path: root/src/monkeysphere-server

#!/bin/bash

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

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

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

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

# UTC date in ISO 8601 format if needed
DATE=$(date -u '+%FT%T')

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

# default return code
RETURN=0

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

usage() {
    cat <<EOF >&2
usage: $PGRM <subcommand> [options] [args]
MonkeySphere server admin tool.

subcommands:
 update-users (u) [USER]...          update user authorized_keys files

 gen-key (g) [NAME[:PORT]]           generate gpg key for the server
   --length (-l) BITS                  key length in bits (2048)
   --expire (-e) EXPIRE                date to expire
   --revoker (-r) FINGERPRINT          add a revoker
 extend-key (e) EXPIRE               extend expiration to EXPIRE
 add-hostname (n+) NAME[:PORT]       add hostname user ID to server key
 revoke-hostname (n-) NAME[:PORT]    revoke hostname user ID
 show-key (s)                        output all server host key information
 publish-key (p)                     publish server host key to keyserver
 diagnostics (d)                     report on server monkeysphere status

 add-id-certifier (c+) KEYID         import and tsign a certification key
   --domain (-n) DOMAIN                limit ID certifications to DOMAIN
   --trust (-t) TRUST                  trust level of certifier (full)
   --depth (-d) DEPTH                  trust depth for certifier (1)
 remove-id-certifier (c-) KEYID      remove a certification key
 list-id-certifiers (c)              list certification keys

 gpg-authentication-cmd CMD          gnupg-authentication command

 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
# FIXME: this function requires basically accepts only a single
# argument because of problems with quote expansion.  this needs to be
# fixed/improved.
gpg_authentication() {
    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
    export GNUPGHOME

    su_monkeysphere_user "gpg $@"
}

# output just key fingerprint
fingerprint_server_key() {
    gpg_host --list-secret-keys --fingerprint \
    --with-colons --fixed-list-mode 2> /dev/null | \
    grep '^fpr:' | head -1 | cut -d: -f10
}

# output key information
show_server_key() {
    local fingerprint
    local tmpkey

    fingerprint=$(fingerprint_server_key)
    gpg_authentication "--fingerprint --list-key --list-options show-unusable-uids $fingerprint"

    # dumping to a file named ' ' so that the ssh-keygen output
    # doesn't claim any potentially bogus hostname(s):
    tmpkey=$(mktemp -d)
    gpg_authentication "--export $fingerprint" | openpgp2ssh "$fingerprint" 2>/dev/null > "$tmpkey/ "
    echo -n "ssh fingerprint: "
    (cd "$tmpkey" && ssh-keygen -l -f ' ' | awk '{ print $2 }')
    rm -rf "$tmpkey"
    echo -n "OpenPGP fingerprint: "
    echo "$fingerprint"
}

# 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
        log 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 verbose "----- user: $uname -----"

        # exit if the authorized_user_ids file is empty
    if ! check_key_file_permissions "$uname" "$AUTHORIZED_USER_IDS" ; then
        log error "Improper permissions on path '$AUTHORIZED_USER_IDS'."
        continue
    fi

    # check permissions on the authorized_keys file path
    if ! check_key_file_permissions "$uname" "$RAW_AUTHORIZED_KEYS" ; then
        log error "Improper permissions on path '$RAW_AUTHORIZED_KEYS'."
        continue
    fi

        # 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 $TMP_AUTHORIZED_USER_IDS"
        RETURN="$?"
    fi

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

    # move the resulting authorized_keys file into place
    mv -f "$AUTHORIZED_KEYS" "${VARLIB}/authorized_keys/${uname}"

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

# generate server gpg key
gen_key() {
    local keyType
    local keyLength
    local keyUsage
    local keyExpire
    local revoker
    local hostName
    local userID
    local keyParameters
    local fingerprint

    # set default key parameter values
    keyType="RSA"
    keyLength="2048"
    keyUsage="auth"
    keyExpire=
    revoker=

