| <?xml version="1.0" encoding="ISO-8859-1"?> |
| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" |
| "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd"> |
| <refentry id='dbusdaemon1'> |
| |
| <!-- dbus\-daemon manual page. |
| Copyright (C) 2003,2008 Red Hat, Inc. --> |
| |
| <refmeta> |
| <refentrytitle>dbus-daemon</refentrytitle> |
| <manvolnum>1</manvolnum> |
| <refmiscinfo class="manual">User Commands</refmiscinfo> |
| <refmiscinfo class="source">D-Bus</refmiscinfo> |
| <refmiscinfo class="version">@DBUS_VERSION@</refmiscinfo> |
| </refmeta> |
| <refnamediv> |
| <refname>dbus-daemon</refname> |
| <refpurpose>Message bus daemon</refpurpose> |
| </refnamediv> |
| <!-- body begins here --> |
| <refsynopsisdiv id='synopsis'> |
| <cmdsynopsis> |
| <command>dbus-daemon</command></cmdsynopsis> |
| <cmdsynopsis> |
| <command>dbus-daemon</command> <arg choice='opt'>--version </arg> |
| <arg choice='opt'>--session </arg> |
| <arg choice='opt'>--system </arg> |
| <arg choice='opt'>--config-file=<replaceable>FILE</replaceable></arg> |
| <arg choice='opt'><arg choice='plain'>--print-address </arg><arg choice='opt'><replaceable>=DESCRIPTOR</replaceable></arg></arg> |
| <arg choice='opt'><arg choice='plain'>--print-pid </arg><arg choice='opt'><replaceable>=DESCRIPTOR</replaceable></arg></arg> |
| <arg choice='opt'>--fork </arg> |
| <sbr/> |
| </cmdsynopsis> |
| </refsynopsisdiv> |
| |
| |
| <refsect1 id='description'><title>DESCRIPTION</title> |
| <para><command>dbus-daemon</command> is the D-Bus message bus daemon. See |
| <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink> for more information about |
| the big picture. D-Bus is first a library that provides one-to-one |
| communication between any two applications; <command>dbus-daemon</command> is an |
| application that uses this library to implement a message bus |
| daemon. Multiple programs connect to the message bus daemon and can |
| exchange messages with one another.</para> |
| |
| <para>There are two standard message bus instances: the systemwide message bus |
| (installed on many systems as the "messagebus" init service) and the |
| per-user-login-session message bus (started each time a user logs in). |
| <command>dbus-daemon</command> is used for both of these instances, but with |
| a different configuration file.</para> |
| |
| <para>The --session option is equivalent to |
| "--config-file=@EXPANDED_DATADIR@/dbus-1/session.conf" and the --system |
| option is equivalent to |
| "--config-file=@EXPANDED_DATADIR@/dbus-1/system.conf". By creating |
| additional configuration files and using the --config-file option, |
| additional special-purpose message bus daemons could be created.</para> |
| |
| <para>The systemwide daemon is normally launched by an init script, |
| standardly called simply "messagebus".</para> |
| |
| <para>The systemwide daemon is largely used for broadcasting system events, |
| such as changes to the printer queue, or adding/removing devices.</para> |
| |
| <para>The per-session daemon is used for various interprocess communication |
| among desktop applications (however, it is not tied to X or the GUI |
| in any way).</para> |
| |
| <para>SIGHUP will cause the D-Bus daemon to PARTIALLY reload its |
| configuration file and to flush its user/group information caches. Some |
| configuration changes would require kicking all apps off the bus; so they will |
| only take effect if you restart the daemon. Policy changes should take effect |
| with SIGHUP.</para> |
| |
| </refsect1> |
| |
| <refsect1 id='options'><title>OPTIONS</title> |
| <para>The following options are supported:</para> |
| <variablelist remap='TP'> |
| <varlistentry> |
| <term><option>--config-file=FILE</option></term> |
| <listitem> |
| <para>Use the given configuration file.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--fork</option></term> |
| <listitem> |
| <para>Force the message bus to fork and become a daemon, even if |
| the configuration file does not specify that it should. |
| In most contexts the configuration file already gets this |
| right, though. This option is not supported on Windows.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--nofork</option></term> |
| <listitem> |
| <para>Force the message bus not to fork and become a daemon, even if |
| the configuration file specifies that it should. On Windows, |
| the dbus-daemon never forks, so this option is allowed but does |
| nothing.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--print-address[=DESCRIPTOR]</option></term> |
| <listitem> |
| <para>Print the address of the message bus to standard output, or |
| to the given file descriptor. This is used by programs that |
| launch the message bus.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--print-pid[=DESCRIPTOR]</option></term> |
| <listitem> |
| <para>Print the process ID of the message bus to standard output, or |
| to the given file descriptor. This is used by programs that |
