kumquat-buildroot/support/scripts/mkusers
Norbert Lange 41ea61d59c support/scripts/mkusers: allow option for system uid/gid
Some software decides based on uid/gid whether a user is a system or
normal (human) user, with different behaviour for those flavors (example
journald [2]).

So adding logic to create system-users is necessary, we take the now
common ranges from [1].

This extends the mkusers script to allow -2 for uid/gid, this argument
will take an identifier from the user range. All identifiers used up to
now should have been from the system range, so -1 is now interpreted as
a system user/group.

Note that after this commit, all the UIDs and GIDs that are created
automatically (with -1) will change. That means if there is peristent
data on an existing system that was created by such an automatic user,
it will suddenly belong to a different user. However, this could already
happen before: if a USERS line is added to a package, then other UIDs
may change as well.

Add system/user ranges as variables, and the argument for user/system
uid variable as well. Thus some magic constants could be removed, some
further occurences of -1 were replaced with equivalent logic. For
consistency, the existing MIN/MAX_UID/GID variables are renamed to
FIRST/LAST_USER_UID/GID.

Update the documentation with the new automatic ranges.

[1] - https://systemd.io/UIDS-GIDS/
[2] - https://www.freedesktop.org/software/systemd/man/journald.conf.html

Signed-off-by: Norbert Lange <nolange79@gmail.com>
[Arnout: use -1 for system users; refactor the changes a bit]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
2022-02-05 23:09:31 +01:00

