path: root/src/share/common

# -*-shell-script-*-
# This should be sourced by bash (though we welcome changes to make it POSIX sh compliant)

# Shared sh functions for the monkeysphere
#
# Written by
# Jameson Rollins <jrollins@finestructure.net>
# Jamie McClelland <jm@mayfirst.org>
# Daniel Kahn Gillmor <dkg@fifthhorseman.net>
#
# Copyright 2008-2009, 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

########################################################################
### UTILITY FUNCTIONS

# output version info
version() {
    cat "${SYSSHAREDIR}/VERSION"
}

# failure function.  exits with code 255, unless specified otherwise.
failure() {
    [ "$1" ] && echo "$1" >&2
    exit ${2:-'255'}
}

# write output to stderr based on specified LOG_LEVEL the first
# parameter is the priority of the output, and everything else is what
# is echoed to stderr.  If there is nothing else, then output comes
# from stdin, and is not prefaced by log prefix.
log() {
    local priority
    local level
    local output
    local alllevels
    local found=

    # don't include SILENT in alllevels: it's handled separately
    # list in decreasing verbosity (all caps).
    # separate with $IFS explicitly, since we do some fancy footwork
    # elsewhere.
    alllevels="DEBUG${IFS}VERBOSE${IFS}INFO${IFS}ERROR"

    # translate lowers to uppers in global log level
    LOG_LEVEL=$(echo "$LOG_LEVEL" | tr "[:lower:]" "[:upper:]")

    # just go ahead and return if the log level is silent
    if [ "$LOG_LEVEL" = 'SILENT' ] ; then
    return
    fi

    for level in $alllevels ; do 
    if [ "$LOG_LEVEL" = "$level" ] ; then
        found=true
    fi
    done
    if [ -z "$found" ] ; then
    # default to INFO:
    LOG_LEVEL=INFO
    fi

    # get priority from first parameter, translating all lower to
    # uppers
    priority=$(echo "$1" | tr "[:lower:]" "[:upper:]")
    shift

    # scan over available levels
    for level in $alllevels ; do
    # output if the log level matches, set output to true
    # this will output for all subsequent loops as well.
    if [ "$LOG_LEVEL" = "$level" ] ; then
        output=true
    fi
    if [ "$priority" = "$level" -a "$output" = 'true' ] ; then
        if [ "$1" ] ; then
        echo "$@"
        else
        cat
        fi | sed 's/^/'"${LOG_PREFIX}"'/' >&2
    fi
    done
}

# run command as monkeysphere user
su_monkeysphere_user() {
    # our main goal here is to run the given command as the the
    # monkeysphere user, but without prompting for any sort of
    # authentication.  If this is not possible, we should just fail.

    # FIXME: our current implementation is overly restrictive, because
    # there may be some su PAM configurations that would allow su
    # "$MONKEYSPHERE_USER" -c "$@" to Just Work without prompting,
    # allowing specific users to invoke commands which make use of
    # this user.

    # chpst (from runit) would be nice to use, but we don't want to
    # introduce an extra dependency just for this.  This may be a
    # candidate for re-factoring if we switch implementation languages.

    case $(id -un) in
    # if monkeysphere user, run the command under bash
    "$MONKEYSPHERE_USER")
        bash -c "$@"
        ;;

         # if root, su command as monkeysphere user
    'root')
        su "$MONKEYSPHERE_USER" -c "$@"
        ;;

    # otherwise, fail
    *)
        log error "non-privileged user."
        ;;
    esac
}

# cut out all comments(#) and blank lines from standard input
meat() {
    grep -v -e "^[[:space:]]*#" -e '^$' "$1"
}

# cut a specified line from standard input
cutline() {
    head --line="$1" "$2" | tail -1
}

# make a temporary directory
msmktempdir() {
    mktemp -d ${TMPDIR:-/tmp}/monkeysphere.XXXXXXXXXX
}

# make a temporary file
msmktempfile() {
    mktemp ${TMPDIR:-/tmp}/monkeysphere.XXXXXXXXXX
}

# this is a wrapper for doing lock functions.
#
# it lets us depend on either lockfile-progs (preferred) or procmail's
# lockfile, and should
lock() {
    local use_lockfileprogs=true
    local action="$1"
    local file="$2"

