tree 83bb9c589051fd7269a9cd2bf1d7be9a955eccbd
parent 6e38bfaad6c83bdd07eb659f9bfd50f8d71a5a46
author Dmitry Kasatkin <dmitry.kasatkin@intel.com> 1347262640 +0300
committer Mimi Zohar <zohar@linux.vnet.ibm.com> 1360165228 -0500

evm: add file system uuid to EVM hmac

EVM uses the same key for all file systems to calculate the HMAC,
making it possible to paste inodes from one file system on to another
one, without EVM being able to detect it.  To prevent such an attack,
it is necessary to make the EVM HMAC file system specific.

This patch uses the file system UUID, a file system unique identifier,
to bind the EVM HMAC to the file system. The value inode->i_sb->s_uuid
is used for the HMAC hash calculation, instead of using it for deriving
the file system specific key.  Initializing the key for every inode HMAC
calculation is a bit more expensive operation than adding the uuid to
the HMAC hash.

Changing the HMAC calculation method or adding additional info to the
calculation, requires existing EVM labeled file systems to be relabeled.
This patch adds a Kconfig HMAC version option for backwards compatability.

Changelog v1:
- squash "hmac version setting"
Changelog v0:
- add missing Kconfig depends (Mimi)

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>