inputoutput.md

Input-output examples

The input to each example is a Rust function. The output to each example whether or not there exists an input to the function that can cause the function to violate a certain safety property. Each example is located in the examples directory numbered accordingly.

All examples use these:

use std::fs;
use std::path::PathBuf;
use std::io::{self, ErrorKind};

1. This function does contain an input (filename: /proc/self/mem) such that a safety property (write to /proc/self/mem) is violated.

pub fn write_to_file(contents: &str, filename: &str) -> io::Result<()> {
    fs::write(filename, contents)?;
    Ok(())
}

LHS output (excerpt):

WARNING: potential write to `/proc/self/mem`
        examples/ex1.rs:5:5: 5:14 (#0)

2. This function also contains an input (filename: /proc/../proc/self/mem) such that a safety property (write to /proc/self/mem) is violated.

pub fn write_to_file_safe(contents: &str, filename: &str) -> io::Result<()> {
    if filename == "/proc/self/mem" {
        return Err(io::Error::new(ErrorKind::Other, "Unsafe write!"));
    }
    fs::write(filename, contents)?;
    Ok(())
}

LHS output (excerpt):

WARNING: potential write to `/proc/self/mem`
        examples/ex2.rs:8:5: 8:14 (#0)

3. This function contains no input such that a write to /proc/self/mem occurs.

pub fn write_to_file_actually_safe(contents: &str, filename: &str) -> io::Result<()> {
    let filename_realpath: PathBuf = fs::canonicalize(filename)?;
    let unsafe_path: PathBuf = fs::canonicalize("/proc/self/mem")?;
    if filename_realpath == unsafe_path {
        return Err(io::Error::new(ErrorKind::Other, "Unsafe write!"));
    }
    fs::write(filename_realpath, contents)?;
    Ok(())
}

LHS output (excerpt):

No potential writes to `/proc/self/mem` detected!

4. This function contains an input (operation: |x| {fs::write("hello", "/proc/self/mem"); x})such that a write to /proc/self/mem occurs.

pub fn apply_operation_twice(num: i32, operation: impl Fn(i32) -> i32) -> i32 {
    operation(operation(num))
}

LHS output (excerpt):

No potential writes to `/proc/self/mem` detected!

Note, this is intended behavior as LHS evaluates every single function located in the source file. It does not attempt to trace through function logic that is being called upon.

5. This function contains no input such that a write to /proc/self/mem occurs.

pub fn write_to_hw3(contents: &str)-> io::Result<()> {
    Ok(fs::write("~/UCDavis/PL/2024/summer/REU/LHS/main.rs", contents)?)
}

LHS output (excerpt):

No potential writes to `/proc/self/mem` detected!

6. The following two functions showcases the if/else branching traces.

a) Write to /proc/self/mem occurs:

fn main() {
    let x: isize = 1;
    if x == 1 {
        std::fs::write("/proc/self/mem", "dangerous write");
    } else {
        println!("Harmless print");
    }
}

LHS output (excerpt):

WARNING: potential write to `/proc/self/mem`
        examples/ex6a.rs:4:9: 4:23 (#0)

b) Write to /proc/self/mem does not occur:

fn main() {
    let x: isize = 0;
    if x == 1 {
        std::fs::write("/proc/self/mem", "this is skipped");
    } else {
        println!("This is printed");
    }
}

LHS output (excerpt):

No potential writes to `/proc/self/mem` detected!