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    SubjectRe: [PATCH 04/14] evm: re-release
    Quoting Mimi Zohar (
    > EVM protects a file's security extended attributes against integrity
    > attacks. It maintains an HMAC-sha1 value across the extended attributes,
    > storing the value as the extended attribute 'security.evm'. EVM has gone
    > through a number of iterations, initially as an LSM module, subsequently
    > as a LIM integrity provider, and now, when co-located with a security_
    > hook, embedded directly in the security_ hook, similar to IMA.
    > This is the first part of a local file integrity verification system.
    > While this part does authenticate the selected extended attributes, and
    > cryptographically bind them to the inode, coming extensions will bind
    > other directory and inode metadata for more complete protection. The
    > set of protected security extended attributes is configured at compile.
    > EVM depends on the Kernel Key Retention System to provide it with the
    > kernel master key for the HMAC operation. The kernel master key is
    > securely loaded onto the root's keyring, typically by 'loadkernkey',
    > which either uses the TPM sealed secret key, if available, or a
    > password requested from the console. To signal EVM, that the key has
    > been loaded onto the keyring, 'echo 1 > <securityfs>/evm'. This is
    > normally done in the initrd, which has already been measured as part
    > of the trusted boot. (Refer to
    > EVM adds the following three calls to the existing security hooks,
    > evm_inode_setxattr(), evm_inode_post_setxattr(), and
    > evm_inode_removexattr.
    > To initialize and update the 'security.evm' extended attribute, EVM
    > defines three calls: evm_inode_post_init(), evm_inode_post_setattr()
    > and evm_inode_post_removexattr() hooks.
    > To verify the integrity of an extended attribute, EVM exports
    > evm_verifyxattr().
    > Signed-off-by: Mimi Zohar <>

    Acked-by: Serge Hallyn <>


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