#!/bin/bash

# monkeysphere-server: MonkeySphere server admin tool
#
# The monkeysphere scripts are written by:
# Jameson Rollins <jrollins@fifthhorseman.net>
#
# They are Copyright 2008, and are all released under the GPL, version 3
# or later.

########################################################################
PGRM=$(basename $0)

SHARE=${SHARE:-"/usr/share/monkeysphere"}
export SHARE
. "${SHARE}/common" || exit 1

VARLIB="/var/lib/monkeysphere"
export VARLIB

# date in UTF format if needed
DATE=$(date -u '+%FT%T')

# unset some environment variables that could screw things up
GREP_OPTIONS=

# default return code
ERR=0

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

usage() {
cat <<EOF
usage: $PGRM <subcommand> [args]
MonkeySphere server admin tool.

subcommands:
  update-users (u) [USER]...            update users authorized_keys files
  gen-key (g) [HOSTNAME]                generate gpg key for the server
  show-fingerprint (f)                  show server's host key fingerprint
  publish-key (p)                       publish server's host key to keyserver
  add-certifier (a) KEYID               import and tsign a certification key
  remove-certifier (r) KEYID            remove a certification key
  list-certifiers (l)                   list certification keys
  help (h,?)                            this help

EOF
}

su_monkeysphere_user() {
    su --preserve-environment "$MONKEYSPHERE_USER" -- -c "$@"
}

# function to interact with the host gnupg keyring
gpg_host() {
    local returnCode

    GNUPGHOME="$GNUPGHOME_HOST"
    export GNUPGHOME

    # NOTE: we supress this warning because we need the monkeysphere
    # user to be able to read the host pubring.  we realize this might
    # be problematic, but it's the simplest solution, without too much
    # loss of security.
    gpg --no-permission-warning "$@"
    returnCode="$?"

    # always reset the permissions on the host pubring so that the
    # monkeysphere user can read the trust signatures
    chgrp "$MONKEYSPHERE_USER" "${GNUPGHOME_HOST}/pubring.gpg"
    chmod g+r "${GNUPGHOME_HOST}/pubring.gpg"
    
    return "$returnCode"
}

# function to interact with the authentication gnupg keyring
gpg_authentication() {
    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
    export GNUPGHOME

    su_monkeysphere_user "gpg $@"
}

# update authorized_keys for users
update_users() {
    if [ "$1" ] ; then
	# get users from command line
	unames="$@"
    else
	# or just look at all users if none specified
	unames=$(getent passwd | cut -d: -f1)
    fi

    # set mode
    MODE="authorized_keys"

    # set gnupg home
    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"

    # check to see if the gpg trust database has been initialized
    if [ ! -s "${GNUPGHOME}/trustdb.gpg" ] ; then
	failure "GNUPG trust database uninitialized.  Please see MONKEYSPHERE-SERVER(8)."
    fi

    # make sure the authorized_keys directory exists
    mkdir -p "${VARLIB}/authorized_keys"

    # loop over users
    for uname in $unames ; do
	# check all specified users exist
	if ! getent passwd "$uname" >/dev/null ; then
	    error "----- unknown user '$uname' -----"
	    continue
	fi

	# set authorized_user_ids and raw authorized_keys variables,
	# translating ssh-style path variables
	authorizedUserIDs=$(translate_ssh_variables "$uname" "$AUTHORIZED_USER_IDS")
	rawAuthorizedKeys=$(translate_ssh_variables "$uname" "$RAW_AUTHORIZED_KEYS")

	# if neither is found, skip user
	if [ ! -s "$authorizedUserIDs" ] ; then
	    if [ "$rawAuthorizedKeys" = '-' -o ! -s "$rawAuthorizedKeys" ] ; then
		continue
	    fi
	fi

	log "----- user: $uname -----"

        # make temporary directory
        TMPDIR=$(mktemp -d)

	# trap to delete temporary directory on exit
	trap "rm -rf $TMPDIR" EXIT

        # create temporary authorized_user_ids file
        TMP_AUTHORIZED_USER_IDS="${TMPDIR}/authorized_user_ids"
        touch "$TMP_AUTHORIZED_USER_IDS"

        # create temporary authorized_keys file
        AUTHORIZED_KEYS="${TMPDIR}/authorized_keys"
        touch "$AUTHORIZED_KEYS"

        # set restrictive permissions on the temporary files
	# FIXME: is there a better way to do this?
        chmod 0700 "$TMPDIR"
        chmod 0600 "$AUTHORIZED_KEYS"
        chmod 0600 "$TMP_AUTHORIZED_USER_IDS"
        chown -R "$MONKEYSPHERE_USER" "$TMPDIR"

	# if the authorized_user_ids file exists...
	if [ -s "$authorizedUserIDs" ] ; then
            # copy user authorized_user_ids file to temporary
            # location
	    cat "$authorizedUserIDs" > "$TMP_AUTHORIZED_USER_IDS"

