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// run-pass
// only-x86_64-unknown-linux-gnu
// revisions: ssp no-ssp
// [ssp] compile-flags: -Z stack-protector=all
// compile-flags: -C opt-level=2
// compile-flags: -g
use std::env;
use std::process::{Command, ExitStatus};
fn main() {
if env::args().len() == 1 {
// The test is initially run without arguments. Start the process again,
// this time *with* an argument; in this configuration, the test program
// will deliberately smash the stack.
let cur_argv0 = env::current_exe().unwrap();
let mut child = Command::new(&cur_argv0);
child.arg("stacksmash");
if cfg!(ssp) {
assert_stack_smash_prevented(&mut child);
} else {
assert_stack_smashed(&mut child);
}
} else {
vulnerable_function();
// If we return here the test is broken: it should either have called
// malicious_code() which terminates the process, or be caught by the
// stack check which also terminates the process.
panic!("TEST BUG: stack smash unsuccessful");
}
}
// Avoid inlining to make sure the return address is pushed to stack.
#[inline(never)]
fn vulnerable_function() {
let mut x = 5usize;
let stackaddr = &mut x as *mut usize;
let bad_code_ptr = malicious_code as usize;
// Overwrite the on-stack return address with the address of `malicious_code()`,
// thereby jumping to that function when returning from `vulnerable_function()`.
unsafe { fill(stackaddr, bad_code_ptr, 20); }
}
// Use an uninlined function with its own stack frame to make sure that we don't
// clobber e.g. the counter or address local variable.
#[inline(never)]
unsafe fn fill(addr: *mut usize, val: usize, count: usize) {
let mut addr = addr;
for _ in 0..count {
*addr = val;
addr = addr.add(1);
}
}
// We jump to malicious_code() having wreaked havoc with the previous stack
// frame and not setting up a new one. This function is therefore constrained,
// e.g. both println!() and std::process::exit() segfaults if called. We
// therefore keep the amount of work to a minimum by calling POSIX functions
// directly.
// The function is un-inlined just to make it possible to set a breakpoint here.
#[inline(never)]
fn malicious_code() {
let msg = [112u8, 119u8, 110u8, 101u8, 100u8, 33u8, 0u8]; // "pwned!\0" ascii
unsafe {
write(1, &msg as *const u8, msg.len());
_exit(0);
}
}
extern "C" {
fn write(fd: i32, buf: *const u8, count: usize) -> isize;
fn _exit(status: i32) -> !;
}
fn assert_stack_smash_prevented(cmd: &mut Command) {
let (status, stdout, stderr) = run(cmd);
assert!(!status.success());
assert!(stdout.is_empty());
assert!(stderr.contains("stack smashing detected"));
}
fn assert_stack_smashed(cmd: &mut Command) {
let (status, stdout, stderr) = run(cmd);
assert!(status.success());
assert!(stdout.contains("pwned!"));
assert!(stderr.is_empty());
}
fn run(cmd: &mut Command) -> (ExitStatus, String, String) {
let output = cmd.output().unwrap();
let stdout = String::from_utf8_lossy(&output.stdout);
let stderr = String::from_utf8_lossy(&output.stderr);
println!("status: {}", output.status);
println!("stdout: {}", stdout);
println!("stderr: {}", stderr);
(output.status, stdout.to_string(), stderr.to_string())
}
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