileIfExists(sudoPassword, dmsPath, ".backup"); err != nil {
 		return fmt.Errorf("failed to backup %s: %w", dmsPath, err)
 	}
-	if err := runSudoCmd(sudoPassword, "install", "-o", "root", "-g", "greeter", "-m", "0644", dmsTemp.Name(), dmsPath); err != nil {
+	if err := runSudoCmd(sudoPassword, "install", "-o", "root", "-g", greeterGroup, "-m", "0644", dmsTemp.Name(), dmsPath); err != nil {
 		return fmt.Errorf("failed to install greetd niri dms config: %w", err)
 	}
 
@@ -487,7 +510,7 @@ func syncNiriGreeterConfig(logFunc func(string), sudoPassword string) error {
 	if err := backupFileIfExists(sudoPassword, mainPath, ".backup"); err != nil {
 		return fmt.Errorf("failed to backup %s: %w", mainPath, err)
 	}
-	if err := runSudoCmd(sudoPassword, "install", "-o", "root", "-g", "greeter", "-m", "0644", mainTemp.Name(), mainPath); err != nil {
+	if err := runSudoCmd(sudoPassword, "install", "-o", "root", "-g", greeterGroup, "-m", "0644", mainTemp.Name(), mainPath); err != nil {
 		return fmt.Errorf("failed to install greetd niri main config: %w", err)
 	}
 
@@ -736,17 +759,19 @@ func ConfigureGreetd(dmsPath, compositor string, logFunc func(string), sudoPassw
 		logFunc(fmt.Sprintf("✓ Backed up existing config to %s", backupPath))
 	}
 
+	greeterUser := DetectGreeterGroup()
+
 	var configContent string
 	if data, err := os.ReadFile(configPath); err == nil {
 		configContent = string(data)
 	} else {
-		configContent = `[terminal]
+		configContent = fmt.Sprintf(`[terminal]
 vt = 1
 
 [default_session]
 
-user = "greeter"
+user = "%s"
-`
+`, greeterUser)
 	}
 
 	lines := strings.Split(configContent, "\n")
@@ -755,7 +780,7 @@ user = "greeter"
 		trimmed := strings.TrimSpace(line)
 		if !strings.HasPrefix(trimmed, "command =") && !strings.HasPrefix(trimmed, "command=") {
 			if strings.HasPrefix(trimmed, "user =") || strings.HasPrefix(trimmed, "user=") {
-				newLines = append(newLines, `user = "greeter"`)
+				newLines = append(newLines, fmt.Sprintf(`user = "%s"`, greeterUser))
 			} else {
 				newLines = append(newLines, line)
 			}
@@ -807,7 +832,7 @@ user = "greeter"
 		return fmt.Errorf("failed to move config to /etc/greetd: %w", err)
 	}
 
-	logFunc(fmt.Sprintf("✓ Updated greetd configuration (user: greeter, command: %s --command %s -p %s)", wrapperCmd, compositorLower, dmsPath))
+	logFunc(fmt.Sprintf("✓ Updated greetd configuration (user: %s, command: %s --command %s -p %s)", greeterUser, wrapperCmd, compositorLower, dmsPath))
 	return nil
 }
 

core/internal/utils/group.go

@@ -0,0 +1,37 @@
+package utils
+
+import (
+	"os"
+	"strings"
+)
+
+func HasGroup(groupName string) bool {
+	return HasGroupIn(groupName, "/etc/group")
+}
+
+func HasGroupIn(groupName, path string) bool {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return false
+	}
+	return HasGroupData(groupName, string(data))
+}
+
+func HasGroupData(groupName, data string) bool {
+	prefix := groupName + ":"
+	for line := range strings.SplitSeq(data, "\n") {
+		if strings.HasPrefix(line, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+func FindGroupData(data string, candidates ...string) (string, bool) {
+	for _, candidate := range candidates {
+		if HasGroupData(candidate, data) {
+			return candidate, true
+		}
+	}
+	return "", false
+}

