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SELinux 专题 1.任务引出 一个用户自己的进程，可以访问用户自己的任何文件，这按照传统的unix/linux文件访问控制设定，是没问题的。但是如果一个firefox进程访问用户的ssh私钥(~/.ssh/id_rsa)，这种行为总感觉怪怪的。 SELinux就是用来阻止这种不恰当行为的，此为MAC（Mandatory Access Control，强制访问控制模型)。前者叫DAC（Discretionary Access Control，自主访问控制模型）。和SELinux类似的还有一个叫AppArmor，同样基于LSM(Linux security module)，被CentOS等发行版使用。 2.SELinux的介绍 SELinux（Security-Enhanc... Read More

Vbs脚本病毒学习笔记（1） 1.Vbs脚本病毒的特点以及发展现状 ​ VBS病毒是用VB Script编写而成，该脚本语言功能非常强大，它们利用Windows系统的开放性特点，通过调用一些现成的Windows对象、组件，可以直接对文件系统、注册表等进行控制，功能非常强大。应该说病毒就是一种思想，但是这种思想在用VBS实现时变得极其容易。VBS脚本病毒具有如下几个特点： 1.编写简单，初学者也能很快学习并且编写出一个简易的Vbs脚本病毒。 2.破坏力大，脚本病毒不仅仅会破坏用户系统文件，还可以使得邮件服务器崩溃，网络发生阻塞。 3.较强的感染能力，由于是脚本直接解释执行，因此可以直接通过自我复制的方式感染其他的同类文件。 4.传播范围较大，通过htm文档，Em... Read More

1.什么是图像分割 1.1图像分割的含义以及基本发展 ​ 图像分割一般定义为将图像划分为同质组的过程，使每个区域都是同质的，但相邻区域的并集不是同质的。因此图像分割主要是确定合适的同质性措施，来区分对象彼此。 法一：图像驱动方法：基于图像像素的统计特征提取目标，大部分基于边缘分割技术 法二：模型驱动方法：通常用于图像分割的模型有a)目标背景/阈值模型，b)神经模型，c)马尔可夫随机场模型，d)模糊模型，e)分形模型，f)多分辨率和g)变换模型，即分水岭模型和小波模型。 对象背景模型：目前，基于阈值的方法在遥感领域，特别是在高分辨率影像的城市遥感应用中并不流行。 马尔可夫随机场模型（MRF）：它能够以先验分布的形式整合图像的光谱、纹理、上下文、空间属性，甚至先验... Read More

10月10日上课笔记 1.关于BOF的内存溢出问题 C语言设计之初是为了OS的开发，因此没有考虑到内存溢出的问题。BOF溢出覆盖了绝大部分漏洞的场景。 对于BOF的练习小作业，应当尝试使用Linux系统中的GDB编译器查看源码。可以在Visual Studio中安装对应的GDB插件查看源码。 PS:对应BOF小练习中，passwd以及yourpasswd内存的分配前后顺序，在vc编译器和gcc编译器中刚好相反 一个新的BOF问题： memcpy函数（复制内存，移动） Bof是c语言的固有特征，Java是C语言添加类后又减去了指针，指针是C的精华，也是糟粕。 那么对抗Bof的终极方法——将C语言更换为Rust语言。 2.网红语言Rust Rust可以编写Linux的内... Read More

1.Bof题目 追究漏洞和入侵的缘由，超过一半的锅需要BOF（buffer over flow）来背。所以第一时间了解bof很有必要。下面这个例子通过一个故意构造的场景，演示了bof的一种典型情况。 下面的这个c程序，看似人畜无害，实则蕴含一个危险的漏洞，或者说暗藏后门。 #include ... main() { char passwd[8] = {"??????"}; // 此处实际密码为2e4rfe char yourpasswd[8] = {""}; again: puts("please input passwd?"); gets(yourpasswd); if (strcmp(yourpasswd, passwd)= =0) goto ok; put... Read More

You’ll find this post in your _posts directory. Go ahead and edit it and re-build the site to see your changes. You can rebuild the site in many different ways, but the most common way is to run jekyll serve, which launches a web server and auto-regenerates your site when a file is updated. To add new posts, simply add a file in the _posts dire... Read More

