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+What: security/evm
+Date: March 2011
+Contact: Mimi Zohar <zohar@us.ibm.com>
+ EVM protects a file's security extended attributes(xattrs)
+ against integrity attacks. The initial method maintains an
+ HMAC-sha1 value across the extended attributes, storing the
+ value as the extended attribute 'security.evm'.
+ EVM depends on the Kernel Key Retention System to provide it
+ with a trusted/encrypted key for the HMAC-sha1 operation.
+ The key is loaded onto the root's keyring using keyctl. Until
+ EVM receives notification that the key has been successfully
+ loaded onto the keyring (echo 1 > <securityfs>/evm), EVM
+ can not create or validate the 'security.evm' xattr, but
+ returns INTEGRITY_UNKNOWN. Loading the key and signaling EVM
+ should be done as early as possible. Normally this is done
+ in the initramfs, which has already been measured as part
+ of the trusted boot. For more information on creating and
+ loading existing trusted/encrypted keys, refer to:
+ Documentation/keys-trusted-encrypted.txt. (A sample dracut
+ patch, which loads the trusted/encrypted key and enables
+ EVM, is available from http://linux-ima.sourceforge.net/#EVM.)