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     7 \usepackage{ifthen}

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     7 

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    10 

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    27 

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    40 	showstringspaces=false}

    41 

    42 \lstdefinelanguage{scala}{

    43   morekeywords={abstract,case,catch,class,def,%

    44     do,else,extends,false,final,finally,%

    45     for,if,implicit,import,match,mixin,%

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    58 

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    74 \renewcommand{\slidecaption}{APP 03, King's College London, 22 October 2014}

    14 \renewcommand{\slidecaption}{APP 04, King's College London}

    75 \makeatletter

    15 \newcommand{\bl}[1]{\textcolor{blue}{#1}}  

    76 \def\verbatim@font{\consolas\footnotesize}

    77 \makeatother

    82 \mode<presentation>{

    20 \begin{frame}[t]

    83 \begin{frame}<1>[t]

   100 

    37 \end{frame}

   101 \end{frame}}

    38 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   102  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

    39 

   103 

    40 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   104 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    41 \begin{frame}[c]

   105 \mode<presentation>{

    42 

   106 \begin{frame}[c]

    43 \begin{center}

   107 

    44 \includegraphics[scale=0.45]{../pics/trainwreck.jpg}\\

   108 \begin{center}

    45 last week: buffer overflow attacks

   109 \includegraphics[scale=0.45]{pics/trainwreck.jpg}\\

    46 \end{center}

   110 two weeks ago: buffer overflow attacks

   111 \end{center}

   112 

   114 \end{frame}}

    48 \end{frame}

   119 \frametitle{D-Link Router, Buffer Overflows}

    53 \frametitle{D-Link Wifi Router, BOA}

   120 

    54 \small

   121 \begin{verbatim}

    55 

   127  curl http://<target ip>/post_login.xml?hash=AAA...AAABBBB

    61 \begin{center}\footnotesize 

    62 \pcode{curl http://<target ip>/post_login.xml?hash=AAA...AAABBBB}

    63 \end{center}

   130 292 occurrences of the 'A' character, followed by four 

    66 292 occurrences of the \pcode{'A'} character, followed by four 

   131 occurrences of character 'B'. In our lab setup, characters 

    67 occurrences of character \pcode{'B'}. In our lab setup, characters 

   132 'B' overwrite the saved program counter (%ra).

    68 \pcode{'B'} overwrite the saved program counter (\pcode{\%ra}).\bigskip

   133 

    69 

   134 Discovery date: 06/03/2013

    70 

   135 Release date:   02/08/2013

    71 \begin{tabular}{@{}ll}

   136 \end{verbatim}

    72 Discovery date: & 06/03/2013\\

   137 

    73 Release date:   & 02/08/2013

   138 \mbox{}\footnotesize\hfill\url{http://pastebin.com/vbiG42VD}  

    74 \end{tabular}

   139 \end{frame}

    75 

   140 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

    76 

   141 

    77 

   142 

    78 \hfill\url{http://roberto.greyhats.it/advisories/20130801-dlink-dir645.txt} 

    79 \end{frame}

    80 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   146 \frametitle{Backdoors}

    84 \frametitle{D-Link Backdoors}

   157 \begin{verbatim}

    96 \begin{center}

   158 xmlset_roodkcableoj28840ybtide

    97 \pcode{xmlset_roodkcableoj28840ybtide}

   159 \end{verbatim}

    98 \end{center}

   160 

    99 \end{quote}\bigskip\bigskip

   163 \hfill\tiny\url{http://www.devttys0.com/2013/10/reverse-engineering-a-d-link-backdoor/}

   102 \hfill\footnotesize\url{http://www.devttys0.com/2013/10/reverse-engineering-a-d-link-backdoor/}

   164   

   103 

   165 \end{frame}

   104 \end{frame}

   166 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   105 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   167 

   106 

   168 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   107 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   169 \mode<presentation>{

   108 \begin{frame}[fragile]

