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2e12256b9a
linux-brain/security/keys/internal.h
David Howells 2e12256b9a keys: Replace uid/gid/perm permissions checking with an ACL 
Replace the uid/gid/perm permissions checking on a key with an ACL to allow
the SETATTR and SEARCH permissions to be split.  This will also allow a
greater range of subjects to represented.

============
WHY DO THIS?
============

The problem is that SETATTR and SEARCH cover a slew of actions, not all of
which should be grouped together.

For SETATTR, this includes actions that are about controlling access to a
key:

 (1) Changing a key's ownership.

 (2) Changing a key's security information.

 (3) Setting a keyring's restriction.

And actions that are about managing a key's lifetime:

 (4) Setting an expiry time.

 (5) Revoking a key.

and (proposed) managing a key as part of a cache:

 (6) Invalidating a key.

Managing a key's lifetime doesn't really have anything to do with
controlling access to that key.

Expiry time is awkward since it's more about the lifetime of the content
and so, in some ways goes better with WRITE permission.  It can, however,
be set unconditionally by a process with an appropriate authorisation token
for instantiating a key, and can also be set by the key type driver when a
key is instantiated, so lumping it with the access-controlling actions is
probably okay.

As for SEARCH permission, that currently covers:

 (1) Finding keys in a keyring tree during a search.

 (2) Permitting keyrings to be joined.

 (3) Invalidation.

But these don't really belong together either, since these actions really
need to be controlled separately.

Finally, there are number of special cases to do with granting the
administrator special rights to invalidate or clear keys that I would like
to handle with the ACL rather than key flags and special checks.


===============
WHAT IS CHANGED
===============

The SETATTR permission is split to create two new permissions:

 (1) SET_SECURITY - which allows the key's owner, group and ACL to be
     changed and a restriction to be placed on a keyring.

 (2) REVOKE - which allows a key to be revoked.

The SEARCH permission is split to create:

 (1) SEARCH - which allows a keyring to be search and a key to be found.

 (2) JOIN - which allows a keyring to be joined as a session keyring.

 (3) INVAL - which allows a key to be invalidated.

The WRITE permission is also split to create:

 (1) WRITE - which allows a key's content to be altered and links to be
     added, removed and replaced in a keyring.

 (2) CLEAR - which allows a keyring to be cleared completely.  This is
     split out to make it possible to give just this to an administrator.

 (3) REVOKE - see above.


Keys acquire ACLs which consist of a series of ACEs, and all that apply are
unioned together.  An ACE specifies a subject, such as:

 (*) Possessor - permitted to anyone who 'possesses' a key
 (*) Owner - permitted to the key owner
 (*) Group - permitted to the key group
 (*) Everyone - permitted to everyone

Note that 'Other' has been replaced with 'Everyone' on the assumption that
you wouldn't grant a permit to 'Other' that you wouldn't also grant to
everyone else.

Further subjects may be made available by later patches.

The ACE also specifies a permissions mask.  The set of permissions is now:

	VIEW		Can view the key metadata
	READ		Can read the key content
	WRITE		Can update/modify the key content
	SEARCH		Can find the key by searching/requesting
	LINK		Can make a link to the key
	SET_SECURITY	Can change owner, ACL, expiry
	INVAL		Can invalidate
	REVOKE		Can revoke
	JOIN		Can join this keyring
	CLEAR		Can clear this keyring


The KEYCTL_SETPERM function is then deprecated.

The KEYCTL_SET_TIMEOUT function then is permitted if SET_SECURITY is set,
or if the caller has a valid instantiation auth token.

The KEYCTL_INVALIDATE function then requires INVAL.

The KEYCTL_REVOKE function then requires REVOKE.

The KEYCTL_JOIN_SESSION_KEYRING function then requires JOIN to join an
existing keyring.

The JOIN permission is enabled by default for session keyrings and manually
created keyrings only.


======================
BACKWARD COMPATIBILITY
======================

To maintain backward compatibility, KEYCTL_SETPERM will translate the
permissions mask it is given into a new ACL for a key - unless
KEYCTL_SET_ACL has been called on that key, in which case an error will be
returned.

It will convert possessor, owner, group and other permissions into separate
ACEs, if each portion of the mask is non-zero.

SETATTR permission turns on all of INVAL, REVOKE and SET_SECURITY.  WRITE
permission turns on WRITE, REVOKE and, if a keyring, CLEAR.  JOIN is turned
on if a keyring is being altered.

The KEYCTL_DESCRIBE function translates the ACL back into a permissions
mask to return depending on possessor, owner, group and everyone ACEs.

It will make the following mappings:

 (1) INVAL, JOIN -> SEARCH

 (2) SET_SECURITY -> SETATTR

 (3) REVOKE -> WRITE if SETATTR isn't already set

 (4) CLEAR -> WRITE

Note that the value subsequently returned by KEYCTL_DESCRIBE may not match
the value set with KEYCTL_SETATTR.


=======
TESTING
=======

This passes the keyutils testsuite for all but a couple of tests:

 (1) tests/keyctl/dh_compute/badargs: The first wrong-key-type test now
     returns EOPNOTSUPP rather than ENOKEY as READ permission isn't removed
     if the type doesn't have ->read().  You still can't actually read the
     key.

