Based on kernel version 4.0. Page generated on 2015-04-14 21:26 EST.
1 2 3 "Good for you, you've decided to clean the elevator!" 4 - The Elevator, from Dark Star 5 6 Smack is the Simplified Mandatory Access Control Kernel. 7 Smack is a kernel based implementation of mandatory access 8 control that includes simplicity in its primary design goals. 9 10 Smack is not the only Mandatory Access Control scheme 11 available for Linux. Those new to Mandatory Access Control 12 are encouraged to compare Smack with the other mechanisms 13 available to determine which is best suited to the problem 14 at hand. 15 16 Smack consists of three major components: 17 - The kernel 18 - Basic utilities, which are helpful but not required 19 - Configuration data 20 21 The kernel component of Smack is implemented as a Linux 22 Security Modules (LSM) module. It requires netlabel and 23 works best with file systems that support extended attributes, 24 although xattr support is not strictly required. 25 It is safe to run a Smack kernel under a "vanilla" distribution. 26 27 Smack kernels use the CIPSO IP option. Some network 28 configurations are intolerant of IP options and can impede 29 access to systems that use them as Smack does. 30 31 The current git repository for Smack user space is: 32 33 git://github.com/smack-team/smack.git 34 35 This should make and install on most modern distributions. 36 There are three commands included in smackutil: 37 38 smackload - properly formats data for writing to /smack/load 39 smackcipso - properly formats data for writing to /smack/cipso 40 chsmack - display or set Smack extended attribute values 41 42 In keeping with the intent of Smack, configuration data is 43 minimal and not strictly required. The most important 44 configuration step is mounting the smackfs pseudo filesystem. 45 If smackutil is installed the startup script will take care 46 of this, but it can be manually as well. 47 48 Add this line to /etc/fstab: 49 50 smackfs /smack smackfs smackfsdef=* 0 0 51 52 and create the /smack directory for mounting. 53 54 Smack uses extended attributes (xattrs) to store labels on filesystem 55 objects. The attributes are stored in the extended attribute security 56 name space. A process must have CAP_MAC_ADMIN to change any of these 57 attributes. 58 59 The extended attributes that Smack uses are: 60 61 SMACK64 62 Used to make access control decisions. In almost all cases 63 the label given to a new filesystem object will be the label 64 of the process that created it. 65 SMACK64EXEC 66 The Smack label of a process that execs a program file with 67 this attribute set will run with this attribute's value. 68 SMACK64MMAP 69 Don't allow the file to be mmapped by a process whose Smack 70 label does not allow all of the access permitted to a process 71 with the label contained in this attribute. This is a very 72 specific use case for shared libraries. 73 SMACK64TRANSMUTE 74 Can only have the value "TRUE". If this attribute is present 75 on a directory when an object is created in the directory and 76 the Smack rule (more below) that permitted the write access 77 to the directory includes the transmute ("t") mode the object 78 gets the label of the directory instead of the label of the 79 creating process. If the object being created is a directory 80 the SMACK64TRANSMUTE attribute is set as well. 81 SMACK64IPIN 82 This attribute is only available on file descriptors for sockets. 83 Use the Smack label in this attribute for access control 84 decisions on packets being delivered to this socket. 85 SMACK64IPOUT 86 This attribute is only available on file descriptors for sockets. 87 Use the Smack label in this attribute for access control 88 decisions on packets coming from this socket. 89 90 There are multiple ways to set a Smack label on a file: 91 92 # attr -S -s SMACK64 -V "value" path 93 # chsmack -a value path 94 95 A process can see the smack label it is running with by 96 reading /proc/self/attr/current. A process with CAP_MAC_ADMIN 97 can set the process smack by writing there. 98 99 Most Smack configuration is accomplished by writing to files 100 in the smackfs filesystem. This pseudo-filesystem is usually 101 mounted on /smack. 102 103 access 104 This interface reports whether a subject with the specified 105 Smack label has a particular access to an object with a 106 specified Smack label. Write a fixed format access rule to 107 this file. The next read will indicate whether the access 108 would be permitted. The text will be either "1" indicating 109 access, or "0" indicating denial. 110 access2 111 This interface reports whether a subject with the specified 112 Smack label has a particular access to an object with a 113 specified Smack label. Write a long format access rule to 114 this file. The next read will indicate whether the access 115 would be permitted. The text will be either "1" indicating 116 access, or "0" indicating denial. 117 ambient 118 This contains the Smack label applied to unlabeled network 119 packets. 120 change-rule 121 This interface allows modification of existing access control rules. 