![David Howells](/assets/img/avatar_default.png)
Inaugurate copy-on-write credentials management. This uses RCU to manage the credentials pointer in the task_struct with respect to accesses by other tasks. A process may only modify its own credentials, and so does not need locking to access or modify its own credentials. A mutex (cred_replace_mutex) is added to the task_struct to control the effect of PTRACE_ATTACHED on credential calculations, particularly with respect to execve(). With this patch, the contents of an active credentials struct may not be changed directly; rather a new set of credentials must be prepared, modified and committed using something like the following sequence of events: struct cred *new = prepare_creds(); int ret = blah(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); There are some exceptions to this rule: the keyrings pointed to by the active credentials may be instantiated - keyrings violate the COW rule as managing COW keyrings is tricky, given that it is possible for a task to directly alter the keys in a keyring in use by another task. To help enforce this, various pointers to sets of credentials, such as those in the task_struct, are declared const. The purpose of this is compile-time discouragement of altering credentials through those pointers. Once a set of credentials has been made public through one of these pointers, it may not be modified, except under special circumstances: (1) Its reference count may incremented and decremented. (2) The keyrings to which it points may be modified, but not replaced. The only safe way to modify anything else is to create a replacement and commit using the functions described in Documentation/credentials.txt (which will be added by a later patch). This patch and the preceding patches have been tested with the LTP SELinux testsuite. This patch makes several logical sets of alteration: (1) execve(). This now prepares and commits credentials in various places in the security code rather than altering the current creds directly. (2) Temporary credential overrides. do_coredump() and sys_faccessat() now prepare their own credentials and temporarily override the ones currently on the acting thread, whilst preventing interference from other threads by holding cred_replace_mutex on the thread being dumped. This will be replaced in a future patch by something that hands down the credentials directly to the functions being called, rather than altering the task's objective credentials. (3) LSM interface. A number of functions have been changed, added or removed: (*) security_capset_check(), ->capset_check() (*) security_capset_set(), ->capset_set() Removed in favour of security_capset(). (*) security_capset(), ->capset() New. This is passed a pointer to the new creds, a pointer to the old creds and the proposed capability sets. It should fill in the new creds or return an error. All pointers, barring the pointer to the new creds, are now const. (*) security_bprm_apply_creds(), ->bprm_apply_creds() Changed; now returns a value, which will cause the process to be killed if it's an error. (*) security_task_alloc(), ->task_alloc_security() Removed in favour of security_prepare_creds(). (*) security_cred_free(), ->cred_free() New. Free security data attached to cred->security. (*) security_prepare_creds(), ->cred_prepare() New. Duplicate any security data attached to cred->security. (*) security_commit_creds(), ->cred_commit() New. Apply any security effects for the upcoming installation of new security by commit_creds(). (*) security_task_post_setuid(), ->task_post_setuid() Removed in favour of security_task_fix_setuid(). (*) security_task_fix_setuid(), ->task_fix_setuid() Fix up the proposed new credentials for setuid(). This is used by cap_set_fix_setuid() to implicitly adjust capabilities in line with setuid() changes. Changes are made to the new credentials, rather than the task itself as in security_task_post_setuid(). (*) security_task_reparent_to_init(), ->task_reparent_to_init() Removed. Instead the task being reparented to init is referred directly to init's credentials. NOTE! This results in the loss of some state: SELinux's osid no longer records the sid of the thread that forked it. (*) security_key_alloc(), ->key_alloc() (*) security_key_permission(), ->key_permission() Changed. These now take cred pointers rather than task pointers to refer to the security context. (4) sys_capset(). This has been simplified and uses less locking. The LSM functions it calls have been merged. (5) reparent_to_kthreadd(). This gives the current thread the same credentials as init by simply using commit_thread() to point that way. (6) __sigqueue_alloc() and switch_uid() __sigqueue_alloc() can't stop the target task from changing its creds beneath it, so this function gets a reference to the currently applicable user_struct which it then passes into the sigqueue struct it returns if successful. switch_uid() is now called from commit_creds(), and possibly should be folded into that. commit_creds() should take care of protecting __sigqueue_alloc(). (7) [sg]et[ug]id() and co and [sg]et_current_groups. The set functions now all use prepare_creds(), commit_creds() and abort_creds() to build and check a new set of credentials before applying it. security_task_set[ug]id() is called inside the prepared section. This guarantees that nothing else will affect the creds until we've finished. The calling of set_dumpable() has been moved into commit_creds(). Much of the functionality of set_user() has been moved into commit_creds(). The get functions all simply access the data directly. (8) security_task_prctl() and cap_task_prctl(). security_task_prctl() has been modified to return -ENOSYS if it doesn't want to handle a function, or otherwise return the return value directly rather than through an argument. Additionally, cap_task_prctl() now prepares a new set of credentials, even if it doesn't end up using it. (9) Keyrings. A number of changes have been made to the keyrings code: (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have all been dropped and built in to the credentials functions directly. They may want separating out again later. (b) key_alloc() and search_process_keyrings() now take a cred pointer rather than a task pointer to specify the security context. (c) copy_creds() gives a new thread within the same thread group a new thread keyring if its parent had one, otherwise it discards the thread keyring. (d) The authorisation key now points directly to the credentials to extend the search into rather pointing to the task that carries them. (e) Installing thread, process or session keyrings causes a new set of credentials to be created, even though it's not strictly necessary for process or session keyrings (they're shared). (10) Usermode helper. The usermode helper code now carries a cred struct pointer in its subprocess_info struct instead of a new session keyring pointer. This set of credentials is derived from init_cred and installed on the new process after it has been cloned. call_usermodehelper_setup() allocates the new