sudok

#!/bin/sh
#-
############################################################ IDENT(1)
#
# $Title: Script to provide interactive shell that answers sudo prompts $
# $Copyright: 2019 Devin Teske. All rights reserved. $
# $FrauBSD$
#
############################################################ ENVIRONMENT

: "${USER:=$( id -nu )}"
: "${HOSTNAME:=$( hostname )}"
export USER HOSTNAME

SUDO_PROMPT="[sudo] Password:"
SUDO_PROMPT_RE="\\[sudo\\] [Pp]assword( for $USER)?: *"
export SUDO_PROMPT SUDO_PROMPT_RE

############################################################ GLOBALS

pgm="${0##*/}" # Program basename
progdir="${0%/*}" # Program directory

#
# Global exit status
#
SUCCESS=0
FAILURE=1

############################################################ FUNCTIONS

usage()
{
        local optfmt="\t%-5s %s\n"
        exec >&2
        printf "Usage: %s [-h]\n" "$pgm"
        printf "Options:\n"
        printf "$optfmt" "-h" "Print usage statement to stderr and exit."
        die
}

die()
{
        local fmt="$1"
        if [ "$fmt" ]; then
                shift 1 # fmt
                printf "%s: $fmt\n" "$pgm" "$@"
        fi
        exit $FAILURE
}

make_expect()
{
        local var=$1
        shift 1 # var
        exec 9<<-EOF
        set okprompt    "$pgm> "
        set timeout     -1
        set user        $::env(USER)
        set hostname    $::env(HOSTNAME)
        set argv        $::env(COMMAND)

        $( n=1; for key_value in "$@"; do
                prompt="${key_value%%=*}"
                re="${key_value#*=}"
                printf '\nset prompt%u\t$::env(%s)' $n $prompt
                printf '\nset promptre%u\t$::env(%s)' $n $re
                n=$(( $n + 1 ))
        done )

        regsub -all {\..*} \$hostname {} hostname

        set shell_prompts ""
        foreach shell_prompt [list \
                [subst -nocommand -nobackslashes \
                        {\$user@\$hostname[^\n\r]*$}] \
                [subst -nocommand -nobackslashes \
                        {\$user@\$hostname[^\n\r]*[#%>]}] \
        ] {
                set shell_prompts [subst -nocommand -nobackslashes \
                        {\$shell_prompts|\$shell_prompt}]
        }
        set shell_prompts [string range \$shell_prompts 1 \
                [string length \$shell_prompts]]

        set prompts ""
        foreach prompt [list \
                [subst -nocommand -nobackslashes {\$shell_prompts}] \
                $( n=0; for key_value in "$@"; do
                        n=$(( $n + 1 ))
                        printf '[subst %s {$%s}] \\\n' \
                                "-nocommand -nobackslashes" promptre$n
                done ) \
        ] {
                set prompts [subst -nocommand -nobackslashes \
                        {\$prompts|\$prompt}]
        }
        set prompts [string range \$prompts 1 [string length \$prompts]]

        fconfigure stdout -buffering none
        spawn {*}\$argv

        # Get prompt answers
        stty -echo
        $( n=1; for key_value in "$@"; do
                printf 'send_user "$%s"\n' prompt$n
                printf 'expect_tty eof exit -re {([[:print:]]*)\\n}\n'
                printf 'send_user "\\n"\n'
                printf 'set %s $expect_out(1,string)\n' answer$n
        done )
        stty echo

        proc abort {} {
                log_user 0
                exit 0
        }

        while (1) {
                expect eof abort -re [subst -nocommands -nobackslashes \
                        {[^\n\r]*(\$prompts)\s*$}]
                set buffer \$expect_out(0,string)

                # shell prompt(s)
                if {[regexp [subst -nocommands -nobackslashes \
                        {^[^\n\r]*(\$shell_prompts)\s*$}] \$buffer]} \
                {
                        send_tty \$okprompt
                        interact eof abort \
                                -nobuffer -re {[\r\003\004]} {return} \
                }

                # defined prompt(s)
                $( n=0; for key_value in "$@"; do
                        n=$(( $n + 1 ))
                        printf 'if {[regexp [subst %s {^$%s$}] $buffer]} ' \
                                "-nocommands -nobackslashes" promptre$n
                        printf '{ send "$%s\\r" }\n' answer$n
                done )
        }
        EOF
        eval $var='$( cat <&9 )'
}

############################################################ MAIN

#
# Parse command-line options
#
while getopts h flag; do
        case "$flag" in
        *) usage # NOTREACHED
        esac
done
shift $(( $OPTIND - 1 ))

#
# Run command
#
make_expect EXPECT_SUDO SUDO_PROMPT=SUDO_PROMPT_RE
export EXPECT_SUDO COMMAND="${*:-$( ps -o ucomm= -p $PPID )} -l"
expect -c 'eval $::env(EXPECT_SUDO)'

################################################################################
# END
################################################################################