# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# @ECLASS: user.eclass
# @MAINTAINER:
# The Chromium OS Authors. <chromium-os-dev@chromium.org>
# @BLURB: user management in ebuilds
# @DESCRIPTION:
# Replaces the upstream mechanism of managing users and groups with one that
# manages the database in ${ROOT}, changing the sysroot database
# only when the caller creates the user/group during setup.

# Before we manipulate users at all, we want to make sure that
# passwd/group/shadow is initialized in the first place. That's
# what baselayout does.
#
# We should consider providing a virtual to abstract away this dependency.
# This would allow CrOS builds to completely specify all users and groups,
# instead of accepting the assumption (expressed in baselayout, currently)
# that every build wants groups like wheel, tty and so forth.
if [ "${PN}" != "baselayout" ]; then
	DEPEND="sys-apps/baselayout"
	RDEPEND="sys-apps/baselayout"
fi

# @FUNCTION: _assert_pkg_ebuild_phase
# @INTERNAL
# @USAGE: <calling func name>
_assert_pkg_ebuild_phase() {
	case ${EBUILD_PHASE} in
	setup|preinst|postinst) ;;
	*)
		eerror "'$1()' called from '${EBUILD_PHASE}' phase which is not OK:"
		eerror "You may only call from pkg_{setup,preinst,postinst} functions."
		eerror "Package fails at QA and at life.  Please file a bug."
		die "Bad package!  $1 is only for use in some pkg_* functions!"
	esac
}

# If an overlay has eclass overrides, but doesn't actually override the
# user.eclass, we'll have USER_ECLASSDIR pointing to the active overlay's
# eclass/ dir, but the users and groups templates are still in our profiles/.
USER_ECLASSDIR_LOCAL=${BASH_SOURCE[0]%/*}
ACCOUNTS_DIR_LOCAL="${USER_ECLASSDIR_LOCAL}/../profiles/base/accounts/"

# @FUNCTION: _get_value_for_user
# @INTERNAL
# @USAGE: <user> <key>
# @DESCRIPTION:
# Gets value from appropriate account definition file.
_get_value_for_user() {
	local user=$1 key=$2
	[[ $# -ne 2 ]] && die "usage: _get_value_for_user <user> <key>"

	case ${key} in
	user|password|uid|gid|gecos|home|shell) ;;
	*) die "sorry, '${key}' is not a field in the passwd db." ;;
	esac

	local template="${ACCOUNTS_DIR_LOCAL}/user/${user}"
	[[ ! -e "${template}" ]] && die "No entry for ${user} at ${template}."
	awk -F':' -v key="${key}" '$1 == key { print $2 }' "${template}"
}

# @FUNCTION: _get_value_for_group
# @INTERNAL
# @USAGE: <group> <key>
# @DESCRIPTION:
# Gets value from appropriate account definition file.
_get_value_for_group() {
	local group=$1 key=$2
	[[ $# -ne 2 ]] && die "usage: _get_value_for_group <group> <key>"

	case ${key} in
	group|password|gid|users) ;;
	*) die "sorry, '${key}' is not a field in the group db." ;;
	esac

	local template="${ACCOUNTS_DIR_LOCAL}/group/${group}"
	[[ ! -e "${template}" ]] && die "No entry for ${group} at ${template}."
	awk -F':' -v key="${key}" '$1 == key { print $2 }' "${template}"
}

# @FUNCTION: _portable_grab_lock
# @INTERNAL
# @USAGE: <lockfile>
# @DESCRIPTION:
# Grabs a lock on <lockfile> in a race-free, portable manner.
# We need to use this mechanism in order to be compatible with the shadow utils
# (groupadd, useradd, etc).
_portable_grab_lock() {
	local lockfile=$1
	local lockfile_1="${lockfile}.${BASHPID}"
	touch "${lockfile_1}"
	until ln "${lockfile_1}" "${lockfile}" &> /dev/null; do
		sleep 1
	done
	rm "${lockfile_1}" || die "Failed to lock ${lockfile}."
}

# @FUNCTION: _write_entry_to_db()
# @INTERNAL
# @USAGE: <entry> <database> <root>
# @DESCRIPTION:
# Writes an entry to the specified database under the specified root.
_write_entry_to_db() {
	local entry=$1 db=$2 root=$3

	[[ $# -ne 3 ]] && die "usage: _write_entry_to_db <entry> <database> <root>"

	case ${db} in
	passwd|group) ;;
	*) die "sorry, database '${db}' not supported." ;;
	esac

	local dbfile=$(readlink -e "${root}/etc/${db}")
	[[ ! -e "${dbfile}" ]] && die "${db} under ${root} does not exist."

