cregit-Linux how code gets into the kernel

Release 4.15 security/keys/key.c

Directory: security/keys
/* Basic authentication token and access key management
 *
 * Copyright (C) 2004-2008 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/poison.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/workqueue.h>
#include <linux/random.h>
#include <linux/err.h>
#include "internal.h"


struct kmem_cache *key_jar;

struct rb_root		key_serial_tree; 
/* tree of keys indexed by serial */

DEFINE_SPINLOCK(key_serial_lock);


struct rb_root	key_user_tree; 
/* tree of quota records indexed by UID */

DEFINE_SPINLOCK(key_user_lock);


unsigned int key_quota_root_maxkeys = 1000000;	
/* root's key count quota */

unsigned int key_quota_root_maxbytes = 25000000; 
/* root's key space quota */

unsigned int key_quota_maxkeys = 200;		
/* general key count quota */

unsigned int key_quota_maxbytes = 20000;	
/* general key space quota */

static LIST_HEAD(key_types_list);
static DECLARE_RWSEM(key_types_sem);

/* We serialise key instantiation and link */

DEFINE_MUTEX(key_construction_mutex);

#ifdef KEY_DEBUGGING

void __key_check(const struct key *key) { printk("__key_check: key %p {%08x} should be {%08x}\n", key, key->magic, KEY_DEBUG_MAGIC); BUG(); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells27100.00%1100.00%
Total27100.00%1100.00%

#endif /* * Get the key quota record for a user, allocating a new record if one doesn't * already exist. */
struct key_user *key_user_lookup(kuid_t uid) { struct key_user *candidate = NULL, *user; struct rb_node *parent, **p; try_again: parent = NULL; p = &key_user_tree.rb_node; spin_lock(&key_user_lock); /* search the tree for a user record with a matching UID */ while (*p) { parent = *p; user = rb_entry(parent, struct key_user, node); if (uid_lt(uid, user->uid)) p = &(*p)->rb_left; else if (uid_gt(uid, user->uid)) p = &(*p)->rb_right; else goto found; } /* if we get here, we failed to find a match in the tree */ if (!candidate) { /* allocate a candidate user record if we don't already have * one */ spin_unlock(&key_user_lock); user = NULL; candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL); if (unlikely(!candidate)) goto out; /* the allocation may have scheduled, so we need to repeat the * search lest someone else added the record whilst we were * asleep */ goto try_again; } /* if we get here, then the user record still hadn't appeared on the * second pass - so we use the candidate record */ refcount_set(&candidate->usage, 1); atomic_set(&candidate->nkeys, 0); atomic_set(&candidate->nikeys, 0); candidate->uid = uid; candidate->qnkeys = 0; candidate->qnbytes = 0; spin_lock_init(&candidate->lock); mutex_init(&candidate->cons_lock); rb_link_node(&candidate->node, parent, p); rb_insert_color(&candidate->node, &key_user_tree); spin_unlock(&key_user_lock); user = candidate; goto out; /* okay - we found a user record for this UID */ found: refcount_inc(&user->usage); spin_unlock(&key_user_lock); kfree(candidate); out: return user; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells26288.81%228.57%
Serge E. Hallyn113.73%114.29%
Eric W. Biedermann93.05%114.29%
Alexander Nyberg62.03%114.29%
Eric Biggers51.69%114.29%
Elena Reshetova20.68%114.29%
Total295100.00%7100.00%

/* * Dispose of a user structure */
void key_user_put(struct key_user *user) { if (refcount_dec_and_lock(&user->usage, &key_user_lock)) { rb_erase(&user->node, &key_user_tree); spin_unlock(&key_user_lock); kfree(user); } }

Contributors

PersonTokensPropCommitsCommitProp
David Howells4697.87%150.00%
Elena Reshetova12.13%150.00%
Total47100.00%2100.00%

