cs161.txt

LEC02:
  Least Privilege:
    previously browser was run as [Browser Kernel + Rendering Engine + user Files]
      web site is a js program downloaded and run on rendering engine generate bitmap
      that sent to the screen; what happened if there is abug on the rendering engine exploited
      by the website?
      [drive-by malware: a malicious web page exploits a browser bug to infect local files]
    Chrome Design: Apply Least Privilege:
      break the browser into [trusted computing base: Browser kernel, sandbox for each tab:
      an isolated environment[process] to run unsafe code. Damage in the sandbox will not spread
       anywhere [where Rendering engne is located]]
      kernel and engine communicate via very narrow specified channel to [data/bitmap]
      prevent drive-by malware. 70% of vulnerabilites are in the rendering engine.
      chrome eat ram because each tab has its own sandbox and rendering engine.
      [Spectre attack]
  
  Separation of Responsibility:
    if u have something critical need to be done, don't have one thing to do it. 
    
    Also known as distributed trust
    
    If u need to have a privilege, consider requiring multiple parties to work together
    (collude) to exercise it.
     -> it's much more likely for a single party to be malicious than for all multiple parties
        to be malicious and collude with one another.
  
  Ensure Complete Mediation  
    make sure every request go through the security system
    *Reference Monitor* single point through which all access must occur.
      Example: network fireware.
    - vulnerability  : Time-of-check to Time-of-Use
  
  Don't Rely on security through Obsecurity  
    the only part of a cryptographic system unknown to the adversary are the cryptographic keys
  
    always asume that the attacker know every detail about the system u are worrking on.
    
  Use Fail-Safe Defaults  
    choose default settings that "fail safe" balancing security with usability when a sys 
    goes down
    
  Design in Security from the start  
---
Register:
  - fixed width. backward compatiability is maintained by allowing access to subset of registers
     so 32bits code still run on 64bits machine because processor can treat half of 64bits register as 32bits reg
     
  [global keyword] make the identifier accessible to the linker.   
    identifier + :  = label
    int 0x80 -> make a system call; determined by val in eax
    mul, sub operate implicitly on val in register eax
    EIP -> instruction pointer, his val changed by Jump ops
    -> nasm -f elf32 [file]
    elf32 -> 32bits executable and linking format.
    ld -m elf_i386 [object file]
    ld _> linker ld format to build executale from obj 
    db -> 1 byte, dw -> 2 bytes, dd -> 4 bytes.
    x86 stack:
      - LIFO
      - Random access, -> add/sub from the stack pointer to access any address.
      - ESP register hold the lowest addr of the stack 
      - pop put data in eax