    # get options
    TEMP=$(getopt -o e:l:r -l expire:,length:,revoker: -n "$PGRM" -- "$@")

    if [ $? != 0 ] ; then
    exit 1
    fi

    # Note the quotes around `$TEMP': they are essential!
    eval set -- "$TEMP"

    while true ; do
    case "$1" in
        -l|--length)
        keyLength="$2"
        shift 2
        ;;
        -e|--expire)
        keyExpire="$2"
        shift 2
        ;;
        -r|--revoker)
        revoker="$2"
        shift 2
        ;;
        --)
        shift
        ;;
            *)
        break
        ;;
    esac
    done

    hostName=${1:-$(hostname --fqdn)}
    userID="ssh://${hostName}"

    # check for presense of key with user ID
    if gpg_host --list-key ="$userID" > /dev/null 2>&1 ; then
    failure "Key for '$userID' already exists"
    fi

    # prompt about key expiration if not specified
    keyExpire=$(get_gpg_expiration "$keyExpire")

    # set key parameters
    keyParameters=$(cat <<EOF
Key-Type: $keyType
Key-Length: $keyLength
Key-Usage: $keyUsage
Name-Real: $userID
Expire-Date: $keyExpire
EOF
)

    # add the revoker field if specified
    # FIXME: the "1:" below assumes that $REVOKER's key is an RSA key.
    # FIXME: key is marked "sensitive"?  is this appropriate?
    if [ "$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 verbose "generating server key..."
    echo "$keyParameters" | gpg_host --batch --gen-key

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

    # find the key fingerprint of the newly generated key
    fingerprint=$(fingerprint_server_key)

    # export host ownertrust to authentication keyring
    log verbose "setting ultimate owner trust for server key..."
    echo "${fingerprint}:6:" | gpg_authentication "--import-ownertrust"

    # 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 info "Private SSH host key output to file: ${VARLIB}/ssh_host_rsa_key"
}

# extend the lifetime of a host key:
extend_key() {
    local fpr=$(fingerprint_server_key)
    local extendTo="$1"

    if [ -z "$fpr" ] ; then
    failure "You don't appear to have a MonkeySphere host key on this server.  Try 'monkeysphere-server gen-key' first."
    fi

    # get the new expiration date
    extendTo=$(get_gpg_expiration "$extendTo")

    gpg_host --quiet --command-fd 0 --edit-key "$fpr" <<EOF 
expire
$extendTo
save
EOF

    echo
    echo "NOTE: Host key expiration date adjusted, but not yet published."
    echo "Run '$PGRM publish-key' to publish the new expiration date."
}

# add hostname user ID to server key
add_hostname() {
    local userID
    local fingerprint
    local tmpuidMatch
    local line
    local adduidCommand

    if [ -z "$1" ] ; then
    failure "You must specify a hostname to add."
    fi

    userID="ssh://${1}"

    fingerprint=$(fingerprint_server_key)

    # match to only ultimately trusted user IDs
    tmpuidMatch="u:$(echo $userID | gpg_escape)"

    # find the index of the requsted user ID
    # NOTE: this is based on circumstantial evidence that the order of
    # this output is the appropriate index
    if line=$(gpg_host --list-keys --with-colons --fixed-list-mode "0x${fingerprint}!" \
    | egrep '^(uid|uat):' | cut -f2,10 -d: | grep -n -x -F "$tmpuidMatch") ; then
    failure "Host userID '$userID' already exists."
    fi

    echo "The following user ID will be added to the host key:"
    echo "  $userID"
    read -p "Are you sure you would like to add this user ID? (y/N) " OK; OK=${OK:=N}
    if [ ${OK/y/Y} != 'Y' ] ; then
    failure "User ID not added."
    fi

    # edit-key script command to add user ID
    adduidCommand=$(cat <<EOF
adduid
$userID


save
EOF
    )

    # execute edit-key script
    if echo "$adduidCommand" | \
    gpg_host --quiet --command-fd 0 --edit-key "0x${fingerprint}!" ; then

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

    show_server_key

    echo
    echo "NOTE: User ID added to key, but key not published."
    echo "Run '$PGRM publish-key' to publish the new user ID."
    else
    failure "Problem adding user ID."
    fi
}

