aboutsummaryrefslogtreecommitdiffstats
path: root/vendor/sabre/dav/lib/DAVACL/Plugin.php
blob: 601dffeccf86fc1f6d7d3f7270a0f411aafc780f (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
<?php

namespace Sabre\DAVACL;

use Sabre\DAV;
use Sabre\DAV\INode;
use Sabre\DAV\Exception\BadRequest;
use Sabre\HTTP\RequestInterface;
use Sabre\HTTP\ResponseInterface;
use Sabre\Uri;

/**
 * SabreDAV ACL Plugin
 *
 * This plugin provides functionality to enforce ACL permissions.
 * ACL is defined in RFC3744.
 *
 * In addition it also provides support for the {DAV:}current-user-principal
 * property, defined in RFC5397 and the {DAV:}expand-property report, as
 * defined in RFC3253.
 *
 * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
 * @author Evert Pot (http://evertpot.com/)
 * @license http://sabre.io/license/ Modified BSD License
 */
class Plugin extends DAV\ServerPlugin {

    /**
     * Recursion constants
     *
     * This only checks the base node
     */
    const R_PARENT = 1;

    /**
     * Recursion constants
     *
     * This checks every node in the tree
     */
    const R_RECURSIVE = 2;

    /**
     * Recursion constants
     *
     * This checks every parentnode in the tree, but not leaf-nodes.
     */
    const R_RECURSIVEPARENTS = 3;

    /**
     * Reference to server object.
     *
     * @var Sabre\DAV\Server
     */
    protected $server;

    /**
     * List of urls containing principal collections.
     * Modify this if your principals are located elsewhere.
     *
     * @var array
     */
    public $principalCollectionSet = [
        'principals',
    ];

    /**
     * By default ACL is only enforced for nodes that have ACL support (the
     * ones that implement IACL). For any other node, access is
     * always granted.
     *
     * To override this behaviour you can turn this setting off. This is useful
     * if you plan to fully support ACL in the entire tree.
     *
     * @var bool
     */
    public $allowAccessToNodesWithoutACL = true;

    /**
     * By default nodes that are inaccessible by the user, can still be seen
     * in directory listings (PROPFIND on parent with Depth: 1)
     *
     * In certain cases it's desirable to hide inaccessible nodes. Setting this
     * to true will cause these nodes to be hidden from directory listings.
     *
     * @var bool
     */
    public $hideNodesFromListings = false;

    /**
     * This list of properties are the properties a client can search on using
     * the {DAV:}principal-property-search report.
     *
     * The keys are the property names, values are descriptions.
     *
     * @var array
     */
    public $principalSearchPropertySet = [
        '{DAV:}displayname'                     => 'Display name',
        '{http://sabredav.org/ns}email-address' => 'Email address',
    ];

    /**
     * Any principal uri's added here, will automatically be added to the list
     * of ACL's. They will effectively receive {DAV:}all privileges, as a
     * protected privilege.
     *
     * @var array
     */
    public $adminPrincipals = [];

    /**
     * Returns a list of features added by this plugin.
     *
     * This list is used in the response of a HTTP OPTIONS request.
     *
     * @return array
     */
    function getFeatures() {

        return ['access-control', 'calendarserver-principal-property-search'];

    }

    /**
     * Returns a list of available methods for a given url
     *
     * @param string $uri
     * @return array
     */
    function getMethods($uri) {

        return ['ACL'];

    }

    /**
     * Returns a plugin name.
     *
     * Using this name other plugins will be able to access other plugins
     * using Sabre\DAV\Server::getPlugin
     *
     * @return string
     */
    function getPluginName() {

        return 'acl';

    }

    /**
     * Returns a list of reports this plugin supports.
     *
     * This will be used in the {DAV:}supported-report-set property.
     * Note that you still need to subscribe to the 'report' event to actually
     * implement them
     *
     * @param string $uri
     * @return array
     */
    function getSupportedReportSet($uri) {

        return [
            '{DAV:}expand-property',
            '{DAV:}principal-property-search',
            '{DAV:}principal-search-property-set',
        ];

    }


    /**
     * Checks if the current user has the specified privilege(s).
     *
     * You can specify a single privilege, or a list of privileges.
     * This method will throw an exception if the privilege is not available
     * and return true otherwise.
     *
     * @param string $uri
     * @param array|string $privileges
     * @param int $recursion
     * @param bool $throwExceptions if set to false, this method won't throw exceptions.
     * @throws Sabre\DAVACL\Exception\NeedPrivileges
     * @return bool
     */
    function checkPrivileges($uri, $privileges, $recursion = self::R_PARENT, $throwExceptions = true) {

        if (!is_array($privileges)) $privileges = [$privileges];

