Emeric Vigier | 2f62582 | 2012-08-06 11:09:52 -0400 | [diff] [blame] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?> |
| 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| 3 | "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"> |
| 4 | <!-- lifted from troff+man by doclifter --> |
| 5 | <refentry id='dbus-daemon'> |
| 6 | <!-- --> |
| 7 | <!-- dbus\-daemon manual page. --> |
| 8 | <!-- Copyright (C) 2003 Red Hat, Inc. --> |
| 9 | |
| 10 | <refmeta> |
| 11 | <refentrytitle>dbus-daemon</refentrytitle> |
| 12 | <manvolnum>1</manvolnum> |
| 13 | </refmeta> |
| 14 | <refnamediv id='name'> |
| 15 | <refname>dbus-daemon</refname> |
| 16 | <refpurpose>Message bus daemon</refpurpose> |
| 17 | </refnamediv> |
| 18 | <!-- body begins here --> |
| 19 | <refsynopsisdiv id='synopsis'> |
| 20 | <cmdsynopsis> |
| 21 | <command>dbus-daemon</command></cmdsynopsis> |
| 22 | <cmdsynopsis> |
| 23 | <command>dbus-daemon</command> <arg choice='opt'>--version </arg> |
| 24 | <arg choice='opt'>--session </arg> |
| 25 | <arg choice='opt'>--system </arg> |
| 26 | <arg choice='opt'>--config-file=<replaceable>FILE</replaceable></arg> |
| 27 | <arg choice='opt'><arg choice='plain'>--print-address </arg><arg choice='opt'><replaceable>=DESCRIPTOR</replaceable></arg></arg> |
| 28 | <arg choice='opt'><arg choice='plain'>--print-pid </arg><arg choice='opt'><replaceable>=DESCRIPTOR</replaceable></arg></arg> |
| 29 | <arg choice='opt'>--fork </arg> |
| 30 | <sbr/> |
| 31 | </cmdsynopsis> |
| 32 | </refsynopsisdiv> |
| 33 | |
| 34 | |
| 35 | <refsect1 id='description'><title>DESCRIPTION</title> |
| 36 | <para><command>dbus-daemon</command> is the D-Bus message bus daemon. See |
| 37 | <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink> for more information about |
| 38 | the big picture. D-Bus is first a library that provides one-to-one |
| 39 | communication between any two applications; <command>dbus-daemon</command> is an |
| 40 | application that uses this library to implement a message bus |
| 41 | daemon. Multiple programs connect to the message bus daemon and can |
| 42 | exchange messages with one another.</para> |
| 43 | |
| 44 | |
| 45 | <para>There are two standard message bus instances: the systemwide message bus |
| 46 | (installed on many systems as the "messagebus" init service) and the |
| 47 | per-user-login-session message bus (started each time a user logs in). |
| 48 | <command>dbus-daemon</command> is used for both of these instances, but with |
| 49 | a different configuration file.</para> |
| 50 | |
| 51 | |
| 52 | <para>The --session option is equivalent to |
| 53 | "--config-file=/etc/dbus-1/session.conf" and the --system |
| 54 | option is equivalent to |
| 55 | "--config-file=/etc/dbus-1/system.conf". By creating |
| 56 | additional configuration files and using the --config-file option, |
| 57 | additional special-purpose message bus daemons could be created.</para> |
| 58 | |
| 59 | |
| 60 | <para>The systemwide daemon is normally launched by an init script, |
| 61 | standardly called simply "messagebus".</para> |
| 62 | |
| 63 | |
| 64 | <para>The systemwide daemon is largely used for broadcasting system events, |
| 65 | such as changes to the printer queue, or adding/removing devices.</para> |
| 66 | |
| 67 | |
| 68 | <para>The per-session daemon is used for various interprocess communication |
| 69 | among desktop applications (however, it is not tied to X or the GUI |
| 70 | in any way).</para> |
| 71 | |
| 72 | |
| 73 | <para>SIGHUP will cause the D-Bus daemon to PARTIALLY reload its |
| 74 | configuration file and to flush its user/group information caches. Some |
| 75 | configuration changes would require kicking all apps off the bus; so they will |
| 76 | only take effect if you restart the daemon. Policy changes should take effect |
| 77 | with SIGHUP.</para> |
| 78 | |
| 79 | </refsect1> |
| 80 | |
| 81 | <refsect1 id='options'><title>OPTIONS</title> |
| 82 | <para>The following options are supported:</para> |
| 83 | <variablelist remap='TP'> |
| 84 | <varlistentry> |
