582 

   583 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   584 \begin{frame}[c]

   585 \frametitle{Man-in-the-Middle}

   586 

   587 Attack:

   588 

   589 \begin{itemize}

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

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

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

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

   594 \item similar for other direction

   595 \end{itemize}

   596 

   597 \end{frame}

   598 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   599 

   600 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   601 \begin{frame}[c]

   602 \frametitle{Man-in-the-Middle}

   603 

   604 Potential Prevention?

   605 

   606 \begin{itemize}

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

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

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

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

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

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

   613 \end{itemize}\pause

   614 

   615 %\bl{$C$} would have to invent a totally new message

   616 \alert{Under which circumstances does this protocol prevent

   617 MiM-attacks, or does it?}

   618 

   619 \end{frame}

   620 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   621 

   622 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   623 \begin{frame}[c]

   624 \frametitle{Car Transponder (HiTag2)}

   625 

   626 \begin{enumerate}

   627 \item \bl{$C$} generates a random number \bl{$N$}

   628 \item \bl{$C$} calculates \bl{$(F,G) = \{N\}_K$}

   629 \item \bl{$C \to T$}: \bl{$N, F$}

   630 \item \bl{$T$} calculates \bl{$(F',G') = \{N\}_K$}

   631 \item \bl{$T$} checks that \bl{$F = F'$}

   632 \item \bl{$T \to C$}: \bl{$N, G'$}

   633 \item \bl{$C$} checks that \bl{$G = G'$}

   634 \end{enumerate}\pause

   635 

   636 \small

   637 This process means that the transponder believes the car knows

   638 the key \bl{$K$}, and the car believes the transponder knows

   639 the key \bl{$K$}. They have authenticated themselves

   640 to each other, or have they?

   641 

   642 \end{frame}

   643 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   644 

   645 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   646 \begin{frame}[c]

   647 

   648 A Man-in-the-middle attack in real life:

   649 

   650 \begin{itemize}

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

   652 \item trick the card in thinking transaction is verified by signature

   653 \item trick the terminal in thinking the transaction was verified by PIN

   654 \end{itemize}

   655 

   656 \begin{minipage}{1.1\textwidth}

   657 \begin{center}

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

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

   660 \end{center}

   661 \end{minipage}

   662 

   663 \end{frame}

   664 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   665 

   666 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   667 \begin{frame}[c]

   668 \frametitle{Problems with EMV}

   669 

   670 \begin{itemize}

   671 \item it is a wrapper for many protocols

   672 \item specification by consensus (resulted unmanageable complexity)

   673 \item its specification is 700 pages in English plus 2000+ pages for testing, additionally some 

   674 further parts are secret

   675 \item other attacks have been found

   676 \end{itemize}

   677 

   678 \end{frame}

   679 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   680 

   681 

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

   683 \begin{frame}[c]

   684 \frametitle{Protocols are Difficult}

   685 

   686 \begin{itemize}

   687 \item even the systems designed by experts regularly fail\medskip

   688 \item the one who can fix a system should also be liable for the losses\medskip

   689 \item cryptography is often not the problem\bigskip\bigskip  

   690 \end{itemize}

   691 

   692 \end{frame}

   693 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   694 

   695 

  1167 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1168 \begin{frame}[c]

  1169 \frametitle{Mid-Term}

  1170 

  1171 \begin{itemize}

  1172 \item homework, handouts, programs\ldots

  1173 \end{itemize}\bigskip\bigskip\bigskip

  1174 

  1175 \begin{center}

  1176 {\huge\bf\alert{Any Questions?}}

  1177 \end{center}

  1178 

  1179 \end{frame}

  1180 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1181 

  1182 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1183 \begin{frame}[c]

  1184 \frametitle{Security Engineering}

  1185   

  1186   \begin{center}

  1187   \begin{tabular}{cc}

  1188   \raisebox{-0.8mm}{\includegraphics[scale=0.28]{../pics/flight.jpg}} &

  1189   \includegraphics[scale=0.31]{../pics/airbus.jpg}\\

  1190   \small Wright brothers, 1901 & \small Airbus, 2005 \\ 

  1191   \end{tabular}

  1192   \end{center}

  1193 

  1194   \end{frame}

  1195 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1196 

  1197 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1198 \begin{frame}[c]

  1199 \frametitle{1st Lecture}

  1200 

  1201 \begin{itemize}

  1202 \item chip-and-pin, banks vs.~customers

  1203 \begin{quote}\small\rm

  1204  the one who can improve security should also be 

  1205  liable for the losses 

  1206 \end{quote}\pause\bigskip

  1207 

  1208 \item hashes and salts to guarantee data integrity\medskip

  1209 \item storing passwords (you should know the difference between

  1210 brute force attacks and dictionary attacks; how do salts help?)

