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No question: Moodle | business secrets require extra protection. ● cwe - 259 : use of hard - coded ( “ default ” ) password, cwe - 327 : broken or risky crypto algorithm, and cwe - 331 : insufficient entropy ● reduce attack surface by storing minimal data ● ensure up - to - date algorithms and implementations ● disable legacy protocols 8 ow... | EPFL CS 402 Moodle |
No question: Moodle | possible 11 owasp top 10 : a05 security misconfiguration software is getting more configurable and administrators need to carefully balance features and security. any software along a complex stack may be misconfigured ● cwe - 16 configuration and cwe - 611 improper restriction of xml external entity reference ● docume... | EPFL CS 402 Moodle |
No question: Moodle | against authentication - related attacks. ● cwe - 297 : improper validation of certificate with host mismatch, cwe - 287 : improper authentication, and cwe - 384 : session fixation ● reduce attack surface through 2fa ● check for good password hygiene ( length, weak passwords, policies ) ● limit or increasingly delay fa... | EPFL CS 402 Moodle |
No question: Moodle | file ● mitigate by logging failed logins, authentication, or access control checks ● ensure high - value transactions have an audit trail ● protect log data through integrity or other safeguards 17 owasp top 10 : a10 server side request forgery ssrf flaws occur whenever a web application is fetching a remote resource w... | EPFL CS 402 Moodle |
No question: Moodle | > 0x01 common cyberthreats a05 security misconfiguration - > 0x01 common cyberthreats a06 vulnerable / outdated comps. - > 0x27 fuzzing ( and 0x15 somewhat ) a07 identification / authentication - > 0x03 access control & authentication a08 software and data integrity - > 0x14 data security ( and 0x15 somewhat ) a09 secu... | EPFL CS 402 Moodle |
No question: Moodle | city ='lausanne'; sql injection example example : authentication of a web application suffering from an sql injection 24 $ request = " select user from t _ user where user ='". $ _ get [ " user " ]. "'and password ='". $ _ get [ " password " ]. "'" $ result = mysqli _ query ( $ conn, $ request ) ; if (! $ result ) { ab... | EPFL CS 402 Moodle |
No question: Moodle | ' union select if ( substring ( password, 1, 1 ) = char ( 50 ), waitfor ( 50 ), null ) from users where uid = 1 ; - -'http : / / xkcd. com / 327 ldap for hackers : ● the lightweight directory access protocol is used to query directories verify a user's password read a user's attribute read a group's members ● search ex... | EPFL CS 402 Moodle |
No question: Moodle | and - how - to - stay - ahead here the context is runtime. exec, the java method to execute other programs ● the code wants to start the windows shell cmd. exe to list directory contents ● if chosen _ dir is “ photo ” you get the list of photographs ● if it is “ photo & rmdir / s / q photo ” you no longer have photos! ... | EPFL CS 402 Moodle |
No question: Moodle | the client side 32 https : / / fancywebapp /? eid = < script > alert ( ‘ hello from js! ’ ) < / script > deny by default, otherwise inspect received data twice when receiving : input validation ● refuse the characters you do not need ● for example, use a regular expression : when using : encode data ● escape ( encode )... | EPFL CS 402 Moodle |
No question: Moodle | sql, or ldap ) be sure to refuse by default, escape ( encode ) anything dangerous separate code and data ( e. g., sql prepared statements ) good web frameworks ( e. g., django, struts, ruby on rails ) take care of this for every request, check if the requesting user has adequate permissions! 35 software security buffer... | EPFL CS 402 Moodle |
No question: Moodle | ● mov : move data from an address or a register to an address or register ● add, mult, div : arithmetic calculations quick systems programming reminder 39 code heap stack c rip int main ( int argc, char * argv [ ] ) { int f = foo ( ) ; / / < - in foo ( ) / * ret addr * / bar ( f ) ; return 0 ; } stack buffer overflow 4... | EPFL CS 402 Moodle |
No question: Moodle | char buf [ 32 ] ; puts ( " your username? : " ) ; gets ( buf ) ; } int main ( ) { vuln ( ) ; } stack frame of main return address ( 0x11aa ) hi \ n vuln function runs and gets is called, user input is “ hi \ n ” stack frame of main return address ( 0x11aa ) unused stored base pointer stack frame of main return address ... | EPFL CS 402 Moodle |