# revoke hostname user ID to server key
revoke_hostname() {
    local userID
    local fingerprint
    local tmpuidMatch
    local line
    local uidIndex
    local message
    local revuidCommand

    if [ -z "$1" ] ; then
    failure "You must specify a hostname to revoke."
    fi

    echo "WARNING: There is a known bug in this function."
    echo "This function has been known to occasionally revoke the wrong user ID."
    echo "Please see the following bug report for more information:"
    echo "http://web.monkeysphere.info/bugs/revoke-hostname-revoking-wrong-userid/"
    read -p "Are you sure you would like to proceed? (y/N) " OK; OK=${OK:=N}
    if [ ${OK/y/Y} != 'Y' ] ; then
    failure "aborting."
    fi

    userID="ssh://${1}"

    fingerprint=$(fingerprint_server_key)

    # match to only ultimately trusted user IDs
    tmpuidMatch="u:$(echo $userID | gpg_escape)"

    # find the index of the requsted user ID
    # NOTE: this is based on circumstantial evidence that the order of
    # this output is the appropriate index
    if line=$(gpg_host --list-keys --with-colons --fixed-list-mode "0x${fingerprint}!" \
    | egrep '^(uid|uat):' | cut -f2,10 -d: | grep -n -x -F "$tmpuidMatch") ; then
    uidIndex=${line%%:*}
    else
    failure "No non-revoked user ID '$userID' is found."
    fi

    echo "The following host key user ID will be revoked:"
    echo "  $userID"
    read -p "Are you sure you would like to revoke this user ID? (y/N) " OK; OK=${OK:=N}
    if [ ${OK/y/Y} != 'Y' ] ; then
    failure "User ID not revoked."
    fi

    message="Hostname removed by monkeysphere-server $DATE"

    # edit-key script command to revoke user ID
    revuidCommand=$(cat <<EOF
$uidIndex
revuid
y
4
$message

y
save
EOF
    )   

    # execute edit-key script
    if echo "$revuidCommand" | \
    gpg_host --quiet --command-fd 0 --edit-key "0x${fingerprint}!" ; then

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

    show_server_key

    echo
    echo "NOTE: User ID revoked, but revocation not published."
    echo "Run '$PGRM publish-key' to publish the revocation."
    else
    failure "Problem revoking user ID."
    fi
}

# publish server key to keyserver
publish_server_key() {
    read -p "Really publish host key to $KEYSERVER? (y/N) " OK; OK=${OK:=N}
    if [ ${OK/y/Y} != 'Y' ] ; then
    failure "key not published."
    fi

    # find the key fingerprint
    fingerprint=$(fingerprint_server_key)

    # publish host key
    gpg_authentication "--keyserver $KEYSERVER --send-keys '0x${fingerprint}!'"
}

diagnostics() {
#  * check on the status and validity of the key and public certificates
    local seckey
    local keysfound
    local curdate
    local warnwindow
    local warndate
    local create
    local expire
    local uid
    local fingerprint
    local badhostkeys
    local sshd_config

    # FIXME: what's the correct, cross-platform answer?
    sshd_config=/etc/ssh/sshd_config
    seckey=$(gpg_host --list-secret-keys --fingerprint --with-colons --fixed-list-mode)
    keysfound=$(echo "$seckey" | grep -c ^sec:)
    curdate=$(date +%s)
    # warn when anything is 2 months away from expiration
    warnwindow='2 months'
    warndate=$(date +%s -d "$warnwindow")

    if ! id monkeysphere >/dev/null ; then
    echo "! No monkeysphere user found!  Please create a monkeysphere system user."
    fi

    if ! [ -d "$VARLIB" ] ; then
    echo "! no $VARLIB directory found.  Please create it."
    fi