| launch the message bus.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--session</option></term> |
| <listitem> |
| <para>Use the standard configuration file for the per-login-session message |
| bus.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--system</option></term> |
| <listitem> |
| <para>Use the standard configuration file for the systemwide message bus.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--version</option></term> |
| <listitem> |
| <para>Print the version of the daemon.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--introspect</option></term> |
| <listitem> |
| <para>Print the introspection information for all D-Bus internal interfaces.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--address[=ADDRESS]</option></term> |
| <listitem> |
| <para>Set the address to listen on. This option overrides the address |
| configured in the configuration file.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--systemd-activation</option></term> |
| <listitem> |
| <para>Enable systemd-style service activation. Only useful in conjunction |
| with the systemd system and session manager on Linux.</para> |
| </listitem> |
| </varlistentry> |
| <varlistentry> |
| <term><option>--nopidfile</option></term> |
| <listitem> |
| <para>Don't write a PID file even if one is configured in the configuration |
| files.</para> |
| |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1 id='configuration_file'><title>CONFIGURATION FILE</title> |
| <para>A message bus daemon has a configuration file that specializes it |
| for a particular application. For example, one configuration |
| file might set up the message bus to be a systemwide message bus, |
| while another might set it up to be a per-user-login-session bus.</para> |
| |
| <para>The configuration file also establishes resource limits, security |
| parameters, and so forth.</para> |
| |
| <para>The configuration file is not part of any interoperability |
| specification and its backward compatibility is not guaranteed; this |
| document is documentation, not specification.</para> |
| |
| <para>The standard systemwide and per-session message bus setups are |
| configured in the files "@EXPANDED_DATADIR@/dbus-1/system.conf" and |
| "@EXPANDED_DATADIR@/dbus-1/session.conf". These files normally |
| <include> a system-local.conf or session-local.conf in |
| @EXPANDED_SYSCONFDIR@/dbus-1; you can put local |
| overrides in those files to avoid modifying the primary configuration |
| files.</para> |
| |
| |
| <para>The configuration file is an XML document. It must have the following |
| doctype declaration:</para> |
| <literallayout remap='.nf'> |
| |
| <!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-Bus Bus Configuration 1.0//EN" |
| "<ulink url='http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd'>http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd</ulink>"> |
| |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>The following elements may be present in the configuration file.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><busconfig></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>Root element.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><type></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>The well-known type of the message bus. Currently known values are |
| "system" and "session"; if other values are set, they should be |
| either added to the D-Bus specification, or namespaced. The last |
| <type> element "wins" (previous values are ignored). This element |
| only controls which message bus specific environment variables are |
| set in activated clients. Most of the policy that distinguishes a |
| session bus from the system bus is controlled from the other elements |
| in the configuration file.</para> |
| |
| |
| <para>If the well-known type of the message bus is "session", then the |
| DBUS_STARTER_BUS_TYPE environment variable will be set to "session" |
| and the DBUS_SESSION_BUS_ADDRESS environment variable will be set |
| to the address of the session bus. Likewise, if the type of the |
| message bus is "system", then the DBUS_STARTER_BUS_TYPE environment |
| variable will be set to "system" and the DBUS_SESSION_BUS_ADDRESS |
| environment variable will be set to the address of the system bus |
| (which is normally well known anyway).</para> |
| |
| |
| <para>Example: <type>session</type></para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><include></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>Include a file <include>filename.conf</include> at this point. If the |
| filename is relative, it is located relative to the configuration file |
| doing the including.</para> |
| |
| |
| <para><include> has an optional attribute "ignore_missing=(yes|no)" |
| which defaults to "no" if not provided. This attribute |
| controls whether it's a fatal error for the included file |