No question: Moodle | ##aaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa vuln function runs and gets is called, user input is “ aaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaa … stack frame of main return address ( 0x11aa ) unused stack frame of main return address ( 0x11aa ) buf stored base point... | EPFL CS 402 Moodle |
No question: Moodle | ##aaa aaaaaaaaaaaaaa software bug : buffer overflow vulnerable program : the strcpy call copies a string into the buffer on the stack, potentially past the end of cookie. 46 int main ( int argc, char * argv [ ] ) { char authorized = 0 ; char cookie [ 31 ] ; if ( getenv ( " auth " )! = null & & strcmp ( getenv ( " auth ... | EPFL CS 402 Moodle |
No question: Moodle | ) ) ; strcpy ( cookie, argv [ 1 ] ) ; printf ( " thanks for the % s \ n ", cookie ) ; if ( authorized ) { printf ( " congratulations, you are authorized! \ n " ) ; } return 0 ; } software bug : buffer overflow ( getting authorized ) check the status of mitigations : $ checksec. / stack : no canary ; nx disabled ; no pi... | EPFL CS 402 Moodle |
No question: Moodle | 50 the exploit consists of two stages : an environment variable ( egg ) that contains the executable code. buffer input that triggers the buffer overflow, overwriting the return instruction pointer to point to that code. buffer input : str = " aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa " + eggloc + 0x0 note that eggloc m... | EPFL CS 402 Moodle |
No question: Moodle | \ xff \ xff \ x2f " / / call 0xed ( - 19 ) " \ x62 \ x69 \ x6e \ x2f \ x73 \ x68 \ x00 \ x5d " ; / / / bin / bash + \ 0 char buf [ 256 ] ; / / buffer used for overflow for ( int i = 0 ; i < bufsize + sizeof ( void * ) ; buf [ i + + ] ='a') ; / / fill buffer + rbp char * * buff = ( char * * ) ( & buf [ bufsize + sizeof ... | EPFL CS 402 Moodle |
No question: Moodle | ##fefd3 ) thanks for the aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa $ whoami gannimo $ exit 52 defense strategies stop memory corruption ● safe c / c + + dialects ccured, cyclone ● retrofit on c / c + + : softbounds + cets ● rewrite in safe language : java / c # 53 memory safety integrity randomization flow integrity attac... | EPFL CS 402 Moodle |
No question: Moodle | challenge : isas ( e. g., x86, arm ) did not distinguish code and data any data in the address space could be interpreted as code ( code injection : an attacker redirects control - flow to a buffer that contains attacker - controlled data as shellcode ) 58 defense : dep address space 59 defense : dep hardware support p... | EPFL CS 402 Moodle |
No question: Moodle | checking each pointer dereference, check integrity only before important data is accessed, e. g., before accessing a code pointer assumption : we only prevent rip control - flow hijack attacks we therefore only need to protect the integrity of the return instruction pointer key insight : buffer overflows are only possi... | EPFL CS 402 Moodle |
No question: Moodle | buffer overflow ( with canary ) 67 void vuln ( ) { char buf [ 32 ] ; puts ( " your username? : " ) ; gets ( buf ) ; } int main ( ) { vuln ( ) ; } stack frame of main the overflow clobbers the canary rip : 0x1195 rip : 0x11c4 stack frame of main return address ( 0x11aa ) stack frame of main return address ( 0x11aa ) unu... | EPFL CS 402 Moodle |
No question: Moodle | main return address ( 0x11aa ) aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa stack frame of main return address ( 0x11ed ) buf stored base pointer canary stack frame of main aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaaaa aaaaaaaaaaaa... | EPFL CS 402 Moodle |
No question: Moodle | 0xf ( % rbp ), % eax leaveq retq defense : stack canaries ( stack protector ) 70 push % rbp mov % rsp, % rbp sub $ 0x20, % rsp mov % rdi, - 0x18 ( % rbp ) mov - 0x18 ( % rbp ), % rdx lea - 0x10 ( % rbp ), % rax mov % rdx, % rsi mov % rax, % rdi callq 400410 < strcpy @ plt > movzbl - 0xf ( % rbp ), % eax leaveq retq pus... | EPFL CS 402 Moodle |
No question: Moodle | ##x8 ( % rbp ), % rcx xor % fs : 0x28, % rcx je < out > callq < _ _ stack _ chk _ fail @ plt > out : leaveq, retq on linux, canary is stored on per - thread page defense : stack canaries protect against continuous buffer - overflows by placing canary between buffer and other data canary is stored in a safe location, co... | EPFL CS 402 Moodle |
No question: Moodle | targets learn about sanitization methods to detect more bugs identify opportunities for improving fuzzers explain bug oracles and how they signal faults 2 guarding software supply chain is key! 3 ● attacker injects backdoor in liblzma ( compression library ) ● liblzma is used by openssh ● attacker can gain root access ... | EPFL CS 402 Moodle |
