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linux/security/keys/internal.h
David Howells 0b0a84154e KEYS: request_key() should reget expired keys rather than give EKEYEXPIRED 
Since the keyring facility can be viewed as a cache (at least in some
applications), the local expiration time on the key should probably be viewed
as a 'needs updating after this time' property rather than an absolute 'anyone
now wanting to use this object is out of luck' property.

Since request_key() is the main interface for the usage of keys, this should
update or replace an expired key rather than issuing EKEYEXPIRED if the local
expiration has been reached (ie. it should refresh the cache).

For absolute conditions where refreshing the cache probably doesn't help, the
key can be negatively instantiated using KEYCTL_REJECT_KEY with EKEYEXPIRED
given as the error to issue.  This will still cause request_key() to return
EKEYEXPIRED as that was explicitly set.

In the future, if the key type has an update op available, we might want to
upcall with the expired key and allow the upcall to update it.  We would pass
a different operation name (the first column in /etc/request-key.conf) to the
request-key program.

request_key() returning EKEYEXPIRED is causing an NFS problem which Chuck
Lever describes thusly:

	After about 10 minutes, my NFSv4 functional tests fail because the
	ownership of the test files goes to "-2". Looking at /proc/keys
	shows that the id_resolv keys that map to my test user ID have
	expired. The ownership problem persists until the expired keys are
	purged from the keyring, and fresh keys are obtained.

	I bisected the problem to 3.13 commit b2a4df200d ("KEYS: Expand
	the capacity of a keyring"). This commit inadvertantly changes the
	API contract of the internal function keyring_search_aux().

	The root cause appears to be that b2a4df200d made "no state check"
	the default behavior. "No state check" means the keyring search
	iterator function skips checking the key's expiry timeout, and
	returns expired keys.  request_key_and_link() depends on getting
	an -EAGAIN result code to know when to perform an upcall to refresh
	an expired key.

This patch can be tested directly by:

	keyctl request2 user debug:fred a @s
	keyctl timeout %user:debug:fred 3
	sleep 4
	keyctl request2 user debug:fred a @s

Without the patch, the last command gives error EKEYEXPIRED, but with the
command it gives a new key.

Reported-by: Carl Hetherington <cth@carlh.net>
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
2014-12-01 22:52:53 +00:00

