Commit Graph

12 Commits

Author SHA1 Message Date
Linus Torvalds
028db3e290 Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs"
This reverts merge 0f75ef6a9c (and thus
effectively commits

   7a1ade8475 ("keys: Provide KEYCTL_GRANT_PERMISSION")
   2e12256b9a ("keys: Replace uid/gid/perm permissions checking with an ACL")

that the merge brought in).

It turns out that it breaks booting with an encrypted volume, and Eric
biggers reports that it also breaks the fscrypt tests [1] and loading of
in-kernel X.509 certificates [2].

The root cause of all the breakage is likely the same, but David Howells
is off email so rather than try to work it out it's getting reverted in
order to not impact the rest of the merge window.

 [1] https://lore.kernel.org/lkml/20190710011559.GA7973@sol.localdomain/
 [2] https://lore.kernel.org/lkml/20190710013225.GB7973@sol.localdomain/

Link: https://lore.kernel.org/lkml/CAHk-=wjxoeMJfeBahnWH=9zShKp2bsVy527vo3_y8HfOdhwAAw@mail.gmail.com/
Reported-by: Eric Biggers <ebiggers@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-10 18:43:43 -07:00
David Howells
2e12256b9a keys: Replace uid/gid/perm permissions checking with an ACL
Replace the uid/gid/perm permissions checking on a key with an ACL to allow
the SETATTR and SEARCH permissions to be split.  This will also allow a
greater range of subjects to represented.

============
WHY DO THIS?
============

The problem is that SETATTR and SEARCH cover a slew of actions, not all of
which should be grouped together.

For SETATTR, this includes actions that are about controlling access to a
key:

 (1) Changing a key's ownership.

 (2) Changing a key's security information.

 (3) Setting a keyring's restriction.

And actions that are about managing a key's lifetime:

 (4) Setting an expiry time.

 (5) Revoking a key.

and (proposed) managing a key as part of a cache:

 (6) Invalidating a key.

Managing a key's lifetime doesn't really have anything to do with
controlling access to that key.

Expiry time is awkward since it's more about the lifetime of the content
and so, in some ways goes better with WRITE permission.  It can, however,
be set unconditionally by a process with an appropriate authorisation token
for instantiating a key, and can also be set by the key type driver when a
key is instantiated, so lumping it with the access-controlling actions is
probably okay.

As for SEARCH permission, that currently covers:

 (1) Finding keys in a keyring tree during a search.

 (2) Permitting keyrings to be joined.

 (3) Invalidation.

But these don't really belong together either, since these actions really
need to be controlled separately.

Finally, there are number of special cases to do with granting the
administrator special rights to invalidate or clear keys that I would like
to handle with the ACL rather than key flags and special checks.


===============
WHAT IS CHANGED
===============

The SETATTR permission is split to create two new permissions:

 (1) SET_SECURITY - which allows the key's owner, group and ACL to be
     changed and a restriction to be placed on a keyring.

 (2) REVOKE - which allows a key to be revoked.

The SEARCH permission is split to create:

 (1) SEARCH - which allows a keyring to be search and a key to be found.

 (2) JOIN - which allows a keyring to be joined as a session keyring.

 (3) INVAL - which allows a key to be invalidated.

The WRITE permission is also split to create:

 (1) WRITE - which allows a key's content to be altered and links to be
     added, removed and replaced in a keyring.

 (2) CLEAR - which allows a keyring to be cleared completely.  This is
     split out to make it possible to give just this to an administrator.

 (3) REVOKE - see above.


Keys acquire ACLs which consist of a series of ACEs, and all that apply are
unioned together.  An ACE specifies a subject, such as:

 (*) Possessor - permitted to anyone who 'possesses' a key
 (*) Owner - permitted to the key owner
 (*) Group - permitted to the key group
 (*) Everyone - permitted to everyone

Note that 'Other' has been replaced with 'Everyone' on the assumption that
you wouldn't grant a permit to 'Other' that you wouldn't also grant to
everyone else.

Further subjects may be made available by later patches.

The ACE also specifies a permissions mask.  The set of permissions is now:

	VIEW		Can view the key metadata
	READ		Can read the key content
	WRITE		Can update/modify the key content
	SEARCH		Can find the key by searching/requesting
	LINK		Can make a link to the key
	SET_SECURITY	Can change owner, ACL, expiry
	INVAL		Can invalidate
	REVOKE		Can revoke
	JOIN		Can join this keyring
	CLEAR		Can clear this keyring


The KEYCTL_SETPERM function is then deprecated.

The KEYCTL_SET_TIMEOUT function then is permitted if SET_SECURITY is set,
or if the caller has a valid instantiation auth token.

The KEYCTL_INVALIDATE function then requires INVAL.

The KEYCTL_REVOKE function then requires REVOKE.

The KEYCTL_JOIN_SESSION_KEYRING function then requires JOIN to join an
existing keyring.

The JOIN permission is enabled by default for session keyrings and manually
created keyrings only.


======================
BACKWARD COMPATIBILITY
======================

To maintain backward compatibility, KEYCTL_SETPERM will translate the
permissions mask it is given into a new ACL for a key - unless
KEYCTL_SET_ACL has been called on that key, in which case an error will be
returned.

It will convert possessor, owner, group and other permissions into separate
ACEs, if each portion of the mask is non-zero.