No question: Moodle | program analysis. code is analyzed, the testing environment observes the behavior of the code, detecting violations 7 turtles all the way down : bugs are everywhere giant code bases ● chromium, linux kernel, gnome, etc … ● millions of loc result in a huge attack surface ● millions of vulnerable hosts, bug is weaponizab... | EPFL CS 402 Moodle |
No question: Moodle | true bugs ) nor complete ( reports all bugs ) due to lack of runtime information but remains an indicator of possible bugs ● dynamic analysis ( fuzzing, symbolic execution ) is incomplete but sound due to state explosion but any reported issues are true bugs 9 manual testing 10 code reviews code review improves softwar... | EPFL CS 402 Moodle |
No question: Moodle | and how it interacts with the rest of the system. ● code is reviewed incrementally, assumes the rest of the code remains correct ● gradual review of code base, focusing on new code ● review changes ( i. e., pull requests or commits ) before they are integrated ● better suited to modern project development ● pioneered b... | EPFL CS 402 Moodle |
No question: Moodle | of warnings goal : highlight issues in code, give feedback to developer must be fast ( low overhead, simple analysis ) must have low false positives ( warning fatigue ) clang - wall - wextra - wpedantic ● wall : enables basic set of warnings, mostly easy to fix ● wextra : extends wall, being a little more detailed ; ex... | EPFL CS 402 Moodle |
No question: Moodle | types in python ● argument usage in c / c + + ● pre / postconditions for verification 19 codeql : static analysis framework to find bugs codeql is a pattern - based code analysis engine to automate security checks target code is parsed and analyzed based on patterns in the query language, starting from sources the patt... | EPFL CS 402 Moodle |
No question: Moodle | inside : free ( $ var ) ;... $ var = malloc (... ) ;... the 8 “ laws ” of static analysis can ’ t check code you don ’ t see : must fit into build system can ’ t check code you can ’ t parse : must parse “ real ” code not everything is implemented in c : must handle other languages not a bug : developers will not fix a... | EPFL CS 402 Moodle |
No question: Moodle | as symbols without concrete values define set of conditions at code locations ● symbolic execution determines triggering input testing : finding bugs in applications ● infer pre / post conditions and add assertions ● use symbolic execution to negate conditions generating poc input through sat / smt solving 27 state 1 :... | EPFL CS 402 Moodle |
No question: Moodle | ( x + y + z! = 3 ) ; } the parameters a, b, and c are symbolic. can the assertion ever by triggered? 29 symbolic execution : example 30 x = 0, y = 0, z = 0 a0 b0 < 5 b0 < 5! a0 & & c0! a0 & & c0 x = - 2 y = 1, z = 2 condition : a0 & & b0 < 5 & &! a0 & & c0 unsat infeasible path condition : a0 & & b0 < 5 & &! (! a0 & & ... | EPFL CS 402 Moodle |
No question: Moodle | if (! a & & c ) y = 1 ; z = 2 ; } assert ( x + y + z! = 3 ) ; } void func ( int a, int b, int c ) { int x = 0, y = 0, z = 0 ; if ( a ) x = - 2 ; / /! a - > a = 0 if ( b < 5 ) { / / b < 0 - > b = 4 if (! a & & c ) y = 1 ; / / c - > c = 1 z = 2 ; } assert ( x + y + z! = 3 ) ; } concolic execution symbolic execution is li... | EPFL CS 402 Moodle |
No question: Moodle | ; } assert ( x + y + z + d! = 3 ) ; } x0 = 0, y0 = 0, z0 = 0 x0 = 0, y0 = 0, z1 = 2 2 + d! = 3 - > d = 1 for sat fuzzing automatic and dynamic software testing technique key concept : fastest way to test a program is to run it ● runs on bare metal = > “ efficient ” analogy : obstacle course ● programs are riddled with ... | EPFL CS 402 Moodle |
No question: Moodle | research efforts 33 fuzzer best practices a fuzzer should explore the program ● a bug cannot be found if its code is not executed a fuzzer should trigger bugs ● executing buggy code does not necessarily mean a bug has been triggered ● e. g. strcpy ( dst, src ) with sizeof ( dst ) > = strlen ( src ) + 1 a fuzzer should ... | EPFL CS 402 Moodle |
No question: Moodle | ● specification is needed for input structure ● inputs are seen as parametric data ● parameters are sampled, constraints are resolved to generate grammatically - valid inputs ● may be slow, application - specific 39 mutation - based input generation can be subject to feedback - guided scheduling ● not necessarily / pur... | EPFL CS 402 Moodle |
No question: Moodle | ##zation ideal sanitizer : detect bugs as soon as they occur first approximation : cpu exceptions ( segfault, timeouts, div by 0, int overflows ) llvm sanitizers by policy : ● spatial and temporal memory safety addresssanitizer ( use - after - free, use - after - return, double - free, oob, unmapped address ) memorysan... | EPFL CS 402 Moodle |
