From Linux NFS

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Revision as of 04:35, 20 July 2011

This is a WIP by dros@netapp.com - please let me finish before changing/commenting).

This document describes using NFSv4 with FreeIPA.

Historically, setting up a secure NFSv4 export (or even a client) was challenging, requiring the setup of a Kerberos realm and possibly an LDAP server. FreeIPA provides a packaged service of both Kerberos 5 and LDAP with the purpose of making this process much less painful.

These instructions are for Fedora 15. Other distros will require similar setup - the key differences will be a package installation tool other than yum(1), and a different config file layout.

1 Disclaimer about the testing environment
2 Notes
3 Configure DNS realm
4 Install and configure the FreeIPA server
- 4.1 Install the FreeIPA server and admintools package
- 4.2 Configure FreeIPA server
5 Install and configure FreeIPA client(s)
6 Add FreeIPA NFS service for each host
7 Turn on "Secure NFS" on both client(s) and server
8 Each host must have it's full DNS name in /etc/hosts
9 Set up /etc/exports on the server
10 Allow Kerberos to use "weak crypto"
11 Mount the filesystem
12 Test the NFS mount as another user
- 12.1 Add another user
- 12.2 Test NFS on client

Disclaimer about the testing environment

This example uses a private network (192.168.56.0/24) with a fake DNS realm (example.fake). For simplicity, this domain only has one server (server.example.fake) and one client (client1.example.fake).

Notes

This example is running on a NAT'd private network, so I just turned off the firewall on the server! You probably shouldn't do that! You'll need to allow traffic on:
- port 53 for named
- port 88 for kerberos
- port 389 for ldap
- XXX MORE!! (ipa web interface, etc?)

XXX maybe just add firewall config to instructions?

For the following example, I'm logged in as root on both the client and server. Either login as root or prepend "sudo " to each command.

Configure DNS realm

You might not need to do this.

If you're just setting up a client of FreeIPA, you can skip this section entirely.

If you already have a name server running for your domain:

make sure the full DNS names and reverse mappings for server(s) and client(s) are in DNS.

[root@client1 ~]# nslookup server.example.fake
Server:		192.168.56.20
Address:	192.168.56.20#53

Name:	server.example.fake
Address: 192.168.56.20

[root@client1 ~]# nslookup 192.168.56.20
Server:		192.168.56.20
Address:	192.168.56.20#53

20.56.168.192.in-addr.arpa	name = server.example.fake.

[root@client1 ~]# nslookup client1.example.fake
Server:		192.168.56.20
Address:	192.168.56.20#53

Name:	client1.example.fake
Address: 192.168.56.40

[root@client1 ~]# nslookup 192.168.56.40
Server:		192.168.56.20
Address:	192.168.56.20#53

40.56.168.192.in-addr.arpa	name = client1.example.fake.

add the service entries for FreeIPA auto discovery. They are of the form:

; DNS auto discovery of services
_ldap._tcp      SRV 10 10 389 server.example.fake.
_kerberos._udp  SRV 10 10 88 server.example.fake.
_kerberos._tcp  SRV 10 10 88 server.example.fake.

If you are setting up a fake domain for testing, follow these instructions:

Create a fake DNS realm for testing

Install and configure the FreeIPA server

Install and configure the FreeIPA software on the server (server.example.fake).

Install the FreeIPA server and admintools package

This step fetches and installs FreeIPA and it's dependencies. It will install around 100 packages, depending on what you already have installed.

[root@server ~]# yum install freeipa-server freeipa-admintools

Configure FreeIPA server

Run the ipa-server-install program. This takes a while.

All of the default answers should work if DNS hostnames and services are set up correctly and the full domain name is returned by hostname(1).

[root@server ~]# ipa-server-install 

The log file for this installation can be found in /var/log/ipaserver-install.log
==============================================================================
This program will set up the FreeIPA Server.

This includes:
  * Configure the Network Time Daemon (ntpd)
  * Create and configure an instance of Directory Server
  * Create and configure a Kerberos Key Distribution Center (KDC)
  * Configure Apache (httpd)

To accept the default shown in brackets, press the Enter key.

Enter the fully qualified domain name of the computer
on which you're setting up server software. Using the form
<hostname>.<domainname>
Example: master.example.com.


Server host name [server.example.fake]: 

The domain name has been calculated based on the host name.

