#!/bin/bash

# webaccess
# Manage access control for scripts.mit.edu in .htaccess and .htpasswd files.
# Anders Kaseorg <andersk@mit.edu>

set -e

on_exit=
trap 'eval "$on_exit"' EXIT

dir="$(pwd)"
htaccess=$dir/.htaccess
authuserfile=$dir/.htpasswd

add_users=
del_users=
enable_auth=1
def_authname=\"Private\"

begin_section="### BEGIN webaccess directives"
end_section="### END webaccess directives"

usage () {
    cat <<EOF >&2
usage:
  webaccess -a <user>   Allow access from <user> and set password.
  webaccess -d <user>   Deny access from <user>.
  webaccess -r          Reset default access control.
EOF
    exit 1
}

getpass () {
    user=$1
    (
	echo -n "New password for $user: " >/dev/tty
	trap 'stty echo; echo >/dev/tty' EXIT
	stty -echo
	perl -e 'chop($_ = <>); print crypt($_, "\$1\$" . join "", (".", "/", "0".."9", "A".."Z", "a".."z") [rand 64, rand 64, rand 64, rand 64, rand 64, rand 64, rand 64, rand 64])' </dev/tty
    )
}

if [ $# -eq 0 ]; then usage; fi

while [ $# -gt 0 ]; do
    arg="$1"; shift
    case "$arg" in
	-a*)
	    user="${arg#-a}"
	    if [ -z "$user" ]; then user=$1; shift; fi
	    if [ -z "$user" ]; then usage; fi
	    add_users=$add_users\ $user
	    ;;
	allow)
	    user="$1"; shift
	    if [ -z "$user" ]; then usage; fi
	    add_users=$add_users\ $user
	    ;;
	-d*)
	    user="${arg#-d}"
	    if [ -z "$user" ]; then user=$1; shift; fi
	    if [ -z "$user" ]; then usage; fi
	    del_users=$del_users\ $user
	    ;;
	remove)
	    user="$1"; shift
	    if [ -z "$user" ]; then usage; fi
	    del_users=$del_users\ $user
	    ;;
	-r|reset)
	    enable_auth=0
	    ;;
	-n*)
	    authname="${arg#-n}"
	    if [ -z "$authname" ]; then authname=\"$1\"; shift; fi
	    if [ -z "$authname" ]; then usage; fi
	    ;;
	*)
	    usage
	    ;;
    esac
done

tmp_htaccess=$htaccess.webaccess-new
trap 'rm -f "$tmp_htaccess"' EXIT
exec 3>"$tmp_htaccess"

config_written=0
write_config () {
    if [ $config_written -eq 1 ]; then return 0; fi
    config_written=1
    if [ $enable_auth -eq 1 ]; then
	echo "$begin_section" >&3
	echo "# See http://scripts.mit.edu/faq/23" >&3
	echo "AuthUserFile $authuserfile" >&3
	echo "AuthName ${authname:-$def_authname}" >&3
	echo "AuthType Basic" >&3
	echo "Require valid-user" >&3
	echo "$end_section" >&3
    fi
}

if [ -e "$htaccess" ]; then
    exec 4<"$htaccess"
    
    oldconfig_state=0
    oldconfig_buffer=__END__
    
    while read -r line <&4; do
	oldconfig_newstate=0
	case "$line" in
	    "AuthUserFile "*)     oldconfig_newstate=1 ;;
	    "AuthName "*)         oldconfig_newstate=2; oldconfig_authname=${line#AuthName } ;;
	    "AuthType Basic")     oldconfig_newstate=3 ;;
	    "<Limit GET>")        oldconfig_newstate=4 ;;
	    "require valid-user") oldconfig_newstate=5 ;;
	    "</Limit>")           oldconfig_newstate=6 ;;
	esac
	
	if [ $oldconfig_newstate -ne $(($oldconfig_state + 1)) ]; then
	    if [ $oldconfig_state -ne 0 ]; then
		echo "${oldconfig_buffer%
__END__}" >&3
		oldconfig_state=0
		oldconfig_buffer=__END__
	    fi
	fi
	
	if [ "$line" = "$begin_section" ]; then
	    while read -r line <&4 && [ "$line" != "$end_section" ]; do
		case "$line" in
		    "AuthName "*)
			def_authname=${line#AuthName }
			;;
		esac
	    done
	    write_config
	elif [ $oldconfig_newstate -eq $(($oldconfig_state + 1)) ]; then
	    oldconfig_buffer=$(echo "${oldconfig_buffer%__END__}$line"; echo __END__)
	    oldconfig_state=$oldconfig_newstate
	    if [ $oldconfig_state -eq 6 ]; then
		echo "Replacing obsolete webaccess configuration." >&2
		oldconfig_state=0
		oldconfig_buffer=__END__
		def_authname=$oldconfig_authname
	    fi
	else
	    echo "$line" >&3
	fi
    done
    
    if [ $oldconfig_state -ne 0 ]; then
	echo "${oldconfig_buffer%
__END__}"
	oldconfig_state=0
	oldconfig_buffer=__END__
    fi
    
    exec 4<&-
fi

write_config

exec 3>&-
if ! cmp -s "$htaccess" "$tmp_htaccess"; then
    if [ -s "$tmp_htaccess" ]; then
	echo "Updating $htaccess" >&2
	mv -f "$tmp_htaccess" "$htaccess"
    else
	if [ -e "$htaccess" ]; then
	    echo "Deleting $htaccess" >&2
	    rm -f "$htaccess"
	fi
	rm -f "$tmp_htaccess"
    fi
fi
trap - EXIT

if [ $enable_auth -eq 1 ]; then
    if [ ! -e "$authuserfile" ]; then touch "$authuserfile"; fi
    
    tmp_authuserfile=$authuserfile.webaccess-new
    trap 'rm -f "$tmp_authuserfile"' EXIT
    exec 3>"$tmp_authuserfile"

    exec 4<"$authuserfile"
    while IFS=: read user pass <&4; do
	for del_user in $del_users; do
	    if [ "$del_user" = "$user" ]; then
		echo "Deleting user $del_user:" >&2
		pass=
	    fi
	done
	new_add_users=
	for add_user in $add_users; do
	    if [ "$add_user" = "$user" ]; then
		pass=$(getpass "$user")
	    else
		new_add_users=$new_add_users\ $add_user
	    fi
	done
	add_users=$new_add_users
	if [ -n "$pass" ]; then
	    echo "$user:$pass" >&3
	fi
    done
    exec 4<&-
    
    for add_user in $add_users; do
	pass=$(getpass "$add_user")
	echo "$add_user:$pass" >&3
    done
    
    exec 3>&-
    mv -f "$tmp_authuserfile" "$authuserfile"
    trap - EXIT
    
    echo "Done.  New list of valid users:" >&2
    sed -n 's/^\([^:]*\):.*$/  \1/ p' "$authuserfile"
else
    rm -f "$authuserfile"
fi