credentials and call_usermodehelper_freeinfo() discards them if they haven't been used. A special cred function (prepare_usermodeinfo_creds()) is provided specifically for call_usermodehelper_setup() to call. call_usermodehelper_setkeys() adjusts the credentials to sport the supplied keyring as the new session keyring. (11) SELinux. SELinux has a number of changes, in addition to those to support the LSM interface changes mentioned above: (a) selinux_setprocattr() no longer does its check for whether the current ptracer can access processes with the new SID inside the lock that covers getting the ptracer's SID. Whilst this lock ensures that the check is done with the ptracer pinned, the result is only valid until the lock is released, so there's no point doing it inside the lock. (12) is_single_threaded(). This function has been extracted from selinux_setprocattr() and put into a file of its own in the lib/ directory as join_session_keyring() now wants to use it too. The code in SELinux just checked to see whether a task shared mm_structs with other tasks (CLONE_VM), but that isn't good enough. We really want to know if they're part of the same thread group (CLONE_THREAD). (13) nfsd. The NFS server daemon now has to use the COW credentials to set the credentials it is going to use. It really needs to pass the credentials down to the functions it calls, but it can't do that until other patches in this series have been applied. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Signed-off-by: James Morris <jmorris@namei.org>
1000 lines
24 KiB
C
1000 lines
24 KiB
C
/* Keyring handling
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*
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* Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/security.h>
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#include <linux/seq_file.h>
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#include <linux/err.h>
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#include <keys/keyring-type.h>
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#include <asm/uaccess.h>
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#include "internal.h"
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/*
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* when plumbing the depths of the key tree, this sets a hard limit set on how
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* deep we're willing to go
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*/
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#define KEYRING_SEARCH_MAX_DEPTH 6
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/*
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* we keep all named keyrings in a hash to speed looking them up
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*/
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#define KEYRING_NAME_HASH_SIZE (1 << 5)
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static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
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static DEFINE_RWLOCK(keyring_name_lock);
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static inline unsigned keyring_hash(const char *desc)
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{
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unsigned bucket = 0;
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for (; *desc; desc++)
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bucket += (unsigned char) *desc;
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return bucket & (KEYRING_NAME_HASH_SIZE - 1);
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}
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/*
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* the keyring type definition
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*/
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static int keyring_instantiate(struct key *keyring,
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const void *data, size_t datalen);
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static int keyring_match(const struct key *keyring, const void *criterion);
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static void keyring_revoke(struct key *keyring);
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static void keyring_destroy(struct key *keyring);
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static void keyring_describe(const struct key *keyring, struct seq_file *m);
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static long keyring_read(const struct key *keyring,
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char __user *buffer, size_t buflen);
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struct key_type key_type_keyring = {
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.name = "keyring",
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.def_datalen = sizeof(struct keyring_list),
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.instantiate = keyring_instantiate,
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.match = keyring_match,
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.revoke = keyring_revoke,
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.destroy = keyring_destroy,
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.describe = keyring_describe,
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.read = keyring_read,
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};
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EXPORT_SYMBOL(key_type_keyring);
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/*
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* semaphore to serialise link/link calls to prevent two link calls in parallel
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* introducing a cycle
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*/
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static DECLARE_RWSEM(keyring_serialise_link_sem);
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/*****************************************************************************/
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/*
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* publish the name of a keyring so that it can be found by name (if it has
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* one)
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*/
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static void keyring_publish_name(struct key *keyring)
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{
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int bucket;
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if (keyring->description) {
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bucket = keyring_hash(keyring->description);
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write_lock(&keyring_name_lock);
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if (!keyring_name_hash[bucket].next)
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INIT_LIST_HEAD(&keyring_name_hash[bucket]);
