Root/security/keys/key.c

Source at commit be977234bfb4a6dca8a39e7c52165e4cd536ad71 created 9 years 5 months ago.
By Lars-Peter Clausen, jz4740: Fix compile error
1/* Basic authentication token and access key management
2 *
3 * Copyright (C) 2004-2008 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/poison.h>
15#include <linux/sched.h>
16#include <linux/slab.h>
17#include <linux/security.h>
18#include <linux/workqueue.h>
19#include <linux/random.h>
20#include <linux/err.h>
21#include <linux/user_namespace.h>
22#include "internal.h"
23
24static struct kmem_cache *key_jar;
25struct rb_root key_serial_tree; /* tree of keys indexed by serial */
26DEFINE_SPINLOCK(key_serial_lock);
27
28struct rb_root key_user_tree; /* tree of quota records indexed by UID */
29DEFINE_SPINLOCK(key_user_lock);
30
31unsigned int key_quota_root_maxkeys = 200; /* root's key count quota */
32unsigned int key_quota_root_maxbytes = 20000; /* root's key space quota */
33unsigned int key_quota_maxkeys = 200; /* general key count quota */
34unsigned int key_quota_maxbytes = 20000; /* general key space quota */
35
36static LIST_HEAD(key_types_list);
37static DECLARE_RWSEM(key_types_sem);
38
39static void key_cleanup(struct work_struct *work);
40static DECLARE_WORK(key_cleanup_task, key_cleanup);
41
42/* We serialise key instantiation and link */
43DEFINE_MUTEX(key_construction_mutex);
44
45/* Any key who's type gets unegistered will be re-typed to this */
46static struct key_type key_type_dead = {
47    .name = "dead",
48};
49
50#ifdef KEY_DEBUGGING
51void __key_check(const struct key *key)
52{
53    printk("__key_check: key %p {%08x} should be {%08x}\n",
54           key, key->magic, KEY_DEBUG_MAGIC);
55    BUG();
56}
57#endif
58
59/*
60 * Get the key quota record for a user, allocating a new record if one doesn't
61 * already exist.
62 */
63struct key_user *key_user_lookup(uid_t uid, struct user_namespace *user_ns)
64{
65    struct key_user *candidate = NULL, *user;
66    struct rb_node *parent = NULL;
67    struct rb_node **p;
68
69try_again:
70    p = &key_user_tree.rb_node;
71    spin_lock(&key_user_lock);
72
73    /* search the tree for a user record with a matching UID */
74    while (*p) {
75        parent = *p;
76        user = rb_entry(parent, struct key_user, node);
77
78        if (uid < user->uid)
79            p = &(*p)->rb_left;
80        else if (uid > user->uid)
81            p = &(*p)->rb_right;
82        else if (user_ns < user->user_ns)
83            p = &(*p)->rb_left;
84        else if (user_ns > user->user_ns)
85            p = &(*p)->rb_right;
86        else
87            goto found;
88    }
89
90    /* if we get here, we failed to find a match in the tree */
91    if (!candidate) {
92        /* allocate a candidate user record if we don't already have
93         * one */
94        spin_unlock(&key_user_lock);
95
96        user = NULL;
97        candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
98        if (unlikely(!candidate))
99            goto out;
100
101        /* the allocation may have scheduled, so we need to repeat the
102         * search lest someone else added the record whilst we were
103         * asleep */
104        goto try_again;
105    }
106
107    /* if we get here, then the user record still hadn't appeared on the
108     * second pass - so we use the candidate record */
109    atomic_set(&candidate->usage, 1);
110    atomic_set(&candidate->nkeys, 0);
111    atomic_set(&candidate->nikeys, 0);
112    candidate->uid = uid;
113    candidate->user_ns = get_user_ns(user_ns);
114    candidate->qnkeys = 0;
115    candidate->qnbytes = 0;
116    spin_lock_init(&candidate->lock);
117    mutex_init(&candidate->cons_lock);
118
119    rb_link_node(&candidate->node, parent, p);
120    rb_insert_color(&candidate->node, &key_user_tree);
121    spin_unlock(&key_user_lock);
122    user = candidate;
123    goto out;
124
125    /* okay - we found a user record for this UID */
126found:
127    atomic_inc(&user->usage);
128    spin_unlock(&key_user_lock);
129    kfree(candidate);
130out:
131    return user;
132}
133
134/*
135 * Dispose of a user structure
136 */
137void key_user_put(struct key_user *user)
138{
139    if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
140        rb_erase(&user->node, &key_user_tree);
141        spin_unlock(&key_user_lock);
142        put_user_ns(user->user_ns);
143
144        kfree(user);
145    }
146}
147
148/*
149 * Allocate a serial number for a key. These are assigned randomly to avoid
150 * security issues through covert channel problems.