   109 

   110 CVE-2014-0476 chkrootkit vulnerability 4 Jun'14\medskip

   111 

   112 \begin{quote}\rm\small

   113 Hi,

   114 

   115 we just found a serious vulnerability in the chkrootkit package, which

   116 may allow local attackers to gain root access to a box in certain

   117 configurations (\pcode{/tmp} not mounted noexec). Steps to reproduce:

   118 

   119 \begin{itemize}

   120 \item Put an executable file named \pcode{update} with non-root owner in /tmp (not

   121 mounted noexec, obviously)

   122 \item Run chkrootkit (as uid 0)

   123 \end{itemize}

   124 

   125 Result: The file \pcode{/tmp/update} will be executed as root, thus effectively

   126 rooting your box, if malicious content is placed inside the file.

   127 

   128 If an attacker knows you are periodically running chkrootkit (like in

   129 cron.daily) and has write access to \pcode{/tmp} (not mounted noexec), he may

   130 easily take advantage of this.

   131 \end{quote}

   132 \mbox{}\\[-10mm]

   133 

   134 \hfill\footnotesize\url{http://seclists.org/oss-sec/2014/q2/430}

   135 

   136 \end{frame}

   137 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   138 

   139 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   179 \begin{tikzpicture}

   149 \begin{bubble}[8cm]

   180 \draw (0,0) node[inner sep=2mm,fill=cream, ultra thick, draw=red, rounded corners=2mm] 

   181 {\begin{minipage}{8cm}

   183 programs should only have as much privilege as they need 

   151 users and programs should only have as much privilege as they need 

   184 \end{minipage}};

   152 \end{bubble}

   185 \end{tikzpicture}

   153 \end{itemize}

   186 \end{itemize}

   154 

   187 

   155 \end{frame}

   188 \end{frame}}

   196 \begin{itemize}

   163 

   197 \item the idea is to restrict access to files and therefore lower the consequences of an attack\\[1cm]\mbox{}

   164 \begin{itemize}

   198 \end{itemize}

   165 \item privileges are specified by file access permissions (``everything is a file'')\medskip 

   199 

   166 \item there are 9 (plus 2) bits that specify the permissions of a file

   200 \begin{textblock}{1}(2.5,9.5)

   167 

   201   \begin{tikzpicture}[scale=1]

   168 \begin{center}

   202   

   169 \begin{tabular}{l}

   203   \draw[line width=1mm] (-.3, 0) rectangle (1.5,2);

   170 \texttt{\$ ls -la}\\

   204   \draw (4.7,1) node {Internet};

   171 \texttt{-rwxrw-r-{}- \hspace{3mm} foo\_file.txt}

   205   \draw (0.6,1.7) node {\footnotesize Interface};

   172 \end{tabular}

   206   \draw (0.6,-0.4) node {\footnotesize \begin{tabular}{c}unprivileged\\[-1mm] process\end{tabular}};

   173 \end{center}

   207   \draw (-2.7,-0.4) node {\footnotesize \begin{tabular}{c}privileged\\[-1mm] process\end{tabular}};

   174 \end{itemize}

   208   

   175 

   209   \draw[line width=1mm] (-1.8, 0) rectangle (-3.6,2);

   176 \end{frame}}

   210 

   177 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   211   \draw[white] (1.7,1) node (X) {};

   178 

   212   \draw[white] (3.7,1) node (Y) {};

   179 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   213   \draw[red, <->, line width = 2mm] (X) -- (Y);

   180 \begin{frame}[c]

   214  

   181 \frametitle{Login Process}

   215   \draw[red, <->, line width = 1mm] (-0.6,1) -- (-1.6,1);

   182 

   216   \end{tikzpicture}

   183 

   217 \end{textblock}

   184 \begin{itemize}

   218 

   185 \item login processes run under UID $=$ \pcode{0}\medskip 

   219 \end{frame}}

   186 \begin{center}

   220 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   187 \texttt{ps -axl | grep login}

