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Commit 927942aa authored by David Howells's avatar David Howells Committed by James Morris
Browse files

KEYS: Make /proc/keys check to see if a key is possessed before security check 



Make /proc/keys check to see if the calling process possesses each key before
performing the security check.  The possession check can be skipped if the key
doesn't have the possessor-view permission bit set.

This causes the keys a process possesses to show up in /proc/keys, even if they
don't have matching user/group/other view permissions.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 9156235b

security/keys/internal.h

+5 −0
Original line number Diff line number Diff line
@@ -114,6 +114,10 @@ extern key_ref_t keyring_search_aux(key_ref_t keyring_ref, 
				    const void *description,

				    key_match_func_t match);



extern key_ref_t search_my_process_keyrings(struct key_type *type,

					    const void *description,

					    key_match_func_t match,

					    const struct cred *cred);

extern key_ref_t search_process_keyrings(struct key_type *type,

					 const void *description,

					 key_match_func_t match,
@@ -134,6 +138,7 @@ extern struct key *request_key_and_link(struct key_type *type, 
					struct key *dest_keyring,

					unsigned long flags);



extern int lookup_user_key_possessed(const struct key *key, const void *target);

extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,

				 key_perm_t perm);

#define KEY_LOOKUP_CREATE	0x01

security/keys/proc.c

+18 −2
Original line number Diff line number Diff line
@@ -184,20 +184,36 @@ static void proc_keys_stop(struct seq_file *p, void *v) 


static int proc_keys_show(struct seq_file *m, void *v)

{

	const struct cred *cred = current_cred();

	struct rb_node *_p = v;

	struct key *key = rb_entry(_p, struct key, serial_node);

	struct timespec now;

	unsigned long timo;

	key_ref_t key_ref, skey_ref;

	char xbuf[12];

	int rc;



	key_ref = make_key_ref(key, 0);



	/* determine if the key is possessed by this process (a test we can

	 * skip if the key does not indicate the possessor can view it

	 */

	if (key->perm & KEY_POS_VIEW) {

		skey_ref = search_my_process_keyrings(key->type, key,

						      lookup_user_key_possessed,

						      cred);

		if (!IS_ERR(skey_ref)) {

			key_ref_put(skey_ref);

			key_ref = make_key_ref(key, 1);

		}

	}



	/* check whether the current task is allowed to view the key (assuming

	 * non-possession)

	 * - the caller holds a spinlock, and thus the RCU read lock, making our

	 *   access to __current_cred() safe

	 */

	rc = key_task_permission(make_key_ref(key, 0), current_cred(),

				 KEY_VIEW);

	rc = key_task_permission(key_ref, cred, KEY_VIEW);

	if (rc < 0)

		return 0;

security/keys/process_keys.c

+43 −21
Original line number Diff line number Diff line
@@ -309,22 +309,19 @@ void key_fsgid_changed(struct task_struct *tsk) 


/*****************************************************************************/

/*

 * search the process keyrings for the first matching key

 * search only my process keyrings for the first matching key

 * - we use the supplied match function to see if the description (or other

 *   feature of interest) matches

 * - we return -EAGAIN if we didn't find any matching key

 * - we return -ENOKEY if we found only negative matching keys

 */

key_ref_t search_process_keyrings(struct key_type *type,

key_ref_t search_my_process_keyrings(struct key_type *type,

				     const void *description,

				     key_match_func_t match,

				     const struct cred *cred)

{

	struct request_key_auth *rka;

	key_ref_t key_ref, ret, err;



	might_sleep();



	/* we want to return -EAGAIN or -ENOKEY if any of the keyrings were

	 * searchable, but we failed to find a key or we found a negative key;

	 * otherwise we want to return a sample error (probably -EACCES) if
@@ -424,6 +421,36 @@ key_ref_t search_process_keyrings(struct key_type *type, 
		}

	}



	/* no key - decide on the error we're going to go for */

	key_ref = ret ? ret : err;



found:

	return key_ref;

}



/*****************************************************************************/

/*

 * search the process keyrings for the first matching key

 * - we use the supplied match function to see if the description (or other

 *   feature of interest) matches

 * - we return -EAGAIN if we didn't find any matching key

 * - we return -ENOKEY if we found only negative matching keys

 */

key_ref_t search_process_keyrings(struct key_type *type,

				  const void *description,

				  key_match_func_t match,

				  const struct cred *cred)

{

	struct request_key_auth *rka;

	key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;



	might_sleep();



	key_ref = search_my_process_keyrings(type, description, match, cred);

	if (!IS_ERR(key_ref))

		goto found;

	err = key_ref;



	/* if this process has an instantiation authorisation key, then we also

	 * search the keyrings of the process mentioned there

	 * - we don't permit access to request_key auth keys via this method
@@ -446,24 +473,19 @@ key_ref_t search_process_keyrings(struct key_type *type, 
			if (!IS_ERR(key_ref))

				goto found;



			switch (PTR_ERR(key_ref)) {

			case -EAGAIN: /* no key */

				if (ret)

					break;

			case -ENOKEY: /* negative key */

			ret = key_ref;

				break;

			default:

				err = key_ref;

				break;

			}

		} else {

			up_read(&cred->request_key_auth->sem);

		}

	}



	/* no key - decide on the error we're going to go for */

	key_ref = ret ? ret : err;

	if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))

		key_ref = ERR_PTR(-ENOKEY);

	else if (err == ERR_PTR(-EACCES))

		key_ref = ret;

	else

		key_ref = err;



found:

	return key_ref;
@@ -474,7 +496,7 @@ key_ref_t search_process_keyrings(struct key_type *type, 
/*

 * see if the key we're looking at is the target key

 */

static int lookup_user_key_possessed(const struct key *key, const void *target)

int lookup_user_key_possessed(const struct key *key, const void *target)

{

	return key == target;