apt/cmdline/apt-key.in

#!/bin/sh

set -e
unset GREP_OPTIONS

GPG_CMD="gpg --ignore-time-conflict --no-options --no-default-keyring"

# gpg needs (in different versions more or less) files to function correctly,
# so we give it its own homedir and generate some valid content for it
GPGHOMEDIR="$(mktemp -d)"
CURRENTTRAP="${CURRENTTRAP} rm -rf '${GPGHOMEDIR}';"
trap "${CURRENTTRAP}" 0 HUP INT QUIT ILL ABRT FPE SEGV PIPE TERM
chmod 700 "$GPGHOMEDIR"
# We don't use a secret keyring, of course, but gpg panics and
# implodes if there isn't one available - and writeable for imports
SECRETKEYRING="${GPGHOMEDIR}/secring.gpg"
touch $SECRETKEYRING
GPG_CMD="$GPG_CMD --homedir $GPGHOMEDIR"
# create the trustdb with an (empty) dummy keyring
# older gpgs required it, newer gpgs even warn that it isn't needed,
# but require it nonetheless for some commands, so we just play safe
# here for the foreseeable future and create a dummy one
$GPG_CMD --quiet --check-trustdb --keyring $SECRETKEYRING >/dev/null 2>&1
# tell gpg that it shouldn't try to maintain a trustdb file
GPG_CMD="$GPG_CMD --no-auto-check-trustdb --trust-model always"
GPG="$GPG_CMD"

APT_DIR="/"
eval $(apt-config shell APT_DIR Dir)

MASTER_KEYRING='&keyring-master-filename;'
eval $(apt-config shell MASTER_KEYRING APT::Key::MasterKeyring)
ARCHIVE_KEYRING='&keyring-filename;'
eval $(apt-config shell ARCHIVE_KEYRING APT::Key::ArchiveKeyring)
REMOVED_KEYS='&keyring-removed-filename;'
eval $(apt-config shell REMOVED_KEYS APT::Key::RemovedKeys)
ARCHIVE_KEYRING_URI='&keyring-uri;'
eval $(apt-config shell ARCHIVE_KEYRING_URI APT::Key::ArchiveKeyringURI)
TMP_KEYRING=${APT_DIR}/var/lib/apt/keyrings/maybe-import-keyring.gpg

aptkey_echo() { echo "$@"; }

requires_root() {
	if [ "$(id -u)" -ne 0 ]; then
		echo >&2 "ERROR: This command can only be used by root."
		exit 1
	fi
}

add_keys_with_verify_against_master_keyring() {
    ADD_KEYRING=$1
    MASTER=$2

    if [ ! -f "$ADD_KEYRING" ]; then
	echo >&2 "ERROR: '$ADD_KEYRING' not found"
	return
    fi
    if [ ! -f "$MASTER" ]; then
	echo >&2 "ERROR: '$MASTER' not found"
	return
    fi

    # when adding new keys, make sure that the archive-master-keyring
    # is honored. so:
    #   all keys that are exported must have a valid signature
    #   from a key in the $distro-master-keyring
    add_keys=`$GPG_CMD --keyring $ADD_KEYRING --with-colons --list-keys | grep ^pub | cut -d: -f5`
    all_add_keys=`$GPG_CMD --keyring $ADD_KEYRING --with-colons --list-keys | grep ^[ps]ub | cut -d: -f5`
    master_keys=`$GPG_CMD --keyring $MASTER --with-colons --list-keys | grep ^pub | cut -d: -f5`

