On Fri, Jul 7, 2023 at 2:49 AM Roberto Sassu <roberto.sassu@xxxxxxxxxx> wrote: > > From: Paul Moore [mailto:paul@xxxxxxxxxxxxxx] > > Sent: Friday, July 7, 2023 3:44 AM > > On Jun 10, 2023 Roberto Sassu <roberto.sassu@xxxxxxxxxxxxxxx> wrote: > > > > > > Currently, the LSM infrastructure supports only one LSM providing an xattr > > > and EVM calculating the HMAC on that xattr, plus other inode metadata. > > > > > > Allow all LSMs to provide one or multiple xattrs, by extending the security > > > blob reservation mechanism. Introduce the new lbs_xattr_count field of the > > > lsm_blob_sizes structure, so that each LSM can specify how many xattrs it > > > needs, and the LSM infrastructure knows how many xattr slots it should > > > allocate. > > > > > > Modify the inode_init_security hook definition, by passing the full > > > xattr array allocated in security_inode_init_security(), and the current > > > number of xattr slots in that array filled by LSMs. The first parameter > > > would allow EVM to access and calculate the HMAC on xattrs supplied by > > > other LSMs, the second to not leave gaps in the xattr array, when an LSM > > > requested but did not provide xattrs (e.g. if it is not initialized). > > > > > > Introduce lsm_get_xattr_slot(), which LSMs can call as many times as the > > > number specified in the lbs_xattr_count field of the lsm_blob_sizes > > > structure. During each call, lsm_get_xattr_slot() increments the number of > > > filled xattrs, so that at the next invocation it returns the next xattr > > > slot to fill. > > > > > > Cleanup security_inode_init_security(). Unify the !initxattrs and > > > initxattrs case by simply not allocating the new_xattrs array in the > > > former. Update the documentation to reflect the changes, and fix the > > > description of the xattr name, as it is not allocated anymore. > > > > > > Adapt both SELinux and Smack to use the new definition of the > > > inode_init_security hook, and to call lsm_get_xattr_slot() to obtain and > > > fill the reserved slots in the xattr array. > > > > > > Move the xattr->name assignment after the xattr->value one, so that it is > > > done only in case of successful memory allocation. > > > > > > Finally, change the default return value of the inode_init_security hook > > > from zero to -EOPNOTSUPP, so that BPF LSM correctly follows the hook > > > conventions. > > > > > > Reported-by: Nicolas Bouchinet <nicolas.bouchinet@xxxxxxxxxxx> > > > Link: https://lore.kernel.org/linux-integrity/Y1FTSIo+1x+4X0LS@archlinux/ > > > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > > > --- > > > include/linux/lsm_hook_defs.h | 6 +-- > > > include/linux/lsm_hooks.h | 20 ++++++++++ > > > security/security.c | 71 +++++++++++++++++++++++------------ > > > security/selinux/hooks.c | 17 +++++---- > > > security/smack/smack_lsm.c | 25 ++++++------ > > > 5 files changed, 92 insertions(+), 47 deletions(-) > > > > Two *very* small suggestions below, but I can make those during the > > merge if you are okay with that Roberto? > > Hi Paul > > yes, sure, I'm ok with them. Please make them during the merge. Great, I'll queue this up for merging once the merge window closes. I'll send confirmation once it's done but just a heads-up that things might be a little delayed next week. -- paul-moore.com
