shim: user switcher process management struct

This change moves all user switcher and shim management to the shim package and withholds output while shim is alive. This also eliminated all exit scenarios where revert is skipped.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/shim/payload.go

@@ -1,6 +1,13 @@
 package shim
 
-import "git.ophivana.moe/security/fortify/helper/bwrap"
+import (
+	"encoding/gob"
+	"errors"
+	"net"
+
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
 
 const EnvShim = "FORTIFY_SHIM"
 
@@ -17,3 +24,19 @@ type Payload struct {
 	// verbosity pass through
 	Verbose bool
 }
+
+func (p *Payload) serve(conn *net.UnixConn, wl *Wayland) error {
+	if err := gob.NewEncoder(conn).Encode(*p); err != nil {
+		return fmsg.WrapErrorSuffix(err,
+			"cannot stream shim payload:")
+	}
+
+	if wl != nil {
+		if err := wl.WriteUnix(conn); err != nil {
+			return errors.Join(err, conn.Close())
+		}
+	}
+
+	return fmsg.WrapErrorSuffix(conn.Close(),
+		"cannot close setup connection:")
+}