    if ! ( type lockfile-create &>/dev/null ) ; then
    if ! ( type lockfile &>/dev/null ); then
        failure "Neither lockfile-create nor lockfile are in the path!"
    fi
    use_lockfileprogs=
    fi
    
    case "$action" in
    create)
        if [ -n "$use_lockfileprogs" ] ; then
        lockfile-create "$file" || failure "unable to lock '$file'"
        else
        lockfile -r 20 "${file}.lock" || failure "unable to lock '$file'"
        fi
        log debug "lock created on '$file'."
        ;;
    touch)  
        if [ -n "$use_lockfileprogs" ] ; then
        lockfile-touch --oneshot "$file"
        else
        : Nothing to do here
        fi
        log debug "lock touched on '$file'."
        ;;
    remove)
        if [ -n "$use_lockfileprogs" ] ; then
        lockfile-remove "$file"
        else
        rm -f "${file}.lock"
        fi
        log debug "lock removed on '$file'."
        ;;
    *)
        failure "bad argument for lock subfunction '$action'"
    esac
}


# for portability, between gnu date and BSD date.
# arguments should be:  number longunits format

# e.g. advance_date 20 seconds +%F
advance_date() {
    local gnutry
    local number="$1"
    local longunits="$2"
    local format="$3"
    local shortunits

    # try things the GNU way first 
    if date -d "$number $longunits" "$format" &>/dev/null; then
    date -d "$number $longunits" "$format"
    else
    # otherwise, convert to (a limited version of) BSD date syntax:
    case "$longunits" in
        years)
        shortunits=y
        ;;
        months)
        shortunits=m
        ;;
        weeks)
        shortunits=w
        ;;
        days)
        shortunits=d
        ;;
        hours)
        shortunits=H
        ;;
        minutes)
        shortunits=M
        ;;
        seconds)
        shortunits=S
        ;;
        *)
        # this is a longshot, and will likely fail; oh well.
        shortunits="$longunits"
    esac
    date "-v+${number}${shortunits}" "$format"
    fi
}


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

    usage="$1"
    shift 1

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

# hash of a file
file_hash() {
    if type md5sum &>/dev/null ; then
    md5sum "$1"
    elif type md5 &>/dev/null ; then
    md5 "$1"
    else
    failure "Neither md5sum nor md5 are in the path!"
    fi
}

# convert escaped characters in pipeline from gpg output back into
# original character
# FIXME: undo all escape character translation in with-colons gpg
# output
gpg_unescape() {
    sed 's/\\x3a/:/g'
}

# convert nasty chars into gpg-friendly form in pipeline
# FIXME: escape everything, not just colons!
gpg_escape() {
    sed 's/:/\\x3a/g'
}

# prompt for GPG-formatted expiration, and emit result on stdout
get_gpg_expiration() {
    local keyExpire

    keyExpire="$1"

    if [ -z "$keyExpire" -a "$PROMPT" = 'true' ]; then
    cat >&2 <<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
    while [ -z "$keyExpire" ] ; do
        printf "Key is valid for? (0) " >&2
        read keyExpire
        if ! test_gpg_expire ${keyExpire:=0} ; then
        echo "invalid value" >&2
        unset keyExpire
        fi
    done
    elif ! test_gpg_expire "$keyExpire" ; then
    failure "invalid key expiration value '$keyExpire'."
    fi
    
    echo "$keyExpire"
}

passphrase_prompt() {
    local prompt="$1"
    local fifo="$2"
    local PASS

    if [ "$DISPLAY" ] && type "${SSH_ASKPASS:-ssh-askpass}" >/dev/null; then
    printf 'Launching "%s"\n' "${SSH_ASKPASS:-ssh-askpass}" | log info
    printf '(with prompt "%s")\n' "$prompt" | log debug
    "${SSH_ASKPASS:-ssh-askpass}" "$prompt" > "$fifo"
    else
    read -s -p "$prompt" PASS
    # Uses the builtin echo, so should not put the passphrase into
    # the process table.  I think. --dkg
    echo "$PASS" > "$fifo"
    fi
}