No question: Moodle | / policy for expected behavior ● how to model logic or semantic bugs? need specification ● most specification is human - readable but not machine - readable ● can chatgpt help? 46 ● probably, too slow for fuzzing identifying faults crashes are a certain indicator of faults, but not all bugs crash sanitizers implement f... | EPFL CS 402 Moodle |
No question: Moodle | test cases, often using static analysis to fine - tune and adjust exploration formal techniques such as model checking or symbolic execution can give strong guarantees but are limited due to state explosion fuzzing is a powerful technique to find bugs with thousands of discovered bugs sanitization is integral for effic... | EPFL CS 402 Moodle |
No question: Moodle | store ) unpack and reverse engineer app this is relatively easy on android modify and add code ● add ads ● require more permissions than original app to steal user data ● escalate privileges using exploits to deploy ransomware ● … pack and publish modified version 8 piracy of digital content steal digital content from ... | EPFL CS 402 Moodle |
No question: Moodle | / nov / 03 / nso - group - pegasus - spyware - us - blacklist android ecosystem and security 12 android open source project ( aosp ) 13 android is “ owned ” by google code is made available through aosp original equipment manufacturer ( oem ) customizes code to their hardware oem adds proprietary components ( e. g., fo... | EPFL CS 402 Moodle |
No question: Moodle | ● some devices never get updated ( tablets ) ● most devices get updates only for 2 / 3 years ● android versions distribution secluded android devices 17 what android version would you target? 18 newer versions have more features and are more secure older versions have bigger reach what android version would you target?... | EPFL CS 402 Moodle |
No question: Moodle | compatibility problems? run all the tests! but are the tests comprehensive enough? patch deployment can be risky ● 2b + monthly active android users. broken patch can do damage. the perils of customization 25 previously : no clear interface between android os framework and vendor implementation when the android os is u... | EPFL CS 402 Moodle |
No question: Moodle | " bug bounties ” the role of security researchers 30 remember : attackers will also target anything not included in the bug bounties! security researchers want to ● identify malware ( add to disallow - lists, flag apps “ similar enough ” to listed malware apps ) ● report security vulnerabilities for bug bounties attack... | EPFL CS 402 Moodle |
No question: Moodle | try { inputstream in = new bufferedinputstream ( urlconnection. getinputstream ( ) ) ; readstream ( in ) ; } finally { urlconnection. disconnect ( ) ; } example of apis : http request ( doc ) 35 log. i ( " myapp ", " logging a message " ) ; log. e ( " com - 402 ", " test message " ) ; example of apis : log message ( do... | EPFL CS 402 Moodle |
No question: Moodle | ask chatgpt for a demo android framework apis 38 each app has a package name, e. g., " com. facebook. katana " the package name acts as a " unique " identifier across the system constraints : package name needs to be * unique * ● across apps installed on a specific android device ● across the google play store package ... | EPFL CS 402 Moodle |
No question: Moodle | , regardless of what the user is doing in foreground ( the user could be switching between activities ) example : a music player service services do not provide a user interface component : service 43 broadcast receivers are meant to respond to system - wide events they have a well - defined entry point as well the sys... | EPFL CS 402 Moodle |
No question: Moodle | the manifest file 47 https : / / developer. android. com / guide / topics / manifest / manifest - intro android studio 48 central / recommended ide for android app development common ide features like ● syntax highlighting ● go to definition / usage ● tooling for compilation, packaging, deployment ● tons of plugins : v... | EPFL CS 402 Moodle |
No question: Moodle | ". android framework architecture 55 image from https : / / source. android. com / security app b app a security boundary! android framework architecture 56 image from https : / / source. android. com / security app b app a instrumentation & analysis at these abstraction levels can be bypassed! pros : syscall analysis ... | EPFL CS 402 Moodle |
