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1/* Keyring handling
2 *
3 * Copyright (C) 2004-2005, 2008, 2013 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/sched.h>
15#include <linux/slab.h>
16#include <linux/security.h>
17#include <linux/seq_file.h>
18#include <linux/err.h>
19#include <keys/keyring-type.h>
20#include <keys/user-type.h>
21#include <linux/assoc_array_priv.h>
22#include <linux/uaccess.h>
23#include "internal.h"
24
25/*
26 * When plumbing the depths of the key tree, this sets a hard limit
27 * set on how deep we're willing to go.
28 */
29#define KEYRING_SEARCH_MAX_DEPTH 6
30
31/*
32 * We keep all named keyrings in a hash to speed looking them up.
33 */
34#define KEYRING_NAME_HASH_SIZE (1 << 5)
35
36/*
37 * We mark pointers we pass to the associative array with bit 1 set if
38 * they're keyrings and clear otherwise.
39 */
40#define KEYRING_PTR_SUBTYPE 0x2UL
41
42static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
43{
44 return (unsigned long)x & KEYRING_PTR_SUBTYPE;
45}
46static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
47{
48 void *object = assoc_array_ptr_to_leaf(x);
49 return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
50}
51static inline void *keyring_key_to_ptr(struct key *key)
52{
53 if (key->type == &key_type_keyring)
54 return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
55 return key;
56}
57
58static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
59static DEFINE_RWLOCK(keyring_name_lock);
60
61static inline unsigned keyring_hash(const char *desc)
62{
63 unsigned bucket = 0;
64
65 for (; *desc; desc++)
66 bucket += (unsigned char)*desc;
67
68 return bucket & (KEYRING_NAME_HASH_SIZE - 1);
69}
70
71/*
72 * The keyring key type definition. Keyrings are simply keys of this type and
73 * can be treated as ordinary keys in addition to having their own special
74 * operations.
75 */
76static int keyring_preparse(struct key_preparsed_payload *prep);
77static void keyring_free_preparse(struct key_preparsed_payload *prep);
78static int keyring_instantiate(struct key *keyring,
79 struct key_preparsed_payload *prep);
80static void keyring_revoke(struct key *keyring);
81static void keyring_destroy(struct key *keyring);
82static void keyring_describe(const struct key *keyring, struct seq_file *m);
83static long keyring_read(const struct key *keyring,
84 char __user *buffer, size_t buflen);
85
86struct key_type key_type_keyring = {
87 .name = "keyring",
88 .def_datalen = 0,
89 .preparse = keyring_preparse,
90 .free_preparse = keyring_free_preparse,
91 .instantiate = keyring_instantiate,
92 .revoke = keyring_revoke,
93 .destroy = keyring_destroy,
94 .describe = keyring_describe,
95 .read = keyring_read,
96};
97EXPORT_SYMBOL(key_type_keyring);
98
99/*
100 * Semaphore to serialise link/link calls to prevent two link calls in parallel
101 * introducing a cycle.
102 */
103static DECLARE_RWSEM(keyring_serialise_link_sem);
104
105/*
106 * Publish the name of a keyring so that it can be found by name (if it has
107 * one).
108 */
109static void keyring_publish_name(struct key *keyring)
110{
111 int bucket;
112
113 if (keyring->description) {
114 bucket = keyring_hash(keyring->description);
115
116 write_lock(&keyring_name_lock);
117
118 if (!keyring_name_hash[bucket].next)
119 INIT_LIST_HEAD(&keyring_name_hash[bucket]);
120
121 list_add_tail(&keyring->name_link,
122 &keyring_name_hash[bucket]);
123
124 write_unlock(&keyring_name_lock);
125 }
126}
127
128/*
129 * Preparse a keyring payload
130 */
131static int keyring_preparse(struct key_preparsed_payload *prep)
132{
133 return prep->datalen != 0 ? -EINVAL : 0;
134}
135
136/*
137 * Free a preparse of a user defined key payload
138 */
139static void keyring_free_preparse(struct key_preparsed_payload *prep)
140{
141}
142
143/*
144 * Initialise a keyring.
145 *
146 * Returns 0 on success, -EINVAL if given any data.
147 */
148static int keyring_instantiate(struct key *keyring,
149 struct key_preparsed_payload *prep)
150{
151 assoc_array_init(&keyring->keys);
152 /* make the keyring available by name if it has one */
153 keyring_publish_name(keyring);
154 return 0;
155}
156
157/*
158 * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit. Ideally we'd
159 * fold the carry back too, but that requires inline asm.
160 */
161static u64 mult_64x32_and_fold(u64 x, u32 y)
162{
163 u64 hi = (u64)(u32)(x >> 32) * y;
164 u64 lo = (u64)(u32)(x) * y;
165 return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
166}
167
168/*
169 * Hash a key type and description.
170 */
171static unsigned long hash_key_type_and_desc(const struct keyring_index_key *index_key)
172{
173 const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
174 const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
175 const char *description = index_key->description;
176 unsigned long hash, type;
177 u32 piece;
178 u64 acc;
179 int n, desc_len = index_key->desc_len;
180
181 type = (unsigned long)index_key->type;
182
183 acc = mult_64x32_and_fold(type, desc_len + 13);
184 acc = mult_64x32_and_fold(acc, 9207);
185 for (;;) {
186 n = desc_len;
187 if (n <= 0)
188 break;
189 if (n > 4)
190 n = 4;
191 piece = 0;
192 memcpy(&piece, description, n);
193 description += n;
194 desc_len -= n;
195 acc = mult_64x32_and_fold(acc, piece);
196 acc = mult_64x32_and_fold(acc, 9207);
197 }
198
199 /* Fold the hash down to 32 bits if need be. */
200 hash = acc;
201 if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
202 hash ^= acc >> 32;
203
204 /* Squidge all the keyrings into a separate part of the tree to
205 * ordinary keys by making sure the lowest level segment in the hash is
206 * zero for keyrings and non-zero otherwise.
207 */
208 if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
209 return hash | (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
210 if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
211 return (hash + (hash << level_shift)) & ~fan_mask;
212 return hash;
213}
214
215/*
216 * Build the next index key chunk.
217 *
218 * On 32-bit systems the index key is laid out as:
219 *
220 * 0 4 5 9...
221 * hash desclen typeptr desc[]
222 *
223 * On 64-bit systems:
224 *
225 * 0 8 9 17...
226 * hash desclen typeptr desc[]
227 *
228 * We return it one word-sized chunk at a time.
229 */
230static unsigned long keyring_get_key_chunk(const void *data, int level)
231{
232 const struct keyring_index_key *index_key = data;
233 unsigned long chunk = 0;
234 long offset = 0;
235 int desc_len = index_key->desc_len, n = sizeof(chunk);
236
237 level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
238 switch (level) {
239 case 0:
240 return hash_key_type_and_desc(index_key);
241 case 1:
242 return ((unsigned long)index_key->type << 8) | desc_len;
243 case 2:
244 if (desc_len == 0)
245 return (u8)((unsigned long)index_key->type >>
246 (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
247 n--;
248 offset = 1;
249 default:
250 offset += sizeof(chunk) - 1;
251 offset += (level - 3) * sizeof(chunk);
252 if (offset >= desc_len)
253 return 0;
254 desc_len -= offset;
255 if (desc_len > n)
256 desc_len = n;
257 offset += desc_len;
258 do {
259 chunk <<= 8;
260 chunk |= ((u8*)index_key->description)[--offset];
261 } while (--desc_len > 0);
262
263 if (level == 2) {
264 chunk <<= 8;
265 chunk |= (u8)((unsigned long)index_key->type >>
266 (ASSOC_ARRAY_KEY_CHUNK_SIZE - 8));
267 }
268 return chunk;
269 }
270}
271
272static unsigned long keyring_get_object_key_chunk(const void *object, int level)
273{
274 const struct key *key = keyring_ptr_to_key(object);
275 return keyring_get_key_chunk(&key->index_key, level);
276}
277
278static bool keyring_compare_object(const void *object, const void *data)
279{
280 const struct keyring_index_key *index_key = data;
281 const struct key *key = keyring_ptr_to_key(object);
282
283 return key->index_key.type == index_key->type &&
284 key->index_key.desc_len == index_key->desc_len &&
285 memcmp(key->index_key.description, index_key->description,
286 index_key->desc_len) == 0;
287}
288
289/*
290 * Compare the index keys of a pair of objects and determine the bit position
291 * at which they differ - if they differ.
292 */
293static int keyring_diff_objects(const void *object, const void *data)
294{
295 const struct key *key_a = keyring_ptr_to_key(object);
296 const struct keyring_index_key *a = &key_a->index_key;
297 const struct keyring_index_key *b = data;
298 unsigned long seg_a, seg_b;
299 int level, i;
300
301 level = 0;
302 seg_a = hash_key_type_and_desc(a);
303 seg_b = hash_key_type_and_desc(b);
304 if ((seg_a ^ seg_b) != 0)
305 goto differ;
306
307 /* The number of bits contributed by the hash is controlled by a
308 * constant in the assoc_array headers. Everything else thereafter we
309 * can deal with as being machine word-size dependent.
310 */
311 level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;
312 seg_a = a->desc_len;
313 seg_b = b->desc_len;
314 if ((seg_a ^ seg_b) != 0)
315 goto differ;
316
317 /* The next bit may not work on big endian */
318 level++;
319 seg_a = (unsigned long)a->type;
320 seg_b = (unsigned long)b->type;
321 if ((seg_a ^ seg_b) != 0)
322 goto differ;
323
324 level += sizeof(unsigned long);
325 if (a->desc_len == 0)
326 goto same;
327
328 i = 0;
329 if (((unsigned long)a->description | (unsigned long)b->description) &
330 (sizeof(unsigned long) - 1)) {
331 do {
332 seg_a = *(unsigned long *)(a->description + i);
333 seg_b = *(unsigned long *)(b->description + i);
334 if ((seg_a ^ seg_b) != 0)
335 goto differ_plus_i;
336 i += sizeof(unsigned long);
337 } while (i < (a->desc_len & (sizeof(unsigned long) - 1)));
338 }
339
340 for (; i < a->desc_len; i++) {
341 seg_a = *(unsigned char *)(a->description + i);
342 seg_b = *(unsigned char *)(b->description + i);
343 if ((seg_a ^ seg_b) != 0)
344 goto differ_plus_i;
345 }
346
347same:
348 return -1;
349
350differ_plus_i:
351 level += i;
352differ:
353 i = level * 8 + __ffs(seg_a ^ seg_b);
354 return i;
355}
356
357/*
358 * Free an object after stripping the keyring flag off of the pointer.
