75a323e604
Define a new structure for EVM-specific metadata, called evm_iint_cache, and embed it in the inode security blob. Introduce evm_iint_inode() to retrieve metadata, and register evm_inode_alloc_security() for the inode_alloc_security LSM hook, to initialize the structure (before splitting metadata, this task was done by iint_init_always()). Keep the non-NULL checks after calling evm_iint_inode() except in evm_inode_alloc_security(), to take into account inodes for which security_inode_alloc() was not called. When using shared metadata, obtaining a NULL pointer from integrity_iint_find() meant that the file wasn't in the IMA policy. Now, because IMA and EVM use disjoint metadata, the EVM status has to be stored for every inode regardless of the IMA policy. Given that from now on EVM relies on its own metadata, remove the iint parameter from evm_verifyxattr(). Also, directly retrieve the iint in evm_verify_hmac(), called by both evm_verifyxattr() and evm_verify_current_integrity(), since now there is no performance penalty in retrieving EVM metadata (constant time). Replicate the management of the IMA_NEW_FILE flag, by introducing evm_post_path_mknod() and evm_file_release() to respectively set and clear the newly introduced flag EVM_NEW_FILE, at the same time IMA does. Like for IMA, select CONFIG_SECURITY_PATH when EVM is enabled, to ensure that files are marked as new. Unlike ima_post_path_mknod(), evm_post_path_mknod() cannot check if a file must be appraised. Thus, it marks all affected files. Also, it does not clear EVM_NEW_FILE depending on i_version, but that is not a problem because IMA_NEW_FILE is always cleared when set in ima_check_last_writer(). Move the EVM-specific flag EVM_IMMUTABLE_DIGSIG to security/integrity/evm/evm.h, since that definition is now unnecessary in the common integrity layer. Finally, switch to the LSM reservation mechanism for the EVM xattr, and consequently decrement by one the number of xattrs to allocate in security_inode_init_security(). Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Acked-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
2.3 KiB
SPDX-License-Identifier: GPL-2.0-only
config EVM bool "EVM support" select KEYS select ENCRYPTED_KEYS select CRYPTO_HMAC select CRYPTO_SHA1 select CRYPTO_HASH_INFO select SECURITY_PATH default n help EVM protects a file's security extended attributes against integrity attacks.
If you are unsure how to answer this question, answer N.
config EVM_ATTR_FSUUID bool "FSUUID (version 2)" default y depends on EVM help Include filesystem UUID for HMAC calculation.
Default value is 'selected', which is former version 2.
if 'not selected', it is former version 1
WARNING: changing the HMAC calculation method or adding
additional info to the calculation, requires existing EVM
labeled file systems to be relabeled.
config EVM_EXTRA_SMACK_XATTRS bool "Additional SMACK xattrs" depends on EVM && SECURITY_SMACK default n help Include additional SMACK xattrs for HMAC calculation.
In addition to the original security xattrs (eg. security.selinux,
security.SMACK64, security.capability, and security.ima) included
in the HMAC calculation, enabling this option includes newly defined
Smack xattrs: security.SMACK64EXEC, security.SMACK64TRANSMUTE and
security.SMACK64MMAP.
WARNING: changing the HMAC calculation method or adding
additional info to the calculation, requires existing EVM
labeled file systems to be relabeled.
config EVM_ADD_XATTRS bool "Add additional EVM extended attributes at runtime" depends on EVM default n help Allow userland to provide additional xattrs for HMAC calculation.
When this option is enabled, root can add additional xattrs to the
list used by EVM by writing them into
/sys/kernel/security/integrity/evm/evm_xattrs.
config EVM_LOAD_X509 bool "Load an X509 certificate onto the '.evm' trusted keyring" depends on EVM && INTEGRITY_TRUSTED_KEYRING default n help Load an X509 certificate onto the '.evm' trusted keyring.
This option enables X509 certificate loading from the kernel
onto the '.evm' trusted keyring. A public key can be used to
verify EVM integrity starting from the 'init' process. The
key must have digitalSignature usage set.
config EVM_X509_PATH string "EVM X509 certificate path" depends on EVM_LOAD_X509 default "/etc/keys/x509_evm.der" help This option defines X509 certificate path.