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- What: security/evm
- Date: March 2011
- Contact: Mimi Zohar <zohar@us.ibm.com>
- Description:
- 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.)
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