359 */
360static void keyring_free_object(void *object)
361{
362 key_put(keyring_ptr_to_key(object));
363}
364
365/*
366 * Operations for keyring management by the index-tree routines.
367 */
368static const struct assoc_array_ops keyring_assoc_array_ops = {
369 .get_key_chunk = keyring_get_key_chunk,
370 .get_object_key_chunk = keyring_get_object_key_chunk,
371 .compare_object = keyring_compare_object,
372 .diff_objects = keyring_diff_objects,
373 .free_object = keyring_free_object,
374};
375
376/*
377 * Clean up a keyring when it is destroyed. Unpublish its name if it had one
378 * and dispose of its data.
379 *
380 * The garbage collector detects the final key_put(), removes the keyring from
381 * the serial number tree and then does RCU synchronisation before coming here,
382 * so we shouldn't need to worry about code poking around here with the RCU
383 * readlock held by this time.
384 */
385static void keyring_destroy(struct key *keyring)
386{
387 if (keyring->description) {
388 write_lock(&keyring_name_lock);
389
390 if (keyring->name_link.next != NULL &&
391 !list_empty(&keyring->name_link))
392 list_del(&keyring->name_link);
393
394 write_unlock(&keyring_name_lock);
395 }
396
397 assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
398}
399
400/*
401 * Describe a keyring for /proc.
402 */
403static void keyring_describe(const struct key *keyring, struct seq_file *m)
404{
405 if (keyring->description)
406 seq_puts(m, keyring->description);
407 else
408 seq_puts(m, "[anon]");
409
410 if (key_is_instantiated(keyring)) {
411 if (keyring->keys.nr_leaves_on_tree != 0)
412 seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
413 else
414 seq_puts(m, ": empty");
415 }
416}
417
418struct keyring_read_iterator_context {
419 size_t qty;
420 size_t count;
421 key_serial_t __user *buffer;
422};
423
424static int keyring_read_iterator(const void *object, void *data)
425{
426 struct keyring_read_iterator_context *ctx = data;
427 const struct key *key = keyring_ptr_to_key(object);
428 int ret;
429
430 kenter("{%s,%d},,{%zu/%zu}",
431 key->type->name, key->serial, ctx->count, ctx->qty);
432
433 if (ctx->count >= ctx->qty)
434 return 1;
435
436 ret = put_user(key->serial, ctx->buffer);
437 if (ret < 0)
438 return ret;
439 ctx->buffer++;
440 ctx->count += sizeof(key->serial);
441 return 0;
442}
443
444/*
445 * Read a list of key IDs from the keyring's contents in binary form
446 *
447 * The keyring's semaphore is read-locked by the caller. This prevents someone
448 * from modifying it under us - which could cause us to read key IDs multiple
449 * times.
450 */
451static long keyring_read(const struct key *keyring,
452 char __user *buffer, size_t buflen)
453{
454 struct keyring_read_iterator_context ctx;
455 unsigned long nr_keys;
456 int ret;
457
458 kenter("{%d},,%zu", key_serial(keyring), buflen);
459
460 if (buflen & (sizeof(key_serial_t) - 1))
461 return -EINVAL;
462
463 nr_keys = keyring->keys.nr_leaves_on_tree;
464 if (nr_keys == 0)
465 return 0;
466
467 /* Calculate how much data we could return */
468 ctx.qty = nr_keys * sizeof(key_serial_t);
469
470 if (!buffer || !buflen)
471 return ctx.qty;
472
473 if (buflen > ctx.qty)
474 ctx.qty = buflen;
475
476 /* Copy the IDs of the subscribed keys into the buffer */
477 ctx.buffer = (key_serial_t __user *)buffer;
478 ctx.count = 0;
479 ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
480 if (ret < 0) {
481 kleave(" = %d [iterate]", ret);
482 return ret;
483 }
484
485 kleave(" = %zu [ok]", ctx.count);
486 return ctx.count;
487}
488
489/*
490 * Allocate a keyring and link into the destination keyring.
491 */
492struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
493 const struct cred *cred, key_perm_t perm,
494 unsigned long flags, struct key *dest)
495{
496 struct key *keyring;
497 int ret;
498
499 keyring = key_alloc(&key_type_keyring, description,
500 uid, gid, cred, perm, flags);
501 if (!IS_ERR(keyring)) {
502 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
503 if (ret < 0) {
504 key_put(keyring);
505 keyring = ERR_PTR(ret);
506 }
507 }
508
509 return keyring;
510}
511EXPORT_SYMBOL(keyring_alloc);
512
513/*
514 * By default, we keys found by getting an exact match on their descriptions.
515 */
516bool key_default_cmp(const struct key *key,
517 const struct key_match_data *match_data)
518{
519 return strcmp(key->description, match_data->raw_data) == 0;
520}
521
522/*
523 * Iteration function to consider each key found.
524 */
525static int keyring_search_iterator(const void *object, void *iterator_data)
526{
527 struct keyring_search_context *ctx = iterator_data;
528 const struct key *key = keyring_ptr_to_key(object);
529 unsigned long kflags = key->flags;
530
531 kenter("{%d}", key->serial);
532
533 /* ignore keys not of this type */
534 if (key->type != ctx->index_key.type) {
535 kleave(" = 0 [!type]");
536 return 0;
537 }
538
539 /* skip invalidated, revoked and expired keys */
540 if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
541 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
542 (1 << KEY_FLAG_REVOKED))) {
543 ctx->result = ERR_PTR(-EKEYREVOKED);
544 kleave(" = %d [invrev]", ctx->skipped_ret);
545 goto skipped;
546 }
547
548 if (key->expiry && ctx->now.tv_sec >= key->expiry) {
549 if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
550 ctx->result = ERR_PTR(-EKEYEXPIRED);
551 kleave(" = %d [expire]", ctx->skipped_ret);
552 goto skipped;
553 }
554 }
555
556 /* keys that don't match */
557 if (!ctx->match_data.cmp(key, &ctx->match_data)) {
558 kleave(" = 0 [!match]");
559 return 0;
560 }
561
562 /* key must have search permissions */
563 if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
564 key_task_permission(make_key_ref(key, ctx->possessed),
565 ctx->cred, KEY_NEED_SEARCH) < 0) {
566 ctx->result = ERR_PTR(-EACCES);
567 kleave(" = %d [!perm]", ctx->skipped_ret);
568 goto skipped;
569 }
570
571 if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
572 /* we set a different error code if we pass a negative key */
573 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
574 smp_rmb();
575 ctx->result = ERR_PTR(key->reject_error);
576 kleave(" = %d [neg]", ctx->skipped_ret);
577 goto skipped;
578 }
579 }
580
581 /* Found */
582 ctx->result = make_key_ref(key, ctx->possessed);
583 kleave(" = 1 [found]");
584 return 1;
585
586skipped:
587 return ctx->skipped_ret;
588}
589
590/*
591 * Search inside a keyring for a key. We can search by walking to it
592 * directly based on its index-key or we can iterate over the entire
593 * tree looking for it, based on the match function.
594 */
595static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
596{
597 if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
598 const void *object;
599
600 object = assoc_array_find(&keyring->keys,
601 &keyring_assoc_array_ops,
602 &ctx->index_key);
603 return object ? ctx->iterator(object, ctx) : 0;
604 }
605 return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
606}
607
608/*
609 * Search a tree of keyrings that point to other keyrings up to the maximum
610 * depth.
611 */
612static bool search_nested_keyrings(struct key *keyring,
613 struct keyring_search_context *ctx)
614{
615 struct {
616 struct key *keyring;
617 struct assoc_array_node *node;
618 int slot;
619 } stack[KEYRING_SEARCH_MAX_DEPTH];
620
621 struct assoc_array_shortcut *shortcut;
622 struct assoc_array_node *node;
623 struct assoc_array_ptr *ptr;
624 struct key *key;
625 int sp = 0, slot;
626
627 kenter("{%d},{%s,%s}",
628 keyring->serial,
629 ctx->index_key.type->name,
630 ctx->index_key.description);
631
632#define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
633 BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
634 (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
635
636 if (ctx->index_key.description)
637 ctx->index_key.desc_len = strlen(ctx->index_key.description);
638
639 /* Check to see if this top-level keyring is what we are looking for
640 * and whether it is valid or not.
641 */
642 if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
643 keyring_compare_object(keyring, &ctx->index_key)) {
644 ctx->skipped_ret = 2;
645 switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
646 case 1:
647 goto found;
648 case 2:
649 return false;
650 default:
651 break;
652 }
653 }
654
655 ctx->skipped_ret = 0;
656
657 /* Start processing a new keyring */
658descend_to_keyring:
659 kdebug("descend to %d", keyring->serial);
660 if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
661 (1 << KEY_FLAG_REVOKED)))
662 goto not_this_keyring;
663
664 /* Search through the keys in this keyring before its searching its
665 * subtrees.
666 */
667 if (search_keyring(keyring, ctx))
668 goto found;
669
670 /* Then manually iterate through the keyrings nested in this one.
671 *
672 * Start from the root node of the index tree. Because of the way the
673 * hash function has been set up, keyrings cluster on the leftmost
674 * branch of the root node (root slot 0) or in the root node itself.
675 * Non-keyrings avoid the leftmost branch of the root entirely (root
676 * slots 1-15).
677 */
678 ptr = ACCESS_ONCE(keyring->keys.root);
679 if (!ptr)
680 goto not_this_keyring;
681
682 if (assoc_array_ptr_is_shortcut(ptr)) {
683 /* If the root is a shortcut, either the keyring only contains
684 * keyring pointers (everything clusters behind root slot 0) or
685 * doesn't contain any keyring pointers.
