# -*-shell-script-*-

# Shared bash functions for the monkeysphere
#
# Written by
# Jameson Rollins <jrollins@fifthhorseman.net>
#
# Copyright 2008, released under the GPL, version 3 or later

# all caps variables are meant to be user supplied (ie. from config
# file) and are considered global

########################################################################
# managed directories
ETC="/etc/monkeysphere"
export ETC
CACHE="/var/cache/monkeysphere"
export CACHE
########################################################################

failure() {
    echo "$1" >&2
    exit ${2:-'1'}
}

# write output to stderr
log() {
    echo -n "ms: " 1>&2
    echo "$@" 1>&2
}

# cut out all comments(#) and blank lines from standard input
meat() {
    grep -v -e "^[[:space:]]*#" -e '^$'
}

# cut a specified line from standard input
cutline() {
    head --line="$1" | tail -1
}

# retrieve all keys with given user id from keyserver
# FIXME: need to figure out how to retrieve all matching keys
# (not just first 5)
gpg_fetch_userid() {
    local id
    id="$1"
    echo 1,2,3,4,5 | \
	gpg --quiet --batch --command-fd 0 --with-colons \
	--keyserver "$KEYSERVER" \
	--search ="$id" >/dev/null 2>&1
}

# check that characters are in a string (in an AND fashion).
# used for checking key capability
# check_capability capability a [b...]
check_capability() {
    local capability
    local capcheck

    capability="$1"
    shift 1

    for capcheck ; do
	if echo "$capability" | grep -q -v "$capcheck" ; then
	    return 1
	fi
    done
    return 0
}

# get the full fingerprint of a key ID
get_key_fingerprint() {
    local keyID

    keyID="$1"

    gpg --list-key --with-colons --fixed-list-mode \
	--with-fingerprint "$keyID" | grep "$keyID" | \
	grep '^fpr:' | cut -d: -f10
}


# convert escaped characters from gpg output back into original
# character
# FIXME: undo all escape character translation in with-colons gpg output
unescape() {
    echo "$1" | sed 's/\\x3a/:/'
}

# convert key from gpg to ssh known_hosts format
gpg2known_hosts() {
    local keyID
    local host

    keyID="$1"
    host=$(echo "$2" | sed -e "s|ssh://||")

    # NOTE: it seems that ssh-keygen -R removes all comment fields from
    # all lines in the known_hosts file.  why?
    # NOTE: just in case, the COMMENT can be matched with the
    # following regexp:
    # '^MonkeySphere[[:digit:]]{4}(-[[:digit:]]{2}){2}T[[:digit:]]{2}(:[[:digit:]]{2}){2}$'
    echo -n "$host "
    gpg --export "$keyID" | \
	openpgp2ssh "$keyID" | tr -d '\n'
    echo " MonkeySphere${DATE}"
}

# convert key from gpg to ssh authorized_keys format
gpg2authorized_keys() {
    local keyID
    local userID

    keyID="$1"
    userID="$2"

    gpg --export "$keyID" | \
	openpgp2ssh "$keyID" | tr -d '\n'
    echo " MonkeySphere${DATE}:${userID}"
}

# userid and key policy checking
# the following checks policy on the returned keys
# - checks that full key has appropriate valididy (u|f)
# - checks key has specified capability (REQUIRED_KEY_CAPABILITY)
# - checks that particular desired user id has appropriate validity
# see /usr/share/doc/gnupg/DETAILS.gz
# expects global variable: "MODE"
process_user_id() {
    local userID
    local cacheDir
    local requiredPubCapability
    local gpgOut
    local line
    local type
    local validity
    local keyid
    local uidfpr
    local capability
    local keyOK
    local pubKeyID
    local uidOK
    local keyIDs
    local userIDHash
    local keyID

    userID="$1"
    cacheDir="$2"

    requiredPubCapability=$(echo "$REQUIRED_KEY_CAPABILITY" | tr "[:lower:]" "[:upper:]")

    # fetch keys from keyserver, return 1 if none found
    gpg_fetch_userid "$userID" || return 1

    # output gpg info for (exact) userid and store
    gpgOut=$(gpg --fixed-list-mode --list-key --with-colons \
	="$userID" 2> /dev/null)

    # return 1 if there only "tru" lines are output from gpg
    if [ -z "$(echo "$gpgOut" | grep -v '^tru:')" ] ; then
	log "  key not found."
	return 1
    fi

    # loop over all lines in the gpg output and process.
    # need to do it this way (as opposed to "while read...") so that
    # variables set in loop will be visible outside of loop
    for line in $(seq 1 $(echo "$gpgOut" | wc -l)) ; do

