[client] Resolve profiles for the sudo invoking user instead of root

The SSH server flags force `netbird up` through sudo, but the CLI resolved
every per-user path with the process user. As root that reads root's own
(empty) local state, so a `sudo netbird up` silently switched the daemon from
the user's profile to the default one — cancelling any login already waiting
in the browser — and then ran an SSO login for the default profile's config.
Whichever account that login returned, the default profile's peer belongs to
someone else, so every attempt ended in "peer is already registered by a
different User or a Setup Key", with nothing telling the user why.

Resolve the acting user through SUDO_USER when running as root: the active
profile, the profile config paths and the stored account email now come from
the invoking user's directories. Privilege decisions are untouched — they stay
on the kernel credentials of the daemon connection, which an environment
variable can never influence; a forged SUDO_USER only selects a profile root
could select anyway.

The invoking user's directories are strictly read-only under sudo. Anything
root wrote there would be root-owned and break the user's own runs, so instead
of chowning files back, the local writes are skipped: the active-profile
bookkeeping and the account-email state simply do not update from a sudo run
(the daemon records the switch on its side; a skipped email write costs at
most one extra account prompt later).

Plain root — no sudo context — has no user to act for, so the ambiguity is
refused instead of guessed at: when the daemon's active profile differs from
what root resolves and no --profile was given, up fails with a message naming
both profiles, instead of silently switching the daemon and failing later with
the ownership error.

client/cmd/debug.go

@@ -3,7 +3,6 @@ package cmd
 import (
 	"context"
 	"fmt"
-	"os/user"
 	"strings"
 	"time"
 
@@ -114,7 +113,7 @@ func debugConfigDump(cmd *cobra.Command, _ []string) error {
 	if err != nil {
 		return fmt.Errorf("get active profile: %v", err)
 	}
-	currUser, err := user.Current()
+	currUser, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %v", err)
 	}

client/cmd/login.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"os"
-	"os/user"
 	"strings"
 
 	log "github.com/sirupsen/logrus"
@@ -53,7 +52,7 @@ var loginCmd = &cobra.Command{
 			// nolint
 			ctx = context.WithValue(ctx, system.DeviceNameCtxKey, hostName)
 		}
-		username, err := user.Current()
+		username, err := profilemanager.InvokingUser()
 		if err != nil {
 			return fmt.Errorf("get current user: %v", err)
 		}

client/cmd/logout.go

@@ -3,11 +3,11 @@ package cmd
 import (
 	"context"
 	"fmt"
-	"os/user"
 	"time"
 
 	"github.com/spf13/cobra"
 
+	"github.com/netbirdio/netbird/client/internal/profilemanager"
 	"github.com/netbirdio/netbird/client/proto"
 )
 
@@ -37,7 +37,7 @@ var logoutCmd = &cobra.Command{
 		if profileName != "" {
 			req.ProfileName = &profileName
 
-			currUser, err := user.Current()
+			currUser, err := profilemanager.InvokingUser()
 			if err != nil {
 				return fmt.Errorf("get current user: %v", err)
 			}

client/cmd/profile.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"os/user"
 	"strings"
 	"text/tabwriter"
 	"time"
@@ -97,7 +96,7 @@ func listProfilesFunc(cmd *cobra.Command, _ []string) error {
 	}
 	defer conn.Close()
 
-	currUser, err := user.Current()
+	currUser, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %w", err)
 	}
@@ -138,7 +137,7 @@ func addProfileFunc(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	currUser, err := user.Current()
+	currUser, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %w", err)
 	}
@@ -179,7 +178,7 @@ func renameProfileFunc(cmd *cobra.Command, args []string) error {
 	}
 	defer conn.Close()
 
-	currUser, err := user.Current()
+	currUser, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %w", err)
 	}
@@ -233,7 +232,7 @@ func removeProfileFunc(cmd *cobra.Command, args []string) error {
 	}
 	defer conn.Close()
 
-	currUser, err := user.Current()
+	currUser, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %w", err)
 	}
@@ -261,7 +260,7 @@ func selectProfileFunc(cmd *cobra.Command, args []string) error {
 	profileManager := profilemanager.NewProfileManager()
 	handle := args[0]
 
-	currUser, err := user.Current()
+	currUser, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %w", err)
 	}

client/cmd/up.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"net"
 	"net/netip"
-	"os/user"
 	"runtime"
 	"strings"
 	"time"
@@ -122,7 +121,7 @@ func upFunc(cmd *cobra.Command, args []string) error {
 
 	pm := profilemanager.NewProfileManager()
 
-	username, err := user.Current()
+	username, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %v", err)
 	}
@@ -295,6 +294,21 @@ func runInDaemonMode(ctx context.Context, cmd *cobra.Command, pm *profilemanager
 
 	client := proto.NewDaemonServiceClient(conn)
 
+	// Plain root has no invoking user to resolve profiles for, so the local
+	// state falls back to root's own — the default profile. Acting on that
+	// while the daemon runs another user's profile would silently switch the
+	// daemon away from it (and a later browser login would register the
+	// default profile's peer under whichever account the IdP returns). Refuse
+	// the ambiguity instead of guessing.
+	if profilemanager.IsPlainRoot() && profileName == "" {
+		if active, err := client.GetActiveProfile(ctx, &proto.GetActiveProfileRequest{}); err == nil &&
+			active.GetId() != "" && active.GetId() != activeProf.ID.String() {
+			return fmt.Errorf(
+				"running as root: the daemon's active profile is %q (user %q), but this invocation resolves to %q; pass --profile to choose one explicitly, or run via sudo from your own user",
+				active.GetProfileName(), active.GetUsername(), activeProf.ID)
+		}
+	}
+
 	status, err := client.Status(ctx, &proto.StatusRequest{
 		WaitForReady: func() *bool { b := true; return &b }(),
 	})
@@ -314,7 +328,7 @@ func runInDaemonMode(ctx context.Context, cmd *cobra.Command, pm *profilemanager
 		}
 	}
 
-	username, err := user.Current()
+	username, err := profilemanager.InvokingUser()
 	if err != nil {
 		return fmt.Errorf("get current user: %v", err)
 	}