基于MATLAB的窗函数法设计FIR数字滤波器

这个代码虽然虽然也是在网上下的，但是为了更好的理解，加了自己的注释。

控制学科sci期刊IET control theory and application 期刊的最新latex投稿模板

该文档包含了比较全面的行为识别的综述，以及深度学习的最近进展，能够帮助大家尽快掌握该领域的发展现状，为大家理清研究思路提供一定的帮助和参考。

一款基于Simulink的移相全桥DC/DC变换器模型

1)问题描述迷宫求解是实验心理学中的一个经典问题，心理学家把一只老鼠从一个无顶盖的大盒子的入口处赶进迷宫，迷宫中设置很多隔壁，对前进方向形成了多处障碍，心理学家在迷宫的唯一出口处放置了一块奶酪，吸引老鼠在迷宫中寻找通路以到达出口。例如，图2所示为一个迷宫示意图，其中双边矩形表示迷宫，1代表有障碍，0代表无障碍。 0 1 2 3 4 5 6 7 8 90 1 1 1 1 1 1 1 1 1 111 0 1 1 1 0 1 1 1 12 1 1 0 1 0 1 1 1 1 13 1 0 1 0 0 0 0 0 1 14 1 0 1 1 1 0 1 1 1 15 1 1 0

振南这几年一直在研究FAT32文件系统与SD卡、Flash等嵌入式存储的相关技术，初衷一方面在于振南对它的浓厚兴趣，因为其中蕴涵着很多非常巧妙的设计思想和理念，通过更加系统化、工程化的开发实践，自身的水平得到了很大的提升；另一方面随着嵌入式存储技术的迅猛发展，基于通用嵌入式FAT32文件系统的应用与产品层出不穷，这催生了对这方面技术和功能的极大需求。振南希望通过自己的研究，让广大的爱好者与工程师轻松地进入这一领域，对大家产生一定的参考意义。　　基于振南长期而深入的研究，一个精简、优秀而功能完备的嵌入式FAT32文件系统方案很早便应运而生，并一直维护至今，这就是振南的znFAT。经过几年的推广

全新RTCM3.3协议完整版RTCM STANDARD 10403.3DIFFERENTIAL GNSS(GLOBAL NAVIGATION SATELLITE SYSTEMS)SERVICES – VERSION 3DEVELOPED BYRTCM SPECIAL COMMITTEE NO. 104OCTOBER 7, 2016COPYRIGHT©2016 RTCMRadio Technical Commission for Maritime Services1611 N. Kent St., Suite 605Arlington, Virginia 22209-214RTCM Paper 141-2016-SC104-STD000ocRTCMco00c30RTCM 10403. 3, Differential GNSS Global Navigation Satellite Systems)Services- Version 3, October 7, 2016This standard (referred to as version 3 has been developed by rtCm special Committee 104 as a moreefficient alternative to the standards entitled rtcm recommended standards for diffe rentialRecommended Standards for Differential gNss Global Navigation Satellite Systems Service, Version 2.x(Current version is 2. 3, now designated as RTCM 10402. 3. Service providers and vendors represented onthe SC104 Committee wanted a new standard that would be more efficient, easy to use, and more easilyadaptable to new situations. The main complaint was that the version 2. x parity scheme, which useswords with 24 bits of data followed by 6 bits of parity, was wasteful of bandwidth. Another complaint wasthat the parity was not independent from word to word. Still another was that even with so many bitsdevoted to parity the actual integrity of the message was not as high as it should be. Plus, 30-bit wordsare awkward to handle. the new standard version 3 is intended to correct these weaknessesUnlike Version 2. x, this standard does not include tentative messages The messages in Version 3 haveundergone testing for validity and interoperability and are considered to be permanent. amendments tothe standard may change the meaning of reserved bits or provide additional clarifying text, but no changeswill be made in the data fields. Changes will require new messages to be developed. In addition to themessages described in the current standard the committee continues to develop new messages whichare