rc/sh/maybesudo

#!/usr/bin/env sh
# YES_ZSH
# YES_BASH
# YES_DASH
# YES_ASH

maybesudo_() ( ### @-
    ### mimic certain features of `sudo` for systems without it installed.
    ### as it stands, this mostly just handles some environment variables.
    ###
    ### try this: `maybesudo_ -u "$USER" printenv`

    name=
    env_cleanup=0

    while getopts :AEHKPSVbhiklnsvC:U:g:p:r:t:u: name; do
        case "$name" in
        K|V|k)
        # K: sure kill
        # V: version
        # k: kill
            note 'maybesudo: your system does not have sudo installed!'
            return 0
            ;;

        h)
            printf "%s\n" 'maybesudo - a dumb utility for systems without sudo'
            printf "\n"
            printf "%s\n" 'usage: maybesudo -h | -V'
            printf "%s\n" 'usage: maybesudo [command]'
            return 0
            ;;

        A|E|H|P|S|n|p)
        # A: askpass
        # E: preserve environment
        # H: HOME
        # P: preserve group vector
        # S: stdin (password)
        # n: non-interactive
        # p: prompt
            note 'maybesudo: option has no effect --' "'$name'"
            ;;

        C|U|b|g|i|l|r|s|t)
        # C: close from (fd)
        # U: other user (in conjunction wiht -l)
        # b: background
        # g: group
        # i: simulate initial login (TODO)
        # l: list
        # r: role (SELinux)
        # s: shell (TODO)
        # t: type (SELinux)
            note "maybesudo: unsupported option --" "'$name'"
            return 1
            ;;

        u)      # user
            if [ -z "$USER" -o "$OPTARG" != "$USER" ]; then
                note 'maybesudo: users other than yourself are unsupported!'
                return 1
            fi
            env_cleanup=1
            ;;

        :)
            note 'maybesudo: option requires an argument --' "'$OPTARG'"
            return 1
            ;;
        default)
            note 'maybesudo: invalid option --' "'$OPTARG'"
            return 1
            ;;
        esac
    done

    shift "$((OPTIND-1))"

    if [ "$env_cleanup" = 1 ]; then
        # portably listing exported variable names is virtually impossible
        # without the blessing of null-terminated strings, so don't even try.
        # just export the bare minimum that a fairly stock sudo would.
        # TODO: you know, awk has an ENVIRON array that might be easier to work with.

        # don't eat up precious command space with dumb colors.
        # xargs --show-limits says:
        # Maximum length of command we could actually use: 5080
        [ "${#LS_COLORS}" -le 1024 ] || LS_COLORS=

        # doas seems to override PATH with /bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
        # sudo also sets SUDO_COMMAND, SUDO_GID, SUDO_UID, SUDO_USER, and MAIL,
        # but who needs those?
        #   "${USER:+DOAS_USER}=${USER}"
        #   "${USER:+SUDO_USER}=${USER}"

        # coreutils treats '=' arguments as no-ops, but busybox does not, so...
        env -i \
            "${COLORS:+COLORS=}${COLORS:--i}" \
            "${DISPLAY:+DISPLAY=}${DISPLAY:--i}" \
            "${DPKG_COLORS:+DPKG_COLORS=}${DPKG_COLORS:--i}" \
            "${HOME:+HOME=}${HOME:--i}" \
            "${HOSTNAME:+HOSTNAME=}${HOSTNAME:--i}" \
            "${KRB5CCNAME:+KRB5CCNAME=}${KRB5CCNAME:--i}" \
            "${LOGNAME:+HOME=}${USER:--i}" \
            "${LS_COLORS:+LS_COLORS=}${LS_COLORS:--i}" \
            "${PATH:+PATH=}${PATH:--i}" \
            "${SHELL:+SHELL=}${SHELL:--i}" \
            "${TERM:+TERM=}${TERM:--i}" \
            "${USER:+USER=}${USER:--i}" \
            "${USERNAME:+USERNAME=}${USERNAME:--i}" \
            "${XAUTHORITY:+XAUTHORITY=}${XAUTHORITY:--i}" \
            "${XAUTHORIZATION:+XAUTHORIZATION=}${XAUTHORIZATION:--i}" \
            -- "$@"

    else
        # run it through env anyway for consistency.
        env -- "$@"
    fi

    # don't put any code here or you'll clobber $?.
)

[ -n "${preload+-}" ] || maybesudo_ "$@"