[Buildroot] [PATCH 1/2] packages: add ability for packages to create users
Arnout Vandecappelle
arnout at mind.be
Wed Feb 6 00:12:57 UTC 2013
Although I have a shitload of comments below, there's nothing critical so:
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
On 05/02/13 15:54, Yann E. MORIN wrote:
[snip]
> diff --git a/support/scripts/mkusers b/support/scripts/mkusers
> new file mode 100755
> index 0000000..d98714c
> --- /dev/null
> +++ b/support/scripts/mkusers
> @@ -0,0 +1,371 @@
> +#!/bin/bash
Although we already do depend on bash, I would prefer not to add more
dependencies. The only bashism I could find is the 'local' declaration,
which unfortunately is really required where it is used in this script.
So never mind that.
> +set -e
> +myname="${0##*/}"
> +
> +#----------------------------------------------------------------------------
> +# Configurable items
> +MIN_UID=1000
> +MAX_UID=1999
> +MIN_GID=1000
> +MAX_GID=1999
> +# No more is configurable below this point
> +#----------------------------------------------------------------------------
> +
> +#----------------------------------------------------------------------------
> +error() {
> + local fmt="${1}"
> + shift
> +
> + printf "%s: " "${myname}" >&2
> + printf "${fmt}" "${@}" >&2
> +}
> +fail() {
> + error "$@"
> + exit 1
> +}
> +
> +#----------------------------------------------------------------------------
> +if [ ${#} -ne 2 ]; then
> + fail "usage: %s USERS_TBLE TARGET_DIR\n"
USERS_TABLE
> +fi
> +USERS_TABLE="${1}"
> +TARGET_DIR="${2}"
> +shift 2
> +PASSWD="${TARGET_DIR}/etc/passwd"
> +SHADOW="${TARGET_DIR}/etc/shadow"
> +GROUP="${TARGET_DIR}/etc/group"
> +# /etc/gsahdow is not part of the standard skeleton, so not everybody
gshadow
> +# will have it, but some may hav it, and its content must be in sync
> +# with /etc/group, so any use of gshadow must be conditional.
> +GSHADOW="${TARGET_DIR}/etc/gshadow"
> +PASSWD_METHOD="$( sed -r -e '/^BR2_TARGET_GENERIC_PASSWD_METHOD="(.)*"$/!d' \
> + -e 's//\1/;' \
> + "${BUILDROOT_CONFIG}" \
> + )"
I'm personally more in favour of sourcing ${BUILDROOT_CONFIG} and using
"${BR2_TARGET_GENERIC_PASSWD_METHOD}" directly.
> +
> +#----------------------------------------------------------------------------
> +get_uid() {
> + local username="${1}"
> +
> + awk -F: '$1=="'"${username}"'" { printf( "%d\n", $3 ); }' "${PASSWD}"
I personally find it easier to read an awk script that is written like
this:
awk -F: -v username="${1}" \
'$1 == username { printf( "%d\n", $3 ); }'
(i.e. pass variables as awk variables rather than expanding them in the
awk script).
But obviously that's just personal opinion.
> +}
> +
> +#----------------------------------------------------------------------------
> +get_ugid() {
> + local username="${1}"
> +
> + awk -F: '$1=="'"${username}"'" { printf( "%d\n", $4 ); }' "${PASSWD}"
> +}
> +
> +#----------------------------------------------------------------------------
> +get_gid() {
> + local group="${1}"
> +
> + awk -F: '$1=="'"${group}"'" { printf( "%d\n", $3 ); }' "${GROUP}"
> +}
I would define a single get_id for passwd and group, where the file is
passed as a parameter. That allows to factor the generate_uid/gid, below,
as well.
> +
> +#----------------------------------------------------------------------------
> +get_username() {
> + local uid="${1}"
> +
> + awk -F: '$3=="'"${uid}"'" { printf( "%s\n", $1 ); }' "${PASSWD}"
> +}
> +
> +#----------------------------------------------------------------------------
> +get_group() {
> + local gid="${1}"
> +
> + awk -F: '$3=="'"${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 -1 -o ${gid} -eq 0 ]; then
If ${gid} is not an integer, this will report:
[: foo: integer expression expected
in addition to the error below. Unfortunately there is no way to check
for integer, but you could redirect stderr to /dev/null.
