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\documentclass[12pt]{beamer}
\usetheme{metropolis}
\newenvironment{code}{\ttfamily}{\par}
\title{Where does \textit{your} compiler come from?}
\date{2018-03-13}
\author{Vincent Ambo}
\institute{Norwegian Unix User Group}
\begin{document}
\maketitle
%% Slide 1:
\section{Introduction}
%% Slide 2:
\begin{frame}{Chicken and egg}
Self-hosted compilers are often built using themselves, for example:
\begin{itemize}
\item C-family compilers bootstrap themselves \& each other
\item (Some!) Common Lisp compilers can bootstrap each other
\item \texttt{rustc} bootstraps itself with a previous version
\item ... same for many other languages!
\end{itemize}
\end{frame}
%% Slide 3:
\begin{frame}{Trusting Trust}
\begin{center}
\large{Could this be exploited?}
\end{center}
\end{frame}
%% Slide 4:
\begin{frame}{Short interlude: A quine}
\begin{center}
\begin{code}
((lambda (x) (list x (list 'quote x)))
\newline\vspace*{6mm} '(lambda (x) (list x (list 'quote x))))
\end{code}
\end{center}
\end{frame}
%% Slide 5:
\begin{frame}{Short interlude: Quine Relay}
\begin{center}
\includegraphics[
keepaspectratio=true,
height=\textheight
]{quine-relay.png}
\end{center}
\end{frame}
%% Slide 6:
\begin{frame}{Trusting Trust}
An attack described by Ken Thompson in 1984:
\begin{enumerate}
\item Modify a compiler to detect when it's compiling itself.
\item Let the modification insert \textit{itself} into the new compiler.
\item Add arbitrary attack code to the modification.
\item \textit{Optional!} Remove the attack from the source after compilation.
\end{enumerate}
\end{frame}
%% Slide 7:
\begin{frame}{Damage potential?}
\begin{center}
Let your imagination run wild!
\end{center}
\end{frame}
%% Slide 8:
\section{Countermeasures}
%% Slide 9:
\begin{frame}{Diverse Double-Compiling}
Assume we have:
\begin{itemize}
\item Target language compilers $A$ and $T$
\item The source code of $A$: $ S_{A} $
\end{itemize}
\end{frame}
%% Slide 10:
\begin{frame}{Diverse Double-Compiling}
Apply the first stage (functional equivalence):
\begin{itemize}
\item $ X = A(S_{A})$
\item $ Y = T(S_{A})$
\end{itemize}
Apply the second stage (bit-for-bit equivalence):
\begin{itemize}
\item $ V = X(S_{A})$
\item $ W = Y(S_{A})$
\end{itemize}
Now we have a new problem: Reproducibility!
\end{frame}
%% Slide 11:
\begin{frame}{Reproducibility}
Bit-for-bit equivalent output is hard, for example:
\begin{itemize}
\item Timestamps in output artifacts
\item Non-deterministic linking order in concurrent builds
\item Non-deterministic VM \& memory states in outputs
\item Randomness in builds (sic!)
\end{itemize}
\end{frame}
\begin{frame}{Reproducibility}
\begin{center}
Without reproducibility, we can never trust that any shipped
binary matches the source code!
\end{center}
\end{frame}
%% Slide 12:
\section{(Partial) State of the Union}
\begin{frame}{The Desired State}
\begin{center}
\begin{enumerate}
\item Full-source bootstrap!
\item All packages reproducible!
\end{enumerate}
\end{center}
\end{frame}
%% Slide 13:
\begin{frame}{Bootstrapping Debian}
\begin{itemize}
\item Sparse information on the Debian-wiki
\item Bootstrapping discussions mostly resolve around new architectures
\item GCC is compiled by depending on previous versions of gcc
\end{itemize}
\end{frame}
\begin{frame}{Reproducing Debian}
Debian has a very active effort for reproducible builds:
\begin{itemize}
\item Organised information about reproducibility status
\item Over 90\% reproducibility in Debian package base!
\end{itemize}
\end{frame}
\begin{frame}{Bootstrapping NixOS}
\end{frame}
\section{The future of bootstrapping}
\begin{frame}{MES}
\end{frame}
\begin{frame}{The Nix project(s)}
\end{frame}
\begin{frame}{Other platforms}
\end{frame}
%% Next up: Debian, Fedora, NixOS
%% Next up: Relevant projects: Nix, MES
%% Next up: There's hope, but don't even think about phones ...
\end{document}
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