# remove all lines with specified string from specified file
remove_line() {
    local file
    local string
    local tempfile

    file="$1"
    string="$2"

    if [ -z "$file" -o -z "$string" ] ; then
    return 1
    fi

    if [ ! -e "$file" ] ; then
    return 1
    fi

    # if the string is in the file...
    if grep -q -F "$string" "$file" 2>/dev/null ; then
    tempfile=$(mktemp "${file}.XXXXXXX") || \
        failure "Unable to make temp file '${file}.XXXXXXX'"
    
    # remove the line with the string, and return 0
    grep -v -F "$string" "$file" >"$tempfile"
    cat "$tempfile" > "$file"
    rm "$tempfile"
    return 0
    # otherwise return 1
    else
    return 1
    fi
}

# remove all lines with MonkeySphere strings in file
remove_monkeysphere_lines() {
    local file
    local tempfile

    file="$1"

    # return error if file does not exist
    if [ ! -e "$file" ] ; then
    return 1
    fi

    # just return ok if the file is empty, since there aren't any
    # lines to remove
    if [ ! -s "$file" ] ; then
    return 0
    fi

    tempfile=$(mktemp "${file}.XXXXXXX") || \
    failure "Could not make temporary file '${file}.XXXXXXX'."

    egrep -v '^MonkeySphere[[:digit:]]{4}(-[[:digit:]]{2}){2}T[[:digit:]]{2}(:[[:digit:]]{2}){2}$' \
    "$file" >"$tempfile"
    cat "$tempfile" > "$file"
    rm "$tempfile"
}

# translate ssh-style path variables %h and %u
translate_ssh_variables() {
    local uname
    local home

    uname="$1"
    path="$2"

    # get the user's home directory
    userHome=$(get_homedir "$uname")

    # translate '%u' to user name
    path=${path/\%u/"$uname"}
    # translate '%h' to user home directory
    path=${path/\%h/"$userHome"}

    echo "$path"
}

# test that a string to conforms to GPG's expiration format
test_gpg_expire() {
    echo "$1" | egrep -q "^[0-9]+[mwy]?$"
}

# check that a file is properly owned, and that all it's parent
# directories are not group/other writable
check_key_file_permissions() {
    local uname
    local path
    local stat
    local access
    local gAccess
    local oAccess

    # function to check that the given permission corresponds to writability
    is_write() {
    [ "$1" = "w" ]
    }

    uname="$1"
    path="$2"

    if [ "$STRICT_MODES" = 'false' ] ; then
    log debug "skipping path permission check for '$path' because STRICT_MODES is false..."
    return 0
    fi
    log debug "checking path permission '$path'..."

    # rewrite path if it points to a symlink
    if [ -h "$path" ] ; then
    path=$(readlink -f "$path")
    log debug "checking path symlink '$path'..."
    fi

    # return 255 if cannot stat file
    if ! stat=$(ls -ld "$path" 2>/dev/null) ; then
        log error "could not stat path '$path'."
    return 255
    fi

    owner=$(echo "$stat" | awk '{ print $3 }')
    gAccess=$(echo "$stat" | cut -c6)
    oAccess=$(echo "$stat" | cut -c9)

    # return 1 if path has invalid owner
    if [ "$owner" != "$uname" -a "$owner" != 'root' ] ; then
    log error "improper ownership on path '$path':"
    log error " $owner != ($uname|root)"
    return 1
    fi

    # return 2 if path has group or other writability
    if is_write "$gAccess" || is_write "$oAccess" ; then
    log error "improper group or other writability on path '$path':"
    log error " group: $gAccess, other: $oAccess"
    return 2
    fi

    # return zero if all clear, or go to next path
    if [ "$path" = '/' ] ; then
    log debug "path ok."
    return 0
    else
    check_key_file_permissions "$uname" $(dirname "$path")
    fi
}

# return a list of all users on the system
list_users() {
    if type getent &>/dev/null ; then
    # for linux and FreeBSD systems
    getent passwd | cut -d: -f1
    elif type dscl &>/dev/null ; then
    # for Darwin systems
    dscl localhost -list /Search/Users
    else
    failure "Neither getent or dscl is in the path!  Could not determine list of users."
    fi
}