    echo "Checking host GPG key..."
    if (( "$keysfound" < 1 )); then
    echo "! No host key found."
    echo " - Recommendation: run 'monkeysphere-server gen-key'"
    elif (( "$keysfound" > 1 )); then
    echo "! More than one host key found?"
    # FIXME: recommend a way to resolve this
    else
    create=$(echo "$seckey" | grep ^sec: | cut -f6 -d:)
    expire=$(echo "$seckey" | grep ^sec: | cut -f7 -d:)
    fingerprint=$(echo "$seckey" | grep ^fpr: | head -n1 | cut -f10 -d:)
    # check for key expiration:
    if [ "$expire" ]; then
        if (( "$expire"  < "$curdate" )); then
        echo "! Host key is expired."
        echo " - Recommendation: extend lifetime of key with 'monkeysphere-server extend-key'"
        elif (( "$expire" < "$warndate" )); then
        echo "! Host key expires in less than $warnwindow:" $(date -d "$(( $expire - $curdate )) seconds" +%F)
        echo " - Recommendation: extend lifetime of key with 'monkeysphere-server extend-key'"
        fi
    fi

        # and weirdnesses:
    if [ "$create" ] && (( "$create" > "$curdate" )); then
        echo "! Host key was created in the future(?!). Is your clock correct?"
        echo " - Recommendation: Check clock ($(date +%F_%T)); use NTP?"
    fi

        # check for UserID expiration:
    echo "$seckey" | grep ^uid: | cut -d: -f6,7,10 | \
    while IFS=: read create expire uid ; do
        # FIXME: should we be doing any checking on the form
        # of the User ID?  Should we be unmangling it somehow?

        if [ "$create" ] && (( "$create" > "$curdate" )); then
        echo "! User ID '$uid' was created in the future(?!).  Is your clock correct?"
        echo " - Recommendation: Check clock ($(date +%F_%T)); use NTP?"
        fi
        if [ "$expire" ] ; then
        if (( "$expire" < "$curdate" )); then
            echo "! User ID '$uid' is expired."
            # FIXME: recommend a way to resolve this
        elif (( "$expire" < "$warndate" )); then
            echo "! User ID '$uid' expires in less than $warnwindow:" $(date -d "$(( $expire - $curdate )) seconds" +%F)        
            # FIXME: recommend a way to resolve this
        fi
        fi
    done
        
# FIXME: verify that the host key is properly published to the
#   keyservers (do this with the non-privileged user)

# FIXME: check that there are valid, non-expired certifying signatures
#   attached to the host key after fetching from the public keyserver
#   (do this with the non-privileged user as well)

# FIXME: propose adding a revoker to the host key if none exist (do we
#   have a way to do that after key generation?)

    # Ensure that the ssh_host_rsa_key file is present and non-empty:
    echo
    echo "Checking host SSH key..."
    if [ ! -s "${VARLIB}/ssh_host_rsa_key" ] ; then
        echo "! The host key as prepared for SSH (${VARLIB}/ssh_host_rsa_key) is missing or empty."
    else
        if [ $(stat -c '%a' "${VARLIB}/ssh_host_rsa_key") != 600 ] ; then
        echo "! Permissions seem wrong for ${VARLIB}/ssh_host_rsa_key -- should be 0600."
        fi

        # propose changes needed for sshd_config (if any)
        if ! grep -q "^HostKey[[:space:]]\+${VARLIB}/ssh_host_rsa_key$" "$sshd_config"; then
        echo "! $sshd_config does not point to the monkeysphere host key (${VARLIB}/ssh_host_rsa_key)."
        echo " - Recommendation: add a line to $sshd_config: 'HostKey ${VARLIB}/ssh_host_rsa_key'"
        fi
        if badhostkeys=$(grep -i '^HostKey' "$sshd_config" | grep -q -v "^HostKey[[:space:]]\+${VARLIB}/ssh_host_rsa_key$") ; then
        echo "! $sshd_config refers to some non-monkeysphere host keys:"
        echo "$badhostkeys"
        echo " - Recommendation: remove the above HostKey lines from $sshd_config"
        fi
    fi
    fi

# FIXME: look at the ownership/privileges of the various keyrings,
#    directories housing them, etc (what should those values be?  can
#    we make them as minimal as possible?)