  1211 \end{itemize}

  1212 

  1213 \end{frame}

  1214 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

  1215 

  1216 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1217 \begin{frame}[c]

  1218 \frametitle{1st Lecture: Cookies}

  1219 

  1220 \begin{itemize}

  1221 \item good uses of cookies?\medskip

  1222 

  1223 \item bad uses of cookies: snooping, tracking, profiling\ldots

  1224       the ``disadvantage'' is that the user is in

  1225       \alert{control}, because you can delete them 

  1226           

  1227           \begin{center} ``Please track me using cookies.''

  1228           \end{center}\bigskip\pause

  1229                  

  1230 \item fingerprinting beyond browser cookies

  1231   \begin{quote}\small\rm

  1232   Pixel Perfect: Fingerprinting Canvas in HTML5\\ 

  1233   (a research paper from 2012)\\

  1234   \footnotesize

  1235   \url{http://cseweb.ucsd.edu/~hovav/papers/ms12.html}      

  1236   \end{quote}      

  1237 \end{itemize}

  1238 

  1239 \end{frame}

  1240 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

  1241 

  1242 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1243 \begin{frame}[c]

  1244 \frametitle{1st Lecture: Cookies}

  1245 

  1246 \begin{itemize}

  1247 \item a bit of JavaScript and HTML5 + canvas\medskip

  1248 \begin{center}

  1249 \begin{tabular}{cc}

  1250 Firefox & Safari\\

  1251 \includegraphics[scale=0.31]{../pics/firefox1.png} &

  1252 \includegraphics[scale=0.31]{../pics/safari1.png} \\

  1253 \tiny

  1254 \pcode{55b2257ad0f20ecbf927fb66a15c61981f7ed8fc} &

  1255 \tiny

  1256 \pcode{17bc79f8111e345f572a4f87d6cd780b445625d3}

  1257 \end{tabular}

  1258 \end{center}\bigskip

  1259 

  1260 \item\small no actual drawing needed\pause

  1261 \item\small in May 2014 a crawl of 100,000 popular 

  1262 webpages revealed 5.5\% already use canvas 

  1263 fingerprinting\smallskip

  1264 \begin{center}\scriptsize

  1265 \url{https://securehomes.esat.kuleuven.be/~gacar/persistent/the_web_never_forgets.pdf}

  1266 \end{center}

  1267 \end{itemize}

  1268 

  1269 \end{frame}

  1270 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

  1271 

  1272 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1273 \begin{frame}[c]

  1274 \frametitle{1st Lecture: Cookies}

  1275 

  1276 Remember the small web-app I showed you where a cookie 

  1277 protected a counter?\bigskip 

  1278 

  1279 \begin{itemize}

  1280 \item NYT, the cookie looks the ``resource'' - harm\medskip

  1281 \item imaginary discount unlocked by cookie - no harm

  1282 \end{itemize}

  1283 

  1284 \end{frame}

  1285 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

  1286 

  1287 

  1288 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1289 \begin{frame}[t]

  1290 \frametitle{2nd Lecture: E-Voting}

  1291 

  1292 Where are paper ballots better than voice voting?\bigskip

  1293 

  1294 \begin{itemize}

  1295 \item Integrity 

  1296 \item \alert{Ballot Secrecy}

  1297 \item Voter Authentication

  1298 \item Enfranchisement

  1299 \item Availability

  1300 \end{itemize}

  1301 

  1302 \end{frame}

  1303 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1304 

  1305 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1306 \begin{frame}[t]

  1307 \frametitle{2nd Lecture: E-Voting}

  1308 

  1309 \begin{itemize}

  1310 \item recently an Australian parliamentary committee 

  1311 found: e-voting is highly vulnerable to hacking and Australia 

  1312 will not use it any time soon\bigskip\pause

  1313 \item Alex Halderman, Washington D.C.~hack

  1314 \begin{center}

  1315 \scriptsize

  1316 \url{https://jhalderm.com/pub/papers/dcvoting-fc12.pdf}

  1317 \end{center}\medskip

  1318 

  1319 \item PDF-ballot tampering at the wireless router (the modification 

  1320 is nearly undetectable and leaves no traces; MITM attack with firmware 

  1321 updating)