| 85 | <term><option>--config-file=FILE</option></term> |
| 86 | <listitem> |
| 87 | <para>Use the given configuration file.</para> |
| 88 | </listitem> |
| 89 | </varlistentry> |
| 90 | <varlistentry> |
| 91 | <term><option>--fork</option></term> |
| 92 | <listitem> |
| 93 | <para>Force the message bus to fork and become a daemon, even if |
| 94 | the configuration file does not specify that it should. |
| 95 | In most contexts the configuration file already gets this |
| 96 | right, though.</para> |
| 97 | </listitem> |
| 98 | </varlistentry> |
| 99 | <varlistentry> |
| 100 | <term><option>--print-address[=DESCRIPTOR]</option></term> |
| 101 | <listitem> |
| 102 | <para>Print the address of the message bus to standard output, or |
| 103 | to the given file descriptor. This is used by programs that |
| 104 | launch the message bus.</para> |
| 105 | </listitem> |
| 106 | </varlistentry> |
| 107 | <varlistentry> |
| 108 | <term><option>--print-pid[=DESCRIPTOR]</option></term> |
| 109 | <listitem> |
| 110 | <para>Print the process ID of the message bus to standard output, or |
| 111 | to the given file descriptor. This is used by programs that |
| 112 | launch the message bus.</para> |
| 113 | </listitem> |
| 114 | </varlistentry> |
| 115 | <varlistentry> |
| 116 | <term><option>--session</option></term> |
| 117 | <listitem> |
| 118 | <para>Use the standard configuration file for the per-login-session message |
| 119 | bus.</para> |
| 120 | </listitem> |
| 121 | </varlistentry> |
| 122 | <varlistentry> |
| 123 | <term><option>--system</option></term> |
| 124 | <listitem> |
| 125 | <para>Use the standard configuration file for the systemwide message bus.</para> |
| 126 | </listitem> |
| 127 | </varlistentry> |
| 128 | <varlistentry> |
| 129 | <term><option>--version</option></term> |
| 130 | <listitem> |
| 131 | <para>Print the version of the daemon.</para> |
| 132 | |
| 133 | </listitem> |
| 134 | </varlistentry> |
| 135 | </variablelist> |
| 136 | </refsect1> |
| 137 | |
| 138 | <refsect1 id='configuration_file'><title>CONFIGURATION FILE</title> |
| 139 | <para>A message bus daemon has a configuration file that specializes it |
| 140 | for a particular application. For example, one configuration |
| 141 | file might set up the message bus to be a systemwide message bus, |
| 142 | while another might set it up to be a per-user-login-session bus.</para> |
| 143 | |
| 144 | |
| 145 | <para>The configuration file also establishes resource limits, security |
| 146 | parameters, and so forth.</para> |
| 147 | |
| 148 | |
| 149 | <para>The configuration file is not part of any interoperability |
| 150 | specification and its backward compatibility is not guaranteed; this |
| 151 | document is documentation, not specification.</para> |
| 152 | |
| 153 | |
| 154 | <para>The standard systemwide and per-session message bus setups are |
| 155 | configured in the files "/etc/dbus-1/system.conf" and |
| 156 | "/etc/dbus-1/session.conf". These files normally |
| 157 | <include> a system-local.conf or session-local.conf; you can put local |
| 158 | overrides in those files to avoid modifying the primary configuration |
| 159 | files.</para> |
| 160 | |
| 161 | |
| 162 | <para>The configuration file is an XML document. It must have the following |
| 163 | doctype declaration:</para> |
| 164 | <literallayout remap='.nf'> |
| 165 | |
| 166 | <!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-Bus Bus Configuration 1.0//EN" |
| 167 | "<ulink url='http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd'>http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd</ulink>"> |
| 168 | |
| 169 | </literallayout> <!-- .fi --> |
| 170 | |
| 171 | |
| 172 | <para>The following elements may be present in the configuration file.</para> |
| 173 | |
| 174 | <variablelist remap='TP'> |
| 175 | <varlistentry> |
| 176 | <term><emphasis remap='I'><busconfig></emphasis></term> |
| 177 | <listitem> |
| 178 | <para></para> |
| 179 | </listitem> |
| 180 | </varlistentry> |
| 181 | </variablelist> |
| 182 | |
| 183 | <para>Root element.</para> |
| 184 | |
