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 own_prefix="name" 516 user="username" 517 group="groupname" 518 </literallayout> <!-- .fi --> 519 520 521 <para>Examples:</para> 522 <literallayout remap='.nf'> 523 <deny send_interface="org.freedesktop.System" send_member="Reboot"/> 524 <deny receive_interface="org.freedesktop.System" receive_member="Reboot"/> 525 <deny own="org.freedesktop.System"/> 526 <deny send_destination="org.freedesktop.System"/> 527 <deny receive_sender="org.freedesktop.System"/> 528 <deny user="john"/> 529 <deny group="enemies"/> 530 </literallayout> <!-- .fi --> 531 532 533 <para>The <deny> element's attributes determine whether the deny "matches" a 534 particular action. If it matches, the action is denied (unless later 535 rules in the config file allow it).</para> 536 537 538 <para>send_destination and receive_sender rules mean that messages may not be 539 sent to or received from the *owner* of the given name, not that 540 they may not be sent *to that name*. That is, if a connection 541 owns services A, B, C, and sending to A is denied, sending to B or C 542 will not work either.</para> 543 544 545 <para>The other send_* and receive_* attributes are purely textual/by-value 546 matches against the given field in the message header.</para> 547 548 549 <para>"Eavesdropping" occurs when an application receives a message that 550 was explicitly addressed to a name the application does not own. 551 Eavesdropping thus only applies to messages that are addressed to 552 services (i.e. it does not apply to signals).</para> 553 554 555 <para>For <allow>, eavesdrop="true" indicates that the rule matches even 556 when eavesdropping. eavesdrop="false" is the default and means that 557 the rule only allows messages to go to their specified recipient. 558 For <deny>, eavesdrop="true" indicates that the rule matches 559 only when eavesdropping. eavesdrop="false" is the default for <deny> 560 also, but here it means that the rule applies always, even when 561 not eavesdropping. The eavesdrop attribute can only be combined with 562 receive rules (with receive_* attributes).</para> 563 564 565 566 <para>The [send|receive]_requested_reply attribute works similarly to the eavesdrop 567 attribute. It controls whether the <deny> or <allow> matches a reply 568 that is expected (corresponds to a previous method call message). 569 This attribute only makes sense for reply messages (errors and method 570 returns), and is ignored for other message types.</para> 571 572 573 <para>For <allow>, [send|receive]_requested_reply="true" is the default and indicates that 574 only requested replies are allowed by the 575 rule. [send|receive]_requested_reply="false" means that the rule allows any reply 576 even if unexpected.</para> 577 578 579 <para>For <deny>, [send|receive]_requested_reply="false" is the default but indicates that 580 the rule matches only when the reply was not 581 requested. [send|receive]_requested_reply="true" indicates that the rule applies 582 always, regardless of pending reply state.</para> 583 584 585 <para>user and group denials mean that the given user or group may 586 not connect to the message bus.</para> 587 588 589 <para>For "name", "username", "groupname", etc. 590 the character "*" can be substituted, meaning "any." Complex globs 591 like "foo.bar.*" aren't allowed for now because they'd be work to 592 implement and maybe encourage sloppy security anyway.</para> 593 594 <para><allow own_prefix="a.b"/> allows you to own the name "a.b" or any 595 name whose first dot-separated elements are "a.b": in particular, 596 you can own "a.b.c" or "a.b.c.d", but not "a.bc" or "a.c". 597 This is useful when services like Telepathy and ReserveDevice 598 define a meaning for subtrees of well-known names, such as 599 org.freedesktop.Telepathy.ConnectionManager.(anything) 600 and org.freedesktop.ReserveDevice1.(anything).</para> 601 602 <para>It does not make sense to deny a user or group inside a <policy> 603 for a user or group; user/group denials can only be inside 604 context="default" or context="mandatory" policies.</para> 605 606 607 <para>A single <deny> rule may specify combinations of attributes such as 608 send_destination and send_interface and send_type. In this case, the 609 denial applies only if both attributes match the message being denied. 610 e.g. <deny send_interface="foo.bar" send_destination="foo.blah"/> would 611 deny messages with the given interface AND the given bus name. 612 To get an OR effect you specify multiple <deny> rules.</para> 613 614 615 <para>You can't include both send_ and receive_ attributes on the same 616 rule, since "whether the message can be sent" and "whether it can be 617 received" are evaluated separately.</para> 618 619 620 <para>Be careful with send_interface/receive_interface, because the 621 interface field in messages is optional.</para> 622 623 <variablelist remap='TP'> 624 <varlistentry> 625 <term><emphasis remap='I'><selinux></emphasis></term> 626 <listitem> 627 628 <para></para> <!-- FIXME: blank list item --> 629 </listitem> 630 </varlistentry> 631 </variablelist> 632 633 <para>The <selinux> element contains settings related to Security Enhanced Linux. 