    # ensure there are no colisions LP: #857472
    for all_add_key in $all_add_keys; do
	for master_key in $master_keys; do
            if [ "$all_add_key" = "$master_key" ]; then
                echo >&2 "Keyid collision for '$all_add_key' detected, operation aborted"
                return 1
            fi
        done
    done
    
    for add_key in $add_keys; do
        # export the add keyring one-by-one
        rm -f $TMP_KEYRING
        $GPG_CMD --keyring $ADD_KEYRING --output $TMP_KEYRING --export $add_key 
        # check if signed with the master key and only add in this case
        ADDED=0
	for master_key in $master_keys; do
	    if $GPG_CMD --keyring $MASTER --keyring $TMP_KEYRING --check-sigs --with-colons $add_key | grep '^sig:!:' | cut -d: -f5 | grep -q $master_key; then
		$GPG --import $TMP_KEYRING
		ADDED=1
	    fi
	done
	if [ $ADDED = 0 ]; then
	    echo >&2 "Key '$add_key' not added. It is not signed with a master key"
	fi
    done
    rm -f $TMP_KEYRING
}

# update the current archive signing keyring from a network URI
# the archive-keyring keys needs to be signed with the master key
# (otherwise it does not make sense from a security POV)
net_update() {
    # Disabled for now as code is insecure (LP: #1013639 (and 857472, 1013128))
    APT_KEY_NET_UPDATE_ENABLED=""
    eval $(apt-config shell APT_KEY_NET_UPDATE_ENABLED APT::Key::Net-Update-Enabled)
    if [ -z "$APT_KEY_NET_UPDATE_ENABLED" ]; then
        exit 1
    fi

    if [ -z "$ARCHIVE_KEYRING_URI" ]; then
	echo >&2 "ERROR: Your distribution is not supported in net-update as no uri for the archive-keyring is set"
	exit 1
    fi
    # in theory we would need to depend on wget for this, but this feature
    # isn't useable in debian anyway as we have no keyring uri nor a master key
    if ! which wget >/dev/null 2>&1; then
	echo >&2 "ERROR: an installed wget is required for a network-based update"
	exit 1
    fi
    if [ ! -d ${APT_DIR}/var/lib/apt/keyrings ]; then
	mkdir -p ${APT_DIR}/var/lib/apt/keyrings
    fi
    keyring=${APT_DIR}/var/lib/apt/keyrings/$(basename $ARCHIVE_KEYRING_URI)
    old_mtime=0
    if [ -e $keyring ]; then
	old_mtime=$(stat -c %Y $keyring)
    fi
    (cd  ${APT_DIR}/var/lib/apt/keyrings; wget --timeout=90 -q -N $ARCHIVE_KEYRING_URI)
    if [ ! -e $keyring ]; then
	return
    fi
    new_mtime=$(stat -c %Y $keyring)
    if [ $new_mtime -ne $old_mtime ]; then
	aptkey_echo "Checking for new archive signing keys now"
	add_keys_with_verify_against_master_keyring $keyring $MASTER_KEYRING
    fi
}

update() {
    if [ ! -f $ARCHIVE_KEYRING ]; then
	echo >&2 "ERROR: Can't find the archive-keyring"
	echo >&2 "Is the &keyring-package; package installed?"
	exit 1
    fi

    # add new keys from the package;

    # we do not use add_keys_with_verify_against_master_keyring here,
    # because "update" is run on regular package updates.  A
    # attacker might as well replace the master-archive-keyring file
    # in the package and add his own keys. so this check wouldn't
    # add any security. we *need* this check on net-update though
    $GPG_CMD --quiet --batch --keyring $ARCHIVE_KEYRING --export | $GPG --import

    if [ -r "$REMOVED_KEYS" ]; then
	# remove no-longer supported/used keys
	$GPG_CMD --keyring $REMOVED_KEYS --with-colons --list-keys | grep ^pub | cut -d: -f5 | while read key; do
	    foreach_keyring_do 'remove_key_from_keyring' "$key"
	done
    else
	echo >&2 "Warning: removed keys keyring  $REMOVED_KEYS missing or not readable"
    fi
}

remove_key_from_keyring() {
    local KEYRINGFILE="$1"
    shift
    # non-existent keyrings have by definition no keys
    if [ ! -e "$KEYRINGFILE" ]; then
       return
    fi