	 # Use the same lock file as the shadow utils.
	local lockfile="${dbfile}.lock"
	_portable_grab_lock "${lockfile}"

	echo "${entry}" >> "${dbfile}" || die "Could not write ${entry} to ${dbfile}."

	rm "${lockfile}" || die "Failed to release lock on ${lockfile}."
}

# @FUNCTION: egetent
# @USAGE: <database> <key>
# @DESCRIPTION:
# Provides getent-like functionality for databases under ${ROOT}.
#
# Supported databases: group passwd
egetent() {
	local db=$1 key=$2

	[[ $# -ne 2 ]] && die "usage: egetent <database> <key>"

	case ${db} in
	passwd|group) ;;
	*) die "sorry, database '${db}' not yet supported; file a bug" ;;
	esac

	local dbfile=$(readlink -e "${ROOT}/etc/${db}")
	[[ ! -e "${dbfile}" ]] && die "${db} under ${ROOT} does not exist."
	local lockfile="${dbfile}.lock"
	_portable_grab_lock "${lockfile}"

	awk -F':' -v key="${key}" \
		'($1 == key || $3 == key) { print }' \
		"${ROOT}/etc/${db}" 2>/dev/null

	rm "${lockfile}" || die "Failed to release lock on ${lockfile}."
}

# @FUNCTION: enewuser
# @USAGE: <user> [uid] [shell] [homedir] [groups]
# @DESCRIPTION:
# Same as enewgroup, you are not required to understand how to properly add
# a user to the system.  The only required parameter is the username.
# Default uid is (pass -1 for this) next available, default shell is
# /bin/false, default homedir is /dev/null, and there are no default groups.
enewuser() {
	_assert_pkg_ebuild_phase ${FUNCNAME}

	# get the username
	local euser=$1; shift
	if [[ -z ${euser} ]] ; then
		eerror "No username specified !"
		die "Cannot call enewuser without a username"
	fi

	# lets see if the username already exists
	if [[ -n $(egetent passwd "${euser}") ]] ; then
		return 0
	fi

	# Ensure username exists in profile.
	if [[ -z $(_get_value_for_user "${euser}" user) ]] ; then
		die "'${euser}' does not exist in profile!"
	fi
	einfo "Adding user '${euser}' to your system ..."

	# Handle uid. Passing no UID is functionally equivalent to passing -1.
	local provided_uid=$(_get_value_for_user "${euser}" uid)
	local euid=$1; shift
	if [[ -z ${euid} ]] ; then
		euid=-1
	elif [[ ${euid} -lt -1 ]] ; then
		eerror "Userid given but is not greater than 0 !"
		die "${euid} is not a valid UID."
	fi
	# Now, ${euid} is set and >= -1.
	if [[ -n ${provided_uid} ]] ; then
		# If profile has UID and caller specified '' or -1, use profile.
		# If profile has UID and caller specified different, barf.
		# If profile has UID and caller specified same, OK.
		if [[ ${euid} == -1 ]] ; then
			euid=${provided_uid}
		elif [[ ${euid} != ${provided_uid} ]] ; then
			eerror "Userid differs from the profile!"
			die "${euid} != ${provided_uid} from profile."
			# else...they're already equal, so do nothing.
		fi
	else
		# If profile has no UID and caller did not specify, barf.
		if [[ ${euid} == -1 ]] ; then
			die "No UID specified in profile!"
		fi
		# If profile has no entry w/UID and caller specified one, OK.
	fi

	if [[ -n $(egetent passwd ${euid}) ]] ; then
		eerror "UID ${euid} already taken!"
		die "${euid} already taken in $(egetent passwd ${euid})"
	fi
	einfo " - Userid: ${euid}"

	# handle shell
	local eshell=$1; shift
	if [[ -n ${eshell} && ${eshell} != "-1" ]] ; then
		if [[ ${eshell} == */false || ${eshell} == */nologin ]] ; then
			eerror "Do not specify ${eshell} yourself, use -1"
			die "Pass '-1' as the shell parameter"
		fi
	else
		eshell=$(_get_value_for_user "${euser}" shell)
		${eshell:=/bin/false}
	fi
	if [[ ${eshell} != */false && ${eshell} != */nologin ]] ; then
		if [[ ! -e ${ROOT}${eshell} ]] ; then
			eerror "A shell was specified but it does not exist !"
			die "${eshell} does not exist in ${ROOT}"
		fi
	fi
	einfo " - Shell: ${eshell}"

	# handle homedir
	local ehome=$1; shift
	if [[ -z ${ehome} || ${ehome} == "-1" ]] ; then
		ehome=$(_get_value_for_user "${euser}" home)
	fi
	einfo " - Home: ${ehome}"