	    # export needed variables
	    export AUTHORIZED_KEYS
	    export TMP_AUTHORIZED_USER_IDS

	    # process authorized_user_ids file, as monkeysphere
	    # user
	    su_monkeysphere_user \
		". ${SHARE}/common; process_authorized_user_ids $TMP_AUTHORIZED_USER_IDS"
	    ERR="$?"
	fi

	# add user-controlled authorized_keys file path if specified
	if [ "$rawAuthorizedKeys" != '-' -a -s "$rawAuthorizedKeys" ] ; then
	    log -n "adding raw authorized_keys file... "
	    cat "$rawAuthorizedKeys" >> "$AUTHORIZED_KEYS"
	    loge "done."
	fi

	# openssh appears to check the contents of the
        # authorized_keys file as the user in question, so the
        # file must be readable by that user at least.
	# FIXME: is there a better way to do this?
	chown root "$AUTHORIZED_KEYS"
	chgrp $(getent passwd "$uname" | cut -f4 -d:) "$AUTHORIZED_KEYS"
	chmod g+r "$AUTHORIZED_KEYS"

	# if the resulting authorized_keys file is not empty, move
	# it into place
	mv -f "$AUTHORIZED_KEYS" "${VARLIB}/authorized_keys/${uname}"

	# destroy temporary directory
	rm -rf "$TMPDIR"
    done
}

# generate server gpg key
gen_key() {
    local hostName
    local userID
    local keyParameters
    local fingerprint

    hostName=${1:-$(hostname --fqdn)}

    SERVICE=${SERVICE:-"ssh"}
    userID="${SERVICE}://${hostName}"

    if gpg_host --list-key ="$userID" > /dev/null 2>&1 ; then
	failure "Key for '$userID' already exists"
    fi

    # set key defaults
    KEY_TYPE=${KEY_TYPE:-"RSA"}
    KEY_LENGTH=${KEY_LENGTH:-"2048"}
    KEY_USAGE=${KEY_USAGE:-"auth"}
    KEY_EXPIRE=${KEY_EXPIRE:-"0"}
    cat <<EOF
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
EOF
    read -p "Key is valid for? ($KEY_EXPIRE) " KEY_EXPIRE; KEY_EXPIRE=${KEY_EXPIRE:-"0"}

    # set key parameters
    keyParameters=$(cat <<EOF
Key-Type: $KEY_TYPE
Key-Length: $KEY_LENGTH
Key-Usage: $KEY_USAGE
Name-Real: $userID
Expire-Date: $KEY_EXPIRE
EOF
)

    # add the revoker field if specified
    # FIXME: the "1:" below assumes that $REVOKER's key is an RSA key.  why?
    # FIXME: why is this marked "sensitive"?  how will this signature ever
    # be transmitted to the expected revoker?
    if [ "$REVOKER" ] ; then
	keyParameters="${keyParameters}"$(cat <<EOF

Revoker: 1:$REVOKER sensitive
EOF
)
    fi

    echo "The following key parameters will be used for the host private key:"
    echo "$keyParameters"

    read -p "Generate key? (Y/n) " OK; OK=${OK:=Y}
    if [ ${OK/y/Y} != 'Y' ] ; then
	failure "aborting."
    fi

    # add commit command
    keyParameters="${keyParameters}"$(cat <<EOF

%commit
%echo done
EOF
)

    log "generating server key..."
    echo "$keyParameters" | gpg_host --batch --gen-key

    # output the server fingerprint
    fingerprint_server_key "=${userID}"

    # find the key fingerprint of the server primary key
    fingerprint=$(gpg_host --list-key --with-colons --with-fingerprint "=${userID}" | \
	grep '^fpr:' | head -1 | cut -d: -f10)

    # translate the private key to ssh format, and export to a file
    # for sshs usage.
    # NOTE: assumes that the primary key is the proper key to use
    (umask 077 && \
	gpg_host --export-secret-key "$fingerprint" | \
	openpgp2ssh "$fingerprint" > "${VARLIB}/ssh_host_rsa_key")
    log "Private SSH host key output to file: ${VARLIB}/ssh_host_rsa_key"
}

# gpg output key fingerprint
fingerprint_server_key() {
    gpg_host --fingerprint --list-secret-keys
}

# publish server key to keyserver
publish_server_key() {
    read -p "really publish key to $KEYSERVER? (y/N) " OK; OK=${OK:=N}
    if [ ${OK/y/Y} != 'Y' ] ; then
	failure "aborting."
    fi