151 */
152static inline void key_alloc_serial(struct key *key)
153{
154    struct rb_node *parent, **p;
155    struct key *xkey;
156
157    /* propose a random serial number and look for a hole for it in the
158     * serial number tree */
159    do {
160        get_random_bytes(&key->serial, sizeof(key->serial));
161
162        key->serial >>= 1; /* negative numbers are not permitted */
163    } while (key->serial < 3);
164
165    spin_lock(&key_serial_lock);
166
167attempt_insertion:
168    parent = NULL;
169    p = &key_serial_tree.rb_node;
170
171    while (*p) {
172        parent = *p;
173        xkey = rb_entry(parent, struct key, serial_node);
174
175        if (key->serial < xkey->serial)
176            p = &(*p)->rb_left;
177        else if (key->serial > xkey->serial)
178            p = &(*p)->rb_right;
179        else
180            goto serial_exists;
181    }
182
183    /* we've found a suitable hole - arrange for this key to occupy it */
184    rb_link_node(&key->serial_node, parent, p);
185    rb_insert_color(&key->serial_node, &key_serial_tree);
186
187    spin_unlock(&key_serial_lock);
188    return;
189
190    /* we found a key with the proposed serial number - walk the tree from
191     * that point looking for the next unused serial number */
192serial_exists:
193    for (;;) {
194        key->serial++;
195        if (key->serial < 3) {
196            key->serial = 3;
197            goto attempt_insertion;
198        }
199
200        parent = rb_next(parent);
201        if (!parent)
202            goto attempt_insertion;
203
204        xkey = rb_entry(parent, struct key, serial_node);
205        if (key->serial < xkey->serial)
206            goto attempt_insertion;
207    }
208}
209
210/**
211 * key_alloc - Allocate a key of the specified type.
212 * @type: The type of key to allocate.
213 * @desc: The key description to allow the key to be searched out.
214 * @uid: The owner of the new key.
215 * @gid: The group ID for the new key's group permissions.
216 * @cred: The credentials specifying UID namespace.
217 * @perm: The permissions mask of the new key.
218 * @flags: Flags specifying quota properties.
219 *
220 * Allocate a key of the specified type with the attributes given. The key is
221 * returned in an uninstantiated state and the caller needs to instantiate the
222 * key before returning.
223 *
224 * The user's key count quota is updated to reflect the creation of the key and
225 * the user's key data quota has the default for the key type reserved. The
226 * instantiation function should amend this as necessary. If insufficient
227 * quota is available, -EDQUOT will be returned.
228 *
229 * The LSM security modules can prevent a key being created, in which case
230 * -EACCES will be returned.
231 *
232 * Returns a pointer to the new key if successful and an error code otherwise.
233 *
234 * Note that the caller needs to ensure the key type isn't uninstantiated.
235 * Internally this can be done by locking key_types_sem. Externally, this can
236 * be done by either never unregistering the key type, or making sure
237 * key_alloc() calls don't race with module unloading.
238 */
239struct key *key_alloc(struct key_type *type, const char *desc,
240              uid_t uid, gid_t gid, const struct cred *cred,
241              key_perm_t perm, unsigned long flags)
242{
243    struct key_user *user = NULL;
244    struct key *key;
245    size_t desclen, quotalen;
246    int ret;
247
248    key = ERR_PTR(-EINVAL);
249    if (!desc || !*desc)
250        goto error;
251
252    if (type->vet_description) {
253        ret = type->vet_description(desc);
254        if (ret < 0) {
255            key = ERR_PTR(ret);
256            goto error;
257        }
258    }
259
260    desclen = strlen(desc) + 1;
261    quotalen = desclen + type->def_datalen;
262
263    /* get hold of the key tracking for this user */
264    user = key_user_lookup(uid, cred->user->user_ns);
265    if (!user)
266        goto no_memory_1;
267
268    /* check that the user's quota permits allocation of another key and
269     * its description */
270    if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
271        unsigned maxkeys = (uid == 0) ?
