hammer/docs/hammer-presentation.tex
2012-08-28 13:29:24 -04:00

388 lines
16 KiB
TeX

\documentclass{beamer}
\usetheme[secheader]{Boadilla}
\usecolortheme{seahorse}
\setbeamertemplate{footline}{https://github.com/UpstandingHackers/hammer}
\title{Hammer: Smashing Binary Formats Into Bits}
\author{mlp and tq}
\date{July 27, 2012}
\institute[2012]{Upstanding Hackers}
\usepackage{fancyvrb}
\usepackage{color}
\usepackage[utf8]{inputenc}
\makeatletter
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\def\PYZbs{\char`\\}
\def\PYZus{\char`\_}
\def\PYZob{\char`\{}
\def\PYZcb{\char`\}}
\def\PYZca{\char`\^}
\def\PYZsh{\char`\#}
\def\PYZpc{\char`\%}
\def\PYZdl{\char`\$}
\def\PYZti{\char`\~}
% for compatibility with earlier versions
\def\PYZat{@}
\def\PYZlb{[}
\def\PYZrb{]}
\makeatother
\begin{document}
\frame{\titlepage}
\section[Outline]{}
\frame{\tableofcontents}
\section{Introduction}
\frame{
\frametitle{The recursive-descent family}
\begin{itemize}
\item<1-> Recursive descent parsers
\begin{itemize}
\item Parsing like mom used to do it (if your mom is Jack Crenshaw)
\item Conceptually really simple
\item Can't do left recursion
\item Can have exponential runtime
\end{itemize}
\item<2-> Parsing expression grammars
\begin{itemize}
\item Look a lot like CFGs
\item Always deterministic (unambiguous)
\item Provide lookahead
\item Still can't do left recursion
\end{itemize}
\item<3-> Packrat parsers
\begin{itemize}
\item They're PEGs, but memoized
\item Can handle left-recursion!
\end{itemize}
\end{itemize}
}
\section{Binary Parsing}
\frame{
\frametitle{Why binary parsing?}
\begin{itemize}
\item<1-> None of the existing tools do it well
\begin{itemize}
\item Limited to character streams
\item Endianness is a pain in the dick
\item So are bit-fields
\end{itemize}
\item<2-> Except bison, which nobody likes
\begin{itemize}
\item Interface sucks for everything except parsers/interpreters
\item Shift-reduce conflicts are confusing
\item Bit-fields still hard unless everything's nicely byte-aligned
\end{itemize}
\end{itemize}
}
\frame{
\frametitle{Requirements}
\begin{itemize}
\item Thread-safe and reentrant
\item Simple API
\item Fast
\item Correct
\end{itemize}
}
\section{Parser combinators}
\frame{
\frametitle{Naming conventions}
\begin{itemize}
\item<1-> Types
\begin{itemize}
\item Start with \textbf{H} and are CamelCased
\item \texttt{HParser}, \texttt{HParsedToken}, etc
\end{itemize}
\item<2-> Functions
\begin{itemize}
\item Start with \textbf{h\_} and use underscores
\item \texttt{h\_parse()}, \texttt{h\_length\_value()}, etc
\end{itemize}
\end{itemize}
}
\begin{frame}[fragile]
\frametitle{Basic usage}
\begin{Verbatim}[commandchars=\\\{\}]
\PY{c+cp}{\PYZsh{}}\PY{c+cp}{include "hammer.h"}