122 The format accepted on write is: 123 "%s %s %s %s" 124 where the first string is the subject label, the second the 125 object label, the third the access to allow and the fourth the 126 access to deny. The access strings may contain only the characters 127 "rwxat-". If a rule for a given subject and object exists it will be 128 modified by enabling the permissions in the third string and disabling 129 those in the fourth string. If there is no such rule it will be 130 created using the access specified in the third and the fourth strings. 131 cipso 132 This interface allows a specific CIPSO header to be assigned 133 to a Smack label. The format accepted on write is: 134 "%24s%4d%4d"["%4d"]... 135 The first string is a fixed Smack label. The first number is 136 the level to use. The second number is the number of categories. 137 The following numbers are the categories. 138 "level-3-cats-5-19 3 2 5 19" 139 cipso2 140 This interface allows a specific CIPSO header to be assigned 141 to a Smack label. The format accepted on write is: 142 "%s%4d%4d"["%4d"]... 143 The first string is a long Smack label. The first number is 144 the level to use. The second number is the number of categories. 145 The following numbers are the categories. 146 "level-3-cats-5-19 3 2 5 19" 147 direct 148 This contains the CIPSO level used for Smack direct label 149 representation in network packets. 150 doi 151 This contains the CIPSO domain of interpretation used in 152 network packets. 153 load 154 This interface allows access control rules in addition to 155 the system defined rules to be specified. The format accepted 156 on write is: 157 "%24s%24s%5s" 158 where the first string is the subject label, the second the 159 object label, and the third the requested access. The access 160 string may contain only the characters "rwxat-", and specifies 161 which sort of access is allowed. The "-" is a placeholder for 162 permissions that are not allowed. The string "r-x--" would 163 specify read and execute access. Labels are limited to 23 164 characters in length. 165 load2 166 This interface allows access control rules in addition to 167 the system defined rules to be specified. The format accepted 168 on write is: 169 "%s %s %s" 170 where the first string is the subject label, the second the 171 object label, and the third the requested access. The access 172 string may contain only the characters "rwxat-", and specifies 173 which sort of access is allowed. The "-" is a placeholder for 174 permissions that are not allowed. The string "r-x--" would 175 specify read and execute access. 176 load-self 177 This interface allows process specific access rules to be 178 defined. These rules are only consulted if access would 179 otherwise be permitted, and are intended to provide additional 180 restrictions on the process. The format is the same as for 181 the load interface. 182 load-self2 183 This interface allows process specific access rules to be 184 defined. These rules are only consulted if access would 185 otherwise be permitted, and are intended to provide additional 186 restrictions on the process. The format is the same as for 187 the load2 interface. 188 logging 189 This contains the Smack logging state. 190 mapped 191 This contains the CIPSO level used for Smack mapped label 192 representation in network packets. 193 netlabel 194 This interface allows specific internet addresses to be 195 treated as single label hosts. Packets are sent to single 196 label hosts without CIPSO headers, but only from processes 197 that have Smack write access to the host label. All packets 198 received from single label hosts are given the specified 199 label. The format accepted on write is: 200 "%d.%d.%d.%d label" or "%d.%d.%d.%d/%d label". 201 onlycap 202 This contains the label processes must have for CAP_MAC_ADMIN 203 and CAP_MAC_OVERRIDE to be effective. If this file is empty 204 these capabilities are effective at for processes with any 205 label. The value is set by writing the desired label to the 206 file or cleared by writing "-" to the file. 207 ptrace 208 This is used to define the current ptrace policy 209 0 - default: this is the policy that relies on smack access rules. 210 For the PTRACE_READ a subject needs to have a read access on 211 object. For the PTRACE_ATTACH a read-write access is required. 212 1 - exact: this is the policy that limits PTRACE_ATTACH. Attach is 213 only allowed when subject's and object's labels are equal. 214 PTRACE_READ is not affected. Can be overriden with CAP_SYS_PTRACE. 215 2 - draconian: this policy behaves like the 'exact' above with an 216 exception that it can't be overriden with CAP_SYS_PTRACE. 217 revoke-subject 218 Writing a Smack label here sets the access to '-' for all access 219 rules with that subject label. 220 221 You can add access rules in /etc/smack/accesses. They take the form: 222 223 subjectlabel objectlabel access 224 225 access is a combination of the letters rwxa which specify the 226 kind of access permitted a subject with subjectlabel on an 227 object with objectlabel. If there is no rule no access is allowed. 