diff options
Diffstat (limited to 'security/keys/keyring.c')
| -rw-r--r-- | security/keys/keyring.c | 1226 |
1 files changed, 1226 insertions, 0 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c new file mode 100644 index 00000000..a06ffab3 --- /dev/null +++ b/security/keys/keyring.c @@ -0,0 +1,1226 @@ +/* Keyring handling + * + * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/sched.h> +#include <linux/slab.h> +#include <linux/security.h> +#include <linux/seq_file.h> +#include <linux/err.h> +#include <keys/keyring-type.h> +#include <linux/uaccess.h> +#include "internal.h" + +#define rcu_dereference_locked_keyring(keyring) \ + (rcu_dereference_protected( \ + (keyring)->payload.subscriptions, \ + rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem))) + +#define KEY_LINK_FIXQUOTA 1UL + +/* + * When plumbing the depths of the key tree, this sets a hard limit + * set on how deep we're willing to go. + */ +#define KEYRING_SEARCH_MAX_DEPTH 6 + +/* + * We keep all named keyrings in a hash to speed looking them up. + */ +#define KEYRING_NAME_HASH_SIZE (1 << 5) + +static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE]; +static DEFINE_RWLOCK(keyring_name_lock); + +static inline unsigned keyring_hash(const char *desc) +{ + unsigned bucket = 0; + + for (; *desc; desc++) + bucket += (unsigned char)*desc; + + return bucket & (KEYRING_NAME_HASH_SIZE - 1); +} + +/* + * The keyring key type definition. Keyrings are simply keys of this type and + * can be treated as ordinary keys in addition to having their own special + * operations. + */ +static int keyring_instantiate(struct key *keyring, + const void *data, size_t datalen); +static int keyring_match(const struct key *keyring, const void *criterion); +static void keyring_revoke(struct key *keyring); +static void keyring_destroy(struct key *keyring); +static void keyring_describe(const struct key *keyring, struct seq_file *m); +static long keyring_read(const struct key *keyring, + char __user *buffer, size_t buflen); + +struct key_type key_type_keyring = { + .name = "keyring", + .def_datalen = sizeof(struct keyring_list), + .instantiate = keyring_instantiate, + .match = keyring_match, + .revoke = keyring_revoke, + .destroy = keyring_destroy, + .describe = keyring_describe, + .read = keyring_read, +}; +EXPORT_SYMBOL(key_type_keyring); + +/* + * Semaphore to serialise link/link calls to prevent two link calls in parallel + * introducing a cycle. + */ +static DECLARE_RWSEM(keyring_serialise_link_sem); + +/* + * Publish the name of a keyring so that it can be found by name (if it has + * one). + */ +static void keyring_publish_name(struct key *keyring) +{ + int bucket; + + if (keyring->description) { + bucket = keyring_hash(keyring->description); + + write_lock(&keyring_name_lock); + + if (!keyring_name_hash[bucket].next) + INIT_LIST_HEAD(&keyring_name_hash[bucket]); + + list_add_tail(&keyring->type_data.link, + &keyring_name_hash[bucket]); + + write_unlock(&keyring_name_lock); + } +} + +/* + * Initialise a keyring. + * + * Returns 0 on success, -EINVAL if given any data. + */ +static int keyring_instantiate(struct key *keyring, + const void *data, size_t datalen) +{ + int ret; + + ret = -EINVAL; + if (datalen == 0) { + /* make the keyring available by name if it has one */ + keyring_publish_name(keyring); + ret = 0; + } + + return ret; +} + +/* + * Match keyrings on their name + */ +static int keyring_match(const struct key *keyring, const void *description) +{ + return keyring->description && + strcmp(keyring->description, description) == 0; +} + +/* + * Clean up a keyring when it is destroyed. Unpublish its name if it had one + * and dispose of its data. + */ +static void keyring_destroy(struct key *keyring) +{ + struct keyring_list *klist; + int loop; + + if (keyring->description) { + write_lock(&keyring_name_lock); + + if (keyring->type_data.link.next != NULL && + !list_empty(&keyring->type_data.link)) + list_del(&keyring->type_data.link); + + write_unlock(&keyring_name_lock); + } + + klist = rcu_dereference_check(keyring->payload.subscriptions, + rcu_read_lock_held() || + atomic_read(&keyring->usage) == 0); + if (klist) { + for (loop = klist->nkeys - 1; loop >= 0; loop--) + key_put(klist->keys[loop]); + kfree(klist); + } +} + +/* + * Describe a keyring for /proc. + */ +static void keyring_describe(const struct key *keyring, struct seq_file *m) +{ + struct keyring_list *klist; + + if (keyring->description) + seq_puts(m, keyring->description); + else + seq_puts(m, "[anon]"); + + if (key_is_instantiated(keyring)) { + rcu_read_lock(); + klist = rcu_dereference(keyring->payload.subscriptions); + if (klist) + seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys); + else + seq_puts(m, ": empty"); + rcu_read_unlock(); + } +} + +/* + * Read a list of key IDs from the keyring's contents in binary form + * + * The keyring's semaphore is read-locked by the caller. + */ +static long keyring_read(const struct key *keyring, + char __user *buffer, size_t buflen) +{ + struct keyring_list *klist; + struct key *key; + size_t qty, tmp; + int loop, ret; + + ret = 0; + klist = rcu_dereference_locked_keyring(keyring); + if (klist) { + /* calculate how much data we could return */ + qty = klist->nkeys * sizeof(key_serial_t); + + if (buffer && buflen > 0) { + if (buflen > qty) + buflen = qty; + + /* copy the IDs of the subscribed keys into the + * buffer */ + ret = -EFAULT; + + for (loop = 0; loop < klist->nkeys; loop++) { + key = klist->keys[loop]; + + tmp = sizeof(key_serial_t); + if (tmp > buflen) + tmp = buflen; + + if (copy_to_user(buffer, + &key->serial, + tmp) != 0) + goto error; + + buflen -= tmp; + if (buflen == 0) + break; + buffer += tmp; + } + } + + ret = qty; + } + +error: + return ret; +} + +/* + * Allocate a keyring and link into the destination keyring. + */ +struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid, + const struct cred *cred, unsigned long flags, + struct key *dest) +{ + struct key *keyring; + int ret; + + keyring = key_alloc(&key_type_keyring, description, + uid, gid, cred, + (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL, + flags); + + if (!IS_ERR(keyring)) { + ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL); + if (ret < 0) { + key_put(keyring); + keyring = ERR_PTR(ret); + } + } + + return keyring; +} + +/** + * keyring_search_aux - Search a keyring tree for a key matching some criteria + * @keyring_ref: A pointer to the keyring with possession indicator. + * @cred: The credentials to use for permissions checks. + * @type: The type of key to search for. + * @description: Parameter for @match. + * @match: Function to rule on whether or not a key is the one required. + * @no_state_check: Don't check if a matching key is bad + * + * Search the supplied keyring tree for a key that matches the criteria given. + * The root keyring and any linked keyrings must grant Search permission to the + * caller to be searchable and keys can only be found if they too grant Search + * to the caller. The possession flag on the root keyring pointer controls use + * of the possessor bits in permissions checking of the entire tree. In + * addition, the LSM gets to forbid keyring searches and key matches. + * + * The search is performed as a breadth-then-depth search up to the prescribed + * limit (KEYRING_SEARCH_MAX_DEPTH). + * + * Keys are matched to the type provided and are then filtered by the match + * function, which is given the description to use in any way it sees fit. The + * match function may use any attributes of a key that it wishes to to + * determine the match. Normally the match function from the key type would be + * used. + * + * RCU is used to prevent the keyring key lists from disappearing without the + * need to take lots