\PY{k}{const} \PY{n}{HParsedToken}\PY{o}{*} \PY{n+nf}{build\PYZus{}my\PYZus{}struct}\PY{p}{(}\PY{k}{const} \PY{n}{HParseResult} \PY{o}{*}\PY{n}{p}\PY{p}{)} \PY{p}{\PYZob{}}
\PY{c+c1}{// ...}
\PY{p}{\PYZcb{}}
\PY{k+kt}{int} \PY{n+nf}{main}\PY{p}{(}\PY{k+kt}{int} \PY{n}{argc}\PY{p}{,} \PY{k+kt}{char}\PY{o}{*}\PY{o}{*} \PY{n}{argv}\PY{p}{)} \PY{p}{\PYZob{}}
\PY{c+c1}{// obtain data, and its length, from somewhere}
\PY{c+c1}{// Create a parser}
\PY{n}{HParser} \PY{o}{*}\PY{n}{parser} \PY{o}{=} \PY{n}{action}\PY{p}{(}\PY{p}{.}\PY{p}{.}\PY{p}{.}\PY{p}{,}
\PY{n}{build\PYZus{}my\PYZus{}struct}\PY{p}{)}\PY{p}{;}
\PY{c+c1}{// Parse the data}
\PY{n}{HParseResult} \PY{o}{*}\PY{n}{result} \PY{o}{=} \PY{n}{h\PYZus{}parse}\PY{p}{(}\PY{n}{parser}\PY{p}{,} \PY{n}{data}\PY{p}{,} \PY{n}{length}\PY{p}{)}\PY{p}{;}
\PY{c+c1}{// Get your struct back from the result token and use it}
\PY{n}{do\PYZus{}something}\PY{p}{(}\PY{n}{result}\PY{o}{-}\PY{o}{>}\PY{n}{ast}\PY{o}{-}\PY{o}{>}\PY{n}{user}\PY{p}{)}\PY{p}{;}
\PY{k}{return} \PY{l+m+mi}{0}\PY{p}{;}
\PY{p}{\PYZcb{}}
\end{Verbatim}
\end{frame}
\begin{frame}[fragile]
\frametitle{Result types}
\begin{itemize}
\item<1-> HParseResult
\begin{itemize}
\item A tree of parsed tokens
\item The total number of bits parsed
\item A reference to the memory context for this parse
\end{itemize}
\item<2-> HParsedToken
\begin{itemize}
\item Token type: bytes, signed/unsigned int, sequence, user-defined
\item Token (a tagged union)
\item Byte index and bit offset
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Primitives}
\begin{itemize}
\item<1-> Character and token parsers
\begin{itemize}
\item \texttt{h\_ch(const uint8\_t c)}, \\ \texttt{h\_token(const uint8\_t *str, size\_t len)}
\item \texttt{h\_ch\_range(const uint8\_t lower, const uint8\_t upper)}
\item \texttt{h\_not\_in(const uint8\_t charset, size\_t length)}
\end{itemize}
\item<2-> Integral parsers
\begin{itemize}
\item \texttt{h\_uint8()}, \texttt{h\_int64()}
\item \texttt{h\_bits(size\_t len, bool sign)}
\item \texttt{h\_int\_range(const HParser *p, const int64\_t lower, const int64\_t upper)}
\end{itemize}
\item<3-> End-of-input
\begin{itemize}
\item \texttt{h\_end\_p()}
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Combining primitives}
\begin{itemize}
\item<1-> Sequential and alternative
\begin{itemize}
\item \texttt{h\_sequence(const HParser *p, ...)}
\item \texttt{h\_choice(const HParser *p, ...)}
\end{itemize}
\item<2-> Repetition
\begin{itemize}
\item \texttt{h\_many(const HParser *p)}
\item \texttt{h\_many1(const HParser *p)}
\item \texttt{h\_repeat\_n(const HParser *p, size\_t len)}
\end{itemize}
\item<3-> Optional
\begin{itemize}