228 229 Look for additional programs on http://schaufler-ca.com 230 231 From the Smack Whitepaper: 232 233 The Simplified Mandatory Access Control Kernel 234 235 Casey Schaufler 236 email@example.com 237 238 Mandatory Access Control 239 240 Computer systems employ a variety of schemes to constrain how information is 241 shared among the people and services using the machine. Some of these schemes 242 allow the program or user to decide what other programs or users are allowed 243 access to pieces of data. These schemes are called discretionary access 244 control mechanisms because the access control is specified at the discretion 245 of the user. Other schemes do not leave the decision regarding what a user or 246 program can access up to users or programs. These schemes are called mandatory 247 access control mechanisms because you don't have a choice regarding the users 248 or programs that have access to pieces of data. 249 250 Bell & LaPadula 251 252 From the middle of the 1980's until the turn of the century Mandatory Access 253 Control (MAC) was very closely associated with the Bell & LaPadula security 254 model, a mathematical description of the United States Department of Defense 255 policy for marking paper documents. MAC in this form enjoyed a following 256 within the Capital Beltway and Scandinavian supercomputer centers but was 257 often sited as failing to address general needs. 258 259 Domain Type Enforcement 260 261 Around the turn of the century Domain Type Enforcement (DTE) became popular. 262 This scheme organizes users, programs, and data into domains that are 263 protected from each other. This scheme has been widely deployed as a component 264 of popular Linux distributions. The administrative overhead required to 265 maintain this scheme and the detailed understanding of the whole system 266 necessary to provide a secure domain mapping leads to the scheme being 267 disabled or used in limited ways in the majority of cases. 268 269 Smack 270 271 Smack is a Mandatory Access Control mechanism designed to provide useful MAC 272 while avoiding the pitfalls of its predecessors. The limitations of Bell & 273 LaPadula are addressed by providing a scheme whereby access can be controlled 274 according to the requirements of the system and its purpose rather than those 275 imposed by an arcane government policy. The complexity of Domain Type 276 Enforcement and avoided by defining access controls in terms of the access 277 modes already in use. 278 279 Smack Terminology 280 281 The jargon used to talk about Smack will be familiar to those who have dealt 282 with other MAC systems and shouldn't be too difficult for the uninitiated to 283 pick up. There are four terms that are used in a specific way and that are 284 especially important: 285 286 Subject: A subject is an active entity on the computer system. 287 On Smack a subject is a task, which is in turn the basic unit 288 of execution. 289 290 Object: An object is a passive entity on the computer system. 291 On Smack files of all types, IPC, and tasks can be objects. 292 293 Access: Any attempt by a subject to put information into or get 294 information from an object is an access. 295 296 Label: Data that identifies the Mandatory Access Control 297 characteristics of a subject or an object. 298 299 These definitions are consistent with the traditional use in the security 300 community. There are also some terms from Linux that are likely to crop up: 301 302 Capability: A task that possesses a capability has permission to 303 violate an aspect of the system security policy, as identified by 304 the specific capability. A task that possesses one or more 305 capabilities is a privileged task, whereas a task with no 306 capabilities is an unprivileged task. 307 308 Privilege: A task that is allowed to violate the system security 309 policy is said to have privilege. As of this writing a task can 310 have privilege either by possessing capabilities or by having an 311 effective user of root. 312 313 Smack Basics 314 315 Smack is an extension to a Linux system. It enforces additional restrictions 316 on what subjects can access which objects, based on the labels attached to 317 each of the subject and the object. 318 319 Labels 320 321 Smack labels are ASCII character strings, one to twenty-three characters in 322 length. Single character labels using special characters, that being anything 323 other than a letter or digit, are reserved for use by the Smack development 324 team. Smack labels are unstructured, case sensitive, and the only operation 325 ever performed on them is comparison for equality. Smack labels cannot 326 contain unprintable characters, the "/" (slash), the "\" (backslash), the "'" 327 (quote) and '"' (double-quote) characters. 328 Smack labels cannot begin with a '-'. This is reserved for special options. 329 330 There are some predefined labels: 331 332 _ Pronounced "floor", a single underscore character. 333 ^ Pronounced "hat", a single circumflex character. 334 * Pronounced "star", a single asterisk character. 335 ? Pronounced "huh", a single question mark character. 336 @ Pronounced "web", a single at sign character. 