686 */
687 shortcut = assoc_array_ptr_to_shortcut(ptr);
688 smp_read_barrier_depends();
689 if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
690 goto not_this_keyring;
691
692 ptr = ACCESS_ONCE(shortcut->next_node);
693 node = assoc_array_ptr_to_node(ptr);
694 goto begin_node;
695 }
696
697 node = assoc_array_ptr_to_node(ptr);
698 smp_read_barrier_depends();
699
700 ptr = node->slots[0];
701 if (!assoc_array_ptr_is_meta(ptr))
702 goto begin_node;
703
704descend_to_node:
705 /* Descend to a more distal node in this keyring's content tree and go
706 * through that.
707 */
708 kdebug("descend");
709 if (assoc_array_ptr_is_shortcut(ptr)) {
710 shortcut = assoc_array_ptr_to_shortcut(ptr);
711 smp_read_barrier_depends();
712 ptr = ACCESS_ONCE(shortcut->next_node);
713 BUG_ON(!assoc_array_ptr_is_node(ptr));
714 }
715 node = assoc_array_ptr_to_node(ptr);
716
717begin_node:
718 kdebug("begin_node");
719 smp_read_barrier_depends();
720 slot = 0;
721ascend_to_node:
722 /* Go through the slots in a node */
723 for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
724 ptr = ACCESS_ONCE(node->slots[slot]);
725
726 if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
727 goto descend_to_node;
728
729 if (!keyring_ptr_is_keyring(ptr))
730 continue;
731
732 key = keyring_ptr_to_key(ptr);
733
734 if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
735 if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
736 ctx->result = ERR_PTR(-ELOOP);
737 return false;
738 }
739 goto not_this_keyring;
740 }
741
742 /* Search a nested keyring */
743 if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
744 key_task_permission(make_key_ref(key, ctx->possessed),
745 ctx->cred, KEY_NEED_SEARCH) < 0)
746 continue;
747
748 /* stack the current position */
749 stack[sp].keyring = keyring;
750 stack[sp].node = node;
751 stack[sp].slot = slot;
752 sp++;
753
754 /* begin again with the new keyring */
755 keyring = key;
756 goto descend_to_keyring;
757 }
758
759 /* We've dealt with all the slots in the current node, so now we need
760 * to ascend to the parent and continue processing there.
761 */
762 ptr = ACCESS_ONCE(node->back_pointer);
763 slot = node->parent_slot;
764
765 if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
766 shortcut = assoc_array_ptr_to_shortcut(ptr);
767 smp_read_barrier_depends();
768 ptr = ACCESS_ONCE(shortcut->back_pointer);
769 slot = shortcut->parent_slot;
770 }
771 if (!ptr)
772 goto not_this_keyring;
773 node = assoc_array_ptr_to_node(ptr);
774 smp_read_barrier_depends();
775 slot++;
776
777 /* If we've ascended to the root (zero backpointer), we must have just
778 * finished processing the leftmost branch rather than the root slots -
779 * so there can't be any more keyrings for us to find.
780 */
781 if (node->back_pointer) {
782 kdebug("ascend %d", slot);
783 goto ascend_to_node;
784 }
785
786 /* The keyring we're looking at was disqualified or didn't contain a
787 * matching key.
788 */
789not_this_keyring:
790 kdebug("not_this_keyring %d", sp);
791 if (sp <= 0) {
792 kleave(" = false");
793 return false;
794 }
795
796 /* Resume the processing of a keyring higher up in the tree */
797 sp--;
798 keyring = stack[sp].keyring;
799 node = stack[sp].node;
800 slot = stack[sp].slot + 1;
801 kdebug("ascend to %d [%d]", keyring->serial, slot);
802 goto ascend_to_node;
803
804 /* We found a viable match */
805found:
806 key = key_ref_to_ptr(ctx->result);
807 key_check(key);
808 if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
809 key->last_used_at = ctx->now.tv_sec;
810 keyring->last_used_at = ctx->now.tv_sec;
811 while (sp > 0)
812 stack[--sp].keyring->last_used_at = ctx->now.tv_sec;
813 }
814 kleave(" = true");
815 return true;
816}
817
818/**
819 * keyring_search_aux - Search a keyring tree for a key matching some criteria
820 * @keyring_ref: A pointer to the keyring with possession indicator.
821 * @ctx: The keyring search context.
822 *
823 * Search the supplied keyring tree for a key that matches the criteria given.
824 * The root keyring and any linked keyrings must grant Search permission to the
825 * caller to be searchable and keys can only be found if they too grant Search
826 * to the caller. The possession flag on the root keyring pointer controls use
827 * of the possessor bits in permissions checking of the entire tree. In
828 * addition, the LSM gets to forbid keyring searches and key matches.
829 *
830 * The search is performed as a breadth-then-depth search up to the prescribed
831 * limit (KEYRING_SEARCH_MAX_DEPTH).
832 *
833 * Keys are matched to the type provided and are then filtered by the match
834 * function, which is given the description to use in any way it sees fit. The
835 * match function may use any attributes of a key that it wishes to to
836 * determine the match. Normally the match function from the key type would be
837 * used.
838 *
839 * RCU can be used to prevent the keyring key lists from disappearing without
840 * the need to take lots of locks.
841 *
842 * Returns a pointer to the found key and increments the key usage count if
843 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
844 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
845 * specified keyring wasn't a keyring.
846 *
847 * In the case of a successful return, the possession attribute from
848 * @keyring_ref is propagated to the returned key reference.
849 */
850key_ref_t keyring_search_aux(key_ref_t keyring_ref,
851 struct keyring_search_context *ctx)
852{
853 struct key *keyring;
854 long err;
855
856 ctx->iterator = keyring_search_iterator;
857 ctx->possessed = is_key_possessed(keyring_ref);
858 ctx->result = ERR_PTR(-EAGAIN);
859
860 keyring = key_ref_to_ptr(keyring_ref);
861 key_check(keyring);
862
863 if (keyring->type != &key_type_keyring)
864 return ERR_PTR(-ENOTDIR);
865
866 if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
867 err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
868 if (err < 0)
869 return ERR_PTR(err);
870 }
871
872 rcu_read_lock();
873 ctx->now = current_kernel_time();
874 if (search_nested_keyrings(keyring, ctx))
875 __key_get(key_ref_to_ptr(ctx->result));
876 rcu_read_unlock();
877 return ctx->result;
878}
879
880/**
881 * keyring_search - Search the supplied keyring tree for a matching key
882 * @keyring: The root of the keyring tree to be searched.
883 * @type: The type of keyring we want to find.
884 * @description: The name of the keyring we want to find.
885 *
886 * As keyring_search_aux() above, but using the current task's credentials and
887 * type's default matching function and preferred search method.
888 */
889key_ref_t keyring_search(key_ref_t keyring,
890 struct key_type *type,
891 const char *description)
892{
893 struct keyring_search_context ctx = {
894 .index_key.type = type,
895 .index_key.description = description,
896 .cred = current_cred(),
897 .match_data.cmp = key_default_cmp,
898 .match_data.raw_data = description,
899 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
900 .flags = KEYRING_SEARCH_DO_STATE_CHECK,
901 };
902 key_ref_t key;
903 int ret;
904
905 if (type->match_preparse) {
906 ret = type->match_preparse(&ctx.match_data);
907 if (ret < 0)
908 return ERR_PTR(ret);
909 }
910
911 key = keyring_search_aux(keyring, &ctx);
912
913 if (type->match_free)
914 type->match_free(&ctx.match_data);
915 return key;
916}
917EXPORT_SYMBOL(keyring_search);
918
919/*
920 * Search the given keyring for a key that might be updated.
921 *
922 * The caller must guarantee that the keyring is a keyring and that the
923 * permission is granted to modify the keyring as no check is made here. The
924 * caller must also hold a lock on the keyring semaphore.
925 *
926 * Returns a pointer to the found key with usage count incremented if
927 * successful and returns NULL if not found. Revoked and invalidated keys are
928 * skipped over.
929 *
930 * If successful, the possession indicator is propagated from the keyring ref
931 * to the returned key reference.
932 */
933key_ref_t find_key_to_update(key_ref_t keyring_ref,
934 const struct keyring_index_key *index_key)
935{
936 struct key *keyring, *key;
937 const void *object;
938
939 keyring = key_ref_to_ptr(keyring_ref);
940
941 kenter("{%d},{%s,%s}",
942 keyring->serial, index_key->type->name, index_key->description);
943
944 object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
945 index_key);
946
947 if (object)
948 goto found;
949
950 kleave(" = NULL");
951 return NULL;
952
953found:
954 key = keyring_ptr_to_key(object);
955 if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
956 (1 << KEY_FLAG_REVOKED))) {
957 kleave(" = NULL [x]");
958 return NULL;
959 }
960 __key_get(key);
961 kleave(" = {%d}", key->serial);
962 return make_key_ref(key, is_key_possessed(keyring_ref));
963}
964
965/*
966 * Find a keyring with the specified name.
967 *
968 * All named keyrings in the current user namespace are searched, provided they
969 * grant Search permission directly to the caller (unless this check is
970 * skipped). Keyrings whose usage points have reached zero or who have been
971 * revoked are skipped.
972 *
973 * Returns a pointer to the keyring with the keyring's refcount having being
974 * incremented on success. -ENOKEY is returned if a key could not be found.
