On Fri, Jul 7, 2023 at 12:54 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > On 7/6/2023 6:43 PM, Paul Moore wrote: > > 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? > > > > I'm also going to assume that Casey is okay with the Smack portion of > > this patchset? It looks fine to me, and considering his ACK on the > > other Smack patch in this patchset I'm assuming he is okay with this > > one as well ... ? > > Yes, please feel free to add my Acked-by as needed. Done. Thanks Casey. -- paul-moore.com