Please confirm the domain name [example.fake]: 

The IPA Master Server will be configured with
Hostname:    server.example.fake
IP address:  192.168.56.20
Domain name: example.fake

The kerberos protocol requires a Realm name to be defined.
This is typically the domain name converted to uppercase.

Please provide a realm name [EXAMPLE.FAKE]: 
Certain directory server operations require an administrative user.
This user is referred to as the Directory Manager and has full access
to the Directory for system management tasks and will be added to the
instance of directory server created for IPA.
The password must be at least 8 characters long.

Directory Manager password: 
Password (confirm): 

The IPA server requires an administrative user, named 'admin'.
This user is a regular system account used for IPA server administration.

IPA admin password: 
Password (confirm): 


The following operations may take some minutes to complete.
Please wait until the prompt is returned.

Configuring ntpd
  [1/4]: stopping ntpd
  [2/4]: writing configuration
  [3/4]: configuring ntpd to start on boot
  [4/4]: starting ntpd
done configuring ntpd.
Configuring directory server for the CA: Estimated time 30 seconds
  [1/3]: creating directory server user
  [2/3]: creating directory server instance
  [3/3]: restarting directory server
done configuring pkids.
Configuring certificate server: Estimated time 6 minutes
  [1/17]: creating certificate server user
  [2/17]: creating pki-ca instance
  [3/17]: restarting certificate server
  [4/17]: configuring certificate server instance
  [5/17]: restarting certificate server
  [6/17]: creating CA agent PKCS#12 file in /root
  [7/17]: creating RA agent certificate database
  [8/17]: importing CA chain to RA certificate database
  [9/17]: restarting certificate server
  [10/17]: requesting RA certificate from CA
  [11/17]: issuing RA agent certificate
  [12/17]: adding RA agent as a trusted user
  [13/17]: fixing RA database permissions
  [14/17]: setting up signing cert profile
  [15/17]: set up CRL publishing
  [16/17]: configuring certificate server to start on boot
  [17/17]: restarting certificate server
done configuring pki-cad.
Configuring directory server: Estimated time 1 minute
  [1/32]: creating directory server user
  [2/32]: creating directory server instance
  [3/32]: adding default schema
  [4/32]: enabling memberof plugin
  [5/32]: enabling referential integrity plugin
  [6/32]: enabling winsync plugin
  [7/32]: configuring replication version plugin
  [8/32]: enabling IPA enrollment plugin
  [9/32]: enabling ldapi
  [10/32]: configuring uniqueness plugin
  [11/32]: configuring uuid plugin
  [12/32]: configuring modrdn plugin
  [13/32]: enabling entryUSN plugin
  [14/32]: configuring lockout plugin
  [15/32]: creating indices
  [16/32]: configuring ssl for ds instance
  [17/32]: configuring certmap.conf
  [18/32]: configure autobind for root
  [19/32]: restarting directory server
  [20/32]: adding default layout
  [21/32]: adding delegation layout
  [22/32]: adding replication acis
  [23/32]: configuring user private groups
  [24/32]: configuring netgroups from hostgroups
  [25/32]: creating default Sudo bind user
  [26/32]: creating default HBAC rule allow_all
  [27/32]: initializing group membership
  [28/32]: adding master entry
  [29/32]: configuring Posix uid/gid generation
  [30/32]: enabling compatibility plugin
  [31/32]: tuning directory server
  [32/32]: configuring directory to start on boot
done configuring dirsrv.
Configuring Kerberos KDC: Estimated time 30 seconds
  [1/14]: setting KDC account password
  [2/14]: adding sasl mappings to the directory
  [3/14]: adding kerberos entries to the DS
  [4/14]: adding default ACIs
  [5/14]: configuring KDC
  [6/14]: adding default keytypes
  [7/14]: adding default password policy
  [8/14]: creating a keytab for the directory
  [9/14]: creating a keytab for the machine
  [10/14]: exporting the kadmin keytab
  [11/14]: adding the password extension to the directory
  [12/14]: adding the kerberos master key to the directory
  [13/14]: starting the KDC
  [14/14]: configuring KDC to start on boot
done configuring krb5kdc.
Configuring ipa_kpasswd
  [1/2]: starting ipa_kpasswd 
  [2/2]: configuring ipa_kpasswd to start on boot
done configuring ipa_kpasswd.
Configuring the web interface: Estimated time 1 minute
  [1/12]: disabling mod_ssl in httpd
  [2/12]: setting mod_nss port to 443
  [3/12]: setting mod_nss password file
  [4/12]: adding URL rewriting rules
  [5/12]: configuring httpd
  [6/12]: setting up ssl
  [7/12]: setting up browser autoconfig
  [8/12]: publish CA cert
  [9/12]: creating a keytab for httpd
  [10/12]: configuring SELinux for httpd
  [11/12]: restarting httpd
  [12/12]: configuring httpd to start on boot
done configuring httpd.
Setting the certificate subject base
restarting certificate server
Applying LDAP updates
Restarting the directory server
Restarting the KDC
Restarting the web server
Sample zone file for bind has been created in /tmp/sample.zone.I_fDwT.db
==============================================================================
Setup complete