| 185 | <variablelist remap='TP'> |
| 186 | <varlistentry> |
| 187 | <term><emphasis remap='I'><type></emphasis></term> |
| 188 | <listitem> |
| 189 | |
| 190 | <para></para> <!-- FIXME: blank list item --> |
| 191 | </listitem> |
| 192 | </varlistentry> |
| 193 | </variablelist> |
| 194 | |
| 195 | <para>The well-known type of the message bus. Currently known values are |
| 196 | "system" and "session"; if other values are set, they should be |
| 197 | either added to the D-Bus specification, or namespaced. The last |
| 198 | <type> element "wins" (previous values are ignored).</para> |
| 199 | |
| 200 | |
| 201 | <para>Example: <type>session</type></para> |
| 202 | |
| 203 | <variablelist remap='TP'> |
| 204 | <varlistentry> |
| 205 | <term><emphasis remap='I'><include></emphasis></term> |
| 206 | <listitem> |
| 207 | <para></para> |
| 208 | </listitem> |
| 209 | </varlistentry> |
| 210 | </variablelist> |
| 211 | |
| 212 | <para>Include a file <include>filename.conf</include> at this point. If the |
| 213 | filename is relative, it is located relative to the configuration file |
| 214 | doing the including.</para> |
| 215 | |
| 216 | |
| 217 | <para><include> has an optional attribute "ignore_missing=(yes|no)" |
| 218 | which defaults to "no" if not provided. This attribute |
| 219 | controls whether it's a fatal error for the included file |
| 220 | to be absent.</para> |
| 221 | |
| 222 | <variablelist remap='TP'> |
| 223 | <varlistentry> |
| 224 | <term><emphasis remap='I'><includedir></emphasis></term> |
| 225 | <listitem> |
| 226 | |
| 227 | <para></para> <!-- FIXME: blank list item --> |
| 228 | </listitem> |
| 229 | </varlistentry> |
| 230 | </variablelist> |
| 231 | |
| 232 | <para>Include all files in <includedir>foo.d</includedir> at this |
| 233 | point. Files in the directory are included in undefined order. |
| 234 | Only files ending in ".conf" are included.</para> |
| 235 | |
| 236 | |
| 237 | <para>This is intended to allow extension of the system bus by particular |
| 238 | packages. For example, if CUPS wants to be able to send out |
| 239 | notification of printer queue changes, it could install a file to |
| 240 | /etc/dbus-1/system.d that allowed all apps to receive |
| 241 | this message and allowed the printer daemon user to send it.</para> |
| 242 | |
| 243 | <variablelist remap='TP'> |
| 244 | <varlistentry> |
| 245 | <term><emphasis remap='I'><user></emphasis></term> |
| 246 | <listitem> |
| 247 | |
| 248 | <para></para> <!-- FIXME: blank list item --> |
| 249 | </listitem> |
| 250 | </varlistentry> |
| 251 | </variablelist> |
| 252 | |
| 253 | <para>The user account the daemon should run as, as either a username or a |
| 254 | UID. If the daemon cannot change to this UID on startup, it will exit. |
| 255 | If this element is not present, the daemon will not change or care |
| 256 | about its UID.</para> |
| 257 | |
| 258 | |
| 259 | <para>The last <user> entry in the file "wins", the others are ignored.</para> |
| 260 | |
| 261 | |
| 262 | <para>The user is changed after the bus has completed initialization. So |
| 263 | sockets etc. will be created before changing user, but no data will be |
| 264 | read from clients before changing user. This means that sockets |
| 265 | and PID files can be created in a location that requires root |
| 266 | privileges for writing.</para> |
| 267 | |
| 268 | <variablelist remap='TP'> |
| 269 | <varlistentry> |
| 270 | <term><emphasis remap='I'><fork></emphasis></term> |
| 271 | <listitem> |
| 272 | <para></para> |
| 273 | </listitem> |
| 274 | </varlistentry> |
| 275 | </variablelist> |
| 276 | |
| 277 | <para>If present, the bus daemon becomes a real daemon (forks |
| 278 | into the background, etc.). This is generally used |
| 279 | rather than the --fork command line option.</para> |
| 280 | |
| 281 | <variablelist remap='TP'> |
| 282 | <varlistentry> |
| 283 | <term><emphasis remap='I'><listen></emphasis></term> |
| 284 | <listitem> |
| 285 | |
| 286 | <para></para> <!-- FIXME: blank list item --> |
| 287 | </listitem> |
| 288 | </varlistentry> |
| 289 | </variablelist> |
