CMSC 433 Homework 4: Testing BoundedAtomicQueue and Security Best Practices - Prof. Willia, Assignments of Programming Languages

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• CMSC

Homework 4

• write test cases for BoundedAtomicQueue, using MultithreadedTC
• Should be atomic, fair, and the correct size
• You are given a correct implementation, and 4 broken implementations
• Write test cases that distinguish them
• Everything open, no release tests
  • this is a homework, not a project
• Due Friday Nov 16th

Upcoming stuff

• WebGoat security homework
• Distributed programming
  • Map/Reduce and Hadoop

Timing notes

• Turns out, OSX is way better than most other operating systems by default
• On OSX (as least on Leopard), Java Thread.sleep resolution is 1 millisecond
• On many other platforms, it is 10 milliseconds or 16 milliseconds
• Had to adjust tests cases to fit
• Project 4

Software Security

• Making sure that if your software is misused, it doesn’t do any of the vast number of things you didn’t intend for the software to do

On trusting trust

• You can hide a trojan horse in a compiler - or in the operating system

Slightly cool, but not very

interesting

• Get spotted in a code audit

Compiler

Code generateCode(AST method) { if (method.getName() .equals(“authenticateLogin”)) { return .. code with trap door.. } if (method.getName() .equals(“generateCode”)) { return ... code with special code gen ...; } .. generate code normally }

Software defects

• Traditional approach to correctness
  • define precondition
  • show that if precondition satisfied, output satisfied postcondition
• Didn’t examine what happened if input didn’t satisfy precondition

#1 source of security defects

• Untrusted, unverified and unexpected input leading to a program doing something completely unexpected - unexpected by developer - intended by attacker
• of all the untrusted input problems, # 1 is buffer overruns in C/C++.

Stack layout

int main(int argc, char *argv[]) { int value; char buf1[80]; … } argv argc return address frame pointer buf value

gets() is evil

• Impossible to use gets() correctly char buf[20]; gets(buf);

C String functions

char buf[20]; char * prefix = “http://”; strcpy(buf,prefix); strncat(buf, path, sizeof(buf) - strlen(buf));

sprintf

• char buf[80]; sprintf(buf, “%s - %d\n”, path, errno);