diff options
| -rw-r--r-- | Documentation/keys.txt | 19 | ||||
| -rw-r--r-- | include/linux/key.h | 5 | ||||
| -rw-r--r-- | security/keys/Makefile | 1 | ||||
| -rw-r--r-- | security/keys/gc.c | 193 | ||||
| -rw-r--r-- | security/keys/internal.h | 4 | ||||
| -rw-r--r-- | security/keys/key.c | 14 | ||||
| -rw-r--r-- | security/keys/keyctl.c | 1 | ||||
| -rw-r--r-- | security/keys/keyring.c | 85 | ||||
| -rw-r--r-- | security/keys/sysctl.c | 28 |
9 files changed, 344 insertions, 6 deletions
diff --git a/Documentation/keys.txt b/Documentation/keys.txt index b56aacc1fff..203487e9b1d 100644 --- a/Documentation/keys.txt +++ b/Documentation/keys.txt @@ -26,7 +26,7 @@ This document has the following sections: - Notes on accessing payload contents - Defining a key type - Request-key callback service - - Key access filesystem + - Garbage collection ============ @@ -113,6 +113,9 @@ Each key has a number of attributes: (*) Dead. The key's type was unregistered, and so the key is now useless. +Keys in the last three states are subject to garbage collection. See the +section on "Garbage collection". + ==================== KEY SERVICE OVERVIEW @@ -1231,3 +1234,17 @@ by executing: In this case, the program isn't required to actually attach the key to a ring; the rings are provided for reference. + + +================== +GARBAGE COLLECTION +================== + +Dead keys (for which the type has been removed) will be automatically unlinked +from those keyrings that point to them and deleted as soon as possible by a +background garbage collector. + +Similarly, revoked and expired keys will be garbage collected, but only after a +certain amount of time has passed. This time is set as a number of seconds in: + + /proc/sys/kernel/keys/gc_delay diff --git a/include/linux/key.h b/include/linux/key.h index e544f466d69..33e0165de10 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -129,7 +129,10 @@ struct key { struct rw_semaphore sem; /* change vs change sem */ struct key_user *user; /* owner of this key */ void *security; /* security data for this key */ - time_t expiry; /* time at which key expires (or 0) */ + union { + time_t expiry; /* time at which key expires (or 0) */ + time_t revoked_at; /* time at which key was revoked */ + }; uid_t uid; gid_t gid; key_perm_t perm; /* access permissions */ diff --git a/security/keys/Makefile b/security/keys/Makefile index 747a464943a..74d5447d7df 100644 --- a/security/keys/Makefile +++ b/security/keys/Makefile @@ -3,6 +3,7 @@ # obj-y := \ + gc.o \ key.o \ keyring.o \ keyctl.o \ diff --git a/security/keys/gc.c b/security/keys/gc.c new file mode 100644 index 00000000000..44adc325e15 --- /dev/null +++ b/security/keys/gc.c @@ -0,0 +1,193 @@ +/* Key garbage collector + * + * Copyright (C) 2009 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 Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include <linux/module.h> +#include <keys/keyring-type.h> +#include "internal.h" + +/* + * Delay between key revocation/expiry in seconds + */ +unsigned key_gc_delay = 5 * 60; + +/* + * Reaper + */ +static void key_gc_timer_func(unsigned long); +static void key_garbage_collector(struct work_struct *); +static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0); +static DECLARE_WORK(key_gc_work, key_garbage_collector); +static key_serial_t key_gc_cursor; /* the last key the gc considered */ +static unsigned long key_gc_executing; +static time_t key_gc_next_run = LONG_MAX; + +/* + * Schedule a garbage collection run + * - precision isn't particularly important + */ +void key_schedule_gc(time_t gc_at) +{ + unsigned long expires; + time_t now = current_kernel_time().tv_sec; + + kenter("%ld", gc_at - now); + + gc_at += key_gc_delay; + + if (now >= gc_at) { + schedule_work(&key_gc_work); + } else if (gc_at < key_gc_next_run) { + expires = jiffies + (gc_at - now) * HZ; + mod_timer(&key_gc_timer, expires); + } +} + +/* + * The garbage collector timer kicked off + */ +static void key_gc_timer_func(unsigned long data) +{ + kenter(""); + key_gc_next_run = LONG_MAX; + schedule_work(&key_gc_work); +} + +/* + * Garbage collect pointers from a keyring + * - return true if we altered the keyring + */ +static bool key_gc_keyring(struct key *keyring, time_t limit) +{ + struct keyring_list *klist; + struct key *key; + int loop; + + kenter("%x", key_serial(keyring)); + + if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) + goto dont_gc; + + /* scan the keyring looking for dead keys */ + klist = rcu_dereference(keyring->payload.subscriptions); + if (!klist) + goto dont_gc; + + for (loop = klist->nkeys - 1; loop >= 0; loop--) { + key = klist->keys[loop]; + if (test_bit(KEY_FLAG_DEAD, &key->flags) || + (key->expiry > 0 && key->expiry <= limit)) + goto do_gc; + } + +dont_gc: + kleave(" = false"); + return false; + +do_gc: + key_gc_cursor = keyring->serial; + key_get(keyring); + spin_unlock(&key_serial_lock); + keyring_gc(keyring, limit); + key_put(keyring); + kleave(" = true"); + return true; +} + +/* + * Garbage collector for keys + * - this involves scanning the keyrings for dead, expired and revoked keys + * that have overstayed their welcome + */ +static void key_garbage_collector(struct work_struct *work) +{ + struct rb_node *rb; + key_serial_t cursor; + struct key *key, *xkey; + time_t new_timer = LONG_MAX, limit; + + kenter(""); + + if (test_and_set_bit(0, &key_gc_executing)) { + key_schedule_gc(current_kernel_time().tv_sec); + return; + } + + limit = current_kernel_time().tv_sec; + if (limit > key_gc_delay) + limit -= key_gc_delay; + else + limit = key_gc_delay; + + spin_lock(&key_serial_lock); + + if (RB_EMPTY_ROOT(&key_serial_tree)) + goto reached_the_end; + + cursor = key_gc_cursor; + if (cursor < 0) + cursor = 0; + + /* find the first key above the cursor */ + key = NULL; + rb = key_serial_tree.rb_node; + while (rb) { + xkey = rb_entry(rb, struct key, serial_node); + if (cursor < xkey->serial) { + key = xkey; + rb = rb->rb_left; + } else if (cursor > xkey->serial) { + rb = rb->rb_right; + } else { + rb = rb_next(rb); + if (!rb) + goto reached_the_end; + key = rb_entry(rb, struct key, serial_node); + break; + } + } + + if (!key) + goto reached_the_end; + + /* trawl through the keys looking for keyrings */ + for (;;) { + if (key->expiry > 0 && key->expiry < new_timer) + new_timer = key->expiry; + + if (key->type == &key_type_keyring && + key_gc_keyring(key, limit)) { + /* the gc ate our lock */ + schedule_work(&key_gc_work); + goto no_unlock; + } + + rb = rb_next(&key->serial_node); + if (!rb) { + key_gc_cursor = 0; + break; + } + key = rb_entry(rb, struct key, serial_node); + } + +out: + spin_unlock(&key_serial_lock); +no_unlock: + clear_bit(0, &key_gc_executing); + if (new_timer < LONG_MAX) + key_schedule_gc(new_timer); + + kleave(""); + return; + +reached_the_end: + key_gc_cursor = 0; + goto out; +} diff --git a/security/keys/internal.h b/security/keys/internal.h index a7252e7b2e0..fb830514c33 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -132,6 +132,10 @@ extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags, extern long join_session_keyring(const char *name); +extern unsigned key_gc_delay; +extern void keyring_gc(struct key *keyring, time_t limit); +extern void key_schedule_gc(time_t expiry_at); + /* * check to see whether permission is granted to use a key in the desired way */ diff --git a/security/keys/key.c b/security/keys/key.c index bd9d2670e9c..08531ad0f25 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -500,6 +500,7 @@ int key_negate_and_link(struct key *key, set_bit(KEY_FLAG_INSTANTIATED, &key->flags); now = current_kernel_time(); key->expiry = now.tv_sec + timeout; + key_schedule_gc(key->expiry); if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags)) awaken = 1; @@ -888,6 +889,9 @@ EXPORT_SYMBOL(key_update); */ void key_revoke(struct key *key) { + struct timespec now; + time_t time; + key_check(key); /* make sure no one's trying to change or use the key when we mark it @@ -900,6 +904,14 @@ void key_revoke(struct key *key) key->type->revoke) key->type->revoke(key); + /* set the death time to no more than the expiry time */ + now = current_kernel_time(); + time = now.tv_sec; + if (key->revoked_at == 0 || key->revoked_at > time) { + key->revoked_at = time; + key_schedule_gc(key->revoked_at); + } + up_write(&key->sem); } /* end key_revoke() */ @@ -984,6 +996,8 @@ void unregister_key_type(struct key_type *ktype) spin_unlock(&key_serial_lock); up_write(&key_types_sem); + key_schedule_gc(0); + } /* end unregister_key_type() */ EXPORT_SYMBOL(unregister_key_type); diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 1160b644dac..736d7800f97 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -1115,6 +1115,7 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout) } key->expiry = expiry; + key_schedule_gc(key->expiry); up_write(&key->sem); key_put(key); diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 3dba81c2eba..ac977f661a7 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1000,3 +1000,88 @@ static void keyring_revoke(struct key *keyring) } } /* end keyring_revoke() */ + +/* + * 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 + */ +void keyring_gc(struct key *keyring, time_t limit) +{ + struct keyring_list *klist, *new; + struct key *key; + int loop, keep, max; + + kenter("%x", key_serial(keyring)); + + down_write(&keyring->sem); + + klist = keyring->payload.subscriptions; + if (!klist) + goto just_return; + + /* 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 just_return; + 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); +just_return: + up_write(&keyring->sem); + kleave(" [no]"); +} diff --git a/security/keys/sysctl.c b/security/keys/sysctl.c index b611d493c2d..5e05dc09e2d 100644 --- a/security/keys/sysctl.c +++ b/security/keys/sysctl.c @@ -13,6 +13,8 @@ #include <linux/sysctl.h> #include "internal.h" +static const int zero, one = 1, max = INT_MAX; + ctl_table key_sysctls[] = { { .ctl_name = CTL_UNNUMBERED, @@ -20,7 +22,9 @@ ctl_table key_sysctls[] = { .data = &key_quota_maxkeys, .maxlen = sizeof(unsigned), .mode = 0644, - .proc_handler = &proc_dointvec, + .proc_handler = &proc_dointvec_minmax, + .extra1 = (void *) &one, + .extra2 = (void *) &max, }, { .ctl_name = CTL_UNNUMBERED, @@ -28,7 +32,9 @@ ctl_table key_sysctls[] = { .data = &key_quota_maxbytes, .maxlen = sizeof(unsigned), .mode = 0644, - .proc_handler = &proc_dointvec, + .proc_handler = &proc_dointvec_minmax, + .extra1 = (void *) &one, + .extra2 = (void *) &max, }, { .ctl_name = CTL_UNNUMBERED, @@ -36,7 +42,9 @@ ctl_table key_sysctls[] = { .data = &key_quota_root_maxkeys, .maxlen = sizeof(unsigned), .mode = 0644, - .proc_handler = &proc_dointvec, + .proc_handler = &proc_dointvec_minmax, + .extra1 = (void *) &one, + .extra2 = (void *) &max, }, { .ctl_name = CTL_UNNUMBERED, @@ -44,7 +52,19 @@ ctl_table key_sysctls[] = { .data = &key_quota_root_maxbytes, .maxlen = sizeof(unsigned), .mode = 0644, - .proc_handler = &proc_dointvec, + .proc_handler = &proc_dointvec_minmax, + .extra1 = (void *) &one, + .extra2 = (void *) &max, + }, + { + .ctl_name = CTL_UNNUMBERED, + .procname = "gc_delay", + .data = &key_gc_delay, + .maxlen = sizeof(unsigned), + .mode = 0644, + .proc_handler = &proc_dointvec_minmax, + .extra1 = (void *) &zero, + .extra2 = (void *) &max, }, { .ctl_name = 0 } }; 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