of locks. + * + * Returns a pointer to the found key and increments the key usage count if + * successful; -EAGAIN if no matching keys were found, or if expired or revoked + * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the + * specified keyring wasn't a keyring. + * + * In the case of a successful return, the possession attribute from + * @keyring_ref is propagated to the returned key reference. + */ +key_ref_t keyring_search_aux(key_ref_t keyring_ref, + const struct cred *cred, + struct key_type *type, + const void *description, + key_match_func_t match, + bool no_state_check) +{ + struct { + struct keyring_list *keylist; + int kix; + } stack[KEYRING_SEARCH_MAX_DEPTH]; + + struct keyring_list *keylist; + struct timespec now; + unsigned long possessed, kflags; + struct key *keyring, *key; + key_ref_t key_ref; + long err; + int sp, kix; + + keyring = key_ref_to_ptr(keyring_ref); + possessed = is_key_possessed(keyring_ref); + key_check(keyring); + + /* top keyring must have search permission to begin the search */ + err = key_task_permission(keyring_ref, cred, KEY_SEARCH); + if (err < 0) { + key_ref = ERR_PTR(err); + goto error; + } + + key_ref = ERR_PTR(-ENOTDIR); + if (keyring->type != &key_type_keyring) + goto error; + + rcu_read_lock(); + + now = current_kernel_time(); + err = -EAGAIN; + sp = 0; + + /* firstly we should check to see if this top-level keyring is what we + * are looking for */ + key_ref = ERR_PTR(-EAGAIN); + kflags = keyring->flags; + if (keyring->type == type && match(keyring, description)) { + key = keyring; + if (no_state_check) + goto found; + + /* check it isn't negative and hasn't expired or been + * revoked */ + if (kflags & (1 << KEY_FLAG_REVOKED)) + goto error_2; + if (key->expiry && now.tv_sec >= key->expiry) + goto error_2; + key_ref = ERR_PTR(key->type_data.reject_error); + if (kflags & (1 << KEY_FLAG_NEGATIVE)) + goto error_2; + goto found; + } + + /* otherwise, the top keyring must not be revoked, expired, or + * negatively instantiated if we are to search it */ + key_ref = ERR_PTR(-EAGAIN); + if (kflags & ((1 << KEY_FLAG_REVOKED) | (1 << KEY_FLAG_NEGATIVE)) || + (keyring->expiry && now.tv_sec >= keyring->expiry)) + goto error_2; + + /* start processing a new keyring */ +descend: + if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) + goto not_this_keyring; + + keylist = rcu_dereference(keyring->payload.subscriptions); + if (!keylist) + goto not_this_keyring; + + /* iterate through the keys in this keyring first */ + for (kix = 0; kix < keylist->nkeys; kix++) { + key = keylist->keys[kix]; + kflags = key->flags; + + /* ignore keys not of this type */ + if (key->type != type) + continue; + + /* skip revoked keys and expired keys */ + if (!no_state_check) { + if (kflags & (1 << KEY_FLAG_REVOKED)) + continue; + + if (key->expiry && now.tv_sec >= key->expiry) + continue; + } + + /* keys that don't match */ + if (!match(key, description)) + continue; + + /* key must have search permissions */ + if (key_task_permission(make_key_ref(key, possessed), + cred, KEY_SEARCH) < 0) + continue; + + if (no_state_check) + goto found; + + /* we set a different error code if we pass a negative key */ + if (kflags & (1 << KEY_FLAG_NEGATIVE)) { + err = key->type_data.reject_error; + continue; + } + + goto found; + } + + /* search through the keyrings nested in this one */ + kix = 0; +ascend: + for (; kix < keylist->nkeys; kix++) { + key = keylist->keys[kix]; + if (key->type != &key_type_keyring) + continue; + + /* recursively search nested keyrings + * - only search keyrings for which we have search permission + */ + if (sp >= KEYRING_SEARCH_MAX_DEPTH) + continue; + + if (key_task_permission(make_key_ref(key, possessed), + cred, KEY_SEARCH) < 0) + continue; + + /* stack the current position */ + stack[sp].keylist = keylist; + stack[sp].kix = kix; + sp++; + + /* begin again with the new