472 lines
16 KiB
Bash
Executable File

#!/usr/bin/env bash
set -e
myname="${0##*/}"
#----------------------------------------------------------------------------
# Configurable items
FIRST_USER_UID=1000
LAST_USER_UID=1999
FIRST_USER_GID=1000
LAST_USER_GID=1999
# use names from /etc/adduser.conf
FIRST_SYSTEM_UID=100
LAST_SYSTEM_UID=999
FIRST_SYSTEM_GID=100
LAST_SYSTEM_GID=999
# argument to automatically crease system/user id
AUTO_SYSTEM_ID=-1
AUTO_USER_ID=-2
# No more is configurable below this point
#----------------------------------------------------------------------------
#----------------------------------------------------------------------------
error() {
local fmt="${1}"
shift
printf "%s: " "${myname}" >&2
printf "${fmt}" "${@}" >&2
}
fail() {
error "$@"
exit 1
}
#----------------------------------------------------------------------------
if [ ${#} -ne 2 ]; then
fail "usage: %s USERS_TABLE TARGET_DIR\n"
fi
USERS_TABLE="${1}"
TARGET_DIR="${2}"
shift 2
PASSWD="${TARGET_DIR}/etc/passwd"
SHADOW="${TARGET_DIR}/etc/shadow"
GROUP="${TARGET_DIR}/etc/group"
# /etc/gshadow is not part of the standard skeleton, so not everybody
# will have it, but some may have it, and its content must be in sync
# with /etc/group, so any use of gshadow must be conditional.
GSHADOW="${TARGET_DIR}/etc/gshadow"
# We can't simply source ${BR2_CONFIG} as it may contains constructs
# such as:
# BR2_DEFCONFIG="$(CONFIG_DIR)/defconfig"
# which when sourced from a shell script will eventually try to execute
# a command named 'CONFIG_DIR', which is plain wrong for virtually every
# systems out there.
# So, we have to scan that file instead. Sigh... :-(
PASSWD_METHOD="$( sed -r -e '/^BR2_TARGET_GENERIC_PASSWD_METHOD="(.*)"$/!d;' \
-e 's//\1/;' \
"${BR2_CONFIG}" \
)"
#----------------------------------------------------------------------------
get_uid() {
local username="${1}"
awk -F: -v username="${username}" \
'$1 == username { printf( "%d\n", $3 ); }' "${PASSWD}"
}
#----------------------------------------------------------------------------
get_ugid() {
local username="${1}"
awk -F: -v username="${username}" \
'$1 == username { printf( "%d\n", $4 ); }' "${PASSWD}"
}
#----------------------------------------------------------------------------
get_gid() {
local group="${1}"
awk -F: -v group="${group}" \
'$1 == group { printf( "%d\n", $3 ); }' "${GROUP}"
}
#----------------------------------------------------------------------------
get_members() {
local group="${1}"
awk -F: -v group="${group}" \
'$1 == group { printf( "%s\n", $4 ); }' "${GROUP}"
}
#----------------------------------------------------------------------------
get_username() {
local uid="${1}"
awk -F: -v uid="${uid}" \
'$3 == uid { printf( "%s\n", $1 ); }' "${PASSWD}"
}
#----------------------------------------------------------------------------
get_group() {
local gid="${1}"
awk -F: -v gid="${gid}" \
'$3 == gid { printf( "%s\n", $1 ); }' "${GROUP}"
}
#----------------------------------------------------------------------------
get_ugroup() {
local username="${1}"
local ugid
ugid="$( get_ugid "${username}" )"
if [ -n "${ugid}" ]; then
get_group "${ugid}"
fi
}
#----------------------------------------------------------------------------
# Sanity-check the new user/group:
# - check the gid is not already used for another group
# - check the group does not already exist with another gid
# - check the user does not already exist with another gid
# - check the uid is not already used for another user
# - check the user does not already exist with another uid
# - check the user does not already exist in another group
check_user_validity() {
local username="${1}"
local uid="${2}"
local group="${3}"
local gid="${4}"
local _uid _ugid _gid _username _group _ugroup
_group="$( get_group "${gid}" )"
_gid="$( get_gid "${group}" )"
_ugid="$( get_ugid "${username}" )"
_username="$( get_username "${uid}" )"
_uid="$( get_uid "${username}" )"
_ugroup="$( get_ugroup "${username}" )"
if [ "${username}" = "root" ]; then
fail "invalid username '%s\n'" "${username}"
fi
if [ ${gid} -lt -2 -o ${gid} -eq 0 ]; then
fail "invalid gid '%d' for '%s'\n" ${gid} "${username}"
elif [ ${gid} -ge 0 ]; then
# check the gid is not already used for another group
if [ -n "${_group}" -a "${_group}" != "${group}" ]; then
fail "gid '%d' for '%s' is already used by group '%s'\n" \
${gid} "${username}" "${_group}"
fi
# check the group does not already exists with another gid
# Need to split the check in two, otherwise '[' complains it
# is missing arguments when _gid is empty
if [ -n "${_gid}" ] && [ ${_gid} -ne ${gid} ]; then
