Root/security/keys/request_key.c

Source at commit be977234bfb4a6dca8a39e7c52165e4cd536ad71 created 9 years 5 months ago.
By Lars-Peter Clausen, jz4740: Fix compile error
1/* Request a key from userspace
2 *
3 * Copyright (C) 2004-2007 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 * See Documentation/keys-request-key.txt
12 */
13
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/kmod.h>
17#include <linux/err.h>
18#include <linux/keyctl.h>
19#include <linux/slab.h>
20#include "internal.h"
21
22#define key_negative_timeout 60 /* default timeout on a negative key's existence */
23
24/*
25 * wait_on_bit() sleep function for uninterruptible waiting
26 */
27static int key_wait_bit(void *flags)
28{
29    schedule();
30    return 0;
31}
32
33/*
34 * wait_on_bit() sleep function for interruptible waiting
35 */
36static int key_wait_bit_intr(void *flags)
37{
38    schedule();
39    return signal_pending(current) ? -ERESTARTSYS : 0;
40}
41
42/**
43 * complete_request_key - Complete the construction of a key.
44 * @cons: The key construction record.
45 * @error: The success or failute of the construction.
46 *
47 * Complete the attempt to construct a key. The key will be negated
48 * if an error is indicated. The authorisation key will be revoked
49 * unconditionally.
50 */
51void complete_request_key(struct key_construction *cons, int error)
52{
53    kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
54
55    if (error < 0)
56        key_negate_and_link(cons->key, key_negative_timeout, NULL,
57                    cons->authkey);
58    else
59        key_revoke(cons->authkey);
60
61    key_put(cons->key);
62    key_put(cons->authkey);
63    kfree(cons);
64}
65EXPORT_SYMBOL(complete_request_key);
66
67/*
68 * Initialise a usermode helper that is going to have a specific session
69 * keyring.
70 *
71 * This is called in context of freshly forked kthread before kernel_execve(),
72 * so we can simply install the desired session_keyring at this point.
73 */
74static int umh_keys_init(struct subprocess_info *info)
75{
76    struct cred *cred = (struct cred*)current_cred();
77    struct key *keyring = info->data;
78
79    return install_session_keyring_to_cred(cred, keyring);
80}
81
82/*
83 * Clean up a usermode helper with session keyring.
84 */
85static void umh_keys_cleanup(struct subprocess_info *info)
86{
87    struct key *keyring = info->data;
88    key_put(keyring);
89}
90
91/*
92 * Call a usermode helper with a specific session keyring.
93 */
94static int call_usermodehelper_keys(char *path, char **argv, char **envp,
95             struct key *session_keyring, enum umh_wait wait)
96{
97    gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
98    struct subprocess_info *info =
99        call_usermodehelper_setup(path, argv, envp, gfp_mask);
100
101    if (!info)
102        return -ENOMEM;
103
104    call_usermodehelper_setfns(info, umh_keys_init, umh_keys_cleanup,
105                    key_get(session_keyring));
106    return call_usermodehelper_exec(info, wait);
107}
108
109/*
110 * Request userspace finish the construction of a key
111 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
112 */
113static int call_sbin_request_key(struct key_construction *cons,
114                 const char *op,
115                 void *aux)
116{
117    const struct cred *cred = current_cred();
118    key_serial_t prkey, sskey;
119    struct key *key = cons->key, *authkey = cons->authkey, *keyring,
120        *session;
121    char *argv[9], *envp[3], uid_str[12], gid_str[12];
122    char key_str[12], keyring_str[3][12];
123    char desc[20];
124    int ret, i;
125
126    kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
127
128    ret = install_user_keyrings();
129    if (ret < 0)
130        goto error_alloc;
131
132    /* allocate a new session keyring */
133    sprintf(desc, "_req.%u", key->serial);
134
135    cred = get_current_cred();
136    keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