described in separately published amendments and periodically gathered into a new edition of thestandard. RTCM 10403x for dgNSS services is proving useful in supporting highly accurate differentialand kinematic positioning as well as a wide range of navigation applications worldwideNote that Version 3 messages are not compatible with Version 2. x. Since many receivers have beendesigned and programmed for use with Version 2. x messages, rtCm is maintaining both standards0402 3 and 10403, 3 as" standardsVersion 3.0The initial edition consisted primarily of messages designed to support real-time kinematic (RTK)operations. The reason for this emphasis is that rtk operation involves broadcasting a lot of informationand thus benefits the most from an efficient data format. Version 3.0 provided messages that supportGPS and gloNaSs rTK operations including code and carrier phase observables antenna parametersand ancillary system parametersVersion 3. 1(RTCM Standard 10403.1:The next edition, Version 3. 1 (RTCM Standard 10403. 1), incorporated GPS Network Corrections, whichenable a mobile receiver to obtain accurate rtk information valid over a large area. In addition, new GPSand GLoNaSS messages provide orbital parameters to assist in rapid acquisition a Unicode text messageis also provided for the transmission of textual data. Finally a set of messages are reserved for vendorswho want to encapsulate proprietary data in their broadcasts the gps Network Corrections enable amobile receiver to obtain accurate rtk information valid over a large area. the network rtk correctioninformation provided to a rover can be considered as interpolated corrections between the referencestations in the rtk network this interpolation is not perfect and varies with the actual conditions of theatmosphere. A residual interpolation error has to be expected. With sufficient redundancy in the RtKnetwork, the network server process can provide an estimate for residual interpolation errors. Suchquality estimates may be used by the rover to optimize the performance of rtk solutions The values maybe considered by the rover as a priori estimates only with sufficient tracking data available the rovermight be able to judge residual geometric and ionospheric errors itselfVersion 3. 1. Amendment 1:Amendments 1 was an extensive addition that adds rtcm messages containing transformation data andinformation about Coordinate reference Systems. For rtCm data supporting a rtk service, coordinatesare measured within the itrf or a regional realization surve yors and other users of rtk services mustnormally present their results in the coordinates of local datums. Therefore, coordinate transformationsare necessary. by having RTCM messages that contain transformation data and information about theCoordinate reference systems the users of the rtk service can obtain their results in the desired datumwithout any manual operations. the rtk service providers can then ensure that current information forthe computation of the transformations is always used. the convenience of this method will promote theacceptance of rtK servicesVersion 3. 