    local GPG="$GPG_CMD --keyring $KEYRINGFILE"
    while [ -n "$1" ]; do
       local KEY="$1"
       shift
	# check if the key is in this keyring: the key id is in the 5 column at the end
	if ! $GPG --with-colons --list-keys 2>&1 | grep -q "^pub:[^:]*:[^:]*:[^:]*:[0-9A-F]*${KEY}:"; then
	    continue
	fi
	if [ ! -w "$KEYRINGFILE" ]; then
	    echo >&2 "Key ${KEY} is in keyring ${KEYRINGFILE}, but can't be removed as it is read only."
	    continue
	fi
	# check if it is the only key in the keyring and if so remove the keyring altogether
	if [ '1' = "$($GPG --with-colons --list-keys | grep "^pub:[^:]*:[^:]*:[^:]*:[0-9A-F]\+:" | wc -l)" ]; then
	    mv -f "$KEYRINGFILE" "${KEYRINGFILE}~" # behave like gpg
	    return
	fi
	# we can't just modify pointed to files as these might be in /usr or something
	local REALTARGET
	if [ -L "$KEYRINGFILE" ]; then
	    REALTARGET="$(readlink -f "$KEYRINGFILE")"
	    mv -f "$KEYRINGFILE" "${KEYRINGFILE}.dpkg-tmp"
	    cp -a "$REALTARGET" "$KEYRINGFILE"
	fi
	# delete the key from the keyring
	$GPG --batch --delete-key --yes "$KEY"
	if [ -n "$REALTARGET" ]; then
	    # the real backup is the old link, not the copy we made
	    mv -f "${KEYRINGFILE}.dpkg-tmp" "${KEYRINGFILE}~"
	fi
    done
}

foreach_keyring_do() {
   local ACTION="$1"
   shift
   # if a --keyring was given, just remove from there
   if [ -n "$FORCED_KEYRING" ]; then
	$ACTION "$FORCED_KEYRING" "$@"
   else
	# otherwise all known keyrings are up for inspection
	if [ -s "$TRUSTEDFILE" ]; then
	    $ACTION "$TRUSTEDFILE" "$@"
	fi
	local TRUSTEDPARTS="/etc/apt/trusted.gpg.d"
	eval $(apt-config shell TRUSTEDPARTS Dir::Etc::TrustedParts/d)
	if [ -d "$TRUSTEDPARTS" ]; then
	    # strip / suffix as gpg will double-slash in that case (#665411)
	    local STRIPPED_TRUSTEDPARTS="${TRUSTEDPARTS%/}"
	    if [ "${STRIPPED_TRUSTEDPARTS}/" = "$TRUSTEDPARTS" ]; then
		TRUSTEDPARTS="$STRIPPED_TRUSTEDPARTS"
	    fi
	    for trusted in $(run-parts --list "$TRUSTEDPARTS" --regex '^.*\.gpg$'); do
		if [ -s "$trusted" ]; then
		    $ACTION "$trusted" "$@"
		fi
	    done
	fi
   fi
}

list_keys_from_keyring() {
    local KEYRINGFILE="$1"
    shift
    # don't show the error message if this keyring doesn't include the key
    $GPG_CMD --keyring "$KEYRINGFILE" --batch --list-keys "$@" 2>/dev/null || true
}

fingerprint_keys_from_keyring() {
    local KEYRINGFILE="$1"
    shift
    # don't show the error message if this keyring doesn't include the fingerprint
    $GPG_CMD --keyring "$KEYRINGFILE" --batch --fingerprint "$@" 2>/dev/null || true
}

import_keys_from_keyring() {
    local IMPORT="$1"
    local KEYRINGFILE="$2"
    $GPG_CMD --keyring "$KEYRINGFILE" --batch --import "$IMPORT" >/dev/null 2>&1
}