# FIXME: look to see that the ownertrust rules are set properly on the
#    authentication keyring

# FIXME:  make sure that at least one identity certifier exists

    echo
    echo "Checking for MonkeySphere-enabled public-key authentication for users ..."
    # Ensure that User ID authentication is enabled:
    if ! grep -q "^AuthorizedKeysFile[[:space:]]\+${VARLIB}/authorized_keys/%u$" "$sshd_config"; then
    echo "! $sshd_config does not point to monkeysphere authorized keys."
    echo " - Recommendation: add a line to $sshd_config: 'AuthorizedKeysFile ${VARLIB}/authorized_keys/%u'"
    fi
    if badauthorizedkeys=$(grep -i '^AuthorizedKeysFile' "$sshd_config" | grep -q -v "^AuthorizedKeysFile[[:space:]]\+${VARLIB}/authorized_keys/%u$") ; then
    echo "! $sshd_config refers to non-monkeysphere authorized_keys files:"
    echo "$badauthorizedkeys"
    echo " - Recommendation: remove the above AuthorizedKeysFile lines from $sshd_config"
    fi
}

# 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 domain
    local trust
    local depth
    local keyID
    local fingerprint
    local ltsignCommand
    local trustval

    # set default values for trust depth and domain
    domain=
    trust=full
    depth=1

    # get options
    TEMP=$(getopt -o n:t:d: -l domain:,trust:,depth: -n "$PGRM" -- "$@")

    if [ $? != 0 ] ; then
    exit 1
    fi

    # Note the quotes around `$TEMP': they are essential!
    eval set -- "$TEMP"

    while true ; do
    case "$1" in
        -n|--domain)
        domain="$2"
        shift 2
        ;;
        -t|--trust)
        trust="$2"
        shift 2
        ;;
        -d|--depth)
        depth="$2"
        shift 2
        ;;
        --)
        shift
        ;;
            *)
        break
        ;;
    esac
    done

    keyID="$1"
    if [ -z "$keyID" ] ; then
    failure "You must specify the key ID of a key to add."
    fi
    export keyID

    # get the key from the key server
    gpg_authentication "--keyserver $KEYSERVER --recv-key '0x${keyID}!'"

    # get the full fingerprint of a key ID
    fingerprint=$(gpg_authentication "--list-key --with-colons --with-fingerprint 0x${keyID}!" | \
    grep '^fpr:' | grep "$keyID" | cut -d: -f10)

    if [ -z "$fingerprint" ] ; then
    failure "Key '$keyID' not found."
    fi

    echo
    echo "key found:"
    gpg_authentication "--fingerprint 0x${fingerprint}!"

    echo "Are you sure you want to add the above key as a"
    read -p "certifier of users on this system? (y/N) " OK; OK=${OK:-N}
    if [ "${OK/y/Y}" != 'Y' ] ; then
    failure "Identity certifier not added."
    fi

    # export the key to the host keyring
    gpg_authentication "--export 0x${fingerprint}!" | gpg_host --import

    if [ "$trust" == marginal ]; then
    trustval=1
    elif [ "$trust" == full ]; then
    trustval=2
    else
    failure "Trust value requested ('$trust') was unclear (only 'marginal' or 'full' are supported)."
    fi

    # ltsign command
    # NOTE: *all* user IDs will be ltsigned
    ltsignCommand=$(cat <<EOF
ltsign
y
$trustval
$depth
$domain
y
save
EOF
    )

    # ltsign the key
    if echo "$ltsignCommand" | \
    gpg_host --quiet --command-fd 0 --edit-key "0x${fingerprint}!" ; then

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

    echo
    echo "Identity certifier added."
    else
    failure "Problem adding identify certifier."
    fi
}

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

    keyID="$1"
    if [ -z "$keyID" ] ; then
    failure "You must specify the key ID of a key to remove."
    fi

    if gpg_authentication "--no-options --list-options show-uid-validity --keyring ${GNUPGHOME_AUTHENTICATION}/pubring.gpg --list-key 0x${keyID}!" ; then
    read -p "Really remove above listed identity certifier? (y/N) " OK; OK=${OK:-N}
    if [ "${OK/y/Y}" != 'Y' ] ; then
        failure "Identity certifier not removed."
    fi
    else
    failure
    fi

    # delete the requested key
    if gpg_authentication "--delete-key --batch --yes 0x${keyID}!" ; then
    # delete key from host keyring as well
    gpg_host --delete-key --batch --yes "0x${keyID}!"