        $acl = $this->getCurrentUserPrivilegeSet($uri);

        if (is_null($acl)) {
            if ($this->allowAccessToNodesWithoutACL) {
                return true;
            } else {
                if ($throwExceptions)
                    throw new Exception\NeedPrivileges($uri, $privileges);
                else
                    return false;

            }
        }

        $failed = [];
        foreach ($privileges as $priv) {

            if (!in_array($priv, $acl)) {
                $failed[] = $priv;
            }

        }

        if ($failed) {
            if ($throwExceptions)
                throw new Exception\NeedPrivileges($uri, $failed);
            else
                return false;
        }
        return true;

    }

    /**
     * Returns the standard users' principal.
     *
     * This is one authorative principal url for the current user.
     * This method will return null if the user wasn't logged in.
     *
     * @return string|null
     */
    function getCurrentUserPrincipal() {

        $authPlugin = $this->server->getPlugin('auth');
        if (is_null($authPlugin)) return null;
        /** @var $authPlugin Sabre\DAV\Auth\Plugin */

        return $authPlugin->getCurrentPrincipal();

    }


    /**
     * Returns a list of principals that's associated to the current
     * user, either directly or through group membership.
     *
     * @return array
     */
    function getCurrentUserPrincipals() {

        $currentUser = $this->getCurrentUserPrincipal();

        if (is_null($currentUser)) return [];

        return array_merge(
            [$currentUser],
            $this->getPrincipalMembership($currentUser)
        );

    }

    /**
     * This array holds a cache for all the principals that are associated with
     * a single principal.
     *
     * @var array
     */
    protected $principalMembershipCache = [];


    /**
     * Returns all the principal groups the specified principal is a member of.
     *
     * @param string $principal
     * @return array
     */
    function getPrincipalMembership($mainPrincipal) {

        // First check our cache
        if (isset($this->principalMembershipCache[$mainPrincipal])) {
            return $this->principalMembershipCache[$mainPrincipal];
        }

        $check = [$mainPrincipal];
        $principals = [];

        while (count($check)) {

            $principal = array_shift($check);

            $node = $this->server->tree->getNodeForPath($principal);
            if ($node instanceof IPrincipal) {
                foreach ($node->getGroupMembership() as $groupMember) {

                    if (!in_array($groupMember, $principals)) {

                        $check[] = $groupMember;
                        $principals[] = $groupMember;

                    }

                }

            }

        }

        // Store the result in the cache
        $this->principalMembershipCache[$mainPrincipal] = $principals;

        return $principals;

    }

    /**
     * Returns the supported privilege structure for this ACL plugin.
     *
     * See RFC3744 for more details. Currently we default on a simple,
     * standard structure.
     *
     * You can either get the list of privileges by a uri (path) or by
     * specifying a Node.
     *
     * @param string|INode $node
     * @return array
     */
    function getSupportedPrivilegeSet($node) {

        if (is_string($node)) {
            $node = $this->server->tree->getNodeForPath($node);
        }

        if ($node instanceof IACL) {
            $result = $node->getSupportedPrivilegeSet();

            if ($result)
                return $result;
        }

        return self::getDefaultSupportedPrivilegeSet();

    }

    /**
     * Returns a fairly standard set of privileges, which may be useful for
     * other systems to use as a basis.
     *
     * @return array
     */
    static function getDefaultSupportedPrivilegeSet() {

        return [
            'privilege'  => '{DAV:}all',
            'abstract'   => true,
            'aggregates' => [
                [
                    'privilege'  => '{DAV:}read',
                    'aggregates' => [
                        [
                            'privilege' => '{DAV:}read-acl',
                            'abstract'  => false,
                        ],
                        [
                            'privilege' => '{DAV:}read-current-user-privilege-set',
                            'abstract'  => false,
                        ],
                    ],
                ], // {DAV:}read
                [
                    'privilege'  => '{DAV:}write',
                    'aggregates' => [
                        [
                            'privilege' => '{DAV:}write-acl',
                            'abstract'  => false,
                        ],
                        [
                            'privilege' => '{DAV:}write-properties',
                            'abstract'  => false,
                        ],
                        [
                            'privilege' => '{DAV:}write-content',
                            'abstract'  => false,
                        ],
                        [
                            'privilege' => '{DAV:}bind',
                            'abstract'  => false,
                        ],
                        [
                            'privilege' => '{DAV:}unbind',
                            'abstract'  => false,
                        ],
                        [
                            'privilege' => '{DAV:}unlock',
                            'abstract'  => false,
                        ],
                    ],
                ], // {DAV:}write
            ],
        ]; // {DAV:}all