1. amendment 2:Amendment 2 added residual error messages to support the use of Non-Physical or Computed referenceStations in a network rtk environmentVersion 3. 1. amendment 3:Amendment 3 addressed differences in the way gnss receiver manufacturers have implemented carrierphase encoding of some Version 3 messages so that carrier phase observations are in phase for all carrierphases of a specific frequency i e. they correct for quarter cycle phase shifts. others retain the quartercycle offset between the carrier phase observations in the data. this amendment documents the waydifferent manufacturers have handled the phase shift issue and prescribes a uniform approach for futureproducts.∨ersiⅰon3.1, Amendment4:Amendment 4 added sections 3.5.13 on glONASS Network rtK Correction Messages and 3.5. 14 on FKPNetwork Rtk Correction Messages Related revisions were also made elsewhere in the document.Version 3. 1. amendment 5Amendment 5 added section 3. 5. 12 on State Space Representation related revisions are also madeelsewhere in the document, along with some editorial correctionsVersion 3. 2(RTCM Standard 10403.2)Version 3.2 consolidates Version 3. 1 and all five amendments into a new edition, and it adds MultipleSignal Messages (MSM)as well. the Multiple Signal Message (MSm)format generates receiverobservables in the same way for all included satellite systems. the messages include compact and fullmessages for Pseudorange, PhaseRange, Carrier to Noise Ratio (standard and high resolution), andPhaseRangeratea table near the beginning of the standard lists which messages were included in each separate editionand amendment, so it should not be necessary for users to refer to older versions. Multiple signalMessages are a generic format that will be followed for all GNSs systems. version 3 originally consisted ofmessages for GPS and GLONASS, each in their own format Now with the imminent addition of signals forBeiDou, Galileo, and QZSS, as well as new signals provided by modernized GPS and GloNASS satellitesthe need for a consistent generic format became evident. service providers and users are urged to migrateto the MsM messages to make it easier to accommodate new gNss services(See The RTCM Multiple Signal Messages: A New Step in GNSS Data Standardization")Another newmessage is the gloNaSS Bias Information message. This message provides information which is intendedto compensate for the first-order inter-frequency phase range biases introduced by the reference receivercode- phase biasVersion 3.2, Amendment 1:Added Galileo F/NAv Satellite Ephemeris Data(msg. 1045 )and Bds MSM(msgs. 1121-1127)Version 3.2 amendment 2Added qzss ephemeris(msg. 1044 )and QZss MSm (msgs. 1111-1117Version 3. 