337 338 Every task on a Smack system is assigned a label. System tasks, such as 339 init(8) and systems daemons, are run with the floor ("_") label. User tasks 340 are assigned labels according to the specification found in the 341 /etc/smack/user configuration file. 342 343 Access Rules 344 345 Smack uses the traditional access modes of Linux. These modes are read, 346 execute, write, and occasionally append. There are a few cases where the 347 access mode may not be obvious. These include: 348 349 Signals: A signal is a write operation from the subject task to 350 the object task. 351 Internet Domain IPC: Transmission of a packet is considered a 352 write operation from the source task to the destination task. 353 354 Smack restricts access based on the label attached to a subject and the label 355 attached to the object it is trying to access. The rules enforced are, in 356 order: 357 358 1. Any access requested by a task labeled "*" is denied. 359 2. A read or execute access requested by a task labeled "^" 360 is permitted. 361 3. A read or execute access requested on an object labeled "_" 362 is permitted. 363 4. Any access requested on an object labeled "*" is permitted. 364 5. Any access requested by a task on an object with the same 365 label is permitted. 366 6. Any access requested that is explicitly defined in the loaded 367 rule set is permitted. 368 7. Any other access is denied. 369 370 Smack Access Rules 371 372 With the isolation provided by Smack access separation is simple. There are 373 many interesting cases where limited access by subjects to objects with 374 different labels is desired. One example is the familiar spy model of 375 sensitivity, where a scientist working on a highly classified project would be 376 able to read documents of lower classifications and anything she writes will 377 be "born" highly classified. To accommodate such schemes Smack includes a 378 mechanism for specifying rules allowing access between labels. 379 380 Access Rule Format 381 382 The format of an access rule is: 383 384 subject-label object-label access 385 386 Where subject-label is the Smack label of the task, object-label is the Smack 387 label of the thing being accessed, and access is a string specifying the sort 388 of access allowed. The access specification is searched for letters that 389 describe access modes: 390 391 a: indicates that append access should be granted. 392 r: indicates that read access should be granted. 393 w: indicates that write access should be granted. 394 x: indicates that execute access should be granted. 395 t: indicates that the rule requests transmutation. 396 397 Uppercase values for the specification letters are allowed as well. 398 Access mode specifications can be in any order. Examples of acceptable rules 399 are: 400 401 TopSecret Secret rx 402 Secret Unclass R 403 Manager Game x 404 User HR w 405 New Old rRrRr 406 Closed Off - 407 408 Examples of unacceptable rules are: 409 410 Top Secret Secret rx 411 Ace Ace r 412 Odd spells waxbeans 413 414 Spaces are not allowed in labels. Since a subject always has access to files 415 with the same label specifying a rule for that case is pointless. Only 416 valid letters (rwxatRWXAT) and the dash ('-') character are allowed in 417 access specifications. The dash is a placeholder, so "a-r" is the same 418 as "ar". A lone dash is used to specify that no access should be allowed. 419 420 Applying Access Rules 421 422 The developers of Linux rarely define new sorts of things, usually importing 423 schemes and concepts from other systems. Most often, the other systems are 424 variants of Unix. Unix has many endearing properties, but consistency of 425 access control models is not one of them. Smack strives to treat accesses as 426 uniformly as is sensible while keeping with the spirit of the underlying 427 mechanism. 428 429 File system objects including files, directories, named pipes, symbolic links, 430 and devices require access permissions that closely match those used by mode 431 bit access. To open a file for reading read access is required on the file. To 432 search a directory requires execute access. Creating a file with write access 433 requires both read and write access on the containing directory. Deleting a 434 file requires read and write access to the file and to the containing 435 directory. It is possible that a user may be able to see that a file exists 436 but not any of its attributes by the circumstance of having read access to the 437 containing directory but not to the differently labeled file. This is an 438 artifact of the file name being data in the directory, not a part of the file. 439 440 If a directory is marked as transmuting (SMACK64TRANSMUTE=TRUE) and the 441 access rule that allows a process to create an object in that directory 442 includes 't' access the label assigned to the new object will be that 443 of the directory, not the creating process. This makes it much easier 444 for two processes with different labels to share data without granting 445 access to all of their files. 446 447 IPC objects, message queues, semaphore sets, and memory segments exist in flat 448 namespaces and access requests are only required to match the object in 449 question. 