| 290 | |
| 291 | <para>Add an address that the bus should listen on. The |
| 292 | address is in the standard D-Bus format that contains |
| 293 | a transport name plus possible parameters/options.</para> |
| 294 | |
| 295 | |
| 296 | <para>Example: <listen>unix:path=/tmp/foo</listen></para> |
| 297 | |
| 298 | |
| 299 | <para>If there are multiple <listen> elements, then the bus listens |
| 300 | on multiple addresses. The bus will pass its address to |
| 301 | started services or other interested parties with |
| 302 | the last address given in <listen> first. That is, |
| 303 | apps will try to connect to the last <listen> address first.</para> |
| 304 | |
| 305 | <variablelist remap='TP'> |
| 306 | <varlistentry> |
| 307 | <term><emphasis remap='I'><auth></emphasis></term> |
| 308 | <listitem> |
| 309 | |
| 310 | <para></para> <!-- FIXME: blank list item --> |
| 311 | </listitem> |
| 312 | </varlistentry> |
| 313 | </variablelist> |
| 314 | |
| 315 | <para>Lists permitted authorization mechanisms. If this element doesn't |
| 316 | exist, then all known mechanisms are allowed. If there are multiple |
| 317 | <auth> elements, all the listed mechanisms are allowed. The order in |
| 318 | which mechanisms are listed is not meaningful.</para> |
| 319 | |
| 320 | |
| 321 | <para>Example: <auth>EXTERNAL</auth></para> |
| 322 | |
| 323 | |
| 324 | <para>Example: <auth>DBUS_COOKIE_SHA1</auth></para> |
| 325 | |
| 326 | <variablelist remap='TP'> |
| 327 | <varlistentry> |
| 328 | <term><emphasis remap='I'><servicedir></emphasis></term> |
| 329 | <listitem> |
| 330 | |
| 331 | <para></para> <!-- FIXME: blank list item --> |
| 332 | </listitem> |
| 333 | </varlistentry> |
| 334 | </variablelist> |
| 335 | |
| 336 | <para>Adds a directory to scan for .service files. Directories are |
| 337 | scanned starting with the last to appear in the config file |
| 338 | (the first .service file found that provides a particular |
| 339 | service will be used).</para> |
| 340 | |
| 341 | |
| 342 | <para>Service files tell the bus how to automatically start a program. |
| 343 | They are primarily used with the per-user-session bus, |
| 344 | not the systemwide bus.</para> |
| 345 | |
| 346 | <variablelist remap='TP'> |
| 347 | <varlistentry> |
| 348 | <term><emphasis remap='I'><standard_session_servicedirs/></emphasis></term> |
| 349 | <listitem> |
| 350 | |
| 351 | <para></para> <!-- FIXME: blank list item --> |
| 352 | </listitem> |
| 353 | </varlistentry> |
| 354 | </variablelist> |
| 355 | |
| 356 | <para><standard_session_servicedirs/> is equivalent to specifying a series |
| 357 | of <servicedir/> elements for each of the data directories in the "XDG |
| 358 | Base Directory Specification" with the subdirectory "dbus-1/services", |
| 359 | so for example "/usr/share/dbus-1/services" would be among the |
| 360 | directories searched.</para> |
| 361 | |
| 362 | |
| 363 | <para>The "XDG Base Directory Specification" can be found at |
| 364 | <ulink url='http://freedesktop.org/wiki/Standards/basedir-spec'>http://freedesktop.org/wiki/Standards/basedir-spec</ulink> if it hasn't moved, |
| 365 | otherwise try your favorite search engine.</para> |
| 366 | |
| 367 | |
| 368 | <para>The <standard_session_servicedirs/> option is only relevant to the |
| 369 | per-user-session bus daemon defined in |
| 370 | /etc/dbus-1/session.conf. Putting it in any other |
| 371 | configuration file would probably be nonsense.</para> |
| 372 | |
| 373 | <variablelist remap='TP'> |
| 374 | <varlistentry> |
| 375 | <term><emphasis remap='I'><limit></emphasis></term> |
| 376 | <listitem> |
| 377 | |
| 378 | <para></para> <!-- FIXME: blank list item --> |
| 379 | </listitem> |
| 380 | </varlistentry> |
| 381 | </variablelist> |
| 382 | |
| 383 | <para><limit> establishes a resource limit. For example:</para> |
| 384 | <literallayout remap='.nf'> |
| 385 | <limit name="max_message_size">64</limit> |
| 386 | <limit name="max_completed_connections">512</limit> |
| 387 | </literallayout> <!-- .fi --> |
| 388 | |
| 389 | |
| 390 | <para>The name attribute is mandatory. |