  1322 \begin{center}

  1323 \scriptsize

  1324 \url{http://galois.com/wp-content/uploads/2014/11/technical-hack-a-pdf.pdf}

  1325 \end{center}

  1326 

  1327 \end{itemize}

  1328 

  1329 \end{frame}

  1330 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1331 

  1332 

  1333 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1334 \tikzset{alt/.code args={<#1>#2#3#4}{%

  1335   \alt<#1>{\pgfkeysalso{#2}}{\pgfkeysalso{#3}} % \pgfkeysalso doesn't change the path

  1336 }}

  1337 

  1338 \begin{frame}[t]

  1339 \frametitle{\begin{tabular}{c}3rd Lecture:\\ Buffer Overflow Attacks\end{tabular}}

  1340 

  1341 \begin{itemize}

  1342 \item the problem arises from the way C/C++ organises its function calls\\[-8mm]\mbox{}

  1343 \end{itemize}

  1344 

  1345 \begin{center}

  1346 \begin{tikzpicture}[scale=1]

  1347 %\draw[black!10,step=2mm] (0,0) grid (9,4);

  1348 %\draw[black!10,thick,step=10mm] (0,0) grid (9,4);

  1349 

  1350 \node at (0.5,4.5) {\small\begin{tabular}{l}main\\[-2mm] prog.\end{tabular}};

  1351 \draw[line width=0mm, white, alt=<2->{fill=red}{fill=blue}] (0,2.5) rectangle (1,3.8);

  1352 \draw[line width=0mm, white, alt=<9->{fill=red}{fill=blue}] (0,0.2) rectangle (1,0.5);

  1353 \draw[line width=1mm, alt=<3->{fill=yellow}{fill=blue}] (0,2.0) rectangle (1,2.5);

  1354 \draw[line width=1mm, alt=<6->{fill=red}{fill=blue}] (0,1.0) rectangle (1,2.0);

  1355 \draw[line width=1mm, alt=<7->{fill=yellow}{fill=blue}] (0,0.5) rectangle (1,1.0);

  1356 \draw[line width=1mm] (0,0) -- (0,4);

  1357 \draw[line width=1mm] (1,0) -- (1,4);

  1358 

  1359 \node at (3.5,3.5) {\small\begin{tabular}{l}fact(n)\end{tabular}};

  1360 \draw[line width=1mm, alt=<{4-5,8}>{fill=red}{fill=blue}] (3,1.0) rectangle (4,3.0);

  1361 

  1362 \onslide<3-4>{\draw[->, line width=1mm,red] (1,2.3) to node [above,sloped,midway] {n=4} (3,3);}

  1363 \onslide<5>{\draw[<-, line width=1mm,red] (1,2.3) to node [above,sloped,midway] {res=24} (3,1);}

  1364 

  1365 \onslide<7-8>{\draw[->, line width=1mm,red] (1,0.8) to node [above,sloped,midway] {n=3} (3,3);}

  1366 \onslide<9>{\draw[<-, line width=1mm,red] (1,0.8) to node [above,sloped,midway] {res=6} (3,1);}

  1367 

  1368 

  1369 \node at (7.75,3.9) {\small\begin{tabular}{l}stack\end{tabular}};

  1370 \draw[line width=1mm] (7,3.5) -- (7,0.5) -- (8.5,0.5) -- (8.5,3.5);

  1371 

  1372 \onslide<3,4,7,8>{

  1373 \node at (7.75, 1.4) {ret};

  1374 \draw[line width=1mm] (7,1.1) -- (8.5,1.1);

  1375 \node at (7.75, 2.0) {sp};

  1376 \draw[line width=1mm] (7,2.3) -- (8.5,2.3);

  1377 }

  1378 \onslide<3,4>{

  1379 \node at (7.75, 0.8) {4};

  1380 \draw[line width=1mm] (7,1.7) -- (8.5,1.7);

  1381 }

  1382 \onslide<7,8>{

  1383 \node at (7.75, 0.8) {3};

  1384 \draw[line width=1mm] (7,1.7) -- (8.5,1.7);

