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Linux/security/keys/keyring.c

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

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