proc: remove duplicate compile-time fortify reference

This is no longer needed since shim and init are now part of the main program.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/path.go

@@ -3,8 +3,7 @@ package internal
 import "path"
 
 var (
-	Fortify = compPoison
-	Fsu     = compPoison
+	Fsu = compPoison
 )
 
 func Path(p string) (string, bool) {

internal/proc/priv/shim/main.go

@@ -37,14 +37,6 @@ func Main() {
 		}
 	}
 
-	// check path to fortify
-	var fortifyPath string
-	if p, ok := internal.Path(internal.Fortify); !ok {
-		fmsg.Fatal("invalid fortify path, this copy of fortify is not compiled correctly")
-	} else {
-		fortifyPath = p
-	}
-
 	// receive setup payload
 	var (
 		payload    Payload
@@ -135,7 +127,7 @@ func Main() {
 	// bind fortify inside sandbox
 	innerSbin := path.Join(fst.Tmp, "sbin")
 	fortifyInnerPath := path.Join(innerSbin, "fortify")
-	conf.Bind(fortifyPath, fortifyInnerPath)
+	conf.Bind(proc.MustExecutable(), fortifyInnerPath)
 	conf.Symlink(fortifyInnerPath, path.Join(innerSbin, "init"))
 
 	helper.BubblewrapName = payload.Exec[0] // resolved bwrap path by parent

internal/proc/priv/shim/manager.go

@@ -56,7 +56,7 @@ func (s *Shim) WaitFallback() chan error {
 func (s *Shim) Start() (*time.Time, error) {
 	// prepare user switcher invocation
 	var fsu string
-	if p, ok := internal.Check(internal.Fsu); !ok {
+	if p, ok := internal.Path(internal.Fsu); !ok {
 		fmsg.Fatal("invalid fsu path, this copy of fortify is not compiled correctly")
 		panic("unreachable")
 	} else {

internal/proc/self.go

@@ -0,0 +1,26 @@
+package proc
+
+import (
+	"os"
+	"sync"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+var (
+	executable     string
+	executableOnce sync.Once
+)
+
+func copyExecutable() {
+	if name, err := os.Executable(); err != nil {
+		fmsg.Fatalf("cannot read executable path: %v", err)
+	} else {
+		executable = name
+	}
+}
+
+func MustExecutable() string {
+	executableOnce.Do(copyExecutable)
+	return executable
+}