No question: Moodle | ##e. getlastlocation ( ) ( ref ) ● we are in a " privileged " service how do we go from one side to the other one? example : getlastlocation ( ) 60 binder : one of the main android's " extensions " over linux it allows for ● remote procedure call ( rpc ) ● inter - process communication ( ipc ) different from intents : ... | EPFL CS 402 Moodle |
No question: Moodle | connection, send sms ● the ability to " access " sensitive information, e. g., location, user contacts,... android permission system 65 https : / / developer. android. com / guide / topics / permissions / overview https : / / developer. android. com / reference / android / manifest. permission # send _ sms ● internet (... | EPFL CS 402 Moodle |
No question: Moodle | x86 : / sdcard $ ls - l drwxrwx - - x 2 root sdcard _ rw 4096 2018 - 09 - 28 20 : 59 alarms drwxrwx - - x 3 root sdcard _ rw 4096 2018 - 09 - 28 20 : 59 android drwxrwx - - x 2 root sdcard _ rw 4096 2018 - 09 - 28 20 : 59 dcim drwxrwx - - x 2 root sdcard _ rw 4096 2018 - 09 - 28 20 : 59 download drwxrwx - - x 2 root sd... | EPFL CS 402 Moodle |
No question: Moodle | 69 the compilation process 70 java source code. java java bytecode. class. jar dalvik bytecode. dex java compiler javac dex compiler dx executable by the jvm executable by the dvm c / c + + source code. c. cpp. h kotlin source code. kt. kts kotlin compiler kotlinc machine code. so interpreted or aot? 71 an apk is a zip... | EPFL CS 402 Moodle |
No question: Moodle | the os or other apps android implements defense in depth 76 apps are isolated from each other by being assigned to different users the sandbox is in the kernel : native code can't bypass it to bypass the sandbox, an attacker would need to compromise linux the application sandbox 77 bh usa ’ 22 – android universal root ... | EPFL CS 402 Moodle |
No question: Moodle | , low overhead ) mitigates against : buffer overflows, use - after - free. available since android 12 on armv9 compatible cpus. arm mte ( memory tagging extension ) 80 improved version of malloc with some additional features. ● randomized allocations ● guard pages to prevent some heap overflows ● more information store... | EPFL CS 402 Moodle |
No question: Moodle | benefits! android inc. ( purchased by google in ‘ 05 ) started developing android ‘ 03 google needed to catch up : “ open handset alliance ” ( 84 companies ) ecosystem is much more open in principle ● android / aosp is open source ● android can run on many different devices, even non - google ones ● easy to inspect and... | EPFL CS 402 Moodle |
No question: Moodle | everything about the system, except the key, is public knowledge! the mobile exploit market 91 92 mobile exploit payouts are exploding! ( 2019 ) 93 mobile exploit payouts are exploding! ( 2024 ) 94 full remote chain on samsung s24 : only 50, 000 $ ( 2024 ) 95 cellebrite iphone support ( april 2024 ) afu = after first u... | EPFL CS 402 Moodle |
No question: Moodle | users to a pretty good baseline, but it ’ s not customizable. mobile ecosystems rely on many layers of security, on system, during boot, and across different trust levels ( e. g., trust zone ) android fragmentation remains a key challenge apps are checked in the central marked and build on the ecosystem app security ma... | EPFL CS 402 Moodle |
No question: Moodle | ● demilitarized zone ( dmz ) * to expose organization's external facing networks to the internet towards outside : secure communication ● tls, ipsec, vpns 5 network segmentation break down the network into segments based on system and data classification or into functional zones access from zone to zone can be managed ... | EPFL CS 402 Moodle |
No question: Moodle | office vpn server vpn connection network segmentation : zones creating containment zones aims to stop attacks from spreading between zones communication between zones goes through firewalls this is closer to least privilege, than rings the challenge is creating firewall rules for each case, it ’ s easy to make mistakes... | EPFL CS 402 Moodle |
No question: Moodle | anybody, not even internal machines ● goal : prevent lateral movement ● continuously monitor and validate everything ● install local firewall on internal machines ( least privilege and access control ) ● encrypt all traffic between internal machines ( microsegmentation ) ● use strong authentication even internally ( mf... | EPFL CS 402 Moodle |
No question: Moodle | 172. 16. 0. 0 / 12, 192. 168. 0. 0 / 16 are reserved for private networks and not to be routed over the internet! 15 internet legend : router / vpn gateway physical network connection 80. 32. 3. 4 remote employee 42. 21. 5. 1 132. 2. 10. 1 10. 1. 0. 2 10. 1. 0. 3 10. 2. 0. 2 zurich office geneva office vpn : physical v... | EPFL CS 402 Moodle |
