path: root/src/monkeysphere-authentication

#!/usr/bin/env bash

# monkeysphere-authentication: Monkeysphere authentication 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)

SYSSHAREDIR=${MONKEYSPHERE_SYSSHAREDIR:-"/usr/share/monkeysphere"}
export SYSSHAREDIR
. "${SYSSHAREDIR}/common" || exit 1

SYSDATADIR=${MONKEYSPHERE_SYSDATADIR:-"/var/lib/monkeysphere/authentication"}
export SYSDATADIR

# monkeysphere temp directory, in sysdatadir to enable atomic moves of
# authorized_keys files
MSTMPDIR="${SYSDATADIR}/tmp"
export MSTMPDIR

# 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 authentication admin tool.

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

 expert
  diagnostics (d)                    monkeysphere authentication status
  gpg-cmd CMD                        execute gpg command

 version (v)                         show version number
 help (h,?)                          this help

EOF
}

# function to run command as monkeysphere user
su_monkeysphere_user() {
    # if the current user is the monkeysphere user, then just eval
    # command
    if [ $(id -un) = "$MONKEYSPHERE_USER" ] ; then
    eval "$@"

    # otherwise su command as monkeysphere user
    else
    su "$MONKEYSPHERE_USER" -c "$@"
    fi
}

# 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 $@"
}

# check if user is root
is_root() {
    [ $(id -u 2>/dev/null) = '0' ]
}

# check that user is root, for functions that require root access
check_user() {
    is_root || failure "You must be root to run this command."
}

# output just key fingerprint
fingerprint_server_key() {
    # set the pipefail option so functions fails if can't read sec key
    set -o pipefail

    gpg_host --list-secret-keys --fingerprint \
    --with-colons --fixed-list-mode 2> /dev/null | \
    grep '^fpr:' | head -1 | cut -d: -f10 2>/dev/null
}

# function to check for host secret key
check_host_keyring() {
    fingerprint_server_key >/dev/null \
    || failure "You don't appear to have a Monkeysphere host key on this server.  Please run 'monkeysphere-server gen-key' first."
}

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
    local problemsfound=0

    # 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=$(advance_date $warnwindow +%s)

    if ! id monkeysphere >/dev/null ; then
    echo "! No monkeysphere user found!  Please create a monkeysphere system user with bash as its shell."
    problemsfound=$(($problemsfound+1))
    fi

    if ! [ -d "$SYSDATADIR" ] ; then
    echo "! no $SYSDATADIR directory found.  Please create it."
    problemsfound=$(($problemsfound+1))
    fi

    echo "Checking host GPG key..."
    if (( "$keysfound" < 1 )); then
    echo "! No host key found."
    echo " - Recommendation: run 'monkeysphere-server gen-key'"
    problemsfound=$(($problemsfound+1))
    elif (( "$keysfound" > 1 )); then
    echo "! More than one host key found?"
    # FIXME: recommend a way to resolve this
    problemsfound=$(($problemsfound+1))
    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"  < "$curdate" )); then
        echo "! Host key is expired."
        echo " - Recommendation: extend lifetime of key with 'monkeysphere-server extend-key'"
        problemsfound=$(($problemsfound+1))
        elif (( "$expire" < "$warndate" )); then
        echo "! Host key expires in less than $warnwindow:" $(advance_date $(( $expire - $curdate )) seconds +%F)
        echo " - Recommendation: extend lifetime of key with 'monkeysphere-server extend-key'"
        problemsfound=$(($problemsfound+1))
        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?"
        problemsfound=$(($problemsfound+1))
    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 ($(date +%F_%T)); use NTP?"
        problemsfound=$(($problemsfound+1))
        fi
        if [ "$expire" ] ; then
        if (( "$expire" < "$curdate" )); then
            echo "! User ID '$uid' is expired."
            # FIXME: recommend a way to resolve this
            problemsfound=$(($problemsfound+1))
        elif (( "$expire" < "$warndate" )); then
            echo "! User ID '$uid' expires in less than $warnwindow:" $(advance_date $(( $expire - $curdate )) seconds +%F)     
            # FIXME: recommend a way to resolve this
            problemsfound=$(($problemsfound+1))
        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 "${SYSDATADIR}/ssh_host_rsa_key" ] ; then
        echo "! The host key as prepared for SSH (${SYSDATADIR}/ssh_host_rsa_key) is missing or empty."
        problemsfound=$(($problemsfound+1))
    else
        if [ $(ls -l "${SYSDATADIR}/ssh_host_rsa_key" | cut -f1 -d\ ) != '-rw-------' ] ; then
        echo "! Permissions seem wrong for ${SYSDATADIR}/ssh_host_rsa_key -- should be 0600."
        problemsfound=$(($problemsfound+1))
        fi

        # propose changes needed for sshd_config (if any)
        if ! grep -q "^HostKey[[:space:]]\+${SYSDATADIR}/ssh_host_rsa_key$" "$sshd_config"; then
        echo "! $sshd_config does not point to the monkeysphere host key (${SYSDATADIR}/ssh_host_rsa_key)."
        echo " - Recommendation: add a line to $sshd_config: 'HostKey ${SYSDATADIR}/ssh_host_rsa_key'"
        problemsfound=$(($problemsfound+1))
        fi
        if badhostkeys=$(grep -i '^HostKey' "$sshd_config" | grep -v "^HostKey[[:space:]]\+${SYSDATADIR}/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 $sshd_config"
        problemsfound=$(($problemsfound+1))
        fi