  1385 }

  1386 

  1387 

  1388 \end{tikzpicture}

  1389 \end{center}

  1390 

  1391 \end{frame}

  1392 

  1393 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1394 \begin{frame}[t]

  1395 

  1396 \begin{center}

  1397 \begin{tikzpicture}[scale=1]

  1398 %\draw[black!10,step=2mm] (0,0) grid (9,4);

  1399 %\draw[black!10,thick,step=10mm] (0,0) grid (9,4);

  1400 

  1401 \node at (0.5,4.5) {\small\begin{tabular}{l}main\\[-2mm] prog.\end{tabular}};

  1402 \draw[line width=0mm, white, alt=<2->{fill=red}{fill=blue}] (0,2.5) rectangle (1,3.8);

  1403 \draw[line width=1mm, white, fill=blue] (0,1.0) rectangle (1,2.0);

  1404 \draw[line width=1mm, alt=<3->{fill=yellow}{fill=blue}] (0,2.0) rectangle (1,2.5);

  1405 \draw[line width=1mm] (0,0) -- (0,4);

  1406 \draw[line width=1mm] (1,0) -- (1,4);

  1407 

  1408 \node at (3.5,3.5) {\small\begin{tabular}{l}fact(n)\end{tabular}};

  1409 \draw[line width=0mm, alt=<{4-}>{red, fill=red}{blue, fill=blue}] (3,2.8) rectangle (4,3.0);

  1410 \draw[line width=0mm, alt=<{5-}>{red, fill=red}{blue, fill=blue}] (3,2.8) rectangle (4,2.0);

  1411 \draw[line width=0mm, alt=<{7-}>{red, fill=red}{blue, fill=blue}] (3,2.0) rectangle (4,1.0);

  1412 \draw[line width=1mm] (3,1.0) rectangle (4,3.0);

  1413 

  1414 \onslide<3->{\draw[->, line width=1mm,red] (1,2.3) to node [above,sloped,midway] {n=4} (3,3);}

  1415 \onslide<5->{\draw[<-, line width=2mm,red] (4,2) to node [above,sloped,midway] 

  1416 {\begin{tabular}{l}user\\[-1mm] input\end{tabular}} (6,2);}

  1417 \onslide<8->{\draw[<-, line width=1mm,red] (1,-2) to (3,1);}

  1418 

  1419 \node at (7.75,3.9) {\small\begin{tabular}{l}stack\end{tabular}};

  1420 \draw[line width=1mm] (7,3.5) -- (7,-0.1) -- (8.5,-0.1) -- (8.5,3.5);

  1421 

  1422 \onslide<3->{

  1423 \node at (7.75, 0.2) {4};

  1424 \draw[line width=1mm,alt=<6->{fill=red}{fill=white}] (7,0.5) rectangle (8.5,1.1);

  1425 \node at (7.75, 0.8) {\alt<6->{@a\#}{ret}};

  1426 \draw[line width=1mm,alt=<6->{fill=red}{fill=white}] (7,1.1) rectangle (8.5,1.7);

  1427 \node at (7.75, 1.4) {\alt<6->{!?w;}sp};

  1428 }

  1429 

  1430 \onslide<4->{

  1431 \draw[line width=1mm,fill=red] (7,1.7) rectangle (8.5,3.0);

  1432 \node[white] at (7.75, 2.4) {buffer};

  1433 }

  1434 

  1435 \end{tikzpicture}

  1436 \end{center}

  1437 

  1438 \end{frame}

  1439 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1440 

  1441 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1442 \begin{frame}[t]

  1443 \frametitle{\begin{tabular}{c}3rd Lecture:\\[-3mm] 

  1444 Buffer Overflow Attacks\end{tabular}}

  1445 

  1446 US National Vulnerability Database\\ 

  1447 \small(636 out of 6675 in 2014)

  1448 

  1449 \begin{center}

  1450 \begin{tikzpicture}

  1451 \begin{axis}[

  1452     xlabel={year},

  1453     ylabel={\% of total attacks},

  1454     ylabel style={yshift=0em},

  1455     enlargelimits=false,

  1456     xtick={1997,1999,...,2015},

  1457     xmin=1996.5,

  1458     xmax=2016,

  1459     ymax=21,

  1460     ytick={0,5,...,20},

  1461     scaled ticks=false,

  1462     axis lines=left,

  1463     width=11cm,

  1464     height=5cm,

  1465     ybar,

  1466     nodes near coords=

  1467      {\footnotesize

  1468       $\pgfmathprintnumber[fixed,fixed zerofill,precision=1,use comma]{\pgfkeysvalueof{/data point/y}}$},