No question: Moodle | 10. 3. 0. 5 src 80. 32. 3. 4 dst 42. 21. 5. 1 vpn : example on linux, use the ip command to show network information : $ ip address show 15 : enp45s0u2 :... link / ether 00 : e0 : 4c : 1a : 39 : 90 brd ff : ff : ff : ff : ff : ff inet 128. 178. 122. 155 / 24 brd 128. 178. 122. 255 scope global dynamic noprefixroute enp... | EPFL CS 402 Moodle |
No question: Moodle | more specific routes ( in this case : 10. 2. 0. 0 / 24 vs. default ) take precedence! 19 vpn typical protocols ● ipsec, official ietf standard ● openvpn, open source software, based on tls ● wireguard, built into the linux kernel ● proprietary protocols ( e. g., cisco anyconnect, microsoft sstp ), offer convenience in ... | EPFL CS 402 Moodle |
No question: Moodle | of ip, tcp, and udp. firewalls are oblivious of the application for which the packets are transmitted 23 firewall within the network protecting the network with firewalls at the perimeter is insufficient due to lateral movement of attackers propagation of attacks is prevented by segmenting the internal network example ... | EPFL CS 402 Moodle |
No question: Moodle | at the network level ) proxies 29 internet ● direct proxies protect users when they access servers on the internet ● reverse proxies protect servers when accessed by users from the internet internet client proxy server client reverse proxy server web proxies goal : protect users surfing the web against threats by reduc... | EPFL CS 402 Moodle |
No question: Moodle | ##ing is getting more and more difficult due to technological advances such as ● hsts for enforcing https ● certificate pinning for preventing certificate spoofing ● perfect forward secrecy of tls 1. 3 for using ephemeral keys to prevent later decryption famous mailing list response by kenny paterson ( professor at eth... | EPFL CS 402 Moodle |
No question: Moodle | block an ip address for a certain time after detection of an attack ● authenticate users ( to prohibit unauthenticated users from interacting ) 35 waf example : modsecurity modsecurity started as an apache web server module and now protects diverse web servers and reverse proxies there is a free open source set of rule... | EPFL CS 402 Moodle |
No question: Moodle | | tab ; | newline ; ) ) * (? : b | & # x? 0 * (? : 66 | 42 | 98 | 62 ) ;? ) (? : \ t | & (? : # x? 0 * (? : 9 | 13 | 10 | a | d ) ;? | tab ; | newline ; ) ) * (? : s | & # x? 0 * (? : 83 | 5 3 | 115 | 73 ) ;? ) (? : \ t | & (? : # x? 0 * (? : 9 | 13 | 10 | a | d ) ;? | tab ; | newline ; ) ) * (? : c | & # x? 0 * (? : 6... | EPFL CS 402 Moodle |
No question: Moodle | - based ids compares network traffic against signatures from a pattern database, like a waf does for web traffic possible issues ● requires previous knowledge of an attack to create a signature ( false negatives for new attacks ) ● matched signature does not always mean successful attack, e. g. signature for a linux vu... | EPFL CS 402 Moodle |
No question: Moodle | ##n. php " ; fast _ pattern : only ; http _ uri ; content : " dalvik / " ; http _ header ; content : " android " ; within : 25 ; http _ header ; metadata : impact _ flag red, policy balanced - ips drop, policy security - ips drop, ruleset community, service http ; reference : url, blog. lookout. com / blog / 2017 / 02 ... | EPFL CS 402 Moodle |
No question: Moodle | packet ● it is 2am, you receive an alert from your ids what is the chance that this is a true alarm? ● 10 % ● 99. 9 % ● 1 % ● 50 % do you get up or stay in bed? 44 pr ( markedasmalware | ismalware ) = tpr = 0. 99 pr ( ismalware ) = 0. 0001 pr ( markedasmalware ) = 0. 01 pr ( ismalware | markedasmalware ) = pr ( markeda... | EPFL CS 402 Moodle |
No question: Moodle | typical issue : a program that is run by system is writable by any user, the attacker replaces the program by a malicious program and reboots the machine make sure that all programs are regularly patched to fix any known vulnerabilities make sure that the hard disk is encrypted, if not, attackers can boot from usb ( or... | EPFL CS 402 Moodle |
No question: Moodle | ##7. 36 ( khtml, like gecko ; compatible ; bingbot / 2. 0 ; + http : / / www. bing. com / bingbot. htm ) chrome / 103. 0. 5060. 134 safari / 537. 36 " 51. 222. 253. 5 - - [ 13 / nov / 2023 : 00 : 09 : 15 + 0100 ] " get / robots. txt http / 1. 1 " 404 439 " - " " mozilla / 5. 0 ( compatible ; ahrefsbot / 7. 0 ; + http :... | EPFL CS 402 Moodle |
