“UbuntuHelp:ActiveDirectoryHowto”的版本间的差异

2007年11月22日 (四) 11:58的版本

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Active Directory

Active Directory from Microsoft is a directory service that uses some open protocols, like Kerberos, ldap and SSL.

There are several ways to use AD for authentication, you can use pam_krb5, LDAP or winbind. For Winbind see [ActiveDirectoryWinbindHowto].

Kerberos: pam_krb5

Configuration and Installation

To install pam_krb5 you need to install krb5-user and libpam-krb5 from the Universe Repository. Also you don't have to configure anything in Active Directory for pam_krb5.

Then to setup pam_krb5 go to /etc/krb5.conf and open it up using your favorite text editor.

[logging]
default = FILE:/var/log/krb5lib.log

[libdefaults]
ticket_lifetime = 24000
default_realm = EXAMPLE.COM
default_tkt_enctypes = des3-hmac-sha1 des-cbc-crc
default_tgs_enctypes = des3-hmac-sha1 des-cbc-crc

[realms]
EXAMPLE.COM = {
kdc = windc.example.com
admin_server = windc.example.com
default_domain = example.com
}


[domain_realm]
.example.com = EXAMPLE.COM
example.com = EXAMPLE.COM

You need to replace windc.example.com with the IP or FQDN of your Windows domain controller and EXAMPLE.COM with your kerberos realm, typically is this the domain name in uppercase.

Then try to see if you can receive a kerberos ticket:

# kinit user
Password for [email protected]: ...

# klist
Ticket cache: FILE:/tmp/krb5cc_1003
Default principal: [email protected]

Valid starting     Expires            Service principal
11/26/04 11:23:53  11/26/04 21:23:53  krbtgt/[email protected]


Kerberos 4 ticket cache: /tmp/tkt0
klist: You have no tickets cached

Then you need to set up /etc/pam.d/common-auth and then

auth    sufficient      pam_krb5.so ccache=/tmp/krb5cc_%u
auth    sufficient      pam_unix.so likeauth nullok use_first_pass
auth    required        pam_deny.so

set up /etc/pam.d/common-session.

session required        pam_unix.so
session required        pam_mkhomedir.so skel=/etc/skel/ umask=0077

kpasswd for password changing does not work.

The user from AD have to exist in /etc/passwd on the ubuntu workstation, you can also use libnss-ldap to get the account info also from AD.

LDAP

TestQuery: Windows

Assuming you do not maintain the Active Directory, You will want to determine the structure of AD before trying to connect to it from Linux. From a windows PC connected to AD you should perform a query using Microsoft's Active Directory Application Mode (ADAM). ADAM is a package of tools that includes CSVDE, which we will be using to perform our queries.

Type this into google, the download page should be the second hit.

adam microsoft

Install. Open the command prompt. Start>RUN and type 'cmd' Navigate to the installation directory, default is c:\windows\ADAM

Example Queries: Query a user entry

CSVDE -f export.csv -r "(&(objectClass=user)(sn=lastname))"

wildcards work as well

CSVDE -f export.csv -r "(&(objectClass=user)(sn=last*))"

Query a computer entry

CSVDE -f export.csv -r "(&(objectClass=computer)(cn=computername))"

Return everything in the following AD folder

CSVDE -d "OU=Pathology,OU=Departmental OUs,OU=Medcenter,DC=Med,DC=University,DC=edu" -f export.csv

The output of these queries would be placed within export.csv inside c:\windows\ADAM. Which can then be viewed as a spreadsheet editor.

For more on querying with ADAM's CSVDE [www.computerperformance.co.uk/Logon/Logon_CSVDE.htm]

Configure AD

In Windows Server versions prior to WS03 R2, it is necessary to extend the LDAP schema from AD with the UNIX attributes. Install "Windows Services for UNIX" from Microsoft (I used version 3.5). SFU: http://www.microsoft.com/windows/sfu/

Installing SFU 3.5 on Windows Server 2003 (non R2) does not appear to add the necessary LDAP schema extensions.