\item \texttt{h\_optional(const HParser *p)}
\end{itemize}
\item<4-> Not Actually Appearing In This Parse Tree
\begin{itemize}
\item \texttt{h\_ignore(const HParser *p)}
\end{itemize}
\item<5-> Higher-order
\begin{itemize}
\item \texttt{h\_length\_value(const HParser *length, const HParser *value)}
\item \texttt{h\_and(const HParser *p)}, \texttt{h\_not(const HParser *p)}
\item \texttt{h\_indirect(const HParser *p)}
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Doing things to combinations of primitives}
\begin{itemize}
\item<1-> \texttt{h\_attr\_bool(const HParser *p, const HPredicate pred)}
\item<2-> \texttt{h\_action(const HParser *p, const HAction a)}
\end{itemize}
\end{frame}
\section{A practical example}
\begin{frame}[fragile]
\frametitle{Top-level DNS}
\begin{Verbatim}[commandchars=\\\{\}]
\PY{k}{const} \PY{n}{HParser} \PY{o}{*}\PY{n}{dns\PYZus{}message} \PY{o}{=}
\PY{n}{h\PYZus{}action}\PY{p}{(}\PY{n}{h\PYZus{}attr\PYZus{}bool}\PY{p}{(}\PY{n}{h\PYZus{}sequence}\PY{p}{(}\PY{n}{dns\PYZus{}header}\PY{p}{,}
\PY{n}{h\PYZus{}many}\PY{p}{(}\PY{n}{dns\PYZus{}question}\PY{p}{)}\PY{p}{,}
\PY{n}{h\PYZus{}many}\PY{p}{(}\PY{n}{dns\PYZus{}rr}\PY{p}{)}\PY{p}{,}
\PY{n}{h\PYZus{}end\PYZus{}p}\PY{p}{(}\PY{p}{)}\PY{p}{,}
\PY{n+nb}{NULL}\PY{p}{)}\PY{p}{,}
\PY{n}{validate\PYZus{}dns}\PY{p}{)}\PY{p}{,}
\PY{n}{pack\PYZus{}dns\PYZus{}struct}\PY{p}{)}\PY{p}{;}
\end{Verbatim}
\end{frame}
\begin{frame}[fragile]
\frametitle{DNS Questions}
\begin{Verbatim}[commandchars=\\\{\}]
\PY{k}{const} \PY{n}{HParser} \PY{o}{*}\PY{n}{dns\PYZus{}question} \PY{o}{=}
\PY{n}{h\PYZus{}sequence}\PY{p}{(}\PY{n}{h\PYZus{}sequence}\PY{p}{(}\PY{n}{h\PYZus{}many1}\PY{p}{(}\PY{n}{h\PYZus{}length\PYZus{}value}\PY{p}{(}\PY{n}{h\PYZus{}int\PYZus{}range}\PY{p}{(}
\PY{n}{h\PYZus{}uint8}\PY{p}{(}\PY{p}{)}\PY{p}{,}
\PY{l+m+mi}{1}\PY{p}{,}
\PY{l+m+mi}{255}\PY{p}{)}\PY{p}{,}
\PY{n}{h\PYZus{}uint8}\PY{p}{(}\PY{p}{)}\PY{p}{)}\PY{p}{)}\PY{p}{,}
\PY{n}{h\PYZus{}ch}\PY{p}{(}\PY{l+s+sc}{'\PYZbs{}x00'}\PY{p}{)}\PY{p}{,}
\PY{n+nb}{NULL}\PY{p}{)}\PY{p}{,} \PY{c+c1}{// QNAME}
\PY{n}{qtype}\PY{p}{,} \PY{c+c1}{// QTYPE}
\PY{n}{qclass}\PY{p}{,} \PY{c+c1}{// QCLASS}
\PY{n+nb}{NULL}\PY{p}{)}\PY{p}{;}
\end{Verbatim}
\end{frame}
\begin{frame}[fragile]
\frametitle{DNS RRs}
\begin{Verbatim}[commandchars=\\\{\}]
\PY{k}{const} \PY{n}{HParser} \PY{o}{*}\PY{n}{dns\PYZus{}rr} \PY{o}{=}
\PY{n}{h\PYZus{}sequence}\PY{p}{(}\PY{n}{domain}\PY{p}{,} \PY{c+c1}{// NAME}
\PY{n}{type}\PY{p}{,} \PY{c+c1}{// TYPE}
\PY{n}{class}\PY{p}{,} \PY{c+c1}{// CLASS}
\PY{n}{h\PYZus{}uint32}\PY{p}{(}\PY{p}{)}\PY{p}{,} \PY{c+c1}{// TTL}
\PY{c+c1}{// RDLENGTH+RDATA}
\PY{n}{h\PYZus{}length\PYZus{}value}\PY{p}{(}\PY{n}{h\PYZus{}uint16}\PY{p}{(}\PY{p}{)}\PY{p}{,} \PY{n}{h\PYZus{}uint8}\PY{p}{(}\PY{p}{)}\PY{p}{)}\PY{p}{,}