450 451 Process objects reflect tasks on the system and the Smack label used to access 452 them is the same Smack label that the task would use for its own access 453 attempts. Sending a signal via the kill() system call is a write operation 454 from the signaler to the recipient. Debugging a process requires both reading 455 and writing. Creating a new task is an internal operation that results in two 456 tasks with identical Smack labels and requires no access checks. 457 458 Sockets are data structures attached to processes and sending a packet from 459 one process to another requires that the sender have write access to the 460 receiver. The receiver is not required to have read access to the sender. 461 462 Setting Access Rules 463 464 The configuration file /etc/smack/accesses contains the rules to be set at 465 system startup. The contents are written to the special file /smack/load. 466 Rules can be written to /smack/load at any time and take effect immediately. 467 For any pair of subject and object labels there can be only one rule, with the 468 most recently specified overriding any earlier specification. 469 470 The program smackload is provided to ensure data is formatted 471 properly when written to /smack/load. This program reads lines 472 of the form 473 474 subjectlabel objectlabel mode. 475 476 Task Attribute 477 478 The Smack label of a process can be read from /proc/<pid>/attr/current. A 479 process can read its own Smack label from /proc/self/attr/current. A 480 privileged process can change its own Smack label by writing to 481 /proc/self/attr/current but not the label of another process. 482 483 File Attribute 484 485 The Smack label of a filesystem object is stored as an extended attribute 486 named SMACK64 on the file. This attribute is in the security namespace. It can 487 only be changed by a process with privilege. 488 489 Privilege 490 491 A process with CAP_MAC_OVERRIDE is privileged. 492 493 Smack Networking 494 495 As mentioned before, Smack enforces access control on network protocol 496 transmissions. Every packet sent by a Smack process is tagged with its Smack 497 label. This is done by adding a CIPSO tag to the header of the IP packet. Each 498 packet received is expected to have a CIPSO tag that identifies the label and 499 if it lacks such a tag the network ambient label is assumed. Before the packet 500 is delivered a check is made to determine that a subject with the label on the 501 packet has write access to the receiving process and if that is not the case 502 the packet is dropped. 503 504 CIPSO Configuration 505 506 It is normally unnecessary to specify the CIPSO configuration. The default 507 values used by the system handle all internal cases. Smack will compose CIPSO 508 label values to match the Smack labels being used without administrative 509 intervention. Unlabeled packets that come into the system will be given the 510 ambient label. 511 512 Smack requires configuration in the case where packets from a system that is 513 not smack that speaks CIPSO may be encountered. Usually this will be a Trusted 514 Solaris system, but there are other, less widely deployed systems out there. 515 CIPSO provides 3 important values, a Domain Of Interpretation (DOI), a level, 516 and a category set with each packet. The DOI is intended to identify a group 517 of systems that use compatible labeling schemes, and the DOI specified on the 518 smack system must match that of the remote system or packets will be 519 discarded. The DOI is 3 by default. The value can be read from /smack/doi and 520 can be changed by writing to /smack/doi. 521 522 The label and category set are mapped to a Smack label as defined in 523 /etc/smack/cipso. 524 525 A Smack/CIPSO mapping has the form: 526 527 smack level [category [category]*] 528 529 Smack does not expect the level or category sets to be related in any 530 particular way and does not assume or assign accesses based on them. Some 531 examples of mappings: 532 533 TopSecret 7 534 TS:A,B 7 1 2 535 SecBDE 5 2 4 6 536 RAFTERS 7 12 26 537 538 The ":" and "," characters are permitted in a Smack label but have no special 539 meaning. 540 541 The mapping of Smack labels to CIPSO values is defined by writing to 542 /smack/cipso. Again, the format of data written to this special file 543 is highly restrictive, so the program smackcipso is provided to 544 ensure the writes are done properly. This program takes mappings 545 on the standard input and sends them to /smack/cipso properly. 546 547 In addition to explicit mappings Smack supports direct CIPSO mappings. One 548 CIPSO level is used to indicate that the category set passed in the packet is 549 in fact an encoding of the Smack label. The level used is 250 by default. The 550 value can be read from /smack/direct and changed by writing to /smack/direct. 551 552 Socket Attributes 553 554 There are two attributes that are associated with sockets. These attributes 555 can only be set by privileged tasks, but any task can read them for their own 556 sockets. 