	# Grab groups for later handling.
	local egroups=$1; shift

	# Check groups.
	local g egroups_arr
	IFS="," read -r -a egroups_arr <<<"${egroups}"
	shift
	for g in "${egroups_arr[@]}" ; do
		enewgroup "${g}"
	done
	einfo " - Groups: ${egroups:-(none)}"

	local comment
	if [[ $# -gt 0 ]] ; then
		die "extra arguments no longer supported; please file a bug."
	else
		comment=$(_get_value_for_user "${euser}" gecos)
		einfo " - GECOS: ${comment}"
	fi

	local epassword=$(_get_value_for_user "${euser}" password)
	: ${epassword:="!"}
	local entry="${euser}:${epassword}:${euid}:${euid}:${comment}:${ehome}:${eshell}"
	if [[ ${EBUILD_PHASE} == "setup" ]] ; then
		_write_entry_to_db "${entry}" passwd /
	fi
	_write_entry_to_db "${entry}" passwd "${ROOT}"

	if [[ ! -e ${ROOT}/${ehome} ]] ; then
		einfo " - Creating ${ehome} in ${ROOT}"
		mkdir -p "${ROOT}/${ehome}"
		chown "${euser}" "${ROOT}/${ehome}"
		chmod 755 "${ROOT}/${ehome}"
	fi
}

# @FUNCTION: enewgroup
# @USAGE: <group> [gid]
# @DESCRIPTION:
# This function does not require you to understand how to properly add a
# group to the system.  Just give it a group name to add and enewgroup will
# do the rest.  You may specify the gid for the group or allow the group to
# allocate the next available one.
enewgroup() {
	_assert_pkg_ebuild_phase ${FUNCNAME}

	# Get the group.
	local egroup=$1; shift
	if [[ -z ${egroup} ]] ; then
		eerror "No group specified !"
		die "Cannot call enewgroup without a group"
	fi

	# See if group already exists.
	if [[ -n $(egetent group "${egroup}") ]] ; then
		return 0
	fi
	# Ensure group exists in profile.
	if [[ -z $(_get_value_for_group "${egroup}" group) ]] ; then
		die "Config for ${egroup} not present in profile!"
	fi
	einfo "Adding group '${egroup}' to your system ..."

	# handle gid
	local provided_gid=$(_get_value_for_group "${egroup}" gid)
	local egid=$1; shift
	if [[ -z ${egid} ]] ; then
		# If caller specified nothing and profile has GID, use profile.
		# If caller specified nothing and profile has no GID, barf.
		if [[ ! -z ${provided_gid} ]] ; then
			egid=${provided_gid}
		else
			die "No gid provided in PROFILE or in args!"
		fi
	else
		if [[ ${egid} -lt 0 ]] ; then
			eerror "Groupid given but is not greater than 0 !"
			die "${egid} is not a valid GID"
		fi

		# If caller specified GID and profile has no GID, OK.
		# If caller specified GID and profile has entry with same, OK.
		if [[ -z ${provided_gid} || ${egid} -eq ${provided_gid} ]] ; then
			provided_gid=${egid}
		fi

		# If caller specified GID but profile has different, barf.
		if [[ ${egid} -ne ${provided_gid} ]] ; then
			eerror "${egid} conflicts with provided ${provided_gid}!"
			die "${egid} conflicts with provided ${provided_gid}!"
		fi
	fi
	if [[ -n $(egetent group ${egid}) ]] ; then
		eerror "Groupid ${egid} already taken!"
		die "${egid} already taken in $(egetent group ${egid})"
	fi
	einfo " - Groupid: ${egid}"

	# Handle extra.
	if [[ $# -gt 0 ]] ; then
		die "extra arguments no longer supported; please file a bug"
	fi

	# Allow group passwords, if profile asks for it.
	local epassword=$(_get_value_for_group "${egroup}" password)
	: ${epassword:="!"}
	einfo " - Password entry: ${epassword}"

	# Pre-populate group with users.
	local eusers=$(_get_value_for_group "${egroup}" users)
	einfo " - User list: ${eusers}"

	# Add the group.
	local entry="${egroup}:${epassword}:${egid}:${eusers}"
	if [[ ${EBUILD_PHASE} == "setup" ]] ; then
		_write_entry_to_db "${entry}" group /
	fi
	_write_entry_to_db "${entry}" group "${ROOT}"
	einfo "Done with group: '${egroup}'."

}

# @FUNCTION: egethome
# @USAGE: <user>
# @DESCRIPTION:
# Gets the home directory for the specified user.
egethome() {
	[[ $# -eq 1 ]] || die "usage: egethome <user>"
	egetent passwd "$1" | cut -d: -f6
}

# @FUNCTION: egetshell
# @USAGE: <user>
# @DESCRIPTION:
# Gets the shell for the specified user.
egetshell() {
	[[ $# -eq 1 ]] || die "usage: egetshell <user>"
	egetent passwd "$1" | cut -d: -f7
}