        # FIXME: test (with ssh-keyscan?) that the running ssh
        # daemon is actually offering the monkeysphere host key.

    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

# FIXME: look at the timestamps on the monkeysphere-generated
# authorized_keys files -- warn if they seem out-of-date.

# FIXME: check for a cronjob that updates monkeysphere-generated
# authorized_keys?

    echo
    echo "Checking for MonkeySphere-enabled public-key authentication for users ..."
    # Ensure that User ID authentication is enabled:
    if ! grep -q "^AuthorizedKeysFile[[:space:]]\+${SYSDATADIR}/authorized_keys/%u$" "$sshd_config"; then
    echo "! $sshd_config does not point to monkeysphere authorized keys."
    echo " - Recommendation: add a line to $sshd_config: 'AuthorizedKeysFile ${SYSDATADIR}/authorized_keys/%u'"
    problemsfound=$(($problemsfound+1))
    fi
    if badauthorizedkeys=$(grep -i '^AuthorizedKeysFile' "$sshd_config" | grep -v "^AuthorizedKeysFile[[:space:]]\+${SYSDATADIR}/authorized_keys/%u$") ; then
    echo "! $sshd_config refers to non-monkeysphere authorized_keys files:"
    echo "$badauthorizedkeys"
    echo " - Recommendation: remove the above AuthorizedKeysFile lines from $sshd_config"
    problemsfound=$(($problemsfound+1))
    fi

    if [ "$problemsfound" -gt 0 ]; then
    echo "When the above $problemsfound issue"$(if [ "$problemsfound" -eq 1 ] ; then echo " is" ; else echo "s are" ; fi)" resolved, please re-run:"
    echo "  monkeysphere-server diagnostics"
    else
    echo "Everything seems to be in order!"
    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
    while true ; do
    case "$1" in
        -n|--domain)
        domain="$2"
        shift 2
        ;;
        -t|--trust)
        trust="$2"
        shift 2
        ;;
        -d|--depth)
        depth="$2"
        shift 2
        ;;
        *)
        if [ "$(echo "$1" | cut -c 1)" = '-' ] ; then
            failure "Unknown option '$1'.
Type '$PGRM help' for usage."
        fi
        break
        ;;
    esac
    done

    keyID="$1"
    if [ -z "$keyID" ] ; then
    failure "You must specify the key ID of a key to add, or specify a file to read the key from."
    fi
    if [ -f "$keyID" ] ; then
    echo "Reading key from file '$keyID':"
    importinfo=$(gpg_authentication "--import" < "$keyID" 2>&1) || failure "could not read key from '$keyID'"
    # FIXME: if this is tried when the key database is not
    # up-to-date, i got these errors (using set -x):

# ++ su -m monkeysphere -c '\''gpg --import'\''
# Warning: using insecure memory!
# gpg: key D21739E9: public key "Daniel Kahn Gillmor <dkg@fifthhorseman.net>" imported
# gpg: Total number processed: 1
# gpg:               imported: 1  (RSA: 1)
# gpg: can'\''t create `/var/monkeysphere/gnupg-host/pubring.gpg.tmp'\'': Permission denied
# gpg: failed to rebuild keyring cache: Permission denied
# gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
# gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
# gpg: next trustdb check due at 2009-01-10'
# + failure 'could not read key from '\''/root/dkg.gpg'\'''
# + echo 'could not read key from '\''/root/dkg.gpg'\'''

    keyID=$(echo "$importinfo" | grep '^gpg: key ' | cut -f2 -d: | cut -f3 -d\ )
    if [ -z "$keyID" ] || [ $(echo "$keyID" | wc -l) -ne 1 ] ; then
        failure "Expected there to be a single gpg key in the file."
    fi
    else
        # get the key from the key server
    gpg_authentication "--keyserver $KEYSERVER --recv-key '0x${keyID}!'" || failure "Could not receive a key with this ID from the '$KEYSERVER' keyserver."
    fi

    export 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
}

########################################################################
# 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 ${MONKEYSPHERE_SERVER_CONFIG:="${SYSCONFIGDIR}/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:="pool.sks-keyservers.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=${MONKEYSPHERE_GNUPGHOME_HOST:="${SYSDATADIR}/gnupg-host"}
GNUPGHOME_AUTHENTICATION=${MONKEYSPHERE_GNUPGHOME_AUTHENTICATION:="${SYSDATADIR}/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 $COMMAND in
    'update-users'|'update-user'|'u')
    check_user
    check_host_keyring
    update_users "$@"
    ;;

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

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

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

    'expert'|'e')
    check_user
    SUBCOMMAND="$1"
    shift
    case "$SUBCOMMAND" in
        'diagnostics'|'d')
        diagnostics
        ;;

        'gpg-cmd')
        gpg_authentication "$@"
        ;;

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

    'version'|'v')
    echo "$VERSION"
    ;;

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

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

exit "$RETURN"