| to be absent.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><includedir></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>Include all files in <includedir>foo.d</includedir> at this |
| point. Files in the directory are included in undefined order. |
| Only files ending in ".conf" are included.</para> |
| |
| |
| <para>This is intended to allow extension of the system bus by particular |
| packages. For example, if CUPS wants to be able to send out |
| notification of printer queue changes, it could install a file to |
| @EXPANDED_DATADIR@/dbus-1/system.d or |
| @EXPANDED_SYSCONFDIR@/dbus-1/system.d that allowed all apps to receive |
| this message and allowed the printer daemon user to send it.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><user></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>The user account the daemon should run as, as either a username or a |
| UID. If the daemon cannot change to this UID on startup, it will exit. |
| If this element is not present, the daemon will not change or care |
| about its UID.</para> |
| |
| |
| <para>The last <user> entry in the file "wins", the others are ignored.</para> |
| |
| |
| <para>The user is changed after the bus has completed initialization. So |
| sockets etc. will be created before changing user, but no data will be |
| read from clients before changing user. This means that sockets |
| and PID files can be created in a location that requires root |
| privileges for writing.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><fork></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>If present, the bus daemon becomes a real daemon (forks |
| into the background, etc.). This is generally used |
| rather than the --fork command line option.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><keep_umask></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>If present, the bus daemon keeps its original umask when forking. |
| This may be useful to avoid affecting the behavior of child processes.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><syslog></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>If present, the bus daemon will log to syslog.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><pidfile></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>If present, the bus daemon will write its pid to the specified file. |
| The --nopidfile command-line option takes precedence over this setting.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><allow_anonymous></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>If present, connections that authenticated using the ANONYMOUS |
| mechanism will be authorized to connect. This option has no practical |
| effect unless the ANONYMOUS mechanism has also been enabled using the |
| <emphasis remap='I'><auth></emphasis> element, described below.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><listen></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>Add an address that the bus should listen on. The |
| address is in the standard D-Bus format that contains |
| a transport name plus possible parameters/options.</para> |
| |
| |
| <para>Example: <listen>unix:path=/tmp/foo</listen></para> |
| |
| |
| <para>Example: <listen>tcp:host=localhost,port=1234</listen></para> |
| |
| |
| <para>If there are multiple <listen> elements, then the bus listens |
| on multiple addresses. The bus will pass its address to |
| started services or other interested parties with |
| the last address given in <listen> first. That is, |
| apps will try to connect to the last <listen> address first.</para> |
| |
| |
| <para>tcp sockets can accept IPv4 addresses, IPv6 addresses or hostnames. |
| If a hostname resolves to multiple addresses, the server will bind |
| to all of them. The family=ipv4 or family=ipv6 options can be used |
| to force it to bind to a subset of addresses</para> |
| |
| |
| <para>Example: <listen>tcp:host=localhost,port=0,family=ipv4</listen></para> |
| |
| |
| <para>A special case is using a port number of zero (or omitting the port), |
| which means to choose an available port selected by the operating |
| system. The port number chosen can be obtained with the |
| --print-address command line parameter and will be present in other |
| cases where the server reports its own address, such as when |
| DBUS_SESSION_BUS_ADDRESS is set.</para> |
| |
| |
| <para>Example: <listen>tcp:host=localhost,port=0</listen></para> |
| |
| |
| <para>tcp/nonce-tcp addresses also allow a bind=hostname option, |
| used in a listenable address to configure the interface on which |
| the server will listen: either the hostname is the IP address of |
| one of the local machine's interfaces (most commonly 127.0.0.1), |
| a DNS name that resolves to one of those IP addresses, '0.0.0.0' |
| to listen on all IPv4 interfaces simultaneously, or '::' |
| to listen on all IPv4 and IPv6 interfaces simultaneously (if supported |
