libnss-rs

Rust bindings for creating libnss modules.

Currently supports the following databases:

• passwd
• shadow
• group
• hosts

Getting started

• Create a new library

cargo new nss_example --lib

• Change library type to cdylib in your Cargo.toml

[lib]
name = "nss_example"
crate-type = [ "cdylib" ]

*** NOTE *** The name of the crate itself is not important, however the library itself must follow the nss_xxx pattern.

• Add libnss to your Cargo.toml

[dependencies]
libc = "0.2.0"
lazy_static = "1.3.0"
paste = "0.1"
libnss = "0.1.0"

• Add the following to your src/main.rs

extern crate libc;
#[macro_use]
extern crate lazy_static;
#[macro_use]
extern crate libnss;

• Implement a passwd database

use libnss::passwd::{PasswdHooks, Passwd};

struct ExamplePasswd;
libnss_passwd_hooks!(example, ExamplePasswd);

It is important that the first param of libnss_passwd_hooks is the name of your final library libnss_example.so.2

impl PasswdHooks for HardcodedPasswd {
    fn get_all_entries() -> Vec<Passwd> {
        vec![
            Passwd {
                name: "test".to_string(),
                passwd: "x".to_string(),
                uid: 1005,
                gid: 1005,
                gecos: "Test Account".to_string(),
                dir: "/home/test".to_string(),
                shell: "/bin/bash".to_string(),
            }
        ]
    }

    fn get_entry_by_uid(uid: libc::uid_t) -> Option<Passwd> {
        if uid == 1005 {
            return Some(Passwd {
                name: "test".to_string(),
                passwd: "x".to_string(),
                uid: 1005,
                gid: 1005,
                gecos: "Test Account".to_string(),
                dir: "/home/test".to_string(),
                shell: "/bin/bash".to_string(),
            });
        }

        None
    }

    fn get_entry_by_name(name: String) -> Option<Passwd> {
        if name == "test" {
            return Some(Passwd {
                name: "test".to_string(),
                passwd: "x".to_string(),
                uid: 1005,
                gid: 1005,
                gecos: "Test Account".to_string(),
                dir: "/home/test".to_string(),
                shell: "/bin/bash".to_string(),
            });
        }

        None
    }
}

• Install the library

cd target/release
cp libnss_example.so libnss_example.so.2
sudo install -m 0644 libnss_example.so.2 /lib
sudo /sbin/ldconfig -n /lib /usr/lib

• Enable your nss module in /etc/nsswitch.conf

eg:

passwd:         example files systemd

The name in here must follow the final library name libnss_example.so.2

• Look at the examples for more information