3(RTCM Standard 10403.3)This new edition adds Satellite-Based Augmentation System Multiple Signal Messages to previouslydopted messages for GPS, GLONASS, Galileo, and QzssA new ephemeris message has been added for BeiDou(BDS)and a new I/NAV ephemeris message hasbeen added for Galileo. The new edition also reserves 100 messages be used exclusively by sc104 fornew message developmentFinally, the new edition makes consolidates previous amendments and makes numerous editorialImprovementsNavstar GPS Service, Version 2. x. Service providers and vendors represented on the scco000c30z1O2co00c30Contentsco00c30

该书详细介绍了linux中关于selinux部分功能的实现流程和关键代码分析7.1.1.3基于创建者SID的文件系统.,,7.1.2 Gcncralizcd Sccurity Context labeling,,,,637.1.4 Mount-Point labeling667.1.5 Initial SId87.1.5.1 Initia1SID和 Initial sc的定义7.1.5.2 Initia1SID和 Initial sc的写出和解析707.1.5.3 Initia1SID和 Initia1SC的使用717.1.6进程创建的内核数拥结构的标签727.2何时需要为应用程序开发pp?●··垂·看垂723设计pp的一般过程7.4为vock程序编写v1ock.pp●垂春·垂767.4.1第一阶段:定义基本的te,fc和.if文件767.4.2第二阶段:根据 AVC Denied msg补充相应的规则807.4.3第三阶段:使用 don audit规则屏蔽与冗余操作枓关的错误信息7.4.4其他注意事项87.5为 samhain程序编写 samhain.pp..857.5.1第一阶段:定义基本的.te,,fc和.if文件事垂垂7.5.2第二阶段:根据 AVC Denied msg补充相应的规则07.5.3第三阶段:使用 don audi t规则屏蔽与冗余操作相关的错误信息927.5.4图解:使用 samhain时的 Domain transition过程春春鲁看D垂垂春,,937.6使用 SLIDE来开发pp,分析 SELinux源代码.7.7编写pp时的注意事项中垂鲁鲁··●,,,,,,,,,,,948. SELinux问题分析步骤总结.8.1排除DAC权限的问题,,,968.2检查用户当前所扮演的角色963分析 AvC Denied message: Target的标签正确吗?,8.4在系统启动过程中适时地修复错误的文件标签97应用程序的实际行为要和其pp的假设相一致,,,,988.6明确相应 domain所缺少的权限8.7其他注意事项8.7.1在 Permissive模式卜调试,998.7.2取消所有的 dontaudit规则.8.7.3当心 MLS Constraints1008.7.4检査 SeLinux- aware应用程序的配置和编译选项,.1018.7.5积极地和社区交互.1018.7.6使用 strace直接定位失败的系统调用(重要!).………1028.8 selinux问题分析过程和方法举例( Revisited),,1028.8.1实例一:用户无法在 console上正常登录-使用 strace定位失败操作1028.8.2实例二: sysadm r无法正确使用 useradd命令108SELinux开发笔记.…,,1149.1使能对/dev/ console的支持1149.1.1提出问题:20101213及之前的 epolicy缺乏对 conso1e的支持9.1.2分析问题··p9.1.3解决问题.1169.1.4测试结果1179.1.5使用 strace观察 consolo被重新打标签的细节(new),,,,1179.2 Socket labeling开发,1189.2.1提出问题: socket默认继承其创建者的SID的副作用,,,,,1189.2.2分析问题1199.2.3解决问题1199.2.4测试结果.,.1239.3给 role transition规则添加c1ass的支持,,..,,1249.3.1提出问题-当前 role transition规则只对 process类有效,,1249.3.2分析问题..,,,,,.1249.3.3解决问题D垂垂垂,,,,,1259.3.4测试结果,,,,,1319.3.5其他说明.1339.3.6经验总结●非春…1359.4增加 role attribute的攴持(new).,,,1369.4.1提出问题之一:roe- dominance规则的局限性1369.4.2提出问题之二:期望的 role attribute使用模型..1409.4.3分析问题1429.4.4解决问题D1439.4.5测试结果639.4.6一个有意思的编译问题,,,,1689.4.7有关role- types规则语法的讨论.,,.1719.5区分 tuna1e和 boolean(new).