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

    echo
    echo "Identity certifier removed."
    else
    failure "Problem removing identity certifier."
    fi
}

# list the host certifiers
list_certifiers() {
    local keys
    local key

    # find trusted keys in authentication keychain
    keys=$(gpg_authentication "--no-options --list-options show-uid-validity --keyring ${GNUPGHOME_AUTHENTICATION}/pubring.gpg --list-keys --with-colons --fingerprint" | \
        grep ^pub: | cut -d: -f2,5 | egrep '^(u|f):' | cut -d: -f2)

    # output keys
    for key in $keys ; do
        gpg_authentication "--no-options --list-options show-uid-validity --keyring ${GNUPGHOME_AUTHENTICATION}/pubring.gpg --list-key --fingerprint $key"
    done
}

# issue command to gpg-authentication keyring
gpg_authentication_cmd() {
    gpg_authentication "$@"
}

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

# unset variables that should be defined only in config file
unset KEYSERVER
unset AUTHORIZED_USER_IDS
unset RAW_AUTHORIZED_KEYS
unset MONKEYSPHERE_USER

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

# set empty config variable with ones from the environment, or with
# defaults
LOG_LEVEL=${MONKEYSPHERE_LOG_LEVEL:=${LOG_LEVEL:="INFO"}}
KEYSERVER=${MONKEYSPHERE_KEYSERVER:=${KEYSERVER:="subkeys.pgp.net"}}
AUTHORIZED_USER_IDS=${MONKEYSPHERE_AUTHORIZED_USER_IDS:=${AUTHORIZED_USER_IDS:="%h/.monkeysphere/authorized_user_ids"}}
RAW_AUTHORIZED_KEYS=${MONKEYSPHERE_RAW_AUTHORIZED_KEYS:=${RAW_AUTHORIZED_KEYS:="%h/.ssh/authorized_keys"}}
MONKEYSPHERE_USER=${MONKEYSPHERE_MONKEYSPHERE_USER:=${MONKEYSPHERE_USER:="monkeysphere"}}

# other variables
CHECK_KEYSERVER=${MONKEYSPHERE_CHECK_KEYSERVER:="true"}
REQUIRED_USER_KEY_CAPABILITY=${MONKEYSPHERE_REQUIRED_USER_KEY_CAPABILITY:="a"}
GNUPGHOME_HOST=${MONKEYSPHERE_GNUPGHOME_HOST:="${VARLIB}/gnupg-host"}
GNUPGHOME_AUTHENTICATION=${MONKEYSPHERE_GNUPGHOME_AUTHENTICATION:="${VARLIB}/gnupg-authentication"}

# export variables needed in su invocation
export DATE
export MODE
export MONKEYSPHERE_USER
export LOG_LEVEL
export KEYSERVER
export CHECK_KEYSERVER
export REQUIRED_USER_KEY_CAPABILITY
export GNUPGHOME_HOST
export GNUPGHOME_AUTHENTICATION
export GNUPGHOME

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

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

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

    'extend-key'|'e')
    extend_key "$@"
    ;;

    'add-hostname'|'add-name'|'n+')
    add_hostname "$@"
    ;;

    'revoke-hostname'|'revoke-name'|'n-')
    revoke_hostname "$@"
    ;;

    'show-key'|'show'|'s')
    show_server_key
    ;;

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

    'diagnostics'|'d')
    diagnostics
    ;;

    'add-identity-certifier'|'add-id-certifier'|'add-certifier'|'c+')
    add_certifier "$@"
    ;;

    'remove-identity-certifier'|'remove-id-certifier'|'remove-certifier'|'c-')
    remove_certifier "$@"
    ;;

    'list-identity-certifiers'|'list-id-certifiers'|'list-certifiers'|'list-certifier'|'c')
    list_certifiers "$@"
    ;;

    'gpg-authentication-cmd')
    gpg_authentication_cmd "$@"
    ;;

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

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

exit "$RETURN"