 (2) tests/keyctl/permitting/valid: The view-other-permissions test doesn't
     work as Other has been replaced with Everyone in the ACL.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-06-27 23:03:07 +01:00

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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/wait_bit.h>
#include <linux/cred.h>
#include <linux/key-type.h>
#include <linux/task_work.h>
#include <linux/keyctl.h>
#include <linux/refcount.h>
#include <linux/compat.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;
refcount_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_acl default_key_acl;
extern struct key_acl joinable_keyring_acl;
extern void key_set_index_key(struct keyring_index_key *index_key);
extern struct key_type *key_type_lookup(const char *type);
extern void key_type_put(struct key_type *ktype);
extern int __key_link_lock(struct key *keyring,
const struct keyring_index_key *index_key);
extern int __key_move_lock(struct key *l_keyring, struct key *u_keyring,
const struct keyring_index_key *index_key);
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) */
#define KEYRING_SEARCH_RECURSE 0x0040 /* Search child keyrings also */
int (*iterator)(const void *object, void *iterator_data);
/* Internal stuff */
int skipped_ret;
bool possessed;
key_ref_t result;
time64_t now;
};
extern bool key_default_cmp(const struct key *key,
const struct key_match_data *match_data);
extern key_ref_t keyring_search_rcu(key_ref_t keyring_ref,
struct keyring_search_context *ctx);
extern key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx);
extern key_ref_t search_process_keyrings_rcu(struct keyring_search_context *ctx);
extern struct key *find_keyring_by_name(const char *name, bool uid_keyring);
extern int look_up_user_keyrings(struct key **, struct key **);
extern struct key *get_user_session_keyring_rcu(const struct cred *);
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,
struct key_tag *domain_tag,
const void *callout_info,
size_t callout_len,
void *aux,
struct key_acl *acl,
struct key *dest_keyring,
unsigned long flags);
extern bool lookup_user_key_possessed(const struct key *key,
const struct key_match_data *match_data);
#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, time64_t limit);
extern void keyring_restriction_gc(struct key *keyring,
struct key_type *dead_type);
extern void key_schedule_gc(time64_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,
u32 desired_perm);
extern unsigned int key_acl_to_perm(const struct key_acl *acl);
extern long key_set_acl(struct key *key, struct key_acl *acl);
extern void key_put_acl(struct key_acl *acl);
/*
* 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);
}
extern struct key_type key_type_request_key_auth;
extern struct key *request_key_auth_new(struct key *target,
const char *op,
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, time64_t limit)
{
return
key->flags & ((1 << KEY_FLAG_DEAD) |
(1 << KEY_FLAG_INVALIDATED)) ||
(key->expiry > 0 && key->expiry <= limit) ||
key->domain_tag->removed;
}
/*
* 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_move(key_serial_t, key_serial_t, key_serial_t, unsigned int);
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, unsigned int);
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);
struct iov_iter;
extern long keyctl_instantiate_key_common(key_serial_t,
struct iov_iter *,
key_serial_t);
extern long keyctl_restrict_keyring(key_serial_t id,
const char __user *_type,
const char __user *_restriction);
#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
#ifdef CONFIG_KEY_DH_OPERATIONS
extern long keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
size_t, struct keyctl_kdf_params __user *);
extern long __keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
size_t, struct keyctl_kdf_params *);
#ifdef CONFIG_KEYS_COMPAT
extern long compat_keyctl_dh_compute(struct keyctl_dh_params __user *params,
char __user *buffer, size_t buflen,
struct compat_keyctl_kdf_params __user *kdf);
#endif
#define KEYCTL_KDF_MAX_OUTPUT_LEN 1024 /* max length of KDF output */
#define KEYCTL_KDF_MAX_OI_LEN 64 /* max length of otherinfo */
#else
static inline long keyctl_dh_compute(struct keyctl_dh_params __user *params,
char __user *buffer, size_t buflen,
struct keyctl_kdf_params __user *kdf)
{
return -EOPNOTSUPP;
}
#ifdef CONFIG_KEYS_COMPAT
static inline long compat_keyctl_dh_compute(
struct keyctl_dh_params __user *params,
char __user *buffer, size_t buflen,
struct keyctl_kdf_params __user *kdf)
{
return -EOPNOTSUPP;
}
#endif
#endif
#ifdef CONFIG_ASYMMETRIC_KEY_TYPE
extern long keyctl_pkey_query(key_serial_t,
const char __user *,
struct keyctl_pkey_query __user *);
extern long keyctl_pkey_verify(const struct keyctl_pkey_params __user *,
const char __user *,
const void __user *, const void __user *);
extern long keyctl_pkey_e_d_s(int,
const struct keyctl_pkey_params __user *,
const char __user *,
const void __user *, void __user *);
#else
static inline long keyctl_pkey_query(key_serial_t id,
const char __user *_info,
struct keyctl_pkey_query __user *_res)
{
return -EOPNOTSUPP;
}
static inline long keyctl_pkey_verify(const struct keyctl_pkey_params __user *params,
const char __user *_info,
const void __user *_in,
const void __user *_in2)
{
return -EOPNOTSUPP;
}
static inline long keyctl_pkey_e_d_s(int op,
const struct keyctl_pkey_params __user *params,
const char __user *_info,
const void __user *_in,
void __user *_out)
{
return -EOPNOTSUPP;
}
#endif
extern long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen);
/*
* 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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