cmd: shim and init into separate binaries

This change also fixes a deadlock when shim fails to connect and complete the setup.

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

cmd/fshim/ipc/payload.go

@@ -0,0 +1,42 @@
+package shim0
+
+import (
+	"encoding/gob"
+	"errors"
+	"net"
+
+	"git.ophivana.moe/security/fortify/helper/bwrap"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+const Env = "FORTIFY_SHIM"
+
+type Payload struct {
+	// child full argv
+	Argv []string
+	// bwrap, target full exec path
+	Exec [2]string
+	// bwrap config
+	Bwrap *bwrap.Config
+	// whether to pass wayland fd
+	WL bool
+
+	// 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:")
+}