# return the path to the home directory of a user
get_homedir() {
    local uname=${1:-`whoami`}
    eval "echo ~${uname}"
}

# return the primary group of a user
get_primary_group() {
    local uname=${1:-`whoami`}
    groups "$uname" | sed 's/^..* : //' | awk '{ print $1 }'
}

### CONVERSION UTILITIES

# output the ssh key for a given key ID
gpg2ssh() {
    local keyID
    
    keyID="$1"

    gpg --export "$keyID" | openpgp2ssh "$keyID" 2>/dev/null
}

# output known_hosts line from ssh key
ssh2known_hosts() {
    local host
    local port
    local key

    # FIXME this does not properly deal with IPv6 hosts using the
    # standard port (because it's unclear whether their final
    # colon-delimited address section is a port number or an address
    # string)
    host=${1%:*}
    port=${1##*:}
    key="$2"

    # specify the host and port properly for new ssh known_hosts
    # format
    if [ "$port" != "$host" ] ; then
    host="[${host}]:${port}"
    fi
    printf "%s %s MonkeySphere%s\n" "$host" "$key" "$DATE"
}

# output authorized_keys line from ssh key
ssh2authorized_keys() {
    local userID
    local key
    
    userID="$1"
    key="$2"

    printf "%s MonkeySphere%s %s\n" "$key" "$DATE" "$userID"
}

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

    host="$1"
    keyID="$2"

    key=$(gpg2ssh "$keyID")

    # 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}$'
    printf "%s %s MonkeySphere%s\n" "$host" "$key" "$DATE"
}

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

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

    key=$(gpg2ssh "$keyID")

    # 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}$'
    printf "%s MonkeySphere%s %s\n" "$key" "$DATE" "$userID"
}

### GPG UTILITIES

# retrieve all keys with given user id from keyserver
# FIXME: need to figure out how to retrieve all matching keys
# (not just first N (5 in this case))
gpg_fetch_userid() {
    local returnCode=0
    local userID

    if [ "$CHECK_KEYSERVER" != 'true' ] ; then
    return 0
    fi

    userID="$1"

    log verbose " checking keyserver $KEYSERVER... "
    echo 1,2,3,4,5 | \
    gpg --quiet --batch --with-colons \
    --command-fd 0 --keyserver "$KEYSERVER" \
    --search ="$userID" &>/dev/null
    returnCode="$?"

    return "$returnCode"
}

########################################################################
### PROCESSING FUNCTIONS

# 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 requested user ID has appropriate validity
# (see /usr/share/doc/gnupg/DETAILS.gz)
# output is one line for every found key, in the following format:
#
# flag:sshKey
#
# "flag" is an acceptability flag, 0 = ok, 1 = bad
# "sshKey" is the translated gpg key
#
# all log output must go to stderr, as stdout is used to pass the
# flag:sshKey to the calling function.
#
# expects global variable: "MODE"
process_user_id() {
    local returnCode=0
    local userID
    local requiredCapability
    local requiredPubCapability
    local gpgOut
    local type
    local validity
    local keyid
    local uidfpr
    local usage
    local keyOK
    local uidOK
    local lastKey
    local lastKeyOK
    local fingerprint

    userID="$1"

    # set the required key capability based on the mode
    if [ "$MODE" = 'known_hosts' ] ; then
    requiredCapability="$REQUIRED_HOST_KEY_CAPABILITY"
    elif [ "$MODE" = 'authorized_keys' ] ; then
    requiredCapability="$REQUIRED_USER_KEY_CAPABILITY"  
    fi
    requiredPubCapability=$(echo "$requiredCapability" | tr "[:lower:]" "[:upper:]")

    # fetch the user ID if necessary/requested
    gpg_fetch_userid "$userID"

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

    # if the gpg query return code is not 0, return 1
    if [ "$returnCode" -ne 0 ] ; then
        log verbose " no primary keys found."
        return 1
    fi