This note demonstrates some of what Markdown is capable of doing. An exhibit of Markdown Note: Feel free to play with this page. Unlike regular notes, this doesn’t automatically save itself. Basic formatting Paragraphs can be written like so. A paragraph is the basic block of Markdown. A paragraph is what text will turn into when there is no... Read More

A safe integer is an integer that can be exactly represented as an IEEE-754 double precision number, and whose IEEE-75 representation cannot be the result of rounding any other integer to fit the IEEE-754 representation For example, $ 2 ^ {53} - 1 $ is a safe integer, it can be exactly represented Read More

Canon in D (Pachelbel’s Canon) - Cello & Piano [BEST WEDDING VERSION] Some of you know that we occasionally play for weddings. As you can imagine, we get a LOT of requests for Canon in D, and we discovered that there were no good arrangements available anywhere for piano and cello! Hard to believe given its popularity. So we decided to make ... Read More

Table example as below For now, these extended features are provided: Cells spanning multiple columns Cells spanning multiple rows Cells text align separately Table header not required Grouped table header rows or data rows Rowspan and Colspan ^^ in a cell indicates it should be merged with the cell above. This feature is contribu... Read More

1. Pie chart pie title Pets adopted by volunteers "Dogs" : 386 "Cats" : 85 "Rats" : 35 2. sequence diagram @startmermaid sequenceDiagram Alice -» Bob: Hello Bob, how are you? Bob–»John: How about you John? Bob–x Alice: I am good thanks! Bob-x John: I am good thanks! Note right of John: Bob thinks a longlong time, so longthat ... Read More

My First PlantUML PlantUML Block-1 @startuml Bob -> Alice : hello @enduml PlantUML Block-2 Bob -> Alice : hello world PlantUML Block-3 @startuml (*) –> “Initialization” if “Some Test” then –>[true] “Some Activity” –> “Another activity” -right-> () else ->[false] “Something else” –>[Ending process] () endif ... Read More

Paragraphs are separated by a blank line. 2nd paragraph. Italic, bold, and monospace. Itemized lists look like: this one that one the other one Note that — not considering the asterisk — the actual text content starts at 4-columns in. Block quotes are written like so. They can span multiple paragraphs, if you like. Use 3 dash... Read More

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce bibendum neque eget nunc mattis eu sollicitudin enim tincidunt. Vestibulum lacus tortor, ultricies id dignissim ac, bibendum in velit. Some great heading (h2) Proin convallis mi ac felis pharetra aliquam. Curabitur dignissim accumsan rutrum. In arcu magna, aliquet vel pretium et, m... Read More

Eos eu docendi tractatos sapientem, brute option menandri in vix, quando vivendo accommodare te ius. Nec melius fastidii constituam id, viderer theophrastus ad sit, hinc semper periculis cum id. Noluisse postulant assentior est in, no choro sadipscing repudiandae vix. Vis in euismod delenit dignissim. Ex quod nostrum sit, suas decore animal id i... Read More

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce bibendum neque eget nunc mattis eu sollicitudin enim tincidunt. Vestibulum lacus tortor, ultricies id dignissim ac, bibendum in velit. Proin convallis mi ac felis pharetra aliquam. Curabitur dignissim accumsan rutrum. In arcu magna, aliquet vel pretium et, molestie et arcu. Mauris lo... Read More

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur s... Read More

Put the math expression within $…$: \(\LaTeX{}\) $\Pi$ $ a * b = c ^ b $ $ 2^{\frac{n-1}{3}} $ $ \int_a^b f(x)\,dx. $ \( \int_a^b f(x)\,dx. \) \[\begin{cases} \text{if true}\ foo \\ \text{if false}\ bar \end{cases}\] $ \rho {\rm{FOD}} = \sum\limits{\sigma ,i} {(\delta _1 - \delta _2 n_i^\sigma ) \phi _i^\sigma ({\bf{... Read More

You can write regular markdown here and Jekyll will automatically convert it to a nice webpage. I strongly encourage you to take 5 minutes to learn how to write in markdown - it’ll teach you how to transform regular text into bold/italics/headings/tables/etc. Here is some bold text Here is a secondary heading Here’s a useless table: ... Read More