2019-2020-1 20175313 "Information security system design basis" the third week of learning summary

table of Contents

First, the learning content summary
Second, the problem of teaching and learning in the process of resolving
Third, feelings and experiences
Fourth, learning progress bar
V. References

First, the learning content summary

Data type
| C declarations | the Intel data type | assembly code suffix | size (bytes) | bits |
| -------- |: ---------------- : |: ----------------: |: ---------------: |: -----: |
| target | 5000 rows | 30 Pian | 400 Xiaoshi | |
| week | 301/706 | 1/34 | 18/40 | |

NOTE: use the assembly code "l" represents a 4 to 8-byte integer and double precision floating point byte. This does not cause ambiguity, because the floating point number is a completely different set of instructions and registers.

Number of operations

操作数可分为三种类型：
1. 立即数
2. 寄存器
3. 内存引用

Operation indicator

process

P call Q:

call QThe instruction in P will call Qnext instruction address A onto the stack, and the program counter is set to the start position Q code.

retqA pop-up will address the instruction from the stack, and assign A PC

gdb debugging

objdump -d mstore.o disassemble

Buffer overflow

Minimize buffer overflow vulnerabilities in three ways:

Stack randomization: before the program starts, the size of the space allocated randomly between 0-n bytes are not being used on the stack, the stack such that a change in location has a program every time it runs.

Tamper detection stack: the stack is stored in the frame buffer with the stack between any of the local state of a particular canary value, and restoring register state from before the function returns, canary value check whether an operation or function of the an operation a function of the function call is changed. In order to determine whether a buffer overflow.

Limit executable code region: only save the code produced by the compiler portion of memory that only need to be enforceable, the other part can be restricted to only allow read and write. In order to eliminate the ability of the attacker to insert executable code into the system.