975 */
976struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
977{
978 struct key *keyring;
979 int bucket;
980
981 if (!name)
982 return ERR_PTR(-EINVAL);
983
984 bucket = keyring_hash(name);
985
986 read_lock(&keyring_name_lock);
987
988 if (keyring_name_hash[bucket].next) {
989 /* search this hash bucket for a keyring with a matching name
990 * that's readable and that hasn't been revoked */
991 list_for_each_entry(keyring,
992 &keyring_name_hash[bucket],
993 name_link
994 ) {
995 if (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
996 continue;
997
998 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
999 continue;
1000
1001 if (strcmp(keyring->description, name) != 0)
1002 continue;
1003
1004 if (!skip_perm_check &&
1005 key_permission(make_key_ref(keyring, 0),
1006 KEY_NEED_SEARCH) < 0)
1007 continue;
1008
1009 /* we've got a match but we might end up racing with
1010 * key_cleanup() if the keyring is currently 'dead'
1011 * (ie. it has a zero usage count) */
1012 if (!atomic_inc_not_zero(&keyring->usage))
1013 continue;
1014 keyring->last_used_at = current_kernel_time().tv_sec;
1015 goto out;
1016 }
1017 }
1018
1019 keyring = ERR_PTR(-ENOKEY);
1020out:
1021 read_unlock(&keyring_name_lock);
1022 return keyring;
1023}
1024
1025static int keyring_detect_cycle_iterator(const void *object,
1026 void *iterator_data)
1027{
1028 struct keyring_search_context *ctx = iterator_data;
1029 const struct key *key = keyring_ptr_to_key(object);
1030
1031 kenter("{%d}", key->serial);
1032
1033 /* We might get a keyring with matching index-key that is nonetheless a
1034 * different keyring. */
1035 if (key != ctx->match_data.raw_data)
1036 return 0;
1037
1038 ctx->result = ERR_PTR(-EDEADLK);
1039 return 1;
1040}
1041
1042/*
1043 * See if a cycle will will be created by inserting acyclic tree B in acyclic
1044 * tree A at the topmost level (ie: as a direct child of A).
1045 *
1046 * Since we are adding B to A at the top level, checking for cycles should just
1047 * be a matter of seeing if node A is somewhere in tree B.
1048 */
1049static int keyring_detect_cycle(struct key *A, struct key *B)
1050{
1051 struct keyring_search_context ctx = {
1052 .index_key = A->index_key,
1053 .match_data.raw_data = A,
1054 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
1055 .iterator = keyring_detect_cycle_iterator,
1056 .flags = (KEYRING_SEARCH_NO_STATE_CHECK |
1057 KEYRING_SEARCH_NO_UPDATE_TIME |
1058 KEYRING_SEARCH_NO_CHECK_PERM |
1059 KEYRING_SEARCH_DETECT_TOO_DEEP),
1060 };
1061
1062 rcu_read_lock();
1063 search_nested_keyrings(B, &ctx);
1064 rcu_read_unlock();
1065 return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
1066}
1067
1068/*
1069 * Preallocate memory so that a key can be linked into to a keyring.
1070 */
1071int __key_link_begin(struct key *keyring,
1072 const struct keyring_index_key *index_key,
1073 struct assoc_array_edit **_edit)
1074 __acquires(&keyring->sem)
1075 __acquires(&keyring_serialise_link_sem)
1076{
1077 struct assoc_array_edit *edit;
1078 int ret;
1079
1080 kenter("%d,%s,%s,",
1081 keyring->serial, index_key->type->name, index_key->description);
1082
1083 BUG_ON(index_key->desc_len == 0);
1084
1085 if (keyring->type != &key_type_keyring)
1086 return -ENOTDIR;
1087
1088 down_write(&keyring->sem);
1089
1090 ret = -EKEYREVOKED;
1091 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
1092 goto error_krsem;
1093
1094 /* serialise link/link calls to prevent parallel calls causing a cycle
1095 * when linking two keyring in opposite orders */
1096 if (index_key->type == &key_type_keyring)
1097 down_write(&keyring_serialise_link_sem);
1098
1099 /* Create an edit script that will insert/replace the key in the
1100 * keyring tree.
1101 */
1102 edit = assoc_array_insert(&keyring->keys,
1103 &keyring_assoc_array_ops,
1104 index_key,
1105 NULL);
1106 if (IS_ERR(edit)) {
1107 ret = PTR_ERR(edit);
1108 goto error_sem;
1109 }
1110
1111 /* If we're not replacing a link in-place then we're going to need some
1112 * extra quota.
1113 */
1114 if (!edit->dead_leaf) {
1115 ret = key_payload_reserve(keyring,
1116 keyring->datalen + KEYQUOTA_LINK_BYTES);
1117 if (ret < 0)
1118 goto error_cancel;
1119 }
1120
1121 *_edit = edit;
1122 kleave(" = 0");
1123 return 0;
1124
1125error_cancel:
1126 assoc_array_cancel_edit(edit);
1127error_sem:
1128 if (index_key->type == &key_type_keyring)
1129 up_write(&keyring_serialise_link_sem);
1130error_krsem:
1131 up_write(&keyring->sem);
1132 kleave(" = %d", ret);
1133 return ret;
1134}
1135
1136/*
1137 * Check already instantiated keys aren't going to be a problem.
1138 *
1139 * The caller must have called __key_link_begin(). Don't need to call this for
1140 * keys that were created since __key_link_begin() was called.
1141 */
1142int __key_link_check_live_key(struct key *keyring, struct key *key)
1143{
1144 if (key->type == &key_type_keyring)
1145 /* check that we aren't going to create a cycle by linking one
1146 * keyring to another */
1147 return keyring_detect_cycle(keyring, key);
1148 return 0;
1149}
1150
1151/*
1152 * Link a key into to a keyring.
1153 *
1154 * Must be called with __key_link_begin() having being called. Discards any
1155 * already extant link to matching key if there is one, so that each keyring
1156 * holds at most one link to any given key of a particular type+description
1157 * combination.
1158 */
1159void __key_link(struct key *key, struct assoc_array_edit **_edit)
1160{
1161 __key_get(key);
1162 assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
1163 assoc_array_apply_edit(*_edit);
1164 *_edit = NULL;
1165}
1166
1167/*
1168 * Finish linking a key into to a keyring.
1169 *
1170 * Must be called with __key_link_begin() having being called.
1171 */
1172void __key_link_end(struct key *keyring,
1173 const struct keyring_index_key *index_key,
1174 struct assoc_array_edit *edit)
1175 __releases(&keyring->sem)
1176 __releases(&keyring_serialise_link_sem)
1177{
1178 BUG_ON(index_key->type == NULL);
1179 kenter("%d,%s,", keyring->serial, index_key->type->name);
1180
1181 if (index_key->type == &key_type_keyring)
1182 up_write(&keyring_serialise_link_sem);
1183
1184 if (edit) {
1185 if (!edit->dead_leaf) {
1186 key_payload_reserve(keyring,
1187 keyring->datalen - KEYQUOTA_LINK_BYTES);
1188 }
1189 assoc_array_cancel_edit(edit);
1190 }
1191 up_write(&keyring->sem);
1192}
1193
1194/**
1195 * key_link - Link a key to a keyring
1196 * @keyring: The keyring to make the link in.
1197 * @key: The key to link to.
1198 *
1199 * Make a link in a keyring to a key, such that the keyring holds a reference
1200 * on that key and the key can potentially be found by searching that keyring.
1201 *
1202 * This function will write-lock the keyring's semaphore and will consume some
1203 * of the user's key data quota to hold the link.
1204 *
1205 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
1206 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
1207 * full, -EDQUOT if there is insufficient key data quota remaining to add
1208 * another link or -ENOMEM if there's insufficient memory.
1209 *
1210 * It is assumed that the caller has checked that it is permitted for a link to
1211 * be made (the keyring should have Write permission and the key Link
1212 * permission).
1213 */
1214int key_link(struct key *keyring, struct key *key)
1215{
1216 struct assoc_array_edit *edit;
1217 int ret;
1218
1219 kenter("{%d,%d}", keyring->serial, atomic_read(&keyring->usage));
1220
1221 key_check(keyring);
1222 key_check(key);
1223
1224 if (test_bit(KEY_FLAG_TRUSTED_ONLY, &keyring->flags) &&
1225 !test_bit(KEY_FLAG_TRUSTED, &key->flags))
1226 return -EPERM;
1227
1228 ret = __key_link_begin(keyring, &key->index_key, &edit);
1229 if (ret == 0) {
1230 kdebug("begun {%d,%d}", keyring->serial, atomic_read(&keyring->usage));
1231 ret = __key_link_check_live_key(keyring, key);
1232 if (ret == 0)
1233 __key_link(key, &edit);
1234 __key_link_end(keyring, &key->index_key, edit);
1235 }
1236
1237 kleave(" = %d {%d,%d}", ret, keyring->serial, atomic_read(&keyring->usage));
1238 return ret;
1239}
1240EXPORT_SYMBOL(key_link);
1241
1242/**
1243 * key_unlink - Unlink the first link to a key from a keyring.
1244 * @keyring: The keyring to remove the link from.
1245 * @key: The key the link is to.
1246 *
1247 * Remove a link from a keyring to a key.
1248 *
1249 * This function will write-lock the keyring's semaphore.
1250 *
1251 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1252 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1253 * memory.
1254 *
1255 * It is assumed that the caller has checked that it is permitted for a link to
1256 * be removed (the keyring should have Write permission; no permissions are
1257 * required on the key).
1258 */
1259int key_unlink(struct key *keyring, struct key *key)
1260{
1261 struct assoc_array_edit *edit;
1262 int ret;
1263
1264 key_check(keyring);
1265 key_check(key);
1266
1267 if (keyring->type != &key_type_keyring)
1268 return -ENOTDIR;
1269
1270 down_write(&keyring->sem);
1271
1272 edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
1273 &key->index_key);
1274 if (IS_ERR(edit)) {
1275 ret = PTR_ERR(edit);
1276 goto error;
1277 }
1278 ret = -ENOENT;
1279 if (edit == NULL)
1280 goto error;
1281
1282 assoc_array_apply_edit(edit);
1283 key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
1284 ret = 0;
1285
1286error:
1287 up_write(&keyring->sem);
1288 return ret;
1289}
1290EXPORT_SYMBOL(key_unlink);
1291
1292/**
1293 * keyring_clear - Clear a keyring
1294 * @keyring: The keyring to clear.
1295 *
1296 * Clear the contents of the specified keyring.