In order to extend the LDAP schema, it is necessary to install the "Server for NIS" component. The installation needs to be performed using an account that has Enterprise Admin privileges in order for the schema to be extended successfully (indeed, Enterprise Admin privileges are required even if the schema has already been extended). In Active Directory, schema extensions are non-reversible, so if the NIS Server is not required, it can be removed once the schema extension is complete. If the SFU Server for NIS is installed however, it will extend the Active Directory Users and Computers tool with a UNIX Attributes tab which allows GUI editing of the UNIX attributes for users, groups and computers.

In Windows Server 2003 R2, the Active Directory schema is already extended with an RFC2307-compliant schema. This differs from the schema extensions used in SFU3.5, requiring a different libnss-ldap configuration. It is still necessary to install Server for NIS to extend the Active Directory Users and Computers tool with the UNIX Attributes tab to allow GUI editing of UNIX attributes for users, groups and computers.

TestQuery: Linux

We will want to perform a testquery in linux before we attempt to configure AD. Its much simpler to determine how to connect on the commandline, and then configure, rather than reconfigure a file repeatedly.

We will need at least these two packages to perform test queries on Active Directory.

sudo apt-get install libnss-ldap ldap-utils

We perform queries with 'ldapsearch' We must specify these minimum parameters:

We need to specify the LDAP Server (Domain Controller)

ldapsearch -h medcenterdc01

and the authentication type: simple or SASL

SASL authentication off, simple on

ldapsearch -h medcenterdc01 -x

and the folder we want to search in

ldapsearch -h medcenterdc01 -x -b "OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu"  

and who to authenticate as

ldapsearch -h medcenterdc01 -x -b "OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu" -D "CN=last name\\, firstname,OU=Users,OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu"  

we'll have it prompt for the password, instead of specifying it in the command

ldapsearch -h medcenterdc01 -x -b "OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu" -D "CN=last name\\, firstname,OU=Users,OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu" -W  

and lets search for sammy's account

ldapsearch -h medcenterdc01 -x -b "OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu" -D "CN=last name\\, firstname,OU=Users,OU=Pathology,OU=Departmental OUs,OU=medcenter,DC=mc,DC=university,DC=edu" -W "sAMAccountName=sammy"  

One doesn't need to worry about spaces, but to specify a comma as part of the path we need to prefix the comma with '\\'

CN=last name\\, firstname

libnss-ldap

You can install libnss-ldap and nscd from the Universe Repository.

Now you need to set up /etc/nsswitch.conf for ldap.

passwd:         compat
group:          compat
shadow:         compat
passwd_compat:  ldap
group_compat:   ldap
shadow_compat:  ldap

hosts:       files dns
networks:    files dns

services:    db files
protocols:   db files
rpc:         db files
ethers:      db files
netmasks:    files
netgroup:    files
bootparams:  files

automount:   files
aliases:     files

If you have trouble when you attempt to ping and your network has a wins server you will want to append 'wins' to the hosts line of nsswitch.conf - you may only notice this only when you try to ping a static ip linux pc from another linux pc - I believe wins is a part of the samba package and the IP addresses for wins servers are stored in /etc/samba/dhcp.conf, the static ip machine also needs to specify its netbios name within /etc/samba/smb.conf

When fiddling with /etc/nsswitch.conf, it is best to turn the Name Services Caching Daemon off - /etc/init.d/nscd stop or you will be confused by cached results. Turn it on afterwards.

