Avoid world-writable file permissions

Docs > Datadog Security > Code Security > Static Code Analysis (SAST) > SAST Rules > Avoid world-writable file permissions

Metadata

ID: rust-security/file-world-writable-permissions

Language: Rust

Severity: Warning

Category: Security

CWE: 732

Related CWEs:

Description

Setting a file’s “other” permission bit to writable (modes like 0o777, 0o666, 0o776, 0o002) lets any local user on the system overwrite the file. This enables privilege escalation if the file is executable, data injection if it’s read by privileged processes, and tampering of secrets, config, or audit logs. Prefer 0o644 for regular files and 0o755 for executables.

Learn More

CWE-732: Incorrect Permission Assignment for Critical Resource

Non-Compliant Code Examples

use std::fs::Permissions;
use std::os::unix::fs::PermissionsExt;

fn invalid() -> std::io::Result<()> {
    // World-writable — classic mistakes
    let _ = Permissions::from_mode(0o777);
    let _ = Permissions::from_mode(0o666);

    // Method form
    let mut p = Permissions::from_mode(0o600);
    p.set_mode(0o777);
    p.set_mode(0o666);

    // Other world-writable triplets
    let _ = Permissions::from_mode(0o776);    // last digit 6 — rw for others
    let _ = Permissions::from_mode(0o002);    // last digit 2 — write only
    let _ = Permissions::from_mode(0o773);    // last digit 3 — wx for others

    // 4-digit (with sticky/setuid) — still world-writable
    let _ = Permissions::from_mode(0o7777);

    // Via the trait name
    let _ = PermissionsExt::from_mode(0o777);

    // Fully qualified
    let _ = std::os::unix::fs::PermissionsExt::from_mode(0o666);

    // Underscore separators
    let _ = Permissions::from_mode(0o7_7_7);

    Ok(())
}

Compliant Code Examples

use std::fs::Permissions;
use std::os::unix::fs::PermissionsExt;

fn valid() -> std::io::Result<()> {
    // Restrictive modes — no world write
    let _ = Permissions::from_mode(0o644);            // owner rw, group/other r
    let _ = Permissions::from_mode(0o755);            // typical executable
    let _ = Permissions::from_mode(0o600);            // owner-only rw
    let _ = Permissions::from_mode(0o770);            // group-writable but NOT world
    let _ = Permissions::from_mode(0o640);            // last digit 0 — fine

    // Method form, restrictive mode
    let mut p = Permissions::from_mode(0o644);
    p.set_mode(0o755);

    // Non-literal mode — can't tell statically, don't flag
    let mode: u32 = std::env::var("MODE").unwrap().parse().unwrap();
    p.set_mode(mode);

    // Unrelated method named set_mode but with non-octal literal
    struct Widget;
    impl Widget {
        fn set_mode(&self, _: u32) {}
    }
    let w = Widget;
    w.set_mode(0o644);

    Ok(())
}