1297 *
1298 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1299 */
1300int keyring_clear(struct key *keyring)
1301{
1302 struct assoc_array_edit *edit;
1303 int ret;
1304
1305 if (keyring->type != &key_type_keyring)
1306 return -ENOTDIR;
1307
1308 down_write(&keyring->sem);
1309
1310 edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1311 if (IS_ERR(edit)) {
1312 ret = PTR_ERR(edit);
1313 } else {
1314 if (edit)
1315 assoc_array_apply_edit(edit);
1316 key_payload_reserve(keyring, 0);
1317 ret = 0;
1318 }
1319
1320 up_write(&keyring->sem);
1321 return ret;
1322}
1323EXPORT_SYMBOL(keyring_clear);
1324
1325/*
1326 * Dispose of the links from a revoked keyring.
1327 *
1328 * This is called with the key sem write-locked.
1329 */
1330static void keyring_revoke(struct key *keyring)
1331{
1332 struct assoc_array_edit *edit;
1333
1334 edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
1335 if (!IS_ERR(edit)) {
1336 if (edit)
1337 assoc_array_apply_edit(edit);
1338 key_payload_reserve(keyring, 0);
1339 }
1340}
1341
1342static bool keyring_gc_select_iterator(void *object, void *iterator_data)
1343{
1344 struct key *key = keyring_ptr_to_key(object);
1345 time_t *limit = iterator_data;
1346
1347 if (key_is_dead(key, *limit))
1348 return false;
1349 key_get(key);
1350 return true;
1351}
1352
1353static int keyring_gc_check_iterator(const void *object, void *iterator_data)
1354{
1355 const struct key *key = keyring_ptr_to_key(object);
1356 time_t *limit = iterator_data;
1357
1358 key_check(key);
1359 return key_is_dead(key, *limit);
1360}
1361
1362/*
1363 * Garbage collect pointers from a keyring.
1364 *
1365 * Not called with any locks held. The keyring's key struct will not be
1366 * deallocated under us as only our caller may deallocate it.
1367 */
1368void keyring_gc(struct key *keyring, time_t limit)
1369{
1370 int result;
1371
1372 kenter("%x{%s}", keyring->serial, keyring->description ?: "");
1373
1374 if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
1375 (1 << KEY_FLAG_REVOKED)))
1376 goto dont_gc;
1377
1378 /* scan the keyring looking for dead keys */
1379 rcu_read_lock();
1380 result = assoc_array_iterate(&keyring->keys,
1381 keyring_gc_check_iterator, &limit);
1382 rcu_read_unlock();
1383 if (result == true)
1384 goto do_gc;
1385
1386dont_gc:
1387 kleave(" [no gc]");
1388 return;
1389
1390do_gc:
1391 down_write(&keyring->sem);
1392 assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
1393 keyring_gc_select_iterator, &limit);
1394 up_write(&keyring->sem);
1395 kleave(" [gc]");
1396}
1/* Keyring handling
2 *
3 * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/sched.h>
15#include <linux/slab.h>
16#include <linux/security.h>
17#include <linux/seq_file.h>
18#include <linux/err.h>
19#include <keys/keyring-type.h>
20#include <linux/uaccess.h>
21#include "internal.h"
22
23#define rcu_dereference_locked_keyring(keyring) \
24 (rcu_dereference_protected( \
25 (keyring)->payload.subscriptions, \
26 rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
27
28#define rcu_deref_link_locked(klist, index, keyring) \
29 (rcu_dereference_protected( \
30 (klist)->keys[index], \
31 rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
32
33#define MAX_KEYRING_LINKS \
34 min_t(size_t, USHRT_MAX - 1, \
35 ((PAGE_SIZE - sizeof(struct keyring_list)) / sizeof(struct key *)))
36
37#define KEY_LINK_FIXQUOTA 1UL
38
39/*
40 * When plumbing the depths of the key tree, this sets a hard limit
41 * set on how deep we're willing to go.
42 */
43#define KEYRING_SEARCH_MAX_DEPTH 6
44
45/*
46 * We keep all named keyrings in a hash to speed looking them up.
47 */
48#define KEYRING_NAME_HASH_SIZE (1 << 5)
49
50static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
51static DEFINE_RWLOCK(keyring_name_lock);
52
53static inline unsigned keyring_hash(const char *desc)
54{
55 unsigned bucket = 0;
56
57 for (; *desc; desc++)
58 bucket += (unsigned char)*desc;
59
60 return bucket & (KEYRING_NAME_HASH_SIZE - 1);
61}
62
63/*
64 * The keyring key type definition. Keyrings are simply keys of this type and
65 * can be treated as ordinary keys in addition to having their own special
66 * operations.
67 */
68static int keyring_instantiate(struct key *keyring,
69 const void *data, size_t datalen);
70static int keyring_match(const struct key *keyring, const void *criterion);
71static void keyring_revoke(struct key *keyring);
72static void keyring_destroy(struct key *keyring);
73static void keyring_describe(const struct key *keyring, struct seq_file *m);
74static long keyring_read(const struct key *keyring,
75 char __user *buffer, size_t buflen);
76
77struct key_type key_type_keyring = {
78 .name = "keyring",
79 .def_datalen = sizeof(struct keyring_list),
80 .instantiate = keyring_instantiate,
81 .match = keyring_match,
82 .revoke = keyring_revoke,
83 .destroy = keyring_destroy,
84 .describe = keyring_describe,
85 .read = keyring_read,
86};
87EXPORT_SYMBOL(key_type_keyring);
88
89/*
90 * Semaphore to serialise link/link calls to prevent two link calls in parallel
91 * introducing a cycle.
92 */
93static DECLARE_RWSEM(keyring_serialise_link_sem);
94
95/*
96 * Publish the name of a keyring so that it can be found by name (if it has
97 * one).
98 */
99static void keyring_publish_name(struct key *keyring)
100{
101 int bucket;
102
103 if (keyring->description) {
104 bucket = keyring_hash(keyring->description);
105
106 write_lock(&keyring_name_lock);
107
108 if (!keyring_name_hash[bucket].next)
109 INIT_LIST_HEAD(&keyring_name_hash[bucket]);
110
111 list_add_tail(&keyring->type_data.link,
112 &keyring_name_hash[bucket]);
113
114 write_unlock(&keyring_name_lock);
115 }
116}
117
118/*
119 * Initialise a keyring.
120 *
121 * Returns 0 on success, -EINVAL if given any data.
122 */
123static int keyring_instantiate(struct key *keyring,
124 const void *data, size_t datalen)
125{
126 int ret;
127
128 ret = -EINVAL;
129 if (datalen == 0) {
130 /* make the keyring available by name if it has one */
131 keyring_publish_name(keyring);
132 ret = 0;
133 }
134
135 return ret;
136}
137
138/*
139 * Match keyrings on their name
140 */
141static int keyring_match(const struct key *keyring, const void *description)
142{
143 return keyring->description &&
144 strcmp(keyring->description, description) == 0;
145}
146
147/*
148 * Clean up a keyring when it is destroyed. Unpublish its name if it had one
149 * and dispose of its data.
150 *
151 * The garbage collector detects the final key_put(), removes the keyring from
152 * the serial number tree and then does RCU synchronisation before coming here,
153 * so we shouldn't need to worry about code poking around here with the RCU
154 * readlock held by this time.
155 */
156static void keyring_destroy(struct key *keyring)
157{
158 struct keyring_list *klist;
159 int loop;
160
161 if (keyring->description) {
162 write_lock(&keyring_name_lock);
163
164 if (keyring->type_data.link.next != NULL &&
165 !list_empty(&keyring->type_data.link))
166 list_del(&keyring->type_data.link);
167
168 write_unlock(&keyring_name_lock);
169 }
170
171 klist = rcu_access_pointer(keyring->payload.subscriptions);
172 if (klist) {
173 for (loop = klist->nkeys - 1; loop >= 0; loop--)
174 key_put(rcu_access_pointer(klist->keys[loop]));
175 kfree(klist);
176 }
177}
178
179/*
180 * Describe a keyring for /proc.
181 */
182static void keyring_describe(const struct key *keyring, struct seq_file *m)
183{
184 struct keyring_list *klist;
185
186 if (keyring->description)
187 seq_puts(m, keyring->description);
188 else
189 seq_puts(m, "[anon]");
190
191 if (key_is_instantiated(keyring)) {
192 rcu_read_lock();
193 klist = rcu_dereference(keyring->payload.subscriptions);
194 if (klist)
195 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
196 else
197 seq_puts(m, ": empty");
198 rcu_read_unlock();
199 }
200}
201
202/*
203 * Read a list of key IDs from the keyring's contents in binary form
204 *
205 * The keyring's semaphore is read-locked by the caller.
206 */
207static long keyring_read(const struct key *keyring,
208 char __user *buffer, size_t buflen)
209{
210 struct keyring_list *klist;
211 struct key *key;
212 size_t qty, tmp;
213 int loop, ret;
214
215 ret = 0;
216 klist = rcu_dereference_locked_keyring(keyring);
217 if (klist) {
218 /* calculate how much data we could return */
219 qty = klist->nkeys * sizeof(key_serial_t);
220
221 if (buffer && buflen > 0) {
222 if (buflen > qty)
223 buflen = qty;
224
225 /* copy the IDs of the subscribed keys into the
226 * buffer */
227 ret = -EFAULT;
228
229 for (loop = 0; loop < klist->nkeys; loop++) {
230 key = rcu_deref_link_locked(klist, loop,
231 keyring);
232
233 tmp = sizeof(key_serial_t);
234 if (tmp > buflen)
235 tmp = buflen;
236
237 if (copy_to_user(buffer,
238 &key->serial,
239 tmp) != 0)
240 goto error;
241
242 buflen -= tmp;
243 if (buflen == 0)
244 break;
245 buffer += tmp;
246 }
247 }
248
249 ret = qty;
250 }
251
252error:
253 return ret;
254}
255
256/*
257 * Allocate a keyring and link into the destination keyring.
258 */
259struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
260 const struct cred *cred, unsigned long flags,
261 struct key *dest)
262{
263 struct key *keyring;
264 int ret;
265
266 keyring = key_alloc(&key_type_keyring, description,
267 uid, gid, cred,
268 (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
269 flags);
270
271 if (!IS_ERR(keyring)) {
272 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
273 if (ret < 0) {
274 key_put(keyring);
275 keyring = ERR_PTR(ret);
276 }
277 }
278
279 return keyring;
280}
281
282/**
283 * keyring_search_aux - Search a keyring tree for a key matching some criteria
284 * @keyring_ref: A pointer to the keyring with possession indicator.