No question: Moodle | ; x64 ; rv : 109. 0 ) gecko / 20100101 firefox / 111. 0 " 2a01 : 4f8 : 262 : 3f23 : : 2 - - [ 13 / nov / 2023 : 00 : 10 : 20 + 0100 ] " get / contact http / 1. 1 " 404 5275 " - " " symfony browserkit " 50 things you should never log : passwords! 51 things you should never log swiss federal act on data protection requir... | EPFL CS 402 Moodle |
No question: Moodle | backups are only done once every 24 hours, and some system parts are not backed up at all ● gitlab manages to restore from a six - hour - old backup but loses all the data submitted after backup recommendations 55 backup types : full, incremental ( data that changed since last backup ), differential ( data that changes... | EPFL CS 402 Moodle |
No question: Moodle | intentions prevent bad things from happening, while letting people do their work ( polp ) most measures ( zones, firewalls, proxies, vpns ) are preventive controls antivirus, wafs, ids are detective controls, detective measures have a higher operational cost because they generate false positives / negatives logs and ba... | EPFL CS 402 Moodle |
No question: Moodle | why trust a computer? 4 can we trust the hardware? trusted hardware : “ a piece of hardware can be trusted, if it always behaves in the expected manner for the intended purpose ” - trusted computing group imagine you could build a small version of you that you could fully trust to work perfectly i execute the correct p... | EPFL CS 402 Moodle |
No question: Moodle | module, or configuration information including the used software and hardware. enables secure persistent storage in untrusted memory. secure module data = unseal ( x, hash ) hash = seal ( data, x ) protects private information by binding it to platform configuration or the state. sealing encrypts data with keys stored ... | EPFL CS 402 Moodle |
No question: Moodle | store measurements in this pcrs registers. ● tpm _ extend ( d ) : adds a measurement to tpm. pcr [ n ] = sha256 ( pcr [ n ] | | d ) ● tpm _ pcrread ( n ) : returns pcr [ n ] 12 0000 0000 0000 0000 0000 pcr registers 0 1 2 3 4.. tpm _ extend ( d ) - > pcr [ n ] = sha256 ( pcr [ n ] | | d ) measurement tpm : attestation ... | EPFL CS 402 Moodle |
No question: Moodle | : sealing store : tpm _ seal ( keyhandle, pcrvalues, data ) recover : tpm _ unseal ( ) changing mbr, os kernel, or app code means that data cannot be decrypted hardware secure modules ( hsms ) external cryptography - oriented device to manage secrets. ● generating keys ● encrypting and decrypting data ● and creating an... | EPFL CS 402 Moodle |
No question: Moodle | api to cryptographic tokens, such as hardware security modules ( hsm ) and smart cards 16 intel sgx hardware extension that defines set of instructions for intel cpus to build trusted execution environment. creates enclaves that protects particular memory region from privileged users ( os, hypervisor ). 17 app hardware... | EPFL CS 402 Moodle |
No question: Moodle | signal? contact phone alice + 41 123456789 bob + 42 987654321 charlie + 43 546738291 signal users + 41 81477818 + 41 123456789 + 1 772888188 find intersection threat model : who do you want to protect against? why? 21 1. protect from signal privacy : users do not want to leak any information to signal about who their c... | EPFL CS 402 Moodle |
No question: Moodle | big. psi does not scale. 24 problem : how to do private contact discovery. threat model protect privacy of contacts signal : solvable with intel sgx? set of signal users : y = { + 1 …, + 41 … } keys : ( sk, pk ) public key of enclave : pk enc ( pk, x ) x y set of contacts : x = { + 41 …, + 42 … } intel sgx enclave sgx ... | EPFL CS 402 Moodle |
No question: Moodle | ( “ pukseal ”, ( sk, puk ) ) < reboot, reconstruct enclave > c 27 problem : how to do private contact discovery. threat model protect privacy of contacts signal : using sealing to store keys iphone backups problem statement : we want users to be able to backup their data to the cloud ; the user should be the only one t... | EPFL CS 402 Moodle |
No question: Moodle | users and cloud provider - apple and external parties iphone backups cloud storage enck ( data ) data backup recover data solution 2 : cryptography problem : what if you lose the phone? good cryptography is made so that if you do not have the key you cannot decrypt the data a backup system based on a key stored in the ... | EPFL CS 402 Moodle |
No question: Moodle | send data to the cloud 3. send key k to the hsm, encrypted with pkhsm 2. enc ( k, passwords ) ( skhsm, pkhsm ) user passcode * k hardware security module ( hsm ) cloud storage * this is a simplification! in reality the hsm does not directly store the passcode, they use password - authenticated key agreement ( pake ) to... | EPFL CS 402 Moodle |