| 391 | Available limit names are:</para> |
| 392 | <literallayout remap='.nf'> |
| 393 | "max_incoming_bytes" : total size in bytes of messages |
| 394 | incoming from a single connection |
| 395 | "max_outgoing_bytes" : total size in bytes of messages |
| 396 | queued up for a single connection |
| 397 | "max_message_size" : max size of a single message in |
| 398 | bytes |
| 399 | "service_start_timeout" : milliseconds (thousandths) until |
| 400 | a started service has to connect |
| 401 | "auth_timeout" : milliseconds (thousandths) a |
| 402 | connection is given to |
| 403 | authenticate |
| 404 | "max_completed_connections" : max number of authenticated connections |
| 405 | "max_incomplete_connections" : max number of unauthenticated |
| 406 | connections |
| 407 | "max_connections_per_user" : max number of completed connections from |
| 408 | the same user |
| 409 | "max_pending_service_starts" : max number of service launches in |
| 410 | progress at the same time |
| 411 | "max_names_per_connection" : max number of names a single |
| 412 | connection can own |
| 413 | "max_match_rules_per_connection": max number of match rules for a single |
| 414 | connection |
| 415 | "max_replies_per_connection" : max number of pending method |
| 416 | replies per connection |
| 417 | (number of calls-in-progress) |
| 418 | "reply_timeout" : milliseconds (thousandths) |
| 419 | until a method call times out |
| 420 | </literallayout> <!-- .fi --> |
| 421 | |
| 422 | |
| 423 | <para>The max incoming/outgoing queue sizes allow a new message to be queued |
| 424 | if one byte remains below the max. So you can in fact exceed the max |
| 425 | by max_message_size.</para> |
| 426 | |
| 427 | |
| 428 | <para>max_completed_connections divided by max_connections_per_user is the |
| 429 | number of users that can work together to denial-of-service all other users by using |
| 430 | up all connections on the systemwide bus.</para> |
| 431 | |
| 432 | |
| 433 | <para>Limits are normally only of interest on the systemwide bus, not the user session |
| 434 | buses.</para> |
| 435 | |
| 436 | <variablelist remap='TP'> |
| 437 | <varlistentry> |
| 438 | <term><emphasis remap='I'><policy></emphasis></term> |
| 439 | <listitem> |
| 440 | |
| 441 | <para></para> <!-- FIXME: blank list item --> |
| 442 | </listitem> |
| 443 | </varlistentry> |
| 444 | </variablelist> |
| 445 | |
| 446 | <para>The <policy> element defines a security policy to be applied to a particular |
| 447 | set of connections to the bus. A policy is made up of |
| 448 | <allow> and <deny> elements. Policies are normally used with the systemwide bus; |
| 449 | they are analogous to a firewall in that they allow expected traffic |
| 450 | and prevent unexpected traffic.</para> |
| 451 | |
| 452 | |
| 453 | <para>The <policy> element has one of three attributes:</para> |
| 454 | <literallayout remap='.nf'> |
| 455 | context="(default|mandatory)" |
| 456 | user="username or userid" |
| 457 | group="group name or gid" |
| 458 | </literallayout> <!-- .fi --> |
| 459 | |
| 460 | |
| 461 | <para> |
| 462 | Policies are applied to a connection as follows:</para> |
| 463 | <literallayout remap='.nf'> |
| 464 | - all context="default" policies are applied |
| 465 | - all group="connection's user's group" policies are applied |
| 466 | in undefined order |
| 467 | - all user="connection's auth user" policies are applied |
| 468 | in undefined order |
| 469 | - all context="mandatory" policies are applied |
| 470 | </literallayout> <!-- .fi --> |
| 471 | |
| 472 | |
| 473 | <para>Policies applied later will override those applied earlier, |
| 474 | when the policies overlap. Multiple policies with the same |
| 475 | user/group/context are applied in the order they appear |
| 476 | in the config file.</para> |
| 477 | |
| 478 | <variablelist remap='TP'> |
| 479 | <varlistentry> |
| 480 | <term><emphasis remap='I'><deny></emphasis></term> |
| 481 | <listitem> |
| 482 | <para><emphasis remap='I'><allow></emphasis></para> |
| 483 | |
| 484 | </listitem> |