272            key_quota_root_maxkeys : key_quota_maxkeys;
273        unsigned maxbytes = (uid == 0) ?
274            key_quota_root_maxbytes : key_quota_maxbytes;
275
276        spin_lock(&user->lock);
277        if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
278            if (user->qnkeys + 1 >= maxkeys ||
279                user->qnbytes + quotalen >= maxbytes ||
280                user->qnbytes + quotalen < user->qnbytes)
281                goto no_quota;
282        }
283
284        user->qnkeys++;
285        user->qnbytes += quotalen;
286        spin_unlock(&user->lock);
287    }
288
289    /* allocate and initialise the key and its description */
290    key = kmem_cache_alloc(key_jar, GFP_KERNEL);
291    if (!key)
292        goto no_memory_2;
293
294    if (desc) {
295        key->description = kmemdup(desc, desclen, GFP_KERNEL);
296        if (!key->description)
297            goto no_memory_3;
298    }
299
300    atomic_set(&key->usage, 1);
301    init_rwsem(&key->sem);
302    key->type = type;
303    key->user = user;
304    key->quotalen = quotalen;
305    key->datalen = type->def_datalen;
306    key->uid = uid;
307    key->gid = gid;
308    key->perm = perm;
309    key->flags = 0;
310    key->expiry = 0;
311    key->payload.data = NULL;
312    key->security = NULL;
313
314    if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
315        key->flags |= 1 << KEY_FLAG_IN_QUOTA;
316
317    memset(&key->type_data, 0, sizeof(key->type_data));
318
319#ifdef KEY_DEBUGGING
320    key->magic = KEY_DEBUG_MAGIC;
321#endif
322
323    /* let the security module know about the key */
324    ret = security_key_alloc(key, cred, flags);
325    if (ret < 0)
326        goto security_error;
327
328    /* publish the key by giving it a serial number */
329    atomic_inc(&user->nkeys);
330    key_alloc_serial(key);
331
332error:
333    return key;
334
335security_error:
336    kfree(key->description);
337    kmem_cache_free(key_jar, key);
338    if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
339        spin_lock(&user->lock);
340        user->qnkeys--;
341        user->qnbytes -= quotalen;
342        spin_unlock(&user->lock);
343    }
344    key_user_put(user);
345    key = ERR_PTR(ret);
346    goto error;
347
348no_memory_3:
349    kmem_cache_free(key_jar, key);
350no_memory_2:
351    if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
352        spin_lock(&user->lock);
353        user->qnkeys--;
354        user->qnbytes -= quotalen;
355        spin_unlock(&user->lock);
356    }
357    key_user_put(user);
358no_memory_1:
359    key = ERR_PTR(-ENOMEM);
360    goto error;
361
362no_quota:
363    spin_unlock(&user->lock);
364    key_user_put(user);
365    key = ERR_PTR(-EDQUOT);
366    goto error;
367}
368EXPORT_SYMBOL(key_alloc);
369
370/**
371 * key_payload_reserve - Adjust data quota reservation for the key's payload
372 * @key: The key to make the reservation for.
373 * @datalen: The amount of data payload the caller now wants.
374 *
375 * Adjust the amount of the owning user's key data quota that a key reserves.
376 * If the amount is increased, then -EDQUOT may be returned if there isn't
377 * enough free quota available.
378 *
379 * If successful, 0 is returned.
380 */
381int key_payload_reserve(struct key *key, size_t datalen)
382{
383    int delta = (int)datalen - key->datalen;
384    int ret = 0;
385
386    key_check(key);
387
388    /* contemplate the quota adjustment */
389    if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
390        unsigned maxbytes = (key->user->uid == 0) ?
