linux-kernel - Re: [PATCH 04/14] evm: re-release

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Message-ID: <20100426210333.GB2029@us.ibm.com>
Date:	Mon, 26 Apr 2010 16:03:33 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH 04/14] evm: re-release

Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> 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 http://linux-ima.sourceforge.net/#EVM.)
> 
> 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 <zohar@...ibm.com>

Acked-by: Serge Hallyn <serue@...ibm.com>

thanks,
-serge
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