Next steps:
	1. You must make sure these network ports are open:
		TCP Ports:
		  * 80, 443: HTTP/HTTPS
		  * 389, 636: LDAP/LDAPS
		  * 88, 464: kerberos
		UDP Ports:
		  * 88, 464: kerberos
		  * 123: ntp

	2. You can now obtain a kerberos ticket using the command: 'kinit admin'
	   This ticket will allow you to use the IPA tools (e.g., ipa user-add)
	   and the web user interface.

Be sure to back up the CA certificate stored in /root/cacert.p12
This file is required to create replicas. The password for this
file is the Directory Manager password

Install and configure FreeIPA client(s)

Install the freeipa-client package on each client of the FreeIPA domain.

Install the FreeIPA client package

Fetch and install the FreeIPA client.

[root@client1 ~]# yum install freeipa-client
...

Configure the FreeIPA client package (OOPS!)

Again, if DNS is setup correctly and hostname returns the full DNS name, the default answers should work.

You want to use "admin" (the administrator user you created when configuring the FreeIPA server) as the enrollment principal.

Oh no! Currently, Fedora 15 gives me this problem:

[root@client1 ~]# ipa-client-install 
Discovery was successful!
Hostname: client1.example.fake
Realm: EXAMPLE.FAKE
DNS Domain: example.fake
IPA Server: server.example.fake
BaseDN: dc=example,dc=fake


Continue to configure the system with these values? [no]: yes
Enrollment principal: admin
Password for admin@EXAMPLE.FAKE: 

Joining realm failed because of failing XML-RPC request.
  This error may be caused by incompatible server/client major versions.

This problem is easily worked around, but you may not need to - I'm sure this will be fixed soon.

Configure the FreeIPA client package (The Workaround)

The problem and workaround are described here: https://www.redhat.com/archives/freeipa-users/2011-July/msg00029.html

Get credentials and add the host to FreeIPA

Both of these commands should be run on the *server*.

First, get admin credentials. If you are configuring multiple clients, this only needs to be run the first time.

[root@server ~]# kinit admin
Password for admin@EXAMPLE.FAKE:

Now that you have credentials, you can add the client to FreeIPA.

[root@server ~]# ipa host-add client1.example.fake
---------------------------------
Added host "client1.example.fake"
---------------------------------
  Host name: client1.example.fake
  Principal name: host/client1.example.fake@EXAMPLE.FAKE
  Managed by: client1.example.fake

(Force) Configure FreeIPA client

Back on the client now. Run ipa-client-install again, but this time use the --force flag:

[root@client1 ~]# ipa-client-install --force
Discovery was successful!
Hostname: client1.example.fake
Realm: EXAMPLE.FAKE
DNS Domain: example.fake
IPA Server: server.example.fake
BaseDN: dc=example,dc=fake


Continue to configure the system with these values? [no]: yes
Enrollment principal: admin
Password for admin@EXAMPLE.FAKE: 

Joining realm failed because of failing XML-RPC request.
  This error may be caused by incompatible server/client major versions.
  Use ipa-getkeytab to obtain a host principal for this server.
Created /etc/ipa/default.conf
Configured /etc/sssd/sssd.conf
Configured /etc/krb5.conf for IPA realm EXAMPLE.FAKE
Failed to configure automatic startup of the NSCD daemon
SSSD enabled
nss_ldap is not able to use DNS discovery!
Changing configuration to use hardcoded server name: server.example.fake
Kerberos 5 enabled
NTP enabled
Client configuration complete.