391            key_quota_root_maxbytes : key_quota_maxbytes;
392
393        spin_lock(&key->user->lock);
394
395        if (delta > 0 &&
396            (key->user->qnbytes + delta >= maxbytes ||
397             key->user->qnbytes + delta < key->user->qnbytes)) {
398            ret = -EDQUOT;
399        }
400        else {
401            key->user->qnbytes += delta;
402            key->quotalen += delta;
403        }
404        spin_unlock(&key->user->lock);
405    }
406
407    /* change the recorded data length if that didn't generate an error */
408    if (ret == 0)
409        key->datalen = datalen;
410
411    return ret;
412}
413EXPORT_SYMBOL(key_payload_reserve);
414
415/*
416 * Instantiate a key and link it into the target keyring atomically. Must be
417 * called with the target keyring's semaphore writelocked. The target key's
418 * semaphore need not be locked as instantiation is serialised by
419 * key_construction_mutex.
420 */
421static int __key_instantiate_and_link(struct key *key,
422                      const void *data,
423                      size_t datalen,
424                      struct key *keyring,
425                      struct key *authkey,
426                      unsigned long *_prealloc)
427{
428    int ret, awaken;
429
430    key_check(key);
431    key_check(keyring);
432
433    awaken = 0;
434    ret = -EBUSY;
435
436    mutex_lock(&key_construction_mutex);
437
438    /* can't instantiate twice */
439    if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
440        /* instantiate the key */
441        ret = key->type->instantiate(key, data, datalen);
442
443        if (ret == 0) {
444            /* mark the key as being instantiated */
445            atomic_inc(&key->user->nikeys);
446            set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
447
448            if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
449                awaken = 1;
450
451            /* and link it into the destination keyring */
452            if (keyring)
453                __key_link(keyring, key, _prealloc);
454
455            /* disable the authorisation key */
456            if (authkey)
457                key_revoke(authkey);
458        }
459    }
460
461    mutex_unlock(&key_construction_mutex);
462
463    /* wake up anyone waiting for a key to be constructed */
464    if (awaken)
465        wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
466
467    return ret;
468}
469
470/**
471 * key_instantiate_and_link - Instantiate a key and link it into the keyring.
472 * @key: The key to instantiate.
473 * @data: The data to use to instantiate the keyring.
474 * @datalen: The length of @data.
475 * @keyring: Keyring to create a link in on success (or NULL).
476 * @authkey: The authorisation token permitting instantiation.
477 *
478 * Instantiate a key that's in the uninstantiated state using the provided data
479 * and, if successful, link it in to the destination keyring if one is
480 * supplied.
481 *
482 * If successful, 0 is returned, the authorisation token is revoked and anyone
483 * waiting for the key is woken up. If the key was already instantiated,
484 * -EBUSY will be returned.
485 */
486int key_instantiate_and_link(struct key *key,
487                 const void *data,
488                 size_t datalen,
489                 struct key *keyring,
490                 struct key *authkey)
491{
492    unsigned long prealloc;
493    int ret;
494
495    if (keyring) {
496        ret = __key_link_begin(keyring, key->type, key->description,
497                       &prealloc);
498        if (ret < 0)
499            return ret;
500    }
501
502    ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey,
503                     &prealloc);
504
505    if (keyring)
506        __key_link_end(keyring, key->type, prealloc);
507
508    return ret;
509}
510
511EXPORT_SYMBOL(key_instantiate_and_link);
512
513/**
514 * key_reject_and_link - Negatively instantiate a key and link it into the keyring.
515 * @key: The key to instantiate.
516 * @timeout: The timeout on the negative key.
517 * @error: The error to return when the key is hit.
518 * @keyring: Keyring to create a link in on success (or NULL).
519 * @authkey: The authorisation token permitting instantiation.
520 *
521 * Negatively instantiate a key that's in the uninstantiated state and, if
522 * successful, set its timeout and stored error and link it in to the
523 * destination keyring if one is supplied. The key and any links to the key
524 * will be automatically garbage collected after the timeout expires.
525 *
526 * Negative keys are used to rate limit repeated request_key() calls by causing
527 * them to return the stored error code (typically ENOKEY) until the negative
528 * key expires.
529 *
530 * If successful, 0 is returned, the authorisation token is revoked and anyone
531 * waiting for the key is woken up. If the key was already instantiated,
532 * -EBUSY will be returned.
