Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull keyring ACL support from David Howells:
 "This changes the permissions model used by keys and keyrings to be
  based on an internal ACL by the following means:

   - Replace the permissions mask internally with an ACL that contains a
     list of ACEs, each with a specific subject with a permissions mask.
     Potted default ACLs are available for new keys and keyrings.

     ACE subjects can be macroised to indicate the UID and GID specified
     on the key (which remain). Future commits will be able to add
     additional subject types, such as specific UIDs or domain
     tags/namespaces.

     Also split a number of permissions to give finer control. Examples
     include splitting the revocation permit from the change-attributes
     permit, thereby allowing someone to be granted permission to revoke
     a key without allowing them to change the owner; also the ability
     to join a keyring is split from the ability to link to it, thereby
     stopping a process accessing a keyring by joining it and thus
     acquiring use of possessor permits.

   - Provide a keyctl to allow the granting or denial of one or more
     permits to a specific subject. Direct access to the ACL is not
     granted, and the ACL cannot be viewed"

* tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  keys: Provide KEYCTL_GRANT_PERMISSION
  keys: Replace uid/gid/perm permissions checking with an ACL

2 files changed, 106 insertions, 31 deletions

diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst
index 0e74f372e58c..1b3c907980ad 100644
--- a/Documentation/security/keys/core.rst
+++ b/Documentation/security/keys/core.rst
@@ -57,9 +57,9 @@ Each key has a number of attributes:
      type provides an operation to perform a match between the description on a
      key and a criterion string.
 
-  *  Each key has an owner user ID, a group ID and a permissions mask. These
-     are used to control what a process may do to a key from userspace, and
-     whether a kernel service will be able to find the key.
+  *  Each key has an owner user ID, a group ID and an ACL.  These are used to
+     control what a process may do to a key from userspace, and whether a
+     kernel service will be able to find the key.
 
   *  Each key can be set to expire at a specific time by the key type's
      instantiation function. Keys can also be immortal.
@@ -198,43 +198,110 @@ The key service provides a number of features besides keys:
 Key Access Permissions
 ======================
 
-Keys have an owner user ID, a group access ID, and a permissions mask. The mask
-has up to eight bits each for possessor, user, group and other access. Only
-six of each set of eight bits are defined. These permissions granted are:
+Keys have an owner user ID, a group ID and an ACL.  The ACL is made up of a
+sequence of ACEs that each contain three elements:
 
-  *  View
+  * The type of subject.
+  * The subject.
 
-     This permits a key or keyring's attributes to be viewed - including key
-     type and description.
+    These two together indicate the subject to whom the permits are granted.
+    The type can be one of:
 
-  *  Read
+     * ``KEY_ACE_SUBJ_STANDARD``
 
-     This permits a key's payload to be viewed or a keyring's list of linked
-     keys.
+       The subject is a standard 'macro' type.  The subject can be one of:
+
+        * ``KEY_ACE_EVERYONE``
+
+	  The permits are granted to everyone.  It replaces the old 'other'
+	  type on the assumption that you wouldn't grant a permission to other
+	  that you you wouldn't grant to everyone else.
+
+	* ``KEY_ACE_OWNER``
+
+	  The permits are granted to the owner of the key (key->uid).
+
+	* ``KEY_ACE_GROUP``
+
+	  The permits are granted to the key's group (key->gid).
+
+	* ``KEY_ACE_POSSESSOR``
+
+	  The permits are granted to anyone who possesses the key.
+
+  * The set of permits granted to the subject.  These include:
+
+     * ``KEY_ACE_VIEW``
+
+       This permits a key or keyring's attributes to be viewed - including the
+       key type and description.
+
+     * ``KEY_ACE_READ``
+
+       This permits a key's payload to be viewed or a keyring's list of linked
+       keys.
 
-  *  Write
+     * ``KEY_ACE_WRITE``
 
-     This permits a key's payload to be instantiated or updated, or it allows a
-     link to be added to or removed from a keyring.
+       This permits a key's payload to be instantiated or updated, or it allows
+       a link to be added to or removed from a keyring.
 
-  *  Search
+     * ``KEY_ACE_SEARCH``
 
-     This permits keyrings to be searched and keys to be found. Searches can
-     only recurse into nested keyrings that have search permission set.
+       This permits keyrings to be searched and keys to be found. Searches can
+       only recurse into nested keyrings that have search permission set.
 
-  *  Link
+     * ``KEY_ACE_LINK``
 
-     This permits a key or keyring to be linked to. To create a link from a
-     keyring to a key, a process must have Write permission on the keyring and
-     Link permission on the key.
+       This permits a key or keyring to be linked to. To create a link from a
+       keyring to a key, a process must have Write permission on the keyring
+       and Link permission on the key.
 
