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linux/security/keys/internal.h
David Howells ee18d64c1f 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 <stdio.h>
	#include <stdlib.h>
	#include <keyutils.h>

	#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 <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-09-02 21:29:22 +10:00

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/* internal.h: 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>
static inline __attribute__((format(printf, 1, 2)))
void no_printk(const char *fmt, ...)
{
}
#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_user;
/*****************************************************************************/
/*
* 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)
* - this also keeps track of keys under request from userspace for this UID
*/
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 */
uid_t uid;
struct user_namespace *user_ns;
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(uid_t uid,
struct user_namespace *user_ns);
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 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(struct key *keyring, struct key *key);
extern key_ref_t __keyring_search_one(key_ref_t keyring_ref,
const struct key_type *type,
const char *description,
key_perm_t perm);
extern struct key *keyring_search_instkey(struct key *keyring,
key_serial_t target_id);
typedef int (*key_match_func_t)(const struct key *, const void *);
extern key_ref_t keyring_search_aux(key_ref_t keyring_ref,
const struct cred *cred,
struct key_type *type,
const void *description,
key_match_func_t match);
extern key_ref_t search_process_keyrings(struct key_type *type,
const void *description,
key_match_func_t match,
const struct cred *cred);
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 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 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 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
*/
extern int key_task_permission(const key_ref_t key_ref,
const struct cred *cred,
key_perm_t perm);
static inline int key_permission(const key_ref_t key_ref, key_perm_t perm)
{
return key_task_permission(key_ref, current_cred(), perm);
}
/* required permissions */
#define KEY_VIEW 0x01 /* require permission to view attributes */
#define KEY_READ 0x02 /* require permission to read content */
#define KEY_WRITE 0x04 /* require permission to update / modify */
#define KEY_SEARCH 0x08 /* require permission to search (keyring) or find (key) */
#define KEY_LINK 0x10 /* require permission to link */
#define KEY_SETATTR 0x20 /* require permission to change attributes */
#define KEY_ALL 0x3f /* all the above permissions */
/*
* request_key authorisation
*/
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);
/*
* 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);
/*
* 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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