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Unix/Windows Inter-Operability

Unix/Windows Inter-Operability. What do we want?. Single Username Password Access Users files (N drive) Personal Machine Multi-User Machines Information about users Name Service Simple Client Setup Multiple Namespaces?. UNIX files. /etc/ passwd User account information

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Unix/Windows Inter-Operability

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  1. Unix/Windows Inter-Operability

  2. What do we want? • Single Username Password • Access Users files (N drive) • Personal Machine • Multi-User Machines • Information about users • Name Service • Simple Client Setup • Multiple Namespaces?

  3. UNIX files • /etc/passwd • User account information • Name:DES#:uid:gid:DisplayName:homedir:shell • /etc/group • Group information and membership • Name:[hash]:gid:user1,user2... • /etc/hosts .... • Files are readable by all users

  4. DES Encryption • Encrypt 64bit 0 25 times using 12bit salt and 8 7bit character password (56bit). • Designed to take 1 second on 1979 hardware. Brute force ~ 23,000,000,000 years. • Only 94 characters on keyboard ~54.2bits • Moore’s law • 500,000 per sec ~4500 years. • Dictionary attack takes only minutes

  5. Shadow File • Remove DES # from public passwd file • Shadow file only access by local root • Add account management for password change frequency, expiry, etc

  6. Yellow Pages (aka NIS) • Service on the network based on maps containing key-value pairs • Add + at the end of files in /etc • All machines in the same namespace see the same information. • Central management of user accounts etc. • Information now visible to all users on any machine on the network.

  7. LDAP • Lightweight Directory Access Protocol • General mechanism • Schema used to define objects • Objects have named attributes • Objects can be extranded • Can require authentication to connect • Can secure individual objects

  8. LDAP vs NIS • ypmatch –d rucsc 11420 passwd.byuid sssadw:x:11420:11203:Anthony Worrall:/home/sufs1/ru10/ss/sssadw:/bin/csh • ldapsearch -h host -b "ou=people,dc=sse,dc=rdg,dc=ac,dc=uk" uidNumber=11420 uid=sssadw,ou=People,dc=sse,dc=rdg,dc=ac,dc=uk cn=Anthony Worrall mail=Anthony.Worrall@Reading.ac.uk uid=sssadw givenName=Anthony sn=Worrall objectClass=person objectClass=organizationalPerson objectClass=inetOrgPerson objectClass=dspswuser objectClass=account objectClass=posixAccount objectClass=shadowAccount objectClass=top loginShell=/bin/csh uidNumber=11420 gidNumber=11203 homeDirectory=/home/sir/sssadw gecos=Anthony Worrall

  9. nsswitch.conf • Controls where each nameservice gets its information passwd: files ldap group: compat hosts: nisdns [NOTFOUND=return] files netgroup: nis • Compat allows +/-[@netgroup] syntax in files • getent instead of ypmatch an ldapsearch

  10. Kerberos • An Authentication Service (KDC) • Obtian a ticket (Passport) at login • Use ticket to access other services. • Can also be used to authenticate clients, services, and encrypt traffic • Based on principals “username@realm” • Realms can have a trust relationship • Pre-authentication need for security

  11. Kerberos client tools • kint • Get ticket for a prinicpal using information from user input or file • klist • List principals for current user or stored in a file • kdestroy • ktutil • Mange princiapls in a keytable files

  12. Pluggable Authentication Modules • Stack of modules in 4 contexts • Auth: User authentication • Account: password/account expiry etc • Session: session management e.g. logging • Password: how to change password etc. • Each service such as login, ftp etc can have its own stacks

  13. Configuring Linux in SSE • LDAP Settings LDAP Server : sse.ad.rdg.ac.uk Search Base : ou=unix,dc=sse,dc=ad,dc=rdg,dc=ac,dc=uk Group member attribute : member • Kerberos Settings Default Domain : rdg.ac.uk Default Realm : RDG-HOME.AD.RDG.AC.UK KDC : rdg-home.ad.rdg.ac.uk

  14. Name Service Cache Deamon • NSCD save results of NameService requests including DNS lookups • Some services on multiple machines • rdg-home.ad.rdg.ac.uk • timehost.rdg.ac.uk • Modify /etc/nscd.conf • enable-cache hosts no

  15. Authentication vs Authorization

  16. Options of Integration • AD Kerberos Authentication, UNIX name service • AD Kerberos Authentication, AD name service • AD LDAP Authentication, UNIX name service • AD LDAP Authentication, AD name service • UNIX Kerberos with cross realm trust for authentication and UNIX name service

  17. Option Requirements

  18. 1. AD Kerberos Auth, UNIX NS • Pros • Same username/password • Existing name service • Single Sign On available • Cons • Need to maintain UNIX NS

  19. 2a. AD Kerberos, AD NS • Pros • Single username/password • Single Name Store • 2003R2 supports RFC 2307 (homeDirectory?) • Cons • Need to extend “user” class • Map Classes and Attributes on clients

  20. 2b. AD Kerberos, AD NS separate OU • Pros • Only need AD DC’s • Looks like UNIX OpenLDAP to clients (RFC 2307) • Allows Multiple Name Spaces • Cons • Need to promote PosixAccount Class • Synchronise information between OU

  21. 3. AD LDAP Auth, UNIX NS • Pros • Same username/password • Existing name service • Cons • Need to maintain UNIX NS • No Single Sign On

  22. 4. AD LDAP Auth, AD NS • Pros • Only need AD DC’s • Cons • Need to extend users class or promote PosixAccount class • No Single Sign On • Need Proxy User to access NS

  23. 5. Cross Realm Trust • Pros • Native Tools • User Prinicpals in AD, Unix Services and Hosts Prinicpals in Unix Kerberos • Cons • Extra complication

  24. Authentication Kerberos AD LDAP Pros Simple Used by web backends (PHP, Perl), Apache Module Cons need to secure connection Modify pam.conf • Pros • Single Sign On to services • Apache Module • Authenticate services • Cons • Host and Service Prinicples • Modify • krb.conf • pam.conf • krb5.keytab

  25. AD as NS Extend user class Promote PosixAccount Pros Looks like UNIX OpenLDAP to clients Allows Multiple Name Spaces Cons Synchronise information between OU • Pros • Single object to maintain • Cons • Map objects and attributes on client (e.g. uid => sAMaccountName )

  26. Unix Name Service LDAP NIS Pros Simple Configuration by DHCP Cons World readable • Pros • Out of the BOX • Can be restricted • Cons • Complicated • Proxy User on clients if restricted

  27. Network File System • Mount directory from server on client (c.f. map network share) • Host based security • Client does authorization by user/group

  28. NFS V4 • Server side authorization • NTFS like Access Control Lists • Kerberos Support • Authentication • Integrity • Encryption • Client Prinicpal need to allow root to mount filesystem

  29. smbmount • Mount folder from Windows server using cifs protocol • Single username and group mapping • Need root access (sudo) to do mount • Requires username and password on command line, in a file or user input.

  30. LUFS/FUSE • Allows normal user to mount “filesystem” • Present sftp connection as filesystem • Other backends available • Similar problems to smbmount • Performance issues?

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