    }

    /**
     * Returns the supported privilege set as a flat list
     *
     * This is much easier to parse.
     *
     * The returned list will be index by privilege name.
     * The value is a struct containing the following properties:
     *   - aggregates
     *   - abstract
     *   - concrete
     *
     * @param string|INode $node
     * @return array
     */
    final function getFlatPrivilegeSet($node) {

        $privs = $this->getSupportedPrivilegeSet($node);

        $fpsTraverse = null;
        $fpsTraverse = function($priv, $concrete, &$flat) use (&$fpsTraverse) {

            $myPriv = [
                'privilege'  => $priv['privilege'],
                'abstract'   => isset($priv['abstract']) && $priv['abstract'],
                'aggregates' => [],
                'concrete'   => isset($priv['abstract']) && $priv['abstract'] ? $concrete : $priv['privilege'],
            ];

            if (isset($priv['aggregates'])) {

                foreach ($priv['aggregates'] as $subPriv) {

                    $myPriv['aggregates'][] = $subPriv['privilege'];

                }

            }

            $flat[$priv['privilege']] = $myPriv;

            if (isset($priv['aggregates'])) {

                foreach ($priv['aggregates'] as $subPriv) {

                    $fpsTraverse($subPriv, $myPriv['concrete'], $flat);

                }

            }

        };

        $flat = [];
        $fpsTraverse($privs, null, $flat);

        return $flat;

    }

    /**
     * Returns the full ACL list.
     *
     * Either a uri or a INode may be passed.
     *
     * null will be returned if the node doesn't support ACLs.
     *
     * @param string|DAV\INode $node
     * @return array
     */
    function getACL($node) {

        if (is_string($node)) {
            $node = $this->server->tree->getNodeForPath($node);
        }
        if (!$node instanceof IACL) {
            return null;
        }
        $acl = $node->getACL();
        foreach ($this->adminPrincipals as $adminPrincipal) {
            $acl[] = [
                'principal' => $adminPrincipal,
                'privilege' => '{DAV:}all',
                'protected' => true,
            ];
        }
        return $acl;

    }

    /**
     * Returns a list of privileges the current user has
     * on a particular node.
     *
     * Either a uri or a DAV\INode may be passed.
     *
     * null will be returned if the node doesn't support ACLs.
     *
     * @param string|DAV\INode $node
     * @return array
     */
    function getCurrentUserPrivilegeSet($node) {

        if (is_string($node)) {
            $node = $this->server->tree->getNodeForPath($node);
        }

        $acl = $this->getACL($node);

        if (is_null($acl)) return null;

        $principals = $this->getCurrentUserPrincipals();

        $collected = [];

        foreach ($acl as $ace) {

            $principal = $ace['principal'];

            switch ($principal) {

                case '{DAV:}owner' :
                    $owner = $node->getOwner();
                    if ($owner && in_array($owner, $principals)) {
                        $collected[] = $ace;
                    }
                    break;


                // 'all' matches for every user
                case '{DAV:}all' :

                // 'authenticated' matched for every user that's logged in.
                // Since it's not possible to use ACL while not being logged
                // in, this is also always true.
                case '{DAV:}authenticated' :
                    $collected[] = $ace;
                    break;

                // 'unauthenticated' can never occur either, so we simply
                // ignore these.
                case '{DAV:}unauthenticated' :
                    break;

                default :
                    if (in_array($ace['principal'], $principals)) {
                        $collected[] = $ace;
                    }
                    break;

            }


        }

        // Now we deduct all aggregated privileges.
        $flat = $this->getFlatPrivilegeSet($node);

        $collected2 = [];
        while (count($collected)) {

            $current = array_pop($collected);
            $collected2[] = $current['privilege'];

            foreach ($flat[$current['privilege']]['aggregates'] as $subPriv) {
                $collected2[] = $subPriv;
                $collected[] = $flat[$subPriv];
            }

        }

        return array_values(array_unique($collected2));

    }


    /**
     * Returns a principal based on its uri.
     *
     * Returns null if the principal could not be found.
     *
     * @param string $uri
     * @return null|string
     */
    function getPrincipalByUri($uri) {

        $result = null;
        $collections = $this->principalCollectionSet;
        foreach ($collections as $collection) {