    # loop over all lines in the gpg output and process.
    echo "$gpgOut" | cut -d: -f1,2,5,10,12 | \
    while IFS=: read -r type validity keyid uidfpr usage ; do
    # process based on record type
    case $type in
        'pub') # primary keys
        # new key, wipe the slate
        keyOK=
        uidOK=
        lastKey=pub
        lastKeyOK=
        fingerprint=

        log verbose " primary key found: $keyid"

        # if overall key is not valid, skip
        if [ "$validity" != 'u' -a "$validity" != 'f' ] ; then
            log debug "  - unacceptable primary key validity ($validity)."
            continue
        fi
        # if overall key is disabled, skip
        if check_capability "$usage" 'D' ; then
            log debug "  - key disabled."
            continue
        fi
        # if overall key capability is not ok, skip
        if ! check_capability "$usage" $requiredPubCapability ; then
            log debug "  - unacceptable primary key capability ($usage)."
            continue
        fi

        # mark overall key as ok
        keyOK=true

        # mark primary key as ok if capability is ok
        if check_capability "$usage" $requiredCapability ; then
            lastKeyOK=true
        fi
        ;;
        'uid') # user ids
        if [ "$lastKey" != pub ] ; then
            log verbose " ! got a user ID after a sub key?!  user IDs should only follow primary keys!"
            continue
        fi
        # if an acceptable user ID was already found, skip
        if [ "$uidOK" = 'true' ] ; then
            continue
        fi
        # if the user ID does matches...
        if [ "$(echo "$uidfpr" | gpg_unescape)" = "$userID" ] ; then
            # and the user ID validity is ok
            if [ "$validity" = 'u' -o "$validity" = 'f' ] ; then
            # mark user ID acceptable
            uidOK=true
            else
            log debug "  - unacceptable user ID validity ($validity)."
            fi
        else
            continue
        fi

        # output a line for the primary key
        # 0 = ok, 1 = bad
        if [ "$keyOK" -a "$uidOK" -a "$lastKeyOK" ] ; then
            log verbose "  * acceptable primary key."
            if [ -z "$sshKey" ] ; then
            log error "    ! primary key could not be translated (not RSA?)."
            else
            echo "0:${sshKey}"
            fi
        else
            log debug "  - unacceptable primary key."
            if [ -z "$sshKey" ] ; then
            log debug "    ! primary key could not be translated (not RSA?)."
            else
            echo "1:${sshKey}"
            fi
        fi
        ;;
        'sub') # sub keys
        # unset acceptability of last key
        lastKey=sub
        lastKeyOK=
        fingerprint=
        
        # don't bother with sub keys if the primary key is not valid
        if [ "$keyOK" != true ] ; then
            continue
        fi

        # don't bother with sub keys if no user ID is acceptable:
        if [ "$uidOK" != true ] ; then
            continue
        fi
        
        # if sub key validity is not ok, skip
        if [ "$validity" != 'u' -a "$validity" != 'f' ] ; then
            log debug "  - unacceptable sub key validity ($validity)."
            continue
        fi
        # if sub key capability is not ok, skip
        if ! check_capability "$usage" $requiredCapability ; then
            log debug "  - unacceptable sub key capability ($usage)."
            continue
        fi

        # mark sub key as ok
        lastKeyOK=true
        ;;
        'fpr') # key fingerprint
        fingerprint="$uidfpr"

        sshKey=$(gpg2ssh "$fingerprint")

        # if the last key was the pub key, skip
        if [ "$lastKey" = pub ] ; then
            continue
        fi

        # output a line for the sub key
        # 0 = ok, 1 = bad
        if [ "$keyOK" -a "$uidOK" -a "$lastKeyOK" ] ; then
            log verbose "  * acceptable sub key."
            if [ -z "$sshKey" ] ; then
            log error "    ! sub key could not be translated (not RSA?)."
            else
            echo "0:${sshKey}"
            fi
        else
            log debug "  - unacceptable sub key."
            if [ -z "$sshKey" ] ; then
            log debug "    ! sub key could not be translated (not RSA?)."
            else
            echo "1:${sshKey}"
            fi
        fi
        ;;
    esac
    done | sort -t: -k1 -n -r
    # NOTE: this last sort is important so that the "good" keys (key
    # flag '0') come last.  This is so that they take precedence when
    # being processed in the key files over "bad" keys (key flag '1')
}