| by the OS). If not specified, |
| the default is the same value as "host".</para> |
| |
| |
| <para>Example: <listen>tcp:host=localhost,bind=0.0.0.0,port=0</listen></para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><auth></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>Lists permitted authorization mechanisms. If this element doesn't |
| exist, then all known mechanisms are allowed. If there are multiple |
| <auth> elements, all the listed mechanisms are allowed. The order in |
| which mechanisms are listed is not meaningful.</para> |
| |
| |
| <para>Example: <auth>EXTERNAL</auth></para> |
| |
| |
| <para>Example: <auth>DBUS_COOKIE_SHA1</auth></para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><servicedir></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>Adds a directory to scan for .service files. Directories are |
| scanned starting with the first to appear in the config file |
| (the first .service file found that provides a particular |
| service will be used).</para> |
| |
| |
| <para>Service files tell the bus how to automatically start a program. |
| They are primarily used with the per-user-session bus, |
| not the systemwide bus.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><standard_session_servicedirs/></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para><standard_session_servicedirs/> is equivalent to specifying a series |
| of <servicedir/> elements for each of the data directories in the "XDG |
| Base Directory Specification" with the subdirectory "dbus-1/services", |
| so for example "/usr/share/dbus-1/services" would be among the |
| directories searched.</para> |
| |
| |
| <para>The "XDG Base Directory Specification" can be found at |
| <ulink url='http://freedesktop.org/wiki/Standards/basedir-spec'>http://freedesktop.org/wiki/Standards/basedir-spec</ulink> if it hasn't moved, |
| otherwise try your favorite search engine.</para> |
| |
| |
| <para>The <standard_session_servicedirs/> option is only relevant to the |
| per-user-session bus daemon defined in |
| @EXPANDED_SYSCONFDIR@/dbus-1/session.conf. Putting it in any other |
| configuration file would probably be nonsense.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><standard_system_servicedirs/></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para><standard_system_servicedirs/> specifies the standard system-wide |
| activation directories that should be searched for service files. |
| This option defaults to @EXPANDED_DATADIR@/dbus-1/system-services.</para> |
| |
| |
| <para>The <standard_system_servicedirs/> option is only relevant to the |
| per-system bus daemon defined in |
| @EXPANDED_DATADIR@/dbus-1/system.conf. Putting it in any other |
| configuration file would probably be nonsense.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><servicehelper/></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para><servicehelper/> specifies the setuid helper that is used to launch |
| system daemons with an alternate user. Typically this should be |
| the dbus-daemon-launch-helper executable in located in libexec.</para> |
| |
| |
| <para>The <servicehelper/> option is only relevant to the per-system bus daemon |
| defined in @EXPANDED_DATADIR@/dbus-1/system.conf. Putting it in any other |
| configuration file would probably be nonsense.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><limit></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para><limit> establishes a resource limit. For example:</para> |
| <literallayout remap='.nf'> |
| <limit name="max_message_size">64</limit> |
| <limit name="max_completed_connections">512</limit> |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>The name attribute is mandatory. |
| Available limit names are:</para> |
| <literallayout remap='.nf'> |
| "max_incoming_bytes" : total size in bytes of messages |
| incoming from a single connection |
| "max_incoming_unix_fds" : total number of unix fds of messages |
| incoming from a single connection |
| "max_outgoing_bytes" : total size in bytes of messages |
| queued up for a single connection |
| "max_outgoing_unix_fds" : total number of unix fds of messages |
| queued up for a single connection |
| "max_message_size" : max size of a single message in |
| bytes |
| "max_message_unix_fds" : max unix fds of a single message |
| "service_start_timeout" : milliseconds (thousandths) until |
| a started service has to connect |
| "auth_timeout" : milliseconds (thousandths) a |
| connection is given to |
| authenticate |
| "pending_fd_timeout" : milliseconds (thousandths) a |
| fd is given to be transmitted to |
| dbus-daemon before disconnecting the |
| connection |
| "max_completed_connections" : max number of authenticated connections |
| "max_incomplete_connections" : max number of unauthenticated |
| connections |
| "max_connections_per_user" : max number of completed connections from |
| the same user |
