#!/bin/sh -e

action="$1"
oldversion="$2"

. /usr/share/debconf/confmodule
db_version 2.0

umask 022

if [ "$action" != configure ]
  then
  exit 0
fi



check_idea_key() {
    #check for old host_key files using IDEA, which openssh does not support
	if [ -f /etc/ssh/ssh_host_key ] ; then
		if ssh-keygen -p -N '' -f /etc/ssh/ssh_host_key 2>&1 | \
				grep -q 'unknown cipher' 2>/dev/null ; then
      mv /etc/ssh/ssh_host_key /etc/ssh/ssh_host_key.old
      mv /etc/ssh/ssh_host_key.pub /etc/ssh/ssh_host_key.pub.old
  fi
	fi
}


create_key() {
	local msg="$1"
	shift
	local file="$1"
	shift

	if [ ! -f "$file" ] ; then
		echo -n $msg
		ssh-keygen -q -f "$file" -N '' "$@"
		echo
	fi
}


create_keys() {
	db_get ssh/protocol2_only
	if [ "$RET" = "false" ] ; then
		create_key "Creating SSH1 key; this may take some time ..." \
			/etc/ssh/ssh_host_key -t rsa1
	fi

	create_key "Creating SSH2 RSA key; this may take some time ..." \
		/etc/ssh/ssh_host_rsa_key -t rsa
	create_key "Creating SSH2 DSA key; this may take some time ..." \
		/etc/ssh/ssh_host_dsa_key -t dsa
}


create_sshdconfig() {
	if [ -e /etc/ssh/sshd_config ] ; then
	    if dpkg --compare-versions "$oldversion" lt-nl 1:1.3 ; then
		db_get ssh/new_config
		if [ "$RET" = "false" ] ; then return 0; fi
	    else return 0
	    fi
	fi

	#Preserve old sshd_config before generating a new one
	if [ -e /etc/ssh/sshd_config ] ; then 
	    mv /etc/ssh/sshd_config /etc/ssh/sshd_config.dpkg-old
	fi

	cat <<EOF > /etc/ssh/sshd_config
# Package generated configuration file
# See the sshd(8) manpage for details

# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
EOF
	db_get ssh/protocol2_only
if [ "$RET" = "false" ]; then
		cat <<EOF >> /etc/ssh/sshd_config
Protocol 2,1
# HostKeys 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
EOF
else
	cat <<EOF >> /etc/ssh/sshd_config
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
EOF
fi

db_get ssh/privsep_ask
if [ "$RET" = "false" ]; then
    cat <<EOF >> /etc/ssh/sshd_config
#Explicitly set PrivSep off, as requested
UsePrivilegeSeparation no

# Use PAM authentication via keyboard-interactive so PAM modules can
# properly interface with the user
PAMAuthenticationViaKbdInt yes
EOF
else
	cat <<EOF >> /etc/ssh/sshd_config
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# ...but breaks Pam auth via kbdint, so we have to turn it off
# Use PAM authentication via keyboard-interactive so PAM modules can
# properly interface with the user (off due to PrivSep)
PAMAuthenticationViaKbdInt no
EOF
fi

	cat <<EOF >> /etc/ssh/sshd_config
# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 768

# Logging
SyslogFacility AUTH
LogLevel INFO

# Authentication:
LoginGraceTime 600
PermitRootLogin yes
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile	%h/.ssh/authorized_keys

# rhosts authentication should not be used
RhostsAuthentication no
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

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

# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication yes


# To change Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#AFSTokenPassing no
#KerberosTicketCleanup no

# Kerberos TGT Passing does only work with the AFS kaserver
#KerberosTgtPassing yes

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

#MaxStartups 10:30:60
#Banner /etc/issue.net
#ReverseMappingCheck yes

Subsystem	sftp	/usr/lib/sftp-server

EOF
}


fix_rsh_diversion() {
# get rid of mistaken rsh diversion (circa 1.2.27-1)

	if [ -L /usr/bin/rsh ] &&
		dpkg-divert --list '/usr/bin/rsh.real/rsh' | grep -q ' ssh$' ; then
		for cmd in rlogin  rsh rcp ; do
			[ -L /usr/bin/$cmd ] && rm /usr/bin/$cmd
			dpkg-divert --package ssh --remove --rename \
				--divert /usr/bin/rsh.real/$cmd /usr/bin/$cmd