   221 \newcommand{\bl}[1]{\textcolor{blue}{#1}}  

   188 \end{center}\medskip

   189 

   190 \item after login, shells run under UID $=$ user (e.g.~501)\medskip

   191 \begin{center}

   192 \texttt{id cu}

   193 \end{center}\medskip\pause

   194 

   195 \item non-root users are not allowed to change the UID --- would break 

   196 access control

   197 \item but needed for example for \texttt{passwd}

   198 \end{itemize}

   199 

   200 \end{frame}

   201 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   202 

   203 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   204 \begin{frame}[c]

   205 \frametitle{Setuid and Setgid}

   206 

   207 The solution is that Unix file permissions are 9 + \underline{2 Bits}:

   208 \alert{Setuid} and \alert{Setgid} Bits

   209 

   210 \begin{itemize}

   211 \item When a file with setuid is executed, the resulting process will

   212   assume the UID given to the owner of the file.

   213 \item This enables users to create processes as root (or another

   214   user).\bigskip

   215 

   216 \item Essential for changing passwords, for example.

   217 \end{itemize}

   218 

   219 \begin{center}

   220 \texttt{chmod 4755 fobar\_file}

   221 \end{center}

   222 

   223 \end{frame}

   224 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

   262 

   267 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   263 

   268 \begin{frame}[c]

   264 

   269 \frametitle{\Large Discretionary Access Control}

   265 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   266 \mode<presentation>{

   267 \begin{frame}[c]

   268 \frametitle{Discretionary Access Control}

   284 \end{frame}}

   284 \end{frame}

   285 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   286 

   287 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   288 \begin{frame}[c]

   289 \small

   290 

   291 \lstinputlisting[numbers=none,xleftmargin=-6mm]{lst}

   292 

   293 

   294 \begin{center}

   295 \begin{tabular}{ll}

   296 Members of group staff: & ping, bob, emma\\ 

   297 Members of group students: & emma\\

   298 \end{tabular}

   299 \end{center}

   300 

   301 \begin{center}

   302 \begin{tabular}{@{\hspace{-7mm}}r|c|c|c|c|c@{}}

   303         & manual.txt & report.txt & microedit & src/code.c & src/code.h \\\hline

   304 ping & & & & &\\\hline

   305 bob & & & & &\\\hline

   306 emma   & & & & &\\

   307 \end{tabular}

   308 \end{center}

   309 

   310 \end{frame}

   290 

   316 \small

   291 \begin{itemize}

   317 

   292 \item Restrictions to allowed information flows are not decided at the user’s 

   318 \begin{itemize}

   293 discretion (as with Unix chmod), but instead enforced by system policies.

   319 \item Restrictions to allowed information flows are not decided at the

   294 

   320   user's discretion (as with Unix \pcode{chmod}), but instead enforced

   295 \item Mandatory access control mechanisms are aimed in particular at 

   321   by system policies.

   296 preventing policy violations by untrusted application software, which 

   322 

   297 typically have at least the same access privileges as the invoking user.\medskip

   323 \item Mandatory access control mechanisms are aimed in particular at

   298 

   324   preventing policy violations by untrusted application software,

   299 Simple example: Air Gap Security.

   325   which typically have at least the same access privileges as the

   300 Uses completely separate network and computer hardware for different application classes.

   326   invoking user.\medskip

   327 

   328 Simple example: Air Gap Security. Uses completely separate network

   329 and computer hardware for different application classes.

   312 \item Formal policy model for mandatory access control in a military multi-level security environment.

   341 \item Formal policy model for mandatory access control in a military

   313 All subjects (processes, users, terminals) and data objects (files, directories, windows, connections) are labeled with a confidentiality level, e.g. 

   342   multi-level security environment. All subjects (processes, users,

   314 \begin{center}

   343   terminals, files, windows, connections) are labeled

   315 unclassified < confidential < secret < top secret.

   344   with a confidentiality level, e.g.

   316 \end{center}

   345 \begin{center}

   317 

   346 unclassified < confidential < secret < top secret

   318 \item 

   347 \end{center}\medskip

   319 The system policy automatically prevents the flow of information from high-level objects to lower levels. A process that reads top secret data becomes tagged as top secret by the operating system, as will be all files into which it writes afterwards. 

