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Tue, 22 Sep 2020 12:44:08 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BDBE37881A; Tue, 22 Sep 2020 12:44:07 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id A708C922E2; Tue, 22 Sep 2020 12:44:06 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 08MCi5n8018824 for ; Tue, 22 Sep 2020 08:44:05 -0400 Received: by smtp.corp.redhat.com (Postfix) id 878D81001281; Tue, 22 Sep 2020 12:44:05 +0000 (UTC) Received: from madcap2.tricolour.ca (unknown [10.10.110.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4784F10027AB; Tue, 22 Sep 2020 12:43:51 +0000 (UTC) Date: Tue, 22 Sep 2020 08:43:49 -0400 From: Richard Guy Briggs To: Paul Moore Subject: Re: [[PATCH V4]] audit: trigger accompanying records when no rules present Message-ID: <20200922124349.GI822320@madcap2.tricolour.ca> References: <35f2b8c69b4b9abbc076dd55a6f0f52cf20abad7.1599687447.git.rgb@redhat.com> <20200921195655.GH822320@madcap2.tricolour.ca> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-loop: linux-audit@redhat.com Cc: Linux Security Module list , Linux-Audit Mailing List , LKML X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-audit-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline On 2020-09-21 19:31, Paul Moore wrote: > On Mon, Sep 21, 2020 at 3:57 PM Richard Guy Briggs wrote: > > On 2020-09-15 12:18, Paul Moore wrote: > > > On Thu, Sep 10, 2020 at 11:03 AM Richard Guy Briggs wrote: > > > > > > > > When there are no audit rules registered, mandatory records (config, > > > > etc.) are missing their accompanying records (syscall, proctitle, etc.). > > > > > > > > This is due to audit context dummy set on syscall entry based on absence > > > > of rules that signals that no other records are to be printed. > > > > > > > > Clear the dummy bit if any record is generated. > > > > > > > > The proctitle context and dummy checks are pointless since the > > > > proctitle record will not be printed if no syscall records are printed. > > > > > > > > The fds array is reset to -1 after the first syscall to indicate it > > > > isn't valid any more, but was never set to -1 when the context was > > > > allocated to indicate it wasn't yet valid. > > > > > > > > The audit_inode* functions can be called without going through > > > > getname_flags() or getname_kernel() that sets audit_names and cwd, so > > > > set the cwd if it has not already been done so due to audit_names being > > > > valid. > > > > > > > > The LSM dump_common_audit_data() LSM_AUDIT_DATA_NET:AF_UNIX case was > > > > missed with the ghak96 patch, so add that case here. > > > > > > > > Thanks to bauen1 for reporting LSM situations in > > > > which context->cwd is not valid, inadvertantly fixed by the ghak96 patch. > > > > > > > > Please see upstream github issue > > > > https://github.com/linux-audit/audit-kernel/issues/120 > > > > This is also related to upstream github issue > > > > https://github.com/linux-audit/audit-kernel/issues/96 > > > > > > > > Signed-off-by: Richard Guy Briggs > > > > --- > > > > Passes audit-testsuite. > > > > > > > > Chagelog: > > > > v4: > > > > - rebase on audit/next v5.9-rc1 > > > > - squash v2+v3fix > > > > - add pwd NULL check in audit_log_name() > > > > - resubmit after revert > > > > > > > > v3: > > > > - initialize fds[0] to -1 > > > > - init cwd for ghak96 LSM_AUDIT_DATA_NET:AF_UNIX case > > > > - init cwd for audit_inode{,_child} > > > > > > > > v2: > > > > - unconditionally clear dummy > > > > - create audit_clear_dummy accessor function > > > > - remove proctitle context and dummy checks > > > > > > > > kernel/audit.c | 1 + > > > > kernel/audit.h | 8 ++++++++ > > > > kernel/auditsc.c | 11 +++++++---- > > > > security/lsm_audit.c | 1 + > > > > 4 files changed, 17 insertions(+), 4 deletions(-) > > > > > > Comments below, but can you elaborate on if any testing was done > > > beyond the audit-testsuite? > > > > Yes, it was tested with audit-testsuite and bauen1's reproducer > > > > > > diff --git a/kernel/audit.h b/kernel/audit.h > > > > index 3b9c0945225a..abcfef58435b 100644 > > > > --- a/kernel/audit.h > > > > +++ b/kernel/audit.h > > > > @@ -290,6 +290,13 @@ extern int audit_signal_info_syscall(struct task_struct *t); > > > > extern void audit_filter_inodes(struct task_struct *tsk, > > > > struct audit_context *ctx); > > > > extern struct list_head *audit_killed_trees(void); > > > > + > > > > +static inline void audit_clear_dummy(struct audit_context *ctx) > > > > +{ > > > > + if (ctx) > > > > + ctx->dummy = 0; > > > > +} > > > > > > With