533 */
534int key_reject_and_link(struct key *key,
535            unsigned timeout,
536            unsigned error,
537            struct key *keyring,
538            struct key *authkey)
539{
540    unsigned long prealloc;
541    struct timespec now;
542    int ret, awaken, link_ret = 0;
543
544    key_check(key);
545    key_check(keyring);
546
547    awaken = 0;
548    ret = -EBUSY;
549
550    if (keyring)
551        link_ret = __key_link_begin(keyring, key->type,
552                        key->description, &prealloc);
553
554    mutex_lock(&key_construction_mutex);
555
556    /* can't instantiate twice */
557    if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
558        /* mark the key as being negatively instantiated */
559        atomic_inc(&key->user->nikeys);
560        set_bit(KEY_FLAG_NEGATIVE, &key->flags);
561        set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
562        key->type_data.reject_error = -error;
563        now = current_kernel_time();
564        key->expiry = now.tv_sec + timeout;
565        key_schedule_gc(key->expiry + key_gc_delay);
566
567        if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
568            awaken = 1;
569
570        ret = 0;
571
572        /* and link it into the destination keyring */
573        if (keyring && link_ret == 0)
574            __key_link(keyring, key, &prealloc);
575
576        /* disable the authorisation key */
577        if (authkey)
578            key_revoke(authkey);
579    }
580
581    mutex_unlock(&key_construction_mutex);
582
583    if (keyring)
584        __key_link_end(keyring, key->type, prealloc);
585
586    /* wake up anyone waiting for a key to be constructed */
587    if (awaken)
588        wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
589
590    return ret == 0 ? link_ret : ret;
591}
592EXPORT_SYMBOL(key_reject_and_link);
593
594/*
595 * Garbage collect keys in process context so that we don't have to disable
596 * interrupts all over the place.
597 *
598 * key_put() schedules this rather than trying to do the cleanup itself, which
599 * means key_put() doesn't have to sleep.
600 */
601static void key_cleanup(struct work_struct *work)
602{
603    struct rb_node *_n;
604    struct key *key;
605
606go_again:
607    /* look for a dead key in the tree */
608    spin_lock(&key_serial_lock);
609
610    for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
611        key = rb_entry(_n, struct key, serial_node);
612
613        if (atomic_read(&key->usage) == 0)
614            goto found_dead_key;
615    }
616
617    spin_unlock(&key_serial_lock);
618    return;
619
620found_dead_key:
621    /* we found a dead key - once we've removed it from the tree, we can
622     * drop the lock */
623    rb_erase(&key->serial_node, &key_serial_tree);
624    spin_unlock(&key_serial_lock);
625
626    key_check(key);
627
628    security_key_free(key);
629
630    /* deal with the user's key tracking and quota */
631    if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
632        spin_lock(&key->user->lock);
633        key->user->qnkeys--;
634        key->user->qnbytes -= key->quotalen;
635        spin_unlock(&key->user->lock);
636    }
637
638    atomic_dec(&key->user->nkeys);
639    if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
640        atomic_dec(&key->user->nikeys);
641
642    key_user_put(key->user);
643
644    /* now throw away the key memory */
645    if (key->type->destroy)
646        key->type->destroy(key);
647
648    kfree(key->description);
649
650#ifdef KEY_DEBUGGING
651    key->magic = KEY_DEBUG_MAGIC_X;
652#endif
653    kmem_cache_free(key_jar, key);
654
655    /* there may, of course, be more than one key to destroy */
656    goto go_again;
657}
658
659/**
660 * key_put - Discard a reference to a key.
661 * @key: The key to discard a reference from.
662 *
663 * Discard a reference to a key, and when all the references are gone, we
664 * schedule the cleanup task to come and pull it out of the tree in process
665 * context at some later time.
666 */
667void key_put(struct key *key)
668{
669    if (key) {
670        key_check(key);
671
672        if (atomic_dec_and_test(&key->usage))
673            schedule_work(&key_cleanup_task);
674    }
675}
676EXPORT_SYMBOL(key_put);
677
678/*
679 * Find a key by its serial number.