\PY{n+nb}{NULL}\PY{p}{)}\PY{p}{;}
\end{Verbatim}
\end{frame}
\begin{frame}[fragile]
\frametitle{Validating a DNS packet}
\begin{Verbatim}[commandchars=\\\{\}]
\PY{n}{bool} \PY{n+nf}{validate\PYZus{}dns}\PY{p}{(}\PY{n}{HParseResult} \PY{o}{*}\PY{n}{p}\PY{p}{)} \PY{p}{\PYZob{}}
\PY{k}{if} \PY{p}{(}\PY{n}{TT\PYZus{}SEQUENCE} \PY{o}{!}\PY{o}{=} \PY{n}{p}\PY{o}{-}\PY{o}{>}\PY{n}{ast}\PY{o}{-}\PY{o}{>}\PY{n}{token\PYZus{}type}\PY{p}{)}
\PY{k}{return} \PY{n+nb}{false}\PY{p}{;}
\PY{n}{HParsedToken} \PY{o}{*}\PY{o}{*}\PY{n}{elems} \PY{o}{=} \PY{n}{p}\PY{o}{-}\PY{o}{>}\PY{n}{ast}\PY{o}{-}\PY{o}{>}\PY{n}{seq}\PY{o}{-}\PY{o}{>}\PY{n}{elements}\PY{p}{[}\PY{l+m+mi}{0}\PY{p}{]}\PY{o}{-}\PY{o}{>}\PY{n}{seq}\PY{o}{-}\PY{o}{>}
\PY{n}{elements}\PY{p}{;}
\PY{k+kt}{size\PYZus{}t} \PY{n}{qd} \PY{o}{=} \PY{n}{elems}\PY{p}{[}\PY{l+m+mi}{8}\PY{p}{]}\PY{o}{-}\PY{o}{>}\PY{n}{uint}\PY{p}{;}
\PY{k+kt}{size\PYZus{}t} \PY{n}{an} \PY{o}{=} \PY{n}{elems}\PY{p}{[}\PY{l+m+mi}{9}\PY{p}{]}\PY{o}{-}\PY{o}{>}\PY{n}{uint}\PY{p}{;}
\PY{k+kt}{size\PYZus{}t} \PY{n}{ns} \PY{o}{=} \PY{n}{elems}\PY{p}{[}\PY{l+m+mi}{10}\PY{p}{]}\PY{o}{-}\PY{o}{>}\PY{n}{uint}\PY{p}{;}
\PY{k+kt}{size\PYZus{}t} \PY{n}{ar} \PY{o}{=} \PY{n}{elems}\PY{p}{[}\PY{l+m+mi}{11}\PY{p}{]}\PY{o}{-}\PY{o}{>}\PY{n}{uint}\PY{p}{;}
\PY{n}{HParsedToken} \PY{o}{*}\PY{n}{questions} \PY{o}{=} \PY{n}{p}\PY{o}{-}\PY{o}{>}\PY{n}{ast}\PY{o}{-}\PY{o}{>}\PY{n}{seq}\PY{o}{-}\PY{o}{>}\PY{n}{elements}\PY{p}{[}\PY{l+m+mi}{1}\PY{p}{]}\PY{p}{;}
\PY{k}{if} \PY{p}{(}\PY{n}{questions}\PY{o}{-}\PY{o}{>}\PY{n}{seq}\PY{o}{-}\PY{o}{>}\PY{n}{used} \PY{o}{!}\PY{o}{=} \PY{n}{qd}\PY{p}{)}
\PY{k}{return} \PY{n+nb}{false}\PY{p}{;}
\PY{n}{HParsedToken} \PY{o}{*}\PY{n}{rrs} \PY{o}{=} \PY{n}{p}\PY{o}{-}\PY{o}{>}\PY{n}{ast}\PY{o}{-}\PY{o}{>}\PY{n}{seq}\PY{o}{-}\PY{o}{>}\PY{n}{elements}\PY{p}{[}\PY{l+m+mi}{2}\PY{p}{]}\PY{p}{;}
\PY{k}{if} \PY{p}{(}\PY{n}{an}\PY{o}{+}\PY{n}{ns}\PY{o}{+}\PY{n}{ar} \PY{o}{!}\PY{o}{=} \PY{n}{rrs}\PY{o}{-}\PY{o}{>}\PY{n}{seq}\PY{o}{-}\PY{o}{>}\PY{n}{used}\PY{p}{)}
\PY{k}{return} \PY{n+nb}{false}\PY{p}{;}
\PY{k}{return} \PY{n+nb}{true}\PY{p}{;}
\PY{p}{\PYZcb{}}
\end{Verbatim}
\end{frame}
\section{Future work}
\begin{frame}[fragile]
\frametitle{What's next?}
\begin{itemize}
\item More parsing backends
\begin{itemize}
\item LL(k)
\item GLR
\item LALR(8)
\item Derivatives
\end{itemize}
\item Benchmarking :)
\item Bindings for python, ruby, (your preferred language here)
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{More to come!}
\begin{itemize}
\item Watch langsec-discuss@lists.langsec.org for further announcements
\item https://github.com/UpstandingHackers/hammer
\end{itemize}
\end{frame}
\end{document}