634 More details below.</para> 635 636 <variablelist remap='TP'> 637 <varlistentry> 638 <term><emphasis remap='I'><associate></emphasis></term> 639 <listitem> 640 641 <para></para> <!-- FIXME: blank list item --> 642 </listitem> 643 </varlistentry> 644 </variablelist> 645 646 <para>An <associate> element appears below an <selinux> element and 647 creates a mapping. Right now only one kind of association is possible:</para> 648 <literallayout remap='.nf'> 649 <associate own="org.freedesktop.Foobar" context="foo_t"/> 650 </literallayout> <!-- .fi --> 651 652 653 <para>This means that if a connection asks to own the name 654 "org.freedesktop.Foobar" then the source context will be the context 655 of the connection and the target context will be "foo_t" - see the 656 short discussion of SELinux below.</para> 657 658 659 <para>Note, the context here is the target context when requesting a name, 660 NOT the context of the connection owning the name.</para> 661 662 663 <para>There's currently no way to set a default for owning any name, if 664 we add this syntax it will look like:</para> 665 <literallayout remap='.nf'> 666 <associate own="*" context="foo_t"/> 667 </literallayout> <!-- .fi --> 668 <para>If you find a reason this is useful, let the developers know. 669 Right now the default will be the security context of the bus itself.</para> 670 671 672 <para>If two <associate> elements specify the same name, the element 673 appearing later in the configuration file will be used.</para> 674 675 </refsect1> 676 677 <refsect1 id='selinux'><title>SELinux</title> 678 <para>See <ulink url='http://www.nsa.gov/selinux/'>http://www.nsa.gov/selinux/</ulink> for full details on SELinux. Some useful excerpts:</para> 679 680 681 <para>Every subject (process) and object (e.g. file, socket, IPC object, 682 etc) in the system is assigned a collection of security attributes, 683 known as a security context. A security context contains all of the 684 security attributes associated with a particular subject or object 685 that are relevant to the security policy.</para> 686 687 688 <para>In order to better encapsulate security contexts and to provide 689 greater efficiency, the policy enforcement code of SELinux typically 690 handles security identifiers (SIDs) rather than security contexts. A 691 SID is an integer that is mapped by the security server to a security 692 context at runtime.</para> 693 694 695 <para>When a security decision is required, the policy enforcement code 696 passes a pair of SIDs (typically the SID of a subject and the SID of 697 an object, but sometimes a pair of subject SIDs or a pair of object 698 SIDs), and an object security class to the security server. The object 699 security class indicates the kind of object, e.g. a process, a regular 700 file, a directory, a TCP socket, etc.</para> 701 702 703 <para>Access decisions specify whether or not a permission is granted for a 704 given pair of SIDs and class. Each object class has a set of 705 associated permissions defined to control operations on objects with 706 that class.</para> 707 708 709 <para>D-Bus performs SELinux security checks in two places.</para> 710 711 712 <para>First, any time a message is routed from one connection to another 713 connection, the bus daemon will check permissions with the security context of 714 the first connection as source, security context of the second connection 715 as target, object class "dbus" and requested permission "send_msg".</para> 716 717 718 <para>If a security context is not available for a connection 719 (impossible when using UNIX domain sockets), then the target 720 context used is the context of the bus daemon itself. 721 There is currently no way to change this default, because we're 722 assuming that only UNIX domain sockets will be used to 723 connect to the systemwide bus. If this changes, we'll 724 probably add a way to set the default connection context.</para> 725 726 727 <para>Second, any time a connection asks to own a name, 728 the bus daemon will check permissions with the security 729 context of the connection as source, the security context specified 730 for the name in the config file as target, object 731 class "dbus" and requested permission "acquire_svc".</para> 732 733 734 <para>The security context for a bus name is specified with the 735 <associate> element described earlier in this document. 736 If a name has no security context associated in the 737 configuration file, the security context of the bus daemon 738 itself will be used.</para> 739 740 </refsect1> 741 742 <refsect1 id='author'><title>AUTHOR</title> 743 <para>See <ulink url='http://www.freedesktop.org/software/dbus/doc/AUTHORS'>http://www.freedesktop.org/software/dbus/doc/AUTHORS</ulink></para> 744 745 </refsect1> 746 747 <refsect1 id='bugs'><title>BUGS</title> 748 <para>Please send bug reports to the D-Bus mailing list or bug tracker, 749 see <ulink url='http://www.freedesktop.org/software/dbus/'>http://www.freedesktop.org/software/dbus/</ulink></para> 750 </refsect1> 751 </refentry> 752 753