137                KEY_ALLOC_QUOTA_OVERRUN, NULL);
138    put_cred(cred);
139    if (IS_ERR(keyring)) {
140        ret = PTR_ERR(keyring);
141        goto error_alloc;
142    }
143
144    /* attach the auth key to the session keyring */
145    ret = key_link(keyring, authkey);
146    if (ret < 0)
147        goto error_link;
148
149    /* record the UID and GID */
150    sprintf(uid_str, "%d", cred->fsuid);
151    sprintf(gid_str, "%d", cred->fsgid);
152
153    /* we say which key is under construction */
154    sprintf(key_str, "%d", key->serial);
155
156    /* we specify the process's default keyrings */
157    sprintf(keyring_str[0], "%d",
158        cred->thread_keyring ? cred->thread_keyring->serial : 0);
159
160    prkey = 0;
161    if (cred->tgcred->process_keyring)
162        prkey = cred->tgcred->process_keyring->serial;
163    sprintf(keyring_str[1], "%d", prkey);
164
165    rcu_read_lock();
166    session = rcu_dereference(cred->tgcred->session_keyring);
167    if (!session)
168        session = cred->user->session_keyring;
169    sskey = session->serial;
170    rcu_read_unlock();
171
172    sprintf(keyring_str[2], "%d", sskey);
173
174    /* set up a minimal environment */
175    i = 0;
176    envp[i++] = "HOME=/";
177    envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
178    envp[i] = NULL;
179
180    /* set up the argument list */
181    i = 0;
182    argv[i++] = "/sbin/request-key";
183    argv[i++] = (char *) op;
184    argv[i++] = key_str;
185    argv[i++] = uid_str;
186    argv[i++] = gid_str;
187    argv[i++] = keyring_str[0];
188    argv[i++] = keyring_str[1];
189    argv[i++] = keyring_str[2];
190    argv[i] = NULL;
191
192    /* do it */
193    ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
194                       UMH_WAIT_PROC);
195    kdebug("usermode -> 0x%x", ret);
196    if (ret >= 0) {
197        /* ret is the exit/wait code */
198        if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
199            key_validate(key) < 0)
200            ret = -ENOKEY;
201        else
202            /* ignore any errors from userspace if the key was
203             * instantiated */
204            ret = 0;
205    }
206
207error_link:
208    key_put(keyring);
209
210error_alloc:
211    complete_request_key(cons, ret);
212    kleave(" = %d", ret);
213    return ret;
214}
215
216/*
217 * Call out to userspace for key construction.
218 *
219 * Program failure is ignored in favour of key status.
220 */
221static int construct_key(struct key *key, const void *callout_info,
222             size_t callout_len, void *aux,
223             struct key *dest_keyring)
224{
225    struct key_construction *cons;
226    request_key_actor_t actor;
227    struct key *authkey;
228    int ret;
229
230    kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
231
232    cons = kmalloc(sizeof(*cons), GFP_KERNEL);
233    if (!cons)
234        return -ENOMEM;
235
236    /* allocate an authorisation key */
237    authkey = request_key_auth_new(key, callout_info, callout_len,
238                       dest_keyring);
239    if (IS_ERR(authkey)) {
240        kfree(cons);
241        ret = PTR_ERR(authkey);
242        authkey = NULL;
243    } else {
244        cons->authkey = key_get(authkey);
245        cons->key = key_get(key);
246
247        /* make the call */
248        actor = call_sbin_request_key;
249        if (key->type->request_key)
250            actor = key->type->request_key;
251
252        ret = actor(cons, "create", aux);
253
254        /* check that the actor called complete_request_key() prior to
255         * returning an error */
256        WARN_ON(ret < 0 &&
257            !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
258        key_put(authkey);
259    }
260
261    kleave(" = %d", ret);
262    return ret;
263}
264
265/*
266 * Get the appropriate destination keyring for the request.
267 *
268 * The keyring selected is returned with an extra reference upon it which the
269 * caller must release.