            $principalCollection = $this->server->tree->getNodeForPath($collection);
            if (!$principalCollection instanceof IPrincipalCollection) {
                // Not a principal collection, we're simply going to ignore
                // this.
                continue;
            }

            $result = $principalCollection->findByUri($uri);
            if ($result) {
                return $result;
            }

        }

    }

    /**
     * Principal property search
     *
     * This method can search for principals matching certain values in
     * properties.
     *
     * This method will return a list of properties for the matched properties.
     *
     * @param array $searchProperties    The properties to search on. This is a
     *                                   key-value list. The keys are property
     *                                   names, and the values the strings to
     *                                   match them on.
     * @param array $requestedProperties This is the list of properties to
     *                                   return for every match.
     * @param string $collectionUri      The principal collection to search on.
     *                                   If this is ommitted, the standard
     *                                   principal collection-set will be used.
     * @param string $test               "allof" to use AND to search the
     *                                   properties. 'anyof' for OR.
     * @return array     This method returns an array structure similar to
     *                  Sabre\DAV\Server::getPropertiesForPath. Returned
     *                  properties are index by a HTTP status code.
     */
    function principalSearch(array $searchProperties, array $requestedProperties, $collectionUri = null, $test = 'allof') {

        if (!is_null($collectionUri)) {
            $uris = [$collectionUri];
        } else {
            $uris = $this->principalCollectionSet;
        }

        $lookupResults = [];
        foreach ($uris as $uri) {

            $principalCollection = $this->server->tree->getNodeForPath($uri);
            if (!$principalCollection instanceof IPrincipalCollection) {
                // Not a principal collection, we're simply going to ignore
                // this.
                continue;
            }

            $results = $principalCollection->searchPrincipals($searchProperties, $test);
            foreach ($results as $result) {
                $lookupResults[] = rtrim($uri, '/') . '/' . $result;
            }

        }

        $matches = [];

        foreach ($lookupResults as $lookupResult) {

            list($matches[]) = $this->server->getPropertiesForPath($lookupResult, $requestedProperties, 0);

        }

        return $matches;

    }

    /**
     * Sets up the plugin
     *
     * This method is automatically called by the server class.
     *
     * @param DAV\Server $server
     * @return void
     */
    function initialize(DAV\Server $server) {

        $this->server = $server;
        $server->on('propFind',            [$this, 'propFind'], 20);
        $server->on('beforeMethod',        [$this, 'beforeMethod'], 20);
        $server->on('beforeBind',          [$this, 'beforeBind'], 20);
        $server->on('beforeUnbind',        [$this, 'beforeUnbind'], 20);
        $server->on('propPatch',           [$this, 'propPatch']);
        $server->on('beforeUnlock',        [$this, 'beforeUnlock'], 20);
        $server->on('report',              [$this, 'report']);
        $server->on('method:ACL',          [$this, 'httpAcl']);
        $server->on('onHTMLActionsPanel',  [$this, 'htmlActionsPanel']);

        array_push($server->protectedProperties,
            '{DAV:}alternate-URI-set',
            '{DAV:}principal-URL',
            '{DAV:}group-membership',
            '{DAV:}principal-collection-set',
            '{DAV:}current-user-principal',
            '{DAV:}supported-privilege-set',
            '{DAV:}current-user-privilege-set',
            '{DAV:}acl',
            '{DAV:}acl-restrictions',
            '{DAV:}inherited-acl-set',
            '{DAV:}owner',
            '{DAV:}group'
        );

        // Automatically mapping nodes implementing IPrincipal to the
        // {DAV:}principal resourcetype.
        $server->resourceTypeMapping['Sabre\\DAVACL\\IPrincipal'] = '{DAV:}principal';

        // Mapping the group-member-set property to the HrefList property
        // class.
        $server->xml->elementMap['{DAV:}group-member-set'] = 'Sabre\\DAV\\Xml\\Property\\Href';
        $server->xml->elementMap['{DAV:}acl'] = 'Sabre\\DAVACL\\Xml\\Property\\Acl';
        $server->xml->elementMap['{DAV:}expand-property'] = 'Sabre\\DAVACL\\Xml\\Request\\ExpandPropertyReport';
        $server->xml->elementMap['{DAV:}principal-property-search'] = 'Sabre\\DAVACL\\Xml\\Request\\PrincipalPropertySearchReport';
        $server->xml->elementMap['{DAV:}principal-search-property-set'] = 'Sabre\\DAVACL\\Xml\\Request\\PrincipalSearchPropertySetReport';

