KEYS: Alter use of key instantiation link-to-keyring argument
Alter the use of the key instantiation and negation functions' link-to-keyring
arguments. Currently this specifies a keyring in the target process to link
the key into, creating the keyring if it doesn't exist. This, however, can be
a problem for copy-on-write credentials as it means that the instantiating
process can alter the credentials of the requesting process.
This patch alters the behaviour such that:
(1) If keyctl_instantiate_key() or keyctl_negate_key() are given a specific
keyring by ID (ringid >= 0), then that keyring will be used.
(2) If keyctl_instantiate_key() or keyctl_negate_key() are given one of the
special constants that refer to the requesting process's keyrings
(KEY_SPEC_*_KEYRING, all <= 0), then:
(a) If sys_request_key() was given a keyring to use (destringid) then the
key will be attached to that keyring.
(b) If sys_request_key() was given a NULL keyring, then the key being
instantiated will be attached to the default keyring as set by
keyctl_set_reqkey_keyring().
(3) No extra link will be made.
Decision point (1) follows current behaviour, and allows those instantiators
who've searched for a specifically named keyring in the requestor's keyring so
as to partition the keys by type to still have their named keyrings.
Decision point (2) allows the requestor to make sure that the key or keys that
get produced by request_key() go where they want, whilst allowing the
instantiator to request that the key is retained. This is mainly useful for
situations where the instantiator makes a secondary request, the key for which
should be retained by the initial requestor:
+-----------+ +--------------+ +--------------+
| | | | | |
| Requestor |------->| Instantiator |------->| Instantiator |
| | | | | |
+-----------+ +--------------+ +--------------+
request_key() request_key()
This might be useful, for example, in Kerberos, where the requestor requests a
ticket, and then the ticket instantiator requests the TGT, which someone else
then has to go and fetch. The TGT, however, should be retained in the
keyrings of the requestor, not the first instantiator. To make this explict
an extra special keyring constant is also added.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 3f09e5b..fcce331 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -103,7 +103,7 @@
}
/* find the target keyring (which must be writable) */
- keyring_ref = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
+ keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error3;
@@ -185,7 +185,7 @@
/* get the destination keyring if specified */
dest_ref = NULL;
if (destringid) {
- dest_ref = lookup_user_key(NULL, destringid, 1, 0, KEY_WRITE);
+ dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
if (IS_ERR(dest_ref)) {
ret = PTR_ERR(dest_ref);
goto error3;
@@ -235,7 +235,7 @@
key_ref_t key_ref;
long ret;
- key_ref = lookup_user_key(NULL, id, create, 0, KEY_SEARCH);
+ key_ref = lookup_user_key(id, create, 0, KEY_SEARCH);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -308,7 +308,7 @@
}
/* find the target key (which must be writable) */
- key_ref = lookup_user_key(NULL, id, 0, 0, KEY_WRITE);
+ key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error2;
@@ -336,7 +336,7 @@
key_ref_t key_ref;
long ret;
- key_ref = lookup_user_key(NULL, id, 0, 0, KEY_WRITE);
+ key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -362,7 +362,7 @@
key_ref_t keyring_ref;
long ret;
- keyring_ref = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
+ keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error;
@@ -388,13 +388,13 @@
key_ref_t keyring_ref, key_ref;
long ret;
- keyring_ref = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
+ keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error;
}
- key_ref = lookup_user_key(NULL, id, 1, 0, KEY_LINK);
+ key_ref = lookup_user_key(id, 1, 0, KEY_LINK);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error2;
@@ -422,13 +422,13 @@
key_ref_t keyring_ref, key_ref;
long ret;
- keyring_ref = lookup_user_key(NULL, ringid, 0, 0, KEY_WRITE);
+ keyring_ref = lookup_user_key(ringid, 0, 0, KEY_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error;
}
- key_ref = lookup_user_key(NULL, id, 0, 0, 0);
+ key_ref = lookup_user_key(id, 0, 0, 0);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error2;
@@ -464,7 +464,7 @@
char *tmpbuf;
long ret;
- key_ref = lookup_user_key(NULL, keyid, 0, 1, KEY_VIEW);
+ key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
if (IS_ERR(key_ref)) {
/* viewing a key under construction is permitted if we have the
* authorisation token handy */
@@ -472,7 +472,7 @@
instkey = key_get_instantiation_authkey(keyid);
if (!IS_ERR(instkey)) {
key_put(instkey);
- key_ref = lookup_user_key(NULL, keyid,
+ key_ref = lookup_user_key(keyid,
0, 1, 0);
if (!IS_ERR(key_ref))
goto okay;
@@ -557,7 +557,7 @@
}
/* get the keyring at which to begin the search */
- keyring_ref = lookup_user_key(NULL, ringid, 0, 0, KEY_SEARCH);