| 485 | </varlistentry> |
| 486 | </variablelist> |
| 487 | |
| 488 | <para>A <deny> element appears below a <policy> element and prohibits some |
| 489 | action. The <allow> element makes an exception to previous <deny> |
| 490 | statements, and works just like <deny> but with the inverse meaning.</para> |
| 491 | |
| 492 | |
| 493 | <para>The possible attributes of these elements are:</para> |
| 494 | <literallayout remap='.nf'> |
| 495 | send_interface="interface_name" |
| 496 | send_member="method_or_signal_name" |
| 497 | send_error="error_name" |
| 498 | send_destination="name" |
| 499 | send_type="method_call" | "method_return" | "signal" | "error" |
| 500 | send_path="/path/name" |
| 501 | |
| 502 | receive_interface="interface_name" |
| 503 | receive_member="method_or_signal_name" |
| 504 | receive_error="error_name" |
| 505 | receive_sender="name" |
| 506 | receive_type="method_call" | "method_return" | "signal" | "error" |
| 507 | receive_path="/path/name" |
| 508 | |
| 509 | send_requested_reply="true" | "false" |
| 510 | receive_requested_reply="true" | "false" |
| 511 | |
| 512 | eavesdrop="true" | "false" |
| 513 | |
| 514 | own="name" |
| 515 | user="username" |
| 516 | group="groupname" |
| 517 | </literallayout> <!-- .fi --> |
| 518 | |
| 519 | |
| 520 | <para>Examples:</para> |
| 521 | <literallayout remap='.nf'> |
| 522 | <deny send_interface="org.freedesktop.System" send_member="Reboot"/> |
| 523 | <deny receive_interface="org.freedesktop.System" receive_member="Reboot"/> |
| 524 | <deny own="org.freedesktop.System"/> |
| 525 | <deny send_destination="org.freedesktop.System"/> |
| 526 | <deny receive_sender="org.freedesktop.System"/> |
| 527 | <deny user="john"/> |
| 528 | <deny group="enemies"/> |
| 529 | </literallayout> <!-- .fi --> |
| 530 | |
| 531 | |
| 532 | <para>The <deny> element's attributes determine whether the deny "matches" a |
| 533 | particular action. If it matches, the action is denied (unless later |
| 534 | rules in the config file allow it).</para> |
| 535 | |
| 536 | |
| 537 | <para>send_destination and receive_sender rules mean that messages may not be |
| 538 | sent to or received from the *owner* of the given name, not that |
| 539 | they may not be sent *to that name*. That is, if a connection |
| 540 | owns services A, B, C, and sending to A is denied, sending to B or C |
| 541 | will not work either.</para> |
| 542 | |
| 543 | |
| 544 | <para>The other send_* and receive_* attributes are purely textual/by-value |
| 545 | matches against the given field in the message header.</para> |
| 546 | |
| 547 | |
| 548 | <para>"Eavesdropping" occurs when an application receives a message that |
| 549 | was explicitly addressed to a name the application does not own. |
| 550 | Eavesdropping thus only applies to messages that are addressed to |
| 551 | services (i.e. it does not apply to signals).</para> |
| 552 | |
| 553 | |
| 554 | <para>For <allow>, eavesdrop="true" indicates that the rule matches even |
| 555 | when eavesdropping. eavesdrop="false" is the default and means that |
| 556 | the rule only allows messages to go to their specified recipient. |
| 557 | For <deny>, eavesdrop="true" indicates that the rule matches |
| 558 | only when eavesdropping. eavesdrop="false" is the default for <deny> |
| 559 | also, but here it means that the rule applies always, even when |
| 560 | not eavesdropping. The eavesdrop attribute can only be combined with |
| 561 | receive rules (with receive_* attributes).</para> |
| 562 | |
| 563 | |
| 564 | |
| 565 | <para>The [send|receive]_requested_reply attribute works similarly to the eavesdrop |
| 566 | attribute. It controls whether the <deny> or <allow> matches a reply |
| 567 | that is expected (corresponds to a previous method call message). |
| 568 | This attribute only makes sense for reply messages (errors and method |
| 569 | returns), and is ignored for other message types.</para> |
| 570 | |
| 571 | |
| 572 | <para>For <allow>, [send|receive]_requested_reply="true" is the default and indicates that |
| 573 | only requested replies are allowed by the |