    }

    /* {{{ Event handlers */

    /**
     * Triggered before any method is handled
     *
     * @param RequestInterface $request
     * @param ResponseInterface $response
     * @return void
     */
    function beforeMethod(RequestInterface $request, ResponseInterface $response) {

        $method = $request->getMethod();
        $path = $request->getPath();

        $exists = $this->server->tree->nodeExists($path);

        // If the node doesn't exists, none of these checks apply
        if (!$exists) return;

        switch ($method) {

            case 'GET' :
            case 'HEAD' :
            case 'OPTIONS' :
                // For these 3 we only need to know if the node is readable.
                $this->checkPrivileges($path, '{DAV:}read');
                break;

            case 'PUT' :
            case 'LOCK' :
            case 'UNLOCK' :
                // This method requires the write-content priv if the node
                // already exists, and bind on the parent if the node is being
                // created.
                // The bind privilege is handled in the beforeBind event.
                $this->checkPrivileges($path, '{DAV:}write-content');
                break;


            case 'PROPPATCH' :
                $this->checkPrivileges($path, '{DAV:}write-properties');
                break;

            case 'ACL' :
                $this->checkPrivileges($path, '{DAV:}write-acl');
                break;

            case 'COPY' :
            case 'MOVE' :
                // Copy requires read privileges on the entire source tree.
                // If the target exists write-content normally needs to be
                // checked, however, we're deleting the node beforehand and
                // creating a new one after, so this is handled by the
                // beforeUnbind event.
                //
                // The creation of the new node is handled by the beforeBind
                // event.
                //
                // If MOVE is used beforeUnbind will also be used to check if
                // the sourcenode can be deleted.
                $this->checkPrivileges($path, '{DAV:}read', self::R_RECURSIVE);

                break;

        }

    }

    /**
     * Triggered before a new node is created.
     *
     * This allows us to check permissions for any operation that creates a
     * new node, such as PUT, MKCOL, MKCALENDAR, LOCK, COPY and MOVE.
     *
     * @param string $uri
     * @return void
     */
    function beforeBind($uri) {

        list($parentUri) = Uri\split($uri);
        $this->checkPrivileges($parentUri, '{DAV:}bind');

    }

    /**
     * Triggered before a node is deleted
     *
     * This allows us to check permissions for any operation that will delete
     * an existing node.
     *
     * @param string $uri
     * @return void
     */
    function beforeUnbind($uri) {

        list($parentUri) = Uri\split($uri);
        $this->checkPrivileges($parentUri, '{DAV:}unbind', self::R_RECURSIVEPARENTS);

    }

    /**
     * Triggered before a node is unlocked.
     *
     * @param string $uri
     * @param DAV\Locks\LockInfo $lock
     * @TODO: not yet implemented
     * @return void
     */
    function beforeUnlock($uri, DAV\Locks\LockInfo $lock) {


    }

    /**
     * Triggered before properties are looked up in specific nodes.
     *
     * @param DAV\PropFind $propFind
     * @param DAV\INode $node
     * @param array $requestedProperties
     * @param array $returnedProperties
     * @TODO really should be broken into multiple methods, or even a class.
     * @return bool
     */
    function propFind(DAV\PropFind $propFind, DAV\INode $node) {

        $path = $propFind->getPath();

        // Checking the read permission
        if (!$this->checkPrivileges($path, '{DAV:}read', self::R_PARENT, false)) {
            // User is not allowed to read properties

            // Returning false causes the property-fetching system to pretend
            // that the node does not exist, and will cause it to be hidden
            // from listings such as PROPFIND or the browser plugin.
            if ($this->hideNodesFromListings) {
                return false;
            }

            // Otherwise we simply mark every property as 403.
            foreach ($propFind->getRequestedProperties() as $requestedProperty) {
                $propFind->set($requestedProperty, null, 403);
            }

            return;

        }

        /* Adding principal properties */
        if ($node instanceof IPrincipal) {

            $propFind->handle('{DAV:}alternate-URI-set', function() use ($node) {
                return new DAV\Xml\Property\Href($node->getAlternateUriSet());
            });
            $propFind->handle('{DAV:}principal-URL', function() use ($node) {
                return new DAV\Xml\Property\Href($node->getPrincipalUrl() . '/');
            });
            $propFind->handle('{DAV:}group-member-set', function() use ($node) {
                $members = $node->getGroupMemberSet();
                foreach ($members as $k => $member) {
                    $members[$k] = rtrim($member, '/') . '/';
                }
                return new DAV\Xml\Property\Href($members);
            });
            $propFind->handle('{DAV:}group-membership', function() use ($node) {
                $members = $node->getGroupMembership();
                foreach ($members as $k => $member) {
                    $members[$k] = rtrim($member, '/') . '/';
                }
                return new DAV\Xml\Property\Href($members);
            });
            $propFind->handle('{DAV:}displayname', [$node, 'getDisplayName']);