| "max_pending_service_starts" : max number of service launches in |
| progress at the same time |
| "max_names_per_connection" : max number of names a single |
| connection can own |
| "max_match_rules_per_connection": max number of match rules for a single |
| connection |
| "max_replies_per_connection" : max number of pending method |
| replies per connection |
| (number of calls-in-progress) |
| "reply_timeout" : milliseconds (thousandths) |
| until a method call times out |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>The max incoming/outgoing queue sizes allow a new message to be queued |
| if one byte remains below the max. So you can in fact exceed the max |
| by max_message_size.</para> |
| |
| |
| <para>max_completed_connections divided by max_connections_per_user is the |
| number of users that can work together to denial-of-service all other users by using |
| up all connections on the systemwide bus.</para> |
| |
| |
| <para>Limits are normally only of interest on the systemwide bus, not the user session |
| buses.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><policy></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>The <policy> element defines a security policy to be applied to a particular |
| set of connections to the bus. A policy is made up of |
| <allow> and <deny> elements. Policies are normally used with the systemwide bus; |
| they are analogous to a firewall in that they allow expected traffic |
| and prevent unexpected traffic.</para> |
| |
| |
| <para>Currently, the system bus has a default-deny policy for sending method calls |
| and owning bus names. Everything else, in particular reply messages, receive |
| checks, and signals has a default allow policy.</para> |
| |
| |
| <para>In general, it is best to keep system services as small, targeted programs which |
| run in their own process and provide a single bus name. Then, all that is needed |
| is an <allow> rule for the "own" permission to let the process claim the bus |
| name, and a "send_destination" rule to allow traffic from some or all uids to |
| your service.</para> |
| |
| |
| <para>The <policy> element has one of four attributes:</para> |
| <literallayout remap='.nf'> |
| context="(default|mandatory)" |
| at_console="(true|false)" |
| user="username or userid" |
| group="group name or gid" |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>Policies are applied to a connection as follows:</para> |
| <literallayout remap='.nf'> |
| - all context="default" policies are applied |
| - all group="connection's user's group" policies are applied |
| in undefined order |
| - all user="connection's auth user" policies are applied |
| in undefined order |
| - all at_console="true" policies are applied |
| - all at_console="false" policies are applied |
| - all context="mandatory" policies are applied |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>Policies applied later will override those applied earlier, |
| when the policies overlap. Multiple policies with the same |
| user/group/context are applied in the order they appear |
| in the config file.</para> |
| |
| <variablelist remap='TP'> |
| <varlistentry> |
| <term><emphasis remap='I'><deny></emphasis></term> |
| <listitem> |
| <para><emphasis remap='I'><allow></emphasis></para> |
| |
| </listitem> |
| </varlistentry> |
| </variablelist> |
| |
| <para>A <deny> element appears below a <policy> element and prohibits some |
| action. The <allow> element makes an exception to previous <deny> |
| statements, and works just like <deny> but with the inverse meaning.</para> |
| |
| |
| <para>The possible attributes of these elements are:</para> |
| <literallayout remap='.nf'> |
| send_interface="interface_name" |
| send_member="method_or_signal_name" |
| send_error="error_name" |
| send_destination="name" |
| send_type="method_call" | "method_return" | "signal" | "error" |
| send_path="/path/name" |
| |
| receive_interface="interface_name" |
| receive_member="method_or_signal_name" |
| receive_error="error_name" |
| receive_sender="name" |
| receive_type="method_call" | "method_return" | "signal" | "error" |
| receive_path="/path/name" |
| |
| send_requested_reply="true" | "false" |
| receive_requested_reply="true" | "false" |
| |
| eavesdrop="true" | "false" |
| |
| own="name" |
| own_prefix="name" |
| user="username" |
| group="groupname" |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>Examples:</para> |
| <literallayout remap='.nf'> |
| <deny send_destination="org.freedesktop.Service" send_interface="org.freedesktop.System" send_member="Reboot"/> |
| <deny send_destination="org.freedesktop.System"/> |
| <deny receive_sender="org.freedesktop.System"/> |
| <deny user="john"/> |
| <deny group="enemies"/> |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>The <deny> element's attributes determine whether the deny "matches" a |
| particular action. If it matches, the action is denied (unless later |