285 * @cred: The credentials to use for permissions checks.
286 * @type: The type of key to search for.
287 * @description: Parameter for @match.
288 * @match: Function to rule on whether or not a key is the one required.
289 * @no_state_check: Don't check if a matching key is bad
290 *
291 * Search the supplied keyring tree for a key that matches the criteria given.
292 * The root keyring and any linked keyrings must grant Search permission to the
293 * caller to be searchable and keys can only be found if they too grant Search
294 * to the caller. The possession flag on the root keyring pointer controls use
295 * of the possessor bits in permissions checking of the entire tree. In
296 * addition, the LSM gets to forbid keyring searches and key matches.
297 *
298 * The search is performed as a breadth-then-depth search up to the prescribed
299 * limit (KEYRING_SEARCH_MAX_DEPTH).
300 *
301 * Keys are matched to the type provided and are then filtered by the match
302 * function, which is given the description to use in any way it sees fit. The
303 * match function may use any attributes of a key that it wishes to to
304 * determine the match. Normally the match function from the key type would be
305 * used.
306 *
307 * RCU is used to prevent the keyring key lists from disappearing without the
308 * need to take lots of locks.
309 *
310 * Returns a pointer to the found key and increments the key usage count if
311 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
312 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
313 * specified keyring wasn't a keyring.
314 *
315 * In the case of a successful return, the possession attribute from
316 * @keyring_ref is propagated to the returned key reference.
317 */
318key_ref_t keyring_search_aux(key_ref_t keyring_ref,
319 const struct cred *cred,
320 struct key_type *type,
321 const void *description,
322 key_match_func_t match,
323 bool no_state_check)
324{
325 struct {
326 /* Need a separate keylist pointer for RCU purposes */
327 struct key *keyring;
328 struct keyring_list *keylist;
329 int kix;
330 } stack[KEYRING_SEARCH_MAX_DEPTH];
331
332 struct keyring_list *keylist;
333 struct timespec now;
334 unsigned long possessed, kflags;
335 struct key *keyring, *key;
336 key_ref_t key_ref;
337 long err;
338 int sp, nkeys, kix;
339
340 keyring = key_ref_to_ptr(keyring_ref);
341 possessed = is_key_possessed(keyring_ref);
342 key_check(keyring);
343
344 /* top keyring must have search permission to begin the search */
345 err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
346 if (err < 0) {
347 key_ref = ERR_PTR(err);
348 goto error;
349 }
350
351 key_ref = ERR_PTR(-ENOTDIR);
352 if (keyring->type != &key_type_keyring)
353 goto error;
354
355 rcu_read_lock();
356
357 now = current_kernel_time();
358 err = -EAGAIN;
359 sp = 0;
360
361 /* firstly we should check to see if this top-level keyring is what we
362 * are looking for */
363 key_ref = ERR_PTR(-EAGAIN);
364 kflags = keyring->flags;
365 if (keyring->type == type && match(keyring, description)) {
366 key = keyring;
367 if (no_state_check)
368 goto found;
369
370 /* check it isn't negative and hasn't expired or been
371 * revoked */
372 if (kflags & (1 << KEY_FLAG_REVOKED))
373 goto error_2;
374 if (key->expiry && now.tv_sec >= key->expiry)
375 goto error_2;
376 key_ref = ERR_PTR(key->type_data.reject_error);
377 if (kflags & (1 << KEY_FLAG_NEGATIVE))
378 goto error_2;
379 goto found;
380 }
381
382 /* otherwise, the top keyring must not be revoked, expired, or
383 * negatively instantiated if we are to search it */
384 key_ref = ERR_PTR(-EAGAIN);
385 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
386 (1 << KEY_FLAG_REVOKED) |
387 (1 << KEY_FLAG_NEGATIVE)) ||
388 (keyring->expiry && now.tv_sec >= keyring->expiry))
389 goto error_2;
390
391 /* start processing a new keyring */
392descend:
393 kflags = keyring->flags;
394 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
395 (1 << KEY_FLAG_REVOKED)))
396 goto not_this_keyring;
397
398 keylist = rcu_dereference(keyring->payload.subscriptions);
399 if (!keylist)
400 goto not_this_keyring;
401
402 /* iterate through the keys in this keyring first */
403 nkeys = keylist->nkeys;
404 smp_rmb();
405 for (kix = 0; kix < nkeys; kix++) {
406 key = rcu_dereference(keylist->keys[kix]);
407 kflags = key->flags;
408
409 /* ignore keys not of this type */
410 if (key->type != type)
411 continue;
412
413 /* skip invalidated, revoked and expired keys */
414 if (!no_state_check) {
415 if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
416 (1 << KEY_FLAG_REVOKED)))
417 continue;
418
419 if (key->expiry && now.tv_sec >= key->expiry)
420 continue;
421 }
422
423 /* keys that don't match */
424 if (!match(key, description))
425 continue;
426
427 /* key must have search permissions */
428 if (key_task_permission(make_key_ref(key, possessed),
429 cred, KEY_SEARCH) < 0)
430 continue;
431
432 if (no_state_check)
433 goto found;
434
435 /* we set a different error code if we pass a negative key */
436 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
437 err = key->type_data.reject_error;
438 continue;
439 }
440
441 goto found;
442 }
443
444 /* search through the keyrings nested in this one */
445 kix = 0;
446ascend:
447 nkeys = keylist->nkeys;
448 smp_rmb();
449 for (; kix < nkeys; kix++) {
450 key = rcu_dereference(keylist->keys[kix]);
451 if (key->type != &key_type_keyring)
452 continue;
453
454 /* recursively search nested keyrings
455 * - only search keyrings for which we have search permission
456 */
457 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
458 continue;
459
460 if (key_task_permission(make_key_ref(key, possessed),
461 cred, KEY_SEARCH) < 0)
462 continue;
463
464 /* stack the current position */
465 stack[sp].keyring = keyring;
466 stack[sp].keylist = keylist;
467 stack[sp].kix = kix;
468 sp++;
469
470 /* begin again with the new keyring */
471 keyring = key;
472 goto descend;
473 }
474
475 /* the keyring we're looking at was disqualified or didn't contain a
476 * matching key */
477not_this_keyring:
478 if (sp > 0) {
479 /* resume the processing of a keyring higher up in the tree */
480 sp--;
481 keyring = stack[sp].keyring;
482 keylist = stack[sp].keylist;
483 kix = stack[sp].kix + 1;
484 goto ascend;
485 }
486
487 key_ref = ERR_PTR(err);
488 goto error_2;
489
490 /* we found a viable match */
491found:
492 atomic_inc(&key->usage);
493 key->last_used_at = now.tv_sec;
494 keyring->last_used_at = now.tv_sec;
495 while (sp > 0)
496 stack[--sp].keyring->last_used_at = now.tv_sec;
497 key_check(key);
498 key_ref = make_key_ref(key, possessed);
499error_2:
500 rcu_read_unlock();
501error:
502 return key_ref;
503}
504
505/**
506 * keyring_search - Search the supplied keyring tree for a matching key
507 * @keyring: The root of the keyring tree to be searched.
508 * @type: The type of keyring we want to find.
509 * @description: The name of the keyring we want to find.
510 *
511 * As keyring_search_aux() above, but using the current task's credentials and
512 * type's default matching function.
513 */
514key_ref_t keyring_search(key_ref_t keyring,
515 struct key_type *type,
516 const char *description)
517{
518 if (!type->match)
519 return ERR_PTR(-ENOKEY);
520
521 return keyring_search_aux(keyring, current->cred,
522 type, description, type->match, false);
523}
524EXPORT_SYMBOL(keyring_search);
525
526/*
527 * Search the given keyring only (no recursion).
528 *
529 * The caller must guarantee that the keyring is a keyring and that the
530 * permission is granted to search the keyring as no check is made here.
531 *
532 * RCU is used to make it unnecessary to lock the keyring key list here.
533 *
534 * Returns a pointer to the found key with usage count incremented if
535 * successful and returns -ENOKEY if not found. Revoked keys and keys not
536 * providing the requested permission are skipped over.
537 *
538 * If successful, the possession indicator is propagated from the keyring ref
539 * to the returned key reference.
540 */
541key_ref_t __keyring_search_one(key_ref_t keyring_ref,
542 const struct key_type *ktype,
543 const char *description,
544 key_perm_t perm)
545{
546 struct keyring_list *klist;
547 unsigned long possessed;
548 struct key *keyring, *key;
549 int nkeys, loop;
550
551 keyring = key_ref_to_ptr(keyring_ref);
552 possessed = is_key_possessed(keyring_ref);
553
554 rcu_read_lock();
555
556 klist = rcu_dereference(keyring->payload.subscriptions);
557 if (klist) {
558 nkeys = klist->nkeys;
559 smp_rmb();
560 for (loop = 0; loop < nkeys ; loop++) {
561 key = rcu_dereference(klist->keys[loop]);
562 if (key->type == ktype &&
563 (!key->type->match ||
564 key->type->match(key, description)) &&
565 key_permission(make_key_ref(key, possessed),
566 perm) == 0 &&
567 !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
568 (1 << KEY_FLAG_REVOKED)))
569 )
570 goto found;
571 }
572 }
573
574 rcu_read_unlock();
575 return ERR_PTR(-ENOKEY);
576
577found:
578 atomic_inc(&key->usage);
579 keyring->last_used_at = key->last_used_at =
580 current_kernel_time().tv_sec;
581 rcu_read_unlock();
582 return make_key_ref(key, possessed);
583}
584
585/*
586 * Find a keyring with the specified name.
587 *
588 * All named keyrings in the current user namespace are searched, provided they
589 * grant Search permission directly to the caller (unless this check is
590 * skipped). Keyrings whose usage points have reached zero or who have been
591 * revoked are skipped.
592 *
593 * Returns a pointer to the keyring with the keyring's refcount having being
594 * incremented on success. -ENOKEY is returned if a key could not be found.
