Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755959AbdGLAaR (ORCPT ); Tue, 11 Jul 2017 20:30:17 -0400 Received: from mail-qt0-f195.google.com ([209.85.216.195]:34312 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753701AbdGLAaN (ORCPT ); Tue, 11 Jul 2017 20:30:13 -0400 Message-ID: <1499819409.26839.1.camel@poochiereds.net> Subject: Re: [PATCH v2] integrity: track mtime in addition to i_version for assessment From: jlayton@poochiereds.net To: "J. Bruce Fields" , Jeff Layton Cc: Mimi Zohar , "Serge E. Hallyn" , Dmitry Kasatkin , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org Date: Tue, 11 Jul 2017 20:30:09 -0400 In-Reply-To: <20170711161324.GA31196@fieldses.org> References: <20170707140530.30452-1-jlayton@kernel.org> <20170711161324.GA31196@fieldses.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.24.3 (3.24.3-1.fc26) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4889 Lines: 150 On Tue, 2017-07-11 at 12:13 -0400, J. Bruce Fields wrote: > On Fri, Jul 07, 2017 at 10:05:30AM -0400, Jeff Layton wrote: > > From: Jeff Layton > > > > The IMA assessment code tries to use the i_version counter to > > detect > > when changes to a file have occurred. Many filesystems don't > > increment > > it properly (or at all) so detecting changes with that is not > > always > > reliable. > > > > That check should be gated on IS_I_VERSION, as you can't rely on > > the > > i_version field changing unless that returns true. > > > > Have the code also track and check the mtime for the file. If the > > IS_I_VERSION returns false, then use it to detect whether the > > file's > > contents might have changed. > > Do they care about attribute changes? It's still better than > nothing, I > suppose. > Evidently not, which is why I switched from using ctime to mtime in this patch. > I also wonder whether they should be mixing in ctime as I plan to for > nfsd--the difference is whether they use it to check changes across > reboots. > I don't think they record the i_version across reboots, so I don't think there's any need. > --b. > > > > > Signed-off-by: Jeff Layton > > --- > > security/integrity/ima/ima_api.c | 4 +++- > > security/integrity/ima/ima_main.c | 32 ++++++++++++++++++++++++--- > > ----- > > security/integrity/integrity.h | 1 + > > 3 files changed, 28 insertions(+), 9 deletions(-) > > > > v2: switch to storing/checking mtime instead of ctime > > > > diff --git a/security/integrity/ima/ima_api.c > > b/security/integrity/ima/ima_api.c > > index c2edba8de35e..b8d746bbc43d 100644 > > --- a/security/integrity/ima/ima_api.c > > +++ b/security/integrity/ima/ima_api.c > > @@ -205,7 +205,8 @@ int ima_collect_measurement(struct > > integrity_iint_cache *iint, > > } hash; > > > > if (!(iint->flags & IMA_COLLECTED)) { > > - u64 i_version = file_inode(file)->i_version; > > + u64 i_version = inode->i_version; > > + struct timespec i_mtime = inode->i_mtime; > > > > if (file->f_flags & O_DIRECT) { > > audit_cause = "failed(directio)"; > > @@ -225,6 +226,7 @@ int ima_collect_measurement(struct > > integrity_iint_cache *iint, > > iint->ima_hash = tmpbuf; > > memcpy(iint->ima_hash, &hash, > > length); > > iint->version = i_version; > > + iint->mtime = i_mtime; > > iint->flags |= IMA_COLLECTED; > > } else > > result = -ENOMEM; > > diff --git a/security/integrity/ima/ima_main.c > > b/security/integrity/ima/ima_main.c > > index 2aebb7984437..8d12ef2d3ba2 100644 > > --- a/security/integrity/ima/ima_main.c > > +++ b/security/integrity/ima/ima_main.c > > @@ -113,6 +113,25 @@ static void ima_rdwr_violation_check(struct > > file *file, > > "invalid_pcr", "open_writers"); > > } > > > > +static bool ima_should_update_iint(struct integrity_iint_cache > > *iint, > > + struct inode *inode) > > +{ > > + if (atomic_read(&inode->i_writecount) != 1) > > + return false; > > + if (iint->flags & IMA_NEW_FILE) > > + return true; > > + if (IS_I_VERSION(inode)) { > > + if (iint->version != inode->i_version) > > + return true; > > + } else { > > + if (iint->mtime.tv_sec != inode->i_mtime.tv_sec) > > + return true; > > + if (iint->mtime.tv_nsec != inode->i_mtime.tv_nsec) > > + return true; > > + } > > + return false; > > +} > > + > > static void ima_check_last_writer(struct integrity_iint_cache > > *iint, > > struct inode *inode, struct file > > *file) > > { > > @@ -122,14 +141,11 @@ static void ima_check_last_writer(struct > > integrity_iint_cache *iint, > > return; > > > > inode_lock(inode); > > - if (atomic_read(&inode->i_writecount) == 1) { > > - if ((iint->version != inode->i_version) || > > - (iint->flags & IMA_NEW_FILE)) { > > - iint->flags &= ~(IMA_DONE_MASK | > > IMA_NEW_FILE); > > - iint->measured_pcrs = 0; > > - if (iint->flags & IMA_APPRAISE) > > - ima_update_xattr(iint, file); > > - } > > + if (ima_should_update_iint(iint, inode)) { > > + iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE); > > + iint->measured_pcrs = 0; > > + if (iint->flags & IMA_APPRAISE) > > + ima_update_xattr(iint, file); > > } > > inode_unlock(inode); > > } > > diff --git a/security/integrity/integrity.h > > b/security/integrity/integrity.h > > index a53e7e4ab06c..61fffa7583bf 100644 > > --- a/security/integrity/integrity.h > > +++ b/security/integrity/integrity.h > > @@ -102,6 +102,7 @@ struct integrity_iint_cache { > > struct rb_node rb_node; /* rooted in > > integrity_iint_tree */ > > struct inode *inode; /* back pointer to inode in > > question */ > > u64 version; /* track inode changes */ > > + struct timespec mtime; /* track inode changes */ > > unsigned long flags; > > unsigned long measured_pcrs; > > enum integrity_status ima_file_status:4; > > -- > > 2.13.0