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\begin{document}

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\mode<presentation>{

\begin{frame}<1>[t]

\frametitle{%

  \begin{tabular}{@ {}c@ {}}

  \\

  \LARGE Access Control and \\[-3mm] 

  \end{tabular}}\bigskip\bigskip\bigskip

  %\begin{center}

  %\includegraphics[scale=1.3]{pics/barrier.jpg}

  %\end{center}

\normalsize

  \begin{center}

  \begin{tabular}{ll}

  Email:  & christian.urban at kcl.ac.uk\\

  Slides: & KEATS (also home work is there)

  \end{tabular}

  \end{center}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\begin{center}

\begin{tabular}[t]{c}

\includegraphics[scale=1.2]{pics/barrier.jpg}\\

\end{tabular}\;\;\;

\onslide<2>{

\begin{tabular}[t]{c}

\includegraphics[scale=0.32]{pics/trainwreck.jpg}\\

today

\end{tabular}

}

\end{center}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{@ {}c@ {}}Smash the Stack for Fun \ldots\end{tabular}}

\begin{itemize}

\begin{flushright}\small

\textcolor{gray}{\url{http://www.kb.cert.org/vuls}}

\end{flushright}

\medskip

\item made popular in an article by Elias Levy\\ (also known as Aleph One):\\

\begin{center}

{\bf ``Smashing The Stack For Fun and Profit''}

\end{center}\medskip

\begin{flushright}

\end{flushright} 

\end{itemize}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}The Problem\end{tabular}}

\begin{itemize}

\item The basic problem is that library routines in C look as follows:

\begin{center}

{\lstset{language=Java}\fontsize{8}{10}\selectfont%

\texttt{\lstinputlisting{../progs/app5.c}}}

\end{center}

\item the resulting problems are often remotely exploitable 

\item can be used to circumvents all access control

(botnets for further attacks)

\end{itemize}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Variants\end{tabular}}

There are many variants:

\begin{itemize}

\item return-to-lib-C attacks

\item heap-smashing attacks\\

\textcolor{gray}{\small(Slammer Worm in 2003 infected 90\% of vulnerable systems within 10 minutes)}\bigskip

\item ``zero-days-attacks'' (new unknown vulnerability)

\end{itemize}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\small

\texttt{my\_float} is printed twice:\bigskip

{\lstset{language=Java}\fontsize{8}{10}\selectfont%

\texttt{\lstinputlisting{../progs/C1.c}}}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\begin{center}

\only<1>{\includegraphics[scale=0.9]{pics/stack1}\;\;}

\only<2>{\includegraphics[scale=0.9]{pics/stack2}\;\;}

\only<3>{\includegraphics[scale=0.9]{pics/stack3}\;\;}

\end{center}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

{\lstset{language=Java}\fontsize{8}{10}\selectfont%

\texttt{\lstinputlisting{../progs/C2.c}}}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\small

A programmer might be careful, but still introduce vulnerabilities:\bigskip

{\lstset{language=Java}\fontsize{8}{10}\selectfont%

\texttt{\lstinputlisting{../progs/C2a.c}}}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Payloads\end{tabular}}

\begin{itemize}

\item the idea is you store some code as part to the buffer

\item you then override the return address to execute this payload\medskip

\item normally you start a root-shell\pause

\item difficulty is to guess the right place where to ``jump''

\end{itemize}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Payloads (2)\end{tabular}}

\begin{itemize}

\item another difficulty is that the code is not allowed to contain \texttt{$\backslash$x00}:

\begin{center}

\texttt{xorl   \%eax, \%eax}

\end{center}

\end{itemize}\bigskip\bigskip

{\lstset{language=Java}\fontsize{8}{10}\selectfont%

\texttt{\lstinputlisting{../progs/app5.c}}}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Format String Vulnerability\end{tabular}}

\small

\texttt{string} is nowhere used:\bigskip

{\lstset{language=Java}\fontsize{8}{10}\selectfont%

\texttt{\lstinputlisting{../progs/C4.c}}}\bigskip

this vulnerability can be used to read out the stack

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Protections against BO Attacks\end{tabular}}

\begin{itemize}

\item use safe library functions

\item ensure stack data is not executable (can be defeated)

\item address space randomisation (makes one-size-fits-all more difficult)

\item choice of programming language (one of the selling points of Java)

\end{itemize}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Security Goals\end{tabular}}

\begin{itemize}

\item Prevent common vulnerabilities from occurring (e.g. buffer overflows)\pause

\item Recover from attacks (traceability and auditing of security-relevant actions)\pause

\item Monitoring (detect attacks)\pause

\item Privacy, confidentiality, anonymity (to protect secrets)\pause

\item Authenticity (needed for access control)\pause

\item Integrity (prevent unwanted modification or tampering)\pause

\item Availability and reliability (reduce the risk of DoS attacks)

\end{itemize}

\end{frame}}

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\mode<presentation>{

\begin{frame}[c]

\frametitle{\begin{tabular}{c}Homework\end{tabular}}

\begin{itemize}

\item Assume format string attacks allow you to read out the stack. What can you do

	with this information?\bigskip

\item Assume you can crash a program remotely. Why is this a problem?

\end{itemize}

\end{frame}}

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\end{document}

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