595 */
596struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
597{
598 struct key *keyring;
599 int bucket;
600
601 if (!name)
602 return ERR_PTR(-EINVAL);
603
604 bucket = keyring_hash(name);
605
606 read_lock(&keyring_name_lock);
607
608 if (keyring_name_hash[bucket].next) {
609 /* search this hash bucket for a keyring with a matching name
610 * that's readable and that hasn't been revoked */
611 list_for_each_entry(keyring,
612 &keyring_name_hash[bucket],
613 type_data.link
614 ) {
615 if (keyring->user->user_ns != current_user_ns())
616 continue;
617
618 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
619 continue;
620
621 if (strcmp(keyring->description, name) != 0)
622 continue;
623
624 if (!skip_perm_check &&
625 key_permission(make_key_ref(keyring, 0),
626 KEY_SEARCH) < 0)
627 continue;
628
629 /* we've got a match but we might end up racing with
630 * key_cleanup() if the keyring is currently 'dead'
631 * (ie. it has a zero usage count) */
632 if (!atomic_inc_not_zero(&keyring->usage))
633 continue;
634 keyring->last_used_at = current_kernel_time().tv_sec;
635 goto out;
636 }
637 }
638
639 keyring = ERR_PTR(-ENOKEY);
640out:
641 read_unlock(&keyring_name_lock);
642 return keyring;
643}
644
645/*
646 * See if a cycle will will be created by inserting acyclic tree B in acyclic
647 * tree A at the topmost level (ie: as a direct child of A).
648 *
649 * Since we are adding B to A at the top level, checking for cycles should just
650 * be a matter of seeing if node A is somewhere in tree B.
651 */
652static int keyring_detect_cycle(struct key *A, struct key *B)
653{
654 struct {
655 struct keyring_list *keylist;
656 int kix;
657 } stack[KEYRING_SEARCH_MAX_DEPTH];
658
659 struct keyring_list *keylist;
660 struct key *subtree, *key;
661 int sp, nkeys, kix, ret;
662
663 rcu_read_lock();
664
665 ret = -EDEADLK;
666 if (A == B)
667 goto cycle_detected;
668
669 subtree = B;
670 sp = 0;
671
672 /* start processing a new keyring */
673descend:
674 if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
675 goto not_this_keyring;
676
677 keylist = rcu_dereference(subtree->payload.subscriptions);
678 if (!keylist)
679 goto not_this_keyring;
680 kix = 0;
681
682ascend:
683 /* iterate through the remaining keys in this keyring */
684 nkeys = keylist->nkeys;
685 smp_rmb();
686 for (; kix < nkeys; kix++) {
687 key = rcu_dereference(keylist->keys[kix]);
688
689 if (key == A)
690 goto cycle_detected;
691
692 /* recursively check nested keyrings */
693 if (key->type == &key_type_keyring) {
694 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
695 goto too_deep;
696
697 /* stack the current position */
698 stack[sp].keylist = keylist;
699 stack[sp].kix = kix;
700 sp++;
701
702 /* begin again with the new keyring */
703 subtree = key;
704 goto descend;
705 }
706 }
707
708 /* the keyring we're looking at was disqualified or didn't contain a
709 * matching key */
710not_this_keyring:
711 if (sp > 0) {
712 /* resume the checking of a keyring higher up in the tree */
713 sp--;
714 keylist = stack[sp].keylist;
715 kix = stack[sp].kix + 1;
716 goto ascend;
717 }
718
719 ret = 0; /* no cycles detected */
720
721error:
722 rcu_read_unlock();
723 return ret;
724
725too_deep:
726 ret = -ELOOP;
727 goto error;
728
729cycle_detected:
730 ret = -EDEADLK;
731 goto error;
732}
733
734/*
735 * Dispose of a keyring list after the RCU grace period, freeing the unlinked
736 * key
737 */
738static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
739{
740 struct keyring_list *klist =
741 container_of(rcu, struct keyring_list, rcu);
742
743 if (klist->delkey != USHRT_MAX)
744 key_put(rcu_access_pointer(klist->keys[klist->delkey]));
745 kfree(klist);
746}
747
748/*
749 * Preallocate memory so that a key can be linked into to a keyring.
750 */
751int __key_link_begin(struct key *keyring, const struct key_type *type,
752 const char *description, unsigned long *_prealloc)
753 __acquires(&keyring->sem)
754{
755 struct keyring_list *klist, *nklist;
756 unsigned long prealloc;
757 unsigned max;
758 time_t lowest_lru;
759 size_t size;
760 int loop, lru, ret;
761
762 kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
763
764 if (keyring->type != &key_type_keyring)
765 return -ENOTDIR;
766
767 down_write(&keyring->sem);
768
769 ret = -EKEYREVOKED;
770 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
771 goto error_krsem;
772
773 /* serialise link/link calls to prevent parallel calls causing a cycle
774 * when linking two keyring in opposite orders */
775 if (type == &key_type_keyring)
776 down_write(&keyring_serialise_link_sem);
777
778 klist = rcu_dereference_locked_keyring(keyring);
779
780 /* see if there's a matching key we can displace */
781 lru = -1;
782 if (klist && klist->nkeys > 0) {
783 lowest_lru = TIME_T_MAX;
784 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
785 struct key *key = rcu_deref_link_locked(klist, loop,
786 keyring);
787 if (key->type == type &&
788 strcmp(key->description, description) == 0) {
789 /* Found a match - we'll replace the link with
790 * one to the new key. We record the slot
791 * position.
792 */
793 klist->delkey = loop;
794 prealloc = 0;
795 goto done;
796 }
797 if (key->last_used_at < lowest_lru) {
798 lowest_lru = key->last_used_at;
799 lru = loop;
800 }
801 }
802 }
803
804 /* If the keyring is full then do an LRU discard */
805 if (klist &&
806 klist->nkeys == klist->maxkeys &&
807 klist->maxkeys >= MAX_KEYRING_LINKS) {
808 kdebug("LRU discard %d\n", lru);
809 klist->delkey = lru;
810 prealloc = 0;
811 goto done;
812 }
813
814 /* check that we aren't going to overrun the user's quota */
815 ret = key_payload_reserve(keyring,
816 keyring->datalen + KEYQUOTA_LINK_BYTES);
817 if (ret < 0)
818 goto error_sem;
819
820 if (klist && klist->nkeys < klist->maxkeys) {
821 /* there's sufficient slack space to append directly */
822 klist->delkey = klist->nkeys;
823 prealloc = KEY_LINK_FIXQUOTA;
824 } else {
825 /* grow the key list */
826 max = 4;
827 if (klist) {
828 max += klist->maxkeys;
829 if (max > MAX_KEYRING_LINKS)
830 max = MAX_KEYRING_LINKS;
831 BUG_ON(max <= klist->maxkeys);
832 }
833
834 size = sizeof(*klist) + sizeof(struct key *) * max;
835
836 ret = -ENOMEM;
837 nklist = kmalloc(size, GFP_KERNEL);
838 if (!nklist)
839 goto error_quota;
840
841 nklist->maxkeys = max;
842 if (klist) {
843 memcpy(nklist->keys, klist->keys,
844 sizeof(struct key *) * klist->nkeys);
845 nklist->delkey = klist->nkeys;
846 nklist->nkeys = klist->nkeys + 1;
847 klist->delkey = USHRT_MAX;
848 } else {
849 nklist->nkeys = 1;
850 nklist->delkey = 0;
851 }
852
853 /* add the key into the new space */
854 RCU_INIT_POINTER(nklist->keys[nklist->delkey], NULL);
855 prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
856 }
857
858done:
859 *_prealloc = prealloc;
860 kleave(" = 0");
861 return 0;
862
863error_quota:
864 /* undo the quota changes */
865 key_payload_reserve(keyring,
866 keyring->datalen - KEYQUOTA_LINK_BYTES);
867error_sem:
868 if (type == &key_type_keyring)
869 up_write(&keyring_serialise_link_sem);
870error_krsem:
871 up_write(&keyring->sem);
872 kleave(" = %d", ret);
873 return ret;
874}
875
876/*
877 * Check already instantiated keys aren't going to be a problem.
878 *
879 * The caller must have called __key_link_begin(). Don't need to call this for
880 * keys that were created since __key_link_begin() was called.
881 */
882int __key_link_check_live_key(struct key *keyring, struct key *key)
883{
884 if (key->type == &key_type_keyring)
885 /* check that we aren't going to create a cycle by linking one
886 * keyring to another */
887 return keyring_detect_cycle(keyring, key);
888 return 0;
889}
890
891/*
892 * Link a key into to a keyring.
893 *
894 * Must be called with __key_link_begin() having being called. Discards any
895 * already extant link to matching key if there is one, so that each keyring
896 * holds at most one link to any given key of a particular type+description
897 * combination.
898 */
899void __key_link(struct key *keyring, struct key *key,
900 unsigned long *_prealloc)
901{
902 struct keyring_list *klist, *nklist;
903 struct key *discard;
904
905 nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
906 *_prealloc = 0;
907
908 kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
909
910 klist = rcu_dereference_locked_keyring(keyring);
911
912 atomic_inc(&key->usage);
913 keyring->last_used_at = key->last_used_at =
914 current_kernel_time().tv_sec;
915
916 /* there's a matching key we can displace or an empty slot in a newly
917 * allocated list we can fill */
918 if (nklist) {
919 kdebug("reissue %hu/%hu/%hu",
920 nklist->delkey, nklist->nkeys, nklist->maxkeys);
921
922 RCU_INIT_POINTER(nklist->keys[nklist->delkey], key);
923
924 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
925
926 /* dispose of the old keyring list and, if there was one, the
927 * displaced key */
928 if (klist) {
929 kdebug("dispose %hu/%hu/%hu",
930 klist->delkey, klist->nkeys, klist->maxkeys);
931 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
932 }
933 } else if (klist->delkey < klist->nkeys) {
934 kdebug("replace %hu/%hu/%hu",
935 klist->delkey, klist->nkeys, klist->maxkeys);
936
937 discard = rcu_dereference_protected(
938 klist->keys[klist->delkey],
939 rwsem_is_locked(&keyring->sem));
940 rcu_assign_pointer(klist->keys[klist->delkey], key);
941 /* The garbage collector will take care of RCU
942 * synchronisation */
943 key_put(discard);
944 } else {
945 /* there's sufficient slack space to append directly */
946 kdebug("append %hu/%hu/%hu",
947 klist->delkey, klist->nkeys, klist->maxkeys);
948
949 RCU_INIT_POINTER(klist->keys[klist->delkey], key);
950 smp_wmb();
951 klist->nkeys++;
952 }
953}
954
955/*
956 * Finish linking a key into to a keyring.
