💾 Archived View for thebackupbox.net › ~epoch › blog › sticky captured on 2024-12-17 at 10:13:11. Gemini links have been rewritten to link to archived content

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experiment with sticky bit on programs

I was wondering if a sticky bit on a program would prevent LD_PRELOAD from working.

Similar to how an suid or sgid bit prevents it from working.

epoch@batou$ cat test.c
#include <stdio.h>

int main(int argc,char *argv[]) {
  puts("ohai");
  return 0;
}
epoch@batou$ gcc -o test test.c
epoch@batou$ cat lib.c
int puts(char *s) {
  return printf("lol hacked: %s\n",s);
}
epoch@batou$ gcc -fPIC -shared -o lib.so lib.c
[warnings]
epoch@batou$ chmod o+t test-sticky
epoch@batou$ ./test
ohai
epoch@batou$ ./test-sticky 
ohai
epoch@batou$ LD_PRELOAD=$(pwd)/lib.so ./test
lol hacked: ohai
epoch@batou$ LD_PRELOAD=$(pwd)/lib.so ./test-sticky 
lol hacked: ohai

A sticky bit on a program doesn't prevent LD_PRELOAD from working.

Oh well.

Guess a static binary would work for LD_PRELOAD-safe program.