	# read the contents of the line
	type=$(echo "$gpgOut" | cutline "$line" | cut -d: -f1)
	validity=$(echo "$gpgOut" | cutline "$line" | cut -d: -f2)
	keyid=$(echo "$gpgOut" | cutline "$line" | cut -d: -f5)
	uidfpr=$(echo "$gpgOut" | cutline "$line" | cut -d: -f10)
	capability=$(echo "$gpgOut" | cutline "$line" | cut -d: -f12)

	# process based on record type
	case $type in
	    'pub') # primary keys
		# new key, wipe the slate
		keyOK=
		pubKeyID=
		uidOK=
		keyIDs=

		pubKeyID="$keyid"

		# check primary key validity
		if [ "$validity" != 'u' -a "$validity" != 'f' ] ; then
		    log "  unacceptable primary key validity ($validity)."
		    continue
		fi
		# check capability is not Disabled...
		if check_capability "$capability" 'D' ; then
		    log "  key disabled."
		    continue
		fi
		# check overall key capability
		# must be Encryption and Authentication
		if ! check_capability "$capability" $requiredPubCapability ; then
		    log "  unacceptable primary key capability ($capability)."
		    continue
		fi

		# mark if primary key is acceptable
		keyOK=true

		# add primary key ID to key list if it has required capability
		if check_capability "$capability" $REQUIRED_KEY_CAPABILITY ; then
		    keyIDs[${#keyIDs[*]}]="$keyid"
		fi
		;;
	    'uid') # user ids
		# check key ok and we have key fingerprint
		if [ -z "$keyOK" ] ; then
		    continue
		fi
		# check key validity
		if [ "$validity" != 'u' -a "$validity" != 'f' ] ; then
		    continue
		fi
		# check the uid matches
		if [ "$(unescape "$uidfpr")" != "$userID" ] ; then
		    continue
		fi

		# mark if uid acceptable
		uidOK=true
		;;
	    'sub') # sub keys
		# add sub key ID to key list if it has required capability
		if check_capability "$capability" $REQUIRED_KEY_CAPABILITY ; then
		    keyIDs[${#keyIDs[*]}]="$keyid"
		fi
		;;
	esac
    done

    # hash userid for cache file name
    userIDHash=$(echo "$userID" | sha1sum | awk '{ print $1 }')

    # touch/clear key cache file
    # (will be left empty if there are noacceptable keys)
    > "$cacheDir"/"$userIDHash"."$pubKeyID"

    # for each acceptable key, write an ssh key line to the
    # key cache file
    if [ "$keyOK" -a "$uidOK" -a "${keyIDs[*]}" ] ; then
	for keyID in ${keyIDs[@]} ; do
	    log "  acceptable key/uid found."

	    if [ "$MODE" = 'known_hosts' ] ; then
		# export the key
		gpg2known_hosts "$keyID" "$userID" >> \
		    "$cacheDir"/"$userIDHash"."$pubKeyID"
		# hash the cache file if specified
		if [ "$HASH_KNOWN_HOSTS" ] ; then
		    ssh-keygen -H -f "$cacheDir"/"$userIDHash"."$pubKeyID" > /dev/null 2>&1
		    rm "$cacheDir"/"$userIDHash"."$pubKeyID".old
		fi
	    elif [ "$MODE" = 'authorized_keys' ] ; then
		# export the key
                # FIXME: needs to apply extra options for authorized_keys
	        # lines if specified
		gpg2authorized_keys "$keyID" "$userID" >> \
		    "$cacheDir"/"$userIDHash"."$pubKeyID"
	    fi
	done
    fi

    # echo the path to the key cache file
    echo "$cacheDir"/"$userIDHash"."$pubKeyID"
}

# update the cache for userid, and prompt to add file to
# authorized_user_ids file if the userid is found in gpg
# and not already in file.
update_userid() {
    local userID
    local cacheDir
    local userIDKeyCache

    userID="$1"
    cacheDir="$2"

    log "processing userid: '$userID'"
    userIDKeyCache=$(process_user_id "$userID" "$cacheDir")
    if [ -z "$userIDKeyCache" ] ; then
	return 1
    fi
    if ! grep -q "^${userID}\$" "$AUTHORIZED_USER_IDS" ; then
	echo "the following userid is not in the authorized_user_ids file:"
	echo "  $userID"
	read -p "would you like to add it? [Y|n]: " OK; OK=${OK:=Y}
	if [ ${OK/y/Y} = 'Y' ] ; then
	    log -n "adding userid to authorized_user_ids file... "
	    echo "$userID" >> "$AUTHORIZED_USER_IDS"
	    echo "done."
	else
	    log "authorized_user_ids file untouched."
	fi
    fi
}

