path: root/src/common

# -*-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_keys() {
    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
}

# 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_keys "$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"
}

# 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
}

# 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 "  $userID"
    read -p "would you like to add? [Y|n]: " OK; OK=${OK:=Y}
    if [ ${OK/y/Y} = 'Y' ] ; then
        log -n "  adding userid to authorized_user_ids file... "
        echo "$userID" >> "$AUTHORIZED_USER_IDS"
        echo "done."
    fi
    fi
}

# 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
    gpg --keyserver "$KEYSERVER" --recv-key "$keyID" || failure "could not retrieve key '$keyID'"

    # edit the key to change trust
    # FIXME: need to figure out how to automate this,
    # in a batch mode or something.
    gpg --edit-key "$keyID"
}