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/* Authentication token and access key management internal defs
*
* Copyright (C) 2003-5, 2007 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.
*/
#ifndef _INTERNAL_H
#define _INTERNAL_H
#include <linux/sched.h>
#include <linux/key-type.h>
#include <linux/task_work.h>
struct iovec;
#ifdef __KDEBUG
#define kenter(FMT, ...) \
printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__)
#define kleave(FMT, ...) \
printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
#define kdebug(FMT, ...) \
printk(KERN_DEBUG " "FMT"\n", ##__VA_ARGS__)
#else
#define kenter(FMT, ...) \
no_printk(KERN_DEBUG "==> %s("FMT")\n", __func__, ##__VA_ARGS__)
#define kleave(FMT, ...) \
no_printk(KERN_DEBUG "<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
#define kdebug(FMT, ...) \
no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__)
#endif
extern struct key_type key_type_dead;
extern struct key_type key_type_user;
extern struct key_type key_type_logon;
/*****************************************************************************/
/*
* Keep track of keys for a user.
*
* This needs to be separate to user_struct to avoid a refcount-loop
* (user_struct pins some keyrings which pin this struct).
*
* We also keep track of keys under request from userspace for this UID here.
*/
struct key_user {
struct rb_node node;
struct mutex cons_lock; /* construction initiation lock */
spinlock_t lock;
atomic_t usage; /* for accessing qnkeys & qnbytes */
atomic_t nkeys; /* number of keys */
atomic_t nikeys; /* number of instantiated keys */
kuid_t uid;
int qnkeys; /* number of keys allocated to this user */
int qnbytes; /* number of bytes allocated to this user */
};
extern struct rb_root key_user_tree;
extern spinlock_t key_user_lock;
extern struct key_user root_key_user;
extern struct key_user *key_user_lookup(kuid_t uid);
extern void key_user_put(struct key_user *user);
/*
* Key quota limits.
* - root has its own separate limits to everyone else
*/
extern unsigned key_quota_root_maxkeys;
extern unsigned key_quota_root_maxbytes;
extern unsigned key_quota_maxkeys;
extern unsigned key_quota_maxbytes;
#define KEYQUOTA_LINK_BYTES 4 /* a link in a keyring is worth 4 bytes */
extern struct kmem_cache *key_jar;
extern struct rb_root key_serial_tree;
extern spinlock_t key_serial_lock;
extern struct mutex key_construction_mutex;
extern wait_queue_head_t request_key_conswq;
extern struct key_type *key_type_lookup(const char *type);
extern void key_type_put(struct key_type *ktype);
extern int __key_link_begin(struct key *keyring,
const struct keyring_index_key *index_key,
struct assoc_array_edit **_edit);
extern int __key_link_check_live_key(struct key *keyring, struct key *key);
extern void __key_link(struct key *key, struct assoc_array_edit **_edit);
extern void __key_link_end(struct key *keyring,
const struct keyring_index_key *index_key,
struct assoc_array_edit *edit);
extern key_ref_t find_key_to_update(key_ref_t keyring_ref,
const struct keyring_index_key *index_key);
extern struct key *keyring_search_instkey(struct key *keyring,
key_serial_t target_id);
extern int iterate_over_keyring(const struct key *keyring,
int (*func)(const struct key *key, void *data),
void *data);
struct keyring_search_context {
struct keyring_index_key index_key;
const struct cred *cred;
struct key_match_data match_data;
unsigned flags;
#define KEYRING_SEARCH_NO_STATE_CHECK 0x0001 /* Skip state checks */
#define KEYRING_SEARCH_DO_STATE_CHECK 0x0002 /* Override NO_STATE_CHECK */
#define KEYRING_SEARCH_NO_UPDATE_TIME 0x0004 /* Don't update times */
#define KEYRING_SEARCH_NO_CHECK_PERM 0x0008 /* Don't check permissions */
#define KEYRING_SEARCH_DETECT_TOO_DEEP 0x0010 /* Give an error on excessive depth */
#define KEYRING_SEARCH_SKIP_EXPIRED 0x0020 /* Ignore expired keys (intention to replace) */
int (*iterator)(const void *object, void *iterator_data);
/* Internal stuff */
int skipped_ret;
bool possessed;
key_ref_t result;
struct timespec now;
};
extern bool key_default_cmp(const struct key *key,
const struct key_match_data *match_data);
extern key_ref_t keyring_search_aux(key_ref_t keyring_ref,
struct keyring_search_context *ctx);
extern key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx);
extern key_ref_t search_process_keyrings(struct keyring_search_context *ctx);
