drop-root-caps 1.1.2

A simple crate to drop 'root' user capabilities on Linux
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

# Drop Root Capabilities

[![no_std](https://img.shields.io/badge/rust-no__std-orchid?logo=rust)](https://docs.rust-embedded.org/book/intro/no-std.html)
[![Crates.io](https://img.shields.io/crates/v/drop-root-caps)](https://crates.io/crates/drop-root-caps)
[![Downloads](https://img.shields.io/crates/d/drop-root-caps)](https://crates.io/crates/drop-root-caps)
[![License](https://img.shields.io/crates/l/sponge-hash-aes256)](https://opensource.org/license/0BSD)

A simple crate to drop "root" user capabilities on Linux.

On Linux, the "root" user (UID 0) has some special capabilities that "regular" users do **not** normally have. This can result in weird behavior, e.g., if unit tests (or integration tests) are executed in the context of the "root" user, as Docker® containers do by default! For example, a file that **should not** be accessible (according to its access permissions) may suddenly become accessible – because the "root" user has the `CAP_DAC_OVERRIDE` capability, which allows the "root" user to access the file *regardless of the access permissions*. As a result, a test case that expects `File::open()` to return a "permission denied" error (and rightfully so!) will suddenly start to fail 😨

This crate uses the Linux syscall [`prctl()`](https://man7.org/linux/man-pages/man2/prctl.2.html) with argument [`PR_CAPBSET_DROP`](https://man7.org/linux/man-pages/man2/PR_CAPBSET_DROP.2const.html) to drop the "root"-specific capabilities at application startup and thus restores the expected behavior. It does *nothing* on other platforms.

## Usage

Add the following to your **`Cargo.toml`** file:

```
[dev-dependencies]
drop-root-caps = "1.1.2"
```

You probably do **not** want to add this crate to your `[dependencies]`, *only* to the `[dev-dependencies]` 💡

Also, you **must** add the following code to your test module(s), because otherwise the Rust compiler optimizes away the `drop-root-caps` dependency 😬

```
#[used]
static DROP_ROOT_CAPS: () = drop_root_caps::set_up();
```

## License

This software is released under the BSD Zero Clause (“0BSD”) License.

Copyright (C) 2025 by LoRd_MuldeR <mulder2@gmx.de>.