fail "group '%s' for '%s' already exists with gid '%d' (wants '%d')\n" \
"${group}" "${username}" ${_gid} ${gid}
fi
# check the user does not already exists with another gid
# Need to split the check in two, otherwise '[' complains it
# is missing arguments when _ugid is empty
if [ -n "${_ugid}" ] && [ ${_ugid} -ne ${gid} ]; then
fail "user '%s' already exists with gid '%d' (wants '%d')\n" \
"${username}" ${_ugid} ${gid}
fi
fi
if [ ${uid} -lt -2 -o ${uid} -eq 0 ]; then
fail "invalid uid '%d' for '%s'\n" ${uid} "${username}"
elif [ ${uid} -ge 0 ]; then
# check the uid is not already used for another user
if [ -n "${_username}" -a "${_username}" != "${username}" ]; then
fail "uid '%d' for '%s' already used by user '%s'\n" \
${uid} "${username}" "${_username}"
fi
# check the user does not already exists with another uid
# Need to split the check in two, otherwise '[' complains it
# is missing arguments when _uid is empty
if [ -n "${_uid}" ] && [ ${_uid} -ne ${uid} ]; then
fail "user '%s' already exists with uid '%d' (wants '%d')\n" \
"${username}" ${_uid} ${uid}
fi
fi
# check the user does not already exist in another group
if [ -n "${_ugroup}" -a "${_ugroup}" != "${group}" ]; then
fail "user '%s' already exists with group '%s' (wants '%s')\n" \
"${username}" "${_ugroup}" "${group}"
fi
return 0
}
#----------------------------------------------------------------------------
# Generate a unique GID for given group. If the group already exists,
# then simply report its current GID. Otherwise, generate the lowest GID
# that is:
# - not 0
# - comprised in [$2..$3]
# - not already used by a group
generate_gid() {
local group="${1}"
local mingid="${2}"
local maxgid="${3}"
local gid
gid="$( get_gid "${group}" )"
if [ -z "${gid}" ]; then
for(( gid=mingid; gid<=maxgid; gid++ )); do
if [ -z "$( get_group "${gid}" )" ]; then
break
fi
done
if [ ${gid} -gt ${maxgid} ]; then
fail "can not allocate a GID for group '%s'\n" "${group}"
fi
fi
printf "%d\n" "${gid}"
}
#----------------------------------------------------------------------------
# Add a group; if it does already exist, remove it first
add_one_group() {
local group="${1}"
local gid="${2}"
local members
# Generate a new GID if needed
if [ ${gid} -eq ${AUTO_USER_ID} ]; then
gid="$( generate_gid "${group}" $FIRST_USER_GID $LAST_USER_GID )"
elif [ ${gid} -eq ${AUTO_SYSTEM_ID} ]; then
gid="$( generate_gid "${group}" $FIRST_SYSTEM_GID $LAST_SYSTEM_GID )"
fi
members=$(get_members "$group")
# Remove any previous instance of this group, and re-add the new one
sed -i --follow-symlinks -e '/^'"${group}"':.*/d;' "${GROUP}"
printf "%s:x:%d:%s\n" "${group}" "${gid}" "${members}" >>"${GROUP}"
# Ditto for /etc/gshadow if it exists
if [ -f "${GSHADOW}" ]; then
sed -i --follow-symlinks -e '/^'"${group}"':.*/d;' "${GSHADOW}"
printf "%s:*::\n" "${group}" >>"${GSHADOW}"
fi
}
#----------------------------------------------------------------------------
# Generate a unique UID for given username. If the username already exists,
# then simply report its current UID. Otherwise, generate the lowest UID
# that is:
# - not 0
# - comprised in [$2..$3]
# - not already used by a user
generate_uid() {
local username="${1}"
local minuid="${2}"
local maxuid="${3}"
local uid
uid="$( get_uid "${username}" )"
if [ -z "${uid}" ]; then
for(( uid=minuid; uid<=maxuid; uid++ )); do
if [ -z "$( get_username "${uid}" )" ]; then
break
fi
done
if [ ${uid} -gt ${maxuid} ]; then
fail "can not allocate a UID for user '%s'\n" "${username}"
fi
fi
printf "%d\n" "${uid}"
}
#----------------------------------------------------------------------------
# Add given user to given group, if not already the case
add_user_to_group() {
local username="${1}"
local group="${2}"
local _f
for _f in "${GROUP}" "${GSHADOW}"; do
[ -f "${_f}" ] || continue
sed -r -i --follow-symlinks \
-e 's/^('"${group}"':.*:)(([^:]+,)?)'"${username}"'(,[^:]+*)?$/\1\2\4/;' \
-e 's/^('"${group}"':.*)$/\1,'"${username}"'/;' \
-e 's/,+/,/' \
-e 's/:,/:/' \
"${_f}"
done
}
#----------------------------------------------------------------------------
# Encode a password
encode_password() {
local passwd="${1}"
mkpasswd -m "${PASSWD_METHOD}" "${passwd}"
}
#----------------------------------------------------------------------------
# Add a user; if it does already exist, remove it first
add_one_user() {
local username="${1}"
local uid="${2}"
local group="${3}"
local gid="${4}"
local passwd="${5}"
local home="${6}"
local shell="${7}"
local groups="${8}"
local comment="${9}"
local _f _group _home _shell _gid _passwd