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list_add_tail(&keyring->type_data.link,
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&keyring_name_hash[bucket]);
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write_unlock(&keyring_name_lock);
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}
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} /* end keyring_publish_name() */
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/*****************************************************************************/
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/*
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* initialise a keyring
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* - we object if we were given any data
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*/
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static int keyring_instantiate(struct key *keyring,
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const void *data, size_t datalen)
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{
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int ret;
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ret = -EINVAL;
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if (datalen == 0) {
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/* make the keyring available by name if it has one */
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keyring_publish_name(keyring);
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ret = 0;
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}
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return ret;
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} /* end keyring_instantiate() */
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/*****************************************************************************/
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/*
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* match keyrings on their name
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*/
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static int keyring_match(const struct key *keyring, const void *description)
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{
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return keyring->description &&
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strcmp(keyring->description, description) == 0;
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} /* end keyring_match() */
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/*****************************************************************************/
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/*
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* dispose of the data dangling from the corpse of a keyring
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*/
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static void keyring_destroy(struct key *keyring)
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{
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struct keyring_list *klist;
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int loop;
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if (keyring->description) {
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write_lock(&keyring_name_lock);
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if (keyring->type_data.link.next != NULL &&
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!list_empty(&keyring->type_data.link))
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list_del(&keyring->type_data.link);
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write_unlock(&keyring_name_lock);
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}
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klist = rcu_dereference(keyring->payload.subscriptions);
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if (klist) {
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for (loop = klist->nkeys - 1; loop >= 0; loop--)
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key_put(klist->keys[loop]);
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kfree(klist);
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}
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} /* end keyring_destroy() */
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/*****************************************************************************/
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/*
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* describe the keyring
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*/
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static void keyring_describe(const struct key *keyring, struct seq_file *m)
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{
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struct keyring_list *klist;
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if (keyring->description) {
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seq_puts(m, keyring->description);
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}
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else {
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seq_puts(m, "[anon]");
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}
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rcu_read_lock();
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klist = rcu_dereference(keyring->payload.subscriptions);
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if (klist)
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seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
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else
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seq_puts(m, ": empty");
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rcu_read_unlock();
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} /* end keyring_describe() */
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/*****************************************************************************/
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/*
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* read a list of key IDs from the keyring's contents
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* - the keyring's semaphore is read-locked
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*/
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static long keyring_read(const struct key *keyring,
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char __user *buffer, size_t buflen)
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{
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struct keyring_list *klist;
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struct key *key;
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size_t qty, tmp;
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int loop, ret;
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ret = 0;
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klist = rcu_dereference(keyring->payload.subscriptions);