   348 

   320 %Each user has a maximum allowed confidentiality level specified and cannot receive data beyond that level. A selected set of trusted subjects is allowed to bypass the restrictions, in order to permit the declassification of information.

   349 \item The system policy automatically prevents the flow of information

   321 \end{itemize}

   350   from high-level objects to lower levels. A process that reads top

   322 

   351   secret data becomes tagged as top secret by the operating system, as

   323 \end{frame}

   352   will be all files into which it writes afterwards.

   324 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   353 %Each user has a maximum allowed confidentiality level specified and

   325 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   354 %cannot receive data beyond that level. A selected set of trusted

   326   \mode<presentation>{

   355 %subjects is allowed to bypass the restrictions, in order to permit

   356 %the declassification of information.

   357 \end{itemize}

   358 

   359 \end{frame}

   360 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   361 

   362 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   345   \end{frame}}

   381   \end{frame}

   346   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   382 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   347 %

   383 

   348 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   384 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   349   \mode<presentation>{

   353   \begin{tikzpicture}

   388   \begin{bubble}[10cm]

   354   \draw (0,0) node[inner sep=2mm,fill=cream, ultra thick, draw=red, rounded corners=2mm] 

   355   {\normalsize\color{darkgray}

   356   \begin{minipage}{10cm}\raggedright

   358   \end{minipage}};

   390   \end{bubble}\bigskip\bigskip

   359   \end{tikzpicture}\bigskip\bigskip

   367   \end{frame}}

   398   \end{frame}

   368   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   399 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   369 %

   400 

   370 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   401 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   371   \mode<presentation>{

   389   \end{frame}}

   419   \end{frame}

   390   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   420 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   391 %

   421 

   392 

   422 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   393 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   423 \begin{frame}[c]

   394 \mode<presentation>{

   424 \frametitle{Security Levels (2)}

   395 \begin{frame}[c]

   425 

   396 \frametitle{\begin{tabular}{@ {}c@ {}}Security Levels (2)\end{tabular}}

   426 \begin{itemize}

   397 

   427 \item Bell-La Padula preserves data secrecy, but not data

   398 \begin{itemize}

   428   integrity\bigskip\pause

   399 \item Bell --- La Padula preserves data secrecy, but not data integrity\bigskip\pause

   409 \end{frame}}

   438 \end{frame}

   410 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   439 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   411 

   440 

   412 

   441 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   413 

   414 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   415 \mode<presentation>{

   420 \includegraphics[scale=0.7]{pics/pointsplane.jpg}

   446 \includegraphics[scale=0.7]{../pics/pointsplane.jpg}

   434 \end{frame}}

   460 \end{frame}

   435 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   461 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   436 

   462 

   437 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   463 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   438 \mode<presentation>{

   464 \begin{frame}[c]

   439 \begin{frame}[c]

   465 \frametitle{\Large Lessons from Access Control}

   440 \frametitle{Lessons from Access Control}

   447 	\textcolor{gray}{you invite situations like\ldots let's be root}\bigskip

   472 	\textcolor{gray}{you invite situations like\ldots lets be root}\bigskip

   448 

   473 

   449 \item you can still abuse the system\ldots

   474 \item you can still abuse the system\ldots\bigskip\pause

   450 

   475 

   451 \end{itemize}

   476 \item 

   452 

   477   policies (a finite system)\\

   453 \end{frame}}

   478   computer system (infinite)\medskip\\

   454 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   479 Q: Does your policy ensure that a tainted file cannot affect your

   455 

   480 core system files?

   456  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   481 

   457   \mode<presentation>{

   482 \end{itemize}

   483 

   484 \end{frame}

   485 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   486 

   487 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   477   \end{frame}}

   507   \end{frame}

   478   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   508 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   480 

   510 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   481 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   511 \begin{frame}[c]

   482 \mode<presentation>{

   512 \frametitle{\Large Cryptographic Protocol Failures}

   483 \begin{frame}[c]

   513 

   484 \frametitle{A mutual authentication protocol}

   514 Ross Anderson and Roger Needham wrote:\bigskip

   515 

   516 \begin{quote}\rm

   517 \alert{A lot of the recorded frauds were the result of this kind of

   518   blunder, or from management negligence pure and simple.} However,

   519 there have been a significant number of cases where the designers

   520 protected the right things, used cryptographic algorithms which were

   521 not broken, and yet found that their systems were still successfully

   522 attacked.

