path: root/src/common

# -*-shell-script-*-

# Shared sh 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

########################################################################
### COMMON VARIABLES

# managed directories
ETC="/etc/monkeysphere"
export ETC

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

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

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

loge() {
    echo "$@" >&2
}

# 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
}

# 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() {
    md5sum "$1" 2> /dev/null
}

# 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/:/g'
}

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

    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
    # remove the line with the string, and return 0
    grep -v -F "$string" "$file" | sponge "$file"
    return 0
    # otherwise return 1
    else
    return 1
    fi
}

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

    file="$1"

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

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

    egrep -v '^MonkeySphere[[:digit:]]{4}(-[[:digit:]]{2}){2}T[[:digit:]]{2}(:[[:digit:]]{2}){2}$' \
    "$file" | sponge "$file"
}

# 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=$(getent passwd "$uname" | cut -d: -f6)

    # 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 user
    local path
    local access
    local gAccess
    local oAccess

    # function to check that an octal corresponds to writability
    is_write() {
    [ "$1" -eq 2 -o "$1" -eq 3 -o "$1" -eq 6 -o "$1" -eq 7 ]
    }

    user="$1"
    path="$2"

    # return 0 is path does not exist
    [ -e "$path" ] || return 0

    owner=$(stat --format '%U' "$path")
    access=$(stat --format '%a' "$path")
    gAccess=$(echo "$access" | cut -c2)
    oAccess=$(echo "$access" | cut -c3)

    # check owner
    if [ "$owner" != "$user" -a "$owner" != 'root' ] ; then
    return 1
    fi

    # check group/other writability
    if is_write "$gAccess" || is_write "$oAccess" ; then
    return 2
    fi

    if [ "$path" = '/' ] ; then
    return 0
    else
    check_key_file_permissions $(dirname "$path")
    fi
}

### 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 key

    host="$1"
    key="$2"

    echo -n "$host "
    echo -n "$key" | tr -d '\n'
    echo " MonkeySphere${DATE}"
}

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

    echo -n "$key" | tr -d '\n'
    echo " MonkeySphere${DATE} ${userID}"
}

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

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

    # 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 "
    gpg2ssh "$keyID" | tr -d '\n'
    echo " MonkeySphere${DATE}"
}

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

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

    # 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}$'
    gpg2ssh "$keyID" | tr -d '\n'
    echo " MonkeySphere${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 userID
    local returnCode

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

    userID="$1"

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

    # if the user is the monkeysphere user, then update the
    # monkeysphere user's trustdb
    if [ $(id -un) = "$MONKEYSPHERE_USER" ] ; then
    gpg_authentication "--check-trustdb" > /dev/null 2>&1
    fi

    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:fingerprint
#
# "flag" is an acceptability flag, 0 = ok, 1 = bad
# "fingerprint" is the fingerprint of the key
#
# expects global variable: "MODE"
process_user_id() {
    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)

    # if the gpg query return code is not 0, return 1
    if [ "$?" -ne 0 ] ; then
        log " 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 " primary key found: $keyid"

        # if overall key is not valid, skip
        if [ "$validity" != 'u' -a "$validity" != 'f' ] ; then
            log "  - unacceptable primary key validity ($validity)."
            continue
        fi
        # if overall key is disabled, skip
        if check_capability "$usage" 'D' ; then
            log "  - key disabled."
            continue
        fi
        # if overall key capability is not ok, skip
        if ! check_capability "$usage" $requiredPubCapability ; then
            log "  - unacceptable primary key capability ($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 " - got a user ID after a sub key!  user IDs should only follow primary keys!"
            continue
        fi
        # don't bother with a uid if there is no valid or reasonable primary key.
        if [ "$keyOK" != true ] ; then
            continue
        fi
        # if an acceptable user ID was already found, skip
        if [ "$uidOK" ] ; then
            continue
        fi
        # if the user ID does not match, skip
        if [ "$(unescape "$uidfpr")" != "$userID" ] ; then
            continue
        fi
        # if the user ID validity is not ok, skip
        if [ "$validity" != 'u' -a "$validity" != 'f' ] ; then
            continue
        fi

        # mark user ID acceptable
        uidOK=true

        # output a line for the primary key
        # 0 = ok, 1 = bad
        if [ "$keyOK" -a "$uidOK" -a "$lastKeyOK" ] ; then
            log "  * acceptable primary key."
            if [ -z "$sshKey" ] ; then
            log "    ! primary key could not be translated (not RSA or DSA?)."
            else
            echo "0:${sshKey}"
            fi
        else
            log "  - unacceptable primary key."
            if [ -z "$sshKey" ] ; then
            log "   ! primary key could not be translated (not RSA or DSA?)."
            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
            continue
        fi
        # if sub key capability is not ok, skip
        if ! check_capability "$usage" $requiredCapability ; then
            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 "$lastKeyOK" ] ; then
            log "  * acceptable sub key."
            if [ -z "$sshKey" ] ; then
            log "    ! sub key could not be translated (not RSA or DSA?)."
            else
            echo "0:${sshKey}"
            fi
        else
            log "  - unacceptable sub key."
            if [ -z "$sshKey" ] ; then
            log "    ! sub key could not be translated (not RSA or DSA?)."
            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 nKeys
    local nKeysOK
    local ok
    local sshKey
    local tmpfile

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

    log "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 the old host key line, and note if removed
    remove_line "$KNOWN_HOSTS" "$sshKey"

    # 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)
        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
    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 nHosts
    local nHostsOK
    local nHostsBAD
    local fileCheck
    local host

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

    nHostsOK=0
    nHostsBAD=0

    # set the trap to remove any lockfiles on exit
    trap "lockfile-remove $KNOWN_HOSTS" EXIT

    # create a lockfile on known_hosts
    lockfile-create "$KNOWN_HOSTS"

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

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

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

    # remove the lockfile
    lockfile-remove "$KNOWN_HOSTS"

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

    log "processing known_hosts file..."

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

    if [ -z "$hosts" ] ; then
    log "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

    userID="$1"

    log "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 userID
    local nIDs
    local nIDsOK
    local nIDsBAD
    local fileCheck

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

    nIDsOK=0
    nIDsBAD=0

    # set the trap to remove any lockfiles on exit
    trap "lockfile-remove $AUTHORIZED_KEYS" EXIT

    # create a lockfile on authorized_keys
    lockfile-create "$AUTHORIZED_KEYS"

    # 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"

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

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

    # remove the lockfile
    lockfile-remove "$AUTHORIZED_KEYS"

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

    log "processing authorized_user_ids file..."

    if ! meat "$authorizedUserIDs" > /dev/null ; then
    log "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[@]}"
}