b33e3cc5c9
Pull security subsystem integrity updates from James Morris:
"There is a mixture of bug fixes, code cleanup, preparatory code for
new functionality and new functionality.
Commit 26ddabfe96 ("evm: enable EVM when X509 certificate is
loaded") enabled EVM without loading a symmetric key, but was limited
to defining the x509 certificate pathname at build. Included in this
set of patches is the ability of enabling EVM, without loading the EVM
symmetric key, from userspace. New is the ability to prevent the
loading of an EVM symmetric key."
* 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
ima: Remove redundant conditional operator
ima: Fix bool initialization/comparison
ima: check signature enforcement against cmdline param instead of CONFIG
module: export module signature enforcement status
ima: fix hash algorithm initialization
EVM: Only complain about a missing HMAC key once
EVM: Allow userspace to signal an RSA key has been loaded
EVM: Include security.apparmor in EVM measurements
ima: call ima_file_free() prior to calling fasync
integrity: use kernel_read_file_from_path() to read x509 certs
ima: always measure and audit files in policy
ima: don't remove the securityfs policy file
vfs: fix mounting a filesystem with i_version
44 lines
1.6 KiB
Plaintext
44 lines
1.6 KiB
Plaintext
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 supports two classes of security.evm. The first is
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an HMAC-sha1 generated locally with a
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trusted/encrypted key stored in the Kernel Key
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Retention System. The second is a digital signature
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generated either locally or remotely using an
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asymmetric key. These keys are loaded onto root's
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keyring using keyctl, and EVM is then enabled by
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echoing a value to <securityfs>/evm:
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1: enable HMAC validation and creation
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2: enable digital signature validation
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3: enable HMAC and digital signature validation and HMAC
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creation
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Further writes will be blocked if HMAC support is enabled or
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if bit 32 is set:
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echo 0x80000002 ><securityfs>/evm
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will enable digital signature validation and block
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further writes to <securityfs>/evm.
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Until this is done, EVM can not create or validate the
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'security.evm' xattr, but returns INTEGRITY_UNKNOWN.
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Loading keys and signaling EVM should be done as early
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as possible. Normally this is done in the initramfs,
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which has already been measured as part of the trusted
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boot. For more information on creating and loading
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existing trusted/encrypted keys, refer to:
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Documentation/security/keys/trusted-encrypted.rst. Both dracut
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(via 97masterkey and 98integrity) and systemd (via
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core/ima-setup) have support for loading keys at boot
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time.
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