  1469     x tick label style={font=\scriptsize,/pgf/number format/1000 sep={}}]

  1470 \addplot

  1471   table [x=Year,y=Percentage] {../handouts/bufferoverflows.data};

  1472 \end{axis}

  1473 \end{tikzpicture}

  1474 \end{center}

  1475 

  1476 \scriptsize

  1477 \url{http://web.nvd.nist.gov/view/vuln/statistics}

  1478 \end{frame}

  1479 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1480 

  1481 

  1482 

  1483 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1484 \begin{frame}[t]

  1485 \frametitle{\begin{tabular}{c}4th Lecture:\\ Unix Access Control\end{tabular}}

  1486 

  1487 \begin{itemize}

  1488 \item privileges are specified by file access permissions (``everything is a file'') 

  1489 \end{itemize}\medskip

  1490 

  1491 \begin{center}

  1492   \begin{tikzpicture}[scale=1]

  1493   

  1494   \draw[line width=1mm] (-.3, 0) rectangle (1.5,2);

  1495   \draw (4.7,1) node {Internet};

  1496   \draw (-2.7,1.7) node {\footnotesize Application};

  1497   \draw (0.6,1.7) node {\footnotesize Interface};

  1498   \draw (0.6,-0.4) node {\footnotesize \begin{tabular}{c}unprivileged\\[-1mm] process\end{tabular}};

  1499   \draw (-2.7,-0.4) node {\footnotesize \begin{tabular}{c}privileged\\[-1mm] process\end{tabular}};

  1500   

  1501   \draw[line width=1mm] (-1.8, 0) rectangle (-3.6,2);

  1502 

  1503   \draw[white] (1.7,1) node (X) {};

  1504   \draw[white] (3.7,1) node (Y) {};

  1505   \draw[red, <->, line width = 2mm] (X) -- (Y);

  1506  

  1507   \draw[red, <->, line width = 1mm] (-0.6,1) -- (-1.6,1);

  1508   \end{tikzpicture}

  1509 \end{center}

  1510 

  1511 \begin{itemize}

  1512 \item the idea is to make the attack surface smaller and 

  1513 mitigate the consequences of an attack

  1514 \end{itemize}

  1515 

  1516 \end{frame}

  1517 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

  1518 

  1519 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1520 \begin{frame}[fragile,t]

  1521 \frametitle{\begin{tabular}{c}4th Lecture:\\ Unix Access Control\end{tabular}}

  1522 

  1523 \begin{itemize}

  1524 \item when a file with setuid is executed, the resulting process will assume the 

  1525 UID given to the owner of the file

  1526 \end{itemize}

  1527 

  1528 \footnotesize\tt

  1529 \begin{center}

  1530 \begin{verbatim}

  1531 $ ls -ld . * */*

  1532 drwxr-xr-x 1 ping staff  32768 Apr  2 2010 .

  1533 -rw----r-- 1 ping students  31359 Jul 24 2011 manual.txt

  1534 -r--rw--w- 1 bob students    4359 Jul 24 2011 report.txt

  1535 -rwsr--r-x 1 bob students  141359 Jun  1 2013 microedit

  1536 dr--r-xr-x 1 bob staff      32768 Jul 23 2011 src

  1537 -rw-r--r-- 1 bob staff      81359 Feb 28 2012 src/code.c

  1538 -r--rw---- 1 emma students    959 Jan 23 2012 src/code.h

  1539 \end{verbatim}

  1540 \end{center}

  1541 

  1542 

  1543 \end{frame}

  1544 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

  1545 

  1546 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1547 \begin{frame}[t]

  1548 \frametitle{\begin{tabular}{c}4th Lecture:\\ Unix Access Control\end{tabular}}

  1549 

  1550 \begin{itemize}

  1551 \item Alice wants to have her files readable, 

  1552 \alert{except} for her office mates.\bigskip

  1553 

  1554 \item make sure you understand the setuid and setgid bits; 

  1555   why are they necessary for login and passwd

  1556 \end{itemize}

  1557 

  1558 

  1559 \end{frame}

  1560 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%