   523 \end{quote}

   524 

   525 \end{frame}

   526 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

   527 

   528 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   529   \begin{frame}<1-3>[c]

   530   \frametitle{Oyster Cards}

   531 

   532   \includegraphics[scale=0.4]{../pics/oysterc.jpg}

   533 

   534   \begin{itemize}

   535   \item good example of a bad protocol\\ (security by obscurity)\bigskip

   536   \item<3->  ``Breaching security on Oyster cards should not 

   537   allow unauthorised use for more than a day, as TfL promises to turn 

   538   off any cloned cards within 24 hours\ldots''

   539   \end{itemize}

   540 

   541   \only<2>{

   542   \begin{textblock}{12}(0.5,0.5)

   543   \begin{bubble}[11cm]\footnotesize

   544   {\bf Wirelessly Pickpocketing a Mifare Classic Card}\medskip

   545 

   546   The Mifare Classic is the most widely used contactless smartcard on the

   547   market. The stream cipher CRYPTO1 used by the Classic has recently been

   548   reverse engineered and serious attacks have been proposed. The most serious

   549   of them retrieves a secret key in under a second. In order to clone a card,

   550   previously proposed attacks require that the adversary either has access to

   551   an eavesdropped communication session or executes a message-by-message

   552   man-in-the-middle attack between the victim and a legitimate

   553   reader. Although this is already disastrous from a cryptographic point of

   554   view, system integrators maintain that these attacks cannot be performed

   555   undetected.\smallskip

   556 

   557   This paper proposes four attacks that can be executed by an adversary having

   558   only wireless access to just a card (and not to a legitimate reader). The

   559   most serious of them recovers a secret key in less than a second on ordinary

   560   hardware. Besides the cryptographic weaknesses, we exploit other weaknesses

   561   in the protocol stack. A vulnerability in the computation of parity bits

   562   allows an adversary to establish a side channel. Another vulnerability

   563   regarding nested authentications provides enough plaintext for a speedy

   564   known-plaintext attack.\hfill{}(a paper from 2009)

   565   \end{bubble}

   566   \end{textblock}}

   567 

   568   \end{frame}

   569 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   570 

   571 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   572 \begin{frame}<1->[t]

   573 \frametitle{Another Example}

   574 

   575 In an email from Ross Anderson\bigskip\small	

   576 

   577 \begin{tabular}{l}

   578 From: Ross Anderson <Ross.Anderson@cl.cam.ac.uk>\\

   579 Sender: cl-security-research-bounces@lists.cam.ac.uk\\

   580 To: cl-security-research@lists.cam.ac.uk\\

   581 Subject: Birmingham case\\

   582 Date: Tue, 13 Aug 2013 15:13:17 +0100\\

   583 \end{tabular}

   584 

   585 

   586 \only<2>{

   587 \begin{textblock}{12}(0.5,0.8)

   588 \begin{bubble}[11cm]

   589 \footnotesize

   590 As you may know, Volkswagen got an injunction against the University of

   591 Birmingham suppressing the publication of the design of a weak cipher

   592 used in the remote key entry systems in its recent-model cars. The paper

   593 is being given today at Usenix, minus the cipher design.\medskip

   594 

   595 I've been contacted by Birmingham University's lawyers who seek to prove

   596 that the cipher can be easily obtained anyway. They are looking for a

   597 student who will download the firmware from any newish VW, disassemble

   598 it and look for the cipher. They'd prefer this to be done by a student

   599 rather than by a professor to emphasise how easy it is.\medskip

   600 

   601 Volkswagen's argument was that the Birmingham people had reversed a

   602 locksmithing tool produced by a company in Vietnam, and since their key

   603 fob chip is claimed to be tamper-resistant, this must have involved a

   604 corrupt insider at VW or at its supplier Thales. Birmingham's argument

   605 is that this is nonsense as the cipher is easy to get hold of. Their

   606 lawyers feel this argument would come better from an independent

   607 outsider.\medskip

   608 

   609 Let me know if you're interested in having a go, and I'll put you in

   610 touch

   611 

   612 Ross

   613 \end{bubble}

   614 \end{textblock}}

   615 

   616 \end{frame}

   617 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   618 

   619 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   620 \mode<presentation>{