> + fail "invalid gid '%d'\n" ${gid}
> + elif [ ${gid} -ne -1 ]; then
> + # check the gid is not already used for another group
> + if [ -n "${_group}" -a "${_group}" != "${group}" ]; then
> + fail "gid is already used by group '${_group}'\n"
> + fi
> +
> + # check the group does not already exists with another gid
> + if [ -n "${_gid}" -a ${_gid} -ne ${gid} ]; then
> + fail "group already exists with gid '${_gid}'\n"
> + fi
> +
> + # check the user does not already exists with another gid
> + if [ -n "${_ugid}" -a ${_ugid} -ne ${gid} ]; then
> + fail "user already exists with gid '${_ugid}'\n"
> + fi
> + fi
> +
> + if [ ${uid} -lt -1 -o ${uid} -eq 0 ]; then
> + fail "invalid uid '%d'\n" ${uid}
> + elif [ ${uid} -ne -1 ]; then
> + # check the uid is not already used for another user
> + if [ -n "${_username}" -a "${_username}" != "${username}" ]; then
> + fail "uid is already used by user '${_username}'\n"
> + fi
> +
> + # check the user does not already exists with another uid
> + if [ -n "${_uid}" -a ${_uid} -ne ${uid} ]; then
> + fail "user already exists with uid '${_uid}'\n"
> + fi
> + fi
If the user already exists, I would check that _all_ fields are exactly
the same. Otherwise, it depends on the order of evaluation of the .mk
files what will end up in the passwd/group file.
> +
> + # check the user does not already exist in another group
> + if [ -n "${_ugroup}" -a "${_ugroup}" != "${group}" ]; then
> + fail "user already exists with group '${_ugroup}'\n"
> + 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 [MIN_GID..MAX_GID]
> +# - not already used by a group
> +generate_gid() {
So you could factor generate_gid/uid into a single generate_id which
you call like:
generate_id ${group} ${GROUP} ${MIN_GID} ${MAX_GID}
> + local group="${1}"
> + local gid
> +
> + gid="$( get_gid "${group}" )"
> + if [ -z "${gid}" ]; then
> + for(( gid=MIN_GID; gid<=MAX_GID; gid++ )); do
> + if [ -z "$( get_group "${gid}" )" ]; then
> + break
> + fi
> + done
> + if [ ${gid} -gt ${MAX_GID} ]; then
> + fail "can not allocate a GID for group '%s'\n" "${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 _f
> +
> + # Generate a new GID if needed
> + if [ ${gid} -eq -1 ]; then
> + gid="$( generate_gid "${group}" )"
> + fi
> +
> + # Remove any previous instance of this group
> + for _f in "${GROUP}" "${GSHADOW}"; do
Since ${GROUP} always exists, I think having a loop here is harder to
read that just repeating the sed call.
> + [ -f "${_f}" ] || continue
> + sed -r -i -e '/^'"${group}"':.*/d;' "${_f}"
-r is redundant (it's a plain regex).
Quoting could be simpler:
sed -i -e "/^${group}:.*/d;" "${GROUP}"
> + done
> +
> + printf "%s:x:%d:\n" "${group}" "${gid}" >>"${GROUP}"
> + if [ -f "${GSHADOW}" ]; then
Instead of having the condition twice, just put the sed statement for
GSHADOW here.
> + 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 [MIN_UID..MAX_UID]
> +# - not already used by a user
> +generate_uid() {
> + local username="${1}"
> + local uid
> +
> + uid="$( get_uid "${username}" )"
> + if [ -z "${uid}" ]; then
> + for(( uid=MIN_UID; uid<=MAX_UID; uid++ )); do
> + if [ -z "$( get_username "${uid}" )" ]; then
> + break
> + fi
> + done
> + if [ ${uid} -gt ${MAX_UID} ]; then
> + fail "can not allocate a UID for user '%s'\n" "${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 -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 "${BR2_TARGET_GENERIC_PASSWD_METHOD}" "${passwd}"
Err, you defined it as PASSWD_METHOD above... But if you source
.config as I suggested, this is OK :-)
> +}
> +
> +#----------------------------------------------------------------------------
> +# 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="${9}"
> + local nb_days="$((($(date +%s)+(24*60*60-1))/(24*60*60)))"
Hm, I don't like this. If I re-run the same configuration after a year,
it gives me a different shadow.