| rules in the config file allow it).</para> |
| |
| <para>send_destination and receive_sender rules mean that messages may not be |
| sent to or received from the *owner* of the given name, not that |
| they may not be sent *to that name*. That is, if a connection |
| owns services A, B, C, and sending to A is denied, sending to B or C |
| will not work either.</para> |
| |
| <para>The other send_* and receive_* attributes are purely textual/by-value |
| matches against the given field in the message header.</para> |
| |
| <para>"Eavesdropping" occurs when an application receives a message that |
| was explicitly addressed to a name the application does not own, or |
| is a reply to such a message. Eavesdropping thus only applies to |
| messages that are addressed to services and replies to such messages |
| (i.e. it does not apply to signals).</para> |
| |
| <para>For <allow>, eavesdrop="true" indicates that the rule matches even |
| when eavesdropping. eavesdrop="false" is the default and means that |
| the rule only allows messages to go to their specified recipient. |
| For <deny>, eavesdrop="true" indicates that the rule matches |
| only when eavesdropping. eavesdrop="false" is the default for <deny> |
| also, but here it means that the rule applies always, even when |
| not eavesdropping. The eavesdrop attribute can only be combined with |
| send and receive rules (with send_* and receive_* attributes).</para> |
| |
| <para>The [send|receive]_requested_reply attribute works similarly to the eavesdrop |
| attribute. It controls whether the <deny> or <allow> matches a reply |
| that is expected (corresponds to a previous method call message). |
| This attribute only makes sense for reply messages (errors and method |
| returns), and is ignored for other message types.</para> |
| |
| |
| <para>For <allow>, [send|receive]_requested_reply="true" is the default and indicates that |
| only requested replies are allowed by the |
| rule. [send|receive]_requested_reply="false" means that the rule allows any reply |
| even if unexpected.</para> |
| |
| |
| <para>For <deny>, [send|receive]_requested_reply="false" is the default but indicates that |
| the rule matches only when the reply was not |
| requested. [send|receive]_requested_reply="true" indicates that the rule applies |
| always, regardless of pending reply state.</para> |
| |
| |
| <para>user and group denials mean that the given user or group may |
| not connect to the message bus.</para> |
| |
| |
| <para>For "name", "username", "groupname", etc. |
| the character "*" can be substituted, meaning "any." Complex globs |
| like "foo.bar.*" aren't allowed for now because they'd be work to |
| implement and maybe encourage sloppy security anyway.</para> |
| |
| |
| <para><allow own_prefix="a.b"/> allows you to own the name "a.b" or any |
| name whose first dot-separated elements are "a.b": in particular, |
| you can own "a.b.c" or "a.b.c.d", but not "a.bc" or "a.c". |
| This is useful when services like Telepathy and ReserveDevice |
| define a meaning for subtrees of well-known names, such as |
| org.freedesktop.Telepathy.ConnectionManager.(anything) |
| and org.freedesktop.ReserveDevice1.(anything).</para> |
| |
| |
| <para>It does not make sense to deny a user or group inside a <policy> |
| for a user or group; user/group denials can only be inside |
| context="default" or context="mandatory" policies.</para> |
| |
| |
| <para>A single <deny> rule may specify combinations of attributes such as |
| send_destination and send_interface and send_type. In this case, the |
| denial applies only if both attributes match the message being denied. |
| e.g. <deny send_interface="foo.bar" send_destination="foo.blah"/> would |
| deny messages with the given interface AND the given bus name. |
| To get an OR effect you specify multiple <deny> rules.</para> |
| |
| |
| <para>You can't include both send_ and receive_ attributes on the same |
| rule, since "whether the message can be sent" and "whether it can be |
| received" are evaluated separately.</para> |
| |
| |
| <para>Be careful with send_interface/receive_interface, because the |
| interface field in messages is optional. In particular, do NOT |
| specify <deny send_interface="org.foo.Bar"/>! This will cause |
| no-interface messages to be blocked for all services, which is |
| almost certainly not what you intended. Always use rules of |
| the form: <deny send_interface="org.foo.Bar" send_destination="org.foo.Service"/></para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><selinux></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>The <selinux> element contains settings related to Security Enhanced Linux. |
| More details below.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><associate></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>An <associate> element appears below an <selinux> element and |
| creates a mapping. Right now only one kind of association is possible:</para> |