   621 \begin{frame}[c]

   622 \frametitle{Authentication Protocols}

   623 

   624 

   625 Alice (\bl{$A$}) and Bob (\bl{$B$}) share a secret key \bl{$K_{AB}$}\bigskip

   626 

   627 Passwords:

   628 

   629 \begin{center}

   630 \bl{$B \rightarrow A: K_{AB}$} 

   631 \end{center}\pause\bigskip

   632 

   633 Problem: Eavesdropper can capture the secret and replay it; \bl{$A$} cannot confirm the

   634 identity of \bl{$B$}  

   635 

   636 \end{frame}}

   637 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   638 

   639 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   640 \mode<presentation>{

   641 \begin{frame}[c]

   642 \frametitle{Authentication Protocols}

   643 

   644 Alice (\bl{$A$}) and Bob (\bl{$B$}) share a secret key \bl{$K_{AB}$}\bigskip

   645 

   646 Simple Challenge Response:

   488 \bl{$A \rightarrow B$:} & \bl{$N_a$}\\  

   650 \bl{$A \rightarrow B:$} & \bl{$N$}\\

   489 \bl{$B \rightarrow A$:} & \bl{$\{N_a, N_b\}_{K_{ab}}$}\\

   651 \bl{$B \rightarrow A:$} & \bl{$\{N\}_{K_{AB}}$}\\

   490 \bl{$A \rightarrow B$:} & \bl{$N_b$}\\

   652 \end{tabular} 

   491 \end{tabular}

   653 \end{center}

   492 \end{center}\pause

   654 

   493 

   655 

   494 An attacker \bl{$E$} can launch an impersonation attack by 

   656 \end{frame}}

   495 intercepting all messages for \bl{$B$} and make \bl{$A$} decrypt her own challenges.

   657 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   496 

   658 

   497 \end{frame}}

   659 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   498 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   660 \mode<presentation>{

   499 

   661 \begin{frame}[c]

   500 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   662 \frametitle{Authentication Protocols}

   501 \mode<presentation>{

   663 

   664 Alice (\bl{$A$}) and Bob (\bl{$B$}) share a secret key \bl{$K_{AB}$}\bigskip

   665 

   666 Mutual Challenge Response:

   667 

   668 \begin{center}

   669 \begin{tabular}{ll}

   670 \bl{$A \rightarrow B:$} & \bl{$N_A$}\\

   671 \bl{$B \rightarrow A:$} & \bl{$\{N_A, N_B\}_{K_{AB}}$}\\

   672 \bl{$A \rightarrow B:$} & \bl{$N_B$}\\

   673 \end{tabular} 

   674 \end{center}

   675 

   676 %\pause

   677 %An attacker \bl{$E$} can launch an impersonation attack by

   678 %intercepting all messages for \bl{$B$} and make \bl{$A$} decrypt her

   679 %own challenges.

   680 

   681 \end{frame}}

   682 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   683 

   684 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   521 \end{frame}}

   704 \end{frame}

   536 The attack:

   719 The attack (let $A$ decrypt her own messages):

   647 

   789 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   790 \mode<presentation>{

   791 \begin{frame}[c]

   792 \frametitle{Person-in-the-Middle}

   793 

   794 ``Normal'' protocol run:\bigskip

   795 

   796 \begin{itemize}

   797 \item \bl{$A$} sends public key  to \bl{$B$}

   798 \item \bl{$B$} sends public key  to \bl{$A$}

   799 \item \bl{$A$} sends message encrypted with \bl{$B$}'s public key, \bl{$B$} decrypts it