# process a single host in the known_host file
process_host_known_hosts() {
    local host
    local userID
    local noKey=
    local nKeys
    local nKeysOK
    local ok
    local sshKey
    local tmpfile

    # set the key processing mode
    export MODE='known_hosts'

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

    log verbose "processing: $host"

    nKeys=0
    nKeysOK=0

    IFS=$'\n'
    for line in $(process_user_id "${userID}") ; do
    # note that key was found
    nKeys=$((nKeys+1))

    ok=$(echo "$line" | cut -d: -f1)
    sshKey=$(echo "$line" | cut -d: -f2)

        if [ -z "$sshKey" ] ; then
            continue
        fi

    # remove any old host key line, and note if removed nothing is
    # removed
    remove_line "$KNOWN_HOSTS" "$sshKey" || noKey=true

    # if key OK, add new host line
    if [ "$ok" -eq '0' ] ; then
        # note that key was found ok
        nKeysOK=$((nKeysOK+1))

        # hash if specified
        if [ "$HASH_KNOWN_HOSTS" = 'true' ] ; then
        # FIXME: this is really hackish cause ssh-keygen won't
        # hash from stdin to stdout
        tmpfile=$(mktemp ${TMPDIR:-/tmp}/tmp.XXXXXXXXXX)
        ssh2known_hosts "$host" "$sshKey" > "$tmpfile"
        ssh-keygen -H -f "$tmpfile" 2>/dev/null
        cat "$tmpfile" >> "$KNOWN_HOSTS"
        rm -f "$tmpfile" "${tmpfile}.old"
        else
        ssh2known_hosts "$host" "$sshKey" >> "$KNOWN_HOSTS"
        fi

        # log if this is a new key to the known_hosts file
        if [ "$noKey" ] ; then
        log info "* new key for $host added to known_hosts file."
        fi
    fi
    done

    # if at least one key was found...
    if [ "$nKeys" -gt 0 ] ; then
    # if ok keys were found, return 0
    if [ "$nKeysOK" -gt 0 ] ; then
        return 0
    # else return 2
    else
        return 2
    fi
    # if no keys were found, return 1
    else
    return 1
    fi
}

# update the known_hosts file for a set of hosts listed on command
# line
update_known_hosts() {
    local returnCode=0
    local nHosts
    local nHostsOK
    local nHostsBAD
    local fileCheck
    local host
    local newUmask

    # the number of hosts specified on command line
    nHosts="$#"

    nHostsOK=0
    nHostsBAD=0

    # touch the known_hosts file so that the file permission check
    # below won't fail upon not finding the file
    if [ ! -f "$KNOWN_HOSTS" ]; then
    # make sure to create any files or directories with the appropriate write bits turned off:
    newUmask=$(printf "%04o" $(( 0$(umask) | 0022 )) )
    [ -d $(dirname "$KNOWN_HOSTS") ] \
        || (umask "$newUmask" && mkdir -p -m 0700 $(dirname "$KNOWN_HOSTS") ) \
        || failure "Could not create path to known_hosts file '$KNOWN_HOSTS'"
    # make sure to create this file with the appropriate bits turned off:
    (umask "$newUmask" && touch "$KNOWN_HOSTS") \
        || failure "Unable to create known_hosts file '$KNOWN_HOSTS'"
    fi

    # check permissions on the known_hosts file path
    check_key_file_permissions $(whoami) "$KNOWN_HOSTS" \
    || failure "Bad permissions governing known_hosts file '$KNOWN_HOSTS'"

    # create a lockfile on known_hosts:
    lock create "$KNOWN_HOSTS"
    # FIXME: we're discarding any pre-existing EXIT trap; is this bad?
    trap "lock remove $KNOWN_HOSTS" EXIT

    # note pre update file checksum
    fileCheck=$(file_hash "$KNOWN_HOSTS")

    for host ; do
    # process the host
    process_host_known_hosts "$host" || returnCode="$?"
    # note the result
    case "$returnCode" in
        0)
        nHostsOK=$((nHostsOK+1))
        ;;
        2)
        nHostsBAD=$((nHostsBAD+1))
        ;;
    esac

