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| author |   Eric Biggers <ebiggers@google.com> | 2017-09-18 11:37:03 -0700 |
|---|---|---|
| committer |   David Howells <dhowells@redhat.com> | 2017-09-25 15:19:57 +0100 |
| commit | 237bbd29f7a049d310d907f4b2716a7feef9abf3 (patch) | |
| tree | bc95e55675ae062350f77c9f6d8f8d0816b83207 /include/linux/key.h | |
| parent | KEYS: fix writing past end of user-supplied buffer in keyring_read() (diff) | |
| download | linux-dev-237bbd29f7a049d310d907f4b2716a7feef9abf3.tar.xz linux-dev-237bbd29f7a049d310d907f4b2716a7feef9abf3.zip | |
KEYS: prevent creating a different user's keyrings
It was possible for an unprivileged user to create the user and user
session keyrings for another user. For example:
sudo -u '#3000' sh -c 'keyctl add keyring _uid.4000 "" @u
keyctl add keyring _uid_ses.4000 "" @u
sleep 15' &
sleep 1
sudo -u '#4000' keyctl describe @u
sudo -u '#4000' keyctl describe @us
This is problematic because these "fake" keyrings won't have the right
permissions. In particular, the user who created them first will own
them and will have full access to them via the possessor permissions,
which can be used to compromise the security of a user's keys:
-4: alswrv-----v------------ 3000 0 keyring: _uid.4000
-5: alswrv-----v------------ 3000 0 keyring: _uid_ses.4000
Fix it by marking user and user session keyrings with a flag
KEY_FLAG_UID_KEYRING. Then, when searching for a user or user session
keyring by name, skip all keyrings that don't have the flag set.
Fixes: 69664cf16af4 ("keys: don't generate user and user session keyrings unless they're accessed")
Cc: <stable@vger.kernel.org> [v2.6.26+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to '')
| -rw-r--r-- | include/linux/key.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/key.h b/include/linux/key.h index 044114185120..e315e16b6ff8 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -187,6 +187,7 @@ struct key { #define KEY_FLAG_BUILTIN 8 /* set if key is built in to the kernel */ #define KEY_FLAG_ROOT_CAN_INVAL 9 /* set if key can be invalidated by root without permission */ #define KEY_FLAG_KEEP 10 /* set if key should not be removed */ +#define KEY_FLAG_UID_KEYRING 11 /* set if key is a user or user session keyring */ /* the key type and key description string * - the desc is used to match a key against search criteria @@ -243,6 +244,7 @@ extern struct key *key_alloc(struct key_type *type, #define KEY_ALLOC_NOT_IN_QUOTA 0x0002 /* not in quota */ #define KEY_ALLOC_BUILT_IN 0x0004 /* Key is built into kernel */ #define KEY_ALLOC_BYPASS_RESTRICTION 0x0008 /* Override the check on restricted keyrings */ +#define KEY_ALLOC_UID_KEYRING 0x0010 /* allocating a user or user session keyring */ extern void key_revoke(struct key *key); extern void key_invalidate(struct key *key); |