| <literallayout remap='.nf'> |
| <associate own="org.freedesktop.Foobar" context="foo_t"/> |
| </literallayout> <!-- .fi --> |
| |
| |
| <para>This means that if a connection asks to own the name |
| "org.freedesktop.Foobar" then the source context will be the context |
| of the connection and the target context will be "foo_t" - see the |
| short discussion of SELinux below.</para> |
| |
| |
| <para>Note, the context here is the target context when requesting a name, |
| NOT the context of the connection owning the name.</para> |
| |
| |
| <para>There's currently no way to set a default for owning any name, if |
| we add this syntax it will look like:</para> |
| <literallayout remap='.nf'> |
| <associate own="*" context="foo_t"/> |
| </literallayout> <!-- .fi --> |
| <para>If you find a reason this is useful, let the developers know. |
| Right now the default will be the security context of the bus itself.</para> |
| |
| |
| <para>If two <associate> elements specify the same name, the element |
| appearing later in the configuration file will be used.</para> |
| |
| <itemizedlist remap='TP'> |
| |
| <listitem><para><emphasis remap='I'><apparmor></emphasis></para></listitem> |
| |
| |
| </itemizedlist> |
| |
| <para>The <apparmor> element is used to configure AppArmor mediation on |
| the bus. It can contain one attribute that specifies the mediation mode:</para> |
| |
| <literallayout remap='.nf'> |
| <apparmor mode="(enabled|disabled|required)"/> |
| </literallayout> <!-- .fi --> |
| |
| <para>The default mode is "enabled". In "enabled" mode, AppArmor mediation |
| will be performed if AppArmor support is available in the kernel. If it is not |
| available, dbus-daemon will start but AppArmor mediation will not occur. In |
| "disabled" mode, AppArmor mediation is disabled. In "required" mode, AppArmor |
| mediation will be enabled if AppArmor support is available, otherwise |
| dbus-daemon will refuse to start.</para> |
| |
| <para>The AppArmor mediation mode of the bus cannot be changed after the bus |
| starts. Modifying the mode in the configuration file and sending a SIGHUP |
| signal to the daemon has no effect on the mediation mode.</para> |
| |
| </refsect1> |
| |
| <refsect1 id='selinux'><title>SELinux</title> |
| <para>See <ulink url='http://www.nsa.gov/selinux/'>http://www.nsa.gov/selinux/</ulink> for full details on SELinux. Some useful excerpts:</para> |
| |
| |
| <para>Every subject (process) and object (e.g. file, socket, IPC object, |
| etc) in the system is assigned a collection of security attributes, |
| known as a security context. A security context contains all of the |
| security attributes associated with a particular subject or object |
| that are relevant to the security policy.</para> |
| |
| |
| <para>In order to better encapsulate security contexts and to provide |
| greater efficiency, the policy enforcement code of SELinux typically |
| handles security identifiers (SIDs) rather than security contexts. A |
| SID is an integer that is mapped by the security server to a security |
| context at runtime.</para> |
| |
| |
| <para>When a security decision is required, the policy enforcement code |
| passes a pair of SIDs (typically the SID of a subject and the SID of |
| an object, but sometimes a pair of subject SIDs or a pair of object |
| SIDs), and an object security class to the security server. The object |
| security class indicates the kind of object, e.g. a process, a regular |
| file, a directory, a TCP socket, etc.</para> |
| |
| |
| <para>Access decisions specify whether or not a permission is granted for a |
| given pair of SIDs and class. Each object class has a set of |
| associated permissions defined to control operations on objects with |
| that class.</para> |
| |
| |
| <para>D-Bus performs SELinux security checks in two places.</para> |
| |
| |
| <para>First, any time a message is routed from one connection to another |
| connection, the bus daemon will check permissions with the security context of |
| the first connection as source, security context of the second connection |
| as target, object class "dbus" and requested permission "send_msg".</para> |
| |
| |
| <para>If a security context is not available for a connection |
| (impossible when using UNIX domain sockets), then the target |
| context used is the context of the bus daemon itself. |
| There is currently no way to change this default, because we're |
| assuming that only UNIX domain sockets will be used to |
| connect to the systemwide bus. If this changes, we'll |
| probably add a way to set the default connection context.</para> |
| |
| |
| <para>Second, any time a connection asks to own a name, |
| the bus daemon will check permissions with the security |
| context of the connection as source, the security context specified |
| for the name in the config file as target, object |
| class "dbus" and requested permission "acquire_svc".</para> |