Then you need to set up /etc/libnss-ldap.conf. AKA: /etc/ldap.conf

# Replace windc.example.com with your Windows DC
uri ldap://windc.example.com/

base dc=example,dc=com
ldap_version 3

# Add a user to AD, that can read the container
# with the users, that you want use.
binddn cn=ldapreader,cn=Users,dc=example,dc=com
bindpw cvfd123

scope sub
timelimit 30


pam_filter objectclass=User

pam_login_attribute sAMAccountName
pam_lookup_policy yes

# Modify cn=User,dc=e... to your container with your users.
nss_base_passwd cn=User,dc=example,dc=com?sub
nss_base_shadow cn=User,dc=example,dc=com?sub
nss_base_group  cn=User,dc=example,dc=com?sub

# For MSSFU:
nss_map_objectclass posixAccount User
nss_map_objectclass shadowAccount User
nss_map_attribute uid sAMAccountName
nss_map_attribute uniqueMember member
nss_map_attribute uidNumber msSFU30UidNumber
nss_map_attribute gidNumber msSFU30GidNumber
nss_map_attribute userPassword msSFU30Password
nss_map_attribute homeDirectory msSFU30HomeDirectory
nss_map_attribute loginShell msSFU30LoginShell
nss_map_attribute gecos name
nss_map_attribute cn sAMAccountName

I think it only needs rootbinddn, no binddn, with the bindpw in /etc/libnss-ldap.secret, not here. I have also successfully combined /etc/ldap/ldap.conf, /etc/libnss-ldap.conf, and /etc/pam_ldap.conf, symlinking them all to /etc/ldap/ldap.conf - AndyRabagliati

Incorrect nss_map settings will prevent one from authenticating, and reading AD in general. These settings are dependent on the column names within your AD database. In older systems the database (schema) needs to be extended as described in the 'Configure AD' section. Once these *NIX attributes are part of the schema they can be modified with the MMC snap-in Active directory Users and Groups, as long as idmu.exe has been installed from the Windows Server 2003 R2 Administration Tools Pack. If *NIX group membership has been administered by modifying the list in the UNIX attributes tab of AD Users and Computers (which is REQUIRED in a NIS environment), then 'uniqueMember' should be mapped to 'msSFU30PosixMember' (or 'posixMember' for WS03R2) as 'member' only includes the membership listed in the Windows group. For Windows Server 2003 R2, the schema extensions are RFC2307 compliant - no longer prefixed 'msSFU30' and with the next letter in lower case (e.g. msSFU30UidNumber is now uidNumber).

Further optimizations of the queries can be made for the nss_base properties:

nss_base_passwd		dc=mydomain,dc=com?sub?(&(objectClass=user)(uidnumber=*))
nss_base_shadow		dc=mydomain,dc=com?sub?(&(objectClass=user)(uidnumber=*))
nss_base_group          dc=mydomain,dc=com?sub?(&(objectClass=group)(gidnumber=*))


The ampersand in the queries above merely specifies AND logic

AND (&(filter)(filter))
OR  (|(filter)(filter))
NOT (!(filter)(filter))

Debugging

To debug LDAP queries one should make sure nscd is off and use the getent command

sudo /etc/init.d/nscd stop

getent passwd
getent shadow
getent group

To follow the actions of the command use strace

strace getent passwd

If thats not enough you can place a line in the configuration file for output:

debug 10

This can be a value anywhere from 1 to 10, 10 being the most verbose.

With this config is the LDAP Traffic unencrypted and someone can sniff it. To make it secure use SSL

Now you need to set up /etc/pam.d/common-auth and

#
# /etc/pam.d/common-auth - authentication settings common to all services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of the authentication modules that define
# the central authentication scheme for use on the system
# (e.g., /etc/shadow, LDAP, Kerberos, etc.).  The default is to use the
# traditional Unix authentication mechanisms.
#
auth    sufficient      pam_ldap.so
auth    required        pam_unix.so nullok_secure use_first_pass

set up /etc/pam.d/common-account.

#
# /etc/pam.d/common-account - authorization settings common to all services
#
# This file is included from other service-specific PAM config files,
# and should contain a list of the authorization modules that define
# the central access policy for use on the system.  The default is to
# only deny service to users whose accounts are expired in /etc/shadow.
#
account sufficient      pam_ldap.so
account required        pam_unix.so

We are still using Kerberos for authentication, but now we are storing the information that would normally be stored in /etc/passwd using Active Directory.

Here are some other useful config files:

• • • login.defs

• • • nscd.conf