Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 101 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm
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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 supports two classes of security.evm. The first is
+		an HMAC-sha1 generated locally with a
+		trusted/encrypted key stored in the Kernel Key
+		Retention System. The second is a digital signature
+		generated either locally or remotely using an
+		asymmetric key. These keys are loaded onto root's
+		keyring using keyctl, and EVM is then enabled by
+		echoing a value to <securityfs>/evm made up of the
+		following bits:
+
+		===	  ==================================================
+		Bit	  Effect
+		===	  ==================================================
+		0	  Enable HMAC validation and creation
+		1	  Enable digital signature validation
+		2	  Permit modification of EVM-protected metadata at
+			  runtime. Not supported if HMAC validation and
+			  creation is enabled.
+		31	  Disable further runtime modification of EVM policy
+		===	  ==================================================
+
+		For example::
+
+		  echo 1 ><securityfs>/evm
+
+		will enable HMAC validation and creation
+
+		::
+
+		  echo 0x80000003 ><securityfs>/evm
+
+		will enable HMAC and digital signature validation and
+		HMAC creation and disable all further modification of policy.
+
+		::
+
+		  echo 0x80000006 ><securityfs>/evm
+
+		will enable digital signature validation, permit
+		modification of EVM-protected metadata and
+		disable all further modification of policy
+
+		Echoing a value is additive, the new value is added to the
+		existing initialization flags.
+
+		For example, after::
+
+		  echo 2 ><securityfs>/evm
+
+		another echo can be performed::
+
+		  echo 1 ><securityfs>/evm
+
+		and the resulting value will be 3.
+
+		Note that once an HMAC key has been loaded, it will no longer
+		be possible to enable metadata modification. Signaling that an
+		HMAC key has been loaded will clear the corresponding flag.
+		For example, if the current value is 6 (2 and 4 set)::
+
+		  echo 1 ><securityfs>/evm
+
+		will set the new value to 3 (4 cleared).
+
+		Loading an HMAC key is the only way to disable metadata
+		modification.
+
+		Until key loading has been signaled EVM can not create
+		or validate the 'security.evm' xattr, but returns
+		INTEGRITY_UNKNOWN.  Loading keys 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/security/keys/trusted-encrypted.rst. Both
+		dracut (via 97masterkey and 98integrity) and systemd (via
+		core/ima-setup) have support for loading keys at boot
+		time.
+
+What:		security/integrity/evm/evm_xattrs
+Date:		April 2018
+Contact:	Matthew Garrett <mjg59@google.com>
+Description:
+		Shows the set of extended attributes used to calculate or
+		validate the EVM signature, and allows additional attributes
+		to be added at runtime. Any signatures generated after
+		additional attributes are added (and on files possessing those
+		additional attributes) will only be valid if the same
+		additional attributes are configured on system boot. Writing
+		a single period (.) will lock the xattr list from any further
+		modification.