| 574 | rule. [send|receive]_requested_reply="false" means that the rule allows any reply |
| 575 | even if unexpected.</para> |
| 576 | |
| 577 | |
| 578 | <para>For <deny>, [send|receive]_requested_reply="false" is the default but indicates that |
| 579 | the rule matches only when the reply was not |
| 580 | requested. [send|receive]_requested_reply="true" indicates that the rule applies |
| 581 | always, regardless of pending reply state.</para> |
| 582 | |
| 583 | |
| 584 | <para>user and group denials mean that the given user or group may |
| 585 | not connect to the message bus.</para> |
| 586 | |
| 587 | |
| 588 | <para>For "name", "username", "groupname", etc. |
| 589 | the character "*" can be substituted, meaning "any." Complex globs |
| 590 | like "foo.bar.*" aren't allowed for now because they'd be work to |
| 591 | implement and maybe encourage sloppy security anyway.</para> |
| 592 | |
| 593 | |
| 594 | <para>It does not make sense to deny a user or group inside a <policy> |
| 595 | for a user or group; user/group denials can only be inside |
| 596 | context="default" or context="mandatory" policies.</para> |
| 597 | |
| 598 | |
| 599 | <para>A single <deny> rule may specify combinations of attributes such as |
| 600 | send_destination and send_interface and send_type. In this case, the |
| 601 | denial applies only if both attributes match the message being denied. |
| 602 | e.g. <deny send_interface="foo.bar" send_destination="foo.blah"/> would |
| 603 | deny messages with the given interface AND the given bus name. |
| 604 | To get an OR effect you specify multiple <deny> rules.</para> |
| 605 | |
| 606 | |
| 607 | <para>You can't include both send_ and receive_ attributes on the same |
| 608 | rule, since "whether the message can be sent" and "whether it can be |
| 609 | received" are evaluated separately.</para> |
| 610 | |
| 611 | |
| 612 | <para>Be careful with send_interface/receive_interface, because the |
| 613 | interface field in messages is optional.</para> |
| 614 | |
| 615 | <variablelist remap='TP'> |
| 616 | <varlistentry> |
| 617 | <term><emphasis remap='I'><selinux></emphasis></term> |
| 618 | <listitem> |
| 619 | |
| 620 | <para></para> <!-- FIXME: blank list item --> |
| 621 | </listitem> |
| 622 | </varlistentry> |
| 623 | </variablelist> |
| 624 | |
| 625 | <para>The <selinux> element contains settings related to Security Enhanced Linux. |
| 626 | More details below.</para> |
| 627 | |
| 628 | <variablelist remap='TP'> |
| 629 | <varlistentry> |
| 630 | <term><emphasis remap='I'><associate></emphasis></term> |
| 631 | <listitem> |
| 632 | |
| 633 | <para></para> <!-- FIXME: blank list item --> |
| 634 | </listitem> |
| 635 | </varlistentry> |
| 636 | </variablelist> |
| 637 | |
| 638 | <para>An <associate> element appears below an <selinux> element and |
| 639 | creates a mapping. Right now only one kind of association is possible:</para> |
| 640 | <literallayout remap='.nf'> |
| 641 | <associate own="org.freedesktop.Foobar" context="foo_t"/> |
| 642 | </literallayout> <!-- .fi --> |
| 643 | |
| 644 | |
| 645 | <para>This means that if a connection asks to own the name |
| 646 | "org.freedesktop.Foobar" then the source context will be the context |
| 647 | of the connection and the target context will be "foo_t" - see the |
| 648 | short discussion of SELinux below.</para> |
| 649 | |
| 650 | |
| 651 | <para>Note, the context here is the target context when requesting a name, |
| 652 | NOT the context of the connection owning the name.</para> |
| 653 | |
| 654 | |
| 655 | <para>There's currently no way to set a default for owning any name, if |
| 656 | we add this syntax it will look like:</para> |
| 657 | <literallayout remap='.nf'> |
| 658 | <associate own="*" context="foo_t"/> |
| 659 | </literallayout> <!-- .fi --> |
| 660 | <para>If you find a reason this is useful, let the developers know. |
| 661 | Right now the default will be the security context of the bus itself.</para> |
| 662 | |
| 663 | |
| 664 | <para>If two <associate> elements specify the same name, the element |