   800 with its private key

   801 \item \bl{$B$} sends message encrypted with \bl{$A$}'s public key, \bl{$A$} decrypts it

   802 with its private key

   803 \end{itemize}

   804 

   805 \end{frame}}

   806 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   807 

   808 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   809 \mode<presentation>{

   810 \begin{frame}[c]

   811 \frametitle{Person-in-the-Middle}

   812 

   813 Attack:

   814 

   815 \begin{itemize}

   816 \item \bl{$A$} sends public key  to \bl{$B$}  --- \bl{$C$} intercepts this message and send his own public key

   817 \item \bl{$B$} sends public key  to \bl{$A$} --- \bl{$C$} intercepts this message and send his own public key

   818 \item \bl{$A$} sends message encrypted with \bl{$C$}'s public key, \bl{$C$} decrypts it

   819 with its private key, re-encrypts with \bl{$B$}'s public key 

   820 \item similar for other direction

   821 \end{itemize}

   822 

   823 \end{frame}}

   824 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   825 

   826 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   827 \mode<presentation>{

   828 \begin{frame}[c]

   829 \frametitle{Person-in-the-Middle}

   830 

   831 Prevention:

   832 

   833 \begin{itemize}

   834 \item \bl{$A$} sends public key  to \bl{$B$}

   835 \item \bl{$B$} sends public key  to \bl{$A$}

   836 \item \bl{$A$} encrypts message with \bl{$B$}'s public key, send's {\bf half} of the message

   837 \item \bl{$B$} encrypts message with \bl{$A$}'s public key, send's {\bf half} of the message

   838 \item \bl{$A$} sends other half, \bl{$B$} can now decrypt entire message

   839 \item \bl{$B$} sends other half, \bl{$A$} can now decrypt entire message

   840 \end{itemize}\pause

   841 

   842 \bl{$C$} would have to invent a totally new message

   843 

   844 \end{frame}}

   845  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   814 \item the card only says yes or no to the terminal if the PIN is correct

   972 \item the card only says yes to the terminal if the PIN is correct

   821 \mbox{}\hspace{-6mm}\includegraphics[scale=0.5]{pics/chip-attack.png}

   979 \mbox{}\hspace{-6mm}\includegraphics[scale=0.5]{../pics/chip-attack.png}

   822 \includegraphics[scale=0.3]{pics/chipnpinflaw.png}

   980 \includegraphics[scale=0.3]{../pics/chipnpinflaw.png}

   879 logic is one way protocols are studied in academia

  1035 \end{frame}}

   880 (you can use computers to search for attacks)

  1036 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   881 

  1037 

   882 \end{frame}}

  1038 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   883 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1039 \mode<presentation>{

   884 

  1040 \begin{frame}[c]

   885 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1041 \frametitle{Best Practices}

   886 \mode<presentation>{

  1042 

   887 \begin{frame}[c]

  1043 {\bf Principle 1:} Every message should say what it means: the interpretation of 

   888 \frametitle{\begin{tabular}{@ {}c@ {}}Schneier: Step 1\end{tabular}}

  1044 a message should not depend on the context.\bigskip\pause

   889 

  1045 

   890 {\bf What assets are you trying to protect?}\bigskip

  1046 {\bf Principle 2:} If the identity of a principal is essential to the meaning of a message, it is prudent 

   891 

  1047 to mention the principal’s name explicitly in the message (though difficult).\bigskip

   892 This question might seem basic, but a surprising number of people never ask it. The question involves understanding the scope of the problem. For example, securing an airplane, an airport, commercial aviation, the transportation system, and a nation against terrorism are all different security problems, and require different solutions.

  1048 

   893 

  1049 

   894 \only<2>{

  1050 \end{frame}}

   895 \begin{tikzpicture}

  1051 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   896 \draw (0,0) node[inner sep=2mm,fill=cream, ultra thick, draw=red, rounded corners=2mm] 

  1052 

   897 {\begin{minipage}{10cm}

  1053 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   898 \small You like to prevent: ``It would be terrible if this sort of attack ever happens; we need to do everything in our power to prevent it.''