setup_merged_keyring() {
    local TRUSTEDFILE_BAK="$TRUSTEDFILE"
    TRUSTEDFILE='/dev/null'
    foreach_keyring_do 'import_keys_from_keyring' "${GPGHOMEDIR}/trusted.gpg"
    TRUSTEDFILE="$TRUSTEDFILE_BAK"
    # mark it as non-writeable so users get errors if gnupg tries to modify it
    if [ -s "${GPGHOMEDIR}/trusted.gpg" ]; then
	chmod -w "${GPGHOMEDIR}/trusted.gpg"
	GPG="$GPG --keyring ${GPGHOMEDIR}/trusted.gpg"
    fi
    if [ -r "$TRUSTEDFILE" ]; then
	GPG="$GPG --keyring $TRUSTEDFILE --primary-keyring $TRUSTEDFILE"
    fi
}


usage() {
    echo "Usage: apt-key [--keyring file] [command] [arguments]"
    echo
    echo "Manage apt's list of trusted keys"
    echo
    echo "  apt-key add <file>          - add the key contained in <file> ('-' for stdin)"
    echo "  apt-key del <keyid>         - remove the key <keyid>"
    echo "  apt-key export <keyid>      - output the key <keyid>"
    echo "  apt-key exportall           - output all trusted keys"
    echo "  apt-key update              - update keys using the keyring package"
    echo "  apt-key net-update          - update keys using the network"
    echo "  apt-key list                - list keys"
    echo "  apt-key finger              - list fingerprints"
    echo "  apt-key adv                 - pass advanced options to gpg (download key)"
    echo
    echo "If no specific keyring file is given the command applies to all keyring files."
}

while [ -n "$1" ]; do
   case "$1" in
      --keyring)
	 shift
	 TRUSTEDFILE="$1"
	 FORCED_KEYRING="$1"
	 shift
	 ;;
      --fakeroot)
	 requires_root() { true; }
	 shift
	 ;;
      --quiet)
	 aptkey_echo() { true; }
	 shift
	 ;;
      --*)
	 echo >&2 "Unknown option: $1"
	 usage
	 exit 1;;
      *)
	 break;;
   esac
done

if [ -z "$TRUSTEDFILE" ]; then
   TRUSTEDFILE="/etc/apt/trusted.gpg"
   eval $(apt-config shell TRUSTEDFILE Apt::GPGV::TrustedKeyring)
   eval $(apt-config shell TRUSTEDFILE Dir::Etc::Trusted/f)
fi

command="$1"
if [ -z "$command" ]; then
    usage
    exit 1
fi
shift

if [ "$command" != "help" ]; then
    if ! which gpg >/dev/null 2>&1; then
	echo >&2 "Warning: gnupg does not seem to be installed."
	echo >&2 "Warning: apt-key requires gnupg for most operations."
	echo >&2
    fi

    # gpg defaults to mode 0600 for new keyrings. Create one with 0644 instead.
    if ! [ -e "$TRUSTEDFILE" ]; then
	if [ -w "$(dirname "$TRUSTEDFILE")" ]; then
	   touch -- "$TRUSTEDFILE"
	   chmod 0644 -- "$TRUSTEDFILE"
	fi
    fi
fi

case "$command" in
    add)
	requires_root
	setup_merged_keyring
	$GPG --quiet --batch --import "$@"
	aptkey_echo "OK"
        ;;
    del|rm|remove)
	requires_root
	foreach_keyring_do 'remove_key_from_keyring' "$@"
	aptkey_echo "OK"
        ;;
    update)
	requires_root
	setup_merged_keyring
	update
	;;
    net-update)
	requires_root
	setup_merged_keyring
	net_update
	;;
    list)
	foreach_keyring_do 'list_keys_from_keyring' "$@"
	;;
    finger*)
	foreach_keyring_do 'fingerprint_keys_from_keyring' "$@"
	;;
    export|exportall)
	foreach_keyring_do 'import_keys_from_keyring' "${GPGHOMEDIR}/trusted.gpg"
	$GPG_CMD --keyring "${GPGHOMEDIR}/trusted.gpg" --armor --export "$@"
	;;
    adv*)
	setup_merged_keyring
	aptkey_echo "Executing: $GPG $*"
	$GPG "$@"
	;;
    help)
        usage
        ;;
    *)
        usage
        exit 1
        ;;
esac