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if (klist) {
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/* calculate how much data we could return */
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qty = klist->nkeys * sizeof(key_serial_t);
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if (buffer && buflen > 0) {
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if (buflen > qty)
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buflen = qty;
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/* copy the IDs of the subscribed keys into the
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* buffer */
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ret = -EFAULT;
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for (loop = 0; loop < klist->nkeys; loop++) {
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key = klist->keys[loop];
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tmp = sizeof(key_serial_t);
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if (tmp > buflen)
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tmp = buflen;
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if (copy_to_user(buffer,
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&key->serial,
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tmp) != 0)
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goto error;
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buflen -= tmp;
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if (buflen == 0)
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break;
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buffer += tmp;
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}
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}
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ret = qty;
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}
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error:
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return ret;
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} /* end keyring_read() */
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/*****************************************************************************/
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/*
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* allocate a keyring and link into the destination keyring
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*/
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struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
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const struct cred *cred, unsigned long flags,
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struct key *dest)
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{
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struct key *keyring;
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int ret;
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keyring = key_alloc(&key_type_keyring, description,
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uid, gid, cred,
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(KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
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flags);
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if (!IS_ERR(keyring)) {
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ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
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if (ret < 0) {
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key_put(keyring);
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keyring = ERR_PTR(ret);
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}
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}
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return keyring;
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} /* end keyring_alloc() */
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/*****************************************************************************/
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/*
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* search the supplied keyring tree for a key that matches the criterion
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* - perform a breadth-then-depth search up to the prescribed limit
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* - we only find keys on which we have search permission
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* - we use the supplied match function to see if the description (or other
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* feature of interest) matches
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* - we rely on RCU to prevent the keyring lists from disappearing on us
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* - we return -EAGAIN if we didn't find any matching key
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* - we return -ENOKEY if we only found negative matching keys
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* - we propagate the possession attribute from the keyring ref to the key ref
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*/
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key_ref_t keyring_search_aux(key_ref_t keyring_ref,
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const struct cred *cred,
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struct key_type *type,
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const void *description,
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key_match_func_t match)
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{
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struct {
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struct keyring_list *keylist;
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int kix;
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} stack[KEYRING_SEARCH_MAX_DEPTH];
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struct keyring_list *keylist;
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struct timespec now;
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unsigned long possessed, kflags;
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struct key *keyring, *key;
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key_ref_t key_ref;
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long err;
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int sp, kix;
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keyring = key_ref_to_ptr(keyring_ref);
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possessed = is_key_possessed(keyring_ref);
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key_check(keyring);
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/* top keyring must have search permission to begin the search */
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err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
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if (err < 0) {
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key_ref = ERR_PTR(err);