| 665 | appearing later in the configuration file will be used.</para> |
| 666 | |
| 667 | </refsect1> |
| 668 | |
| 669 | <refsect1 id='selinux'><title>SELinux</title> |
| 670 | <para>See <ulink url='http://www.nsa.gov/selinux/'>http://www.nsa.gov/selinux/</ulink> for full details on SELinux. Some useful excerpts:</para> |
| 671 | |
| 672 | |
| 673 | <para>Every subject (process) and object (e.g. file, socket, IPC object, |
| 674 | etc) in the system is assigned a collection of security attributes, |
| 675 | known as a security context. A security context contains all of the |
| 676 | security attributes associated with a particular subject or object |
| 677 | that are relevant to the security policy.</para> |
| 678 | |
| 679 | |
| 680 | <para>In order to better encapsulate security contexts and to provide |
| 681 | greater efficiency, the policy enforcement code of SELinux typically |
| 682 | handles security identifiers (SIDs) rather than security contexts. A |
| 683 | SID is an integer that is mapped by the security server to a security |
| 684 | context at runtime.</para> |
| 685 | |
| 686 | |
| 687 | <para>When a security decision is required, the policy enforcement code |
| 688 | passes a pair of SIDs (typically the SID of a subject and the SID of |
| 689 | an object, but sometimes a pair of subject SIDs or a pair of object |
| 690 | SIDs), and an object security class to the security server. The object |
| 691 | security class indicates the kind of object, e.g. a process, a regular |
| 692 | file, a directory, a TCP socket, etc.</para> |
| 693 | |
| 694 | |
| 695 | <para>Access decisions specify whether or not a permission is granted for a |
| 696 | given pair of SIDs and class. Each object class has a set of |
| 697 | associated permissions defined to control operations on objects with |
| 698 | that class.</para> |
| 699 | |
| 700 | |
| 701 | <para>D-Bus performs SELinux security checks in two places.</para> |
| 702 | |
| 703 | |
| 704 | <para>First, any time a message is routed from one connection to another |
| 705 | connection, the bus daemon will check permissions with the security context of |
| 706 | the first connection as source, security context of the second connection |
| 707 | as target, object class "dbus" and requested permission "send_msg".</para> |
| 708 | |
| 709 | |
| 710 | <para>If a security context is not available for a connection |
| 711 | (impossible when using UNIX domain sockets), then the target |
| 712 | context used is the context of the bus daemon itself. |
| 713 | There is currently no way to change this default, because we're |
| 714 | assuming that only UNIX domain sockets will be used to |
| 715 | connect to the systemwide bus. If this changes, we'll |
| 716 | probably add a way to set the default connection context.</para> |
| 717 | |
| 718 | |
| 719 | <para>Second, any time a connection asks to own a name, |
| 720 | the bus daemon will check permissions with the security |
| 721 | context of the connection as source, the security context specified |
| 722 | for the name in the config file as target, object |
| 723 | class "dbus" and requested permission "acquire_svc".</para> |
| 724 | |
| 725 | |
| 726 | <para>The security context for a bus name is specified with the |
| 727 | <associate> element described earlier in this document. |
| 728 | If a name has no security context associated in the |
| 729 | configuration file, the security context of the bus daemon |
| 730 | itself will be used.</para> |
| 731 | |
| 732 | </refsect1> |
| 733 | |
| 734 | <refsect1 id='author'><title>AUTHOR</title> |
| 735 | <para>See <ulink url='http://www.freedesktop.org/software/dbus/doc/AUTHORS'>http://www.freedesktop.org/software/dbus/doc/AUTHORS</ulink></para> |
| 736 | |
| 737 | </refsect1> |
| 738 | |
| 739 | <refsect1 id='bugs'><title>BUGS</title> |
| 740 | <para>Please send bug reports to the D-Bus mailing list or bug tracker, |
| 741 | see <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink></para> |
| 742 | </refsect1> |
| 743 | </refentry> |
| 744 | |