shift left

Description

Introductory Intel x86: Architecture, Assembly, Applications, & Alliteration Creator: Xeno Kovah For more information and to download the class material visit: http://bit.ly/OST_introx86 Playlist Open Security Training: http://bit.ly/OST_playlist Intel processors have been a major force in personal computing for more than 30 years. An understanding of low level computing mechanisms used in Intel chips as taught in this course serves as a foundation upon which to better understand other hardware, as well as many technical specialties such as reverse engineering, compiler design, operating system design, code optimization, and vulnerability exploitation. 25% of the time will be spent bootstrapping knowledge of fully OS-independent aspects of Intel architecture. 50% will be spent learning Windows tools and analysis of simple programs. The final 25% of time will be spent learning Linux tools for analysis. This class serves as a foundation for the follow on Intermediate level x86 class. It teaches the basic concepts and describes the hardware that assembly code deals with. It also goes over many of the most common assembly instructions. Although x86 has hundreds of special purpose instructions, students will be shown it is possible to read most programs by knowing only around 20-30 instructions and their variations. The instructor-led lab work will include: * Stepping through a small program and watching the changes to the stack at each instruction (push, pop, call, ret (return), mov) * Stepping through a slightly more complicated program (adds lea(load effective address), add, sub) * Understanding the correspondence between C and assembly control transfer mechanisms (e.g. goto in C == jmp in ams) * Understanding conditional control flow and how loops are translated from C to asm(conditional jumps, jge(jump greater than or equal), jle(jump less than or equal), ja(jump above), cmp (compare), test, etc) * Boolean logic (and, or, xor, not) * Logical and Arithmetic bit shift instructions and the cases where each would be used (shl (logical shift left), shr (logical shift right), sal (arithmetic shift left), sar(arithmetic shift right)) * Signed and unsigned multiplication and division * Special one instruction loops and how C functions like memset or memcpy can be implemented in one instruction plus setup (rep stos (repeat store to string), rep mov (repeat mov) * Misc instructions like leave and nop (no operation) * Running examples in the Visual Studio debugger on Windows and the Gnu Debugger (GDB) on Linux * The famous "binary bomb" lab from the Carnegie Mellon University computer architecture class, which requires the student to do basic reverse engineering to progress through the different phases of the bomb giving the correct input to avoid it "blowing up". This will be an independent activity.