Manually fetch the keytab entry for the client

The last step of the workaround is to fetch the client's own keytab entry that ipa-client-install wasn't able to get.

To do this, you'll need to authenticate as admin again, but this time on the client:

[root@client1 ~]# kinit admin
Password for admin@EXAMPLE.FAKE:

Now run ipa-getkeytab on the client for the host keytab entries:

[root@client1 ~]# ipa-getkeytab -s server.example.fake -p host/client1.example.fake -k /etc/krb5.keytab
Keytab successfully retrieved and stored in: /etc/krb5.keytab

Now, FreeIPA should be setup on the client.

Add FreeIPA NFS service for each host

The next step is to setup kerberos principals for the NFS service on each host.

Add FreeIPA NFS service for server

[root@server ~]# ipa service-add nfs/server.example.fake
----------------------------------------------------
Added service "nfs/server.example.fake@EXAMPLE.FAKE"
----------------------------------------------------
  Principal: nfs/server.example.fake@EXAMPLE.FAKE
  Managed by: server.example.fake

Add FreeIPA NFS service for client(s)

[root@server ~]# ipa service-add nfs/client1.example.fake
-----------------------------------------------------
Added service "nfs/client1.example.fake@EXAMPLE.FAKE"
-----------------------------------------------------
  Principal: nfs/client1.example.fake@EXAMPLE.FAKE
  Managed by: client1.example.fake

Import FreeIPA NFS service tickets on the server

Again, we have to fetch a keytab entry. This time, it's for the nfs service of the local host.

According to this, we need to specify the enc type "des-cbc-crc".

[root@server ~]# ipa-getkeytab -s server.example.fake -e des-cbc-crc -p nfs/server.example.fake -k /etc/krb5.keytab
Keytab successfully retrieved and stored in: /etc/krb5.keytab

You can check to see what's in the keytab like this:

[root@server ~]# klist -ke /etc/krb5.keytab
Keytab name: WRFILE:/etc/krb5.keytab
KVNO Principal
---- --------------------------------------------------------------------------
   6 nfs/server.example.fake@EXAMPLE.FAKE (des-cbc-crc) 
   4 host/server.example.fake@EXAMPLE.FAKE (aes256-cts-hmac-sha1-96) 
   4 host/server.example.fake@EXAMPLE.FAKE (aes128-cts-hmac-sha1-96) 
   4 host/server.example.fake@EXAMPLE.FAKE (des3-cbc-sha1) 
   4 host/server.example.fake@EXAMPLE.FAKE (arcfour-hmac) 
   4 host/server.example.fake@EXAMPLE.FAKE (des-cbc-crc)

Import FreeIPA NFS service tickets on the client(s)

[root@client1 ~]# ipa-getkeytab -s server.example.fake -e des-cbc-crc -p nfs/client1.example.fake -k /etc/krb5.keytab
Keytab successfully retrieved and stored in: /etc/krb5.keytab

And here's what /etc/krb5.kettab has in it:

[root@client1 ~]# klist -ke /etc/krb5.keytab
Keytab name: WRFILE:/etc/krb5.keytab
KVNO Principal
---- --------------------------------------------------------------------------
   6 nfs/client1.example.fake@EXAMPLE.FAKE (des-cbc-crc) 
   3 host/client1.example.fake@EXAMPLE.FAKE (aes256-cts-hmac-sha1-96) 
   3 host/client1.example.fake@EXAMPLE.FAKE (aes128-cts-hmac-sha1-96) 
   3 host/client1.example.fake@EXAMPLE.FAKE (des3-cbc-sha1) 
   3 host/client1.example.fake@EXAMPLE.FAKE (arcfour-hmac) 
   3 host/client1.example.fake@EXAMPLE.FAKE (des-cbc-crc)

Turn on "Secure NFS" on both client(s) and server

This turns on NFS secure mounts and enables rpc.gssd and rpc.svcgssd.

Edit these lines in file "/etc/sysconfig/nfs":

# Set to turn on Secure NFS mounts.
SECURE_NFS="yes"
# Optional arguments passed to rpc.gssd. See rpc.gssd(8)
RPCGSSDARGS="-vvv"
# Optional arguments passed to rpc.svcgssd. See rpc.svcgssd(8)
RPCSVCGSSDARGS="-vvv"

The -vvv flags are for better debugging output in file "/var/log/messages".