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goto error;
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}
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key_ref = ERR_PTR(-ENOTDIR);
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if (keyring->type != &key_type_keyring)
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goto error;
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rcu_read_lock();
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now = current_kernel_time();
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err = -EAGAIN;
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sp = 0;
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/* firstly we should check to see if this top-level keyring is what we
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* are looking for */
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key_ref = ERR_PTR(-EAGAIN);
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kflags = keyring->flags;
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if (keyring->type == type && match(keyring, description)) {
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key = keyring;
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/* check it isn't negative and hasn't expired or been
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* revoked */
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if (kflags & (1 << KEY_FLAG_REVOKED))
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goto error_2;
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if (key->expiry && now.tv_sec >= key->expiry)
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goto error_2;
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key_ref = ERR_PTR(-ENOKEY);
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if (kflags & (1 << KEY_FLAG_NEGATIVE))
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goto error_2;
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goto found;
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}
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/* otherwise, the top keyring must not be revoked, expired, or
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* negatively instantiated if we are to search it */
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key_ref = ERR_PTR(-EAGAIN);
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if (kflags & ((1 << KEY_FLAG_REVOKED) | (1 << KEY_FLAG_NEGATIVE)) ||
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(keyring->expiry && now.tv_sec >= keyring->expiry))
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goto error_2;
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/* start processing a new keyring */
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descend:
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if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
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goto not_this_keyring;
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keylist = rcu_dereference(keyring->payload.subscriptions);
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if (!keylist)
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goto not_this_keyring;
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/* iterate through the keys in this keyring first */
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for (kix = 0; kix < keylist->nkeys; kix++) {
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key = keylist->keys[kix];
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kflags = key->flags;
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/* ignore keys not of this type */
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if (key->type != type)
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continue;
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/* skip revoked keys and expired keys */
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if (kflags & (1 << KEY_FLAG_REVOKED))
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continue;
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if (key->expiry && now.tv_sec >= key->expiry)
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continue;
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/* keys that don't match */
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if (!match(key, description))
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continue;
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/* key must have search permissions */
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if (key_task_permission(make_key_ref(key, possessed),
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cred, KEY_SEARCH) < 0)
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continue;
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/* we set a different error code if we pass a negative key */
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if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
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err = -ENOKEY;
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continue;
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}
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goto found;
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}
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/* search through the keyrings nested in this one */
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kix = 0;
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ascend:
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for (; kix < keylist->nkeys; kix++) {
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key = keylist->keys[kix];
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if (key->type != &key_type_keyring)
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continue;
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/* recursively search nested keyrings
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* - only search keyrings for which we have search permission
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*/
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if (sp >= KEYRING_SEARCH_MAX_DEPTH)
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continue;
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if (key_task_permission(make_key_ref(key, possessed),
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cred, KEY_SEARCH) < 0)
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continue;
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/* stack the current position */
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stack[sp].keylist = keylist;
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stack[sp].kix = kix;
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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;
|
|
|
|
} /* end keyring_search_aux() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* search the supplied keyring tree for a key that matches the criterion
|
|
* - perform a breadth-then-depth search up to the prescribed limit