/* * Allocate a serial number for a key. These are assigned randomly to avoid * security issues through covert channel problems. */
static inline void key_alloc_serial(struct key *key) { struct rb_node *parent, **p; struct key *xkey; /* propose a random serial number and look for a hole for it in the * serial number tree */ do { get_random_bytes(&key->serial, sizeof(key->serial)); key->serial >>= 1; /* negative numbers are not permitted */ } while (key->serial < 3); spin_lock(&key_serial_lock); attempt_insertion: parent = NULL; p = &key_serial_tree.rb_node; while (*p) { parent = *p; xkey = rb_entry(parent, struct key, serial_node); if (key->serial < xkey->serial) p = &(*p)->rb_left; else if (key->serial > xkey->serial) p = &(*p)->rb_right; else goto serial_exists; } /* we've found a suitable hole - arrange for this key to occupy it */ rb_link_node(&key->serial_node, parent, p); rb_insert_color(&key->serial_node, &key_serial_tree); spin_unlock(&key_serial_lock); return; /* we found a key with the proposed serial number - walk the tree from * that point looking for the next unused serial number */ serial_exists: for (;;) { key->serial++; if (key->serial < 3) { key->serial = 3; goto attempt_insertion; } parent = rb_next(parent); if (!parent) goto attempt_insertion; xkey = rb_entry(parent, struct key, serial_node); if (key->serial < xkey->serial) goto attempt_insertion; } }

Contributors

PersonTokensPropCommitsCommitProp
David Howells22889.76%266.67%
Michael LeMay2610.24%133.33%
Total254100.00%3100.00%

/** * key_alloc - Allocate a key of the specified type. * @type: The type of key to allocate. * @desc: The key description to allow the key to be searched out. * @uid: The owner of the new key. * @gid: The group ID for the new key's group permissions. * @cred: The credentials specifying UID namespace. * @perm: The permissions mask of the new key. * @flags: Flags specifying quota properties. * @restrict_link: Optional link restriction for new keyrings. * * Allocate a key of the specified type with the attributes given. The key is * returned in an uninstantiated state and the caller needs to instantiate the * key before returning. * * The restrict_link structure (if not NULL) will be freed when the * keyring is destroyed, so it must be dynamically allocated. * * The user's key count quota is updated to reflect the creation of the key and * the user's key data quota has the default for the key type reserved. The * instantiation function should amend this as necessary. If insufficient * quota is available, -EDQUOT will be returned. * * The LSM security modules can prevent a key being created, in which case * -EACCES will be returned. * * Returns a pointer to the new key if successful and an error code otherwise. * * Note that the caller needs to ensure the key type isn't uninstantiated. * Internally this can be done by locking key_types_sem. Externally, this can * be done by either never unregistering the key type, or making sure * key_alloc() calls don't race with module unloading. */
struct key *key_alloc(struct key_type *type, const char *desc, kuid_t uid, kgid_t gid, const struct cred *cred, key_perm_t perm, unsigned long flags, struct key_restriction *restrict_link) { struct key_user *user = NULL; struct key *key; size_t desclen, quotalen; int ret; key = ERR_PTR(-EINVAL); if (!desc || !*desc) goto error; if (type->vet_description) { ret = type->vet_description(desc); if (ret < 0) { key = ERR_PTR(ret); goto error; } } desclen = strlen(desc); quotalen = desclen + 1 + type->def_datalen; /* get hold of the key tracking for this user */ user = key_user_lookup(uid); if (!user) goto no_memory_1; /* check that the user's quota permits allocation of another key and * its description */ if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) { unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ? key_quota_root_maxkeys : key_quota_maxkeys; unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ? key_quota_root_maxbytes : key_quota_maxbytes; spin_lock(&user->lock); if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) { if (user->qnkeys + 1 >= maxkeys || user->qnbytes + quotalen >= maxbytes || user->qnbytes + quotalen < user->qnbytes) goto no_quota; } user->qnkeys++; user->qnbytes += quotalen; spin_unlock(&user->lock); } /* allocate and initialise the key and its description */ key = kmem_cache_zalloc(key_jar, GFP_KERNEL); if (!key) goto no_memory_2; key->index_key.desc_len = desclen; key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL); if (!key->index_key.description) goto no_memory_3; refcount_set(&key->usage, 1); init_rwsem(&key->sem); lockdep_set_class(&key->sem, &type->lock_class); key->index_key.type = type; key->user = user; key->quotalen = quotalen; key->datalen = type->def_datalen; key->uid = uid; key->gid = gid; key->perm = perm; key->restrict_link = restrict_link; if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) key->flags |= 1 << KEY_FLAG_IN_QUOTA; if (flags & KEY_ALLOC_BUILT_IN) key->flags |= 1 << KEY_FLAG_BUILTIN; if (flags & KEY_ALLOC_UID_KEYRING) key->flags |= 1 << KEY_FLAG_UID_KEYRING; #ifdef KEY_DEBUGGING key->magic = KEY_DEBUG_MAGIC; #endif /* let the security module know about the key */ ret = security_key_alloc(key, cred, flags); if (ret < 0) goto security_error; /* publish the key by giving it a serial number */ atomic_inc(&user->nkeys); key_alloc_serial(key); error: return key; security_error: kfree(key->description); kmem_cache_free(key_jar, key); if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) { spin_lock(&user->lock); user->qnkeys--; user->qnbytes -= quotalen; spin_unlock(&user->lock); } key_user_put(user); key = ERR_PTR(ret); goto error; no_memory_3: kmem_cache_free(key_jar, key); no_memory_2: if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) { spin_lock(&user->lock); user->qnkeys--; user->qnbytes -= quotalen; spin_unlock(&user->lock); } key_user_put(user); no_memory_1: key = ERR_PTR(-ENOMEM); goto error; no_quota: spin_unlock(&user->lock); key_user_put(user); key = ERR_PTR(-EDQUOT); goto error; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells61493.88%1463.64%
Eric Biggers142.14%14.55%
Eric W. Biedermann121.83%14.55%
Michael LeMay40.61%14.55%
Eric Sesterhenn / Snakebyte30.46%14.55%
Mat Martineau30.46%14.55%
Insu Yun20.31%14.55%
Elena Reshetova10.15%14.55%
Christoph Lameter10.15%14.55%
Total654100.00%22100.00%