| |
| |
| <para>The security context for a bus name is specified with the |
| <associate> element described earlier in this document. |
| If a name has no security context associated in the |
| configuration file, the security context of the bus daemon |
| itself will be used.</para> |
| |
| </refsect1> |
| |
| <refsect1 id='apparmor'><title>AppArmor</title> |
| <para>The AppArmor confinement context is stored when applications connect to |
| the bus. The confinement context consists of a label and a confinement mode. |
| When a security decision is required, the daemon uses the confinement context |
| to query the AppArmor policy to determine if the action should be allowed or |
| denied and if the action should be audited.</para> |
| |
| <para>The daemon performs AppArmor security checks in three places.</para> |
| |
| <para>First, any time a message is routed from one connection to another |
| connection, the bus daemon will check permissions with the label of the first |
| connection as source, label and/or connection name of the second connection as |
| target, along with the bus name, the path name, the interface name, and the |
| member name. Reply messages, such as method_return and error messages, are |
| implicitly allowed if they are in response to a message that has already been |
| allowed.</para> |
| |
| <para>Second, any time a connection asks to own a name, the bus daemon will |
| check permissions with the label of the connection as source, the requested |
| name as target, along with the bus name.</para> |
| |
| <para>Third, any time a connection attempts to eavesdrop, the bus daemon will |
| check permissions with the label of the connection as the source, along with |
| the bus name.</para> |
| |
| <para>AppArmor rules for bus mediation are not stored in the bus configuration |
| files. They are stored in the application's AppArmor profile. Please see |
| <emphasis remap='I'>apparmor.d(5)</emphasis> for more details.</para> |
| |
| </refsect1> |
| |
| <refsect1 id='debugging'><title>DEBUGGING</title> |
| <para>If you're trying to figure out where your messages are going or why |
| you aren't getting messages, there are several things you can try.</para> |
| |
| <para>Remember that the system bus is heavily locked down and if you |
| haven't installed a security policy file to allow your message |
| through, it won't work. For the session bus, this is not a concern.</para> |
| |
| <para>The simplest way to figure out what's happening on the bus is to run |
| the <emphasis remap='I'>dbus-monitor</emphasis> program, which comes with the D-Bus |
| package. You can also send test messages with <emphasis remap='I'>dbus-send</emphasis>. These |
| programs have their own man pages.</para> |
| |
| <para>If you want to know what the daemon itself is doing, you might consider |
| running a separate copy of the daemon to test against. This will allow you |
| to put the daemon under a debugger, or run it with verbose output, without |
| messing up your real session and system daemons.</para> |
| |
| <para>To run a separate test copy of the daemon, for example you might open a terminal |
| and type:</para> |
| <literallayout remap='.nf'> |
| DBUS_VERBOSE=1 dbus-daemon --session --print-address |
| </literallayout> <!-- .fi --> |
| |
| <para>The test daemon address will be printed when the daemon starts. You will need |
| to copy-and-paste this address and use it as the value of the |
| DBUS_SESSION_BUS_ADDRESS environment variable when you launch the applications |
| you want to test. This will cause those applications to connect to your |
| test bus instead of the DBUS_SESSION_BUS_ADDRESS of your real session bus.</para> |
| |
| <para>DBUS_VERBOSE=1 will have NO EFFECT unless your copy of D-Bus |
| was compiled with verbose mode enabled. This is not recommended in |
| production builds due to performance impact. You may need to rebuild |
| D-Bus if your copy was not built with debugging in mind. (DBUS_VERBOSE |
| also affects the D-Bus library and thus applications using D-Bus; it may |
| be useful to see verbose output on both the client side and from the daemon.)</para> |
| |
| <para>If you want to get fancy, you can create a custom bus |
| configuration for your test bus (see the session.conf and system.conf |
| files that define the two default configurations for example). This |
| would allow you to specify a different directory for .service files, |
| for example.</para> |
| |
| </refsect1> |
| |
| <refsect1 id='author'><title>AUTHOR</title> |
| <para>See <ulink url='http://www.freedesktop.org/software/dbus/doc/AUTHORS'>http://www.freedesktop.org/software/dbus/doc/AUTHORS</ulink></para> |
| |
| </refsect1> |
| |
| <refsect1 id='bugs'><title>BUGS</title> |
| <para>Please send bug reports to the D-Bus mailing list or bug tracker, |
| see <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink></para> |
| </refsect1> |
| </refentry> |