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Hacking in C: Understanding Software Vulnerabilities
- 1. Hacking in C hic 1
- 2. About this course: topics & goals • Standard ways in which software can be exploited – understanding how such attacks work – understanding what makes these attacks possible – doing some attacks in practice • Root cause analysis: why are things so easy to hack? • This involves understanding – programming languages, compilers, and operating systems, and the abstractions that they provide – the languages, representations, and interpretations involved – the potential for trouble – in the form of software vulnerabilities - all this introduces hic 2
- 3. Hacking in C • security problems in machine code compiled from C(++) source code running on standard CPU and operating system. • to understand this, we need to know how – the data representations involved – the memory management that the programmer has to do hic 3
- 4. Prerequisites • Imperatief Programmeren – we won’t use C++, but C – biggest change: using printf instead of >> ? • Processoren – what is the functionality that a typical CPU offers, on which we have to run our software written in higher-level languages? Eg. fetch-execute cycle of the CPU, with Program Counter (PC) registers where in the code we are, which is modified for a JUMP instruction and incremented for the other instructions hic 4
- 5. Lectures & lab sessions • Lectures Mondays 13:45-15:30 in HG00.304 • Lab sessions Thursdays 10:45-12:30 in HG00.137 & HG00.625 Aanstaande woensdag: als je al bekend met Linux command line ga dan naar HG00.625 • All course material will be on http://www.cs.ru.nl/~erikpoll/hic hic 5
- 6. Lab exercises Weekly lab session with weekly programming/hacking exercise • Exercises to be done in pairs • Doing the exercises is obligatory to take part in the exam; • Exercises will be lightly graded to provide feedback, with nsi-regeling: you can have only one exercise niet-serieus-ingeleverd • You learn stuff in the exercises that you won't learn at the lectures, and vv. • Beware: exercises of one week will build on knowledge & skills from the previous week • Also: turning up for the lab sesions might be crucial to sort out practical problems (with C, gcc, Linux, ...) hic 6
- 7. Lab exercises We use • C as programming language, not C++ • Linux from the command line aka shell • the compiler gcc So no fancy graphical user interfaces (GUIs) for the operating system (OS) or the compiler Why? • GUIs are nice, but hide what OS and compiler are doing • the command line is clumsy at first, – using commands instead of pointing & clicking but gives great power – we can write shell scripts: programs that interact with the OS hic 7
- 8. ‘to hack’ NB several meaning and connotations, incl. 1. To write software in a clever way – to really exploit all the capabilities a system offers 2. To break into a computer system. 3. To fix some problem in a quickly & ugly way Focus of this course 1 & 2. hic 8
- 9. How do you break into a computer system? 1. Using user credentials – username/password How do you get those? – default passwords hic 9
- 10. Default passwords exploited by Mirai botnet hic 10
- 11. Default passwords exploited by Mirai botnet hic 11
- 12. How do you break into a computer system? 1. Using user credentials – username/password How do you get those? – default passwords – phishing – brute forcing – eavesdropping, • on unsecured network connection, • with keylogger hardware or software keylogger – using stolen password files • which may need to be brute forced, if passwords are hashed – ... 2 Using flaws in the software – Focus of this course & web security next quarter hic 12
- 13. Security problems in software Terminology can be confusing: (security) weakness, flaw, vulnerability, bug, error, coding defect, ... Important distinction: 1. security weakness/flaw: something that is wrong or could be better 2. security vulnerability weakness/flaw that can actually be exploited by an attacker, This requires the flaw to be 1. accessible - attacker has to be able to get at it 2. exploitable – attacker has to be able to do some damage with it Eg by unplugging your network connection, many vulnerabilities become flaws Warning: there is no standardised terminology for the distinction above! hic 13
- 14. Software security prices (2015) hic 14
- 15. design vs implementation flaws Software vulnerabilities can be introduced at different “levels” • design flaws – fundamental error in the design • implementation flaws or coding error – introduced when implementing The precise border is not precise it can be debatable whether a flaws is a design or implementation flaw To understand implementation flaws, we need to look 'under the hood' of how a programming language works hic 15 focus of this course
- 16. To understand implementation flaws hic 16