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Installing Kerberos Keys on a Local Machine

by admin last modified 2005-09-08 01:19
First you must obtain a pass phrase from the FNAL helpdesk.  This will allow you to install service/ftp keys on your local machine.
(Most of these commands were taken from http://security.fnal.gov/StrongAuth/UserDocs/hostkeys.htm.  I refuse to take credit for their brilliance.)
Here's what I did on red.unl.edu
	# kadmin -p host/red.fnal.gov
Enter password: (enter the password you were given)
kadmin: ktadd host/red.fnal.gov
Entry for principal host/red.fnal.gov with kvno 2, encryption
type DES-CBC-CRC added to keytab WRFILE:/etc/krb5.keytab.
kadmin: exit
# kadmin -p ftp/red.fnal.gov
Enter password: (enter the password you were given)
kadmin: ktadd ftp/red.fnal.gov
Entry for principal ftp/red.fnal.gov with kvno 2, encryption
type DES-CBC-CRC added to keytab WRFILE:/etc/krb5.keytab.
kadmin: exit


This is the easy part.  The hard part is setting up ssh to authenticate against kerberos.  Here's the sshd_config file that I finally got to work correctly:


$OpenBSD: sshd_config,v 1.48 2002/02/19 02:50:59 deraadt Exp
# This is the sshd server system-wide configuration file.  See sshd(8
# for more information
# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin
# The strategy used for options in the default sshd_config shipped with # OpenSSH is to specify options with their default value where # possible, but leave them commented.  Uncommented options change a # default value.
#Port 22
#Protocol 2,1
#ListenAddress 0.0.0.0
#ListenAddress ::
# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 3600
#ServerKeyBits 768
# Logging
#obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
#SyslogFacility AUTHPRIV
#LogLevel INFO

# Authentication:
#LoginGraceTime 600

#PermitRootLogin yes
#StrictModes yes

RSAAuthentication no
PubkeyAuthentication no
#AuthorizedKeysFile .ssh/authorized_keys
# rhosts authentication should not be used
#RhostsAuthentication no
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts no
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
RhostsRSAAuthentication yes
# similar for protocol version 2
HostbasedAuthentication yes
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication yes
#PermitEmptyPasswords no

# Change to no to disable s/key passwords
ChallengeResponseAuthentication no

# Kerberos options # KerberosAuthentication automatically enabled if keyfile exists
KerberosAuthentication yes
KerberosOrLocalPasswd yes
KerberosTicketCleanup yes

# AFSTokenPassing automatically enabled if k_hasafs() is true #AFSTokenPassing yes

# Kerberos TGT Passing only works with the AFS kaserver

KerberosTgtPassing yes

# Set this to 'yes' to enable PAM keyboard-interactive authentication
# Warning: enabling this may bypass the setting of 'PasswordAuthentication'
#PAMAuthenticationViaKbdInt yes

#X11Forwarding no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PrintMotd yes
#PrintLastLog yes
#KeepAlive yes
#UseLogin no
UsePrivilegeSeparation no

#MaxStartups 10
# no default banner path
#Banner /some/path
#VerifyReverseMapping no

# override default of no subsystems
Subsystem sftp /usr/libexec/openssh/sftp-server

GssapiAuthentication yes
GssapiKeyExchange yes
GssapiUseSessionCredcache yes
GssapiCleanupCreds yes

AklogCmd /usr/krb5/bin/aklog

Don't forget to restart sshd after every edit to sshd_config
> /etc/init.d/sshd restart


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