keyring */ + keyring = key; + goto descend; + } + + /* the keyring we're looking at was disqualified or didn't contain a + * matching key */ +not_this_keyring: + if (sp > 0) { + /* resume the processing of a keyring higher up in the tree */ + sp--; + keylist = stack[sp].keylist; + kix = stack[sp].kix + 1; + goto ascend; + } + + key_ref = ERR_PTR(err); + goto error_2; + + /* we found a viable match */ +found: + atomic_inc(&key->usage); + key_check(key); + key_ref = make_key_ref(key, possessed); +error_2: + rcu_read_unlock(); +error: + return key_ref; +} + +/** + * keyring_search - Search the supplied keyring tree for a matching key + * @keyring: The root of the keyring tree to be searched. + * @type: The type of keyring we want to find. + * @description: The name of the keyring we want to find. + * + * As keyring_search_aux() above, but using the current task's credentials and + * type's default matching function. + */ +key_ref_t keyring_search(key_ref_t keyring, + struct key_type *type, + const char *description) +{ + if (!type->match) + return ERR_PTR(-ENOKEY); + + return keyring_search_aux(keyring, current->cred, + type, description, type->match, false); +} +EXPORT_SYMBOL(keyring_search); + +/* + * Search the given keyring only (no recursion). + * + * The caller must guarantee that the keyring is a keyring and that the + * permission is granted to search the keyring as no check is made here. + * + * RCU is used to make it unnecessary to lock the keyring key list here. + * + * Returns a pointer to the found key with usage count incremented if + * successful and returns -ENOKEY if not found. Revoked keys and keys not + * providing the requested permission are skipped over. + * + * If successful, the possession indicator is propagated from the keyring ref + * to the returned key reference. + */ +key_ref_t __keyring_search_one(key_ref_t keyring_ref, + const struct key_type *ktype, + const char *description, + key_perm_t perm) +{ + struct keyring_list *klist; + unsigned long possessed; + struct key *keyring, *key; + int loop; + + keyring = key_ref_to_ptr(keyring_ref); + possessed = is_key_possessed(keyring_ref); + + rcu_read_lock(); + + klist = rcu_dereference(keyring->payload.subscriptions); + if (klist) { + for (loop = 0; loop < klist->nkeys; loop++) { + key = klist->keys[loop]; + + if (key->type == ktype && + (!key->type->match || + key->type->match(key, description)) && + key_permission(make_key_ref(key, possessed), + perm) == 0 && + !test_bit(KEY_FLAG_REVOKED, &key->flags) + ) + goto found; + } + } + + rcu_read_unlock(); + return ERR_PTR(-ENOKEY); + +found: + atomic_inc(&key->usage); + rcu_read_unlock(); + return make_key_ref(key, possessed); +} + +/* + * Find a keyring with the specified name. + * + * All named keyrings in the current user namespace are searched, provided they + * grant Search permission directly to the caller (unless this check is + * skipped). Keyrings whose usage points have reached zero or who have been + * revoked are skipped. + * + * Returns a pointer to the keyring with the keyring's refcount having being + * incremented on success. -ENOKEY is returned if a key could not be found. + */ +struct key *find_keyring_by_name(const char *name, bool skip_perm_check) +{ + struct key *keyring; + int bucket; + + if (!name) + return ERR_PTR(-EINVAL); + + bucket = keyring_hash(name); + + read_lock(&keyring_name_lock); + + if (keyring_name_hash[bucket].next) { + /* search this hash bucket for a keyring with a matching name + * that's readable and that hasn't been revoked */ + list_for_each_entry(keyring, + &keyring_name_hash[bucket], + type_data.link + ) { + if (keyring->user->user_ns != current_user_ns()) + continue; + + if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) + continue; + + if (strcmp(keyring->description, name) != 0) + continue; + + if (!skip_perm_check && + key_permission(make_key_ref(keyring, 