Commit ed0ac5c7 authored by David Howells's avatar David Howells

keys: Add a keyctl to move a key between keyrings

Add a keyctl to atomically move a link to a key from one keyring to
another.  The key must exist in "from" keyring and a flag can be given to
cause the operation to fail if there's a matching key already in the "to"
keyring.

This can be done with:

	keyctl(KEYCTL_MOVE,
	       key_serial_t key,
	       key_serial_t from_keyring,
	       key_serial_t to_keyring,
	       unsigned int flags);

The key being moved must grant Link permission and both keyrings must grant
Write permission.

flags should be 0 or KEYCTL_MOVE_EXCL, with the latter preventing
displacement of a matching key from the "to" keyring.
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent df593ee2
......@@ -577,6 +577,27 @@ The keyctl syscall functions are:
added.
* Move a key from one keyring to another::
long keyctl(KEYCTL_MOVE,
key_serial_t id,
key_serial_t from_ring_id,
key_serial_t to_ring_id,
unsigned int flags);
Move the key specified by "id" from the keyring specified by
"from_ring_id" to the keyring specified by "to_ring_id". If the two
keyrings are the same, nothing is done.
"flags" can have KEYCTL_MOVE_EXCL set in it to cause the operation to fail
with EEXIST if a matching key exists in the destination keyring, otherwise
such a key will be replaced.
A process must have link permission on the key for this function to be
successful and write permission on both keyrings. Any errors that can
occur from KEYCTL_LINK also apply on the destination keyring here.
* Unlink a key or keyring from another keyring::
long keyctl(KEYCTL_UNLINK, key_serial_t keyring, key_serial_t key);
......
......@@ -310,6 +310,11 @@ extern int key_update(key_ref_t key,
extern int key_link(struct key *keyring,
struct key *key);
extern int key_move(struct key *key,
struct key *from_keyring,
struct key *to_keyring,
unsigned int flags);
extern int key_unlink(struct key *keyring,
struct key *key);
......
......@@ -67,6 +67,7 @@
#define KEYCTL_PKEY_SIGN 27 /* Create a public key signature */
#define KEYCTL_PKEY_VERIFY 28 /* Verify a public key signature */
#define KEYCTL_RESTRICT_KEYRING 29 /* Restrict keys allowed to link to a keyring */
#define KEYCTL_MOVE 30 /* Move keys between keyrings */
/* keyctl structures */
struct keyctl_dh_params {
......@@ -112,4 +113,6 @@ struct keyctl_pkey_params {
__u32 __spare[7];
};
#define KEYCTL_MOVE_EXCL 0x00000001 /* Do not displace from the to-keyring */
#endif /* _LINUX_KEYCTL_H */
......@@ -159,6 +159,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
return keyctl_pkey_verify(compat_ptr(arg2), compat_ptr(arg3),
compat_ptr(arg4), compat_ptr(arg5));
case KEYCTL_MOVE:
return keyctl_keyring_move(arg2, arg3, arg4, arg5);
default:
return -EOPNOTSUPP;
}
......
......@@ -95,6 +95,8 @@ 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);
......@@ -217,6 +219,7 @@ 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 *,
......
......@@ -572,6 +572,52 @@ long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
return ret;
}
/*
* Move a link to a key from one keyring to another, displacing any matching
* key from the destination keyring.
*
* The key must grant the caller Link permission and both keyrings must grant
* the caller Write permission. There must also be a link in the from keyring
* to the key. If both keyrings are the same, nothing is done.
*
* If successful, 0 will be returned.
*/
long keyctl_keyring_move(key_serial_t id, key_serial_t from_ringid,
key_serial_t to_ringid, unsigned int flags)
{
key_ref_t key_ref, from_ref, to_ref;
long ret;
if (flags & ~KEYCTL_MOVE_EXCL)
return -EINVAL;
key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
if (IS_ERR(key_ref))
return PTR_ERR(key_ref);
from_ref = lookup_user_key(from_ringid, 0, KEY_NEED_WRITE);
if (IS_ERR(from_ref)) {
ret = PTR_ERR(from_ref);
goto error2;
}
to_ref = lookup_user_key(to_ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
if (IS_ERR(to_ref)) {
ret = PTR_ERR(to_ref);
goto error3;
}
ret = key_move(key_ref_to_ptr(key_ref), key_ref_to_ptr(from_ref),