To pick up the changes, you must restart nfs services:

[root@client1 ~]# service nfs restart
Restarting nfs (via systemctl):                            [  OK  ]
[root@client1 ~]# service rpcgssd restart
Restarting rpcgssd (via systemctl):                        [  OK  ]
[root@client1 ~]# service rpcsvcgssd restart
Restarting rpcsvcgssd (via systemctl):                     [  OK  ]

This must be run on both clients and servers.

Each host must have it's full DNS name in /etc/hosts

NFS util program 'rpc.gssd' (XXX ???) requires that the full dns name of the host be in /etc/hosts. The full DNS name must be the only entry on that line.

On the server:

[root@server ~]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

192.168.56.20 server.example.fake

This must be done on the client(s) as well:

[root@client1 ~]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

192.168.56.40 client1.example.fake

Set up /etc/exports on the server

Edit file "/etc/exports". This makes one krb5 mountpoint of /export to be mounted as "/" (thats the fsid=0 part):

/export gss/krb5(rw,fsid=0,insecure,no_subtree_check,no_root_squash)

Now exportfs should show the mount:

[root@server ~]# exportfs -av
exportfs: scandir /etc/exports.d: No such file or directory

exporting gss/krb5:/export

Restart nfs:

[root@server ~]# service nfs restart
Restarting nfs (via systemctl):                            [  OK  ]

Allow Kerberos to use "weak crypto"

To use the des key kerberos must be told to allow "weak" crypto. Newer kernels + nfsutils allow the use of AES, etc.

XXX look in to why fedora 15 is like this

Edit file '/etc/krb5.conf':

In section "libdefaults", add the line:

allow_weak_crypto = true

Mount the filesystem

The moment of truth!

If you run in to problems see ProblemsMountingNFS.

[root@client1 ~]# mount -v -t nfs4 -o sec=krb5 server.example.fake:/ /mnt
mount.nfs4: timeout set for Tue Jul 19 22:36:46 2011
mount.nfs4: trying text-based options 'sec=krb5,addr=192.168.56.20,clientaddr=192.168.56.40'
server.example.fake:/ on /mnt type nfs4 (rw,sec=krb5)

now test it as root

[root@client1 ~]# echo "test" > /mnt/example.com
[root@client1 ~]# cat /mnt/example.com
test

Test the NFS mount as another user

This section just covers testing the NFS mount with other users. I get a little verbose here describing how to add users in the FreeIPA system.

Add another user

First, we need to add another user to FreeIPA.

This must be run with credentials. (XXX link)

On the *server*, run:

[root@server ~]# ipa user-add someguy
First name: guy
Last name: someone
--------------------
Added user "someguy"
--------------------
  User login: someguy
  First name: guy
  Last name: someone
  Full name: guy someone
  Display name: guy someone
  Initials: gs
  Home directory: /home/someguy
  GECOS field: guy someone
  Login shell: /bin/sh
  Kerberos principal: someguy@EXAMPLE.FAKE
  UID: 25400004

Now set a temporary password for the user. The first time the user logs in, they must change it to something new.

[root@server ~]# ipa passwd someguy
Password: 
Enter Password again to verify: 
-------------------------------------------
Changed password for "someguy@EXAMPLE.FAKE"
-------------------------------------------

Test NFS on client

Now there is a new user the client(s)!

[root@client1 ~]# su someguy
sh-4.2$ id
uid=25400004(someguy) gid=25400004(someguy) groups=25400004(someguy),25400001(ipausers) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

Authenticate as the user:

sh-4.2$ kinit
Password for someguy@EXAMPLE.FAKE: 
Password expired.  You must change it now.
Enter new password: 
Enter it again:

Now test nfs:

sh-4.2$ echo bar > /mnt/foo
sh-4.2$ cat /mnt/foo
bar
sh-4.2$ ls -l /mnt
total 12
-rw-r--r--. 1 nobody  nobody  4 Jul 19 17:22 bar
-rw-r--r--. 1 nobody  nobody  5 Jul 19 22:35 example.com
-rw-r--r--. 1 someguy someguy 4 Jul 19 22:44 foo

FreeIPA and NFSv4