    # touch the lockfile, for good measure.
    lock touch "$KNOWN_HOSTS"
    done

    # remove the lockfile and the trap
    lock remove "$KNOWN_HOSTS"
    trap - EXIT

    # note if the known_hosts file was updated
    if [ "$(file_hash "$KNOWN_HOSTS")" != "$fileCheck" ] ; then
    log debug "known_hosts file updated."
    fi

    # if an acceptable host was found, return 0
    if [ "$nHostsOK" -gt 0 ] ; then
    return 0
    # else if no ok hosts were found...
    else
    # if no bad host were found then no hosts were found at all,
    # and return 1
    if [ "$nHostsBAD" -eq 0 ] ; then
        return 1
    # else if at least one bad host was found, return 2
    else
        return 2
    fi
    fi
}

# process hosts from a known_hosts file
process_known_hosts() {
    local hosts

    # exit if the known_hosts file does not exist
    if [ ! -e "$KNOWN_HOSTS" ] ; then
    failure "known_hosts file '$KNOWN_HOSTS' does not exist."
    fi

    log debug "processing known_hosts file:"
    log debug " $KNOWN_HOSTS"

    hosts=$(meat "$KNOWN_HOSTS" | cut -d ' ' -f 1 | grep -v '^|.*$' | tr , ' ' | tr '\n' ' ')

    if [ -z "$hosts" ] ; then
    log debug "no hosts to process."
    return
    fi

    # take all the hosts from the known_hosts file (first
    # field), grep out all the hashed hosts (lines starting
    # with '|')...
    update_known_hosts $hosts
}

# process uids for the authorized_keys file
process_uid_authorized_keys() {
    local userID
    local nKeys
    local nKeysOK
    local ok
    local sshKey

    # set the key processing mode
    export MODE='authorized_keys'

    userID="$1"

    log verbose "processing: $userID"

    nKeys=0
    nKeysOK=0

    IFS=$'\n'
    for line in $(process_user_id "$userID") ; do
    # note that key was found
    nKeys=$((nKeys+1))

    ok=$(echo "$line" | cut -d: -f1)
    sshKey=$(echo "$line" | cut -d: -f2)

        if [ -z "$sshKey" ] ; then
            continue
        fi

    # remove the old host key line
    remove_line "$AUTHORIZED_KEYS" "$sshKey"

    # if key OK, add new host line
    if [ "$ok" -eq '0' ] ; then
        # note that key was found ok
        nKeysOK=$((nKeysOK+1))

        ssh2authorized_keys "$userID" "$sshKey" >> "$AUTHORIZED_KEYS"
    fi
    done

    # if at least one key was found...
    if [ "$nKeys" -gt 0 ] ; then
    # if ok keys were found, return 0
    if [ "$nKeysOK" -gt 0 ] ; then
        return 0
    # else return 2
    else
        return 2
    fi
    # if no keys were found, return 1
    else
    return 1
    fi
}

# update the authorized_keys files from a list of user IDs on command
# line
update_authorized_keys() {
    local returnCode=0
    local userID
    local nIDs
    local nIDsOK
    local nIDsBAD
    local fileCheck

    # the number of ids specified on command line
    nIDs="$#"

    nIDsOK=0
    nIDsBAD=0

    log debug "updating authorized_keys file:"
    log debug " $AUTHORIZED_KEYS"

    # check permissions on the authorized_keys file path
    check_key_file_permissions $(whoami) "$AUTHORIZED_KEYS" || failure

    # create a lockfile on authorized_keys
    lock create "$AUTHORIZED_KEYS"
    # FIXME: we're discarding any pre-existing EXIT trap; is this bad?
    trap "lock remove $AUTHORIZED_KEYS" EXIT

    # note pre update file checksum
    fileCheck="$(file_hash "$AUTHORIZED_KEYS")"

    # remove any monkeysphere lines from authorized_keys file
    remove_monkeysphere_lines "$AUTHORIZED_KEYS"

    for userID ; do
    # process the user ID, change return code if key not found for
    # user ID
    process_uid_authorized_keys "$userID" || returnCode="$?"