the only caller being audit_log_start(), should this be moved to > > > kernel/audit.c? I'm just not sure this is something we would ever > > > need (or want) to call from elsewhere, thoughts? > > > > Yes, move it, or better yet just open code it. > > Sure. It might also help to put a one-liner comment in there about why. No problem. > > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > > > > index 8dba8f0983b5..9d2de93f40b3 100644 > > > > --- a/kernel/auditsc.c > > > > +++ b/kernel/auditsc.c > > > > @@ -1367,7 +1368,10 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n, > > > > /* name was specified as a relative path and the > > > > * directory component is the cwd > > > > */ > > > > - audit_log_d_path(ab, " name=", &context->pwd); > > > > + if (&context->pwd) > > > > > > Hmm, I don't think this is going to work the way you are intending; I > > > believe this will always evaluate to true regardless of the state of > > > context->pwd. If you look elsewhere in kernel/auditsc.c you will see > > > some examples of checking to see if context->pwd is valid (e.g. > > > _audit_getcwd() and audit_log_exit()). > > > > Sorry for the ctx->pwd.dentry/mnt brainfart, the compiler *did* > > complain. > > That begs the question: why did you submit the patch? I don't want to > dwell too much on this, but compilers are pretty smart these days, > it's best not to ignore their warnings unless you are *really* sure > you are right. I didn't ignore the compiler warning. I fixed it a bit too hastily, incorrectly, the first time. > > > > + audit_log_d_path(ab, " name=", &context->pwd); > > > > + else > > > > + audit_log_format(ab, " name=(null)"); > > > > break; > > > > default: > > > > /* log the name's directory component */... > > > > > > > @@ -2079,6 +2080,7 @@ void __audit_inode(struct filename *name, const struct dentry *dentry, > > > > } > > > > handle_path(dentry); > > > > audit_copy_inode(n, dentry, inode, flags & AUDIT_INODE_NOEVAL); > > > > + _audit_getcwd(context); > > > > } > > > > > > > > void __audit_file(const struct file *file) > > > > @@ -2197,6 +2199,7 @@ void __audit_inode_child(struct inode *parent, > > > > audit_copy_inode(found_child, dentry, inode, 0); > > > > else > > > > found_child->ino = AUDIT_INO_UNSET; > > > > + _audit_getcwd(context); > > > > } > > > > EXPORT_SYMBOL_GPL(__audit_inode_child); > > > > > > > > diff --git a/security/lsm_audit.c b/security/lsm_audit.c > > > > index 53d0d183db8f..e93077612246 100644 > > > > --- a/security/lsm_audit.c > > > > +++ b/security/lsm_audit.c > > > > @@ -369,6 +369,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, > > > > audit_log_untrustedstring(ab, p); > > > > else > > > > audit_log_n_hex(ab, p, len); > > > > + audit_getcwd(); > > > > break; > > > > } > > > > } > > > > > > I'm starting to wonder if audit is doing this wrong (it is audit after > > > all) ... why not just fetch the cwd in audit_log_exit() if there are > > > entries in the context->names_list? The only time we care about > > > logging the working dir is when we actually have PATH records, right? > > > My initial thinking is that we can simplify a lot of code if we just > > > add a audit_getcwd() call in audit_log_exit() if the > > > context->names_list is not empty. We should even be safe in the task > > > exit case as the fs info appears to get cleaned up *after* > > > audit_log_exit() is called. > > > > > Assuming we go this route, we can probably get rid of all the > > > audit_getcwd() calls outside of the audit code (e.g. the lsm_audit.c > > > code). I guess we would need to make sure things still behave the > > > same for chdir(2), getcwd(2), etc. but even if we have to insert one > > > or two audit_getcwd() calls in that case we should still come out on > > > top (although I suspect the necessary calls are already being made). > > > > Or just open code audit_getcwd() in audit_alloc_name() and kill all > > audit_getcwd() calls since it is audit_names that is populated as the > > result of a call to audit_alloc_name(). > > > > How does this look?: 4 files changed, 9 insertions(+), 33 deletions(-) > > It looks like a diffstat ... ? I'm guessing you meant to copy-n-paste > a diff here? No, it was a teaser of the patch I intended to send immediately afterwards, but life intervened and I have yet to send out the patch, which should be imminent. > paul moore - RGB -- Richard Guy Briggs Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635 -- Linux-audit mailing list Linux-audit@redhat.com https://www.redhat.com/mailman/listinfo/linux-audit