680 */
681struct key *key_lookup(key_serial_t id)
682{
683    struct rb_node *n;
684    struct key *key;
685
686    spin_lock(&key_serial_lock);
687
688    /* search the tree for the specified key */
689    n = key_serial_tree.rb_node;
690    while (n) {
691        key = rb_entry(n, struct key, serial_node);
692
693        if (id < key->serial)
694            n = n->rb_left;
695        else if (id > key->serial)
696            n = n->rb_right;
697        else
698            goto found;
699    }
700
701not_found:
702    key = ERR_PTR(-ENOKEY);
703    goto error;
704
705found:
706    /* pretend it doesn't exist if it is awaiting deletion */
707    if (atomic_read(&key->usage) == 0)
708        goto not_found;
709
710    /* this races with key_put(), but that doesn't matter since key_put()
711     * doesn't actually change the key
712     */
713    atomic_inc(&key->usage);
714
715error:
716    spin_unlock(&key_serial_lock);
717    return key;
718}
719
720/*
721 * Find and lock the specified key type against removal.
722 *
723 * We return with the sem read-locked if successful. If the type wasn't
724 * available -ENOKEY is returned instead.
725 */
726struct key_type *key_type_lookup(const char *type)
727{
728    struct key_type *ktype;
729
730    down_read(&key_types_sem);
731
732    /* look up the key type to see if it's one of the registered kernel
733     * types */
734    list_for_each_entry(ktype, &key_types_list, link) {
735        if (strcmp(ktype->name, type) == 0)
736            goto found_kernel_type;
737    }
738
739    up_read(&key_types_sem);
740    ktype = ERR_PTR(-ENOKEY);
741
742found_kernel_type:
743    return ktype;
744}
745
746/*
747 * Unlock a key type locked by key_type_lookup().
748 */
749void key_type_put(struct key_type *ktype)
750{
751    up_read(&key_types_sem);
752}
753
754/*
755 * Attempt to update an existing key.
756 *
757 * The key is given to us with an incremented refcount that we need to discard
758 * if we get an error.
759 */
760static inline key_ref_t __key_update(key_ref_t key_ref,
761                     const void *payload, size_t plen)
762{
763    struct key *key = key_ref_to_ptr(key_ref);
764    int ret;
765
766    /* need write permission on the key to update it */
767    ret = key_permission(key_ref, KEY_WRITE);
768    if (ret < 0)
769        goto error;
770
771    ret = -EEXIST;
772    if (!key->type->update)
773        goto error;
774
775    down_write(&key->sem);
776
777    ret = key->type->update(key, payload, plen);
778    if (ret == 0)
779        /* updating a negative key instantiates it */
780        clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
781
782    up_write(&key->sem);
783
784    if (ret < 0)
785        goto error;
786out:
787    return key_ref;
788
789error:
790    key_put(key);
791    key_ref = ERR_PTR(ret);
792    goto out;
793}
794
795/**
796 * key_create_or_update - Update or create and instantiate a key.
797 * @keyring_ref: A pointer to the destination keyring with possession flag.
798 * @type: The type of key.
799 * @description: The searchable description for the key.
800 * @payload: The data to use to instantiate or update the key.
801 * @plen: The length of @payload.
802 * @perm: The permissions mask for a new key.
803 * @flags: The quota flags for a new key.
804 *
805 * Search the destination keyring for a key of the same description and if one
806 * is found, update it, otherwise create and instantiate a new one and create a
807 * link to it from that keyring.
808 *
809 * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
810 * concocted.
811 *
812 * Returns a pointer to the new key if successful, -ENODEV if the key type
813 * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
814 * caller isn't permitted to modify the keyring or the LSM did not permit
815 * creation of the key.
816 *
817 * On success, the possession flag from the keyring ref will be tacked on to
818 * the key ref before it is returned.