270 */
271static void construct_get_dest_keyring(struct key **_dest_keyring)
272{
273    struct request_key_auth *rka;
274    const struct cred *cred = current_cred();
275    struct key *dest_keyring = *_dest_keyring, *authkey;
276
277    kenter("%p", dest_keyring);
278
279    /* find the appropriate keyring */
280    if (dest_keyring) {
281        /* the caller supplied one */
282        key_get(dest_keyring);
283    } else {
284        /* use a default keyring; falling through the cases until we
285         * find one that we actually have */
286        switch (cred->jit_keyring) {
287        case KEY_REQKEY_DEFL_DEFAULT:
288        case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
289            if (cred->request_key_auth) {
290                authkey = cred->request_key_auth;
291                down_read(&authkey->sem);
292                rka = authkey->payload.data;
293                if (!test_bit(KEY_FLAG_REVOKED,
294                          &authkey->flags))
295                    dest_keyring =
296                        key_get(rka->dest_keyring);
297                up_read(&authkey->sem);
298                if (dest_keyring)
299                    break;
300            }
301
302        case KEY_REQKEY_DEFL_THREAD_KEYRING:
303            dest_keyring = key_get(cred->thread_keyring);
304            if (dest_keyring)
305                break;
306
307        case KEY_REQKEY_DEFL_PROCESS_KEYRING:
308            dest_keyring = key_get(cred->tgcred->process_keyring);
309            if (dest_keyring)
310                break;
311
312        case KEY_REQKEY_DEFL_SESSION_KEYRING:
313            rcu_read_lock();
314            dest_keyring = key_get(
315                rcu_dereference(cred->tgcred->session_keyring));
316            rcu_read_unlock();
317
318            if (dest_keyring)
319                break;
320
321        case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
322            dest_keyring =
323                key_get(cred->user->session_keyring);
324            break;
325
326        case KEY_REQKEY_DEFL_USER_KEYRING:
327            dest_keyring = key_get(cred->user->uid_keyring);
328            break;
329
330        case KEY_REQKEY_DEFL_GROUP_KEYRING:
331        default:
332            BUG();
333        }
334    }
335
336    *_dest_keyring = dest_keyring;
337    kleave(" [dk %d]", key_serial(dest_keyring));
338    return;
339}
340
341/*
342 * Allocate a new key in under-construction state and attempt to link it in to
343 * the requested keyring.
344 *
345 * May return a key that's already under construction instead if there was a
346 * race between two thread calling request_key().
347 */
348static int construct_alloc_key(struct key_type *type,
349                   const char *description,
350                   struct key *dest_keyring,
351                   unsigned long flags,
352                   struct key_user *user,
353                   struct key **_key)
354{
355    const struct cred *cred = current_cred();
356    unsigned long prealloc;
357    struct key *key;
358    key_ref_t key_ref;
359    int ret;
360
361    kenter("%s,%s,,,", type->name, description);
362
363    *_key = NULL;
364    mutex_lock(&user->cons_lock);
365
366    key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
367            KEY_POS_ALL, flags);
368    if (IS_ERR(key))
369        goto alloc_failed;
370
371    set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
372
373    if (dest_keyring) {
374        ret = __key_link_begin(dest_keyring, type, description,
375                       &prealloc);
376        if (ret < 0)
377            goto link_prealloc_failed;
378    }
379
380    /* attach the key to the destination keyring under lock, but we do need
381     * to do another check just in case someone beat us to it whilst we
382     * waited for locks */
383    mutex_lock(&key_construction_mutex);
384
385    key_ref = search_process_keyrings(type, description, type->match, cred);
386    if (!IS_ERR(key_ref))
387        goto key_already_present;
388
389    if (dest_keyring)
390        __key_link(dest_keyring, key, &prealloc);
391
392    mutex_unlock(&key_construction_mutex);
393    if (dest_keyring)
394        __key_link_end(dest_keyring, type, prealloc);
395    mutex_unlock(&user->cons_lock);
396    *_key = key;
397    kleave(" = 0 [%d]", key_serial(key));
398    return 0;
399
400    /* the key is now present - we tell the caller that we found it by
401     * returning -EINPROGRESS */
402key_already_present:
403    key_put(key);
404    mutex_unlock(&key_construction_mutex);
405    key = key_ref_to_ptr(key_ref);
406    if (dest_keyring) {
407        ret = __key_link_check_live_key(dest_keyring, key);
408        if (ret == 0)
409            __key_link(dest_keyring, key, &prealloc);
410        __key_link_end(dest_keyring, type, prealloc);
411        if (ret < 0)
412            goto link_check_failed;
413    }
414    mutex_unlock(&user->cons_lock);
415    *_key = key;
416    kleave(" = -EINPROGRESS [%d]", key_serial(key));
417    return -EINPROGRESS;
418
419link_check_failed:
420    mutex_unlock(&user->cons_lock);
421    key_put(key);
422    kleave(" = %d [linkcheck]", ret);
423    return ret;
424
425link_prealloc_failed:
426    mutex_unlock(&user->cons_lock);
427    kleave(" = %d [prelink]", ret);
428    return ret;
429
430alloc_failed:
431    mutex_unlock(&user->cons_lock);
432    kleave(" = %ld", PTR_ERR(key));
433    return PTR_ERR(key);
434}
435
436/*
437 * Commence key construction.