No question: Moodle | external parties apple could steal the key 1. login 2a. c = enc ( pkhsm, passcode | pkuser ) procedure auth ( user, c ) passcode, pkuser = dec ( skhsm, c ) if passcode is correct & cnt < max : return enc ( pkuser, k ) else : increment cnt 2b. auth ( user, c ) 2c. enc ( pkuser, k or none ) 2d. enc ( pkuser, k or none ) ... | EPFL CS 402 Moodle |
No question: Moodle | often tamper resistant two types ● memory cards ● microprocessor cards contain keys and certificates : authentication / digital signatures, confidentiality, key management protocols 36 smartcards problem statement we want users to be able to signal to the bank to pay to a merchant without talking to the bank threat mod... | EPFL CS 402 Moodle |
No question: Moodle | problem : pin verification unauthenticated : just accept any pin ( yescard ) at issuance time : skcard, sig ( skbank, pkcard ) sig ( skca, cert ( pkbank ) ) carddata, pkcard, sig ( skbank, carddata, pkcard ) sig ( skca, cert ( pkbank ) ) noncet sig ( skcard, noncet, noncec ) pin entered pin ok online checking solves th... | EPFL CS 402 Moodle |
No question: Moodle | c : cd mod n = ( me ) d mod n = m for completeness, not important for this course 43 side channels : timing attacks rsa decryption : compute cd mod n a modular exponentiation operation naive algorithm : square and multiply w = length of d 1 0 1 d 44 side channels : timing attacks this takes a while to compute this is i... | EPFL CS 402 Moodle |
No question: Moodle | side channels micro - architectural side channels 49 catastrophic attack making it possible to read all memory of a process ( including protected kernel data ) by - product of the way some microarchitectural features are implemented ( e. g., amd x86 implementations are per chance resistant to meltdown ) exploits race c... | EPFL CS 402 Moodle |
No question: Moodle | forbidden access and speculatively use the result with non - architectural side - effects that reveal the secrets before the forbidden access is squashed secret = wherever ; secret attacker : before the exception is thrown something else will be executed speculatively 53 meltdown execute a forbidden access and speculat... | EPFL CS 402 Moodle |
No question: Moodle | linux, kernel page - table isolation ( kpti ) ; similar in other oss ● performance penalty in linux around 5 - 10 %, up to 30 % user space kernel space user and kernel mode user space kernel space user mode user space kernel space kernel mode 57 possible mitigations another catastrophic attack making it possible to rea... | EPFL CS 402 Moodle |
No question: Moodle | - effects that reveal the secrets if ( x < array1 _ size ) y = array2 [ array1 [ x ] * 4096 ] ; array1 [ x ] if ( x < array1 _ size ) array1 [ x ] victim : if we use the speculatively loaded value ( array1 [ x ] ) for a memory access, trace of it will remain in the cache 61 spectre speculatively execute leaky code with... | EPFL CS 402 Moodle |
No question: Moodle | ##s / devices / system / cpu / vulnerabilities / * ; do echo $ i ; cat $ i ; done / sys / devices / system / cpu / vulnerabilities / gather _ data _ sampling : not affected / sys / devices / system / cpu / vulnerabilities / itlb _ multihit : not affected / sys / devices / system / cpu / vulnerabilities / l1tf : not aff... | EPFL CS 402 Moodle |
No question: Moodle | : enhanced ibrs, ibpb : conditional, rsb filling, pbrsb - eibrs : sw seq. / sys / devices / system / cpu / vulnerabilities / srbds : not affected / sys / devices / system / cpu / vulnerabilities / tsx _ async _ abort : not affected 65 even with trusted hardware, vendor requires some trust backup data system from apple ... | EPFL CS 402 Moodle |
No question: Moodle | ##aways for trusted computing trusted hardware ● why is trusted hardware required? ● how does trusted hardware work? ● what guarantees does trusted hardware provide? ● case studies side - channel attacks ● digging tunnels to bypass walls ● speculative side - channel attacks 67 com - 402 : information security and priva... | EPFL CS 402 Moodle |
No question: Moodle | you share, … offline : your ethnicity, job history, the magazines you read, if you ’ ve ever declared bankruptcy or got divorced, the year you bought your house, where you went to college, the number of cars you own,... target can use this information for sending customers with kids catalogs of toys before christmas se... | EPFL CS 402 Moodle |
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