			[ -L /usr/man/man1/$cmd.1.gz ] && rm /usr/man/man1/$$cmd.1.gz
			dpkg-divert --package ssh --remove --rename \
				--divert /usr/man/man1/$cmd.real.1.gz /usr/man/man1/$cmd.1.gz
		done

		rmdir /usr/bin/rsh.real
	fi
}


fix_statoverride() {
# Remove an erronous override for sshd (we should have overridden ssh)
	if [ -x /usr/sbin/dpkg-statoverride ]; then
		if dpkg-statoverride --list /usr/sbin/sshd >/dev/null ; then
			dpkg-statoverride --remove /usr/sbin/sshd
		fi
	fi
}


create_alternatives() {
# Create alternatives for the various r* tools.
# Make sure we don't change existing alternatives that a user might have
# changed, but clean up after some old alternatives that mistakenly pointed
# rlogin and rcp to ssh.
	update-alternatives --quiet --remove rlogin /usr/bin/ssh
	update-alternatives --quiet --remove rcp /usr/bin/ssh
	for cmd in rsh rlogin rcp; do
		scmd="s${cmd#r}"
		if ! update-alternatives --display "$cmd" | \
				grep -q "$scmd"; then
			update-alternatives --quiet --install "/usr/bin/$cmd" "$cmd" "/usr/bin/$scmd" 20 \
				--slave "/usr/share/man/man1/$cmd.1.gz" "$cmd.1.gz" "/usr/share/man/man1/$scmd.1.gz"
		fi
	done
}

setup_sshd_user() {
	if ! getent passwd sshd >/dev/null; then
		adduser --quiet --system --no-create-home --home /var/run/sshd sshd
	fi
}

set_sshd_permissions() {
	if dpkg --compare-versions "$oldversion" lt-nl 1:3.4p1-1 ; then
	    if [ -x /usr/sbin/dpkg-statoverride ] ; then
		if dpkg-statoverride --list /usr/bin/ssh >/dev/null; then
		    dpkg-statoverride --remove /usr/bin/ssh >/dev/null
		fi 
	    fi
	fi

	if [ ! -x /usr/sbin/dpkg-statoverride ] || \
	     ! dpkg-statoverride --list /usr/lib/ssh-keysign >/dev/null ; then
		db_get ssh/SUID_client
		if [ "$RET" = "false" ] ; then
			chmod 0755 /usr/lib/ssh-keysign
		elif [ "$RET" = "true" ] ; then
			chmod 4755 /usr/lib/ssh-keysign
		fi
	fi
}


fix_ssh_group() {
	# Try to remove non-system group mistakenly created by 1:3.5p1-1.
	# set_ssh_agent_permissions() below will re-create it properly.
	if getent group ssh >/dev/null; then
		delgroup --quiet ssh || true
	fi
}


set_ssh_agent_permissions() {
	if ! getent group ssh >/dev/null; then
		addgroup --system --quiet ssh
	fi
	if ! [ -x /usr/sbin/dpkg-statoverride ] || \
	    ! dpkg-statoverride --list /usr/bin/ssh-agent >/dev/null ; then
		chgrp ssh /usr/bin/ssh-agent
		chmod 2755 /usr/bin/ssh-agent
	fi
}


fix_conffile_permissions() {
	# Clean up after executable /etc/default/ssh in 1:3.5p1-5. dpkg
	# doesn't do this for us; see bug #192981.
	chmod 644 /etc/default/ssh
}

setup_startup() {
	db_get ssh/run_sshd
	if [ "$RET" = "false" ] ; then
		/etc/init.d/ssh stop 2>&1 >/dev/null
		touch /etc/ssh/sshd_not_to_be_run
	else
		rm -f /etc/ssh/sshd_not_to_be_run 2>/dev/null
	fi
}


setup_init() {
	if [ -e /etc/init.d/ssh ]; then
		update-rc.d ssh defaults >/dev/null
		/etc/init.d/ssh restart
	fi
}

check_idea_key
create_keys
create_sshdconfig
fix_rsh_diversion
fix_statoverride
create_alternatives
setup_sshd_user
set_sshd_permissions
if [ "$2" = "1:3.5p1-1" ]; then
    fix_ssh_group
fi
set_ssh_agent_permissions
if dpkg --compare-versions "$2" lt 1:3.6.1p2-2; then
    fix_conffile_permissions
fi
setup_startup
setup_init


db_stop

exit 0