819 */
820key_ref_t key_create_or_update(key_ref_t keyring_ref,
821                   const char *type,
822                   const char *description,
823                   const void *payload,
824                   size_t plen,
825                   key_perm_t perm,
826                   unsigned long flags)
827{
828    unsigned long prealloc;
829    const struct cred *cred = current_cred();
830    struct key_type *ktype;
831    struct key *keyring, *key = NULL;
832    key_ref_t key_ref;
833    int ret;
834
835    /* look up the key type to see if it's one of the registered kernel
836     * types */
837    ktype = key_type_lookup(type);
838    if (IS_ERR(ktype)) {
839        key_ref = ERR_PTR(-ENODEV);
840        goto error;
841    }
842
843    key_ref = ERR_PTR(-EINVAL);
844    if (!ktype->match || !ktype->instantiate)
845        goto error_2;
846
847    keyring = key_ref_to_ptr(keyring_ref);
848
849    key_check(keyring);
850
851    key_ref = ERR_PTR(-ENOTDIR);
852    if (keyring->type != &key_type_keyring)
853        goto error_2;
854
855    ret = __key_link_begin(keyring, ktype, description, &prealloc);
856    if (ret < 0)
857        goto error_2;
858
859    /* if we're going to allocate a new key, we're going to have
860     * to modify the keyring */
861    ret = key_permission(keyring_ref, KEY_WRITE);
862    if (ret < 0) {
863        key_ref = ERR_PTR(ret);
864        goto error_3;
865    }
866
867    /* if it's possible to update this type of key, search for an existing
868     * key of the same type and description in the destination keyring and
869     * update that instead if possible
870     */
871    if (ktype->update) {
872        key_ref = __keyring_search_one(keyring_ref, ktype, description,
873                           0);
874        if (!IS_ERR(key_ref))
875            goto found_matching_key;
876    }
877
878    /* if the client doesn't provide, decide on the permissions we want */
879    if (perm == KEY_PERM_UNDEF) {
880        perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
881        perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
882
883        if (ktype->read)
884            perm |= KEY_POS_READ | KEY_USR_READ;
885
886        if (ktype == &key_type_keyring || ktype->update)
887            perm |= KEY_USR_WRITE;
888    }
889
890    /* allocate a new key */
891    key = key_alloc(ktype, description, cred->fsuid, cred->fsgid, cred,
892            perm, flags);
893    if (IS_ERR(key)) {
894        key_ref = ERR_CAST(key);
895        goto error_3;
896    }
897
898    /* instantiate it and link it into the target keyring */
899    ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL,
900                     &prealloc);
901    if (ret < 0) {
902        key_put(key);
903        key_ref = ERR_PTR(ret);
904        goto error_3;
905    }
906
907    key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
908
909 error_3:
910    __key_link_end(keyring, ktype, prealloc);
911 error_2:
912    key_type_put(ktype);
913 error:
914    return key_ref;
915
916 found_matching_key:
917    /* we found a matching key, so we're going to try to update it
918     * - we can drop the locks first as we have the key pinned
919     */
920    __key_link_end(keyring, ktype, prealloc);
921    key_type_put(ktype);
922
923    key_ref = __key_update(key_ref, payload, plen);
924    goto error;
925}
926EXPORT_SYMBOL(key_create_or_update);
927
928/**
929 * key_update - Update a key's contents.
930 * @key_ref: The pointer (plus possession flag) to the key.
931 * @payload: The data to be used to update the key.
932 * @plen: The length of @payload.
933 *
934 * Attempt to update the contents of a key with the given payload data. The
935 * caller must be granted Write permission on the key. Negative keys can be
936 * instantiated by this method.
937 *
938 * Returns 0 on success, -EACCES if not permitted and -EOPNOTSUPP if the key
939 * type does not support updating. The key type may return other errors.
940 */
941int key_update(key_ref_t key_ref, const void *payload, size_t plen)
942{
943    struct key *key = key_ref_to_ptr(key_ref);
944    int ret;
945
946    key_check(key);
947
948    /* the key must be writable */
949    ret = key_permission(key_ref, KEY_WRITE);
950    if (ret < 0)
951        goto error;
952
953    /* attempt to update it if supported */
954    ret = -EOPNOTSUPP;
955    if (key->type->update) {
956        down_write(&key->sem);
957
958        ret = key->type->update(key, payload, plen);
959        if (ret == 0)
960            /* updating a negative key instantiates it */
961            clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
962
963        up_write(&key->sem);
964    }
965
966 error:
967    return ret;
968}
969EXPORT_SYMBOL(key_update);
970
971/**
972 * key_revoke - Revoke a key.
973 * @key: The key to be revoked.
974 *
975 * Mark a key as being revoked and ask the type to free up its resources. The
976 * revocation timeout is set and the key and all its links will be
977 * automatically garbage collected after key_gc_delay amount of time if they
978 * are not manually dealt with first.
