Commit f66665c0 authored by Eric Biggers's avatar Eric Biggers Committed by David Howells
Browse files

ecryptfs: fix dereference of NULL user_key_payload 



In eCryptfs, we failed to verify that the authentication token keys are
not revoked before dereferencing their payloads, which is problematic
because the payload of a revoked key is NULL.  request_key() *does* skip
revoked keys, but there is still a window where the key can be revoked
before we acquire the key semaphore.

Fix it by updating ecryptfs_get_key_payload_data() to return
-EKEYREVOKED if the key payload is NULL.  For completeness we check this
for "encrypted" keys as well as "user" keys, although encrypted keys
cannot be revoked currently.

Alternatively we could use key_validate(), but since we'll also need to
fix ecryptfs_get_key_payload_data() to validate the payload length, it
seems appropriate to just check the payload pointer.

Fixes: 237fead6 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig")
Reviewed-by: default avatarJames Morris <james.l.morris@oracle.com>
Cc: <stable@vger.kernel.org>    [v2.6.19+]
Cc: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent d60b5b78

fs/ecryptfs/ecryptfs_kernel.h

+17 −7
Original line number Diff line number Diff line
@@ -84,11 +84,16 @@ struct ecryptfs_page_crypt_context { 
static inline struct ecryptfs_auth_tok *

ecryptfs_get_encrypted_key_payload_data(struct key *key)

{

	if (key->type == &key_type_encrypted)

		return (struct ecryptfs_auth_tok *)

			(&((struct encrypted_key_payload *)key->payload.data[0])->payload_data);

	else

	struct encrypted_key_payload *payload;



	if (key->type != &key_type_encrypted)

		return NULL;



	payload = key->payload.data[0];

	if (!payload)

		return ERR_PTR(-EKEYREVOKED);



	return (struct ecryptfs_auth_tok *)payload->payload_data;

}



static inline struct key *ecryptfs_get_encrypted_key(char *sig)
@@ -114,12 +119,17 @@ static inline struct ecryptfs_auth_tok * 
ecryptfs_get_key_payload_data(struct key *key)

{

	struct ecryptfs_auth_tok *auth_tok;

	struct user_key_payload *ukp;



	auth_tok = ecryptfs_get_encrypted_key_payload_data(key);

	if (!auth_tok)

		return (struct ecryptfs_auth_tok *)user_key_payload_locked(key)->data;

	else

	if (auth_tok)

		return auth_tok;



	ukp = user_key_payload_locked(key);

	if (!ukp)

		return ERR_PTR(-EKEYREVOKED);



	return (struct ecryptfs_auth_tok *)ukp->data;

}



#define ECRYPTFS_MAX_KEYSET_SIZE 1024

fs/ecryptfs/keystore.c

+8 −1
Original line number Diff line number Diff line
@@ -459,7 +459,8 @@ out: 
 * @auth_tok_key: key containing the authentication token

 * @auth_tok: authentication token

 *

 * Returns zero on valid auth tok; -EINVAL otherwise

 * Returns zero on valid auth tok; -EINVAL if the payload is invalid; or

 * -EKEYREVOKED if the key was revoked before we acquired its semaphore.

 */

static int

ecryptfs_verify_auth_tok_from_key(struct key *auth_tok_key,
@@ -468,6 +469,12 @@ ecryptfs_verify_auth_tok_from_key(struct key *auth_tok_key, 
	int rc = 0;



	(*auth_tok) = ecryptfs_get_key_payload_data(auth_tok_key);

	if (IS_ERR(*auth_tok)) {

		rc = PTR_ERR(*auth_tok);

		*auth_tok = NULL;

		goto out;

	}



	if (ecryptfs_verify_version((*auth_tok)->version)) {

		printk(KERN_ERR "Data structure version mismatch. Userspace "

		       "tools must match eCryptfs kernel module with major "

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