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Commit b5f545c8 authored by David Howells's avatar David Howells Committed by Linus Torvalds
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[PATCH] keys: Permit running process to instantiate keys 



Make it possible for a running process (such as gssapid) to be able to
instantiate a key, as was requested by Trond Myklebust for NFS4.

The patch makes the following changes:

 (1) A new, optional key type method has been added. This permits a key type
     to intercept requests at the point /sbin/request-key is about to be
     spawned and do something else with them - passing them over the
     rpc_pipefs files or netlink sockets for instance.

     The uninstantiated key, the authorisation key and the intended operation
     name are passed to the method.

 (2) The callout_info is no longer passed as an argument to /sbin/request-key
     to prevent unauthorised viewing of this data using ps or by looking in
     /proc/pid/cmdline.

     This means that the old /sbin/request-key program will not work with the
     patched kernel as it will expect to see an extra argument that is no
     longer there.

     A revised keyutils package will be made available tomorrow.

 (3) The callout_info is now attached to the authorisation key. Reading this
     key will retrieve the information.

 (4) A new field has been added to the task_struct. This holds the
     authorisation key currently active for a thread. Searches now look here
     for the caller's set of keys rather than looking for an auth key in the
     lowest level of the session keyring.

     This permits a thread to be servicing multiple requests at once and to
     switch between them. Note that this is per-thread, not per-process, and
     so is usable in multithreaded programs.

     The setting of this field is inherited across fork and exec.

 (5) A new keyctl function (KEYCTL_ASSUME_AUTHORITY) has been added that
     permits a thread to assume the authority to deal with an uninstantiated
     key. Assumption is only permitted if the authorisation key associated
     with the uninstantiated key is somewhere in the thread's keyrings.

     This function can also clear the assumption.

 (6) A new magic key specifier has been added to refer to the currently
     assumed authorisation key (KEY_SPEC_REQKEY_AUTH_KEY).

 (7) Instantiation will only proceed if the appropriate authorisation key is
     assumed first. The assumed authorisation key is discarded if
     instantiation is successful.

 (8) key_validate() is moved from the file of request_key functions to the
     file of permissions functions.

 (9) The documentation is updated.

From: <Valdis.Kletnieks@vt.edu>

    Build fix.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Alexander Zangerl <az@bond.edu.au>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent cab8eb59

Documentation/keys-request-key.txt

+12 −10
Original line number Diff line number Diff line
@@ -56,10 +56,12 @@ A request proceeds in the following manner: 
 (4) request_key() then forks and executes /sbin/request-key with a new session

     keyring that contains a link to auth key V.



 (5) /sbin/request-key execs an appropriate program to perform the actual

 (5) /sbin/request-key assumes the authority associated with key U.



 (6) /sbin/request-key execs an appropriate program to perform the actual

     instantiation.



 (6) The program may want to access another key from A's context (say a

 (7) The program may want to access another key from A's context (say a

     Kerberos TGT key). It just requests the appropriate key, and the keyring

     search notes that the session keyring has auth key V in its bottom level.
@@ -67,19 +69,19 @@ A request proceeds in the following manner: 
     UID, GID, groups and security info of process A as if it was process A,

     and come up with key W.



 (7) The program then does what it must to get the data with which to

 (8) The program then does what it must to get the data with which to

     instantiate key U, using key W as a reference (perhaps it contacts a

     Kerberos server using the TGT) and then instantiates key U.



 (8) Upon instantiating key U, auth key V is automatically revoked so that it

 (9) Upon instantiating key U, auth key V is automatically revoked so that it

     may not be used again.



 (9) The program then exits 0 and request_key() deletes key V and returns key

(10) The program then exits 0 and request_key() deletes key V and returns key

     U to the caller.



This also extends further. If key W (step 5 above) didn't exist, key W would be

created uninstantiated, another auth key (X) would be created [as per step 3]

and another copy of /sbin/request-key spawned [as per step 4]; but the context

This also extends further. If key W (step 7 above) didn't exist, key W would be

created uninstantiated, another auth key (X) would be created (as per step 3)

and another copy of /sbin/request-key spawned (as per step 4); but the context

specified by auth key X will still be process A, as it was in auth key V.



