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