extern struct key *find_keyring_by_name(const char *name, bool skip_perm_check);
extern int install_user_keyrings(void);
extern int install_thread_keyring_to_cred(struct cred *);
extern int install_process_keyring_to_cred(struct cred *);
extern int install_session_keyring_to_cred(struct cred *, struct key *);
extern struct key *request_key_and_link(struct key_type *type,
const char *description,
const void *callout_info,
size_t callout_len,
void *aux,
struct key *dest_keyring,
unsigned long flags);
extern bool lookup_user_key_possessed(const struct key *key,
const struct key_match_data *match_data);
extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
key_perm_t perm);
#define KEY_LOOKUP_CREATE 0x01
#define KEY_LOOKUP_PARTIAL 0x02
#define KEY_LOOKUP_FOR_UNLINK 0x04
extern long join_session_keyring(const char *name);
extern void key_change_session_keyring(struct callback_head *twork);
extern struct work_struct key_gc_work;
extern unsigned key_gc_delay;
extern void keyring_gc(struct key *keyring, time_t limit);
extern void key_schedule_gc(time_t gc_at);
extern void key_schedule_gc_links(void);
extern void key_gc_keytype(struct key_type *ktype);
extern int key_task_permission(const key_ref_t key_ref,
const struct cred *cred,
key_perm_t perm);
/*
* Check to see whether permission is granted to use a key in the desired way.
*/
static inline int key_permission(const key_ref_t key_ref, unsigned perm)
{
return key_task_permission(key_ref, current_cred(), perm);
}
/*
* Authorisation record for request_key().
*/
struct request_key_auth {
struct key *target_key;
struct key *dest_keyring;
const struct cred *cred;
void *callout_info;
size_t callout_len;
pid_t pid;
};
extern struct key_type key_type_request_key_auth;
extern struct key *request_key_auth_new(struct key *target,
const void *callout_info,
size_t callout_len,
struct key *dest_keyring);
extern struct key *key_get_instantiation_authkey(key_serial_t target_id);
/*
* Determine whether a key is dead.
*/
static inline bool key_is_dead(const struct key *key, time_t limit)
{
return
key->flags & ((1 << KEY_FLAG_DEAD) |
(1 << KEY_FLAG_INVALIDATED)) ||
(key->expiry > 0 && key->expiry <= limit);
}
/*
* keyctl() functions
*/
extern long keyctl_get_keyring_ID(key_serial_t, int);
extern long keyctl_join_session_keyring(const char __user *);
extern long keyctl_update_key(key_serial_t, const void __user *, size_t);
extern long keyctl_revoke_key(key_serial_t);
extern long keyctl_keyring_clear(key_serial_t);
extern long keyctl_keyring_link(key_serial_t, key_serial_t);
extern long keyctl_keyring_unlink(key_serial_t, key_serial_t);
extern long keyctl_describe_key(key_serial_t, char __user *, size_t);
extern long keyctl_keyring_search(key_serial_t, const char __user *,
const char __user *, key_serial_t);
extern long keyctl_read_key(key_serial_t, char __user *, size_t);
extern long keyctl_chown_key(key_serial_t, uid_t, gid_t);
extern long keyctl_setperm_key(key_serial_t, key_perm_t);
extern long keyctl_instantiate_key(key_serial_t, const void __user *,
size_t, key_serial_t);
extern long keyctl_negate_key(key_serial_t, unsigned, key_serial_t);
extern long keyctl_set_reqkey_keyring(int);
extern long keyctl_set_timeout(key_serial_t, unsigned);
extern long keyctl_assume_authority(key_serial_t);
extern long keyctl_get_security(key_serial_t keyid, char __user *buffer,
size_t buflen);
extern long keyctl_session_to_parent(void);
extern long keyctl_reject_key(key_serial_t, unsigned, unsigned, key_serial_t);
extern long keyctl_instantiate_key_iov(key_serial_t,
const struct iovec __user *,
unsigned, key_serial_t);
extern long keyctl_invalidate_key(key_serial_t);
extern long keyctl_instantiate_key_common(key_serial_t,
const struct iovec *,
unsigned, size_t, key_serial_t);
#ifdef CONFIG_PERSISTENT_KEYRINGS
extern long keyctl_get_persistent(uid_t, key_serial_t);
extern unsigned persistent_keyring_expiry;
#else
static inline long keyctl_get_persistent(uid_t uid, key_serial_t destring)
{
return -EOPNOTSUPP;
}
#endif
/*
* Debugging key validation
*/
#ifdef KEY_DEBUGGING
extern void __key_check(const struct key *);
static inline void key_check(const struct key *key)
{
if (key && (IS_ERR(key) || key->magic != KEY_DEBUG_MAGIC))
__key_check(key);
}
#else
#define key_check(key) do {} while(0)
#endif
#endif /* _INTERNAL_H */
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