EXPORT_SYMBOL(key_alloc); /** * key_payload_reserve - Adjust data quota reservation for the key's payload * @key: The key to make the reservation for. * @datalen: The amount of data payload the caller now wants. * * Adjust the amount of the owning user's key data quota that a key reserves. * If the amount is increased, then -EDQUOT may be returned if there isn't * enough free quota available. * * If successful, 0 is returned. */
int key_payload_reserve(struct key *key, size_t datalen) { int delta = (int)datalen - key->datalen; int ret = 0; key_check(key); /* contemplate the quota adjustment */ if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) { unsigned maxbytes = uid_eq(key->user->uid, GLOBAL_ROOT_UID) ? key_quota_root_maxbytes : key_quota_maxbytes; spin_lock(&key->user->lock); if (delta > 0 && (key->user->qnbytes + delta >= maxbytes || key->user->qnbytes + delta < key->user->qnbytes)) { ret = -EDQUOT; } else { key->user->qnbytes += delta; key->quotalen += delta; } spin_unlock(&key->user->lock); } /* change the recorded data length if that didn't generate an error */ if (ret == 0) key->datalen = datalen; return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells15996.95%375.00%
Eric W. Biedermann53.05%125.00%
Total164100.00%4100.00%

EXPORT_SYMBOL(key_payload_reserve); /* * Change the key state to being instantiated. */
static void mark_key_instantiated(struct key *key, int reject_error) { /* Commit the payload before setting the state; barrier versus * key_read_state(). */ smp_store_release(&key->state, (reject_error < 0) ? reject_error : KEY_IS_POSITIVE); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells33100.00%1100.00%
Total33100.00%1100.00%