-  *  Set Attribute
+     * ``KEY_ACE_SET_SECURITY``
 
-     This permits a key's UID, GID and permissions mask to be changed.
+       This permits a key's UID, GID and permissions mask to be changed.
+
+     * ``KEY_ACE_INVAL``
+
+       This permits a key to be invalidated with KEYCTL_INVALIDATE.
+
+     * ``KEY_ACE_REVOKE``
+
+       This permits a key to be revoked with KEYCTL_REVOKE.
+
+     * ``KEY_ACE_JOIN``
+
+       This permits a keyring to be joined as a session by
+       KEYCTL_JOIN_SESSION_KEYRING or KEYCTL_SESSION_TO_PARENT.
+
+     * ``KEY_ACE_CLEAR``
+
+       This permits a keyring to be cleared.
 
 For changing the ownership, group ID or permissions mask, being the owner of
 the key or having the sysadmin capability is sufficient.
 
+The legacy KEYCTL_SETPERM and KEYCTL_DESCRIBE functions can only see/generate
+View, Read, Write, Search, Link and SetAttr permits, and do this for each of
+possessor, user, group and other permission sets as a 32-bit flag mask.  These
+will be approximated/inferred:
+
+	SETPERM Permit	Implied ACE Permit
+	===============	=======================
+	Search		Inval, Join
+	Write		Revoke, Clear
+	Setattr		Set Security, Revoke
+
+	ACE Permit	Described as
+	===============	=======================
+	Inval		Search
+	Join		Search
+	Revoke		Write (unless Setattr)
+	Clear		write
+	Set Security	Setattr
+
+'Other' will be approximated as/inferred from the 'Everyone' subject.
+
 
 SELinux Support
 ===============
@@ -1084,7 +1151,8 @@ payload contents" for more information.
 
 	struct key *request_key(const struct key_type *type,
 				const char *description,
-				const char *callout_info);
+				const char *callout_info,
+				struct key_acl *acl);
 
     This is used to request a key or keyring with a description that matches
     the description specified according to the key type's match_preparse()
@@ -1099,6 +1167,8 @@ payload contents" for more information.
     If successful, the key will have been attached to the default keyring for
     implicitly obtained request-key keys, as set by KEYCTL_SET_REQKEY_KEYRING.
 
+    If a key is created, it will be given the specified ACL.
+
     See also Documentation/security/keys/request-key.rst.
 
 
@@ -1107,7 +1177,8 @@ payload contents" for more information.
 	struct key *request_key_tag(const struct key_type *type,
 				    const char *description,
 				    struct key_tag *domain_tag,
-				    const char *callout_info);
+				    const char *callout_info,
+				    struct key_acl *acl);
 
     This is identical to request_key(), except that a domain tag may be
     specifies that causes search algorithm to only match keys matching that
@@ -1122,7 +1193,8 @@ payload contents" for more information.
 					     struct key_tag *domain_tag,
 					     const void *callout_info,
 					     size_t callout_len,
-					     void *aux);
+					     void *aux,
+					     struct key_acl *acl);
 
     This is identical to request_key_tag(), except that the auxiliary data is
     passed to the key_type->request_key() op if it exists, and the
@@ -1195,7 +1267,7 @@ payload contents" for more information.
 
 	struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
 				  const struct cred *cred,
-				  key_perm_t perm,
+				  struct key_acl *acl,
 				  struct key_restriction *restrict_link,
 				  unsigned long flags,
 				  struct key *dest);
diff --git a/Documentation/security/keys/request-key.rst b/Documentation/security/keys/request-key.rst
index 35f2296b704a..f356fd06c8d5 100644
--- a/Documentation/security/keys/request-key.rst
+++ b/Documentation/security/keys/request-key.rst
@@ -11,14 +11,16 @@ The process starts by either the kernel requesting a service by calling
 
 	struct key *request_key(const struct key_type *type,
 				const char *description,
-				const char *callout_info);
+				const char *callout_info,
+				struct key_acl *acl);
 
 or::
 
 	struct key *request_key_tag(const struct key_type *type,
 				    const char *description,
 				    const struct key_tag *domain_tag,
-				    const char *callout_info);
+				    const char *callout_info,
+				    struct key_acl *acl);
 
 or::
 
@@ -27,7 +29,8 @@ or::
 					     const struct key_tag *domain_tag,
 					     const char *callout_info,
 					     size_t callout_len,
-					     void *aux);
+					     void *aux,
+					     struct key_acl *acl);
 
 or::