···1729.5.1提出问题无用的 tunable分支被写入 policy.X.729.5.2分析问题1739.5.3解决问题,,1749.5.4测试结果.1879.5.5其他经验总结9.N在策略中指定 newcontext的缺省设置方法(todo)1929.N.Ⅰ提出问颋- newconteκt的设置策略被硬编码到机制中19210. SeLinux内核驱动分析小记19410.1LSM核心数据结构及相应回调函数,19410.2 sELinux核心数据结构.19410.2.1 selinux对内核数据结构的扩展19410.2.1.1进程的安全属性19510.2.1.2文件和打开文件描逋符的安全属性.,,.,,,,,,..19510.2.1.3 socket的安全属性10.2.1.4文件系统超级块的安全属性1960.2,2AVC数据结构.19710.2.3內核 policy中保存TE规则的数据结构.,19910.2.4內核 policy中保存RBAC规则的数据结构.鲁鲁,,,,,20010.2.5 SeLinux规则在内核中的检查点总结(new)..,,,,,,20110.3情景分析:打开文件时的相关函数调用链20110.4通过 SEL inuxfs访问内核 Security Server,,,,,,,,,,,,,,20810.4.1/ selinux/load和1 oad policy命令一装载冰解析 policy.二进制文件20910.4.2/sc1inux/ relate1及 compute relabel命令-查询 type change规则21110.4.3/ selinux/ create及 compute create命令-查询type_ transition规则21110.4.4/ selinux/ member及 compute member命令-查询 type member规则.21210.4.5/ selinux/ access文件和 compute av命令-查询a11ow规则...21310.4.6/ selinux/user文件和 compute_user命令-查询用户登录后可能的SC21310.4.7/ selinux/ initial contexts/-查询 Initia1SI对应的安全上下文21410.4.8/ selinux/ class/-查询内核 class datum数拥结构(todo10.5情景分析: Domain transition的实现●··垂·看垂,,,,,,,,,,,,,,,,,,,,,21510.5.1 selinux setprocattr凼数-/proc/lpid/attr/“文件驱动21610.5.2 do execve的行为和相关 seLinux内核驱动垂垂看21810.6情景分析:文件系统的挂载和新文件的创建2110.6.1文件系统的挂载过程(new)..22110.6,2确定新创建文件的标签...23610.7 Context数据结构和u32sid之间的映射24110.7.1 sidtab node的定义和 sidtab的组织结构.24110.7.2 sidra_ insert函数- sidtab node的插入·,,,,,,,,,,,,,,24210.7.3 sidtab context to sid函数返回或分配sid..24310.7.4 security transition sid函数-计算新 subject/ object的sid....24410.7.5创建 context并注册到 sidtab以获得sid的时机.24910.7.6 security context to sid函数返回Sc字符对应的sid....25010.7.7 sidtab scarch corc囪数- sidtab node的查找,,,25110.7.8 security sid to context core函数-返回sid所对应的SC宇符串25210.8 Class Mapping..25410.8,1C1 ass mapping的作用..,,,,,25410.8,2 Class Mapping的创建垂垂垂·,,,,,,,,,,,,,,,,25410.8.3 Class mapping的使用-c1ass/perm内核态和用户态索引的转换.25710.8,4增加 class或者权限的方法25810.9和文件操作相关的回调数9. 1 selinux file mprotect回调函数25910.10和 AF UNIX SOCket相关的回调函数(todo),26310.11和程序执行相关的操作(todo).26410.11.1se1 inux bprm secureexec凼数-扩展 AT SECURE机制26410.11.1.1C库 AT SECURE机制介绍26410.11.1.2C库 AT SECURE机制演示26710.11.1.3 SELinux对 AT SECURE机制的扩展( Revisited).26911.用户态应用程序对 SeLinux的支持27211.11 selinux相关文件分析,27211.1.1 selinux config,c文件.,,27211.1.2 gelfilecon.c文件,,,,,27211.1.3 procattr.c文件.27211.1.4 compute relate1.c文件(访问/ selinux/ relate1)..27311.2 newrole源代码分析,27411.2.0 newrole命令的使用模型2742.1main函数7311.2.2 parse command linc arguments函数.,,,27611.2.3 relabel tty函数2761.3PAM模块分析..,27711.3.1 pam sC1inux.so作用分析(TODO27711.3.2pam1 oginuid,so作用分析,27811.3.3 pam name space.so作用分析.,27911.3.3.1多态( polyinstantiation)的作用,,,,,,,,,,,27911.3.3.2LSP对多态的配置,,,,,,,,,,,,,,28111.3.3.3 SELinux对 polyinstantiation的支持.,,,,28111.3.3.4解决在使能多态后 crond的使用间题28211.3.3.5 