# First, sanity-check the user
check_user_validity "${username}" "${uid}" "${group}" "${gid}"
# Generate a new UID if needed
if [ ${uid} -eq ${AUTO_USER_ID} ]; then
uid="$( generate_uid "${username}" $FIRST_USER_GID $LAST_USER_GID )"
elif [ ${uid} -eq ${AUTO_SYSTEM_ID} ]; then
uid="$( generate_uid "${username}" $FIRST_SYSTEM_GID $LAST_SYSTEM_GID )"
fi
# Remove any previous instance of this user
for _f in "${PASSWD}" "${SHADOW}"; do
sed -r -i --follow-symlinks -e '/^'"${username}"':.*/d;' "${_f}"
done
_gid="$( get_gid "${group}" )"
_shell="${shell}"
if [ "${shell}" = "-" ]; then
_shell="/bin/false"
fi
case "${home}" in
-) _home="/";;
/) fail "home can not explicitly be '/'\n";;
/*) _home="${home}";;
*) fail "home must be an absolute path\n";;
esac
case "${passwd}" in
-)
_passwd=""
;;
!=*)
_passwd='!'"$( encode_password "${passwd#!=}" )"
;;
=*)
_passwd="$( encode_password "${passwd#=}" )"
;;
*)
_passwd="${passwd}"
;;
esac
printf "%s:x:%d:%d:%s:%s:%s\n" \
"${username}" "${uid}" "${_gid}" \
"${comment}" "${_home}" "${_shell}" \
>>"${PASSWD}"
printf "%s:%s:::::::\n" \
"${username}" "${_passwd}" \
>>"${SHADOW}"
# Add the user to its additional groups
if [ "${groups}" != "-" ]; then
for _group in ${groups//,/ }; do
add_user_to_group "${username}" "${_group}"
done
fi
# If the user has a home, chown it
# (Note: stdout goes to the fakeroot-script)
if [ "${home}" != "-" ]; then
mkdir -p "${TARGET_DIR}/${home}"
printf "chown -h -R %d:%d '%s'\n" "${uid}" "${_gid}" "${TARGET_DIR}/${home}"
fi
}
#----------------------------------------------------------------------------
main() {
local username uid group gid passwd home shell groups comment
local line
local auto_id
local -a ENTRIES
# Some sanity checks
if [ ${FIRST_USER_UID} -le 0 ]; then
fail "FIRST_USER_UID must be >0 (currently %d)\n" ${FIRST_USER_UID}
fi
if [ ${FIRST_USER_GID} -le 0 ]; then
fail "FIRST_USER_GID must be >0 (currently %d)\n" ${FIRST_USER_GID}
fi
# Read in all the file in memory, exclude empty lines and comments
while read line; do
ENTRIES+=( "${line}" )
done < <( sed -r -e 's/#.*//; /^[[:space:]]*$/d;' "${USERS_TABLE}" )
# We first create groups whose gid is positive, and then we create groups
# whose gid is automatic, so that, if a group is defined both with
# a specified gid and an automatic gid, we ensure the specified gid is
# used, rather than a different automatic gid is computed.
# First, create all the main groups which gid is *not* automatic
for line in "${ENTRIES[@]}"; do
read username uid group gid passwd home shell groups comment <<<"${line}"
[ ${gid} -ge 0 ] || continue # Automatic gid
add_one_group "${group}" "${gid}"
done
# Then, create all the main groups which gid *is* automatic
for line in "${ENTRIES[@]}"; do
read username uid group gid passwd home shell groups comment <<<"${line}"
[ ${gid} -lt 0 ] || continue # Non-automatic gid
add_one_group "${group}" "${gid}"
done
# Then, create all the additional groups
# If any additional group is already a main group, we should use
# the gid of that main group; otherwise, we can use any gid - a
# system gid if the uid is a system user (<= LAST_SYSTEM_UID),
# otherwise a user gid.
for line in "${ENTRIES[@]}"; do
read username uid group gid passwd home shell groups comment <<<"${line}"
if [ "${groups}" != "-" ]; then
if [ ${uid} -le 0 ]; then
auto_id=${uid}
elif [ ${uid} -le ${LAST_SYSTEM_UID} ]; then
auto_id=${AUTO_SYSTEM_ID}
else
auto_id=${AUTO_USER_ID}
fi
for g in ${groups//,/ }; do
add_one_group "${g}" ${auto_id}
done
fi
done
# When adding users, we do as for groups, in case two packages create
# the same user, one with an automatic uid, the other with a specified
# uid, to ensure the specified uid is used, rather than an incompatible
# uid be generated.
# Now, add users whose uid is *not* automatic
for line in "${ENTRIES[@]}"; do
read username uid group gid passwd home shell groups comment <<<"${line}"
[ "${username}" != "-" ] || continue # Magic string to skip user creation
[ ${uid} -ge 0 ] || continue # Automatic uid
add_one_user "${username}" "${uid}" "${group}" "${gid}" "${passwd}" \
"${home}" "${shell}" "${groups}" "${comment}"
done
# Finally, add users whose uid *is* automatic
for line in "${ENTRIES[@]}"; do
read username uid group gid passwd home shell groups comment <<<"${line}"
[ "${username}" != "-" ] || continue # Magic string to skip user creation
[ ${uid} -lt 0 ] || continue # Non-automatic uid
add_one_user "${username}" "${uid}" "${group}" "${gid}" "${passwd}" \
"${home}" "${shell}" "${groups}" "${comment}"
done
}
#----------------------------------------------------------------------------
main "${@}"