KerberosNFSv4

How to install NFSv4 with Kerberos authentication on Debian Squeeze

References:

• http://wiki.debian.org/NFS/Kerberos

Server

Packages

nfs-kernel-server

apt-get install nfs-kernel-server

Configuration

/etc/default/nfs-common

[...]
# Do you want to start the idmapd daemon? It is only needed for NFSv4.
NEED_IDMAPD=yes

# Do you want to start the gssd daemon? It is required for Kerberos mounts.
NEED_GSSD=yes

/etc/default/nfs-kernel-server

NEED_SVCGSSD=yes

/etc/krb5.conf

Enable allow_weak_crypto in libdefaults section

• nfsv4 and encryption types
• Note that RC4-HMAC, 3DES, AES128 and AES256 seem supported in recent kernel

[libdefaults]
        default_realm = COINCOIN.EU
        allow_weak_crypto = true
        permitted_enctypes = des-cbc-crc # needed nfs-utils version of clients >= 1.2.3 (see debian bug #474037, nfs-utils commit 76be349d5dd07f55797cb9920cc275667258f10f)

Create needed directory

kdc:/root# mkdir /mnt/sdb1
kdc:/root# mkdir -p /export/Documents

/etc/exports

/export gss/krb5p(rw,async,no_subtree_check,crossmnt,fsid=0)
/export/Documents  gss/krb5p(rw,async,no_subtree_check)

/etc/fstab

# [...]
/dev/sdb1           /mnt/sdb1         ext3 defaults,acl 1       2
/mnt/sdb1/Documents /export/Documents none ro,bind      0       0

mount directory

kdc:/root# mount /mnt/sdb1
kdc:/root# mount /export/Documents

Export directories

kdc:/root# exportfs -rv
exporting gss/krb5p:/export/Documents
exporting gss/krb5p:/export

NFS service: Create principal entry

kdc:/root# kadmin.local
Authenticating as principal root/admin@COINCOIN.EU with password.
kadmin:  addprinc -randkey nfs/kdc.coincoin.eu
WARNING: no policy specified for nfs/kdc.coincoin.eu@COINCOIN.EU; defaulting to no policy
Principal "nfs/kdc.coincoin.eu@COINCOIN.EU" created.

export nfs@kdc principal to the keytab

kdc:/root# kadmin.local
Authenticating as principal root/admin@COINCOIN.EU with password.
ktadd -e des-cbc-crc:normal -k /etc/krb5.keytab nfs/kdc.coincoin.eu

You can list content of keytab:

kdc:~# ktutil 
ktutil:  rkt /etc/krb5.keytab 
ktutil:  list
slot KVNO Principal
---- ---- ---------------------------------------------------------------------
   1    2    nfs/kdc.coincoin.eu@COINCOIN.EU

Create client entry

kdc:/root# kadmin.local
kadmin:  addprinc -randkey nfs/client.coincoin.eu
WARNING: no policy specified for nfs/client.coincoin.eu@COINCOIN.EU; defaulting to no policy
Principal "nfs/client.coincoin.eu@COINCOIN.EU" created.

Start services

• /etc/init.d/nfs-common start
• /etc/init.d/nfs-kernel-server start

Client

Packages

apt-get install nfs-client

Configuration

/etc/krb5.conf

Enable allow_weak_crypto in libdefaults section

[libdefaults]
        default_realm = COINCOIN.EU
        allow_weak_crypto = true

/etc/fstab

kdc.coincoin.eu:/Documents /mnt/Documents nfs4 sec=krb5p,rw,hard,rsize=32768,wsize=32768,noexec,nosuid,auto 0  0

Check DNS configuration

root@client:/root# host kdc.coincoin.eu
kdc.coincoin.eu has address 192.168.20.123
root@client:/root# host 192.168.20.123
123.20.168.192.in-addr.arpa domain name pointer kdc.coincoin.eu.

/etc/default/nfs-common

[...]
# Do you want to start the idmapd daemon? It is only needed for NFSv4.
NEED_IDMAPD=yes

# Do you want to start the gssd daemon? It is required for Kerberos mounts.
NEED_GSSD=yes

Start services

/etc/init.d/nfs-common restart

Create keytab

client:/root# kadmin -p superuser
Authenticating as principal superuser with password.
Password for superuser@COINCOIN.EU: 
ktadd -e des-cbc-crc:normal -k /etc/krb5.keytab nfs/client.coincoin.eu

Errors

Additional pre-authentication required

/var/log/kerberos/krb5kdc.log:

Mar 01 01:10:57 kdc krb5kdc[2608](info): AS_REQ (7 etypes {18 17 16 23 1 3 2}) 192.168.25.3: NEEDED_PREAUTH: nfs/kdc.coincoin.eu@COINCOIN.EU for krbtgt/COINCOIN.EU@COINCOIN.EU, Additional pre-authentication required

check allow_weak_crypto in /etc/krb5.conf of server and client

Increase verbosity

server

/etc/default/nfs-kernel-server

RPCSVCGSSDOPTS=-vvvvvvvvv

server and client

/etc/init.d/nfs-common

RPCGSSDOPTS=-vvvvvvvvvvvvvv

Replace

start-stop-daemon --start --oknodo --quiet \
--exec /usr/sbin/rpc.idmapd

by

start-stop-daemon --start --oknodo --quiet \
--exec /usr/sbin/rpc.idmapd -- -vvvvvvvvvvvvvvv

TODO

• details client:/root# kadmin -p superuser
• /etc/idmapd.conf
• weak crypto

Performances

• network: 100Mbps, server: Atom D525 and 2Go, client: Core i7 and 2Go
  • krb5/krb5i/krb5p: no difference when moving a file ~ 1 minute 6 sec