This is because process A's keyrings can't simply be attached to
@@ -138,8 +140,8 @@ until one succeeds: 


 (3) The process's session keyring is searched.



 (4) If the process has a request_key() authorisation key in its session

     keyring then:

 (4) If the process has assumed the authority associated with a request_key()

     authorisation key then:



     (a) If extant, the calling process's thread keyring is searched.

Documentation/keys.txt

+24 −0
Original line number Diff line number Diff line
@@ -308,6 +308,8 @@ process making the call: 
	KEY_SPEC_USER_KEYRING		-4	UID-specific keyring

	KEY_SPEC_USER_SESSION_KEYRING	-5	UID-session keyring

	KEY_SPEC_GROUP_KEYRING		-6	GID-specific keyring

	KEY_SPEC_REQKEY_AUTH_KEY	-7	assumed request_key()

						  authorisation key





The main syscalls are:
@@ -645,6 +647,28 @@ The keyctl syscall functions are: 
     or expired keys.





 (*) Assume the authority granted to instantiate a key



	long keyctl(KEYCTL_ASSUME_AUTHORITY, key_serial_t key);



     This assumes or divests the authority required to instantiate the

     specified key. Authority can only be assumed if the thread has the

     authorisation key associated with the specified key in its keyrings

     somewhere.



     Once authority is assumed, searches for keys will also search the

     requester's keyrings using the requester's security label, UID, GID and

     groups.



     If the requested authority is unavailable, error EPERM will be returned,

     likewise if the authority has been revoked because the target key is

     already instantiated.



     If the specified key is 0, then any assumed authority will be divested.



     The assumed authorititive key is inherited across fork and exec.





===============

KERNEL SERVICES

===============

include/linux/key.h

+12 −0
Original line number Diff line number Diff line
@@ -177,6 +177,8 @@ struct key { 
/*

 * kernel managed key type definition

 */

typedef int (*request_key_actor_t)(struct key *key, struct key *authkey, const char *op);



struct key_type {

	/* name of the type */

	const char *name;
@@ -218,6 +220,16 @@ struct key_type { 
	 */

	long (*read)(const struct key *key, char __user *buffer, size_t buflen);



	/* handle request_key() for this type instead of invoking

	 * /sbin/request-key (optional)

	 * - key is the key to instantiate

	 * - authkey is the authority to assume when instantiating this key

	 * - op is the operation to be done, usually "create"

	 * - the call must not return until the instantiation process has run

	 *   its course

	 */

	request_key_actor_t request_key;



	/* internal fields */

	struct list_head	link;		/* link in types list */

};

include/linux/keyctl.h

+2 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#define KEY_SPEC_USER_KEYRING		-4	/* - key ID for UID-specific keyring */

#define KEY_SPEC_USER_SESSION_KEYRING	-5	/* - key ID for UID-session keyring */

#define KEY_SPEC_GROUP_KEYRING		-6	/* - key ID for GID-specific keyring */

#define KEY_SPEC_REQKEY_AUTH_KEY	-7	/* - key ID for assumed request_key auth key */



/* request-key default keyrings */

#define KEY_REQKEY_DEFL_NO_CHANGE		-1
@@ -47,5 +48,6 @@ 
#define KEYCTL_NEGATE			13	/* negate a partially constructed key */

#define KEYCTL_SET_REQKEY_KEYRING	14	/* set default request-key keyring */

#define KEYCTL_SET_TIMEOUT		15	/* set key timeout */

#define KEYCTL_ASSUME_AUTHORITY		16	/* assume request_key() authorisation */



#endif /*  _LINUX_KEYCTL_H */

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -771,6 +771,7 @@ struct task_struct { 
	unsigned keep_capabilities:1;

	struct user_struct *user;

#ifdef CONFIG_KEYS

	struct key *request_key_auth;	/* assumed request_key authority */

	struct key *thread_keyring;	/* keyring private to this thread */

	unsigned char jit_keyring;	/* default keyring to attach requested keys to */

#endif