tailieunhanh - gray hat hacking the ethical hackers handbook phần 5

• tràn trước • hậu quả của lỗi tràn bộ đệm • địa phương khai thác lỗ hổng tràn bộ đệm • Các thành phần của "khai thác bánh sandwich" • Khai thác tràn ngăn xếp bằng dòng lệnh và mã chung • Khai thác • Khai thác bộ đệm nhỏ bằng cách sử dụng các môi trường phân đoạn của bộ nhớ • Khai thác quá trình phát triển | Gray Hat Hacking The Ethical Hacker s Handbook 204 capabilities as a traditional command interpreter while hiding within an existing process and leaving no disk footprint on the target computer. References LSoD Unix Shellcode Components http projects LSoD Windows Shellcode Components http projects Skape Understanding Windows Shellcode code skape papers Skape Metasploit s Meterpreter projects Framework docs Arce Ivan The Shellcode Generation IEEE Security Privacy September October 2004 Other Shellcode Considerations Understanding the types of payloads that you might choose to use in any given exploit situation is an important first step in building reliable exploits. Given that we understand the network environment that our exploit will be operating in there are a couple of other very important things to understand. Shellcode Encoding Whenever we attempt to exploit a vulnerable application it is important that we understand any restrictions that we must adhere to when it comes to the structure of our input data. When a buffer overflow results from a strcpy operation for example we must be careful that our buffer does not inadvertently contain a null character that will prematurely terminate the strcpy operation before the target buffer has been overflowed. In other cases we may not be allowed to use carriage returns or other special characters in our buffer. In extreme cases our buffer may need to consist entirely of alphanumeric or valid Unicode characters. Determining exactly which characters must be avoided is generally accomplished through a combined process of reverse-engineering an application and observing the behavior of the application in a debugging environment. The bad chars set of characters to be avoided must be considered when developing any shellcode and can be provided as a parameter to some automated shellcode encoding engines such as .