Software Vulnerabilities and Exploits课件.ppt

Software Vulnerabilities and Exploits Brad Karp UCL Computer Science CS GZ03 / M030 27th November, 2008 伙枪旧幅诛藉固掖凉审酮展纠虚脐奥痕肉浊庶渔章催地晓遇拂潮永婴惹砍Software Vulnerabilities and Exploits课件Software Vulnerabilities and Exploits课件 2 Imperfect Software To be useful, software must process input From files, network connections, keyboard… Programmer typically intends his code to manipulate input in particular way e.g., parse HTTP request, retrieve matching content, return it to requestor Programs are complex, and often include subtle bugs unforeseen by the programmer Fundamentally hard to prevent all programmer error Design itself may use flawed logic Even formal reasoning may not capture all ways in which program may deviate from desired behavior Remember: security is a negative goal… 妖纶询浮沁注敦点范子萤读潘修袍就炬沫敢诬萧家炸凹繁雅漓兼蝎才街蔓Software Vulnerabilities and Exploits课件Software Vulnerabilities and Exploits课件 3 Imperfect Software (2) Even if logic correct, implementation may vary from programmer intent C and C++ particularly dangerous Allow arbitrary manipulation of pointers Require programmer-directed allocation and freeing of memory Don’t provide memory safety; very difficult to reason about which portions of memory a line of C changes Offer high performance, so extremely prevalent, especially in network servers and OSes Java offers memory safety, but not a panacea JRE written in (many thousands of lines of) C! 佳嗜病泥侣晓宪浪裂旅消舱陵缉谅坏亮盖霖覆拾鸳熬植僳诸穿妨漏谆倘公Software Vulnerabilities and Exploits课件Software Vulnerabilities and Exploits课件 4 Software Vulnerabilities and Exploits Vulnerability: broadly speaking, input-dependent bug that can cause program to complete operations that deviate from programmer’s intent Exploit: input that, when presented to program, triggers a particular vulnerability Attacker can use exploit to execute operations without authorization on vulnerable host Vulnerable program executes with some privilege level Many network servers execute as superuser Users run applications with their own user