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THERE AND
BACK AGAIN
BRIAN CHESS SEPTEMBER 2013
Fred Sam Joe Fred Sam Joe A BRIEF HISTORY OF COMMUNICATIONS - - PowerPoint PPT Presentation
Fred Sam Joe Fred Sam Joe A BRIEF HISTORY OF COMMUNICATIONS - - PowerPoint PPT Presentation
THERE AND BACK AGAIN BRIAN CHESS SEPTEMBER 2013 Fred Sam Joe Fred Sam Joe A BRIEF HISTORY OF COMMUNICATIONS SECURITY 6 COMPUTER SECURITY 7 THE PROGRAMMER "Programming is hard" Donald Knuth Programmers not historically
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Fred Sam Joe
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Fred Sam Joe
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A BRIEF HISTORY OF COMMUNICATIONS SECURITY
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COMPUTER SECURITY
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THE PROGRAMMER
"Programming is hard" Donald Knuth
- Programmers not historically responsible for security.
- Programmers already have one hard job to do.
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DEFENSIVE PROGRAMMING IS NOT ENOUGH
Defensive programming: "Write the program to cope with small disasters." [Kernighan and Plauger] A C function with no error checking: void printMsg(FILE* file, char* msg) { fprintf(file, msg); } Crashes when file or msg is null.
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Error checking added:
void printMsg(FILE* file, char* msg) { if (file == NULL) { logError("attempt to print to null file"); } else if (msg == NULL) { logError("attempt to print null message"); } else { fprintf(file, msg); } }
DEFENSIVE PROGRAMMING IS NOT ENOUGH
No more crashes. Fixed? Hint: AAA1_%08x.%08x.%08x.%08x.%08x.%n
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THIS IS ENOUGH
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Must also defend against format string attacks:
void printMsg(FILE* file, char* msg) { if (file == NULL) { logError("attempt to print to null file"); } else if (msg == NULL) { logError("attempt to print null message"); } else { fprintf(file, "%.128s", msg); } }
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SOFTWARE QUALITY VS. SOFTWARE SECURITY
QUALITY
- Cannot be bolted on
- Must be built in
- Does the program do what
it's supposed to do?
- Will the users be happy?
- Are common cases smooth
and easy?
- Will people pay for it?
SECURITY
- Cannot be bolted on
- Must be built in
- Does the program have
“bonus” features?
- Will the attackers get what
they want?
- Are there corner cases we
haven't considered?
- What do we stand to lose?
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THE EXPLOITABILITY TRAP
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Clearly Dangerous Clearly Safe “I’ll fix it if you show me an exploit.” Trap
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CITI IPHONE INFO LEAK
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BER BERTRAND TRAND RUSSELL USSELL’S CHICKEN S CHICKEN
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Food Shelter Companions Food Shelter Companions
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Success is foreseeing failure.
– Henry Petroski
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STATIC ANALYSIS IS GOOD
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STATIC ANALYSIS = GOOD
= getInputFroNetwork(); copyBuffer( , ); exec( ); buff buff newBuff newBuff (command injection)
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CHAINSAW
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Building Security In Maturity Model (BSIMM)
http://www.bsi-mm.com
MEASURING PROCESS
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THERE AND
BACK AGAIN
BRIAN CHESS SEPTEMBER 2013