+ keyring_ref = lookup_user_key(ringid, 0, 0, KEY_SEARCH);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error2;
@@ -566,7 +566,7 @@
/* get the destination keyring if specified */
dest_ref = NULL;
if (destringid) {
- dest_ref = lookup_user_key(NULL, destringid, 1, 0, KEY_WRITE);
+ dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
if (IS_ERR(dest_ref)) {
ret = PTR_ERR(dest_ref);
goto error3;
@@ -636,7 +636,7 @@
long ret;
/* find the key first */
- key_ref = lookup_user_key(NULL, keyid, 0, 0, 0);
+ key_ref = lookup_user_key(keyid, 0, 0, 0);
if (IS_ERR(key_ref)) {
ret = -ENOKEY;
goto error;
@@ -699,7 +699,7 @@
if (uid == (uid_t) -1 && gid == (gid_t) -1)
goto error;
- key_ref = lookup_user_key(NULL, id, 1, 1, KEY_SETATTR);
+ key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -804,7 +804,7 @@
if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
goto error;
- key_ref = lookup_user_key(NULL, id, 1, 1, KEY_SETATTR);
+ key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -829,6 +829,43 @@
} /* end keyctl_setperm_key() */
+/*
+ * get the destination keyring for instantiation
+ */
+static long get_instantiation_keyring(key_serial_t ringid,
+ struct request_key_auth *rka,
+ struct key **_dest_keyring)
+{
+ key_ref_t dkref;
+
+ /* just return a NULL pointer if we weren't asked to make a link */
+ if (ringid == 0) {
+ *_dest_keyring = NULL;
+ return 0;
+ }
+
+ /* if a specific keyring is nominated by ID, then use that */
+ if (ringid > 0) {
+ dkref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+ if (IS_ERR(dkref))
+ return PTR_ERR(dkref);
+ *_dest_keyring = key_ref_to_ptr(dkref);
+ return 0;
+ }
+
+ if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
+ return -EINVAL;
+
+ /* otherwise specify the destination keyring recorded in the
+ * authorisation key (any KEY_SPEC_*_KEYRING) */
+ if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
+ *_dest_keyring = rka->dest_keyring;
+ return 0;
+ }
+
+ return -ENOKEY;
+}
+
/*****************************************************************************/
/*
* instantiate the key with the specified payload, and, if one is given, link
@@ -840,8 +877,7 @@
key_serial_t ringid)
{
struct request_key_auth *rka;
- struct key *instkey;
- key_ref_t keyring_ref;
+ struct key *instkey, *dest_keyring;
void *payload;
long ret;
bool vm = false;
@@ -883,21 +919,15 @@
/* find the destination keyring amongst those belonging to the
* requesting task */
- keyring_ref = NULL;
- if (ringid) {
- keyring_ref = lookup_user_key(rka->context, ringid, 1, 0,
- KEY_WRITE);
- if (IS_ERR(keyring_ref)) {
- ret = PTR_ERR(keyring_ref);
- goto error2;
- }
- }
+ ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
+ if (ret < 0)
+ goto error2;
/* instantiate the key and link it into a keyring */
ret = key_instantiate_and_link(rka->target_key, payload, plen,
- key_ref_to_ptr(keyring_ref), instkey);
+ dest_keyring, instkey);
- key_ref_put(keyring_ref);
+ key_put(dest_keyring);
/* discard the assumed authority if it's just been disabled by
* instantiation of the key */
@@ -924,8 +954,7 @@
long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
{
struct request_key_auth *rka;
- struct key *instkey;
- key_ref_t keyring_ref;
+ struct key *instkey, *dest_keyring;
long ret;
/* the appropriate instantiation authorisation key must have been
@@ -941,20 +970,15 @@
/* find the destination keyring if present (which must also be
* writable) */
- keyring_ref = NULL;
- if (ringid) {
- keyring_ref = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
- if (IS_ERR(keyring_ref)) {
- ret = PTR_ERR(keyring_ref);
- goto error;
- }
- }
+ ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
+ if (ret < 0)
+ goto error;
/* instantiate the key and link it into a keyring */
ret = key_negate_and_link(rka->target_key, timeout,
- key_ref_to_ptr(keyring_ref), instkey);
+ dest_keyring, instkey);
- key_ref_put(keyring_ref);
+ key_put(dest_keyring);
/* discard the assumed authority if it's just been disabled by
* instantiation of the key */
@@ -979,13 +1003,13 @@
switch (reqkey_defl) {
case KEY_REQKEY_DEFL_THREAD_KEYRING:
- ret = install_thread_keyring(current);
+ ret = install_thread_keyring();
if (ret < 0)
return ret;
goto set;
case KEY_REQKEY_DEFL_PROCESS_KEYRING:
- ret = install_process_keyring(current);
+ ret = install_process_keyring();
if (ret < 0)
return ret;
@@ -1018,7 +1042,7 @@
time_t expiry;
long ret;
- key_ref = lookup_user_key(NULL, id, 1, 1, KEY_SETATTR);
+ key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
@@ -1105,7 +1129,7 @@
char *context;
long ret;
- key_ref = lookup_user_key(NULL, keyid, 0, 1, KEY_VIEW);
+ key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
if (IS_ERR(key_ref)) {
if (PTR_ERR(key_ref) != -EACCES)
return PTR_ERR(key_ref);
@@ -1117,7 +1141,7 @@
return PTR_ERR(key_ref);
key_put(instkey);
- key_ref = lookup_user_key(NULL, keyid, 0, 1, 0);
+ key_ref = lookup_user_key(keyid, 0, 1, 0);
if (IS_ERR(key_ref))
return PTR_ERR(key_ref);
}