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| author | Matthew Garrett <mjg59@google.com> | 2017-11-07 07:18:35 -0800 |
|---|---|---|
| committer | Mimi Zohar <zohar@linux.vnet.ibm.com> | 2017-12-11 14:27:31 -0500 |
| commit | ae1ba1676b88e6c62368a433c7e2d0417e9879fd (patch) | |
| tree | bcbb1a5cba2e439031db519e846f89a91a8b8b2d /security/integrity/evm/evm.h | |
| parent | b7e27bc1d42e8e0cc58b602b529c25cd0071b336 (diff) | |
| download | linux-ae1ba1676b88e6c62368a433c7e2d0417e9879fd.tar.gz linux-ae1ba1676b88e6c62368a433c7e2d0417e9879fd.tar.bz2 linux-ae1ba1676b88e6c62368a433c7e2d0417e9879fd.zip | |
EVM: Allow userland to permit modification of EVM-protected metadata
When EVM is enabled it forbids modification of metadata protected by
EVM unless there is already a valid EVM signature. If any modification
is made, the kernel will then generate a new EVM HMAC. However, this
does not map well on use cases which use only asymmetric EVM signatures,
as in this scenario the kernel is unable to generate new signatures.
This patch extends the /sys/kernel/security/evm interface to allow
userland to request that modification of these xattrs be permitted. This
is only permitted if no keys have already been loaded. In this
configuration, modifying the metadata will invalidate the EVM appraisal
on the file in question. This allows packaging systems to write out new
files, set the relevant extended attributes and then move them into
place.
There's also some refactoring of the use of evm_initialized in order to
avoid heading down codepaths that assume there's a key available.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Diffstat (limited to 'security/integrity/evm/evm.h')
| -rw-r--r-- | security/integrity/evm/evm.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h index 241aca315b0c..3d05250e8313 100644 --- a/security/integrity/evm/evm.h +++ b/security/integrity/evm/evm.h @@ -23,9 +23,12 @@ #define EVM_INIT_HMAC 0x0001 #define EVM_INIT_X509 0x0002 -#define EVM_SETUP 0x80000000 /* userland has signaled key load */ +#define EVM_ALLOW_METADATA_WRITES 0x0004 +#define EVM_SETUP_COMPLETE 0x80000000 /* userland has signaled key load */ -#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP) +#define EVM_KEY_MASK (EVM_INIT_HMAC | EVM_INIT_X509) +#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE | \ + EVM_ALLOW_METADATA_WRITES) extern int evm_initialized; extern char *evm_hmac; |