On Jan 15, 2024 Roberto Sassu <roberto.sassu@xxxxxxxxxxxxxxx> wrote: > > 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@xxxxxxxxxx> > Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx> > --- > include/linux/evm.h | 8 +-- > security/integrity/evm/Kconfig | 1 + > security/integrity/evm/evm.h | 19 +++++++ > security/integrity/evm/evm_crypto.c | 4 +- > security/integrity/evm/evm_main.c | 76 ++++++++++++++++++++------- > security/integrity/ima/ima_appraise.c | 2 +- > security/integrity/integrity.h | 1 - > security/security.c | 4 +- > 8 files changed, 83 insertions(+), 32 deletions(-) Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx> -- paul-moore.com
