On Tue, 2023-12-26 at 12:14 -0800, Casey Schaufler wrote: > On 12/26/2023 10:14 AM, Mimi Zohar wrote: > > On Thu, 2023-12-14 at 18:08 +0100, Roberto Sassu wrote: > >> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > >> > >> Move hardcoded IMA function calls (not appraisal-specific functions) from > >> various places in the kernel to the LSM infrastructure, by introducing a > >> new LSM named 'ima' (at the end of the LSM list and always enabled like > >> 'integrity'). > >> > >> Having IMA before EVM in the Makefile is sufficient to preserve the > >> relative order of the new 'ima' LSM in respect to the upcoming 'evm' LSM, > >> and thus the order of IMA and EVM function calls as when they were > >> hardcoded. > >> > >> Make moved functions as static (except ima_post_key_create_or_update(), > >> which is not in ima_main.c), and register them as implementation of the > >> respective hooks in the new function init_ima_lsm(). > >> > >> A slight difference is that IMA and EVM functions registered for the > >> inode_post_setattr, inode_post_removexattr, path_post_mknod, > >> inode_post_create_tmpfile, inode_post_set_acl and inode_post_remove_acl > >> won't be executed for private inodes. Since those inodes are supposed to be > >> fs-internal, they should not be of interest of IMA or EVM. The S_PRIVATE > >> flag is used for anonymous inodes, hugetlbfs, reiserfs xattrs, XFS scrub > >> and kernel-internal tmpfs files. > >> > >> Conditionally register ima_post_path_mknod() if CONFIG_SECURITY_PATH is > >> enabled, otherwise the path_post_mknod hook won't be available. > > Up to this point, enabling CONFIG_SECURITY_PATH was not required. By > > making it conditional on CONFIG_SECURITY_PATH, anyone enabling IMA will > > also need to enable CONFIG_SECURITY_PATH. Without it, new files will > > not be tagged as a "new" file. > > > > Casey, Paul, how common is it today not to enable CONFIG_SECURITY_PATH? > > Will enabling it just for IMA be a problem? > > Landlock, AppArmor and TOMOYO require it. Fedora enables Landlock and Ubuntu > enables AppArmor. I expect that, except for "minimal" distributions, you > won't get any push back. If a distribution is striving for minimal, it's not > going to use IMA. > > It makes me wonder if eliminating CONFIG_SECURITY_PATH might not be a > rational alternative. Embedded systems were the first to use IMA for file signature verification, not distros. Could they have enabled SELinux, lockdown, and IMA? Mimi