    # publish host key
    # FIXME: need to figure out better way to identify host key
    # dummy command so as not to publish fakes keys during testing
    # eventually:
    #gpg_authentication "--keyring $GNUPGHOME_HOST/pubring.gpg --keyserver $KEYSERVER --send-keys $(hostname -f)"
    failure "NOT PUBLISHED (to avoid permanent publication errors during monkeysphere development)."
}

# retrieve key from web of trust, import it into the host keyring, and
# ltsign the key in the host keyring so that it may certify other keys
add_certifier() {
    local keyID
    local fingerprint
    local ltsignCommand

    keyID="$1"
    export keyID

    # export host ownertrust to authentication keyring
    gpg_host --export-ownertrust | gpg_authentication "--import-ownertrust"

    # get the key from the key server
    gpg_authentication "--keyserver $KEYSERVER --recv-key $keyID"

    # get the full fingerprint of a key ID
    fingerprint=$(gpg_authentication "--list-key --with-colons --with-fingerprint $keyID" | \
	grep '^fpr:' | grep "$keyID" | cut -d: -f10)

    if [ -z "$fingerprint" ] ; then
	failure "Could not find key '$keyID'."
    fi

    echo "key found:"
    gpg_authentication "--fingerprint $fingerprint"

    read -p "Are you sure you want to add this key as a certifier of users on this system? (y/N) " OK; OK=${OK:-N}
    if [ "${OK/y/Y}" != 'Y' ] ; then
	failure "aborting."
    fi

    # export the key to the host keyring
    gpg_authentication "--export $keyID" | gpg_host --import

    # default values for trust depth and domain
    DEPTH=${DEPTH:-1}
    DOMAIN=${DOMAIN:-}

    # ltsign command
    # NOTE: *all* user IDs will be ltsigned
    ltsignCommand=$(cat <<EOF
ltsign
y
2
$DEPTH
$DOMAIN
y
save
EOF
)

    # ltsign the key
    echo "$ltsignCommand" | gpg_host --quiet --command-fd 0 --edit-key "$fingerprint"

    # update the trustdb for the authentication keyring
    gpg_authentication "--check-trustdb"
}

# delete a certifiers key from the host keyring
remove_certifier() {
    local keyID
    local fingerprint

    keyID="$1"

    # delete the requested key (with prompting)
    gpg_host --delete-key "$keyID"

    # update the trustdb for the authentication keyring
    gpg_authentication "--check-trustdb"
}

# list the host certifiers
list_certifiers() {
    gpg_host --list-keys
}

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

COMMAND="$1"
[ "$COMMAND" ] || failure "Type '$PGRM help' for usage."
shift

# load configuration file
MS_CONF=${MS_CONF:-"${ETC}/monkeysphere-server.conf"}
[ -e "$MS_CONF" ] && . "$MS_CONF"

# set empty config variable with defaults
MONKEYSPHERE_USER=${MONKEYSPHERE_USER:-"monkeysphere"}
KEYSERVER=${KEYSERVER:-"subkeys.pgp.net"}
CHECK_KEYSERVER=${CHECK_KEYSERVER:="true"}
AUTHORIZED_USER_IDS=${AUTHORIZED_USER_IDS:-"%h/.config/monkeysphere/authorized_user_ids"}
RAW_AUTHORIZED_KEYS=${RAW_AUTHORIZED_KEYS:-"%h/.ssh/authorized_keys"}

# other variables
REQUIRED_USER_KEY_CAPABILITY=${REQUIRED_USER_KEY_CAPABILITY:-"a"}
GNUPGHOME_HOST=${GNUPGHOME_HOST:-"${VARLIB}/gnupg-host"}
GNUPGHOME_AUTHENTICATION=${GNUPGHOME_AUTHENTICATION:-"${VARLIB}/gnupg-authentication"}

# export variables
export DATE
export MODE
export MONKEYSPHERE_USER
export KEYSERVER
export CHECK_KEYSERVER
export REQUIRED_USER_KEY_CAPABILITY
export GNUPGHOME_HOST
export GNUPGHOME_AUTHENTICATION
export GNUPGHOME

case $COMMAND in
    'update-users'|'update-user'|'u')
	update_users "$@"
	;;

    'gen-key'|'g')
	gen_key "$@"
	;;

    'show-fingerprint'|'f')
	fingerprint_server_key
	;;

    'publish-key'|'p')
	publish_server_key
	;;

    'add-certifier'|'a')
	if [ -z "$1" ] ; then
	    failure "You must specify a key ID."
	fi
	add_certifier "$1"
	;;

    'remove-certifier'|'r')
	if [ -z "$1" ] ; then
	    failure "You must specify a key ID."
	fi
	remove_certifier "$1"
	;;

    'list-certifiers'|'l')
	list_certifiers "$@"
	;;

    'help'|'h'|'?')
        usage
        ;;

    *)
        failure "Unknown command: '$COMMAND'
Type '$PGRM help' for usage."
        ;;
esac

exit "$ERR"