3e30148c3d
The attached patch makes the following changes:
(1) There's a new special key type called ".request_key_auth".
This is an authorisation key for when one process requests a key and
another process is started to construct it. This type of key cannot be
created by the user; nor can it be requested by kernel services.
Authorisation keys hold two references:
(a) Each refers to a key being constructed. When the key being
constructed is instantiated the authorisation key is revoked,
rendering it of no further use.
(b) The "authorising process". This is either:
(i) the process that called request_key(), or:
(ii) if the process that called request_key() itself had an
authorisation key in its session keyring, then the authorising
process referred to by that authorisation key will also be
referred to by the new authorisation key.
This means that the process that initiated a chain of key requests
will authorise the lot of them, and will, by default, wind up with
the keys obtained from them in its keyrings.
(2) request_key() creates an authorisation key which is then passed to
/sbin/request-key in as part of a new session keyring.
(3) When request_key() is searching for a key to hand back to the caller, if
it comes across an authorisation key in the session keyring of the
calling process, it will also search the keyrings of the process
specified therein and it will use the specified process's credentials
(fsuid, fsgid, groups) to do that rather than the calling process's
credentials.
This allows a process started by /sbin/request-key to find keys belonging
to the authorising process.
(4) A key can be read, even if the process executing KEYCTL_READ doesn't have
direct read or search permission if that key is contained within the
keyrings of a process specified by an authorisation key found within the
calling process's session keyring, and is searchable using the
credentials of the authorising process.
This allows a process started by /sbin/request-key to read keys belonging
to the authorising process.
(5) The magic KEY_SPEC_*_KEYRING key IDs when passed to KEYCTL_INSTANTIATE or
KEYCTL_NEGATE will specify a keyring of the authorising process, rather
than the process doing the instantiation.
(6) One of the process keyrings can be nominated as the default to which
request_key() should attach new keys if not otherwise specified. This is
done with KEYCTL_SET_REQKEY_KEYRING and one of the KEY_REQKEY_DEFL_*
constants. The current setting can also be read using this call.
(7) request_key() is partially interruptible. If it is waiting for another
process to finish constructing a key, it can be interrupted. This permits
a request-key cycle to be broken without recourse to rebooting.
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-Off-By: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
136 lines
3.3 KiB
C
136 lines
3.3 KiB
C
/* key-ui.h: key userspace interface stuff
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#ifndef _LINUX_KEY_UI_H
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#define _LINUX_KEY_UI_H
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#include <linux/key.h>
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/* the key tree */
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extern struct rb_root key_serial_tree;
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extern spinlock_t key_serial_lock;
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/* required permissions */
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#define KEY_VIEW 0x01 /* require permission to view attributes */
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#define KEY_READ 0x02 /* require permission to read content */
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#define KEY_WRITE 0x04 /* require permission to update / modify */
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#define KEY_SEARCH 0x08 /* require permission to search (keyring) or find (key) */
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#define KEY_LINK 0x10 /* require permission to link */
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#define KEY_ALL 0x1f /* all the above permissions */
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/*
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* the keyring payload contains a list of the keys to which the keyring is
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* subscribed
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*/
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struct keyring_list {
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struct rcu_head rcu; /* RCU deletion hook */
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unsigned short maxkeys; /* max keys this list can hold */
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unsigned short nkeys; /* number of keys currently held */
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unsigned short delkey; /* key to be unlinked by RCU */
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struct key *keys[0];
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};
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/*
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* check to see whether permission is granted to use a key in the desired way
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*/
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static inline int key_permission(const struct key *key, key_perm_t perm)
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{
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key_perm_t kperm;
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if (key->uid == current->fsuid)
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kperm = key->perm >> 16;
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else if (key->gid != -1 &&
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key->perm & KEY_GRP_ALL &&
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in_group_p(key->gid)
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)
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kperm = key->perm >> 8;
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else
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kperm = key->perm;
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kperm = kperm & perm & KEY_ALL;
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return kperm == perm;
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}
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/*
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* check to see whether permission is granted to use a key in at least one of
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* the desired ways
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*/
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static inline int key_any_permission(const struct key *key, key_perm_t perm)
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{
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key_perm_t kperm;
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if (key->uid == current->fsuid)
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kperm = key->perm >> 16;
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else if (key->gid != -1 &&
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key->perm & KEY_GRP_ALL &&
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in_group_p(key->gid)
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)
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kperm = key->perm >> 8;
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else
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kperm = key->perm;
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kperm = kperm & perm & KEY_ALL;
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return kperm != 0;
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}
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static inline int key_task_groups_search(struct task_struct *tsk, gid_t gid)
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{
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int ret;
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task_lock(tsk);
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ret = groups_search(tsk->group_info, gid);
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task_unlock(tsk);
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return ret;
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}
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static inline int key_task_permission(const struct key *key,
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struct task_struct *context,
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key_perm_t perm)
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{
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key_perm_t kperm;
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if (key->uid == context->fsuid) {
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kperm = key->perm >> 16;
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}
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else if (key->gid != -1 &&
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key->perm & KEY_GRP_ALL && (
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key->gid == context->fsgid ||
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key_task_groups_search(context, key->gid)
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)
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) {
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kperm = key->perm >> 8;
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}
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else {
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kperm = key->perm;
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}
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kperm = kperm & perm & KEY_ALL;
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return kperm == perm;
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}
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extern struct key *lookup_user_key(struct task_struct *context,
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key_serial_t id, int create, int partial,
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key_perm_t perm);
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extern long join_session_keyring(const char *name);
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extern struct key_type *key_type_lookup(const char *type);
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extern void key_type_put(struct key_type *ktype);
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#define key_negative_timeout 60 /* default timeout on a negative key's existence */
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#endif /* _LINUX_KEY_UI_H */
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