# process a host for addition to a known_host file
process_host() {
    local host
    local cacheDir
    local hostKeyCachePath

    host="$1"
    cacheDir="$2"

    log "processing host: '$host'"

    hostKeyCachePath=$(process_user_id "ssh://${host}" "$cacheDir")
    if [ $? = 0 ] ; then
	ssh-keygen -R "$host" -f "$USER_KNOWN_HOSTS"
	cat "$hostKeyCachePath" >> "$USER_KNOWN_HOSTS"
    fi
}

# process known_hosts file
# go through line-by-line, extract each host, and process with the
# host processing function
process_known_hosts() {
    local knownHosts
    local cacheDir
    local hosts
    local host

    knownHosts="$1"
    cacheDir="$2"

    # take all the hosts from the known_hosts file (first field),
    # grep out all the hashed hosts (lines starting with '|')...
    cut -d ' ' -f 1 "$knownHosts" | \
    grep -v '^|.*$' | \
    while IFS=, read -r -a hosts ; do
	# ...and process each host
	for host in ${hosts[*]} ; do
	    process_host "$host" "$cacheDir"
	done
    done
}

# update an authorized_keys file after first processing the 
# authorized_user_ids file
update_authorized_keys() {
    local msAuthorizedKeys
    local userAuthorizedKeys
    local cacheDir

    msAuthorizedKeys="$1"
    userAuthorizedKeys="$2"
    cacheDir="$3"

    process_authorized_ids "$AUTHORIZED_USER_IDS" "$cacheDir"

    # write output key file
    log "writing monkeysphere authorized_keys file... "
    touch "$msAuthorizedKeys"
    if [ "$(ls "$cacheDir")" ] ; then
	log -n "adding gpg keys... "
	cat "$cacheDir"/* > "$msAuthorizedKeys"
	echo "done."
    else
	log "no gpg keys to add."
    fi
    if [ "$userAuthorizedKeys" -a -s "$userAuthorizedKeys" ] ; then
	log -n "adding user authorized_keys file... "
	cat "$userAuthorizedKeys" >> "$msAuthorizedKeys"
	echo "done."
    fi
    log "monkeysphere authorized_keys file generated: $msAuthorizedKeys"
}

# process an authorized_*_ids file
# go through line-by-line, extract each userid, and process
process_authorized_ids() {
    local authorizedIDs
    local cacheDir
    local userID

    authorizedIDs="$1"
    cacheDir="$2"

    # clean out keys file and remake keys directory
    rm -rf "$cacheDir"
    mkdir -p "$cacheDir"

    # loop through all user ids in file
    # FIXME: needs to handle authorized_keys options
    cat "$authorizedIDs" | meat | \
    while read -r userID ; do
	# process the userid
	log "processing userid: '$userID'"
	process_user_id "$userID" "$cacheDir" > /dev/null
    done
}

# EXPERIMENTAL (unused) process userids found in authorized_keys file
# go through line-by-line, extract monkeysphere userids from comment
# fields, and process each userid
process_userids_from_authorized_keys() {
    local authorizedKeys
    local cacheDir
    local userID

    authorizedKeys="$1"
    cacheDir="$2"

    # take all the monkeysphere userids from the authorized_keys file
    # comment field (third field) that starts with "MonkeySphere uid:"
    # FIXME: needs to handle authorized_keys options (field 0)
    cat "$authorizedKeys" | \
    while read -r options keytype key comment ; do
	# if the comment field is empty, assume the third field was
	# the comment
	if [ -z "$comment" ] ; then
	    comment="$key"
	fi
	if ! echo "$comment" | grep '^MonkeySphere userID:.*$' ; then
	    continue
	fi
	userID=$(echo "$comment" | sed -e "/^MonkeySphere userID://")
	if [ -z "$userID" ] ; then
	    continue
	fi
	# process the userid
	log "processing userid: '$userID'"
	process_user_id "$userID" "$cacheDir" > /dev/null
    done
}

# retrieve key from web of trust, and set owner trust to "full"
# if key is found.
trust_key() {
    # get the key from the key server
    if ! gpg --keyserver "$KEYSERVER" --recv-key "$keyID" ; then
	log "could not retrieve key '$keyID'"
	return 1
    fi

    # get key fingerprint
    fingerprint=$(get_key_fingerprint "$keyID")

    # import "full" trust for fingerprint into gpg
    echo ${fingerprint}:5: | gpg --import-ownertrust
    if [ $? = 0 ] ; then
	log "owner trust updated."
    else
	failure "there was a problem changing owner trust."
    fi	
}

# 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 --send-keys --keyserver "$KEYSERVER" $(hostname -f)
    echo "NOT PUBLISHED: gpg --send-keys --keyserver $KEYSERVER $(hostname -f)"
}