        }

        $propFind->handle('{DAV:}principal-collection-set', function() {

            $val = $this->principalCollectionSet;
            // Ensuring all collections end with a slash
            foreach ($val as $k => $v) $val[$k] = $v . '/';
            return new DAV\Xml\Property\Href($val);

        });
        $propFind->handle('{DAV:}current-user-principal', function() {
            if ($url = $this->getCurrentUserPrincipal()) {
                return new Xml\Property\Principal(Xml\Property\Principal::HREF, $url . '/');
            } else {
                return new Xml\Property\Principal(Xml\Property\Principal::UNAUTHENTICATED);
            }
        });
        $propFind->handle('{DAV:}supported-privilege-set', function() use ($node) {
            return new Xml\Property\SupportedPrivilegeSet($this->getSupportedPrivilegeSet($node));
        });
        $propFind->handle('{DAV:}current-user-privilege-set', function() use ($node, $propFind, $path) {
            if (!$this->checkPrivileges($path, '{DAV:}read-current-user-privilege-set', self::R_PARENT, false)) {
                $propFind->set('{DAV:}current-user-privilege-set', null, 403);
            } else {
                $val = $this->getCurrentUserPrivilegeSet($node);
                if (!is_null($val)) {
                    return new Xml\Property\CurrentUserPrivilegeSet($val);
                }
            }
        });
        $propFind->handle('{DAV:}acl', function() use ($node, $propFind, $path) {
            /* The ACL property contains all the permissions */
            if (!$this->checkPrivileges($path, '{DAV:}read-acl', self::R_PARENT, false)) {
                $propFind->set('{DAV:}acl', null, 403);
            } else {
                $acl = $this->getACL($node);
                if (!is_null($acl)) {
                    return new Xml\Property\Acl($this->getACL($node));
                }
            }
        });
        $propFind->handle('{DAV:}acl-restrictions', function() {
            return new Xml\Property\AclRestrictions();
        });

        /* Adding ACL properties */
        if ($node instanceof IACL) {
            $propFind->handle('{DAV:}owner', function() use ($node) {
                return new DAV\Xml\Property\Href($node->getOwner() . '/');
            });
        }

    }

    /**
     * This method intercepts PROPPATCH methods and make sure the
     * group-member-set is updated correctly.
     *
     * @param string $path
     * @param DAV\PropPatch $propPatch
     * @return void
     */
    function propPatch($path, DAV\PropPatch $propPatch) {

        $propPatch->handle('{DAV:}group-member-set', function($value) use ($path) {
            if (is_null($value)) {
                $memberSet = [];
            } elseif ($value instanceof DAV\Xml\Property\Href) {
                $memberSet = array_map(
                    [$this->server, 'calculateUri'],
                    $value->getHrefs()
                );
            } else {
                throw new DAV\Exception('The group-member-set property MUST be an instance of Sabre\DAV\Property\HrefList or null');
            }
            $node = $this->server->tree->getNodeForPath($path);
            if (!($node instanceof IPrincipal)) {
                // Fail
                return false;
            }

            $node->setGroupMemberSet($memberSet);
            // We must also clear our cache, just in case

            $this->principalMembershipCache = [];

            return true;
        });

    }

    /**
     * This method handles HTTP REPORT requests
     *
     * @param string $reportName
     * @param mixed $report
     * @param mixed $path
     * @return bool
     */
    function report($reportName, $report, $path) {

        switch ($reportName) {

            case '{DAV:}principal-property-search' :
                $this->server->transactionType = 'report-principal-property-search';
                $this->principalPropertySearchReport($report);
                return false;
            case '{DAV:}principal-search-property-set' :
                $this->server->transactionType = 'report-principal-search-property-set';
                $this->principalSearchPropertySetReport($report);
                return false;
            case '{DAV:}expand-property' :
                $this->server->transactionType = 'report-expand-property';
                $this->expandPropertyReport($report);
                return false;

        }

    }

    /**
     * This method is responsible for handling the 'ACL' event.
     *
     * @param RequestInterface $request
     * @param ResponseInterface $response
     * @return bool
     */
    function httpAcl(RequestInterface $request, ResponseInterface $response) {