0), + KEY_SEARCH) < 0) + continue; + + /* we've got a match but we might end up racing with + * key_cleanup() if the keyring is currently 'dead' + * (ie. it has a zero usage count) */ + if (!atomic_inc_not_zero(&keyring->usage)) + continue; + goto out; + } + } + + keyring = ERR_PTR(-ENOKEY); +out: + read_unlock(&keyring_name_lock); + return keyring; +} + +/* + * See if a cycle will will be created by inserting acyclic tree B in acyclic + * tree A at the topmost level (ie: as a direct child of A). + * + * Since we are adding B to A at the top level, checking for cycles should just + * be a matter of seeing if node A is somewhere in tree B. + */ +static int keyring_detect_cycle(struct key *A, struct key *B) +{ + struct { + struct keyring_list *keylist; + int kix; + } stack[KEYRING_SEARCH_MAX_DEPTH]; + + struct keyring_list *keylist; + struct key *subtree, *key; + int sp, kix, ret; + + rcu_read_lock(); + + ret = -EDEADLK; + if (A == B) + goto cycle_detected; + + subtree = B; + sp = 0; + + /* start processing a new keyring */ +descend: + if (test_bit(KEY_FLAG_REVOKED, &subtree->flags)) + goto not_this_keyring; + + keylist = rcu_dereference(subtree->payload.subscriptions); + if (!keylist) + goto not_this_keyring; + kix = 0; + +ascend: + /* iterate through the remaining keys in this keyring */ + for (; kix < keylist->nkeys; kix++) { + key = keylist->keys[kix]; + + if (key == A) + goto cycle_detected; + + /* recursively check nested keyrings */ + if (key->type == &key_type_keyring) { + if (sp >= KEYRING_SEARCH_MAX_DEPTH) + goto too_deep; + + /* stack the current position */ + stack[sp].keylist = keylist; + stack[sp].kix = kix; + sp++; + + /* begin again with the new keyring */ + subtree = key; + goto descend; + } + } + + /* the keyring we're looking at was disqualified or didn't contain a + * matching key */ +not_this_keyring: + if (sp > 0) { + /* resume the checking of a keyring higher up in the tree */ + sp--; + keylist = stack[sp].keylist; + kix = stack[sp].kix + 1; + goto ascend; + } + + ret = 0; /* no cycles detected */ + +error: + rcu_read_unlock(); + return ret; + +too_deep: + ret = -ELOOP; + goto error; + +cycle_detected: + ret = -EDEADLK; + goto error; +} + +/* + * Dispose of a keyring list after the RCU grace period, freeing the unlinked + * key + */ +static void keyring_unlink_rcu_disposal(struct rcu_head *rcu) +{ + struct keyring_list *klist = + container_of(rcu, struct keyring_list, rcu); + + if (klist->delkey != USHRT_MAX) + key_put(klist->keys[klist->delkey]); + kfree(klist); +} + +/* + * Preallocate memory so that a key can be linked into to a keyring. + */ +int __key_link_begin(struct key *keyring, const struct key_type *type, + const char *description, unsigned long *_prealloc) + __acquires(&keyring->sem) +{ + struct keyring_list *klist, *nklist; + unsigned long prealloc; + unsigned max; + size_t size; + int loop, ret; + + kenter("%d,%s,%s,", key_serial(keyring), type->name, description); + + if (keyring->type != &key_type_keyring) + return -ENOTDIR; + + down_write(&keyring->sem); + + ret = -EKEYREVOKED; + if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) + goto error_krsem; + + /* serialise link/link calls to prevent parallel calls causing a cycle + * when linking two keyring in opposite orders */ + if (type == &key_type_keyring) + down_write(&keyring_serialise_link_sem); + + klist = rcu_dereference_locked_keyring(keyring); + + /* see if there's a matching key we can displace */ + if (klist && klist->nkeys > 0) { + for (loop = klist->nkeys - 1; loop >= 0; loop--) { + if (klist->keys[loop]->type == type && + strcmp(klist->keys[loop]->description, + description) == 0 + ) { + /* found a match - we'll replace this one with + * the new key */ + size = sizeof(struct key *) * klist->maxkeys; + size += sizeof(*klist); + BUG_ON(size > PAGE_SIZE); + + ret = -ENOMEM; + nklist = kmemdup(klist, size, GFP_KERNEL); + if (!nklist) + goto error_sem; + + /* note replacement slot */ + klist->delkey = nklist->delkey = loop; + prealloc = (unsigned long)nklist; + goto done; + } + } + } + + /* check that we aren't going to overrun the user's quota */ + ret = key_payload_reserve(keyring, + keyring->datalen + KEYQUOTA_LINK_BYTES); + if (ret < 0) + goto error_sem; + + if (klist && klist->nkeys < klist->maxkeys) { + /* there's sufficient slack space to append directly */ + nklist = NULL; + prealloc = KEY_LINK_FIXQUOTA; + } else { + /* grow the key list */ + max = 4; + if (klist) + max += klist->maxkeys; + + ret = -ENFILE; + if (max > USHRT_MAX - 1) + goto error_quota; + size = sizeof(*klist) + sizeof(struct key *) * max; + if (size > PAGE_SIZE) + goto error_quota; + + ret = -ENOMEM; + nklist = kmalloc(size, GFP_KERNEL); + if (!nklist) + goto error_quota; + + nklist->maxkeys = max; + if (klist) { + memcpy(nklist->keys, klist->keys, + sizeof(struct key *) * klist->nkeys); + nklist->delkey = klist->nkeys; + nklist->nkeys = klist->nkeys + 1; + klist->delkey = USHRT_MAX; + } else { + nklist->nkeys = 1; + nklist->delkey = 0; + } + + /* add the key into the new space */ + nklist->keys[nklist->delkey] = NULL; + } + + prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA; +done: + *_prealloc = prealloc; + kleave(" = 0"); + return 0; + +error_quota: + /* undo the quota changes */ + key_payload_reserve(keyring, + keyring->datalen - KEYQUOTA_LINK_BYTES); +error_sem: + if (type == &key_type_keyring) + up_write(&keyring_serialise_link_sem); +error_krsem: + up_write(&keyring->sem); + kleave(" = %d", ret); + return ret; +} + +/* + * Check already instantiated keys aren't going to be a problem. + * + * The caller must have called __key_link_begin(). Don't need to call this for + * keys that were created since __key_link_begin() was called. + */ +int __key_link_check_live_key(struct key *keyring, struct key *key) +{ + if (key->type == &key_type_keyring) + /* check that we aren't going to create a cycle by linking one + * keyring to another */ + return keyring_detect_cycle(keyring, key); + return 0; +} + +/* + * Link a key into to a keyring. + * + * Must be called with __key_link_begin() having being called. Discards any + * already extant link to matching key if there is one, so that each keyring + * holds at most one link to any given key of a particular type+description + * combination. + */ +void __key_link(struct key *keyring, struct key *key, + unsigned long *_prealloc) +{ + struct keyring_list *klist, *nklist; + + nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA); + *_prealloc = 0; + + kenter("%d,%d,%p", keyring->serial, key->serial, nklist); + + klist = rcu_dereference_protected(keyring->payload.subscriptions, + rwsem_is_locked(&keyring->sem)); + + atomic_inc(&key->usage); + + /* there's a matching key we can displace or an empty slot in a newly + * allocated list we can fill */ + if (nklist) { + kdebug("replace %hu/%hu/%hu", + nklist->delkey, nklist->nkeys, nklist->maxkeys); + + nklist->keys[nklist->delkey] = key; + + rcu_assign_pointer(keyring->payload.subscriptions, nklist); + + /* dispose of the old keyring list and, if there was one, the + * displaced key */ + if (klist) { + kdebug("dispose %hu/%hu/%hu", + klist->delkey, klist->nkeys, klist->maxkeys); + call_rcu(&klist->rcu, keyring_unlink_rcu_disposal); + } + } else { + /* there's sufficient slack space to append directly */ + klist->keys[klist->nkeys] = key; + smp_wmb(); + klist->nkeys++; + } +} + +/* + * Finish linking a key into to a keyring. + * + * Must be called with __key_link_begin() having being called. + */ +void __key_link_end(struct key *keyring, struct key_type *type, + unsigned long prealloc) + __releases(&keyring->sem) +{ + BUG_ON(type == NULL); + BUG_ON(type->name == NULL); + kenter("%d,%s,%lx", keyring->serial, type->name, prealloc); + + if (type == &key_type_keyring) + up_write(&keyring_serialise_link_sem); + + if (prealloc) { + if (prealloc & KEY_LINK_FIXQUOTA) + key_payload_reserve(keyring, + keyring->datalen - + KEYQUOTA_LINK_BYTES); + kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA)); + } + up_write(&keyring->sem); +} + +/** + * key_link - Link a key to a keyring + * @keyring: The keyring to make the link in. + * @key: The key to link to. + * + * Make a link in a keyring to a key, such that the keyring holds a reference + * on that key and the key can potentially be found by searching that keyring. + * + * This function will write-lock the keyring's semaphore and will consume some + * of the user's key data quota to hold the link. + * + * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, + * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is + * full, -EDQUOT if there is insufficient key data quota remaining to add + * another link or -ENOMEM if there's insufficient memory. + * + * It is assumed that the caller has checked that it is permitted for a link to + * be made (the keyring should have Write permission and the key Link + * permission). + */ +int key_link(struct key *keyring, struct key *key) +{ + unsigned long prealloc; + int ret; + + key_check(keyring); + key_check(key); + + ret = __key_link_begin(keyring, key->type, key->description, &prealloc); + if (ret == 0) { + ret = __key_link_check_live_key(keyring, key); + if (ret == 0) + __key_link(keyring, key, &prealloc); + __key_link_end(keyring, key->type, prealloc); + } + + return ret; +} +EXPORT_SYMBOL(key_link); + +/** + * key_unlink - Unlink the first link to a key from a keyring. + * @keyring: The keyring to remove the link from. + * @key: The key the link is to. + * + * Remove a link from a keyring to a key. + * + * This function will write-lock the keyring's semaphore. + * + * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if + * the key isn't linked to by the keyring or -ENOMEM if there's insufficient + * memory. + * + * It is assumed that the caller has checked that it is permitted for a link to + * be removed (the keyring should have Write permission; no permissions are + * required on the key). + */ +int key_unlink(struct key *keyring, struct key *key) +{ + struct keyring_list *klist, *nklist; + int loop, ret; + + key_check(keyring); + key_check(key); + + ret = -ENOTDIR; + if (keyring->type != &key_type_keyring) + goto error; + + down_write(&keyring->sem); + + klist = rcu_dereference_locked_keyring(keyring); + if (klist) { + /* search the keyring for the key */ + for (loop = 0; loop < klist->nkeys; loop++) + if (klist->keys[loop] == key) + goto key_is_present; + } + + up_write(&keyring->sem); + ret = -ENOENT; + goto error; + +key_is_present: + /* we need to copy the key list for RCU purposes */ + nklist = kmalloc(sizeof(*klist) + + sizeof(struct key *) * klist->maxkeys, + GFP_KERNEL); + if (!nklist) + goto nomem; + nklist->maxkeys = klist->maxkeys; + nklist->nkeys = klist->nkeys - 1; + + if (loop > 0) + memcpy(&nklist->keys[0], + &klist->keys[0], + loop * sizeof(struct key *)); + + if (loop < nklist->nkeys) + memcpy(&nklist->keys[loop], + &klist->keys[loop + 1], + (nklist->nkeys - loop) * sizeof(struct key *)); + + /* adjust the user's quota */ + key_payload_reserve(keyring, + keyring->datalen - KEYQUOTA_LINK_BYTES); + + rcu_assign_pointer(keyring->payload.subscriptions, nklist); + + up_write(&keyring->sem); + + /* schedule for later cleanup */ + klist->delkey = loop; + call_rcu(&klist->rcu, keyring_unlink_rcu_disposal); + + ret = 0; + +error: + return ret; +nomem: + ret = -ENOMEM; + up_write(&keyring->sem); + goto error; +} +EXPORT_SYMBOL(key_unlink); + +/* + * Dispose of a keyring list after the RCU grace period, releasing the keys it + * links to. + */ +static void keyring_clear_rcu_disposal(struct rcu_head *rcu) +{ + struct keyring_list *klist; + int loop; + + klist = container_of(rcu, struct keyring_list, rcu); + + for (loop = klist->nkeys - 1; loop >= 0; loop--) + key_put(klist->keys[loop]); + + kfree(klist); +} + +/** + * keyring_clear - Clear a keyring + * @keyring: The keyring to clear. + * + * Clear the contents of the specified keyring. + * + * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring. + */ +int keyring_clear(struct key *keyring) +{ + struct keyring_list *klist; + int ret; + + ret = -ENOTDIR; + if (keyring->type == &key_type_keyring) { + /* detach the pointer block with the locks held */ + down_write(&keyring->sem); + + klist = rcu_dereference_locked_keyring(keyring); + if (klist) { + /* adjust the quota */ + key_payload_reserve(keyring, + sizeof(struct keyring_list)); + + rcu_assign_pointer(keyring->payload.subscriptions, + NULL); + } + + up_write(&keyring->sem); + + /* free the keys after the locks have been dropped */ + if (klist) + call_rcu(&klist->rcu, keyring_clear_rcu_disposal); + + ret = 0; + } + + return ret; +} +EXPORT_SYMBOL(keyring_clear); + +/* + * Dispose of the links from a revoked keyring. + * + * This is called with the key sem write-locked. + */ +static void keyring_revoke(struct key *keyring) +{ + struct keyring_list *klist; + + klist = rcu_dereference_locked_keyring(keyring); + + /* adjust the quota */ + key_payload_reserve(keyring, 0); + + if (klist) { + rcu_assign_pointer(keyring->payload.subscriptions, NULL); + call_rcu(&klist->rcu, keyring_clear_rcu_disposal); + } +} + +/* + * Determine whether a key is dead. + */ +static bool key_is_dead(struct key *key, time_t limit) +{ + return test_bit(KEY_FLAG_DEAD, &key->flags) || + (key->expiry > 0 && key->expiry <= limit); +} + +/* + * Collect garbage from the contents of a keyring, replacing the old list with + * a new one with the pointers all shuffled down. + * + * Dead keys are classed as oned that are flagged as being dead or are revoked, + * expired or negative keys that were revoked or expired before the specified + * limit. + */ +void keyring_gc(struct key *keyring, time_t limit) +{ + struct keyring_list *klist, *new; + struct key *key; + int loop, keep, max; + + kenter("{%x,%s}", key_serial(keyring), keyring->description); + + down_write(&keyring->sem); + + klist = rcu_dereference_locked_keyring(keyring); + if (!klist) + goto no_klist; + + /* work out how many subscriptions we're keeping */ + keep = 0; + for (loop = klist->nkeys - 1; loop >= 0; loop--) + if (!key_is_dead(klist->keys[loop], limit)) + keep++; + + if (keep == klist->nkeys) + goto just_return; + + /* allocate a new keyring payload */ + max = roundup(keep, 4); + new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *), + GFP_KERNEL); + if (!new) + goto nomem; + new->maxkeys = max; + new->nkeys = 0; + new->delkey = 0; + + /* install the live keys + * - must take care as expired keys may be updated back to life + */ + keep = 0; + for (loop = klist->nkeys - 1; loop >= 0; loop--) { + key = klist->keys[loop]; + if (!key_is_dead(key, limit)) { + if (keep >= max) + goto discard_new; + new->keys[keep++] = key_get(key); + } + } + new->nkeys = keep; + + /* adjust the quota */ + key_payload_reserve(keyring, + sizeof(struct keyring_list) + + KEYQUOTA_LINK_BYTES * keep); + + if (keep == 0) { + rcu_assign_pointer(keyring->payload.subscriptions, NULL); + kfree(new); + } else { + rcu_assign_pointer(keyring->payload.subscriptions, new); + } + + up_write(&keyring->sem); + + call_rcu(&klist->rcu, keyring_clear_rcu_disposal); + kleave(" [yes]"); + return; + +discard_new: + new->nkeys = keep; + keyring_clear_rcu_disposal(&new->rcu); + up_write(&keyring->sem); + kleave(" [discard]"); + return; + +just_return: + up_write(&keyring->sem); + kleave(" [no dead]"); + return; + +no_klist: + up_write(&keyring->sem); + kleave(" [no_klist]"); + return; + +nomem: + up_write(&keyring->sem); + kleave(" [oom]"); +} |