  1054 \mode<presentation>{

   899 \end{minipage}};

  1055 \begin{frame}[c]

   900 \end{tikzpicture}}

  1056 

   901 \end{frame}}

  1057 {\bf Principle 3:} Be clear about why encryption is being

   902 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1058 done. Encryption is not cheap, and not asking precisely why it is

   903 

  1059 being done can lead to redundancy. Encryption is not synonymous with

   904 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1060 security.

   905 \mode<presentation>{

  1061 

   906 \begin{frame}[c]

  1062 \begin{center}

   907 \frametitle{\begin{tabular}{@ {}c@ {}}Schneier: Step 2\end{tabular}}

  1063 Possible Uses of Encryption

   908 

  1064 

   909 {\bf What are the risks to these assets?}\bigskip

  1065 \begin{itemize}

   910 

  1066 \item Preservation of confidentiality: \bl{$\{X\}_K$} only those that have \bl{$K$} may recover \bl{$X$}.

   911 Here we consider the need for security. Answering it involves understanding what is being defended, what the consequences are if it is successfully attacked, who wants to attack it, how they might attack it, and why.

  1067 \item Guarantee authenticity: The partner is indeed some particular principal.

   912 

  1068 \item Guarantee confidentiality and authenticity: binds two parts of a message --- 

   913 \end{frame}}

  1069 \bl{$\{X,Y\}_K$} is not the same as \bl{$\{X\}_K$} and \bl{$\{Y\}_K$}.

   914 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1070 \end{itemize}

   915 

  1071 \end{center}

   916 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1072 

   917 \mode<presentation>{

  1073 

   918 \begin{frame}[c]

  1074 

   919 \frametitle{\begin{tabular}{@ {}c@ {}}Schneier: Step 3\end{tabular}}

  1075 \end{frame}}

   920 

  1076 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   921 {\bf How well does the security solution mitigate those risks?}\bigskip

  1077 

   922 

  1078 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   923 Another seemingly obvious question, but one that is frequently ignored. If the security solution doesn't solve the problem, it's no good. This is not as simple as looking at the security solution and seeing how well it works. It involves looking at how the security solution interacts with everything around it, evaluating both its operation and its failures.

  1079 \mode<presentation>{

   924 

  1080 \begin{frame}[c]

   925 \end{frame}}

  1081 \frametitle{Best Practices}

   926 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1082 

   927 

  1083 {\bf Principle 4:} The protocol designer should know which trust relations his protocol depends on, and why the dependence is necessary. The reasons for particular trust relations being acceptable should be explicit though they will be founded on judgment and policy rather than on logic.\bigskip

   928 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1084 

   929 \mode<presentation>{

  1085 

   930 \begin{frame}[c]

  1086 Example Certification Authorities: CAs are trusted to certify a key only after proper steps 

   931 \frametitle{\begin{tabular}{@ {}c@ {}}Schneier: Step 4\end{tabular}}

  1087 have been taken to identify the principal that owns it.

   932 

  1088 

   933 {\bf What other risks does the security solution cause?}\bigskip

  1089 \end{frame}}

   934 

  1090 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   935 This question addresses what might be called the problem of unintended consequences. Security solutions have ripple effects, and most cause new security problems. The trick is to understand the new problems and make sure they are smaller than the old ones.

   936 

   937 \end{frame}}

   938 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   939 

   940 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   941 \mode<presentation>{

   942 \begin{frame}[c]

   943 \frametitle{\begin{tabular}{@ {}c@ {}}Schneier: Step 5\end{tabular}}

   944 

   945 {\bf What costs and trade-offs does the security solution impose?}\bigskip

   946 

   947 Every security system has costs and requires trade-offs. Most security costs money, sometimes substantial amounts; but other trade-offs may be more important, ranging from matters of convenience and comfort to issues involving basic freedoms like privacy. Understanding these trade-offs is essential.

   948 

   949 \end{frame}}

   950 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   951