pam namespace,so源代码分析(IODO11.3.3.6有关 pam namespace.so的剩余问题8412. refpolicy的编译,链接,扩展,,,,,,,,,28512.1描朮标识符的数据结构8512.1.1 type datum t8512.1.2 common datum t12.1.3c1 ass datum t.,,,,,.,,,,.28612.1.4ro1 e datum t..,,,,,,曲D,.,28712.2描朮规则的数据结构..28812.2.1 AVTAB AV和 AVTAB TYPE类规则..,,,,28812.2.2 rolc transition规则●·垂,,,,,,,,,,,,,,,,,29012.3用户态 policy t数据结构分析.12.3.1 policy t数据结构综诚29012.3.2 symtab符号表.29412.3.3 avrule block t, avrule decl t FH scope stack t12.3.4 scope datum t-描迒标识符的定义者和使用者29712.3.5 scope index t-描逋一个b1ock/dec1内定义或引用的标识符.29712.3.6 cond node t-描朮一个ir- else conditiona29812.4 module的编译- checkmodu1e..30112.4.1编译过程核心数拥结构关系图30112.4.2 define policy- policy module词法分析....30212.4.3 begin optional- optional_ policy词法分析30412.4.4 declare type-type标识符的定义,,30312.4.5 require type-声明对type标识符的外部依赖31512.4.6 define te_ arab-TE规则的词法分析..31812.4.7 define role_ trans- role transition规则的词法分析32412.4.8 define conditional-if- else conditiona1的词法分析.2912.5 module的链接- semodule1ink.12.5.1链接过程核心数据结构关系图34012.5.2 symtab符号表的拷贝...,,,,,,34112.5.2.1 p types符号表的拷贝,,..34112.5.2.2所有其他标识符符号表的拷贝,,,,,,,,,,,,,,34412.5.2.3 p roles符号表的修正12.5.3 Scope符号表的拷贝34912.5.4链接过程的主要囪数调用链12.6 module的扩展- semodule_ expand37012.6.1 expand过程核心数据结构关系图..37012.6.2type的拷贝..37112.6.3 common的拷贝,,,37412.6.10 expand过程的核心函数调用链,.,,,37612.6.11展开规则的“字面”描诚- copy and expand avrule block囪数..38312.71ink和 expand过程的图解(new),,,,,,,,40012.7.1Role/ attribute标识符的1ink和 expand..…………40012.7.2 symtab的1ink和 expand,,,,,,403128规则中的m4宏定义(new)..,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,40513. seLinux的应用41013. 1 Labeled Networking (half-baked),,,,,,,,,,,,,,,,,,,,,,,41013.1.1 IPsec简介,,,,,41013.1.2 seLinux对本地网络的控制( compat-net),,,,,,。,,,,,,,41613.1.3用 Labeled ipsec实现分布式网络控制..41713.1.4 Linux內核ⅹIM相关数据结构.41813.1.5和 IPsec相关的类,权限和援囗D41813.1.6LSM中和 Labeled ipsec相关的回调函数,41913.1.6.1检查一个f1ow(发送或接收)能否使用一个SPD条目41913.1.6,2给SPD/SAD分配安全属性.,,,42113.1.6.3释放SPD/SAD中的安全属性,,,,,,,,,,,,,,,.42413.1.6.5逐包检查一个 socket能够接收一个skb42413.1.6,4获取发送方的安全上下文字符串..,,4231.7 Labeled ipsec环境的搭建.13.1.8观察 Labeled ipsec的行为43013.1.9和 Labeled ipscc相关的 SeLinux规则,432参考文献434简化 selinux操作的bash配置方法本文档各个版本的说明437注第1至5章包含自己对《 SELinux By example》一书的学习心得;第6至9章包含自己实际经验的总结第10和11章为 selinux内核和用户态源代码分析总结第12章为 refpolicy的编译过程源代码情景分析;第13章打算收录些 SeLinux在内核或者用户态的应用,比如 Labeled Networking,XACl等。l, Refpolicy有300+个p的实现,了解核心pp的实现,必须首先了解应用程序的行为以及安全目标2,阅读 sELinux- aware应用程序源代码,看如何使用 libselinux库函数,学习 sELinux用户态编程3,了解 sELinux语法,标识符的二进制表示形式,内核态和用户态的数据结构;4,学习 policy module的 compile/ expansion/1ink过程5,按照类别,逐步掌握LSM回调囪数的调用时机,所在内核子系统的原理,以及 SELinux对LSM回调函数的实现(参考《 Implementing sElinux as a lsm module》一文)6,掌握 seLinux对各个内核子系统核心数据结构的扩展7,学习XAC规范,体会如何开发 Userspace Ob、 ject Manager;8,积极阅读 Joshua,Dan等人的b1og,向前奉们学与。9,积极关注 selinux邮件列表上的问答和讨论,丰富自己的视野希望能通过自己坚持不懈的努力,证得同满的 sELinκ知识和智慧。