438 */
439static struct key *construct_key_and_link(struct key_type *type,
440                      const char *description,
441                      const char *callout_info,
442                      size_t callout_len,
443                      void *aux,
444                      struct key *dest_keyring,
445                      unsigned long flags)
446{
447    struct key_user *user;
448    struct key *key;
449    int ret;
450
451    kenter("");
452
453    user = key_user_lookup(current_fsuid(), current_user_ns());
454    if (!user)
455        return ERR_PTR(-ENOMEM);
456
457    construct_get_dest_keyring(&dest_keyring);
458
459    ret = construct_alloc_key(type, description, dest_keyring, flags, user,
460                  &key);
461    key_user_put(user);
462
463    if (ret == 0) {
464        ret = construct_key(key, callout_info, callout_len, aux,
465                    dest_keyring);
466        if (ret < 0) {
467            kdebug("cons failed");
468            goto construction_failed;
469        }
470    } else if (ret == -EINPROGRESS) {
471        ret = 0;
472    } else {
473        key = ERR_PTR(ret);
474    }
475
476    key_put(dest_keyring);
477    kleave(" = key %d", key_serial(key));
478    return key;
479
480construction_failed:
481    key_negate_and_link(key, key_negative_timeout, NULL, NULL);
482    key_put(key);
483    key_put(dest_keyring);
484    kleave(" = %d", ret);
485    return ERR_PTR(ret);
486}
487
488/**
489 * request_key_and_link - Request a key and cache it in a keyring.
490 * @type: The type of key we want.
491 * @description: The searchable description of the key.
492 * @callout_info: The data to pass to the instantiation upcall (or NULL).
493 * @callout_len: The length of callout_info.
494 * @aux: Auxiliary data for the upcall.
495 * @dest_keyring: Where to cache the key.
496 * @flags: Flags to key_alloc().
497 *
498 * A key matching the specified criteria is searched for in the process's
499 * keyrings and returned with its usage count incremented if found. Otherwise,
500 * if callout_info is not NULL, a key will be allocated and some service
501 * (probably in userspace) will be asked to instantiate it.
502 *
503 * If successfully found or created, the key will be linked to the destination
504 * keyring if one is provided.
505 *
506 * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
507 * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
508 * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
509 * if insufficient key quota was available to create a new key; or -ENOMEM if
510 * insufficient memory was available.
511 *
512 * If the returned key was created, then it may still be under construction,
513 * and wait_for_key_construction() should be used to wait for that to complete.
514 */
515struct key *request_key_and_link(struct key_type *type,
516                 const char *description,
517                 const void *callout_info,
518                 size_t callout_len,
519                 void *aux,
520                 struct key *dest_keyring,
521                 unsigned long flags)
522{
523    const struct cred *cred = current_cred();
524    struct key *key;
525    key_ref_t key_ref;
526    int ret;
527
528    kenter("%s,%s,%p,%zu,%p,%p,%lx",
529           type->name, description, callout_info, callout_len, aux,
530           dest_keyring, flags);
531
532    /* search all the process keyrings for a key */
533    key_ref = search_process_keyrings(type, description, type->match,
534                      cred);
535
536    if (!IS_ERR(key_ref)) {
537        key = key_ref_to_ptr(key_ref);
538        if (dest_keyring) {
539            construct_get_dest_keyring(&dest_keyring);
540            ret = key_link(dest_keyring, key);
541            key_put(dest_keyring);
542            if (ret < 0) {
543                key_put(key);
544                key = ERR_PTR(ret);
545                goto error;
546            }
547        }
548    } else if (PTR_ERR(key_ref) != -EAGAIN) {
549        key = ERR_CAST(key_ref);
550    } else {
551        /* the search failed, but the keyrings were searchable, so we
552         * should consult userspace if we can */
553        key = ERR_PTR(-ENOKEY);
554        if (!callout_info)
555            goto error;
556
557        key = construct_key_and_link(type, description, callout_info,
558                         callout_len, aux, dest_keyring,
559                         flags);
560    }
561
562error:
563    kleave(" = %p", key);
564    return key;
565}
566
567/**
568 * wait_for_key_construction - Wait for construction of a key to complete
569 * @key: The key being waited for.
570 * @intr: Whether to wait interruptibly.
571 *
572 * Wait for a key to finish being constructed.
573 *
574 * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
575 * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
576 * revoked or expired.
577 */
578int wait_for_key_construction(struct key *key, bool intr)
579{
580    int ret;
581
582    ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
583              intr ? key_wait_bit_intr : key_wait_bit,
584              intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
585    if (ret < 0)
586        return ret;
587    if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
588        return key->type_data.reject_error;
589    return key_validate(key);
590}
591EXPORT_SYMBOL(wait_for_key_construction);
592
593/**
594 * request_key - Request a key and wait for construction
595 * @type: Type of key.
