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Commit 794b4bc2 authored by Eric Biggers's avatar Eric Biggers Committed by James Morris
Browse files

KEYS: encrypted: fix buffer overread in valid_master_desc() 



With the 'encrypted' key type it was possible for userspace to provide a
data blob ending with a master key description shorter than expected,
e.g. 'keyctl add encrypted desc "new x" @s'.  When validating such a
master key description, validate_master_desc() could read beyond the end
of the buffer.  Fix this by using strncmp() instead of memcmp().  [Also
clean up the code to deduplicate some logic.]

Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarJames Morris <james.l.morris@oracle.com>
parent e9ff56ac

security/keys/encrypted-keys/encrypted.c

+15 −16
Original line number Diff line number Diff line
@@ -141,23 +141,22 @@ static int valid_ecryptfs_desc(const char *ecryptfs_desc) 
 */

static int valid_master_desc(const char *new_desc, const char *orig_desc)

{

	if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {

		if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)

			goto out;

		if (orig_desc)

			if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))

				goto out;

	} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {

		if (strlen(new_desc) == KEY_USER_PREFIX_LEN)

			goto out;

		if (orig_desc)

			if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))

				goto out;

	} else

		goto out;

	return 0;

out:

	int prefix_len;



	if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))

		prefix_len = KEY_TRUSTED_PREFIX_LEN;

	else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))

		prefix_len = KEY_USER_PREFIX_LEN;

	else

		return -EINVAL;



	if (!new_desc[prefix_len])

		return -EINVAL;



	if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))

		return -EINVAL;



	return 0;

}



/*