core/internal/utils/group_test.go

@@ -0,0 +1,142 @@
+package utils
+
+import "testing"
+
+const testGroupData = `root:x:0:brltty,root
+sys:x:3:bin,testuser
+mem:x:8:
+ftp:x:11:
+mail:x:12:
+log:x:19:
+smmsp:x:25:
+proc:x:26:
+games:x:50:
+lock:x:54:
+network:x:90:
+floppy:x:94:
+scanner:x:96:
+power:x:98:
+nobody:x:65534:
+adm:x:999:daemon
+wheel:x:998:testuser
+utmp:x:997:
+audio:x:996:brltty
+disk:x:995:
+input:x:994:brltty,testuser,greeter
+kmem:x:993:
+kvm:x:992:libvirt-qemu,qemu,testuser
+lp:x:991:cups,testuser
+optical:x:990:
+render:x:989:
+sgx:x:988:
+storage:x:987:
+tty:x:5:brltty
+uucp:x:986:brltty
+video:x:985:cosmic-greeter,greeter,testuser
+users:x:984:
+groups:x:983:
+systemd-journal:x:982:
+rfkill:x:981:
+bin:x:1:daemon
+daemon:x:2:bin
+http:x:33:
+dbus:x:81:
+systemd-coredump:x:980:
+systemd-network:x:979:
+systemd-oom:x:978:
+systemd-journal-remote:x:977:
+systemd-resolve:x:976:
+systemd-timesync:x:975:
+tss:x:974:
+uuidd:x:973:
+alpm:x:972:
+polkitd:x:102:
+testuser:x:1000:
+avahi:x:971:
+git:x:970:
+nvidia-persistenced:x:143:
+i2c:x:969:testuser
+seat:x:968:
+rtkit:x:133:
+brlapi:x:967:brltty
+gdm:x:120:
+brltty:x:966:
+colord:x:965:
+flatpak:x:964:
+geoclue:x:963:testuser
+gnome-remote-desktop:x:962:
+saned:x:961:
+usbmux:x:140:
+cosmic-greeter:x:960:
+greeter:x:959:testuser
+openvpn:x:958:
+nm-openvpn:x:957:
+named:x:40:
+_talkd:x:956:
+keyd:x:955:
+cups:x:209:testuser
+docker:x:954:testuser
+mysql:x:953:
+radicale:x:952:
+onepassword:x:1001:
+nixbld:x:951:nixbld01,nixbld02,nixbld03,nixbld04,nixbld05,nixbld06,nixbld07,nixbld08,nixbld09,nixbld10
+virtlogin:x:940:
+libvirt:x:939:testuser
+libvirt-qemu:x:938:
+qemu:x:937:
+dnsmasq:x:936:
+clock:x:935:
+dms-greeter:x:1002:greeter,testuser
+pcscd:x:934:
+test:x:1003:
+empower:x:933:
+`
+
+func TestHasGroupData(t *testing.T) {
+	tests := []struct {
+		group string
+		want  bool
+	}{
+		{"greeter", true},
+		{"root", true},
+		{"docker", true},
+		{"cosmic-greeter", true},
+		{"dms-greeter", true},
+		{"nonexistent", false},
+		{"greet", false},
+	}
+
+	for _, tt := range tests {
+		if got := HasGroupData(tt.group, testGroupData); got != tt.want {
+			t.Errorf("HasGroupData(%q) = %v, want %v", tt.group, got, tt.want)
+		}
+	}
+}
+
+func TestFindGroupData(t *testing.T) {
+	tests := []struct {
+		name       string
+		candidates []string
+		wantGroup  string
+		wantFound  bool
+	}{
+		{"first match wins", []string{"greeter", "greetd", "_greeter"}, "greeter", true},
+		{"fallback to second", []string{"greetd", "greeter"}, "greeter", true},
+		{"none found", []string{"_greetd", "greetd"}, "", false},
+		{"single match", []string{"docker"}, "docker", true},
+	}
+
+	for _, tt := range tests {
+		got, found := FindGroupData(testGroupData, tt.candidates...)
+		if got != tt.wantGroup || found != tt.wantFound {
+			t.Errorf("%s: FindGroupData(%v) = (%q, %v), want (%q, %v)",
+				tt.name, tt.candidates, got, found, tt.wantGroup, tt.wantFound)
+		}
+	}
+}
+
+func TestHasGroupDataEmpty(t *testing.T) {
+	if HasGroupData("greeter", "") {
+		t.Error("expected false for empty data")
+	}
+}