957 *
958 * Must be called with __key_link_begin() having being called.
959 */
960void __key_link_end(struct key *keyring, struct key_type *type,
961 unsigned long prealloc)
962 __releases(&keyring->sem)
963{
964 BUG_ON(type == NULL);
965 BUG_ON(type->name == NULL);
966 kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
967
968 if (type == &key_type_keyring)
969 up_write(&keyring_serialise_link_sem);
970
971 if (prealloc) {
972 if (prealloc & KEY_LINK_FIXQUOTA)
973 key_payload_reserve(keyring,
974 keyring->datalen -
975 KEYQUOTA_LINK_BYTES);
976 kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
977 }
978 up_write(&keyring->sem);
979}
980
981/**
982 * key_link - Link a key to a keyring
983 * @keyring: The keyring to make the link in.
984 * @key: The key to link to.
985 *
986 * Make a link in a keyring to a key, such that the keyring holds a reference
987 * on that key and the key can potentially be found by searching that keyring.
988 *
989 * This function will write-lock the keyring's semaphore and will consume some
990 * of the user's key data quota to hold the link.
991 *
992 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
993 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
994 * full, -EDQUOT if there is insufficient key data quota remaining to add
995 * another link or -ENOMEM if there's insufficient memory.
996 *
997 * It is assumed that the caller has checked that it is permitted for a link to
998 * be made (the keyring should have Write permission and the key Link
999 * permission).
1000 */
1001int key_link(struct key *keyring, struct key *key)
1002{
1003 unsigned long prealloc;
1004 int ret;
1005
1006 key_check(keyring);
1007 key_check(key);
1008
1009 ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
1010 if (ret == 0) {
1011 ret = __key_link_check_live_key(keyring, key);
1012 if (ret == 0)
1013 __key_link(keyring, key, &prealloc);
1014 __key_link_end(keyring, key->type, prealloc);
1015 }
1016
1017 return ret;
1018}
1019EXPORT_SYMBOL(key_link);
1020
1021/**
1022 * key_unlink - Unlink the first link to a key from a keyring.
1023 * @keyring: The keyring to remove the link from.
1024 * @key: The key the link is to.
1025 *
1026 * Remove a link from a keyring to a key.
1027 *
1028 * This function will write-lock the keyring's semaphore.
1029 *
1030 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1031 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1032 * memory.
1033 *
1034 * It is assumed that the caller has checked that it is permitted for a link to
1035 * be removed (the keyring should have Write permission; no permissions are
1036 * required on the key).
1037 */
1038int key_unlink(struct key *keyring, struct key *key)
1039{
1040 struct keyring_list *klist, *nklist;
1041 int loop, ret;
1042
1043 key_check(keyring);
1044 key_check(key);
1045
1046 ret = -ENOTDIR;
1047 if (keyring->type != &key_type_keyring)
1048 goto error;
1049
1050 down_write(&keyring->sem);
1051
1052 klist = rcu_dereference_locked_keyring(keyring);
1053 if (klist) {
1054 /* search the keyring for the key */
1055 for (loop = 0; loop < klist->nkeys; loop++)
1056 if (rcu_access_pointer(klist->keys[loop]) == key)
1057 goto key_is_present;
1058 }
1059
1060 up_write(&keyring->sem);
1061 ret = -ENOENT;
1062 goto error;
1063
1064key_is_present:
1065 /* we need to copy the key list for RCU purposes */
1066 nklist = kmalloc(sizeof(*klist) +
1067 sizeof(struct key *) * klist->maxkeys,
1068 GFP_KERNEL);
1069 if (!nklist)
1070 goto nomem;
1071 nklist->maxkeys = klist->maxkeys;
1072 nklist->nkeys = klist->nkeys - 1;
1073
1074 if (loop > 0)
1075 memcpy(&nklist->keys[0],
1076 &klist->keys[0],
1077 loop * sizeof(struct key *));
1078
1079 if (loop < nklist->nkeys)
1080 memcpy(&nklist->keys[loop],
1081 &klist->keys[loop + 1],
1082 (nklist->nkeys - loop) * sizeof(struct key *));
1083
1084 /* adjust the user's quota */
1085 key_payload_reserve(keyring,
1086 keyring->datalen - KEYQUOTA_LINK_BYTES);
1087
1088 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
1089
1090 up_write(&keyring->sem);
1091
1092 /* schedule for later cleanup */
1093 klist->delkey = loop;
1094 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
1095
1096 ret = 0;
1097
1098error:
1099 return ret;
1100nomem:
1101 ret = -ENOMEM;
1102 up_write(&keyring->sem);
1103 goto error;
1104}
1105EXPORT_SYMBOL(key_unlink);
1106
1107/*
1108 * Dispose of a keyring list after the RCU grace period, releasing the keys it
1109 * links to.
1110 */
1111static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
1112{
1113 struct keyring_list *klist;
1114 int loop;
1115
1116 klist = container_of(rcu, struct keyring_list, rcu);
1117
1118 for (loop = klist->nkeys - 1; loop >= 0; loop--)
1119 key_put(rcu_access_pointer(klist->keys[loop]));
1120
1121 kfree(klist);
1122}
1123
1124/**
1125 * keyring_clear - Clear a keyring
1126 * @keyring: The keyring to clear.
1127 *
1128 * Clear the contents of the specified keyring.
1129 *
1130 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1131 */
1132int keyring_clear(struct key *keyring)
1133{
1134 struct keyring_list *klist;
1135 int ret;
1136
1137 ret = -ENOTDIR;
1138 if (keyring->type == &key_type_keyring) {
1139 /* detach the pointer block with the locks held */
1140 down_write(&keyring->sem);
1141
1142 klist = rcu_dereference_locked_keyring(keyring);
1143 if (klist) {
1144 /* adjust the quota */
1145 key_payload_reserve(keyring,
1146 sizeof(struct keyring_list));
1147
1148 rcu_assign_pointer(keyring->payload.subscriptions,
1149 NULL);
1150 }
1151
1152 up_write(&keyring->sem);
1153
1154 /* free the keys after the locks have been dropped */
1155 if (klist)
1156 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1157
1158 ret = 0;
1159 }
1160
1161 return ret;
1162}
1163EXPORT_SYMBOL(keyring_clear);
1164
1165/*
1166 * Dispose of the links from a revoked keyring.
1167 *
1168 * This is called with the key sem write-locked.
1169 */
1170static void keyring_revoke(struct key *keyring)
1171{
1172 struct keyring_list *klist;
1173
1174 klist = rcu_dereference_locked_keyring(keyring);
1175
1176 /* adjust the quota */
1177 key_payload_reserve(keyring, 0);
1178
1179 if (klist) {
1180 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1181 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1182 }
1183}
1184
1185/*
1186 * Collect garbage from the contents of a keyring, replacing the old list with
1187 * a new one with the pointers all shuffled down.
1188 *
1189 * Dead keys are classed as oned that are flagged as being dead or are revoked,
1190 * expired or negative keys that were revoked or expired before the specified
1191 * limit.
1192 */
1193void keyring_gc(struct key *keyring, time_t limit)
1194{
1195 struct keyring_list *klist, *new;
1196 struct key *key;
1197 int loop, keep, max;
1198
1199 kenter("{%x,%s}", key_serial(keyring), keyring->description);
1200
1201 down_write(&keyring->sem);
1202
1203 klist = rcu_dereference_locked_keyring(keyring);
1204 if (!klist)
1205 goto no_klist;
1206
1207 /* work out how many subscriptions we're keeping */
1208 keep = 0;
1209 for (loop = klist->nkeys - 1; loop >= 0; loop--)
1210 if (!key_is_dead(rcu_deref_link_locked(klist, loop, keyring),
1211 limit))
1212 keep++;
1213
1214 if (keep == klist->nkeys)
1215 goto just_return;
1216
1217 /* allocate a new keyring payload */
1218 max = roundup(keep, 4);
1219 new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
1220 GFP_KERNEL);
1221 if (!new)
1222 goto nomem;
1223 new->maxkeys = max;
1224 new->nkeys = 0;
1225 new->delkey = 0;
1226
1227 /* install the live keys
1228 * - must take care as expired keys may be updated back to life
1229 */
1230 keep = 0;
1231 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
1232 key = rcu_deref_link_locked(klist, loop, keyring);
1233 if (!key_is_dead(key, limit)) {
1234 if (keep >= max)
1235 goto discard_new;
1236 RCU_INIT_POINTER(new->keys[keep++], key_get(key));
1237 }
1238 }
1239 new->nkeys = keep;
1240
1241 /* adjust the quota */
1242 key_payload_reserve(keyring,
1243 sizeof(struct keyring_list) +
1244 KEYQUOTA_LINK_BYTES * keep);
1245
1246 if (keep == 0) {
1247 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1248 kfree(new);
1249 } else {
1250 rcu_assign_pointer(keyring->payload.subscriptions, new);
1251 }
1252
1253 up_write(&keyring->sem);
1254
1255 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1256 kleave(" [yes]");
1257 return;
1258
1259discard_new:
1260 new->nkeys = keep;
1261 keyring_clear_rcu_disposal(&new->rcu);
1262 up_write(&keyring->sem);
1263 kleave(" [discard]");
1264 return;
1265
1266just_return:
1267 up_write(&keyring->sem);
1268 kleave(" [no dead]");
1269 return;
1270
1271no_klist:
1272 up_write(&keyring->sem);
1273 kleave(" [no_klist]");
1274 return;
1275
1276nomem:
1277 up_write(&keyring->sem);
1278 kleave(" [oom]");
1279}