596 * @description: The searchable description of the key.
597 * @callout_info: The data to pass to the instantiation upcall (or NULL).
598 *
599 * As for request_key_and_link() except that it does not add the returned key
600 * to a keyring if found, new keys are always allocated in the user's quota,
601 * the callout_info must be a NUL-terminated string and no auxiliary data can
602 * be passed.
603 *
604 * Furthermore, it then works as wait_for_key_construction() to wait for the
605 * completion of keys undergoing construction with a non-interruptible wait.
606 */
607struct key *request_key(struct key_type *type,
608            const char *description,
609            const char *callout_info)
610{
611    struct key *key;
612    size_t callout_len = 0;
613    int ret;
614
615    if (callout_info)
616        callout_len = strlen(callout_info);
617    key = request_key_and_link(type, description, callout_info, callout_len,
618                   NULL, NULL, KEY_ALLOC_IN_QUOTA);
619    if (!IS_ERR(key)) {
620        ret = wait_for_key_construction(key, false);
621        if (ret < 0) {
622            key_put(key);
623            return ERR_PTR(ret);
624        }
625    }
626    return key;
627}
628EXPORT_SYMBOL(request_key);
629
630/**
631 * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
632 * @type: The type of key we want.
633 * @description: The searchable description of the key.
634 * @callout_info: The data to pass to the instantiation upcall (or NULL).
635 * @callout_len: The length of callout_info.
636 * @aux: Auxiliary data for the upcall.
637 *
638 * As for request_key_and_link() except that it does not add the returned key
639 * to a keyring if found and new keys are always allocated in the user's quota.
640 *
641 * Furthermore, it then works as wait_for_key_construction() to wait for the
642 * completion of keys undergoing construction with a non-interruptible wait.
643 */
644struct key *request_key_with_auxdata(struct key_type *type,
645                     const char *description,
646                     const void *callout_info,
647                     size_t callout_len,
648                     void *aux)
649{
650    struct key *key;
651    int ret;
652
653    key = request_key_and_link(type, description, callout_info, callout_len,
654                   aux, NULL, KEY_ALLOC_IN_QUOTA);
655    if (!IS_ERR(key)) {
656        ret = wait_for_key_construction(key, false);
657        if (ret < 0) {
658            key_put(key);
659            return ERR_PTR(ret);
660        }
661    }
662    return key;
663}
664EXPORT_SYMBOL(request_key_with_auxdata);
665
666/*
667 * request_key_async - Request a key (allow async construction)
668 * @type: Type of key.
669 * @description: The searchable description of the key.
670 * @callout_info: The data to pass to the instantiation upcall (or NULL).
671 * @callout_len: The length of callout_info.
672 *
673 * As for request_key_and_link() except that it does not add the returned key
674 * to a keyring if found, new keys are always allocated in the user's quota and
675 * no auxiliary data can be passed.
676 *
677 * The caller should call wait_for_key_construction() to wait for the
678 * completion of the returned key if it is still undergoing construction.
679 */
680struct key *request_key_async(struct key_type *type,
681                  const char *description,
682                  const void *callout_info,
683                  size_t callout_len)
684{
685    return request_key_and_link(type, description, callout_info,
686                    callout_len, NULL, NULL,
687                    KEY_ALLOC_IN_QUOTA);
688}
689EXPORT_SYMBOL(request_key_async);
690
691/*
692 * request a key with auxiliary data for the upcaller (allow async construction)
693 * @type: Type of key.
694 * @description: The searchable description of the key.
695 * @callout_info: The data to pass to the instantiation upcall (or NULL).
696 * @callout_len: The length of callout_info.
697 * @aux: Auxiliary data for the upcall.
698 *
699 * As for request_key_and_link() except that it does not add the returned key
700 * to a keyring if found and new keys are always allocated in the user's quota.
701 *
702 * The caller should call wait_for_key_construction() to wait for the
703 * completion of the returned key if it is still undergoing construction.
704 */
705struct key *request_key_async_with_auxdata(struct key_type *type,
706                       const char *description,
707                       const void *callout_info,
708                       size_t callout_len,
709                       void *aux)
710{
711    return request_key_and_link(type, description, callout_info,
712                    callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
713}
714EXPORT_SYMBOL(request_key_async_with_auxdata);
715

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