/* * Instantiate a key and link it into the target keyring atomically. Must be * called with the target keyring's semaphore writelocked. The target key's * semaphore need not be locked as instantiation is serialised by * key_construction_mutex. */
static int __key_instantiate_and_link(struct key *key, struct key_preparsed_payload *prep, struct key *keyring, struct key *authkey, struct assoc_array_edit **_edit) { int ret, awaken; key_check(key); key_check(keyring); awaken = 0; ret = -EBUSY; mutex_lock(&key_construction_mutex); /* can't instantiate twice */ if (key->state == KEY_IS_UNINSTANTIATED) { /* instantiate the key */ ret = key->type->instantiate(key, prep); if (ret == 0) { /* mark the key as being instantiated */ atomic_inc(&key->user->nikeys); mark_key_instantiated(key, 0); if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) awaken = 1; /* and link it into the destination keyring */ if (keyring) { if (test_bit(KEY_FLAG_KEEP, &keyring->flags)) set_bit(KEY_FLAG_KEEP, &key->flags); __key_link(key, _edit); } /* disable the authorisation key */ if (authkey) key_revoke(authkey); if (prep->expiry != TIME64_MAX) { key->expiry = prep->expiry; key_schedule_gc(prep->expiry + key_gc_delay); } } } mutex_unlock(&key_construction_mutex); /* wake up anyone waiting for a key to be constructed */ if (awaken) wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells21394.25%1184.62%
Mimi Zohar125.31%17.69%
Baolin Wang10.44%17.69%
Total226100.00%13100.00%

/** * key_instantiate_and_link - Instantiate a key and link it into the keyring. * @key: The key to instantiate. * @data: The data to use to instantiate the keyring. * @datalen: The length of @data. * @keyring: Keyring to create a link in on success (or NULL). * @authkey: The authorisation token permitting instantiation. * * Instantiate a key that's in the uninstantiated state using the provided data * and, if successful, link it in to the destination keyring if one is * supplied. * * If successful, 0 is returned, the authorisation token is revoked and anyone * waiting for the key is woken up. If the key was already instantiated, * -EBUSY will be returned. */
int key_instantiate_and_link(struct key *key, const void *data, size_t datalen, struct key *keyring, struct key *authkey) { struct key_preparsed_payload prep; struct assoc_array_edit *edit; int ret; memset(&prep, 0, sizeof(prep)); prep.data = data; prep.datalen = datalen; prep.quotalen = key->type->def_datalen; prep.expiry = TIME64_MAX; if (key->type->preparse) { ret = key->type->preparse(&prep); if (ret < 0) goto error; } if (keyring) { ret = __key_link_begin(keyring, &key->index_key, &edit); if (ret < 0) goto error; if (keyring->restrict_link && keyring->restrict_link->check) { struct key_restriction *keyres = keyring->restrict_link; ret = keyres->check(keyring, key->type, &prep.payload, keyres->key); if (ret < 0) goto error_link_end; } } ret = __key_instantiate_and_link(key, &prep, keyring, authkey, &edit); error_link_end: if (keyring) __key_link_end(keyring, &key->index_key, edit); error: if (key->type->preparse) key->type->free_preparse(&prep); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells20580.71%1071.43%
Mat Martineau4818.90%321.43%
Baolin Wang10.39%17.14%
Total254100.00%14100.00%

EXPORT_SYMBOL(key_instantiate_and_link); /** * key_reject_and_link - Negatively instantiate a key and link it into the keyring. * @key: The key to instantiate. * @timeout: The timeout on the negative key. * @error: The error to return when the key is hit. * @keyring: Keyring to create a link in on success (or NULL). * @authkey: The authorisation token permitting instantiation. * * Negatively instantiate a key that's in the uninstantiated state and, if * successful, set its timeout and stored error and link it in to the * destination keyring if one is supplied. The key and any links to the key * will be automatically garbage collected after the timeout expires. * * Negative keys are used to rate limit repeated request_key() calls by causing * them to return the stored error code (typically ENOKEY) until the negative * key expires. * * If successful, 0 is returned, the authorisation token is revoked and anyone * waiting for the key is woken up. If the key was already instantiated, * -EBUSY will be returned. */
int key_reject_and_link(struct key *key, unsigned timeout, unsigned error, struct key *keyring, struct key *authkey) { struct assoc_array_edit *edit; int ret, awaken, link_ret = 0; key_check(key); key_check(keyring); awaken = 0; ret = -EBUSY; if (keyring) { if (keyring->restrict_link) return -EPERM; link_ret = __key_link_begin(keyring, &key->index_key, &edit); } mutex_lock(&key_construction_mutex); /* can't instantiate twice */ if (key->state == KEY_IS_UNINSTANTIATED) { /* mark the key as being negatively instantiated */ atomic_inc(&key->user->nikeys); mark_key_instantiated(key, -error); key->expiry = ktime_get_real_seconds() + timeout; key_schedule_gc(key->expiry + key_gc_delay); if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) awaken = 1; ret = 0; /* and link it into the destination keyring */ if (keyring && link_ret == 0) __key_link(key, &edit); /* disable the authorisation key */ if (authkey) key_revoke(authkey); } mutex_unlock(&key_construction_mutex); if (keyring && link_ret == 0) __key_link_end(keyring, &key->index_key, edit); /* wake up anyone waiting for a key to be constructed */ if (awaken) wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT); return ret == 0 ? link_ret : ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells23597.51%1386.67%
Dan Carpenter41.66%16.67%
Baolin Wang20.83%16.67%
Total241100.00%15100.00%

