linux系统对密码复杂度的控制机制

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1、linux系统对密码复杂度的控制机制我们在使用linux系统设置密码的时候，经常遇到这样的问题，系统提示：您的密码太简单，或者您的密码是字典的一部分。那么系统是如何实现对用户的密码的复杂度的检查的呢？系统对密码的控制是有两部分（我知道的）组成：1cracklib2login.defs声明：login,defs主要是控制密码的有效期。对密码进行时间管理。此处不细谈login,defs一一shadowpasswordsuiteconfigurationpam_cracklib.so才是控制密码复杂度的关键文件rcdhat公司专门开发了cracklib这个安装包来判断密码的复杂度可以rp

2、m-qlcracklib查看密码的复杂度的判断是通过pam模块控制来实现的，具体的模块是pam_cracklibpam_cracklib的参数介绍：debugThisoptionmakesthemodulewriteinformationtosyslog(3)indicatingthebehaviorofthemodule(thisoptiondoesnotwritepasswordinformationtothelogfile).type=XXXThedefaultactionisforthemoduletousethefollowingpromptswhenrequesting

3、passwords:〃NewUNIXpassword:"and〃RetypeUNIXpassword:ThedefaultwordUNIXcanbereplacedwiththisoption.retry=NPromptuseratmostNtimesbeforereturningwitherror.Thedefaultis1difok=NThisargumenlwil1changethedefaultof5forthenumberofchciractersinthenewpasswordthatmustnotbepresentintheoldpassword.Inaddition

4、,if1/2ofthecharactersinthenewpasswordaredifferentthenthenewpasswordwillbeacceptedan)^vay.difignore二NHowmanycharactersshouldthepasswordhavebeforedifokwillbeignored・Thedefaultis23.minlen=NTheminimumacceptablesizeforthenewpassword(plusoneifcreditsarenotdisabledwhichisthedefault).Inadditiontothenu

5、mberofcharactersinthenewpassword,credit(of+1inlength)isgivenforeachdifferentkindofcharacter(other,upper,loweranddigit).ThedefauItforthisparemeteris9whichisgoodforaoldstyleUNIXpasswordal1ofthesametypeofcharacterbutmaybetoolowtoexploittheaddedsecurityofamd5systcm.Notethatthereisapairoflongthlimi

6、tsinCracklibitself,a"waytooshort"limitof4whichishardcodedinandadefinedlimit(6)thatwillbecheckedwithoutreferencetominlen.Ifyouwanttoallowpasswordsasshortas5charactersyoushouldnotusethismodule.dcredit=N(N>=0)Thisisthemaximumcreditforhavingdigitsinthenewpassword.IfyouhavelessthanorNdigits,eachdig

7、itwillcount+1towardsmeetingthecurrentminlenvalue.Thedefaultfordcreditis1whichistherecommendedvalueforminlenlessthan10.(N<0)Thisistheminimumnumberofdigitsthatmustbemetforanewpassword.ucredit=N(N>=0)Thisisthemaximumcreditforhavinguppercas