引子1,软件的缺陷不可避免(无论过去,现在,或将来);2,没有底层操作系统的支持就无法真正实现上层软件的安全性D. Baker,《 Fortresses Built Upon Sand》操作系统中访问控制模型的演化1.1访问控制模型的概念( Reference moni tor)subjectsAccessobjectsAlertYes or No?Feference validation MechanismRuleelampcrpra吋DBVerifiableRY M由上图可见,访问控制模型由如下四部分组成1, Subjects:访间的发起者,比如系统中的进程2, Objects:被访闩的对象,比如架作系统所管理的仼何资源丶数捃(包拈进程,任意类型文件,Tc尸端口,甚至单个网络报文。总而言之,任何内核数据结构都可能成为被访问的对象)3, Rules de:规则库,在用户态实现的访问策略,定义 Object的属性并规定哪些Sub、ect可以通过什么样的方式对它进行访问;4,RVM( Reference validation mechanism):在操作系统内实现的机制,是汸问控制策略的执行者,在访问操作过程中根据规则库判断当前操作是否合法;Hinx首先需要标识访问者和被访问的对象,由下文可知相关信息保存在进程的 task struct以及其他内核数据结构中 security指针所指向的数据结构中(注意这些数据结构都是运行时动态创建的,安全属性信息来源于文件在辅存上的扩展属性,以及规则库中的 Initia1S1定义等)。白用户态定义的访问规则库指定哪些访闩老能够以何种方弌访问哪些对象,而内核屮的SεLix机制则根据当前操作的访问者和被访问对象,查询规则库得到Yes/No结论。1.2DAC( Discretionary Access Contro1)的致命伤¨ discretionary”一词的含义为“ not contro1 led bv strict rules, but decided on by someonein a position of authority”,所以DAc的本质是由文件的属主定义其它用户对该文件的许可访问方式,其“ owner-group-wor ld”模型如下:S 1s -1 /usr/bin/passwdrwsr-xr-x I rootroot 37084 2009-04-04 13: 49/usr/bin/passwd系统中所有文件属主给各自文件所定义的“ owner-group-wor d”模型的总和,即为DAC下访问规则库的实现。DAC的开发环境(相对封闭的开发社区,或大学实验室)和对软件使用环境的假设(软件没有缺陷且运行环境友好)注定了DAC存在着天生缺陷:进程和文件的安全属性都基于(且总是基于)uid/euid和gid/egid,无论进程执行什么应用程序,其uid/euid都不改变(暂不考虑 setuid类程序),无法将进程所执行程序的行为和可靠性(安全性)标识到进程的安全属性中,导致操作系统无法有针对性地对进程施加访问控制比如,用户登录 shell进程会创建子进程以执行shel1的外部命令,子进程继承父进程的uid/gid,所以无法通过uid/gid来区分父子进程,即无法区分用户人为的操作和通过程序执行的操作。比如,无法限制 passwd程序只能被用户在命令行执行,而不能被属于该用户的其它进程执行。显然,“用户(登录hc11进程)是可信的”绝对不等于“用户执行的程序(后继fork的子进程)也是可信的”。登录sh1进程的行为由用户有意识地支配,而属于该用户的进程的行为则由其执行的实际程序决定。但是程序可能冇在安全漏洞,一巨被攻击植入恶意代码,黑客将具有该用户在系统上的所有权力(比如恶意删除用户的文件,盗取uid/gid所能读取的文件的内容,执行 passwd程序修改用户的密码)另外,用户进程可以执行各种应用程序,而这些程序自身的行为丶对系统安仝性的景响都不尽相同,比如网络类应用程序更容易受到外界病毒的攻击,相应地操作系统应该对此类应用施加更为严格的访冋控制。显然无法通过进程的uid/gid来描当前进程所执行的程序的安全性,因此操作系统也无法有针对性地实施访问控制。综上所逋,仪将uid/gid来作为进程和文件的安全属性是远远不够的最后,DAC的另一个缺点是对权力的管理和划分不够细致(只有两种情况:root或non-root),无法进步细分丶限制root用户的能力。一旦euid/ egid为0的进稈被攻破,将危害整个系统的安全1.3MAC( Mandatory access Contro1)的起源针对DAC的缺点,在ⅥAC中不再由访问对象的属主定义不同用户对其的许可访问方式,而是由匿定的规则库决定。MAC最初的研究由美国军方的MLS(u1ti- Leve1 Security)应用所推动,它将访问主体和被访问对象分成不同的安全级别,严格控制信息只能从低安全级别向高安全级别流动:低安全级别的丰体只能向高安全性的数捃对象中追加新的数据,并∏禁上读取;高安全级别的主体能够读取低安全级别的数据,并且禁止任何形式的写入(即“ no read up, no write down”)ⅥS只定位于数据保密性而并不关心数据完整性和最小权能原则( east, Privilege),以及对进程的能力进行分类。后来的FASK安全系统模型着眼于解决这些不足,而 SELinux则是FASK在 Linux内核中的实现1.4 Selinux的TE( Type Enforcement)模型SELinux作为MAC的一和实现,通过中央规则库( policy.x,二进制数据文件)给所有进程丶所有文件内核数据结构定义各自的安全标识(标签,1abel/type),明碓定义被访问对象所支持的访问方式,并规定进程标签对被访问对象的合法的访问方式。在配置 SELinux时给整个文件系统上的所有文件设置标签,在系统启动过程中init进程经由 selinux接口装载 policy.X到內核空间,由內核中的 SecuritvServer在处理用户态系统调用时实时査询(注,这里所说的“ Security server”,即为 sELinux内核驱动中定义的各种数据结构,比如 sistah, policy, AVC cache,以及在 services.c文件中定义的各种以“ security”开头的函数)

很不错的图像融合程序，通过多个算法实现图像融合。程序中有例图，测试通过。

java dvd影碟管理系统 swing界面