SETATTR permission turns on all of INVAL, REVOKE and SET_SECURITY.  WRITE
permission turns on WRITE, REVOKE and, if a keyring, CLEAR.  JOIN is turned
on if a keyring is being altered.

The KEYCTL_DESCRIBE function translates the ACL back into a permissions
mask to return depending on possessor, owner, group and everyone ACEs.

It will make the following mappings:

 (1) INVAL, JOIN -> SEARCH

 (2) SET_SECURITY -> SETATTR

 (3) REVOKE -> WRITE if SETATTR isn't already set

 (4) CLEAR -> WRITE

Note that the value subsequently returned by KEYCTL_DESCRIBE may not match
the value set with KEYCTL_SETATTR.


=======
TESTING
=======

This passes the keyutils testsuite for all but a couple of tests:

 (1) tests/keyctl/dh_compute/badargs: The first wrong-key-type test now
     returns EOPNOTSUPP rather than ENOKEY as READ permission isn't removed
     if the type doesn't have ->read().  You still can't actually read the
     key.

 (2) tests/keyctl/permitting/valid: The view-other-permissions test doesn't
     work as Other has been replaced with Everyone in the ACL.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-06-27 23:03:07 +01:00
David Howells
a58946c158 keys: Pass the network namespace into request_key mechanism
Create a request_key_net() function and use it to pass the network
namespace domain tag into DNS revolver keys and rxrpc/AFS keys so that keys
for different domains can coexist in the same keyring.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: netdev@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-afs@lists.infradead.org
2019-06-27 23:02:12 +01:00
David Howells
3b8c4a08a4 keys: Kill off request_key_async{,_with_auxdata}
Kill off request_key_async{,_with_auxdata}() as they're not currently used.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-06-26 20:58:13 +01:00
David Howells
7743c48e54 keys: Cache result of request_key*() temporarily in task_struct
If a filesystem uses keys to hold authentication tokens, then it needs a
token for each VFS operation that might perform an authentication check -
either by passing it to the server, or using to perform a check based on
authentication data cached locally.

For open files this isn't a problem, since the key should be cached in the
file struct since it represents the subject performing operations on that
file descriptor.

During pathwalk, however, there isn't anywhere to cache the key, except
perhaps in the nameidata struct - but that isn't exposed to the
filesystems.  Further, a pathwalk can incur a lot of operations, calling
one or more of the following, for instance:

	->lookup()
	->permission()
	->d_revalidate()
	->d_automount()
	->get_acl()
	->getxattr()

on each dentry/inode it encounters - and each one may need to call
request_key().  And then, at the end of pathwalk, it will call the actual
operation:

	->mkdir()
	->mknod()
	->getattr()
	->open()
	...

which may need to go and get the token again.

However, it is very likely that all of the operations on a single
dentry/inode - and quite possibly a sequence of them - will all want to use
the same authentication token, which suggests that caching it would be a
good idea.

To this end:

 (1) Make it so that a positive result of request_key() and co. that didn't
     require upcalling to userspace is cached temporarily in task_struct.

 (2) The cache is 1 deep, so a new result displaces the old one.

 (3) The key is released by exit and by notify-resume.

 (4) The cache is cleared in a newly forked process.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-06-19 16:10:15 +01:00
David Howells
896f1950e5 keys: Provide request_key_rcu()
Provide a request_key_rcu() function that can be used to request a key
under RCU conditions.  It can only search and check permissions; it cannot
allocate a new key, upcall or wait for an upcall to complete.  It may
return a partially constructed key.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-06-19 16:10:15 +01:00
David Howells
e59428f721 keys: Move the RCU locks outwards from the keyring search functions
Move the RCU locks outwards from the keyring search functions so that it
will become possible to provide an RCU-capable partial request_key()
function in a later commit.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-06-19 16:10:15 +01:00
Will Deacon
806654a966 Documentation: Use "while" instead of "whilst"
Whilst making an unrelated change to some Documentation, Linus sayeth:

  | Afaik, even in Britain, "whilst" is unusual and considered more
  | formal, and "while" is the common word.
  |
  | [...]
  |
  | Can we just admit that we work with computers, and we don't need to
  | use þe eald Englisc spelling of words that most of the world never
  | uses?

dictionary.com refers to the word as "Chiefly British", which is
probably an undesirable attribute for technical documentation.

Replace all occurrences under Documentation/ with "while".

Cc: David Howells <dhowells@redhat.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michael Halcrow <mhalcrow@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-11-20 09:30:43 -07:00
Tom Saeger
c7f66400f5 Documentation: fix security related doc refs
Make security document refs valid.

Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-10-12 11:14:40 -06:00
Josh Holland
adf31eebd7 docs: Fix paths in security/keys
Several paths in the security/keys documentation were incorrect.

Signed-off-by: Josh Holland <anowlcalledjosh@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-08-24 13:10:58 -06:00
Jonathan Corbet
5ea787a7ec docs: Fix some formatting issues in request-key.rst
The white space in the big enumerated list was inconsistent, leading to
some strange formatting artifacts.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-05-18 10:46:25 -06:00
Kees Cook
3db38ed768 doc: ReSTify keys-request-key.txt
Adjusts for ReST markup and moves under keys security devel index.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-05-18 10:33:51 -06:00