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Message-ID: <3bcc924ed59ecdc5fda5ab8aceeed9450a54c829.camel@linux.ibm.com> Date: Wed, 27 Dec 2023 14:52:40 -0500 From: Mimi Zohar <zohar@...ux.ibm.com> To: Casey Schaufler <casey@...aufler-ca.com>, Roberto Sassu <roberto.sassu@...weicloud.com>, viro@...iv.linux.org.uk, brauner@...nel.org, chuck.lever@...cle.com, jlayton@...nel.org, neilb@...e.de, kolga@...app.com, Dai.Ngo@...cle.com, tom@...pey.com, paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com, dmitry.kasatkin@...il.com, dhowells@...hat.com, jarkko@...nel.org, stephen.smalley.work@...il.com, eparis@...isplace.org, shuah@...nel.org, mic@...ikod.net Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org, linux-security-module@...r.kernel.org, linux-integrity@...r.kernel.org, keyrings@...r.kernel.org, selinux@...r.kernel.org, linux-kselftest@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com> Subject: Re: [PATCH v8 19/24] ima: Move to LSM infrastructure 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@...wei.com> > >> > >> 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
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