From 5d135440faf7db8d566de0c6fab36b16cf9cfc3b Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 2 Sep 2009 09:14:00 +0100 Subject: KEYS: Add garbage collection for dead, revoked and expired keys. [try #6] Add garbage collection for dead, revoked and expired keys. This involved erasing all links to such keys from keyrings that point to them. At that point, the key will be deleted in the normal manner. Keyrings from which garbage collection occurs are shrunk and their quota consumption reduced as appropriate. Dead keys (for which the key type has been removed) will be garbage collected immediately. Revoked and expired keys will hang around for a number of seconds, as set in /proc/sys/kernel/keys/gc_delay before being automatically removed. The default is 5 minutes. Signed-off-by: David Howells Signed-off-by: James Morris --- security/keys/gc.c | 193 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 193 insertions(+) create mode 100644 security/keys/gc.c (limited to 'security/keys/gc.c') diff --git a/security/keys/gc.c b/security/keys/gc.c new file mode 100644 index 0000000..44adc32 --- /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 +#include +#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; +} -- cgit v1.1 From ee18d64c1f632043a02e6f5ba5e045bb26a5465f Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 2 Sep 2009 09:14:21 +0100 Subject: KEYS: Add a keyctl to install a process's session keyring on its parent [try #6] Add a keyctl to install a process's session keyring onto its parent. This replaces the parent's session keyring. Because the COW credential code does not permit one process to change another process's credentials directly, the change is deferred until userspace next starts executing again. Normally this will be after a wait*() syscall. To support this, three new security hooks have been provided: cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in the blank security creds and key_session_to_parent() - which asks the LSM if the process may replace its parent's session keyring. The replacement may only happen if the process has the same ownership details as its parent, and the process has LINK permission on the session keyring, and the session keyring is owned by the process, and the LSM permits it. Note that this requires alteration to each architecture's notify_resume path. This has been done for all arches barring blackfin, m68k* and xtensa, all of which need assembly alteration to support TIF_NOTIFY_RESUME. This allows the replacement to be performed at the point the parent process resumes userspace execution. This allows the userspace AFS pioctl emulation to fully emulate newpag() and the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to alter the parent process's PAG membership. However, since kAFS doesn't use PAGs per se, but rather dumps the keys into the session keyring, the session keyring of the parent must be replaced if, for example, VIOCSETTOK is passed the newpag flag. This can be tested with the following program: #include #include #include #define KEYCTL_SESSION_TO_PARENT 18 #define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0) int main(int argc, char **argv) { key_serial_t keyring, key; long ret; keyring = keyctl_join_session_keyring(argv[1]); OSERROR(keyring, "keyctl_join_session_keyring"); key = add_key("user", "a", "b", 1, keyring); OSERROR(key, "add_key"); ret = keyctl(KEYCTL_SESSION_TO_PARENT); OSERROR(ret, "KEYCTL_SESSION_TO_PARENT"); return 0; } Compiled and linked with -lkeyutils, you should see something like: [dhowells@andromeda ~]$ keyctl show Session Keyring -3 --alswrv 4043 4043 keyring: _ses 355907932 --alswrv 4043 -1 \_ keyring: _uid.4043 [dhowells@andromeda ~]$ /tmp/newpag [dhowells@andromeda ~]$ keyctl show Session Keyring -3 --alswrv 4043 4043 keyring: _ses 1055658746 --alswrv 4043 4043 \_ user: a [dhowells@andromeda ~]$ /tmp/newpag hello [dhowells@andromeda ~]$ keyctl show Session Keyring -3 --alswrv 4043 4043 keyring: hello 340417692 --alswrv 4043 4043 \_ user: a Where the test program creates a new session keyring, sticks a user key named 'a' into it and then installs it on its parent. Signed-off-by: David Howells Signed-off-by: James Morris --- security/keys/gc.c | 1 + 1 file changed, 1 insertion(+) (limited to 'security/keys/gc.c') diff --git a/security/keys/gc.c b/security/keys/gc.c index 44adc32..1e616ae 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -65,6 +65,7 @@ static void key_gc_timer_func(unsigned long data) * - return true if we altered the keyring */ static bool key_gc_keyring(struct key *keyring, time_t limit) + __releases(key_serial_lock) { struct keyring_list *klist; struct key *key; -- cgit v1.1