    # note the result
    case "$returnCode" in
        0)
        nIDsOK=$((nIDsOK+1))
        ;;
        2)
        nIDsBAD=$((nIDsBAD+1))
        ;;
    esac

    # touch the lockfile, for good measure.
    lock touch "$AUTHORIZED_KEYS"
    done

    # remove the lockfile and the trap
    lock remove "$AUTHORIZED_KEYS"

    # remove the trap
    trap - EXIT

    # note if the authorized_keys file was updated
    if [ "$(file_hash "$AUTHORIZED_KEYS")" != "$fileCheck" ] ; then
    log debug "authorized_keys file updated."
    fi

    # if an acceptable id was found, return 0
    if [ "$nIDsOK" -gt 0 ] ; then
    return 0
    # else if no ok ids were found...
    else
    # if no bad ids were found then no ids were found at all, and
    # return 1
    if [ "$nIDsBAD" -eq 0 ] ; then
        return 1
    # else if at least one bad id was found, return 2
    else
        return 2
    fi
    fi
}

# process an authorized_user_ids file for authorized_keys
process_authorized_user_ids() {
    local line
    local nline
    local userIDs

    authorizedUserIDs="$1"

    # exit if the authorized_user_ids file is empty
    if [ ! -e "$authorizedUserIDs" ] ; then
    failure "authorized_user_ids file '$authorizedUserIDs' does not exist."
    fi

    log debug "processing authorized_user_ids file:"
    log debug " $authorizedUserIDs"

    # check permissions on the authorized_user_ids file path
    check_key_file_permissions $(whoami) "$authorizedUserIDs" || failure

    if ! meat "$authorizedUserIDs" >/dev/null ; then
    log debug " no user IDs to process."
    return
    fi

    nline=0

    # extract user IDs from authorized_user_ids file
    IFS=$'\n'
    for line in $(meat "$authorizedUserIDs") ; do
    userIDs["$nline"]="$line"
    nline=$((nline+1))
    done

    update_authorized_keys "${userIDs[@]}"
}

# takes a gpg key or keys on stdin, and outputs a list of
# fingerprints, one per line:
list_primary_fingerprints() {
    local fake=$(msmktempdir)
    GNUPGHOME="$fake" gpg --no-tty --quiet --import
    GNUPGHOME="$fake" gpg --with-colons --fingerprint --list-keys | \
    awk -F: '/^fpr:/{ print $10 }'
    rm -rf "$fake"
}


check_cruft_file() {
    local loc="$1"
    local version="$2"
    
    if [ -e "$loc" ] ; then
    printf "! The file '%s' is no longer used by\n  monkeysphere (as of version %s), and can be removed.\n\n" "$loc" "$version" | log info
    fi
}

check_upgrade_dir() {
    local loc="$1"
    local version="$2"

    if [ -d "$loc" ] ; then
    printf "The presence of directory '%s' indicates that you have\nnot yet completed a monkeysphere upgrade.\nYou should probably run the following script:\n  %s/transitions/%s\n\n" "$loc" "$SYSSHAREDIR" "$version" | log info
    fi
}

## look for cruft from old versions of the monkeysphere, and notice if
## upgrades have not been run:
report_cruft() {
    check_upgrade_dir "${SYSCONFIGDIR}/gnupg-host" 0.23
    check_upgrade_dir "${SYSCONFIGDIR}/gnupg-authentication" 0.23

    check_cruft_file "${SYSCONFIGDIR}/gnupg-authentication.conf" 0.23
    check_cruft_file "${SYSCONFIGDIR}/gnupg-host.conf" 0.23

    local found=
    for foo in "${SYSDATADIR}/backup-from-"*"-transition"  ; do
    if [ -d "$foo" ] ; then
        printf "! %s\n" "$foo" | log info
        found=true
    fi
    done
    if [ "$found" ] ; then
    printf "The directories above are backups left over from a monkeysphere transition.\nThey may contain copies of sensitive data (host keys, certifier lists), but\nthey are no longer needed by monkeysphere.\nYou may remove them at any time.\n\n" | log info
    fi
}