979 */
980void key_revoke(struct key *key)
981{
982    struct timespec now;
983    time_t time;
984
985    key_check(key);
986
987    /* make sure no one's trying to change or use the key when we mark it
988     * - we tell lockdep that we might nest because we might be revoking an
989     * authorisation key whilst holding the sem on a key we've just
990     * instantiated
991     */
992    down_write_nested(&key->sem, 1);
993    if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
994        key->type->revoke)
995        key->type->revoke(key);
996
997    /* set the death time to no more than the expiry time */
998    now = current_kernel_time();
999    time = now.tv_sec;
1000    if (key->revoked_at == 0 || key->revoked_at > time) {
1001        key->revoked_at = time;
1002        key_schedule_gc(key->revoked_at + key_gc_delay);
1003    }
1004
1005    up_write(&key->sem);
1006}
1007EXPORT_SYMBOL(key_revoke);
1008
1009/**
1010 * register_key_type - Register a type of key.
1011 * @ktype: The new key type.
1012 *
1013 * Register a new key type.
1014 *
1015 * Returns 0 on success or -EEXIST if a type of this name already exists.
1016 */
1017int register_key_type(struct key_type *ktype)
1018{
1019    struct key_type *p;
1020    int ret;
1021
1022    ret = -EEXIST;
1023    down_write(&key_types_sem);
1024
1025    /* disallow key types with the same name */
1026    list_for_each_entry(p, &key_types_list, link) {
1027        if (strcmp(p->name, ktype->name) == 0)
1028            goto out;
1029    }
1030
1031    /* store the type */
1032    list_add(&ktype->link, &key_types_list);
1033    ret = 0;
1034
1035out:
1036    up_write(&key_types_sem);
1037    return ret;
1038}
1039EXPORT_SYMBOL(register_key_type);
1040
1041/**
1042 * unregister_key_type - Unregister a type of key.
1043 * @ktype: The key type.
1044 *
1045 * Unregister a key type and mark all the extant keys of this type as dead.
1046 * Those keys of this type are then destroyed to get rid of their payloads and
1047 * they and their links will be garbage collected as soon as possible.
1048 */
1049void unregister_key_type(struct key_type *ktype)
1050{
1051    struct rb_node *_n;
1052    struct key *key;
1053
1054    down_write(&key_types_sem);
1055
1056    /* withdraw the key type */
1057    list_del_init(&ktype->link);
1058
1059    /* mark all the keys of this type dead */
1060    spin_lock(&key_serial_lock);
1061
1062    for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
1063        key = rb_entry(_n, struct key, serial_node);
1064
1065        if (key->type == ktype) {
1066            key->type = &key_type_dead;
1067            set_bit(KEY_FLAG_DEAD, &key->flags);
1068        }
1069    }
1070
1071    spin_unlock(&key_serial_lock);
1072
1073    /* make sure everyone revalidates their keys */
1074    synchronize_rcu();
1075
1076    /* we should now be able to destroy the payloads of all the keys of
1077     * this type with impunity */
1078    spin_lock(&key_serial_lock);
1079
1080    for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
1081        key = rb_entry(_n, struct key, serial_node);
1082
1083        if (key->type == ktype) {
1084            if (ktype->destroy)
1085                ktype->destroy(key);
1086            memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
1087        }
1088    }
1089
1090    spin_unlock(&key_serial_lock);
1091    up_write(&key_types_sem);
1092
1093    key_schedule_gc(0);
1094}
1095EXPORT_SYMBOL(unregister_key_type);
1096
1097/*
1098 * Initialise the key management state.
1099 */
1100void __init key_init(void)
1101{
1102    /* allocate a slab in which we can store keys */
1103    key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1104            0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1105
1106    /* add the special key types */
1107    list_add_tail(&key_type_keyring.link, &key_types_list);
1108    list_add_tail(&key_type_dead.link, &key_types_list);
1109    list_add_tail(&key_type_user.link, &key_types_list);
1110
1111    /* record the root user tracking */
1112    rb_link_node(&root_key_user.node,
1113             NULL,
1114             &key_user_tree.rb_node);
1115
1116    rb_insert_color(&root_key_user.node,
1117            &key_user_tree);
1118}
1119

Archive Download this file



interactive