557 558 SMACK64IPIN: The Smack label of the task object. A privileged 559 program that will enforce policy may set this to the star label. 560 561 SMACK64IPOUT: The Smack label transmitted with outgoing packets. 562 A privileged program may set this to match the label of another 563 task with which it hopes to communicate. 564 565 Smack Netlabel Exceptions 566 567 You will often find that your labeled application has to talk to the outside, 568 unlabeled world. To do this there's a special file /smack/netlabel where you can 569 add some exceptions in the form of : 570 @IP1 LABEL1 or 571 @IP2/MASK LABEL2 572 573 It means that your application will have unlabeled access to @IP1 if it has 574 write access on LABEL1, and access to the subnet @IP2/MASK if it has write 575 access on LABEL2. 576 577 Entries in the /smack/netlabel file are matched by longest mask first, like in 578 classless IPv4 routing. 579 580 A special label '@' and an option '-CIPSO' can be used there : 581 @ means Internet, any application with any label has access to it 582 -CIPSO means standard CIPSO networking 583 584 If you don't know what CIPSO is and don't plan to use it, you can just do : 585 echo 127.0.0.1 -CIPSO > /smack/netlabel 586 echo 0.0.0.0/0 @ > /smack/netlabel 587 588 If you use CIPSO on your 192.168.0.0/16 local network and need also unlabeled 589 Internet access, you can have : 590 echo 127.0.0.1 -CIPSO > /smack/netlabel 591 echo 192.168.0.0/16 -CIPSO > /smack/netlabel 592 echo 0.0.0.0/0 @ > /smack/netlabel 593 594 595 Writing Applications for Smack 596 597 There are three sorts of applications that will run on a Smack system. How an 598 application interacts with Smack will determine what it will have to do to 599 work properly under Smack. 600 601 Smack Ignorant Applications 602 603 By far the majority of applications have no reason whatever to care about the 604 unique properties of Smack. Since invoking a program has no impact on the 605 Smack label associated with the process the only concern likely to arise is 606 whether the process has execute access to the program. 607 608 Smack Relevant Applications 609 610 Some programs can be improved by teaching them about Smack, but do not make 611 any security decisions themselves. The utility ls(1) is one example of such a 612 program. 613 614 Smack Enforcing Applications 615 616 These are special programs that not only know about Smack, but participate in 617 the enforcement of system policy. In most cases these are the programs that 618 set up user sessions. There are also network services that provide information 619 to processes running with various labels. 620 621 File System Interfaces 622 623 Smack maintains labels on file system objects using extended attributes. The 624 Smack label of a file, directory, or other file system object can be obtained 625 using getxattr(2). 626 627 len = getxattr("/", "security.SMACK64", value, sizeof (value)); 628 629 will put the Smack label of the root directory into value. A privileged 630 process can set the Smack label of a file system object with setxattr(2). 631 632 len = strlen("Rubble"); 633 rc = setxattr("/foo", "security.SMACK64", "Rubble", len, 0); 634 635 will set the Smack label of /foo to "Rubble" if the program has appropriate 636 privilege. 637 638 Socket Interfaces 639 640 The socket attributes can be read using fgetxattr(2). 641 642 A privileged process can set the Smack label of outgoing packets with 643 fsetxattr(2). 644 645 len = strlen("Rubble"); 646 rc = fsetxattr(fd, "security.SMACK64IPOUT", "Rubble", len, 0); 647 648 will set the Smack label "Rubble" on packets going out from the socket if the 649 program has appropriate privilege. 650 651 rc = fsetxattr(fd, "security.SMACK64IPIN, "*", strlen("*"), 0); 652 653 will set the Smack label "*" as the object label against which incoming 654 packets will be checked if the program has appropriate privilege. 655 656 Administration 657 658 Smack supports some mount options: 659 660 smackfsdef=label: specifies the label to give files that lack 661 the Smack label extended attribute. 662 663 smackfsroot=label: specifies the label to assign the root of the 664 file system if it lacks the Smack extended attribute. 665 666 smackfshat=label: specifies a label that must have read access to 667 all labels set on the filesystem. Not yet enforced. 668 669 smackfsfloor=label: specifies a label to which all labels set on the 670 filesystem must have read access. Not yet enforced. 671 672 These mount options apply to all file system types. 673 674 Smack auditing 675 676 If you want Smack auditing of security events, you need to set CONFIG_AUDIT 677 in your kernel configuration. 678 By default, all denied events will be audited. You can change this behavior by 679 writing a single character to the /smack/logging file : 680 0 : no logging 681 1 : log denied (default) 682 2 : log accepted 683 3 : log denied & accepted 684 685 Events are logged as 'key=value' pairs, for each event you at least will get 686 the subject, the object, the rights requested, the action, the kernel function 687 that triggered the event, plus other pairs depending on the type of event 688 audited.