        $path = $request->getPath();
        $body = $request->getBodyAsString();

        if (!$body) {
            throw new DAV\Exception\BadRequest('XML body expected in ACL request');
        }

        $acl = $this->server->xml->expect('{DAV:}acl', $body);
        $newAcl = $acl->getPrivileges();

        // Normalizing urls
        foreach ($newAcl as $k => $newAce) {
            $newAcl[$k]['principal'] = $this->server->calculateUri($newAce['principal']);
        }
        $node = $this->server->tree->getNodeForPath($path);

        if (!$node instanceof IACL) {
            throw new DAV\Exception\MethodNotAllowed('This node does not support the ACL method');
        }

        $oldAcl = $this->getACL($node);

        $supportedPrivileges = $this->getFlatPrivilegeSet($node);

        /* Checking if protected principals from the existing principal set are
           not overwritten. */
        foreach ($oldAcl as $oldAce) {

            if (!isset($oldAce['protected']) || !$oldAce['protected']) continue;

            $found = false;
            foreach ($newAcl as $newAce) {
                if (
                    $newAce['privilege'] === $oldAce['privilege'] &&
                    $newAce['principal'] === $oldAce['principal'] &&
                    $newAce['protected']
                )
                $found = true;
            }

            if (!$found)
                throw new Exception\AceConflict('This resource contained a protected {DAV:}ace, but this privilege did not occur in the ACL request');

        }

        foreach ($newAcl as $newAce) {

            // Do we recognize the privilege
            if (!isset($supportedPrivileges[$newAce['privilege']])) {
                throw new Exception\NotSupportedPrivilege('The privilege you specified (' . $newAce['privilege'] . ') is not recognized by this server');
            }

            if ($supportedPrivileges[$newAce['privilege']]['abstract']) {
                throw new Exception\NoAbstract('The privilege you specified (' . $newAce['privilege'] . ') is an abstract privilege');
            }

            // Looking up the principal
            try {
                $principal = $this->server->tree->getNodeForPath($newAce['principal']);
            } catch (DAV\Exception\NotFound $e) {
                throw new Exception\NotRecognizedPrincipal('The specified principal (' . $newAce['principal'] . ') does not exist');
            }
            if (!($principal instanceof IPrincipal)) {
                throw new Exception\NotRecognizedPrincipal('The specified uri (' . $newAce['principal'] . ') is not a principal');
            }

        }
        $node->setACL($newAcl);

        $response->setStatus(200);

        // Breaking the event chain, because we handled this method.
        return false;

    }

    /* }}} */

    /* Reports {{{ */

    /**
     * The expand-property report is defined in RFC3253 section 3-8.
     *
     * This report is very similar to a standard PROPFIND. The difference is
     * that it has the additional ability to look at properties containing a
     * {DAV:}href element, follow that property and grab additional elements
     * there.
     *
     * Other rfc's, such as ACL rely on this report, so it made sense to put
     * it in this plugin.
     *
     * @param Xml\Request\ExpandPropertyReport $report
     * @return void
     */
    protected function expandPropertyReport($report) {

        $depth = $this->server->getHTTPDepth(0);
        $requestUri = $this->server->getRequestUri();

        $result = $this->expandProperties($requestUri, $report->properties, $depth);

        $xml = $this->server->xml->write(
            '{DAV:}multistatus',
            new DAV\Xml\Response\MultiStatus($result),
            $this->server->getBaseUri()
        );
        $this->server->httpResponse->setHeader('Content-Type', 'application/xml; charset=utf-8');
        $this->server->httpResponse->setStatus(207);
        $this->server->httpResponse->setBody($xml);

    }

    /**
     * This method expands all the properties and returns
     * a list with property values
     *
     * @param array $path
     * @param array $requestedProperties the list of required properties
     * @param int $depth
     * @return array
     */
    protected function expandProperties($path, array $requestedProperties, $depth) {

        $foundProperties = $this->server->getPropertiesForPath($path, array_keys($requestedProperties), $depth);

        $result = [];

        foreach ($foundProperties as $node) {

            foreach ($requestedProperties as $propertyName => $childRequestedProperties) {

                // We're only traversing if sub-properties were requested
                if (count($childRequestedProperties) === 0) continue;

                // We only have to do the expansion if the property was found
                // and it contains an href element.
                if (!array_key_exists($propertyName, $node[200])) continue;

                if (!$node[200][$propertyName] instanceof DAV\Xml\Property\Href) {
                    continue;
                }