EXPORT_SYMBOL(key_reject_and_link); /** * key_put - Discard a reference to a key. * @key: The key to discard a reference from. * * Discard a reference to a key, and when all the references are gone, we * schedule the cleanup task to come and pull it out of the tree in process * context at some later time. */
void key_put(struct key *key) { if (key) { key_check(key); if (refcount_dec_and_test(&key->usage)) schedule_work(&key_gc_work); } }

Contributors

PersonTokensPropCommitsCommitProp
David Howells3594.59%250.00%
Elena Reshetova12.70%125.00%
Tejun Heo12.70%125.00%
Total37100.00%4100.00%

EXPORT_SYMBOL(key_put); /* * Find a key by its serial number. */
struct key *key_lookup(key_serial_t id) { struct rb_node *n; struct key *key; spin_lock(&key_serial_lock); /* search the tree for the specified key */ n = key_serial_tree.rb_node; while (n) { key = rb_entry(n, struct key, serial_node); if (id < key->serial) n = n->rb_left; else if (id > key->serial) n = n->rb_right; else goto found; } not_found: key = ERR_PTR(-ENOKEY); goto error; found: /* A key is allowed to be looked up only if someone still owns a * reference to it - otherwise it's awaiting the gc. */ if (!refcount_inc_not_zero(&key->usage)) goto not_found; error: spin_unlock(&key_serial_lock); return key; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells12297.60%266.67%
Mark Rutland32.40%133.33%
Total125100.00%3100.00%

/* * Find and lock the specified key type against removal. * * We return with the sem read-locked if successful. If the type wasn't * available -ENOKEY is returned instead. */
struct key_type *key_type_lookup(const char *type) { struct key_type *ktype; down_read(&key_types_sem); /* look up the key type to see if it's one of the registered kernel * types */ list_for_each_entry(ktype, &key_types_list, link) { if (strcmp(ktype->name, type) == 0) goto found_kernel_type; } up_read(&key_types_sem); ktype = ERR_PTR(-ENOKEY); found_kernel_type: return ktype; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells69100.00%1100.00%
Total69100.00%1100.00%


void key_set_timeout(struct key *key, unsigned timeout) { time64_t expiry = 0; /* make the changes with the locks held to prevent races */ down_write(&key->sem); if (timeout > 0) expiry = ktime_get_real_seconds() + timeout; key->expiry = expiry; key_schedule_gc(key->expiry + key_gc_delay); up_write(&key->sem); }

Contributors

PersonTokensPropCommitsCommitProp
Bryan Schumaker6095.24%150.00%
Baolin Wang34.76%150.00%
Total63100.00%2100.00%

EXPORT_SYMBOL_GPL(key_set_timeout); /* * Unlock a key type locked by key_type_lookup(). */
void key_type_put(struct key_type *ktype) { up_read(&key_types_sem); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells16100.00%1100.00%
Total16100.00%1100.00%

/* * Attempt to update an existing key. * * The key is given to us with an incremented refcount that we need to discard * if we get an error. */
static inline key_ref_t __key_update(key_ref_t key_ref, struct key_preparsed_payload *prep) { struct key *key = key_ref_to_ptr(key_ref); int ret; /* need write permission on the key to update it */ ret = key_permission(key_ref, KEY_NEED_WRITE); if (ret < 0) goto error; ret = -EEXIST; if (!key->type->update) goto error;