|
|
* - we only find keys on which we have search permission
|
|
* - we readlock the keyrings as we search down the tree
|
|
* - we return -EAGAIN if we didn't find any matching key
|
|
* - we return -ENOKEY if we only found negative matching keys
|
|
*/
|
|
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);
|
|
|
|
} /* end keyring_search() */
|
|
|
|
EXPORT_SYMBOL(keyring_search);
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* search the given keyring only (no recursion)
|
|
* - keyring must be locked by caller
|
|
* - caller must guarantee that the keyring is a keyring
|
|
*/
|
|
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);
|
|
|
|
} /* end __keyring_search_one() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* find a keyring with the specified name
|
|
* - all named keyrings are searched
|
|
* - normally only finds keyrings with search permission for the current process
|
|
*/
|
|
struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
|
|
{
|
|
struct key *keyring;
|
|
int bucket;
|
|
|
|
keyring = ERR_PTR(-EINVAL);
|
|
if (!name)
|
|
goto error;
|
|
|
|
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 (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 */
|
|
atomic_inc(&keyring->usage);
|
|
read_unlock(&keyring_name_lock);
|
|
goto error;
|
|
}
|
|
}
|
|
|
|
read_unlock(&keyring_name_lock);
|
|
keyring = ERR_PTR(-ENOKEY);
|
|
|
|
error:
|
|
return keyring;
|
|
|
|
} /* end find_keyring_by_name() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* 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;
|
|
|
|
} /* end keyring_detect_cycle() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* dispose of a keyring list after the RCU grace period
|
|
*/
|
|
static void keyring_link_rcu_disposal(struct rcu_head *rcu)
|
|
{
|
|
struct keyring_list *klist =
|
|
container_of(rcu, struct keyring_list, rcu);
|
|
|
|
kfree(klist);
|
|
|
|
} /* end keyring_link_rcu_disposal() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* 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);
|
|
|
|
key_put(klist->keys[klist->delkey]);
|
|
kfree(klist);
|
|
|
|
} /* end keyring_unlink_rcu_disposal() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* link a key into to a keyring
|
|
* - must be called with the keyring's semaphore write-locked
|
|
* - discard already extant link to matching key if there is one
|
|
*/
|
|
int __key_link(struct key *keyring, struct key *key)
|
|
{
|
|
struct keyring_list *klist, *nklist;
|
|
unsigned max;
|
|
size_t size;
|
|
int loop, ret;
|
|
|
|
ret = -EKEYREVOKED;
|
|
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
|
|
goto error;
|
|
|
|
ret = -ENOTDIR;
|
|
if (keyring->type != &key_type_keyring)
|
|
goto error;
|
|
|
|
/* serialise link/link calls to prevent parallel calls causing a
|
|
* cycle when applied to two keyring in opposite orders */
|
|
down_write(&keyring_serialise_link_sem);
|
|
|
|
/* check that we aren't going to create a cycle adding one keyring to
|
|
* another */
|
|
if (key->type == &key_type_keyring) {
|
|
ret = keyring_detect_cycle(keyring, key);
|
|
if (ret < 0)
|
|
goto error2;
|
|
}
|
|
|
|
/* see if there's a matching key we can displace */
|
|
klist = keyring->payload.subscriptions;
|
|
|
|
if (klist && klist->nkeys > 0) {
|
|
struct key_type *type = key->type;
|
|
|
|
for (loop = klist->nkeys - 1; loop >= 0; loop--) {
|
|
if (klist->keys[loop]->type == type &&
|
|
strcmp(klist->keys[loop]->description,
|
|
key->description) == 0
|
|
) {
|
|
/* found a match - replace with 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 error2;
|
|
|
|
/* replace matched key */
|
|
atomic_inc(&key->usage);
|
|
nklist->keys[loop] = key;
|
|
|
|
rcu_assign_pointer(
|
|
keyring->payload.subscriptions,
|
|
nklist);
|
|
|
|
/* dispose of the old keyring list and the
|
|
* displaced key */
|
|
klist->delkey = loop;
|
|
call_rcu(&klist->rcu,
|
|
keyring_unlink_rcu_disposal);
|
|
|
|
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 error2;
|
|
|
|
klist = keyring->payload.subscriptions;
|
|
|
|
if (klist && klist->nkeys < klist->maxkeys) {
|
|
/* there's sufficient slack space to add directly */
|
|
atomic_inc(&key->usage);
|
|
|
|
klist->keys[klist->nkeys] = key;
|
|
smp_wmb();
|
|
klist->nkeys++;
|
|
smp_wmb();
|
|
}
|
|
else {
|
|
/* grow the key list */
|
|
max = 4;
|
|
if (klist)
|
|
max += klist->maxkeys;
|
|
|
|
ret = -ENFILE;
|
|
if (max > 65535)
|
|
goto error3;
|
|
size = sizeof(*klist) + sizeof(struct key *) * max;
|
|
if (size > PAGE_SIZE)
|
|
goto error3;
|
|
|
|
ret = -ENOMEM;
|
|
nklist = kmalloc(size, GFP_KERNEL);
|
|
if (!nklist)
|
|
goto error3;
|
|
nklist->maxkeys = max;
|
|
nklist->nkeys = 0;
|
|
|
|
if (klist) {
|
|
nklist->nkeys = klist->nkeys;
|
|
memcpy(nklist->keys,
|
|
klist->keys,
|
|
sizeof(struct key *) * klist->nkeys);
|
|
}
|
|
|
|
/* add the key into the new space */
|
|
atomic_inc(&key->usage);
|
|
nklist->keys[nklist->nkeys++] = key;
|
|
|
|
rcu_assign_pointer(keyring->payload.subscriptions, nklist);
|
|
|
|
/* dispose of the old keyring list */
|
|
if (klist)
|
|
call_rcu(&klist->rcu, keyring_link_rcu_disposal);
|
|
}
|
|
|
|
done:
|
|
ret = 0;
|
|
error2:
|
|
up_write(&keyring_serialise_link_sem);
|
|
error:
|
|
return ret;
|
|
|
|
error3:
|
|
/* undo the quota changes */
|
|
key_payload_reserve(keyring,
|
|
keyring->datalen - KEYQUOTA_LINK_BYTES);
|
|
goto error2;
|
|
|
|
} /* end __key_link() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* link a key to a keyring
|
|
*/
|
|
int key_link(struct key *keyring, struct key *key)
|
|
{
|
|
int ret;
|
|
|
|
key_check(keyring);
|
|
key_check(key);
|
|
|
|
down_write(&keyring->sem);
|
|
ret = __key_link(keyring, key);
|
|
up_write(&keyring->sem);
|
|
|
|
return ret;
|
|
|
|
} /* end key_link() */
|
|
|
|
EXPORT_SYMBOL(key_link);
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* unlink the first link to a key from a keyring
|
|
*/
|
|
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 = keyring->payload.subscriptions;
|
|
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;
|
|
|
|
} /* end key_unlink() */
|
|
|
|
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);
|
|
|
|
} /* end keyring_clear_rcu_disposal() */
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* clear the specified process keyring
|
|
* - implements keyctl(KEYCTL_CLEAR)
|
|
*/
|
|
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 = keyring->payload.subscriptions;
|
|
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;
|
|
|
|
} /* end keyring_clear() */
|
|
|
|
EXPORT_SYMBOL(keyring_clear);
|
|
|
|
/*****************************************************************************/
|
|
/*
|
|
* dispose of the links from a revoked keyring
|
|
* - called with the key sem write-locked
|
|
*/
|
|
static void keyring_revoke(struct key *keyring)
|
|
{
|
|
struct keyring_list *klist = keyring->payload.subscriptions;
|
|
|
|
/* 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);
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|
}
|
|
|
|
} /* end keyring_revoke() */
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