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| author | Matthew Garrett <mjg59@google.com> | 2018-05-15 10:38:26 -0700 |
|---|---|---|
| committer | Mimi Zohar <zohar@linux.vnet.ibm.com> | 2018-05-18 15:34:45 -0400 |
| commit | fa516b66a1bfce1d72f1620c54bdfebc493000d1 (patch) | |
| tree | 26b2887ece19ada7ec0f756a9cc7720cee4d1291 /Documentation | |
| parent | 21af76631476030709f85f48e20bb9429a912b6f (diff) | |
| download | linux-0-day-fa516b66a1bfce1d72f1620c54bdfebc493000d1.tar.gz linux-0-day-fa516b66a1bfce1d72f1620c54bdfebc493000d1.tar.xz | |
EVM: Allow runtime modification of the set of verified xattrs
Sites may wish to provide additional metadata alongside files in order
to make more fine-grained security decisions[1]. The security of this is
enhanced if this metadata is protected, something that EVM makes
possible. However, the kernel cannot know about the set of extended
attributes that local admins may wish to protect, and hardcoding this
policy in the kernel makes it difficult to change over time and less
convenient for distributions to enable.
This patch adds a new /sys/kernel/security/integrity/evm/evm_xattrs node,
which can be read to obtain the current set of EVM-protected extended
attributes or written to in order to add new entries. Extending this list
will not change the validity of any existing signatures provided that the
file in question does not have any of the additional extended attributes -
missing xattrs are skipped when calculating the EVM hash.
[1] For instance, a package manager could install information about the
package uploader in an additional extended attribute. Local LSM policy
could then be associated with that extended attribute in order to
restrict the privileges available to packages from less trusted
uploaders.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/evm | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm index d12cb2eae9ee6..201d10319fa18 100644 --- a/Documentation/ABI/testing/evm +++ b/Documentation/ABI/testing/evm @@ -57,3 +57,16 @@ Description: 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 posessing 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. |