sud • Dyne.org files

# SUD :: Super User Do

This software aims to be a general implementation of a UNIX tool for
privilege escalation, mostly for didactic and frugal purposes. It is
designed to run SUID, with "super-user powers" to execute things as
root on the system it is installed.

It will grant super user access to all users included in at least one system group named as `admin`, `wheel`, `sudo` or `sud`. Simple as that, no password asked.

[![software by Dyne.org](https://files.dyne.org/software_by_dyne.png)](http://www.dyne.org)

## Quick build

Clone the literate submodule: `git submodule update --init`

Install `dub` (the D language compiler)

Build the literate code parser: `make -C literate`

Build sud: `make release`

Other build targets:

```
Usage:
make <target> CC=gcc (or clang)

General
codegen Generate C code from literate file in src/
release Build a dynamically linked release
debug Build a shared binary with debugging symbols
install Install the current build system-wide
clean Clean the build
stamp Generate a SHA512 hash and timestamp for the binary build
release-musl Build a static release with musl
release-rpi Build a static release with cross-pi
release-sign Sign the SHASUMS on the uploaded release
```

## Motivation

This software is a direct response to the sudo tool which has been
adopted by major Linux and BSD distros while augmenting its complexity
and [collecting
vulnerabilities](https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=sudo)
last not least
[CVE-2021-3156](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3156).

With SUD I intend to finally act up and innovate this field of
development considering we have been [relying for 10 years on a tool
that could have been trivially hacked all that
time](https://www.zdnet.com/article/10-years-old-sudo-bug-lets-linux-users-gain-root-level-access/).

## Pros and cons

SUD doesn't covers all use-cases addressed by alternatives, but a few
common situations in which multi-user privilege isolation is a
necessary and sufficient condition to safely operate a local or remote
machine.

Below a short summary of pros (advantages) and cons (disadvantages) over
existing alternatives:

### Pros compared to [sudo](https://www.sudo.ws/repo.html):

- Easier audit thanks to literate development methodology.
- Fewer lines of code, fewer features, fewer dependencies.

### Pros compared to [doas](https://github.com/Duncaen/OpenDoas):

No configuration file, no parsers.

### Pros compared to [sup](https://github.com/parazyd/sup) and [my own bloated sup](https://github.com/dyne/sup):

Runtime configuration based on GID (well, not really an advantage,
more of a different approach for different use-cases).

### Pros compared to all other implementations:

Public domain licensing

### Cons:

- Not heavily tested
- Code may be improved in some places
- Documentation needs more lovance and spell checking

## Methodology

SUD is software written following the
[literate-programming](https://en.wikipedia.org/wiki/Literate_programming)
approach and welcomes reviews and contributions.

Before using SUD you are supposed to [read its annotated source-code](https://sud.dyne.org).

# Downloads

SUD is distributed as a static binary for various platforms on
[files.dyne.org/sud](https://files.dyne.org/sud)

Binaries include [musl-libc](https://musl-libc.org) as a statically
linked component.

To start using sud on a 64bit GNU+Linux machine, simply do:

```
curl https://files.dyne.org/sud/sud-x86-musl > ~/Downloads/sud
```

Or on Apple/OSX:
```
curl https://files.dyne.org/sud/sud-x86-osx > ~/Downloads/sud
```

Or on a RaspberryPI (any version)
```
curl https://files.dyne.org/sud/sud-arm-rpi > ~/Downloads/sud
```

Then to activate it must be in the path and made SUID:
```
sudo install -m 4755 -o root -g 0 ~/Downloads/sud /usr/local/bin/sud
```

Use `vigr` or edit `/etc/group` to make sure your privileged users are in the `admin`, `wheel` or `sudo` groups.

To verify the binary integrity of SUD use `sud -v` and compare the SHA512 to the [hash published here](https://files.dyne.org/sud/SHASUMS.txt) and signed with [my gpg key](https://jaromil.dyne.org/jaromil.pub): it ties the binary to the `sud.c` sourcecode used to build it. Here a shell snippet that does just that:

```
hash=https://files.dyne.org/sud/SHASUMS.txt
echo "Checking sud binary integrity from: $hash\n"
curl -s https://jaromil.dyne.org/jaromil.pub | gpg --import
curl -s $hash | gpg --verify
echo "\nReleases listed:"
curl -s $hash | awk '/sud.c/ {print $0}'
echo "\nYours found at $(which sud):"
sud -v | awk '/sud.c/ {print $0}'
```

## How to build SUD from source

SUD can either be built as a static executable (no dynamic linking of
libraries) or dynamically linked.

Literate programming source-code starts from documentation which is
then used to generate the source-code and a website. In case of SUD
I'm using the [Literate Programming
System](https://github.com/zyedidia/Literate) written in D, which is
included as a submodule in the `literate` sub-folder. To make sure it is ready for use:

1. install `gcc` or another C compiler
2. install `dub` the D package registry and a D compiler
3. make sure the `literate` git submodule is updated
4. make -C literate to build the documentation tool
5. type `make` to build sud
6. type `sudo make install` to install sud with suid

Tead the [Makefile](Makefile) for other supported build targets.

All the above should be possible on any operating system, if you don't
know why is most likely because you don't know well enough the system
you are running. Go find out.

## Work in progress?

This repository is maintained to improve the clarity of code and
eventually its security, would any flaws be found. It will not be
developed further: no new features, eventually less code.

SUD is licensed as Public Domain in the hope to improve the awareness
of how privilege escalation is done. The portability of SUD to any BSD
and POSIX compliant system is a desirable feature and contributions
are welcome.

Contribute via [issues](dyne/sud/issues) or by [sending me a private email](https://jaromil.dyne.org).

I am also considering to write a new software following this effort: a very
secure alternative to sudo that covers some of its core features, plus
adds new features and implements new ideas to grant the security of a
UNIX privilege escalation tool on GNU/Linux and Apple/OSX.

Keep an eye [here](https://github.com/jaromil/suca) in case you are interested.

## License

SUD is designed and written by Denis Roio <Jaromil @ dyne.org>.

SUD redistributes the [parg](https://github.com/jibsen/parg) library by Jørgen Ibsen.

Code reviews were kindly contributed by members of the Veteran Unix Admins and the 2600 Hacker Quarterly online communities.

SUD is Copyright (C) 2021-2022 by the Dyne.org foundation


<a rel="license"
href="https://creativecommons.org/publicdomain/zero/1.0/">
<img src="https://i.creativecommons.org/p/zero/1.0/88x31.png" style="border-style: none;" alt="CC0" />
</a>
 
To the extent possible under law,
<a rel="dct:publisher"
href="https://dyne.org">
Dyne.org foundation</a>
has waived all copyright and related or neighboring rights to
sud.
This work is published from:

The Netherlands.