key_ref_to_ptr(to_ref), flags);
key_ref_put(to_ref);
error3:
key_ref_put(from_ref);
error2:
key_ref_put(key_ref);
return ret;
}
/*
* Return a description of a key to userspace.
*
......@@ -1772,6 +1818,12 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
(const void __user *)arg4,
(const void __user *)arg5);
case KEYCTL_MOVE:
return keyctl_keyring_move((key_serial_t)arg2,
(key_serial_t)arg3,
(key_serial_t)arg4,
(unsigned int)arg5);
default:
return -EOPNOTSUPP;
}
......
......@@ -1221,6 +1221,40 @@ int __key_link_lock(struct key *keyring,
return 0;
}
/*
* Lock keyrings for move (link/unlink combination).
*/
int __key_move_lock(struct key *l_keyring, struct key *u_keyring,
const struct keyring_index_key *index_key)
__acquires(&l_keyring->sem)
__acquires(&u_keyring->sem)
__acquires(&keyring_serialise_link_lock)
{
if (l_keyring->type != &key_type_keyring ||
u_keyring->type != &key_type_keyring)
return -ENOTDIR;
/* We have to be very careful here to take the keyring locks in the
* right order, lest we open ourselves to deadlocking against another
* move operation.
*/
if (l_keyring < u_keyring) {
down_write(&l_keyring->sem);
down_write_nested(&u_keyring->sem, 1);
} else {
down_write(&u_keyring->sem);
down_write_nested(&l_keyring->sem, 1);
}
/* Serialise link/link calls to prevent parallel calls causing a cycle
* when linking two keyring in opposite orders.
*/
if (index_key->type == &key_type_keyring)
mutex_lock(&keyring_serialise_link_lock);
return 0;
}
/*
* Preallocate memory so that a key can be linked into to a keyring.
*/
......@@ -1494,6 +1528,80 @@ int key_unlink(struct key *keyring, struct key *key)
}
EXPORT_SYMBOL(key_unlink);
/**
* key_move - Move a key from one keyring to another
* @key: The key to move
* @from_keyring: The keyring to remove the link from.
* @to_keyring: The keyring to make the link in.
* @flags: Qualifying flags, such as KEYCTL_MOVE_EXCL.
*
* Make a link in @to_keyring to a key, such that the keyring holds a reference
* on that key and the key can potentially be found by searching that keyring
* whilst simultaneously removing a link to the key from @from_keyring.
*
* This function will write-lock both keyring's semaphores and will consume
* some of the user's key data quota to hold the link on @to_keyring.
*
* Returns 0 if successful, -ENOTDIR if either keyring isn't a keyring,
* -EKEYREVOKED if either keyring has been revoked, -ENFILE if the second
* keyring is full, -EDQUOT if there is insufficient key data quota remaining
* to add another link or -ENOMEM if there's insufficient memory. If
* KEYCTL_MOVE_EXCL is set, then -EEXIST will be returned if there's already a
* matching key in @to_keyring.
*
* It is assumed that the caller has checked that it is permitted for a link to
* be made (the keyring should have Write permission and the key Link
* permission).
*/
int key_move(struct key *key,
struct key *from_keyring,
struct key *to_keyring,
unsigned int flags)
{
struct assoc_array_edit *from_edit = NULL, *to_edit = NULL;
int ret;
kenter("%d,%d,%d", key->serial, from_keyring->serial, to_keyring->serial);
if (from_keyring == to_keyring)
return 0;
key_check(key);
key_check(from_keyring);
key_check(to_keyring);
ret = __key_move_lock(from_keyring, to_keyring, &key->index_key);
if (ret < 0)
goto out;
ret = __key_unlink_begin(from_keyring, key, &from_edit);
if (ret < 0)
goto error;
ret = __key_link_begin(to_keyring, &key->index_key, &to_edit);
if (ret < 0)
goto error;
ret = -EEXIST;
if (to_edit->dead_leaf && (flags & KEYCTL_MOVE_EXCL))
goto error;
ret = __key_link_check_restriction(to_keyring, key);
if (ret < 0)
goto error;
ret = __key_link_check_live_key(to_keyring, key);
if (ret < 0)
goto error;
__key_unlink(from_keyring, key, &from_edit);
__key_link(key, &to_edit);
error:
__key_link_end(to_keyring, &key->index_key, to_edit);
__key_unlink_end(from_keyring, key, from_edit);
out:
kleave(" = %d", ret);
return ret;
}
EXPORT_SYMBOL(key_move);
/**
* keyring_clear - Clear a keyring
* @keyring: The keyring to clear.
......
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