                $childHrefs = $node[200][$propertyName]->getHrefs();
                $childProps = [];

                foreach ($childHrefs as $href) {
                    // Gathering the result of the children
                    $childProps[] = [
                        'name'  => '{DAV:}response',
                        'value' => $this->expandProperties($href, $childRequestedProperties, 0)[0]
                    ];
                }

                // Replacing the property with its expannded form.
                $node[200][$propertyName] = $childProps;

            }
            $result[] = new DAV\Xml\Element\Response($node['href'], $node);

        }

        return $result;

    }

    /**
     * principalSearchPropertySetReport
     *
     * This method responsible for handing the
     * {DAV:}principal-search-property-set report. This report returns a list
     * of properties the client may search on, using the
     * {DAV:}principal-property-search report.
     *
     * @param Xml\Request\PrincipalSearchPropertySetReport $report
     * @return void
     */
    protected function principalSearchPropertySetReport($report) {

        $httpDepth = $this->server->getHTTPDepth(0);
        if ($httpDepth !== 0) {
            throw new DAV\Exception\BadRequest('This report is only defined when Depth: 0');
        }

        $writer = $this->server->xml->getWriter();
        $writer->openMemory();
        $writer->startDocument();

        $writer->startElement('{DAV:}principal-search-property-set');

        foreach ($this->principalSearchPropertySet as $propertyName => $description) {

            $writer->startElement('{DAV:}principal-search-property');
            $writer->startElement('{DAV:}prop');

            $writer->writeElement($propertyName);

            $writer->endElement(); // prop

            if ($description) {
                $writer->write([[
                    'name'       => '{DAV:}description',
                    'value'      => $description,
                    'attributes' => ['xml:lang' => 'en']
                ]]);
            }

            $writer->endElement(); // principal-search-property


        }

        $writer->endElement(); // principal-search-property-set

        $this->server->httpResponse->setHeader('Content-Type', 'application/xml; charset=utf-8');
        $this->server->httpResponse->setStatus(200);
        $this->server->httpResponse->setBody($writer->outputMemory());

    }

    /**
     * principalPropertySearchReport
     *
     * This method is responsible for handing the
     * {DAV:}principal-property-search report. This report can be used for
     * clients to search for groups of principals, based on the value of one
     * or more properties.
     *
     * @param Xml\Request\PrincipalPropertySearchReport $report
     * @return void
     */
    protected function principalPropertySearchReport($report) {

        $uri = null;
        if (!$report->applyToPrincipalCollectionSet) {
            $uri = $this->server->httpRequest->getPath();
        }
        if ($this->server->getHttpDepth('0') !== 0) {
            throw new BadRequest('Depth must be 0');
        }
        $result = $this->principalSearch(
            $report->searchProperties,
            $report->properties,
            $uri,
            $report->test
        );

        $prefer = $this->server->getHTTPPrefer();

        $this->server->httpResponse->setStatus(207);
        $this->server->httpResponse->setHeader('Content-Type', 'application/xml; charset=utf-8');
        $this->server->httpResponse->setHeader('Vary', 'Brief,Prefer');
        $this->server->httpResponse->setBody($this->server->generateMultiStatus($result, $prefer['return'] === 'minimal'));

    }

    /* }}} */

    /**
     * This method is used to generate HTML output for the
     * DAV\Browser\Plugin. This allows us to generate an interface users
     * can use to create new calendars.
     *
     * @param DAV\INode $node
     * @param string $output
     * @return bool
     */
    function htmlActionsPanel(DAV\INode $node, &$output) {

        if (!$node instanceof PrincipalCollection)
            return;

        $output .= '<tr><td colspan="2"><form method="post" action="">
            <h3>Create new principal</h3>
            <input type="hidden" name="sabreAction" value="mkcol" />
            <input type="hidden" name="resourceType" value="{DAV:}principal" />
            <label>Name (uri):</label> <input type="text" name="name" /><br />
            <label>Display name:</label> <input type="text" name="{DAV:}displayname" /><br />
            <label>Email address:</label> <input type="text" name="{http://sabredav*DOT*org/ns}email-address" /><br />
            <input type="submit" value="create" />
            </form>
            </td></tr>';

        return false;

    }

    /**
     * Returns a bunch of meta-data about the plugin.
     *
     * Providing this information is optional, and is mainly displayed by the
     * Browser plugin.
     *
     * The description key in the returned array may contain html and will not
     * be sanitized.
     *
     * @return array
     */
    function getPluginInfo() {

        return [
            'name'        => $this->getPluginName(),
            'description' => 'Adds support for WebDAV ACL (rfc3744)',
            'link'        => 'http://sabre.io/dav/acl/',
        ];

    }
}