[Buildroot] [PATCH 1/2] packages: add ability for packages to create users

Yann E. MORIN yann.morin.1998 at free.fr
Wed Feb 6 22:59:47 UTC 2013


On Wednesday 06 February 2013 Arnout Vandecappelle wrote:
>   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
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
> 
> 

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