I think the nb_days field in shadow should be left empty. The one in
the skeleton is arbitrarily set to Dec. 8 1999, it has been like that
since the first commit in 2001, and it has completely no meaning.
> + local _f _group _home _shell _gid _passwd
> +
> + # First, sanity-check the user
> + check_user_validity "${username}" "${uid}" "${group}" "${gid}"
> +
> + # Generate a new UID if needed
> + if [ ${uid} -eq -1 ]; then
> + uid="$( generate_uid "${username}" )"
> + fi
> +
> + # Remove any previous instance of this user
> + for _f in "${PASSWD}" "${SHADOW}"; do
> + sed -r -i -e '/^'"${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='!'"$( encode_passwd "${passwd#!=}" )"
> + ;;
> + =*)
> + _passwd="$( encode_passwd "${passwd#=}" )"
> + ;;
> + *)
> + _passwd="${passwd}"
> + ;;
> + esac
> +
> + printf "%s:x:%d:%d:%s:%s:%s\n" \
> + "${username}" "${uid}" "${_gid}" \
> + "${comment}" "${_home}" "${_shell}" \
> + >>"${PASSWD}"
> + printf "%s:%s:%d:0:99999:7:::\n" \
> + "${username}" "${_passwd}" "${nb_days}" \
> + >>"${SHADOW}"
> +
> + # Add the user to its additional groups
> + if [ "${groups}" != "-" ]; then
> + for _group in ${groups//,/ }; do
Oh, here's another bashism. But also one which is much more difficult
to write in Posix sh.
> + add_user_to_group "${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 -R %d:%d '%s'\n" "${uid}" "${_gid}" "${TARGET_DIR}/${home}"
> + fi
> +}
> +
> +#----------------------------------------------------------------------------
> +main() {
> + local username uid group gid passwd home shell groups comment
> +
> + # Some sanity checks
> + if [ ${MIN_UID} -le 0 ]; then
> + fail "MIN_UID must be >0 (currently %d)\n" ${MIN_UID}
> + fi
> + if [ ${MIN_GID} -le 0 ]; then
> + fail "MIN_GID must be >0 (currently %d)\n" ${MIN_GID}
> + fi
> +
> + # First, create all the main groups
> + while read username uid group gid passwd home shell groups comment; do
> + [ -n "${username}" ] || continue # Package with no user
> + add_one_group "${group}" "${gid}"
In the first pass, I would only add groups where gid != -1. Then, if
there is a line which sets gid and another one which doesn't, it still
works. Of course that means you have to repeat the add_one_group for gid
== -1 in the second pass.
> + done <"${USERS_TABLE}"
> +
> + # Then, create all the additional groups
> + # If any additional group is already a main group, we should use
> + # the gid of that main group; otherwise, we can use any gid
> + while read username uid group gid passwd home shell groups comment; do
> + [ -n "${username}" ] || continue # Package with no user
> + if [ "${groups}" != "-" ]; then
> + for g in ${groups//,/ }; do
> + add_one_group "${g}" -1
> + done
> + fi
> + done <"${USERS_TABLE}"
> +
> + # Finally, add users
> + while read username uid group gid passwd home shell groups comment; do
> + [ -n "${username}" ] || continue # Package with no user
> + add_one_user "${username}" "${uid}" "${group}" "${gid}" "${passwd}" \
> + "${home}" "${shell}" "${groups}" "${comment}"
If you reverse-sort the USERS_TABLE in the makefile before the script
is called, then you also make it possible for one package setting uid to
-1 and another giving a specific uid.
Regards,
Arnout
> + done <"${USERS_TABLE}"
> +}
> +
> +#----------------------------------------------------------------------------
> +main "${@}"
>
--
Arnout Vandecappelle arnout at mind be
Senior Embedded Software Architect +32-16-286500
Essensium/Mind http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint: 7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F
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